Adding upstream version 3.0.36.upstream/3.0.36upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

147 files changed, 40760 insertions, 0 deletions

diff --git a/src/prompt_toolkit/__init__.py b/src/prompt_toolkit/__init__.py
new file mode 100644
index 0000000..26e03a7
--- /dev/null
+++ b/src/prompt_toolkit/__init__.py
@@ -0,0 +1,40 @@
+"""
+prompt_toolkit
+==============
+
+Author: Jonathan Slenders
+
+Description: prompt_toolkit is a Library for building powerful interactive
+             command lines in Python.  It can be a replacement for GNU
+             Readline, but it can be much more than that.
+
+See the examples directory to learn about the usage.
+
+Probably, to get started, you might also want to have a look at
+`prompt_toolkit.shortcuts.prompt`.
+"""
+from .application import Application
+from .formatted_text import ANSI, HTML
+from .shortcuts import PromptSession, print_formatted_text, prompt
+
+# Don't forget to update in `docs/conf.py`!
+__version__ = "3.0.36"
+
+# Version tuple.
+VERSION = tuple(__version__.split("."))
+
+
+__all__ = [
+    # Application.
+    "Application",
+    # Shortcuts.
+    "prompt",
+    "PromptSession",
+    "print_formatted_text",
+    # Formatted text.
+    "HTML",
+    "ANSI",
+    # Version info.
+    "__version__",
+    "VERSION",
+]
diff --git a/src/prompt_toolkit/application/__init__.py b/src/prompt_toolkit/application/__init__.py
new file mode 100644
index 0000000..dc61ca7
--- /dev/null
+++ b/src/prompt_toolkit/application/__init__.py
@@ -0,0 +1,30 @@
+from .application import Application
+from .current import (
+    AppSession,
+    create_app_session,
+    create_app_session_from_tty,
+    get_app,
+    get_app_or_none,
+    get_app_session,
+    set_app,
+)
+from .dummy import DummyApplication
+from .run_in_terminal import in_terminal, run_in_terminal
+
+__all__ = [
+    # Application.
+    "Application",
+    # Current.
+    "AppSession",
+    "get_app_session",
+    "create_app_session",
+    "create_app_session_from_tty",
+    "get_app",
+    "get_app_or_none",
+    "set_app",
+    # Dummy.
+    "DummyApplication",
+    # Run_in_terminal
+    "in_terminal",
+    "run_in_terminal",
+]
diff --git a/src/prompt_toolkit/application/application.py b/src/prompt_toolkit/application/application.py
new file mode 100644
index 0000000..0915a9e
--- /dev/null
+++ b/src/prompt_toolkit/application/application.py
@@ -0,0 +1,1521 @@
+import asyncio
+import os
+import re
+import signal
+import sys
+import threading
+import time
+from asyncio import (
+    AbstractEventLoop,
+    Future,
+    Task,
+    ensure_future,
+    new_event_loop,
+    set_event_loop,
+    sleep,
+)
+from contextlib import ExitStack, contextmanager
+from subprocess import Popen
+from traceback import format_tb
+from typing import (
+    Any,
+    Awaitable,
+    Callable,
+    Coroutine,
+    Dict,
+    FrozenSet,
+    Generator,
+    Generic,
+    Hashable,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Set,
+    Tuple,
+    Type,
+    TypeVar,
+    Union,
+    cast,
+    overload,
+)
+
+from prompt_toolkit.buffer import Buffer
+from prompt_toolkit.cache import SimpleCache
+from prompt_toolkit.clipboard import Clipboard, InMemoryClipboard
+from prompt_toolkit.cursor_shapes import AnyCursorShapeConfig, to_cursor_shape_config
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.enums import EditingMode
+from prompt_toolkit.eventloop import (
+    get_traceback_from_context,
+    run_in_executor_with_context,
+)
+from prompt_toolkit.eventloop.utils import call_soon_threadsafe, get_event_loop
+from prompt_toolkit.filters import Condition, Filter, FilterOrBool, to_filter
+from prompt_toolkit.formatted_text import AnyFormattedText
+from prompt_toolkit.input.base import Input
+from prompt_toolkit.input.typeahead import get_typeahead, store_typeahead
+from prompt_toolkit.key_binding.bindings.page_navigation import (
+    load_page_navigation_bindings,
+)
+from prompt_toolkit.key_binding.defaults import load_key_bindings
+from prompt_toolkit.key_binding.emacs_state import EmacsState
+from prompt_toolkit.key_binding.key_bindings import (
+    Binding,
+    ConditionalKeyBindings,
+    GlobalOnlyKeyBindings,
+    KeyBindings,
+    KeyBindingsBase,
+    KeysTuple,
+    merge_key_bindings,
+)
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent, KeyProcessor
+from prompt_toolkit.key_binding.vi_state import ViState
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.layout.containers import Container, Window
+from prompt_toolkit.layout.controls import BufferControl, UIControl
+from prompt_toolkit.layout.dummy import create_dummy_layout
+from prompt_toolkit.layout.layout import Layout, walk
+from prompt_toolkit.output import ColorDepth, Output
+from prompt_toolkit.renderer import Renderer, print_formatted_text
+from prompt_toolkit.search import SearchState
+from prompt_toolkit.styles import (
+    BaseStyle,
+    DummyStyle,
+    DummyStyleTransformation,
+    DynamicStyle,
+    StyleTransformation,
+    default_pygments_style,
+    default_ui_style,
+    merge_styles,
+)
+from prompt_toolkit.utils import Event, in_main_thread
+
+from .current import get_app_session, set_app
+from .run_in_terminal import in_terminal, run_in_terminal
+
+try:
+    import contextvars
+except ImportError:
+    import prompt_toolkit.eventloop.dummy_contextvars as contextvars  # type: ignore
+
+
+__all__ = [
+    "Application",
+]
+
+
+E = KeyPressEvent
+_AppResult = TypeVar("_AppResult")
+ApplicationEventHandler = Callable[["Application[_AppResult]"], None]
+
+_SIGWINCH = getattr(signal, "SIGWINCH", None)
+_SIGTSTP = getattr(signal, "SIGTSTP", None)
+
+
+class Application(Generic[_AppResult]):
+    """
+    The main Application class!
+    This glues everything together.
+
+    :param layout: A :class:`~prompt_toolkit.layout.Layout` instance.
+    :param key_bindings:
+        :class:`~prompt_toolkit.key_binding.KeyBindingsBase` instance for
+        the key bindings.
+    :param clipboard: :class:`~prompt_toolkit.clipboard.Clipboard` to use.
+    :param full_screen: When True, run the application on the alternate screen buffer.
+    :param color_depth: Any :class:`~.ColorDepth` value, a callable that
+        returns a :class:`~.ColorDepth` or `None` for default.
+    :param erase_when_done: (bool) Clear the application output when it finishes.
+    :param reverse_vi_search_direction: Normally, in Vi mode, a '/' searches
+        forward and a '?' searches backward. In Readline mode, this is usually
+        reversed.
+    :param min_redraw_interval: Number of seconds to wait between redraws. Use
+        this for applications where `invalidate` is called a lot. This could cause
+        a lot of terminal output, which some terminals are not able to process.
+
+        `None` means that every `invalidate` will be scheduled right away
+        (which is usually fine).
+
+        When one `invalidate` is called, but a scheduled redraw of a previous
+        `invalidate` call has not been executed yet, nothing will happen in any
+        case.
+
+    :param max_render_postpone_time: When there is high CPU (a lot of other
+        scheduled calls), postpone the rendering max x seconds.  '0' means:
+        don't postpone. '.5' means: try to draw at least twice a second.
+
+    :param refresh_interval: Automatically invalidate the UI every so many
+        seconds. When `None` (the default), only invalidate when `invalidate`
+        has been called.
+
+    :param terminal_size_polling_interval: Poll the terminal size every so many
+        seconds. Useful if the applications runs in a thread other then then
+        main thread where SIGWINCH can't be handled, or on Windows.
+
+    Filters:
+
+    :param mouse_support: (:class:`~prompt_toolkit.filters.Filter` or
+        boolean). When True, enable mouse support.
+    :param paste_mode: :class:`~prompt_toolkit.filters.Filter` or boolean.
+    :param editing_mode: :class:`~prompt_toolkit.enums.EditingMode`.
+
+    :param enable_page_navigation_bindings: When `True`, enable the page
+        navigation key bindings. These include both Emacs and Vi bindings like
+        page-up, page-down and so on to scroll through pages. Mostly useful for
+        creating an editor or other full screen applications. Probably, you
+        don't want this for the implementation of a REPL. By default, this is
+        enabled if `full_screen` is set.
+
+    Callbacks (all of these should accept an
+    :class:`~prompt_toolkit.application.Application` object as input.)
+
+    :param on_reset: Called during reset.
+    :param on_invalidate: Called when the UI has been invalidated.
+    :param before_render: Called right before rendering.
+    :param after_render: Called right after rendering.
+
+    I/O:
+    (Note that the preferred way to change the input/output is by creating an
+    `AppSession` with the required input/output objects. If you need multiple
+    applications running at the same time, you have to create a separate
+    `AppSession` using a `with create_app_session():` block.
+
+    :param input: :class:`~prompt_toolkit.input.Input` instance.
+    :param output: :class:`~prompt_toolkit.output.Output` instance. (Probably
+                   Vt100_Output or Win32Output.)
+
+    Usage:
+
+        app = Application(...)
+        app.run()
+
+        # Or
+        await app.run_async()
+    """
+
+    def __init__(
+        self,
+        layout: Optional[Layout] = None,
+        style: Optional[BaseStyle] = None,
+        include_default_pygments_style: FilterOrBool = True,
+        style_transformation: Optional[StyleTransformation] = None,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        clipboard: Optional[Clipboard] = None,
+        full_screen: bool = False,
+        color_depth: Union[
+            ColorDepth, Callable[[], Union[ColorDepth, None]], None
+        ] = None,
+        mouse_support: FilterOrBool = False,
+        enable_page_navigation_bindings: Optional[
+            FilterOrBool
+        ] = None,  # Can be None, True or False.
+        paste_mode: FilterOrBool = False,
+        editing_mode: EditingMode = EditingMode.EMACS,
+        erase_when_done: bool = False,
+        reverse_vi_search_direction: FilterOrBool = False,
+        min_redraw_interval: Union[float, int, None] = None,
+        max_render_postpone_time: Union[float, int, None] = 0.01,
+        refresh_interval: Optional[float] = None,
+        terminal_size_polling_interval: Optional[float] = 0.5,
+        cursor: AnyCursorShapeConfig = None,
+        on_reset: Optional["ApplicationEventHandler[_AppResult]"] = None,
+        on_invalidate: Optional["ApplicationEventHandler[_AppResult]"] = None,
+        before_render: Optional["ApplicationEventHandler[_AppResult]"] = None,
+        after_render: Optional["ApplicationEventHandler[_AppResult]"] = None,
+        # I/O.
+        input: Optional[Input] = None,
+        output: Optional[Output] = None,
+    ) -> None:
+
+        # If `enable_page_navigation_bindings` is not specified, enable it in
+        # case of full screen applications only. This can be overridden by the user.
+        if enable_page_navigation_bindings is None:
+            enable_page_navigation_bindings = Condition(lambda: self.full_screen)
+
+        paste_mode = to_filter(paste_mode)
+        mouse_support = to_filter(mouse_support)
+        reverse_vi_search_direction = to_filter(reverse_vi_search_direction)
+        enable_page_navigation_bindings = to_filter(enable_page_navigation_bindings)
+        include_default_pygments_style = to_filter(include_default_pygments_style)
+
+        if layout is None:
+            layout = create_dummy_layout()
+
+        if style_transformation is None:
+            style_transformation = DummyStyleTransformation()
+
+        self.style = style
+        self.style_transformation = style_transformation
+
+        # Key bindings.
+        self.key_bindings = key_bindings
+        self._default_bindings = load_key_bindings()
+        self._page_navigation_bindings = load_page_navigation_bindings()
+
+        self.layout = layout
+        self.clipboard = clipboard or InMemoryClipboard()
+        self.full_screen: bool = full_screen
+        self._color_depth = color_depth
+        self.mouse_support = mouse_support
+
+        self.paste_mode = paste_mode
+        self.editing_mode = editing_mode
+        self.erase_when_done = erase_when_done
+        self.reverse_vi_search_direction = reverse_vi_search_direction
+        self.enable_page_navigation_bindings = enable_page_navigation_bindings
+        self.min_redraw_interval = min_redraw_interval
+        self.max_render_postpone_time = max_render_postpone_time
+        self.refresh_interval = refresh_interval
+        self.terminal_size_polling_interval = terminal_size_polling_interval
+
+        self.cursor = to_cursor_shape_config(cursor)
+
+        # Events.
+        self.on_invalidate = Event(self, on_invalidate)
+        self.on_reset = Event(self, on_reset)
+        self.before_render = Event(self, before_render)
+        self.after_render = Event(self, after_render)
+
+        # I/O.
+        session = get_app_session()
+        self.output = output or session.output
+        self.input = input or session.input
+
+        # List of 'extra' functions to execute before a Application.run.
+        self.pre_run_callables: List[Callable[[], None]] = []
+
+        self._is_running = False
+        self.future: Optional[Future[_AppResult]] = None
+        self.loop: Optional[AbstractEventLoop] = None
+        self.context: Optional[contextvars.Context] = None
+
+        #: Quoted insert. This flag is set if we go into quoted insert mode.
+        self.quoted_insert = False
+
+        #: Vi state. (For Vi key bindings.)
+        self.vi_state = ViState()
+        self.emacs_state = EmacsState()
+
+        #: When to flush the input (For flushing escape keys.) This is important
+        #: on terminals that use vt100 input. We can't distinguish the escape
+        #: key from for instance the left-arrow key, if we don't know what follows
+        #: after "\x1b". This little timer will consider "\x1b" to be escape if
+        #: nothing did follow in this time span.
+        #: This seems to work like the `ttimeoutlen` option in Vim.
+        self.ttimeoutlen = 0.5  # Seconds.
+
+        #: Like Vim's `timeoutlen` option. This can be `None` or a float.  For
+        #: instance, suppose that we have a key binding AB and a second key
+        #: binding A. If the uses presses A and then waits, we don't handle
+        #: this binding yet (unless it was marked 'eager'), because we don't
+        #: know what will follow. This timeout is the maximum amount of time
+        #: that we wait until we call the handlers anyway. Pass `None` to
+        #: disable this timeout.
+        self.timeoutlen = 1.0
+
+        #: The `Renderer` instance.
+        # Make sure that the same stdout is used, when a custom renderer has been passed.
+        self._merged_style = self._create_merged_style(include_default_pygments_style)
+
+        self.renderer = Renderer(
+            self._merged_style,
+            self.output,
+            full_screen=full_screen,
+            mouse_support=mouse_support,
+            cpr_not_supported_callback=self.cpr_not_supported_callback,
+        )
+
+        #: Render counter. This one is increased every time the UI is rendered.
+        #: It can be used as a key for caching certain information during one
+        #: rendering.
+        self.render_counter = 0
+
+        # Invalidate flag. When 'True', a repaint has been scheduled.
+        self._invalidated = False
+        self._invalidate_events: List[
+            Event[object]
+        ] = []  # Collection of 'invalidate' Event objects.
+        self._last_redraw_time = 0.0  # Unix timestamp of last redraw. Used when
+        # `min_redraw_interval` is given.
+
+        #: The `InputProcessor` instance.
+        self.key_processor = KeyProcessor(_CombinedRegistry(self))
+
+        # If `run_in_terminal` was called. This will point to a `Future` what will be
+        # set at the point when the previous run finishes.
+        self._running_in_terminal = False
+        self._running_in_terminal_f: Optional[Future[None]] = None
+
+        # Trigger initialize callback.
+        self.reset()
+
+    def _create_merged_style(self, include_default_pygments_style: Filter) -> BaseStyle:
+        """
+        Create a `Style` object that merges the default UI style, the default
+        pygments style, and the custom user style.
+        """
+        dummy_style = DummyStyle()
+        pygments_style = default_pygments_style()
+
+        @DynamicStyle
+        def conditional_pygments_style() -> BaseStyle:
+            if include_default_pygments_style():
+                return pygments_style
+            else:
+                return dummy_style
+
+        return merge_styles(
+            [
+                default_ui_style(),
+                conditional_pygments_style,
+                DynamicStyle(lambda: self.style),
+            ]
+        )
+
+    @property
+    def color_depth(self) -> ColorDepth:
+        """
+        The active :class:`.ColorDepth`.
+
+        The current value is determined as follows:
+
+        - If a color depth was given explicitly to this application, use that
+          value.
+        - Otherwise, fall back to the color depth that is reported by the
+          :class:`.Output` implementation. If the :class:`.Output` class was
+          created using `output.defaults.create_output`, then this value is
+          coming from the $PROMPT_TOOLKIT_COLOR_DEPTH environment variable.
+        """
+        depth = self._color_depth
+
+        if callable(depth):
+            depth = depth()
+
+        if depth is None:
+            depth = self.output.get_default_color_depth()
+
+        return depth
+
+    @property
+    def current_buffer(self) -> Buffer:
+        """
+        The currently focused :class:`~.Buffer`.
+
+        (This returns a dummy :class:`.Buffer` when none of the actual buffers
+        has the focus. In this case, it's really not practical to check for
+        `None` values or catch exceptions every time.)
+        """
+        return self.layout.current_buffer or Buffer(
+            name="dummy-buffer"
+        )  # Dummy buffer.
+
+    @property
+    def current_search_state(self) -> SearchState:
+        """
+        Return the current :class:`.SearchState`. (The one for the focused
+        :class:`.BufferControl`.)
+        """
+        ui_control = self.layout.current_control
+        if isinstance(ui_control, BufferControl):
+            return ui_control.search_state
+        else:
+            return SearchState()  # Dummy search state.  (Don't return None!)
+
+    def reset(self) -> None:
+        """
+        Reset everything, for reading the next input.
+        """
+        # Notice that we don't reset the buffers. (This happens just before
+        # returning, and when we have multiple buffers, we clearly want the
+        # content in the other buffers to remain unchanged between several
+        # calls of `run`. (And the same is true for the focus stack.)
+
+        self.exit_style = ""
+
+        self._background_tasks: Set[Task[None]] = set()
+
+        self.renderer.reset()
+        self.key_processor.reset()
+        self.layout.reset()
+        self.vi_state.reset()
+        self.emacs_state.reset()
+
+        # Trigger reset event.
+        self.on_reset.fire()
+
+        # Make sure that we have a 'focusable' widget focused.
+        # (The `Layout` class can't determine this.)
+        layout = self.layout
+
+        if not layout.current_control.is_focusable():
+            for w in layout.find_all_windows():
+                if w.content.is_focusable():
+                    layout.current_window = w
+                    break
+
+    def invalidate(self) -> None:
+        """
+        Thread safe way of sending a repaint trigger to the input event loop.
+        """
+        if not self._is_running:
+            # Don't schedule a redraw if we're not running.
+            # Otherwise, `get_event_loop()` in `call_soon_threadsafe` can fail.
+            # See: https://github.com/dbcli/mycli/issues/797
+            return
+
+        # `invalidate()` called if we don't have a loop yet (not running?), or
+        # after the event loop was closed.
+        if self.loop is None or self.loop.is_closed():
+            return
+
+        # Never schedule a second redraw, when a previous one has not yet been
+        # executed. (This should protect against other threads calling
+        # 'invalidate' many times, resulting in 100% CPU.)
+        if self._invalidated:
+            return
+        else:
+            self._invalidated = True
+
+        # Trigger event.
+        self.loop.call_soon_threadsafe(self.on_invalidate.fire)
+
+        def redraw() -> None:
+            self._invalidated = False
+            self._redraw()
+
+        def schedule_redraw() -> None:
+            call_soon_threadsafe(
+                redraw, max_postpone_time=self.max_render_postpone_time, loop=self.loop
+            )
+
+        if self.min_redraw_interval:
+            # When a minimum redraw interval is set, wait minimum this amount
+            # of time between redraws.
+            diff = time.time() - self._last_redraw_time
+            if diff < self.min_redraw_interval:
+
+                async def redraw_in_future() -> None:
+                    await sleep(cast(float, self.min_redraw_interval) - diff)
+                    schedule_redraw()
+
+                self.loop.call_soon_threadsafe(
+                    lambda: self.create_background_task(redraw_in_future())
+                )
+            else:
+                schedule_redraw()
+        else:
+            schedule_redraw()
+
+    @property
+    def invalidated(self) -> bool:
+        "True when a redraw operation has been scheduled."
+        return self._invalidated
+
+    def _redraw(self, render_as_done: bool = False) -> None:
+        """
+        Render the command line again. (Not thread safe!) (From other threads,
+        or if unsure, use :meth:`.Application.invalidate`.)
+
+        :param render_as_done: make sure to put the cursor after the UI.
+        """
+
+        def run_in_context() -> None:
+            # Only draw when no sub application was started.
+            if self._is_running and not self._running_in_terminal:
+                if self.min_redraw_interval:
+                    self._last_redraw_time = time.time()
+
+                # Render
+                self.render_counter += 1
+                self.before_render.fire()
+
+                if render_as_done:
+                    if self.erase_when_done:
+                        self.renderer.erase()
+                    else:
+                        # Draw in 'done' state and reset renderer.
+                        self.renderer.render(self, self.layout, is_done=render_as_done)
+                else:
+                    self.renderer.render(self, self.layout)
+
+                self.layout.update_parents_relations()
+
+                # Fire render event.
+                self.after_render.fire()
+
+                self._update_invalidate_events()
+
+        # NOTE: We want to make sure this Application is the active one. The
+        #       invalidate function is often called from a context where this
+        #       application is not the active one. (Like the
+        #       `PromptSession._auto_refresh_context`).
+        #       We copy the context in case the context was already active, to
+        #       prevent RuntimeErrors. (The rendering is not supposed to change
+        #       any context variables.)
+        if self.context is not None:
+            self.context.copy().run(run_in_context)
+
+    def _start_auto_refresh_task(self) -> None:
+        """
+        Start a while/true loop in the background for automatic invalidation of
+        the UI.
+        """
+        if self.refresh_interval is not None and self.refresh_interval != 0:
+
+            async def auto_refresh(refresh_interval: float) -> None:
+                while True:
+                    await sleep(refresh_interval)
+                    self.invalidate()
+
+            self.create_background_task(auto_refresh(self.refresh_interval))
+
+    def _update_invalidate_events(self) -> None:
+        """
+        Make sure to attach 'invalidate' handlers to all invalidate events in
+        the UI.
+        """
+        # Remove all the original event handlers. (Components can be removed
+        # from the UI.)
+        for ev in self._invalidate_events:
+            ev -= self._invalidate_handler
+
+        # Gather all new events.
+        # (All controls are able to invalidate themselves.)
+        def gather_events() -> Iterable[Event[object]]:
+            for c in self.layout.find_all_controls():
+                yield from c.get_invalidate_events()
+
+        self._invalidate_events = list(gather_events())
+
+        for ev in self._invalidate_events:
+            ev += self._invalidate_handler
+
+    def _invalidate_handler(self, sender: object) -> None:
+        """
+        Handler for invalidate events coming from UIControls.
+
+        (This handles the difference in signature between event handler and
+        `self.invalidate`. It also needs to be a method -not a nested
+        function-, so that we can remove it again .)
+        """
+        self.invalidate()
+
+    def _on_resize(self) -> None:
+        """
+        When the window size changes, we erase the current output and request
+        again the cursor position. When the CPR answer arrives, the output is
+        drawn again.
+        """
+        # Erase, request position (when cursor is at the start position)
+        # and redraw again. -- The order is important.
+        self.renderer.erase(leave_alternate_screen=False)
+        self._request_absolute_cursor_position()
+        self._redraw()
+
+    def _pre_run(self, pre_run: Optional[Callable[[], None]] = None) -> None:
+        """
+        Called during `run`.
+
+        `self.future` should be set to the new future at the point where this
+        is called in order to avoid data races. `pre_run` can be used to set a
+        `threading.Event` to synchronize with UI termination code, running in
+        another thread that would call `Application.exit`. (See the progress
+        bar code for an example.)
+        """
+        if pre_run:
+            pre_run()
+
+        # Process registered "pre_run_callables" and clear list.
+        for c in self.pre_run_callables:
+            c()
+        del self.pre_run_callables[:]
+
+    async def run_async(
+        self,
+        pre_run: Optional[Callable[[], None]] = None,
+        set_exception_handler: bool = True,
+        handle_sigint: bool = True,
+        slow_callback_duration: float = 0.5,
+    ) -> _AppResult:
+        """
+        Run the prompt_toolkit :class:`~prompt_toolkit.application.Application`
+        until :meth:`~prompt_toolkit.application.Application.exit` has been
+        called. Return the value that was passed to
+        :meth:`~prompt_toolkit.application.Application.exit`.
+
+        This is the main entry point for a prompt_toolkit
+        :class:`~prompt_toolkit.application.Application` and usually the only
+        place where the event loop is actually running.
+
+        :param pre_run: Optional callable, which is called right after the
+            "reset" of the application.
+        :param set_exception_handler: When set, in case of an exception, go out
+            of the alternate screen and hide the application, display the
+            exception, and wait for the user to press ENTER.
+        :param handle_sigint: Handle SIGINT signal if possible. This will call
+            the `<sigint>` key binding when a SIGINT is received. (This only
+            works in the main thread.)
+        :param slow_callback_duration: Display warnings if code scheduled in
+            the asyncio event loop takes more time than this. The asyncio
+            default of `0.1` is sometimes not sufficient on a slow system,
+            because exceptionally, the drawing of the app, which happens in the
+            event loop, can take a bit longer from time to time.
+        """
+        assert not self._is_running, "Application is already running."
+
+        if not in_main_thread() or sys.platform == "win32":
+            # Handling signals in other threads is not supported.
+            # Also on Windows, `add_signal_handler(signal.SIGINT, ...)` raises
+            # `NotImplementedError`.
+            # See: https://github.com/prompt-toolkit/python-prompt-toolkit/issues/1553
+            handle_sigint = False
+
+        async def _run_async(f: "asyncio.Future[_AppResult]") -> _AppResult:
+            self.context = contextvars.copy_context()
+
+            # Counter for cancelling 'flush' timeouts. Every time when a key is
+            # pressed, we start a 'flush' timer for flushing our escape key. But
+            # when any subsequent input is received, a new timer is started and
+            # the current timer will be ignored.
+            flush_task: Optional[asyncio.Task[None]] = None
+
+            # Reset.
+            # (`self.future` needs to be set when `pre_run` is called.)
+            self.reset()
+            self._pre_run(pre_run)
+
+            # Feed type ahead input first.
+            self.key_processor.feed_multiple(get_typeahead(self.input))
+            self.key_processor.process_keys()
+
+            def read_from_input() -> None:
+                nonlocal flush_task
+
+                # Ignore when we aren't running anymore. This callback will
+                # removed from the loop next time. (It could be that it was
+                # still in the 'tasks' list of the loop.)
+                # Except: if we need to process incoming CPRs.
+                if not self._is_running and not self.renderer.waiting_for_cpr:
+                    return
+
+                # Get keys from the input object.
+                keys = self.input.read_keys()
+
+                # Feed to key processor.
+                self.key_processor.feed_multiple(keys)
+                self.key_processor.process_keys()
+
+                # Quit when the input stream was closed.
+                if self.input.closed:
+                    if not f.done():
+                        f.set_exception(EOFError)
+                else:
+                    # Automatically flush keys.
+                    if flush_task:
+                        flush_task.cancel()
+                    flush_task = self.create_background_task(auto_flush_input())
+
+            async def auto_flush_input() -> None:
+                # Flush input after timeout.
+                # (Used for flushing the enter key.)
+                # This sleep can be cancelled, in that case we won't flush yet.
+                await sleep(self.ttimeoutlen)
+                flush_input()
+
+            def flush_input() -> None:
+                if not self.is_done:
+                    # Get keys, and feed to key processor.
+                    keys = self.input.flush_keys()
+                    self.key_processor.feed_multiple(keys)
+                    self.key_processor.process_keys()
+
+                    if self.input.closed:
+                        f.set_exception(EOFError)
+
+            # Enter raw mode, attach input and attach WINCH event handler.
+            with self.input.raw_mode(), self.input.attach(
+                read_from_input
+            ), attach_winch_signal_handler(self._on_resize):
+
+                # Draw UI.
+                self._request_absolute_cursor_position()
+                self._redraw()
+                self._start_auto_refresh_task()
+
+                self.create_background_task(self._poll_output_size())
+
+                # Wait for UI to finish.
+                try:
+                    result = await f
+                finally:
+                    # In any case, when the application finishes.
+                    # (Successful, or because of an error.)
+                    try:
+                        self._redraw(render_as_done=True)
+                    finally:
+                        # _redraw has a good chance to fail if it calls widgets
+                        # with bad code. Make sure to reset the renderer
+                        # anyway.
+                        self.renderer.reset()
+
+                        # Unset `is_running`, this ensures that possibly
+                        # scheduled draws won't paint during the following
+                        # yield.
+                        self._is_running = False
+
+                        # Detach event handlers for invalidate events.
+                        # (Important when a UIControl is embedded in multiple
+                        # applications, like ptterm in pymux. An invalidate
+                        # should not trigger a repaint in terminated
+                        # applications.)
+                        for ev in self._invalidate_events:
+                            ev -= self._invalidate_handler
+                        self._invalidate_events = []
+
+                        # Wait for CPR responses.
+                        if self.output.responds_to_cpr:
+                            await self.renderer.wait_for_cpr_responses()
+
+                        # Wait for the run-in-terminals to terminate.
+                        previous_run_in_terminal_f = self._running_in_terminal_f
+
+                        if previous_run_in_terminal_f:
+                            await previous_run_in_terminal_f
+
+                        # Store unprocessed input as typeahead for next time.
+                        store_typeahead(self.input, self.key_processor.empty_queue())
+
+                return result
+
+        @contextmanager
+        def get_loop() -> Iterator[AbstractEventLoop]:
+            loop = get_event_loop()
+            self.loop = loop
+
+            try:
+                yield loop
+            finally:
+                self.loop = None
+
+        @contextmanager
+        def set_is_running() -> Iterator[None]:
+            self._is_running = True
+            try:
+                yield
+            finally:
+                self._is_running = False
+
+        @contextmanager
+        def set_handle_sigint(loop: AbstractEventLoop) -> Iterator[None]:
+            if handle_sigint:
+                loop.add_signal_handler(
+                    signal.SIGINT,
+                    lambda *_: loop.call_soon_threadsafe(
+                        self.key_processor.send_sigint
+                    ),
+                )
+                try:
+                    yield
+                finally:
+                    loop.remove_signal_handler(signal.SIGINT)
+            else:
+                yield
+
+        @contextmanager
+        def set_exception_handler_ctx(loop: AbstractEventLoop) -> Iterator[None]:
+            if set_exception_handler:
+                previous_exc_handler = loop.get_exception_handler()
+                loop.set_exception_handler(self._handle_exception)
+                try:
+                    yield
+                finally:
+                    loop.set_exception_handler(previous_exc_handler)
+
+            else:
+                yield
+
+        @contextmanager
+        def set_callback_duration(loop: AbstractEventLoop) -> Iterator[None]:
+            # Set slow_callback_duration.
+            original_slow_callback_duration = loop.slow_callback_duration
+            loop.slow_callback_duration = slow_callback_duration
+            try:
+                yield
+            finally:
+                # Reset slow_callback_duration.
+                loop.slow_callback_duration = original_slow_callback_duration
+
+        @contextmanager
+        def create_future(
+            loop: AbstractEventLoop,
+        ) -> "Iterator[asyncio.Future[_AppResult]]":
+            f = loop.create_future()
+            self.future = f  # XXX: make sure to set this before calling '_redraw'.
+
+            try:
+                yield f
+            finally:
+                # Also remove the Future again. (This brings the
+                # application back to its initial state, where it also
+                # doesn't have a Future.)
+                self.future = None
+
+        with ExitStack() as stack:
+            stack.enter_context(set_is_running())
+
+            # Make sure to set `_invalidated` to `False` to begin with,
+            # otherwise we're not going to paint anything. This can happen if
+            # this application had run before on a different event loop, and a
+            # paint was scheduled using `call_soon_threadsafe` with
+            # `max_postpone_time`.
+            self._invalidated = False
+
+            loop = stack.enter_context(get_loop())
+
+            stack.enter_context(set_handle_sigint(loop))
+            stack.enter_context(set_exception_handler_ctx(loop))
+            stack.enter_context(set_callback_duration(loop))
+            stack.enter_context(set_app(self))
+            stack.enter_context(self._enable_breakpointhook())
+
+            f = stack.enter_context(create_future(loop))
+
+            try:
+                return await _run_async(f)
+            finally:
+                # Wait for the background tasks to be done. This needs to
+                # go in the finally! If `_run_async` raises
+                # `KeyboardInterrupt`, we still want to wait for the
+                # background tasks.
+                await self.cancel_and_wait_for_background_tasks()
+
+        # The `ExitStack` above is defined in typeshed in a way that it can
+        # swallow exceptions. Without next line, mypy would think that there's
+        # a possibility we don't return here. See:
+        # https://github.com/python/mypy/issues/7726
+        assert False, "unreachable"
+
+    def run(
+        self,
+        pre_run: Optional[Callable[[], None]] = None,
+        set_exception_handler: bool = True,
+        handle_sigint: bool = True,
+        in_thread: bool = False,
+    ) -> _AppResult:
+        """
+        A blocking 'run' call that waits until the UI is finished.
+
+        This will start the current asyncio event loop. If no loop is set for
+        the current thread, then it will create a new loop. If a new loop was
+        created, this won't close the new loop (if `in_thread=False`).
+
+        :param pre_run: Optional callable, which is called right after the
+            "reset" of the application.
+        :param set_exception_handler: When set, in case of an exception, go out
+            of the alternate screen and hide the application, display the
+            exception, and wait for the user to press ENTER.
+        :param in_thread: When true, run the application in a background
+            thread, and block the current thread until the application
+            terminates. This is useful if we need to be sure the application
+            won't use the current event loop (asyncio does not support nested
+            event loops). A new event loop will be created in this background
+            thread, and that loop will also be closed when the background
+            thread terminates. When this is used, it's especially important to
+            make sure that all asyncio background tasks are managed through
+            `get_appp().create_background_task()`, so that unfinished tasks are
+            properly cancelled before the event loop is closed. This is used
+            for instance in ptpython.
+        :param handle_sigint: Handle SIGINT signal. Call the key binding for
+            `Keys.SIGINT`. (This only works in the main thread.)
+        """
+        if in_thread:
+            result: _AppResult
+            exception: Optional[BaseException] = None
+
+            def run_in_thread() -> None:
+                nonlocal result, exception
+                try:
+                    result = self.run(
+                        pre_run=pre_run,
+                        set_exception_handler=set_exception_handler,
+                        # Signal handling only works in the main thread.
+                        handle_sigint=False,
+                    )
+                except BaseException as e:
+                    exception = e
+                finally:
+                    # Make sure to close the event loop in this thread. Running
+                    # the application creates a new loop (because we're in
+                    # another thread), but it doesn't get closed automatically
+                    # (also not by the garbage collector).
+                    loop = get_event_loop()
+                    loop.run_until_complete(loop.shutdown_asyncgens())
+                    loop.close()
+
+            thread = threading.Thread(target=run_in_thread)
+            thread.start()
+            thread.join()
+
+            if exception is not None:
+                raise exception
+            return result
+
+        # We don't create a new event loop by default, because we want to be
+        # sure that when this is called multiple times, each call of `run()`
+        # goes through the same event loop. This way, users can schedule
+        # background-tasks that keep running across multiple prompts.
+        try:
+            loop = get_event_loop()
+        except RuntimeError:
+            # Possibly we are not running in the main thread, where no event
+            # loop is set by default. Or somebody called `asyncio.run()`
+            # before, which closes the existing event loop. We can create a new
+            # loop.
+            loop = new_event_loop()
+            set_event_loop(loop)
+
+        return loop.run_until_complete(
+            self.run_async(
+                pre_run=pre_run,
+                set_exception_handler=set_exception_handler,
+                handle_sigint=handle_sigint,
+            )
+        )
+
+    def _handle_exception(
+        self, loop: AbstractEventLoop, context: Dict[str, Any]
+    ) -> None:
+        """
+        Handler for event loop exceptions.
+        This will print the exception, using run_in_terminal.
+        """
+        # For Python 2: we have to get traceback at this point, because
+        # we're still in the 'except:' block of the event loop where the
+        # traceback is still available. Moving this code in the
+        # 'print_exception' coroutine will loose the exception.
+        tb = get_traceback_from_context(context)
+        formatted_tb = "".join(format_tb(tb))
+
+        async def in_term() -> None:
+            async with in_terminal():
+                # Print output. Similar to 'loop.default_exception_handler',
+                # but don't use logger. (This works better on Python 2.)
+                print("\nUnhandled exception in event loop:")
+                print(formatted_tb)
+                print("Exception {}".format(context.get("exception")))
+
+                await _do_wait_for_enter("Press ENTER to continue...")
+
+        ensure_future(in_term())
+
+    @contextmanager
+    def _enable_breakpointhook(self) -> Generator[None, None, None]:
+        """
+        Install our custom breakpointhook for the duration of this context
+        manager. (We will only install the hook if no other custom hook was
+        set.)
+        """
+        if sys.version_info >= (3, 7) and sys.breakpointhook == sys.__breakpointhook__:
+            sys.breakpointhook = self._breakpointhook
+
+            try:
+                yield
+            finally:
+                sys.breakpointhook = sys.__breakpointhook__
+        else:
+            yield
+
+    def _breakpointhook(self, *a: object, **kw: object) -> None:
+        """
+        Breakpointhook which uses PDB, but ensures that the application is
+        hidden and input echoing is restored during each debugger dispatch.
+        """
+        app = self
+        # Inline import on purpose. We don't want to import pdb, if not needed.
+        import pdb
+        from types import FrameType
+
+        TraceDispatch = Callable[[FrameType, str, Any], Any]
+
+        class CustomPdb(pdb.Pdb):
+            def trace_dispatch(
+                self, frame: FrameType, event: str, arg: Any
+            ) -> TraceDispatch:
+                # Hide application.
+                app.renderer.erase()
+
+                # Detach input and dispatch to debugger.
+                with app.input.detach():
+                    with app.input.cooked_mode():
+                        return super().trace_dispatch(frame, event, arg)
+
+                # Note: we don't render the application again here, because
+                # there's a good chance that there's a breakpoint on the next
+                # line. This paint/erase cycle would move the PDB prompt back
+                # to the middle of the screen.
+
+        frame = sys._getframe().f_back
+        CustomPdb(stdout=sys.__stdout__).set_trace(frame)
+
+    def create_background_task(
+        self, coroutine: Coroutine[Any, Any, None]
+    ) -> "asyncio.Task[None]":
+        """
+        Start a background task (coroutine) for the running application. When
+        the `Application` terminates, unfinished background tasks will be
+        cancelled.
+
+        Given that we still support Python versions before 3.11, we can't use
+        task groups (and exception groups), because of that, these background
+        tasks are not allowed to raise exceptions. If they do, we'll call the
+        default exception handler from the event loop.
+
+        If at some point, we have Python 3.11 as the minimum supported Python
+        version, then we can use a `TaskGroup` (with the lifetime of
+        `Application.run_async()`, and run run the background tasks in there.
+
+        This is not threadsafe.
+        """
+        loop = self.loop or get_event_loop()
+        task: asyncio.Task[None] = loop.create_task(coroutine)
+        self._background_tasks.add(task)
+
+        task.add_done_callback(self._on_background_task_done)
+        return task
+
+    def _on_background_task_done(self, task: "asyncio.Task[None]") -> None:
+        """
+        Called when a background task completes. Remove it from
+        `_background_tasks`, and handle exceptions if any.
+        """
+        self._background_tasks.discard(task)
+
+        if task.cancelled():
+            return
+
+        exc = task.exception()
+        if exc is not None:
+            get_event_loop().call_exception_handler(
+                {
+                    "message": f"prompt_toolkit.Application background task {task!r} "
+                    "raised an unexpected exception.",
+                    "exception": exc,
+                    "task": task,
+                }
+            )
+
+    async def cancel_and_wait_for_background_tasks(self) -> None:
+        """
+        Cancel all background tasks, and wait for the cancellation to complete.
+        If any of the background tasks raised an exception, this will also
+        propagate the exception.
+
+        (If we had nurseries like Trio, this would be the `__aexit__` of a
+        nursery.)
+        """
+        for task in self._background_tasks:
+            task.cancel()
+
+        # Wait until the cancellation of the background tasks completes.
+        # `asyncio.wait()` does not propagate exceptions raised within any of
+        # these tasks, which is what we want. Otherwise, we can't distinguish
+        # between a `CancelledError` raised in this task because it got
+        # cancelled, and a `CancelledError` raised on this `await` checkpoint,
+        # because *we* got cancelled during the teardown of the application.
+        # (If we get cancelled here, then it's important to not suppress the
+        # `CancelledError`, and have it propagate.)
+        # NOTE: Currently, if we get cancelled at this point then we can't wait
+        #       for the cancellation to complete (in the future, we should be
+        #       using anyio or Python's 3.11 TaskGroup.)
+        #       Also, if we had exception groups, we could propagate an
+        #       `ExceptionGroup` if something went wrong here. Right now, we
+        #       don't propagate exceptions, but have them printed in
+        #       `_on_background_task_done`.
+        if len(self._background_tasks) > 0:
+            await asyncio.wait(
+                self._background_tasks, timeout=None, return_when=asyncio.ALL_COMPLETED
+            )
+
+    async def _poll_output_size(self) -> None:
+        """
+        Coroutine for polling the terminal dimensions.
+
+        Useful for situations where `attach_winch_signal_handler` is not sufficient:
+        - If we are not running in the main thread.
+        - On Windows.
+        """
+        size: Optional[Size] = None
+        interval = self.terminal_size_polling_interval
+
+        if interval is None:
+            return
+
+        while True:
+            await asyncio.sleep(interval)
+            new_size = self.output.get_size()
+
+            if size is not None and new_size != size:
+                self._on_resize()
+            size = new_size
+
+    def cpr_not_supported_callback(self) -> None:
+        """
+        Called when we don't receive the cursor position response in time.
+        """
+        if not self.output.responds_to_cpr:
+            return  # We know about this already.
+
+        def in_terminal() -> None:
+            self.output.write(
+                "WARNING: your terminal doesn't support cursor position requests (CPR).\r\n"
+            )
+            self.output.flush()
+
+        run_in_terminal(in_terminal)
+
+    @overload
+    def exit(self) -> None:
+        "Exit without arguments."
+
+    @overload
+    def exit(self, *, result: _AppResult, style: str = "") -> None:
+        "Exit with `_AppResult`."
+
+    @overload
+    def exit(
+        self, *, exception: Union[BaseException, Type[BaseException]], style: str = ""
+    ) -> None:
+        "Exit with exception."
+
+    def exit(
+        self,
+        result: Optional[_AppResult] = None,
+        exception: Optional[Union[BaseException, Type[BaseException]]] = None,
+        style: str = "",
+    ) -> None:
+        """
+        Exit application.
+
+        .. note::
+
+            If `Application.exit` is called before `Application.run()` is
+            called, then the `Application` won't exit (because the
+            `Application.future` doesn't correspond to the current run). Use a
+            `pre_run` hook and an event to synchronize the closing if there's a
+            chance this can happen.
+
+        :param result: Set this result for the application.
+        :param exception: Set this exception as the result for an application. For
+            a prompt, this is often `EOFError` or `KeyboardInterrupt`.
+        :param style: Apply this style on the whole content when quitting,
+            often this is 'class:exiting' for a prompt. (Used when
+            `erase_when_done` is not set.)
+        """
+        assert result is None or exception is None
+
+        if self.future is None:
+            raise Exception("Application is not running. Application.exit() failed.")
+
+        if self.future.done():
+            raise Exception("Return value already set. Application.exit() failed.")
+
+        self.exit_style = style
+
+        if exception is not None:
+            self.future.set_exception(exception)
+        else:
+            self.future.set_result(cast(_AppResult, result))
+
+    def _request_absolute_cursor_position(self) -> None:
+        """
+        Send CPR request.
+        """
+        # Note: only do this if the input queue is not empty, and a return
+        # value has not been set. Otherwise, we won't be able to read the
+        # response anyway.
+        if not self.key_processor.input_queue and not self.is_done:
+            self.renderer.request_absolute_cursor_position()
+
+    async def run_system_command(
+        self,
+        command: str,
+        wait_for_enter: bool = True,
+        display_before_text: AnyFormattedText = "",
+        wait_text: str = "Press ENTER to continue...",
+    ) -> None:
+        """
+        Run system command (While hiding the prompt. When finished, all the
+        output will scroll above the prompt.)
+
+        :param command: Shell command to be executed.
+        :param wait_for_enter: FWait for the user to press enter, when the
+            command is finished.
+        :param display_before_text: If given, text to be displayed before the
+            command executes.
+        :return: A `Future` object.
+        """
+        async with in_terminal():
+            # Try to use the same input/output file descriptors as the one,
+            # used to run this application.
+            try:
+                input_fd = self.input.fileno()
+            except AttributeError:
+                input_fd = sys.stdin.fileno()
+            try:
+                output_fd = self.output.fileno()
+            except AttributeError:
+                output_fd = sys.stdout.fileno()
+
+            # Run sub process.
+            def run_command() -> None:
+                self.print_text(display_before_text)
+                p = Popen(command, shell=True, stdin=input_fd, stdout=output_fd)
+                p.wait()
+
+            await run_in_executor_with_context(run_command)
+
+            # Wait for the user to press enter.
+            if wait_for_enter:
+                await _do_wait_for_enter(wait_text)
+
+    def suspend_to_background(self, suspend_group: bool = True) -> None:
+        """
+        (Not thread safe -- to be called from inside the key bindings.)
+        Suspend process.
+
+        :param suspend_group: When true, suspend the whole process group.
+            (This is the default, and probably what you want.)
+        """
+        # Only suspend when the operating system supports it.
+        # (Not on Windows.)
+        if _SIGTSTP is not None:
+
+            def run() -> None:
+                signal = cast(int, _SIGTSTP)
+                # Send `SIGTSTP` to own process.
+                # This will cause it to suspend.
+
+                # Usually we want the whole process group to be suspended. This
+                # handles the case when input is piped from another process.
+                if suspend_group:
+                    os.kill(0, signal)
+                else:
+                    os.kill(os.getpid(), signal)
+
+            run_in_terminal(run)
+
+    def print_text(
+        self, text: AnyFormattedText, style: Optional[BaseStyle] = None
+    ) -> None:
+        """
+        Print a list of (style_str, text) tuples to the output.
+        (When the UI is running, this method has to be called through
+        `run_in_terminal`, otherwise it will destroy the UI.)
+
+        :param text: List of ``(style_str, text)`` tuples.
+        :param style: Style class to use. Defaults to the active style in the CLI.
+        """
+        print_formatted_text(
+            output=self.output,
+            formatted_text=text,
+            style=style or self._merged_style,
+            color_depth=self.color_depth,
+            style_transformation=self.style_transformation,
+        )
+
+    @property
+    def is_running(self) -> bool:
+        "`True` when the application is currently active/running."
+        return self._is_running
+
+    @property
+    def is_done(self) -> bool:
+        if self.future:
+            return self.future.done()
+        return False
+
+    def get_used_style_strings(self) -> List[str]:
+        """
+        Return a list of used style strings. This is helpful for debugging, and
+        for writing a new `Style`.
+        """
+        attrs_for_style = self.renderer._attrs_for_style
+
+        if attrs_for_style:
+            return sorted(
+                re.sub(r"\s+", " ", style_str).strip()
+                for style_str in attrs_for_style.keys()
+            )
+
+        return []
+
+
+class _CombinedRegistry(KeyBindingsBase):
+    """
+    The `KeyBindings` of key bindings for a `Application`.
+    This merges the global key bindings with the one of the current user
+    control.
+    """
+
+    def __init__(self, app: Application[_AppResult]) -> None:
+        self.app = app
+        self._cache: SimpleCache[
+            Tuple[Window, FrozenSet[UIControl]], KeyBindingsBase
+        ] = SimpleCache()
+
+    @property
+    def _version(self) -> Hashable:
+        """Not needed - this object is not going to be wrapped in another
+        KeyBindings object."""
+        raise NotImplementedError
+
+    @property
+    def bindings(self) -> List[Binding]:
+        """Not needed - this object is not going to be wrapped in another
+        KeyBindings object."""
+        raise NotImplementedError
+
+    def _create_key_bindings(
+        self, current_window: Window, other_controls: List[UIControl]
+    ) -> KeyBindingsBase:
+        """
+        Create a `KeyBindings` object that merges the `KeyBindings` from the
+        `UIControl` with all the parent controls and the global key bindings.
+        """
+        key_bindings = []
+        collected_containers = set()
+
+        # Collect key bindings from currently focused control and all parent
+        # controls. Don't include key bindings of container parent controls.
+        container: Container = current_window
+        while True:
+            collected_containers.add(container)
+            kb = container.get_key_bindings()
+            if kb is not None:
+                key_bindings.append(kb)
+
+            if container.is_modal():
+                break
+
+            parent = self.app.layout.get_parent(container)
+            if parent is None:
+                break
+            else:
+                container = parent
+
+        # Include global bindings (starting at the top-model container).
+        for c in walk(container):
+            if c not in collected_containers:
+                kb = c.get_key_bindings()
+                if kb is not None:
+                    key_bindings.append(GlobalOnlyKeyBindings(kb))
+
+        # Add App key bindings
+        if self.app.key_bindings:
+            key_bindings.append(self.app.key_bindings)
+
+        # Add mouse bindings.
+        key_bindings.append(
+            ConditionalKeyBindings(
+                self.app._page_navigation_bindings,
+                self.app.enable_page_navigation_bindings,
+            )
+        )
+        key_bindings.append(self.app._default_bindings)
+
+        # Reverse this list. The current control's key bindings should come
+        # last. They need priority.
+        key_bindings = key_bindings[::-1]
+
+        return merge_key_bindings(key_bindings)
+
+    @property
+    def _key_bindings(self) -> KeyBindingsBase:
+        current_window = self.app.layout.current_window
+        other_controls = list(self.app.layout.find_all_controls())
+        key = current_window, frozenset(other_controls)
+
+        return self._cache.get(
+            key, lambda: self._create_key_bindings(current_window, other_controls)
+        )
+
+    def get_bindings_for_keys(self, keys: KeysTuple) -> List[Binding]:
+        return self._key_bindings.get_bindings_for_keys(keys)
+
+    def get_bindings_starting_with_keys(self, keys: KeysTuple) -> List[Binding]:
+        return self._key_bindings.get_bindings_starting_with_keys(keys)
+
+
+async def _do_wait_for_enter(wait_text: AnyFormattedText) -> None:
+    """
+    Create a sub application to wait for the enter key press.
+    This has two advantages over using 'input'/'raw_input':
+    - This will share the same input/output I/O.
+    - This doesn't block the event loop.
+    """
+    from prompt_toolkit.shortcuts import PromptSession
+
+    key_bindings = KeyBindings()
+
+    @key_bindings.add("enter")
+    def _ok(event: E) -> None:
+        event.app.exit()
+
+    @key_bindings.add(Keys.Any)
+    def _ignore(event: E) -> None:
+        "Disallow typing."
+        pass
+
+    session: PromptSession[None] = PromptSession(
+        message=wait_text, key_bindings=key_bindings
+    )
+    try:
+        await session.app.run_async()
+    except KeyboardInterrupt:
+        pass  # Control-c pressed. Don't propagate this error.
+
+
+@contextmanager
+def attach_winch_signal_handler(
+    handler: Callable[[], None]
+) -> Generator[None, None, None]:
+    """
+    Attach the given callback as a WINCH signal handler within the context
+    manager. Restore the original signal handler when done.
+
+    The `Application.run` method will register SIGWINCH, so that it will
+    properly repaint when the terminal window resizes. However, using
+    `run_in_terminal`, we can temporarily send an application to the
+    background, and run an other app in between, which will then overwrite the
+    SIGWINCH. This is why it's important to restore the handler when the app
+    terminates.
+    """
+    # The tricky part here is that signals are registered in the Unix event
+    # loop with a wakeup fd, but another application could have registered
+    # signals using signal.signal directly. For now, the implementation is
+    # hard-coded for the `asyncio.unix_events._UnixSelectorEventLoop`.
+
+    # No WINCH? Then don't do anything.
+    sigwinch = getattr(signal, "SIGWINCH", None)
+    if sigwinch is None or not in_main_thread():
+        yield
+        return
+
+    # Keep track of the previous handler.
+    # (Only UnixSelectorEventloop has `_signal_handlers`.)
+    loop = get_event_loop()
+    previous_winch_handler = getattr(loop, "_signal_handlers", {}).get(sigwinch)
+
+    try:
+        loop.add_signal_handler(sigwinch, handler)
+        yield
+    finally:
+        # Restore the previous signal handler.
+        loop.remove_signal_handler(sigwinch)
+        if previous_winch_handler is not None:
+            loop.add_signal_handler(
+                sigwinch,
+                previous_winch_handler._callback,
+                *previous_winch_handler._args,
+            )
diff --git a/src/prompt_toolkit/application/current.py b/src/prompt_toolkit/application/current.py
new file mode 100644
index 0000000..ae69bfd
--- /dev/null
+++ b/src/prompt_toolkit/application/current.py
@@ -0,0 +1,197 @@
+import sys
+from contextlib import contextmanager
+from typing import TYPE_CHECKING, Any, Generator, Optional
+
+try:
+    from contextvars import ContextVar
+except ImportError:
+    from prompt_toolkit.eventloop.dummy_contextvars import ContextVar  # type: ignore
+
+if TYPE_CHECKING:
+    from prompt_toolkit.input.base import Input
+    from prompt_toolkit.output.base import Output
+
+    from .application import Application
+
+__all__ = [
+    "AppSession",
+    "get_app_session",
+    "get_app",
+    "get_app_or_none",
+    "set_app",
+    "create_app_session",
+    "create_app_session_from_tty",
+]
+
+
+class AppSession:
+    """
+    An AppSession is an interactive session, usually connected to one terminal.
+    Within one such session, interaction with many applications can happen, one
+    after the other.
+
+    The input/output device is not supposed to change during one session.
+
+    Warning: Always use the `create_app_session` function to create an
+    instance, so that it gets activated correctly.
+
+    :param input: Use this as a default input for all applications
+        running in this session, unless an input is passed to the `Application`
+        explicitely.
+    :param output: Use this as a default output.
+    """
+
+    def __init__(
+        self, input: Optional["Input"] = None, output: Optional["Output"] = None
+    ) -> None:
+
+        self._input = input
+        self._output = output
+
+        # The application will be set dynamically by the `set_app` context
+        # manager. This is called in the application itself.
+        self.app: Optional["Application[Any]"] = None
+
+    def __repr__(self) -> str:
+        return f"AppSession(app={self.app!r})"
+
+    @property
+    def input(self) -> "Input":
+        if self._input is None:
+            from prompt_toolkit.input.defaults import create_input
+
+            self._input = create_input()
+        return self._input
+
+    @property
+    def output(self) -> "Output":
+        if self._output is None:
+            from prompt_toolkit.output.defaults import create_output
+
+            self._output = create_output()
+        return self._output
+
+
+_current_app_session: ContextVar["AppSession"] = ContextVar(
+    "_current_app_session", default=AppSession()
+)
+
+
+def get_app_session() -> AppSession:
+    return _current_app_session.get()
+
+
+def get_app() -> "Application[Any]":
+    """
+    Get the current active (running) Application.
+    An :class:`.Application` is active during the
+    :meth:`.Application.run_async` call.
+
+    We assume that there can only be one :class:`.Application` active at the
+    same time. There is only one terminal window, with only one stdin and
+    stdout. This makes the code significantly easier than passing around the
+    :class:`.Application` everywhere.
+
+    If no :class:`.Application` is running, then return by default a
+    :class:`.DummyApplication`. For practical reasons, we prefer to not raise
+    an exception. This way, we don't have to check all over the place whether
+    an actual `Application` was returned.
+
+    (For applications like pymux where we can have more than one `Application`,
+    we'll use a work-around to handle that.)
+    """
+    session = _current_app_session.get()
+    if session.app is not None:
+        return session.app
+
+    from .dummy import DummyApplication
+
+    return DummyApplication()
+
+
+def get_app_or_none() -> Optional["Application[Any]"]:
+    """
+    Get the current active (running) Application, or return `None` if no
+    application is running.
+    """
+    session = _current_app_session.get()
+    return session.app
+
+
+@contextmanager
+def set_app(app: "Application[Any]") -> Generator[None, None, None]:
+    """
+    Context manager that sets the given :class:`.Application` active in an
+    `AppSession`.
+
+    This should only be called by the `Application` itself.
+    The application will automatically be active while its running. If you want
+    the application to be active in other threads/coroutines, where that's not
+    the case, use `contextvars.copy_context()`, or use `Application.context` to
+    run it in the appropriate context.
+    """
+    session = _current_app_session.get()
+
+    previous_app = session.app
+    session.app = app
+    try:
+        yield
+    finally:
+        session.app = previous_app
+
+
+@contextmanager
+def create_app_session(
+    input: Optional["Input"] = None, output: Optional["Output"] = None
+) -> Generator[AppSession, None, None]:
+    """
+    Create a separate AppSession.
+
+    This is useful if there can be multiple individual `AppSession`s going on.
+    Like in the case of an Telnet/SSH server. This functionality uses
+    contextvars and requires at least Python 3.7.
+    """
+    if sys.version_info <= (3, 6):
+        raise RuntimeError("Application sessions require Python 3.7.")
+
+    # If no input/output is specified, fall back to the current input/output,
+    # whatever that is.
+    if input is None:
+        input = get_app_session().input
+    if output is None:
+        output = get_app_session().output
+
+    # Create new `AppSession` and activate.
+    session = AppSession(input=input, output=output)
+
+    token = _current_app_session.set(session)
+    try:
+        yield session
+    finally:
+        _current_app_session.reset(token)
+
+
+@contextmanager
+def create_app_session_from_tty() -> Generator[AppSession, None, None]:
+    """
+    Create `AppSession` that always prefers the TTY input/output.
+
+    Even if `sys.stdin` and `sys.stdout` are connected to input/output pipes,
+    this will still use the terminal for interaction (because `sys.stderr` is
+    still connected to the terminal).
+
+    Usage::
+
+        from prompt_toolkit.shortcuts import prompt
+
+        with create_app_session_from_tty():
+            prompt('>')
+    """
+    from prompt_toolkit.input.defaults import create_input
+    from prompt_toolkit.output.defaults import create_output
+
+    input = create_input(always_prefer_tty=True)
+    output = create_output(always_prefer_tty=True)
+
+    with create_app_session(input=input, output=output) as app_session:
+        yield app_session
diff --git a/src/prompt_toolkit/application/dummy.py b/src/prompt_toolkit/application/dummy.py
new file mode 100644
index 0000000..4e5e4aa
--- /dev/null
+++ b/src/prompt_toolkit/application/dummy.py
@@ -0,0 +1,51 @@
+from typing import Callable, Optional
+
+from prompt_toolkit.formatted_text import AnyFormattedText
+from prompt_toolkit.input import DummyInput
+from prompt_toolkit.output import DummyOutput
+
+from .application import Application
+
+__all__ = [
+    "DummyApplication",
+]
+
+
+class DummyApplication(Application[None]):
+    """
+    When no :class:`.Application` is running,
+    :func:`.get_app` will run an instance of this :class:`.DummyApplication` instead.
+    """
+
+    def __init__(self) -> None:
+        super().__init__(output=DummyOutput(), input=DummyInput())
+
+    def run(
+        self,
+        pre_run: Optional[Callable[[], None]] = None,
+        set_exception_handler: bool = True,
+        handle_sigint: bool = True,
+        in_thread: bool = False,
+    ) -> None:
+        raise NotImplementedError("A DummyApplication is not supposed to run.")
+
+    async def run_async(
+        self,
+        pre_run: Optional[Callable[[], None]] = None,
+        set_exception_handler: bool = True,
+        handle_sigint: bool = True,
+        slow_callback_duration: float = 0.5,
+    ) -> None:
+        raise NotImplementedError("A DummyApplication is not supposed to run.")
+
+    async def run_system_command(
+        self,
+        command: str,
+        wait_for_enter: bool = True,
+        display_before_text: AnyFormattedText = "",
+        wait_text: str = "",
+    ) -> None:
+        raise NotImplementedError
+
+    def suspend_to_background(self, suspend_group: bool = True) -> None:
+        raise NotImplementedError
diff --git a/src/prompt_toolkit/application/run_in_terminal.py b/src/prompt_toolkit/application/run_in_terminal.py
new file mode 100644
index 0000000..d5ef8aa
--- /dev/null
+++ b/src/prompt_toolkit/application/run_in_terminal.py
@@ -0,0 +1,117 @@
+"""
+Tools for running functions on the terminal above the current application or prompt.
+"""
+import sys
+from asyncio import Future, ensure_future
+from typing import AsyncGenerator, Awaitable, Callable, TypeVar
+
+from prompt_toolkit.eventloop import run_in_executor_with_context
+
+from .current import get_app_or_none
+
+if sys.version_info >= (3, 7):
+    from contextlib import asynccontextmanager
+else:
+    from prompt_toolkit.eventloop.async_context_manager import asynccontextmanager
+
+
+__all__ = [
+    "run_in_terminal",
+    "in_terminal",
+]
+
+_T = TypeVar("_T")
+
+
+def run_in_terminal(
+    func: Callable[[], _T], render_cli_done: bool = False, in_executor: bool = False
+) -> Awaitable[_T]:
+    """
+    Run function on the terminal above the current application or prompt.
+
+    What this does is first hiding the prompt, then running this callable
+    (which can safely output to the terminal), and then again rendering the
+    prompt which causes the output of this function to scroll above the
+    prompt.
+
+    ``func`` is supposed to be a synchronous function. If you need an
+    asynchronous version of this function, use the ``in_terminal`` context
+    manager directly.
+
+    :param func: The callable to execute.
+    :param render_cli_done: When True, render the interface in the
+            'Done' state first, then execute the function. If False,
+            erase the interface first.
+    :param in_executor: When True, run in executor. (Use this for long
+        blocking functions, when you don't want to block the event loop.)
+
+    :returns: A `Future`.
+    """
+
+    async def run() -> _T:
+        async with in_terminal(render_cli_done=render_cli_done):
+            if in_executor:
+                return await run_in_executor_with_context(func)
+            else:
+                return func()
+
+    return ensure_future(run())
+
+
+@asynccontextmanager
+async def in_terminal(render_cli_done: bool = False) -> AsyncGenerator[None, None]:
+    """
+    Asynchronous context manager that suspends the current application and runs
+    the body in the terminal.
+
+    .. code::
+
+        async def f():
+            async with in_terminal():
+                call_some_function()
+                await call_some_async_function()
+    """
+    app = get_app_or_none()
+    if app is None or not app._is_running:
+        yield
+        return
+
+    # When a previous `run_in_terminal` call was in progress. Wait for that
+    # to finish, before starting this one. Chain to previous call.
+    previous_run_in_terminal_f = app._running_in_terminal_f
+    new_run_in_terminal_f: Future[None] = Future()
+    app._running_in_terminal_f = new_run_in_terminal_f
+
+    # Wait for the previous `run_in_terminal` to finish.
+    if previous_run_in_terminal_f is not None:
+        await previous_run_in_terminal_f
+
+    # Wait for all CPRs to arrive. We don't want to detach the input until
+    # all cursor position responses have been arrived. Otherwise, the tty
+    # will echo its input and can show stuff like ^[[39;1R.
+    if app.output.responds_to_cpr:
+        await app.renderer.wait_for_cpr_responses()
+
+    # Draw interface in 'done' state, or erase.
+    if render_cli_done:
+        app._redraw(render_as_done=True)
+    else:
+        app.renderer.erase()
+
+    # Disable rendering.
+    app._running_in_terminal = True
+
+    # Detach input.
+    try:
+        with app.input.detach():
+            with app.input.cooked_mode():
+                yield
+    finally:
+        # Redraw interface again.
+        try:
+            app._running_in_terminal = False
+            app.renderer.reset()
+            app._request_absolute_cursor_position()
+            app._redraw()
+        finally:
+            new_run_in_terminal_f.set_result(None)
diff --git a/src/prompt_toolkit/auto_suggest.py b/src/prompt_toolkit/auto_suggest.py
new file mode 100644
index 0000000..7099b8e
--- /dev/null
+++ b/src/prompt_toolkit/auto_suggest.py
@@ -0,0 +1,187 @@
+"""
+`Fish-style <http://fishshell.com/>`_  like auto-suggestion.
+
+While a user types input in a certain buffer, suggestions are generated
+(asynchronously.) Usually, they are displayed after the input. When the cursor
+presses the right arrow and the cursor is at the end of the input, the
+suggestion will be inserted.
+
+If you want the auto suggestions to be asynchronous (in a background thread),
+because they take too much time, and could potentially block the event loop,
+then wrap the :class:`.AutoSuggest` instance into a
+:class:`.ThreadedAutoSuggest`.
+"""
+from abc import ABCMeta, abstractmethod
+from typing import TYPE_CHECKING, Callable, Optional, Union
+
+from prompt_toolkit.eventloop import run_in_executor_with_context
+
+from .document import Document
+from .filters import Filter, to_filter
+
+if TYPE_CHECKING:
+    from .buffer import Buffer
+
+__all__ = [
+    "Suggestion",
+    "AutoSuggest",
+    "ThreadedAutoSuggest",
+    "DummyAutoSuggest",
+    "AutoSuggestFromHistory",
+    "ConditionalAutoSuggest",
+    "DynamicAutoSuggest",
+]
+
+
+class Suggestion:
+    """
+    Suggestion returned by an auto-suggest algorithm.
+
+    :param text: The suggestion text.
+    """
+
+    def __init__(self, text: str) -> None:
+        self.text = text
+
+    def __repr__(self) -> str:
+        return "Suggestion(%s)" % self.text
+
+
+class AutoSuggest(metaclass=ABCMeta):
+    """
+    Base class for auto suggestion implementations.
+    """
+
+    @abstractmethod
+    def get_suggestion(
+        self, buffer: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        """
+        Return `None` or a :class:`.Suggestion` instance.
+
+        We receive both :class:`~prompt_toolkit.buffer.Buffer` and
+        :class:`~prompt_toolkit.document.Document`. The reason is that auto
+        suggestions are retrieved asynchronously. (Like completions.) The
+        buffer text could be changed in the meantime, but ``document`` contains
+        the buffer document like it was at the start of the auto suggestion
+        call. So, from here, don't access ``buffer.text``, but use
+        ``document.text`` instead.
+
+        :param buffer: The :class:`~prompt_toolkit.buffer.Buffer` instance.
+        :param document: The :class:`~prompt_toolkit.document.Document` instance.
+        """
+
+    async def get_suggestion_async(
+        self, buff: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        """
+        Return a :class:`.Future` which is set when the suggestions are ready.
+        This function can be overloaded in order to provide an asynchronous
+        implementation.
+        """
+        return self.get_suggestion(buff, document)
+
+
+class ThreadedAutoSuggest(AutoSuggest):
+    """
+    Wrapper that runs auto suggestions in a thread.
+    (Use this to prevent the user interface from becoming unresponsive if the
+    generation of suggestions takes too much time.)
+    """
+
+    def __init__(self, auto_suggest: AutoSuggest) -> None:
+        self.auto_suggest = auto_suggest
+
+    def get_suggestion(
+        self, buff: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        return self.auto_suggest.get_suggestion(buff, document)
+
+    async def get_suggestion_async(
+        self, buff: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        """
+        Run the `get_suggestion` function in a thread.
+        """
+
+        def run_get_suggestion_thread() -> Optional[Suggestion]:
+            return self.get_suggestion(buff, document)
+
+        return await run_in_executor_with_context(run_get_suggestion_thread)
+
+
+class DummyAutoSuggest(AutoSuggest):
+    """
+    AutoSuggest class that doesn't return any suggestion.
+    """
+
+    def get_suggestion(
+        self, buffer: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        return None  # No suggestion
+
+
+class AutoSuggestFromHistory(AutoSuggest):
+    """
+    Give suggestions based on the lines in the history.
+    """
+
+    def get_suggestion(
+        self, buffer: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        history = buffer.history
+
+        # Consider only the last line for the suggestion.
+        text = document.text.rsplit("\n", 1)[-1]
+
+        # Only create a suggestion when this is not an empty line.
+        if text.strip():
+            # Find first matching line in history.
+            for string in reversed(list(history.get_strings())):
+                for line in reversed(string.splitlines()):
+                    if line.startswith(text):
+                        return Suggestion(line[len(text) :])
+
+        return None
+
+
+class ConditionalAutoSuggest(AutoSuggest):
+    """
+    Auto suggest that can be turned on and of according to a certain condition.
+    """
+
+    def __init__(self, auto_suggest: AutoSuggest, filter: Union[bool, Filter]) -> None:
+
+        self.auto_suggest = auto_suggest
+        self.filter = to_filter(filter)
+
+    def get_suggestion(
+        self, buffer: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        if self.filter():
+            return self.auto_suggest.get_suggestion(buffer, document)
+
+        return None
+
+
+class DynamicAutoSuggest(AutoSuggest):
+    """
+    Validator class that can dynamically returns any Validator.
+
+    :param get_validator: Callable that returns a :class:`.Validator` instance.
+    """
+
+    def __init__(self, get_auto_suggest: Callable[[], Optional[AutoSuggest]]) -> None:
+        self.get_auto_suggest = get_auto_suggest
+
+    def get_suggestion(
+        self, buff: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        auto_suggest = self.get_auto_suggest() or DummyAutoSuggest()
+        return auto_suggest.get_suggestion(buff, document)
+
+    async def get_suggestion_async(
+        self, buff: "Buffer", document: Document
+    ) -> Optional[Suggestion]:
+        auto_suggest = self.get_auto_suggest() or DummyAutoSuggest()
+        return await auto_suggest.get_suggestion_async(buff, document)
diff --git a/src/prompt_toolkit/buffer.py b/src/prompt_toolkit/buffer.py
new file mode 100644
index 0000000..72dde91
--- /dev/null
+++ b/src/prompt_toolkit/buffer.py
@@ -0,0 +1,2044 @@
+"""
+Data structures for the Buffer.
+It holds the text, cursor position, history, etc...
+"""
+import asyncio
+import logging
+import os
+import re
+import shlex
+import shutil
+import subprocess
+import tempfile
+from collections import deque
+from enum import Enum
+from functools import wraps
+from typing import (
+    Any,
+    Awaitable,
+    Callable,
+    Coroutine,
+    Deque,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Tuple,
+    TypeVar,
+    Union,
+    cast,
+)
+
+from .application.current import get_app
+from .application.run_in_terminal import run_in_terminal
+from .auto_suggest import AutoSuggest, Suggestion
+from .cache import FastDictCache
+from .clipboard import ClipboardData
+from .completion import (
+    CompleteEvent,
+    Completer,
+    Completion,
+    DummyCompleter,
+    get_common_complete_suffix,
+)
+from .document import Document
+from .eventloop import aclosing
+from .filters import FilterOrBool, to_filter
+from .history import History, InMemoryHistory
+from .search import SearchDirection, SearchState
+from .selection import PasteMode, SelectionState, SelectionType
+from .utils import Event, to_str
+from .validation import ValidationError, Validator
+
+__all__ = [
+    "EditReadOnlyBuffer",
+    "Buffer",
+    "CompletionState",
+    "indent",
+    "unindent",
+    "reshape_text",
+]
+
+logger = logging.getLogger(__name__)
+
+
+class EditReadOnlyBuffer(Exception):
+    "Attempt editing of read-only :class:`.Buffer`."
+
+
+class ValidationState(Enum):
+    "The validation state of a buffer. This is set after the validation."
+    VALID = "VALID"
+    INVALID = "INVALID"
+    UNKNOWN = "UNKNOWN"
+
+
+class CompletionState:
+    """
+    Immutable class that contains a completion state.
+    """
+
+    def __init__(
+        self,
+        original_document: "Document",
+        completions: Optional[List["Completion"]] = None,
+        complete_index: Optional[int] = None,
+    ) -> None:
+
+        #: Document as it was when the completion started.
+        self.original_document = original_document
+
+        #: List of all the current Completion instances which are possible at
+        #: this point.
+        self.completions = completions or []
+
+        #: Position in the `completions` array.
+        #: This can be `None` to indicate "no completion", the original text.
+        self.complete_index = complete_index  # Position in the `_completions` array.
+
+    def __repr__(self) -> str:
+        return "{}({!r}, <{!r}> completions, index={!r})".format(
+            self.__class__.__name__,
+            self.original_document,
+            len(self.completions),
+            self.complete_index,
+        )
+
+    def go_to_index(self, index: Optional[int]) -> None:
+        """
+        Create a new :class:`.CompletionState` object with the new index.
+
+        When `index` is `None` deselect the completion.
+        """
+        if self.completions:
+            assert index is None or 0 <= index < len(self.completions)
+            self.complete_index = index
+
+    def new_text_and_position(self) -> Tuple[str, int]:
+        """
+        Return (new_text, new_cursor_position) for this completion.
+        """
+        if self.complete_index is None:
+            return self.original_document.text, self.original_document.cursor_position
+        else:
+            original_text_before_cursor = self.original_document.text_before_cursor
+            original_text_after_cursor = self.original_document.text_after_cursor
+
+            c = self.completions[self.complete_index]
+            if c.start_position == 0:
+                before = original_text_before_cursor
+            else:
+                before = original_text_before_cursor[: c.start_position]
+
+            new_text = before + c.text + original_text_after_cursor
+            new_cursor_position = len(before) + len(c.text)
+            return new_text, new_cursor_position
+
+    @property
+    def current_completion(self) -> Optional["Completion"]:
+        """
+        Return the current completion, or return `None` when no completion is
+        selected.
+        """
+        if self.complete_index is not None:
+            return self.completions[self.complete_index]
+        return None
+
+
+_QUOTED_WORDS_RE = re.compile(r"""(\s+|".*?"|'.*?')""")
+
+
+class YankNthArgState:
+    """
+    For yank-last-arg/yank-nth-arg: Keep track of where we are in the history.
+    """
+
+    def __init__(
+        self, history_position: int = 0, n: int = -1, previous_inserted_word: str = ""
+    ) -> None:
+
+        self.history_position = history_position
+        self.previous_inserted_word = previous_inserted_word
+        self.n = n
+
+    def __repr__(self) -> str:
+        return "{}(history_position={!r}, n={!r}, previous_inserted_word={!r})".format(
+            self.__class__.__name__,
+            self.history_position,
+            self.n,
+            self.previous_inserted_word,
+        )
+
+
+BufferEventHandler = Callable[["Buffer"], None]
+BufferAcceptHandler = Callable[["Buffer"], bool]
+
+
+class Buffer:
+    """
+    The core data structure that holds the text and cursor position of the
+    current input line and implements all text manipulations on top of it. It
+    also implements the history, undo stack and the completion state.
+
+    :param completer: :class:`~prompt_toolkit.completion.Completer` instance.
+    :param history: :class:`~prompt_toolkit.history.History` instance.
+    :param tempfile_suffix: The tempfile suffix (extension) to be used for the
+        "open in editor" function. For a Python REPL, this would be ".py", so
+        that the editor knows the syntax highlighting to use. This can also be
+        a callable that returns a string.
+    :param tempfile: For more advanced tempfile situations where you need
+        control over the subdirectories and filename. For a Git Commit Message,
+        this would be ".git/COMMIT_EDITMSG", so that the editor knows the syntax
+        highlighting to use. This can also be a callable that returns a string.
+    :param name: Name for this buffer. E.g. DEFAULT_BUFFER. This is mostly
+        useful for key bindings where we sometimes prefer to refer to a buffer
+        by their name instead of by reference.
+    :param accept_handler: Called when the buffer input is accepted. (Usually
+        when the user presses `enter`.) The accept handler receives this
+        `Buffer` as input and should return True when the buffer text should be
+        kept instead of calling reset.
+
+        In case of a `PromptSession` for instance, we want to keep the text,
+        because we will exit the application, and only reset it during the next
+        run.
+
+    Events:
+
+    :param on_text_changed: When the buffer text changes. (Callable or None.)
+    :param on_text_insert: When new text is inserted. (Callable or None.)
+    :param on_cursor_position_changed: When the cursor moves. (Callable or None.)
+    :param on_completions_changed: When the completions were changed. (Callable or None.)
+    :param on_suggestion_set: When an auto-suggestion text has been set. (Callable or None.)
+
+    Filters:
+
+    :param complete_while_typing: :class:`~prompt_toolkit.filters.Filter`
+        or `bool`. Decide whether or not to do asynchronous autocompleting while
+        typing.
+    :param validate_while_typing: :class:`~prompt_toolkit.filters.Filter`
+        or `bool`. Decide whether or not to do asynchronous validation while
+        typing.
+    :param enable_history_search: :class:`~prompt_toolkit.filters.Filter` or
+        `bool` to indicate when up-arrow partial string matching is enabled. It
+        is advised to not enable this at the same time as
+        `complete_while_typing`, because when there is an autocompletion found,
+        the up arrows usually browse through the completions, rather than
+        through the history.
+    :param read_only: :class:`~prompt_toolkit.filters.Filter`. When True,
+        changes will not be allowed.
+    :param multiline: :class:`~prompt_toolkit.filters.Filter` or `bool`. When
+        not set, pressing `Enter` will call the `accept_handler`.  Otherwise,
+        pressing `Esc-Enter` is required.
+    """
+
+    def __init__(
+        self,
+        completer: Optional[Completer] = None,
+        auto_suggest: Optional[AutoSuggest] = None,
+        history: Optional[History] = None,
+        validator: Optional[Validator] = None,
+        tempfile_suffix: Union[str, Callable[[], str]] = "",
+        tempfile: Union[str, Callable[[], str]] = "",
+        name: str = "",
+        complete_while_typing: FilterOrBool = False,
+        validate_while_typing: FilterOrBool = False,
+        enable_history_search: FilterOrBool = False,
+        document: Optional[Document] = None,
+        accept_handler: Optional[BufferAcceptHandler] = None,
+        read_only: FilterOrBool = False,
+        multiline: FilterOrBool = True,
+        on_text_changed: Optional[BufferEventHandler] = None,
+        on_text_insert: Optional[BufferEventHandler] = None,
+        on_cursor_position_changed: Optional[BufferEventHandler] = None,
+        on_completions_changed: Optional[BufferEventHandler] = None,
+        on_suggestion_set: Optional[BufferEventHandler] = None,
+    ):
+
+        # Accept both filters and booleans as input.
+        enable_history_search = to_filter(enable_history_search)
+        complete_while_typing = to_filter(complete_while_typing)
+        validate_while_typing = to_filter(validate_while_typing)
+        read_only = to_filter(read_only)
+        multiline = to_filter(multiline)
+
+        self.completer = completer or DummyCompleter()
+        self.auto_suggest = auto_suggest
+        self.validator = validator
+        self.tempfile_suffix = tempfile_suffix
+        self.tempfile = tempfile
+        self.name = name
+        self.accept_handler = accept_handler
+
+        # Filters. (Usually, used by the key bindings to drive the buffer.)
+        self.complete_while_typing = complete_while_typing
+        self.validate_while_typing = validate_while_typing
+        self.enable_history_search = enable_history_search
+        self.read_only = read_only
+        self.multiline = multiline
+
+        # Text width. (For wrapping, used by the Vi 'gq' operator.)
+        self.text_width = 0
+
+        #: The command buffer history.
+        # Note that we shouldn't use a lazy 'or' here. bool(history) could be
+        # False when empty.
+        self.history = InMemoryHistory() if history is None else history
+
+        self.__cursor_position = 0
+
+        # Events
+        self.on_text_changed: Event["Buffer"] = Event(self, on_text_changed)
+        self.on_text_insert: Event["Buffer"] = Event(self, on_text_insert)
+        self.on_cursor_position_changed: Event["Buffer"] = Event(
+            self, on_cursor_position_changed
+        )
+        self.on_completions_changed: Event["Buffer"] = Event(
+            self, on_completions_changed
+        )
+        self.on_suggestion_set: Event["Buffer"] = Event(self, on_suggestion_set)
+
+        # Document cache. (Avoid creating new Document instances.)
+        self._document_cache: FastDictCache[
+            Tuple[str, int, Optional[SelectionState]], Document
+        ] = FastDictCache(Document, size=10)
+
+        # Create completer / auto suggestion / validation coroutines.
+        self._async_suggester = self._create_auto_suggest_coroutine()
+        self._async_completer = self._create_completer_coroutine()
+        self._async_validator = self._create_auto_validate_coroutine()
+
+        # Asyncio task for populating the history.
+        self._load_history_task: Optional[asyncio.Future[None]] = None
+
+        # Reset other attributes.
+        self.reset(document=document)
+
+    def __repr__(self) -> str:
+        if len(self.text) < 15:
+            text = self.text
+        else:
+            text = self.text[:12] + "..."
+
+        return f"<Buffer(name={self.name!r}, text={text!r}) at {id(self)!r}>"
+
+    def reset(
+        self, document: Optional[Document] = None, append_to_history: bool = False
+    ) -> None:
+        """
+        :param append_to_history: Append current input to history first.
+        """
+        if append_to_history:
+            self.append_to_history()
+
+        document = document or Document()
+
+        self.__cursor_position = document.cursor_position
+
+        # `ValidationError` instance. (Will be set when the input is wrong.)
+        self.validation_error: Optional[ValidationError] = None
+        self.validation_state: Optional[ValidationState] = ValidationState.UNKNOWN
+
+        # State of the selection.
+        self.selection_state: Optional[SelectionState] = None
+
+        # Multiple cursor mode. (When we press 'I' or 'A' in visual-block mode,
+        # we can insert text on multiple lines at once. This is implemented by
+        # using multiple cursors.)
+        self.multiple_cursor_positions: List[int] = []
+
+        # When doing consecutive up/down movements, prefer to stay at this column.
+        self.preferred_column: Optional[int] = None
+
+        # State of complete browser
+        # For interactive completion through Ctrl-N/Ctrl-P.
+        self.complete_state: Optional[CompletionState] = None
+
+        # State of Emacs yank-nth-arg completion.
+        self.yank_nth_arg_state: Optional[YankNthArgState] = None  # for yank-nth-arg.
+
+        # Remember the document that we had *right before* the last paste
+        # operation. This is used for rotating through the kill ring.
+        self.document_before_paste: Optional[Document] = None
+
+        # Current suggestion.
+        self.suggestion: Optional[Suggestion] = None
+
+        # The history search text. (Used for filtering the history when we
+        # browse through it.)
+        self.history_search_text: Optional[str] = None
+
+        # Undo/redo stacks (stack of `(text, cursor_position)`).
+        self._undo_stack: List[Tuple[str, int]] = []
+        self._redo_stack: List[Tuple[str, int]] = []
+
+        # Cancel history loader. If history loading was still ongoing.
+        # Cancel the `_load_history_task`, so that next repaint of the
+        # `BufferControl` we will repopulate it.
+        if self._load_history_task is not None:
+            self._load_history_task.cancel()
+        self._load_history_task = None
+
+        #: The working lines. Similar to history, except that this can be
+        #: modified. The user can press arrow_up and edit previous entries.
+        #: Ctrl-C should reset this, and copy the whole history back in here.
+        #: Enter should process the current command and append to the real
+        #: history.
+        self._working_lines: Deque[str] = deque([document.text])
+        self.__working_index = 0
+
+    def load_history_if_not_yet_loaded(self) -> None:
+        """
+        Create task for populating the buffer history (if not yet done).
+
+        Note::
+
+            This needs to be called from within the event loop of the
+            application, because history loading is async, and we need to be
+            sure the right event loop is active. Therefor, we call this method
+            in the `BufferControl.create_content`.
+
+            There are situations where prompt_toolkit applications are created
+            in one thread, but will later run in a different thread (Ptpython
+            is one example. The REPL runs in a separate thread, in order to
+            prevent interfering with a potential different event loop in the
+            main thread. The REPL UI however is still created in the main
+            thread.) We could decide to not support creating prompt_toolkit
+            objects in one thread and running the application in a different
+            thread, but history loading is the only place where it matters, and
+            this solves it.
+        """
+        if self._load_history_task is None:
+
+            async def load_history() -> None:
+                async for item in self.history.load():
+                    self._working_lines.appendleft(item)
+                    self.__working_index += 1
+
+            self._load_history_task = get_app().create_background_task(load_history())
+
+            def load_history_done(f: "asyncio.Future[None]") -> None:
+                """
+                Handle `load_history` result when either done, cancelled, or
+                when an exception was raised.
+                """
+                try:
+                    f.result()
+                except asyncio.CancelledError:
+                    # Ignore cancellation. But handle it, so that we don't get
+                    # this traceback.
+                    pass
+                except GeneratorExit:
+                    # Probably not needed, but we had situations where
+                    # `GeneratorExit` was raised in `load_history` during
+                    # cancellation.
+                    pass
+                except BaseException:
+                    # Log error if something goes wrong. (We don't have a
+                    # caller to which we can propagate this exception.)
+                    logger.exception("Loading history failed")
+
+            self._load_history_task.add_done_callback(load_history_done)
+
+    # <getters/setters>
+
+    def _set_text(self, value: str) -> bool:
+        """set text at current working_index. Return whether it changed."""
+        working_index = self.working_index
+        working_lines = self._working_lines
+
+        original_value = working_lines[working_index]
+        working_lines[working_index] = value
+
+        # Return True when this text has been changed.
+        if len(value) != len(original_value):
+            # For Python 2, it seems that when two strings have a different
+            # length and one is a prefix of the other, Python still scans
+            # character by character to see whether the strings are different.
+            # (Some benchmarking showed significant differences for big
+            # documents. >100,000 of lines.)
+            return True
+        elif value != original_value:
+            return True
+        return False
+
+    def _set_cursor_position(self, value: int) -> bool:
+        """Set cursor position. Return whether it changed."""
+        original_position = self.__cursor_position
+        self.__cursor_position = max(0, value)
+
+        return self.__cursor_position != original_position
+
+    @property
+    def text(self) -> str:
+        return self._working_lines[self.working_index]
+
+    @text.setter
+    def text(self, value: str) -> None:
+        """
+        Setting text. (When doing this, make sure that the cursor_position is
+        valid for this text. text/cursor_position should be consistent at any time,
+        otherwise set a Document instead.)
+        """
+        # Ensure cursor position remains within the size of the text.
+        if self.cursor_position > len(value):
+            self.cursor_position = len(value)
+
+        # Don't allow editing of read-only buffers.
+        if self.read_only():
+            raise EditReadOnlyBuffer()
+
+        changed = self._set_text(value)
+
+        if changed:
+            self._text_changed()
+
+            # Reset history search text.
+            # (Note that this doesn't need to happen when working_index
+            #  changes, which is when we traverse the history. That's why we
+            #  don't do this in `self._text_changed`.)
+            self.history_search_text = None
+
+    @property
+    def cursor_position(self) -> int:
+        return self.__cursor_position
+
+    @cursor_position.setter
+    def cursor_position(self, value: int) -> None:
+        """
+        Setting cursor position.
+        """
+        assert isinstance(value, int)
+
+        # Ensure cursor position is within the size of the text.
+        if value > len(self.text):
+            value = len(self.text)
+        if value < 0:
+            value = 0
+
+        changed = self._set_cursor_position(value)
+
+        if changed:
+            self._cursor_position_changed()
+
+    @property
+    def working_index(self) -> int:
+        return self.__working_index
+
+    @working_index.setter
+    def working_index(self, value: int) -> None:
+        if self.__working_index != value:
+            self.__working_index = value
+            # Make sure to reset the cursor position, otherwise we end up in
+            # situations where the cursor position is out of the bounds of the
+            # text.
+            self.cursor_position = 0
+            self._text_changed()
+
+    def _text_changed(self) -> None:
+        # Remove any validation errors and complete state.
+        self.validation_error = None
+        self.validation_state = ValidationState.UNKNOWN
+        self.complete_state = None
+        self.yank_nth_arg_state = None
+        self.document_before_paste = None
+        self.selection_state = None
+        self.suggestion = None
+        self.preferred_column = None
+
+        # fire 'on_text_changed' event.
+        self.on_text_changed.fire()
+
+        # Input validation.
+        # (This happens on all change events, unlike auto completion, also when
+        # deleting text.)
+        if self.validator and self.validate_while_typing():
+            get_app().create_background_task(self._async_validator())
+
+    def _cursor_position_changed(self) -> None:
+        # Remove any complete state.
+        # (Input validation should only be undone when the cursor position
+        # changes.)
+        self.complete_state = None
+        self.yank_nth_arg_state = None
+        self.document_before_paste = None
+
+        # Unset preferred_column. (Will be set after the cursor movement, if
+        # required.)
+        self.preferred_column = None
+
+        # Note that the cursor position can change if we have a selection the
+        # new position of the cursor determines the end of the selection.
+
+        # fire 'on_cursor_position_changed' event.
+        self.on_cursor_position_changed.fire()
+
+    @property
+    def document(self) -> Document:
+        """
+        Return :class:`~prompt_toolkit.document.Document` instance from the
+        current text, cursor position and selection state.
+        """
+        return self._document_cache[
+            self.text, self.cursor_position, self.selection_state
+        ]
+
+    @document.setter
+    def document(self, value: Document) -> None:
+        """
+        Set :class:`~prompt_toolkit.document.Document` instance.
+
+        This will set both the text and cursor position at the same time, but
+        atomically. (Change events will be triggered only after both have been set.)
+        """
+        self.set_document(value)
+
+    def set_document(self, value: Document, bypass_readonly: bool = False) -> None:
+        """
+        Set :class:`~prompt_toolkit.document.Document` instance. Like the
+        ``document`` property, but accept an ``bypass_readonly`` argument.
+
+        :param bypass_readonly: When True, don't raise an
+                                :class:`.EditReadOnlyBuffer` exception, even
+                                when the buffer is read-only.
+
+        .. warning::
+
+            When this buffer is read-only and `bypass_readonly` was not passed,
+            the `EditReadOnlyBuffer` exception will be caught by the
+            `KeyProcessor` and is silently suppressed. This is important to
+            keep in mind when writing key bindings, because it won't do what
+            you expect, and there won't be a stack trace. Use try/finally
+            around this function if you need some cleanup code.
+        """
+        # Don't allow editing of read-only buffers.
+        if not bypass_readonly and self.read_only():
+            raise EditReadOnlyBuffer()
+
+        # Set text and cursor position first.
+        text_changed = self._set_text(value.text)
+        cursor_position_changed = self._set_cursor_position(value.cursor_position)
+
+        # Now handle change events. (We do this when text/cursor position is
+        # both set and consistent.)
+        if text_changed:
+            self._text_changed()
+            self.history_search_text = None
+
+        if cursor_position_changed:
+            self._cursor_position_changed()
+
+    @property
+    def is_returnable(self) -> bool:
+        """
+        True when there is something handling accept.
+        """
+        return bool(self.accept_handler)
+
+    # End of <getters/setters>
+
+    def save_to_undo_stack(self, clear_redo_stack: bool = True) -> None:
+        """
+        Safe current state (input text and cursor position), so that we can
+        restore it by calling undo.
+        """
+        # Safe if the text is different from the text at the top of the stack
+        # is different. If the text is the same, just update the cursor position.
+        if self._undo_stack and self._undo_stack[-1][0] == self.text:
+            self._undo_stack[-1] = (self._undo_stack[-1][0], self.cursor_position)
+        else:
+            self._undo_stack.append((self.text, self.cursor_position))
+
+        # Saving anything to the undo stack, clears the redo stack.
+        if clear_redo_stack:
+            self._redo_stack = []
+
+    def transform_lines(
+        self,
+        line_index_iterator: Iterable[int],
+        transform_callback: Callable[[str], str],
+    ) -> str:
+        """
+        Transforms the text on a range of lines.
+        When the iterator yield an index not in the range of lines that the
+        document contains, it skips them silently.
+
+        To uppercase some lines::
+
+            new_text = transform_lines(range(5,10), lambda text: text.upper())
+
+        :param line_index_iterator: Iterator of line numbers (int)
+        :param transform_callback: callable that takes the original text of a
+                                   line, and return the new text for this line.
+
+        :returns: The new text.
+        """
+        # Split lines
+        lines = self.text.split("\n")
+
+        # Apply transformation
+        for index in line_index_iterator:
+            try:
+                lines[index] = transform_callback(lines[index])
+            except IndexError:
+                pass
+
+        return "\n".join(lines)
+
+    def transform_current_line(self, transform_callback: Callable[[str], str]) -> None:
+        """
+        Apply the given transformation function to the current line.
+
+        :param transform_callback: callable that takes a string and return a new string.
+        """
+        document = self.document
+        a = document.cursor_position + document.get_start_of_line_position()
+        b = document.cursor_position + document.get_end_of_line_position()
+        self.text = (
+            document.text[:a]
+            + transform_callback(document.text[a:b])
+            + document.text[b:]
+        )
+
+    def transform_region(
+        self, from_: int, to: int, transform_callback: Callable[[str], str]
+    ) -> None:
+        """
+        Transform a part of the input string.
+
+        :param from_: (int) start position.
+        :param to: (int) end position.
+        :param transform_callback: Callable which accepts a string and returns
+            the transformed string.
+        """
+        assert from_ < to
+
+        self.text = "".join(
+            [
+                self.text[:from_]
+                + transform_callback(self.text[from_:to])
+                + self.text[to:]
+            ]
+        )
+
+    def cursor_left(self, count: int = 1) -> None:
+        self.cursor_position += self.document.get_cursor_left_position(count=count)
+
+    def cursor_right(self, count: int = 1) -> None:
+        self.cursor_position += self.document.get_cursor_right_position(count=count)
+
+    def cursor_up(self, count: int = 1) -> None:
+        """(for multiline edit). Move cursor to the previous line."""
+        original_column = self.preferred_column or self.document.cursor_position_col
+        self.cursor_position += self.document.get_cursor_up_position(
+            count=count, preferred_column=original_column
+        )
+
+        # Remember the original column for the next up/down movement.
+        self.preferred_column = original_column
+
+    def cursor_down(self, count: int = 1) -> None:
+        """(for multiline edit). Move cursor to the next line."""
+        original_column = self.preferred_column or self.document.cursor_position_col
+        self.cursor_position += self.document.get_cursor_down_position(
+            count=count, preferred_column=original_column
+        )
+
+        # Remember the original column for the next up/down movement.
+        self.preferred_column = original_column
+
+    def auto_up(
+        self, count: int = 1, go_to_start_of_line_if_history_changes: bool = False
+    ) -> None:
+        """
+        If we're not on the first line (of a multiline input) go a line up,
+        otherwise go back in history. (If nothing is selected.)
+        """
+        if self.complete_state:
+            self.complete_previous(count=count)
+        elif self.document.cursor_position_row > 0:
+            self.cursor_up(count=count)
+        elif not self.selection_state:
+            self.history_backward(count=count)
+
+            # Go to the start of the line?
+            if go_to_start_of_line_if_history_changes:
+                self.cursor_position += self.document.get_start_of_line_position()
+
+    def auto_down(
+        self, count: int = 1, go_to_start_of_line_if_history_changes: bool = False
+    ) -> None:
+        """
+        If we're not on the last line (of a multiline input) go a line down,
+        otherwise go forward in history. (If nothing is selected.)
+        """
+        if self.complete_state:
+            self.complete_next(count=count)
+        elif self.document.cursor_position_row < self.document.line_count - 1:
+            self.cursor_down(count=count)
+        elif not self.selection_state:
+            self.history_forward(count=count)
+
+            # Go to the start of the line?
+            if go_to_start_of_line_if_history_changes:
+                self.cursor_position += self.document.get_start_of_line_position()
+
+    def delete_before_cursor(self, count: int = 1) -> str:
+        """
+        Delete specified number of characters before cursor and return the
+        deleted text.
+        """
+        assert count >= 0
+        deleted = ""
+
+        if self.cursor_position > 0:
+            deleted = self.text[self.cursor_position - count : self.cursor_position]
+
+            new_text = (
+                self.text[: self.cursor_position - count]
+                + self.text[self.cursor_position :]
+            )
+            new_cursor_position = self.cursor_position - len(deleted)
+
+            # Set new Document atomically.
+            self.document = Document(new_text, new_cursor_position)
+
+        return deleted
+
+    def delete(self, count: int = 1) -> str:
+        """
+        Delete specified number of characters and Return the deleted text.
+        """
+        if self.cursor_position < len(self.text):
+            deleted = self.document.text_after_cursor[:count]
+            self.text = (
+                self.text[: self.cursor_position]
+                + self.text[self.cursor_position + len(deleted) :]
+            )
+            return deleted
+        else:
+            return ""
+
+    def join_next_line(self, separator: str = " ") -> None:
+        """
+        Join the next line to the current one by deleting the line ending after
+        the current line.
+        """
+        if not self.document.on_last_line:
+            self.cursor_position += self.document.get_end_of_line_position()
+            self.delete()
+
+            # Remove spaces.
+            self.text = (
+                self.document.text_before_cursor
+                + separator
+                + self.document.text_after_cursor.lstrip(" ")
+            )
+
+    def join_selected_lines(self, separator: str = " ") -> None:
+        """
+        Join the selected lines.
+        """
+        assert self.selection_state
+
+        # Get lines.
+        from_, to = sorted(
+            [self.cursor_position, self.selection_state.original_cursor_position]
+        )
+
+        before = self.text[:from_]
+        lines = self.text[from_:to].splitlines()
+        after = self.text[to:]
+
+        # Replace leading spaces with just one space.
+        lines = [l.lstrip(" ") + separator for l in lines]
+
+        # Set new document.
+        self.document = Document(
+            text=before + "".join(lines) + after,
+            cursor_position=len(before + "".join(lines[:-1])) - 1,
+        )
+
+    def swap_characters_before_cursor(self) -> None:
+        """
+        Swap the last two characters before the cursor.
+        """
+        pos = self.cursor_position
+
+        if pos >= 2:
+            a = self.text[pos - 2]
+            b = self.text[pos - 1]
+
+            self.text = self.text[: pos - 2] + b + a + self.text[pos:]
+
+    def go_to_history(self, index: int) -> None:
+        """
+        Go to this item in the history.
+        """
+        if index < len(self._working_lines):
+            self.working_index = index
+            self.cursor_position = len(self.text)
+
+    def complete_next(self, count: int = 1, disable_wrap_around: bool = False) -> None:
+        """
+        Browse to the next completions.
+        (Does nothing if there are no completion.)
+        """
+        index: Optional[int]
+
+        if self.complete_state:
+            completions_count = len(self.complete_state.completions)
+
+            if self.complete_state.complete_index is None:
+                index = 0
+            elif self.complete_state.complete_index == completions_count - 1:
+                index = None
+
+                if disable_wrap_around:
+                    return
+            else:
+                index = min(
+                    completions_count - 1, self.complete_state.complete_index + count
+                )
+            self.go_to_completion(index)
+
+    def complete_previous(
+        self, count: int = 1, disable_wrap_around: bool = False
+    ) -> None:
+        """
+        Browse to the previous completions.
+        (Does nothing if there are no completion.)
+        """
+        index: Optional[int]
+
+        if self.complete_state:
+            if self.complete_state.complete_index == 0:
+                index = None
+
+                if disable_wrap_around:
+                    return
+            elif self.complete_state.complete_index is None:
+                index = len(self.complete_state.completions) - 1
+            else:
+                index = max(0, self.complete_state.complete_index - count)
+
+            self.go_to_completion(index)
+
+    def cancel_completion(self) -> None:
+        """
+        Cancel completion, go back to the original text.
+        """
+        if self.complete_state:
+            self.go_to_completion(None)
+            self.complete_state = None
+
+    def _set_completions(self, completions: List[Completion]) -> CompletionState:
+        """
+        Start completions. (Generate list of completions and initialize.)
+
+        By default, no completion will be selected.
+        """
+        self.complete_state = CompletionState(
+            original_document=self.document, completions=completions
+        )
+
+        # Trigger event. This should eventually invalidate the layout.
+        self.on_completions_changed.fire()
+
+        return self.complete_state
+
+    def start_history_lines_completion(self) -> None:
+        """
+        Start a completion based on all the other lines in the document and the
+        history.
+        """
+        found_completions: Set[str] = set()
+        completions = []
+
+        # For every line of the whole history, find matches with the current line.
+        current_line = self.document.current_line_before_cursor.lstrip()
+
+        for i, string in enumerate(self._working_lines):
+            for j, l in enumerate(string.split("\n")):
+                l = l.strip()
+                if l and l.startswith(current_line):
+                    # When a new line has been found.
+                    if l not in found_completions:
+                        found_completions.add(l)
+
+                        # Create completion.
+                        if i == self.working_index:
+                            display_meta = "Current, line %s" % (j + 1)
+                        else:
+                            display_meta = f"History {i + 1}, line {j + 1}"
+
+                        completions.append(
+                            Completion(
+                                text=l,
+                                start_position=-len(current_line),
+                                display_meta=display_meta,
+                            )
+                        )
+
+        self._set_completions(completions=completions[::-1])
+        self.go_to_completion(0)
+
+    def go_to_completion(self, index: Optional[int]) -> None:
+        """
+        Select a completion from the list of current completions.
+        """
+        assert self.complete_state
+
+        # Set new completion
+        state = self.complete_state
+        state.go_to_index(index)
+
+        # Set text/cursor position
+        new_text, new_cursor_position = state.new_text_and_position()
+        self.document = Document(new_text, new_cursor_position)
+
+        # (changing text/cursor position will unset complete_state.)
+        self.complete_state = state
+
+    def apply_completion(self, completion: Completion) -> None:
+        """
+        Insert a given completion.
+        """
+        # If there was already a completion active, cancel that one.
+        if self.complete_state:
+            self.go_to_completion(None)
+        self.complete_state = None
+
+        # Insert text from the given completion.
+        self.delete_before_cursor(-completion.start_position)
+        self.insert_text(completion.text)
+
+    def _set_history_search(self) -> None:
+        """
+        Set `history_search_text`.
+        (The text before the cursor will be used for filtering the history.)
+        """
+        if self.enable_history_search():
+            if self.history_search_text is None:
+                self.history_search_text = self.document.text_before_cursor
+        else:
+            self.history_search_text = None
+
+    def _history_matches(self, i: int) -> bool:
+        """
+        True when the current entry matches the history search.
+        (when we don't have history search, it's also True.)
+        """
+        return self.history_search_text is None or self._working_lines[i].startswith(
+            self.history_search_text
+        )
+
+    def history_forward(self, count: int = 1) -> None:
+        """
+        Move forwards through the history.
+
+        :param count: Amount of items to move forward.
+        """
+        self._set_history_search()
+
+        # Go forward in history.
+        found_something = False
+
+        for i in range(self.working_index + 1, len(self._working_lines)):
+            if self._history_matches(i):
+                self.working_index = i
+                count -= 1
+                found_something = True
+            if count == 0:
+                break
+
+        # If we found an entry, move cursor to the end of the first line.
+        if found_something:
+            self.cursor_position = 0
+            self.cursor_position += self.document.get_end_of_line_position()
+
+    def history_backward(self, count: int = 1) -> None:
+        """
+        Move backwards through history.
+        """
+        self._set_history_search()
+
+        # Go back in history.
+        found_something = False
+
+        for i in range(self.working_index - 1, -1, -1):
+            if self._history_matches(i):
+                self.working_index = i
+                count -= 1
+                found_something = True
+            if count == 0:
+                break
+
+        # If we move to another entry, move cursor to the end of the line.
+        if found_something:
+            self.cursor_position = len(self.text)
+
+    def yank_nth_arg(
+        self, n: Optional[int] = None, _yank_last_arg: bool = False
+    ) -> None:
+        """
+        Pick nth word from previous history entry (depending on current
+        `yank_nth_arg_state`) and insert it at current position. Rotate through
+        history if called repeatedly. If no `n` has been given, take the first
+        argument. (The second word.)
+
+        :param n: (None or int), The index of the word from the previous line
+            to take.
+        """
+        assert n is None or isinstance(n, int)
+        history_strings = self.history.get_strings()
+
+        if not len(history_strings):
+            return
+
+        # Make sure we have a `YankNthArgState`.
+        if self.yank_nth_arg_state is None:
+            state = YankNthArgState(n=-1 if _yank_last_arg else 1)
+        else:
+            state = self.yank_nth_arg_state
+
+        if n is not None:
+            state.n = n
+
+        # Get new history position.
+        new_pos = state.history_position - 1
+        if -new_pos > len(history_strings):
+            new_pos = -1
+
+        # Take argument from line.
+        line = history_strings[new_pos]
+
+        words = [w.strip() for w in _QUOTED_WORDS_RE.split(line)]
+        words = [w for w in words if w]
+        try:
+            word = words[state.n]
+        except IndexError:
+            word = ""
+
+        # Insert new argument.
+        if state.previous_inserted_word:
+            self.delete_before_cursor(len(state.previous_inserted_word))
+        self.insert_text(word)
+
+        # Save state again for next completion. (Note that the 'insert'
+        # operation from above clears `self.yank_nth_arg_state`.)
+        state.previous_inserted_word = word
+        state.history_position = new_pos
+        self.yank_nth_arg_state = state
+
+    def yank_last_arg(self, n: Optional[int] = None) -> None:
+        """
+        Like `yank_nth_arg`, but if no argument has been given, yank the last
+        word by default.
+        """
+        self.yank_nth_arg(n=n, _yank_last_arg=True)
+
+    def start_selection(
+        self, selection_type: SelectionType = SelectionType.CHARACTERS
+    ) -> None:
+        """
+        Take the current cursor position as the start of this selection.
+        """
+        self.selection_state = SelectionState(self.cursor_position, selection_type)
+
+    def copy_selection(self, _cut: bool = False) -> ClipboardData:
+        """
+        Copy selected text and return :class:`.ClipboardData` instance.
+
+        Notice that this doesn't store the copied data on the clipboard yet.
+        You can store it like this:
+
+        .. code:: python
+
+            data = buffer.copy_selection()
+            get_app().clipboard.set_data(data)
+        """
+        new_document, clipboard_data = self.document.cut_selection()
+        if _cut:
+            self.document = new_document
+
+        self.selection_state = None
+        return clipboard_data
+
+    def cut_selection(self) -> ClipboardData:
+        """
+        Delete selected text and return :class:`.ClipboardData` instance.
+        """
+        return self.copy_selection(_cut=True)
+
+    def paste_clipboard_data(
+        self,
+        data: ClipboardData,
+        paste_mode: PasteMode = PasteMode.EMACS,
+        count: int = 1,
+    ) -> None:
+        """
+        Insert the data from the clipboard.
+        """
+        assert isinstance(data, ClipboardData)
+        assert paste_mode in (PasteMode.VI_BEFORE, PasteMode.VI_AFTER, PasteMode.EMACS)
+
+        original_document = self.document
+        self.document = self.document.paste_clipboard_data(
+            data, paste_mode=paste_mode, count=count
+        )
+
+        # Remember original document. This assignment should come at the end,
+        # because assigning to 'document' will erase it.
+        self.document_before_paste = original_document
+
+    def newline(self, copy_margin: bool = True) -> None:
+        """
+        Insert a line ending at the current position.
+        """
+        if copy_margin:
+            self.insert_text("\n" + self.document.leading_whitespace_in_current_line)
+        else:
+            self.insert_text("\n")
+
+    def insert_line_above(self, copy_margin: bool = True) -> None:
+        """
+        Insert a new line above the current one.
+        """
+        if copy_margin:
+            insert = self.document.leading_whitespace_in_current_line + "\n"
+        else:
+            insert = "\n"
+
+        self.cursor_position += self.document.get_start_of_line_position()
+        self.insert_text(insert)
+        self.cursor_position -= 1
+
+    def insert_line_below(self, copy_margin: bool = True) -> None:
+        """
+        Insert a new line below the current one.
+        """
+        if copy_margin:
+            insert = "\n" + self.document.leading_whitespace_in_current_line
+        else:
+            insert = "\n"
+
+        self.cursor_position += self.document.get_end_of_line_position()
+        self.insert_text(insert)
+
+    def insert_text(
+        self,
+        data: str,
+        overwrite: bool = False,
+        move_cursor: bool = True,
+        fire_event: bool = True,
+    ) -> None:
+        """
+        Insert characters at cursor position.
+
+        :param fire_event: Fire `on_text_insert` event. This is mainly used to
+            trigger autocompletion while typing.
+        """
+        # Original text & cursor position.
+        otext = self.text
+        ocpos = self.cursor_position
+
+        # In insert/text mode.
+        if overwrite:
+            # Don't overwrite the newline itself. Just before the line ending,
+            # it should act like insert mode.
+            overwritten_text = otext[ocpos : ocpos + len(data)]
+            if "\n" in overwritten_text:
+                overwritten_text = overwritten_text[: overwritten_text.find("\n")]
+
+            text = otext[:ocpos] + data + otext[ocpos + len(overwritten_text) :]
+        else:
+            text = otext[:ocpos] + data + otext[ocpos:]
+
+        if move_cursor:
+            cpos = self.cursor_position + len(data)
+        else:
+            cpos = self.cursor_position
+
+        # Set new document.
+        # (Set text and cursor position at the same time. Otherwise, setting
+        # the text will fire a change event before the cursor position has been
+        # set. It works better to have this atomic.)
+        self.document = Document(text, cpos)
+
+        # Fire 'on_text_insert' event.
+        if fire_event:  # XXX: rename to `start_complete`.
+            self.on_text_insert.fire()
+
+            # Only complete when "complete_while_typing" is enabled.
+            if self.completer and self.complete_while_typing():
+                get_app().create_background_task(self._async_completer())
+
+            # Call auto_suggest.
+            if self.auto_suggest:
+                get_app().create_background_task(self._async_suggester())
+
+    def undo(self) -> None:
+        # Pop from the undo-stack until we find a text that if different from
+        # the current text. (The current logic of `save_to_undo_stack` will
+        # cause that the top of the undo stack is usually the same as the
+        # current text, so in that case we have to pop twice.)
+        while self._undo_stack:
+            text, pos = self._undo_stack.pop()
+
+            if text != self.text:
+                # Push current text to redo stack.
+                self._redo_stack.append((self.text, self.cursor_position))
+
+                # Set new text/cursor_position.
+                self.document = Document(text, cursor_position=pos)
+                break
+
+    def redo(self) -> None:
+        if self._redo_stack:
+            # Copy current state on undo stack.
+            self.save_to_undo_stack(clear_redo_stack=False)
+
+            # Pop state from redo stack.
+            text, pos = self._redo_stack.pop()
+            self.document = Document(text, cursor_position=pos)
+
+    def validate(self, set_cursor: bool = False) -> bool:
+        """
+        Returns `True` if valid.
+
+        :param set_cursor: Set the cursor position, if an error was found.
+        """
+        # Don't call the validator again, if it was already called for the
+        # current input.
+        if self.validation_state != ValidationState.UNKNOWN:
+            return self.validation_state == ValidationState.VALID
+
+        # Call validator.
+        if self.validator:
+            try:
+                self.validator.validate(self.document)
+            except ValidationError as e:
+                # Set cursor position (don't allow invalid values.)
+                if set_cursor:
+                    self.cursor_position = min(
+                        max(0, e.cursor_position), len(self.text)
+                    )
+
+                self.validation_state = ValidationState.INVALID
+                self.validation_error = e
+                return False
+
+        # Handle validation result.
+        self.validation_state = ValidationState.VALID
+        self.validation_error = None
+        return True
+
+    async def _validate_async(self) -> None:
+        """
+        Asynchronous version of `validate()`.
+        This one doesn't set the cursor position.
+
+        We have both variants, because a synchronous version is required.
+        Handling the ENTER key needs to be completely synchronous, otherwise
+        stuff like type-ahead is going to give very weird results. (People
+        could type input while the ENTER key is still processed.)
+
+        An asynchronous version is required if we have `validate_while_typing`
+        enabled.
+        """
+        while True:
+            # Don't call the validator again, if it was already called for the
+            # current input.
+            if self.validation_state != ValidationState.UNKNOWN:
+                return
+
+            # Call validator.
+            error = None
+            document = self.document
+
+            if self.validator:
+                try:
+                    await self.validator.validate_async(self.document)
+                except ValidationError as e:
+                    error = e
+
+                # If the document changed during the validation, try again.
+                if self.document != document:
+                    continue
+
+            # Handle validation result.
+            if error:
+                self.validation_state = ValidationState.INVALID
+            else:
+                self.validation_state = ValidationState.VALID
+
+            self.validation_error = error
+            get_app().invalidate()  # Trigger redraw (display error).
+
+    def append_to_history(self) -> None:
+        """
+        Append the current input to the history.
+        """
+        # Save at the tail of the history. (But don't if the last entry the
+        # history is already the same.)
+        if self.text:
+            history_strings = self.history.get_strings()
+            if not len(history_strings) or history_strings[-1] != self.text:
+                self.history.append_string(self.text)
+
+    def _search(
+        self,
+        search_state: SearchState,
+        include_current_position: bool = False,
+        count: int = 1,
+    ) -> Optional[Tuple[int, int]]:
+        """
+        Execute search. Return (working_index, cursor_position) tuple when this
+        search is applied. Returns `None` when this text cannot be found.
+        """
+        assert count > 0
+
+        text = search_state.text
+        direction = search_state.direction
+        ignore_case = search_state.ignore_case()
+
+        def search_once(
+            working_index: int, document: Document
+        ) -> Optional[Tuple[int, Document]]:
+            """
+            Do search one time.
+            Return (working_index, document) or `None`
+            """
+            if direction == SearchDirection.FORWARD:
+                # Try find at the current input.
+                new_index = document.find(
+                    text,
+                    include_current_position=include_current_position,
+                    ignore_case=ignore_case,
+                )
+
+                if new_index is not None:
+                    return (
+                        working_index,
+                        Document(document.text, document.cursor_position + new_index),
+                    )
+                else:
+                    # No match, go forward in the history. (Include len+1 to wrap around.)
+                    # (Here we should always include all cursor positions, because
+                    # it's a different line.)
+                    for i in range(working_index + 1, len(self._working_lines) + 1):
+                        i %= len(self._working_lines)
+
+                        document = Document(self._working_lines[i], 0)
+                        new_index = document.find(
+                            text, include_current_position=True, ignore_case=ignore_case
+                        )
+                        if new_index is not None:
+                            return (i, Document(document.text, new_index))
+            else:
+                # Try find at the current input.
+                new_index = document.find_backwards(text, ignore_case=ignore_case)
+
+                if new_index is not None:
+                    return (
+                        working_index,
+                        Document(document.text, document.cursor_position + new_index),
+                    )
+                else:
+                    # No match, go back in the history. (Include -1 to wrap around.)
+                    for i in range(working_index - 1, -2, -1):
+                        i %= len(self._working_lines)
+
+                        document = Document(
+                            self._working_lines[i], len(self._working_lines[i])
+                        )
+                        new_index = document.find_backwards(
+                            text, ignore_case=ignore_case
+                        )
+                        if new_index is not None:
+                            return (
+                                i,
+                                Document(document.text, len(document.text) + new_index),
+                            )
+            return None
+
+        # Do 'count' search iterations.
+        working_index = self.working_index
+        document = self.document
+        for _ in range(count):
+            result = search_once(working_index, document)
+            if result is None:
+                return None  # Nothing found.
+            else:
+                working_index, document = result
+
+        return (working_index, document.cursor_position)
+
+    def document_for_search(self, search_state: SearchState) -> Document:
+        """
+        Return a :class:`~prompt_toolkit.document.Document` instance that has
+        the text/cursor position for this search, if we would apply it. This
+        will be used in the
+        :class:`~prompt_toolkit.layout.BufferControl` to display feedback while
+        searching.
+        """
+        search_result = self._search(search_state, include_current_position=True)
+
+        if search_result is None:
+            return self.document
+        else:
+            working_index, cursor_position = search_result
+
+            # Keep selection, when `working_index` was not changed.
+            if working_index == self.working_index:
+                selection = self.selection_state
+            else:
+                selection = None
+
+            return Document(
+                self._working_lines[working_index], cursor_position, selection=selection
+            )
+
+    def get_search_position(
+        self,
+        search_state: SearchState,
+        include_current_position: bool = True,
+        count: int = 1,
+    ) -> int:
+        """
+        Get the cursor position for this search.
+        (This operation won't change the `working_index`. It's won't go through
+        the history. Vi text objects can't span multiple items.)
+        """
+        search_result = self._search(
+            search_state, include_current_position=include_current_position, count=count
+        )
+
+        if search_result is None:
+            return self.cursor_position
+        else:
+            working_index, cursor_position = search_result
+            return cursor_position
+
+    def apply_search(
+        self,
+        search_state: SearchState,
+        include_current_position: bool = True,
+        count: int = 1,
+    ) -> None:
+        """
+        Apply search. If something is found, set `working_index` and
+        `cursor_position`.
+        """
+        search_result = self._search(
+            search_state, include_current_position=include_current_position, count=count
+        )
+
+        if search_result is not None:
+            working_index, cursor_position = search_result
+            self.working_index = working_index
+            self.cursor_position = cursor_position
+
+    def exit_selection(self) -> None:
+        self.selection_state = None
+
+    def _editor_simple_tempfile(self) -> Tuple[str, Callable[[], None]]:
+        """
+        Simple (file) tempfile implementation.
+        Return (tempfile, cleanup_func).
+        """
+        suffix = to_str(self.tempfile_suffix)
+        descriptor, filename = tempfile.mkstemp(suffix)
+
+        os.write(descriptor, self.text.encode("utf-8"))
+        os.close(descriptor)
+
+        def cleanup() -> None:
+            os.unlink(filename)
+
+        return filename, cleanup
+
+    def _editor_complex_tempfile(self) -> Tuple[str, Callable[[], None]]:
+        # Complex (directory) tempfile implementation.
+        headtail = to_str(self.tempfile)
+        if not headtail:
+            # Revert to simple case.
+            return self._editor_simple_tempfile()
+        headtail = str(headtail)
+
+        # Try to make according to tempfile logic.
+        head, tail = os.path.split(headtail)
+        if os.path.isabs(head):
+            head = head[1:]
+
+        dirpath = tempfile.mkdtemp()
+        if head:
+            dirpath = os.path.join(dirpath, head)
+        # Assume there is no issue creating dirs in this temp dir.
+        os.makedirs(dirpath)
+
+        # Open the filename and write current text.
+        filename = os.path.join(dirpath, tail)
+        with open(filename, "w", encoding="utf-8") as fh:
+            fh.write(self.text)
+
+        def cleanup() -> None:
+            shutil.rmtree(dirpath)
+
+        return filename, cleanup
+
+    def open_in_editor(self, validate_and_handle: bool = False) -> "asyncio.Task[None]":
+        """
+        Open code in editor.
+
+        This returns a future, and runs in a thread executor.
+        """
+        if self.read_only():
+            raise EditReadOnlyBuffer()
+
+        # Write current text to temporary file
+        if self.tempfile:
+            filename, cleanup_func = self._editor_complex_tempfile()
+        else:
+            filename, cleanup_func = self._editor_simple_tempfile()
+
+        async def run() -> None:
+            try:
+                # Open in editor
+                # (We need to use `run_in_terminal`, because not all editors go to
+                # the alternate screen buffer, and some could influence the cursor
+                # position.)
+                succes = await run_in_terminal(
+                    lambda: self._open_file_in_editor(filename), in_executor=True
+                )
+
+                # Read content again.
+                if succes:
+                    with open(filename, "rb") as f:
+                        text = f.read().decode("utf-8")
+
+                        # Drop trailing newline. (Editors are supposed to add it at the
+                        # end, but we don't need it.)
+                        if text.endswith("\n"):
+                            text = text[:-1]
+
+                        self.document = Document(text=text, cursor_position=len(text))
+
+                    # Accept the input.
+                    if validate_and_handle:
+                        self.validate_and_handle()
+
+            finally:
+                # Clean up temp dir/file.
+                cleanup_func()
+
+        return get_app().create_background_task(run())
+
+    def _open_file_in_editor(self, filename: str) -> bool:
+        """
+        Call editor executable.
+
+        Return True when we received a zero return code.
+        """
+        # If the 'VISUAL' or 'EDITOR' environment variable has been set, use that.
+        # Otherwise, fall back to the first available editor that we can find.
+        visual = os.environ.get("VISUAL")
+        editor = os.environ.get("EDITOR")
+
+        editors = [
+            visual,
+            editor,
+            # Order of preference.
+            "/usr/bin/editor",
+            "/usr/bin/nano",
+            "/usr/bin/pico",
+            "/usr/bin/vi",
+            "/usr/bin/emacs",
+        ]
+
+        for e in editors:
+            if e:
+                try:
+                    # Use 'shlex.split()', because $VISUAL can contain spaces
+                    # and quotes.
+                    returncode = subprocess.call(shlex.split(e) + [filename])
+                    return returncode == 0
+
+                except OSError:
+                    # Executable does not exist, try the next one.
+                    pass
+
+        return False
+
+    def start_completion(
+        self,
+        select_first: bool = False,
+        select_last: bool = False,
+        insert_common_part: bool = False,
+        complete_event: Optional[CompleteEvent] = None,
+    ) -> None:
+        """
+        Start asynchronous autocompletion of this buffer.
+        (This will do nothing if a previous completion was still in progress.)
+        """
+        # Only one of these options can be selected.
+        assert select_first + select_last + insert_common_part <= 1
+
+        get_app().create_background_task(
+            self._async_completer(
+                select_first=select_first,
+                select_last=select_last,
+                insert_common_part=insert_common_part,
+                complete_event=complete_event
+                or CompleteEvent(completion_requested=True),
+            )
+        )
+
+    def _create_completer_coroutine(self) -> Callable[..., Coroutine[Any, Any, None]]:
+        """
+        Create function for asynchronous autocompletion.
+
+        (This consumes the asynchronous completer generator, which possibly
+        runs the completion algorithm in another thread.)
+        """
+
+        def completion_does_nothing(document: Document, completion: Completion) -> bool:
+            """
+            Return `True` if applying this completion doesn't have any effect.
+            (When it doesn't insert any new text.
+            """
+            text_before_cursor = document.text_before_cursor
+            replaced_text = text_before_cursor[
+                len(text_before_cursor) + completion.start_position :
+            ]
+            return replaced_text == completion.text
+
+        @_only_one_at_a_time
+        async def async_completer(
+            select_first: bool = False,
+            select_last: bool = False,
+            insert_common_part: bool = False,
+            complete_event: Optional[CompleteEvent] = None,
+        ) -> None:
+
+            document = self.document
+            complete_event = complete_event or CompleteEvent(text_inserted=True)
+
+            # Don't complete when we already have completions.
+            if self.complete_state or not self.completer:
+                return
+
+            # Create an empty CompletionState.
+            complete_state = CompletionState(original_document=self.document)
+            self.complete_state = complete_state
+
+            def proceed() -> bool:
+                """Keep retrieving completions. Input text has not yet changed
+                while generating completions."""
+                return self.complete_state == complete_state
+
+            refresh_needed = asyncio.Event()
+
+            async def refresh_while_loading() -> None:
+                """Background loop to refresh the UI at most 3 times a second
+                while the completion are loading. Calling
+                `on_completions_changed.fire()` for every completion that we
+                receive is too expensive when there are many completions. (We
+                could tune `Application.max_render_postpone_time` and
+                `Application.min_redraw_interval`, but having this here is a
+                better approach.)
+                """
+                while True:
+                    self.on_completions_changed.fire()
+                    refresh_needed.clear()
+                    await asyncio.sleep(0.3)
+                    await refresh_needed.wait()
+
+            refresh_task = asyncio.ensure_future(refresh_while_loading())
+            try:
+                # Load.
+                async with aclosing(
+                    self.completer.get_completions_async(document, complete_event)
+                ) as async_generator:
+                    async for completion in async_generator:
+                        complete_state.completions.append(completion)
+                        refresh_needed.set()
+
+                        # If the input text changes, abort.
+                        if not proceed():
+                            break
+            finally:
+                refresh_task.cancel()
+
+                # Refresh one final time after we got everything.
+                self.on_completions_changed.fire()
+
+            completions = complete_state.completions
+
+            # When there is only one completion, which has nothing to add, ignore it.
+            if len(completions) == 1 and completion_does_nothing(
+                document, completions[0]
+            ):
+                del completions[:]
+
+            # Set completions if the text was not yet changed.
+            if proceed():
+                # When no completions were found, or when the user selected
+                # already a completion by using the arrow keys, don't do anything.
+                if (
+                    not self.complete_state
+                    or self.complete_state.complete_index is not None
+                ):
+                    return
+
+                # When there are no completions, reset completion state anyway.
+                if not completions:
+                    self.complete_state = None
+                    # Render the ui if the completion menu was shown
+                    # it is needed especially if there is one completion and it was deleted.
+                    self.on_completions_changed.fire()
+                    return
+
+                # Select first/last or insert common part, depending on the key
+                # binding. (For this we have to wait until all completions are
+                # loaded.)
+
+                if select_first:
+                    self.go_to_completion(0)
+
+                elif select_last:
+                    self.go_to_completion(len(completions) - 1)
+
+                elif insert_common_part:
+                    common_part = get_common_complete_suffix(document, completions)
+                    if common_part:
+                        # Insert the common part, update completions.
+                        self.insert_text(common_part)
+                        if len(completions) > 1:
+                            # (Don't call `async_completer` again, but
+                            # recalculate completions. See:
+                            # https://github.com/ipython/ipython/issues/9658)
+                            completions[:] = [
+                                c.new_completion_from_position(len(common_part))
+                                for c in completions
+                            ]
+
+                            self._set_completions(completions=completions)
+                        else:
+                            self.complete_state = None
+                    else:
+                        # When we were asked to insert the "common"
+                        # prefix, but there was no common suffix but
+                        # still exactly one match, then select the
+                        # first. (It could be that we have a completion
+                        # which does * expansion, like '*.py', with
+                        # exactly one match.)
+                        if len(completions) == 1:
+                            self.go_to_completion(0)
+
+            else:
+                # If the last operation was an insert, (not a delete), restart
+                # the completion coroutine.
+
+                if self.document.text_before_cursor == document.text_before_cursor:
+                    return  # Nothing changed.
+
+                if self.document.text_before_cursor.startswith(
+                    document.text_before_cursor
+                ):
+                    raise _Retry
+
+        return async_completer
+
+    def _create_auto_suggest_coroutine(self) -> Callable[[], Coroutine[Any, Any, None]]:
+        """
+        Create function for asynchronous auto suggestion.
+        (This can be in another thread.)
+        """
+
+        @_only_one_at_a_time
+        async def async_suggestor() -> None:
+            document = self.document
+
+            # Don't suggest when we already have a suggestion.
+            if self.suggestion or not self.auto_suggest:
+                return
+
+            suggestion = await self.auto_suggest.get_suggestion_async(self, document)
+
+            # Set suggestion only if the text was not yet changed.
+            if self.document == document:
+                # Set suggestion and redraw interface.
+                self.suggestion = suggestion
+                self.on_suggestion_set.fire()
+            else:
+                # Otherwise, restart thread.
+                raise _Retry
+
+        return async_suggestor
+
+    def _create_auto_validate_coroutine(
+        self,
+    ) -> Callable[[], Coroutine[Any, Any, None]]:
+        """
+        Create a function for asynchronous validation while typing.
+        (This can be in another thread.)
+        """
+
+        @_only_one_at_a_time
+        async def async_validator() -> None:
+            await self._validate_async()
+
+        return async_validator
+
+    def validate_and_handle(self) -> None:
+        """
+        Validate buffer and handle the accept action.
+        """
+        valid = self.validate(set_cursor=True)
+
+        # When the validation succeeded, accept the input.
+        if valid:
+            if self.accept_handler:
+                keep_text = self.accept_handler(self)
+            else:
+                keep_text = False
+
+            self.append_to_history()
+
+            if not keep_text:
+                self.reset()
+
+
+_T = TypeVar("_T", bound=Callable[..., Awaitable[None]])
+
+
+def _only_one_at_a_time(coroutine: _T) -> _T:
+    """
+    Decorator that only starts the coroutine only if the previous call has
+    finished. (Used to make sure that we have only one autocompleter, auto
+    suggestor and validator running at a time.)
+
+    When the coroutine raises `_Retry`, it is restarted.
+    """
+    running = False
+
+    @wraps(coroutine)
+    async def new_coroutine(*a: Any, **kw: Any) -> Any:
+        nonlocal running
+
+        # Don't start a new function, if the previous is still in progress.
+        if running:
+            return
+
+        running = True
+
+        try:
+            while True:
+                try:
+                    await coroutine(*a, **kw)
+                except _Retry:
+                    continue
+                else:
+                    return None
+        finally:
+            running = False
+
+    return cast(_T, new_coroutine)
+
+
+class _Retry(Exception):
+    "Retry in `_only_one_at_a_time`."
+
+
+def indent(buffer: Buffer, from_row: int, to_row: int, count: int = 1) -> None:
+    """
+    Indent text of a :class:`.Buffer` object.
+    """
+    current_row = buffer.document.cursor_position_row
+    line_range = range(from_row, to_row)
+
+    # Apply transformation.
+    new_text = buffer.transform_lines(line_range, lambda l: "    " * count + l)
+    buffer.document = Document(
+        new_text, Document(new_text).translate_row_col_to_index(current_row, 0)
+    )
+
+    # Go to the start of the line.
+    buffer.cursor_position += buffer.document.get_start_of_line_position(
+        after_whitespace=True
+    )
+
+
+def unindent(buffer: Buffer, from_row: int, to_row: int, count: int = 1) -> None:
+    """
+    Unindent text of a :class:`.Buffer` object.
+    """
+    current_row = buffer.document.cursor_position_row
+    line_range = range(from_row, to_row)
+
+    def transform(text: str) -> str:
+        remove = "    " * count
+        if text.startswith(remove):
+            return text[len(remove) :]
+        else:
+            return text.lstrip()
+
+    # Apply transformation.
+    new_text = buffer.transform_lines(line_range, transform)
+    buffer.document = Document(
+        new_text, Document(new_text).translate_row_col_to_index(current_row, 0)
+    )
+
+    # Go to the start of the line.
+    buffer.cursor_position += buffer.document.get_start_of_line_position(
+        after_whitespace=True
+    )
+
+
+def reshape_text(buffer: Buffer, from_row: int, to_row: int) -> None:
+    """
+    Reformat text, taking the width into account.
+    `to_row` is included.
+    (Vi 'gq' operator.)
+    """
+    lines = buffer.text.splitlines(True)
+    lines_before = lines[:from_row]
+    lines_after = lines[to_row + 1 :]
+    lines_to_reformat = lines[from_row : to_row + 1]
+
+    if lines_to_reformat:
+        # Take indentation from the first line.
+        match = re.search(r"^\s*", lines_to_reformat[0])
+        length = match.end() if match else 0  # `match` can't be None, actually.
+
+        indent = lines_to_reformat[0][:length].replace("\n", "")
+
+        # Now, take all the 'words' from the lines to be reshaped.
+        words = "".join(lines_to_reformat).split()
+
+        # And reshape.
+        width = (buffer.text_width or 80) - len(indent)
+        reshaped_text = [indent]
+        current_width = 0
+        for w in words:
+            if current_width:
+                if len(w) + current_width + 1 > width:
+                    reshaped_text.append("\n")
+                    reshaped_text.append(indent)
+                    current_width = 0
+                else:
+                    reshaped_text.append(" ")
+                    current_width += 1
+
+            reshaped_text.append(w)
+            current_width += len(w)
+
+        if reshaped_text[-1] != "\n":
+            reshaped_text.append("\n")
+
+        # Apply result.
+        buffer.document = Document(
+            text="".join(lines_before + reshaped_text + lines_after),
+            cursor_position=len("".join(lines_before + reshaped_text)),
+        )
diff --git a/src/prompt_toolkit/cache.py b/src/prompt_toolkit/cache.py
new file mode 100644
index 0000000..e5e9d70
--- /dev/null
+++ b/src/prompt_toolkit/cache.py
@@ -0,0 +1,125 @@
+from collections import deque
+from functools import wraps
+from typing import Any, Callable, Deque, Dict, Generic, Hashable, Tuple, TypeVar, cast
+
+__all__ = [
+    "SimpleCache",
+    "FastDictCache",
+    "memoized",
+]
+
+_T = TypeVar("_T", bound=Hashable)
+_U = TypeVar("_U")
+
+
+class SimpleCache(Generic[_T, _U]):
+    """
+    Very simple cache that discards the oldest item when the cache size is
+    exceeded.
+
+    :param maxsize: Maximum size of the cache. (Don't make it too big.)
+    """
+
+    def __init__(self, maxsize: int = 8) -> None:
+        assert maxsize > 0
+
+        self._data: Dict[_T, _U] = {}
+        self._keys: Deque[_T] = deque()
+        self.maxsize: int = maxsize
+
+    def get(self, key: _T, getter_func: Callable[[], _U]) -> _U:
+        """
+        Get object from the cache.
+        If not found, call `getter_func` to resolve it, and put that on the top
+        of the cache instead.
+        """
+        # Look in cache first.
+        try:
+            return self._data[key]
+        except KeyError:
+            # Not found? Get it.
+            value = getter_func()
+            self._data[key] = value
+            self._keys.append(key)
+
+            # Remove the oldest key when the size is exceeded.
+            if len(self._data) > self.maxsize:
+                key_to_remove = self._keys.popleft()
+                if key_to_remove in self._data:
+                    del self._data[key_to_remove]
+
+            return value
+
+    def clear(self) -> None:
+        "Clear cache."
+        self._data = {}
+        self._keys = deque()
+
+
+_K = TypeVar("_K", bound=Tuple[Hashable, ...])
+_V = TypeVar("_V")
+
+
+class FastDictCache(Dict[_K, _V]):
+    """
+    Fast, lightweight cache which keeps at most `size` items.
+    It will discard the oldest items in the cache first.
+
+    The cache is a dictionary, which doesn't keep track of access counts.
+    It is perfect to cache little immutable objects which are not expensive to
+    create, but where a dictionary lookup is still much faster than an object
+    instantiation.
+
+    :param get_value: Callable that's called in case of a missing key.
+    """
+
+    # NOTE: This cache is used to cache `prompt_toolkit.layout.screen.Char` and
+    #       `prompt_toolkit.Document`. Make sure to keep this really lightweight.
+    #       Accessing the cache should stay faster than instantiating new
+    #       objects.
+    #       (Dictionary lookups are really fast.)
+    #       SimpleCache is still required for cases where the cache key is not
+    #       the same as the arguments given to the function that creates the
+    #       value.)
+    def __init__(self, get_value: Callable[..., _V], size: int = 1000000) -> None:
+        assert size > 0
+
+        self._keys: Deque[_K] = deque()
+        self.get_value = get_value
+        self.size = size
+
+    def __missing__(self, key: _K) -> _V:
+        # Remove the oldest key when the size is exceeded.
+        if len(self) > self.size:
+            key_to_remove = self._keys.popleft()
+            if key_to_remove in self:
+                del self[key_to_remove]
+
+        result = self.get_value(*key)
+        self[key] = result
+        self._keys.append(key)
+        return result
+
+
+_F = TypeVar("_F", bound=Callable[..., object])
+
+
+def memoized(maxsize: int = 1024) -> Callable[[_F], _F]:
+    """
+    Memoization decorator for immutable classes and pure functions.
+    """
+
+    def decorator(obj: _F) -> _F:
+        cache: SimpleCache[Hashable, Any] = SimpleCache(maxsize=maxsize)
+
+        @wraps(obj)
+        def new_callable(*a: Any, **kw: Any) -> Any:
+            def create_new() -> Any:
+                return obj(*a, **kw)
+
+            key = (a, tuple(sorted(kw.items())))
+            return cache.get(key, create_new)
+
+        return cast(_F, new_callable)
+
+    return decorator
diff --git a/src/prompt_toolkit/clipboard/__init__.py b/src/prompt_toolkit/clipboard/__init__.py
new file mode 100644
index 0000000..160b50a
--- /dev/null
+++ b/src/prompt_toolkit/clipboard/__init__.py
@@ -0,0 +1,15 @@
+from .base import Clipboard, ClipboardData, DummyClipboard, DynamicClipboard
+from .in_memory import InMemoryClipboard
+
+# We are not importing `PyperclipClipboard` here, because it would require the
+# `pyperclip` module to be present.
+
+# from .pyperclip import PyperclipClipboard
+
+__all__ = [
+    "Clipboard",
+    "ClipboardData",
+    "DummyClipboard",
+    "DynamicClipboard",
+    "InMemoryClipboard",
+]
diff --git a/src/prompt_toolkit/clipboard/base.py b/src/prompt_toolkit/clipboard/base.py
new file mode 100644
index 0000000..c24623d
--- /dev/null
+++ b/src/prompt_toolkit/clipboard/base.py
@@ -0,0 +1,107 @@
+"""
+Clipboard for command line interface.
+"""
+from abc import ABCMeta, abstractmethod
+from typing import Callable, Optional
+
+from prompt_toolkit.selection import SelectionType
+
+__all__ = [
+    "Clipboard",
+    "ClipboardData",
+    "DummyClipboard",
+    "DynamicClipboard",
+]
+
+
+class ClipboardData:
+    """
+    Text on the clipboard.
+
+    :param text: string
+    :param type: :class:`~prompt_toolkit.selection.SelectionType`
+    """
+
+    def __init__(
+        self, text: str = "", type: SelectionType = SelectionType.CHARACTERS
+    ) -> None:
+
+        self.text = text
+        self.type = type
+
+
+class Clipboard(metaclass=ABCMeta):
+    """
+    Abstract baseclass for clipboards.
+    (An implementation can be in memory, it can share the X11 or Windows
+    keyboard, or can be persistent.)
+    """
+
+    @abstractmethod
+    def set_data(self, data: ClipboardData) -> None:
+        """
+        Set data to the clipboard.
+
+        :param data: :class:`~.ClipboardData` instance.
+        """
+
+    def set_text(self, text: str) -> None:  # Not abstract.
+        """
+        Shortcut for setting plain text on clipboard.
+        """
+        self.set_data(ClipboardData(text))
+
+    def rotate(self) -> None:
+        """
+        For Emacs mode, rotate the kill ring.
+        """
+
+    @abstractmethod
+    def get_data(self) -> ClipboardData:
+        """
+        Return clipboard data.
+        """
+
+
+class DummyClipboard(Clipboard):
+    """
+    Clipboard implementation that doesn't remember anything.
+    """
+
+    def set_data(self, data: ClipboardData) -> None:
+        pass
+
+    def set_text(self, text: str) -> None:
+        pass
+
+    def rotate(self) -> None:
+        pass
+
+    def get_data(self) -> ClipboardData:
+        return ClipboardData()
+
+
+class DynamicClipboard(Clipboard):
+    """
+    Clipboard class that can dynamically returns any Clipboard.
+
+    :param get_clipboard: Callable that returns a :class:`.Clipboard` instance.
+    """
+
+    def __init__(self, get_clipboard: Callable[[], Optional[Clipboard]]) -> None:
+        self.get_clipboard = get_clipboard
+
+    def _clipboard(self) -> Clipboard:
+        return self.get_clipboard() or DummyClipboard()
+
+    def set_data(self, data: ClipboardData) -> None:
+        self._clipboard().set_data(data)
+
+    def set_text(self, text: str) -> None:
+        self._clipboard().set_text(text)
+
+    def rotate(self) -> None:
+        self._clipboard().rotate()
+
+    def get_data(self) -> ClipboardData:
+        return self._clipboard().get_data()
diff --git a/src/prompt_toolkit/clipboard/in_memory.py b/src/prompt_toolkit/clipboard/in_memory.py
new file mode 100644
index 0000000..1902e36
--- /dev/null
+++ b/src/prompt_toolkit/clipboard/in_memory.py
@@ -0,0 +1,46 @@
+from collections import deque
+from typing import Deque, Optional
+
+from .base import Clipboard, ClipboardData
+
+__all__ = [
+    "InMemoryClipboard",
+]
+
+
+class InMemoryClipboard(Clipboard):
+    """
+    Default clipboard implementation.
+    Just keep the data in memory.
+
+    This implements a kill-ring, for Emacs mode.
+    """
+
+    def __init__(
+        self, data: Optional[ClipboardData] = None, max_size: int = 60
+    ) -> None:
+
+        assert max_size >= 1
+
+        self.max_size = max_size
+        self._ring: Deque[ClipboardData] = deque()
+
+        if data is not None:
+            self.set_data(data)
+
+    def set_data(self, data: ClipboardData) -> None:
+        self._ring.appendleft(data)
+
+        while len(self._ring) > self.max_size:
+            self._ring.pop()
+
+    def get_data(self) -> ClipboardData:
+        if self._ring:
+            return self._ring[0]
+        else:
+            return ClipboardData()
+
+    def rotate(self) -> None:
+        if self._ring:
+            # Add the very first item at the end.
+            self._ring.append(self._ring.popleft())
diff --git a/src/prompt_toolkit/clipboard/pyperclip.py b/src/prompt_toolkit/clipboard/pyperclip.py
new file mode 100644
index 0000000..c8cb7af
--- /dev/null
+++ b/src/prompt_toolkit/clipboard/pyperclip.py
@@ -0,0 +1,42 @@
+from typing import Optional
+
+import pyperclip
+
+from prompt_toolkit.selection import SelectionType
+
+from .base import Clipboard, ClipboardData
+
+__all__ = [
+    "PyperclipClipboard",
+]
+
+
+class PyperclipClipboard(Clipboard):
+    """
+    Clipboard that synchronizes with the Windows/Mac/Linux system clipboard,
+    using the pyperclip module.
+    """
+
+    def __init__(self) -> None:
+        self._data: Optional[ClipboardData] = None
+
+    def set_data(self, data: ClipboardData) -> None:
+        self._data = data
+        pyperclip.copy(data.text)
+
+    def get_data(self) -> ClipboardData:
+        text = pyperclip.paste()
+
+        # When the clipboard data is equal to what we copied last time, reuse
+        # the `ClipboardData` instance. That way we're sure to keep the same
+        # `SelectionType`.
+        if self._data and self._data.text == text:
+            return self._data
+
+        # Pyperclip returned something else. Create a new `ClipboardData`
+        # instance.
+        else:
+            return ClipboardData(
+                text=text,
+                type=SelectionType.LINES if "\n" in text else SelectionType.CHARACTERS,
+            )
diff --git a/src/prompt_toolkit/completion/__init__.py b/src/prompt_toolkit/completion/__init__.py
new file mode 100644
index 0000000..270c743
--- /dev/null
+++ b/src/prompt_toolkit/completion/__init__.py
@@ -0,0 +1,41 @@
+from .base import (
+    CompleteEvent,
+    Completer,
+    Completion,
+    ConditionalCompleter,
+    DummyCompleter,
+    DynamicCompleter,
+    ThreadedCompleter,
+    get_common_complete_suffix,
+    merge_completers,
+)
+from .deduplicate import DeduplicateCompleter
+from .filesystem import ExecutableCompleter, PathCompleter
+from .fuzzy_completer import FuzzyCompleter, FuzzyWordCompleter
+from .nested import NestedCompleter
+from .word_completer import WordCompleter
+
+__all__ = [
+    # Base.
+    "Completion",
+    "Completer",
+    "ThreadedCompleter",
+    "DummyCompleter",
+    "DynamicCompleter",
+    "CompleteEvent",
+    "ConditionalCompleter",
+    "merge_completers",
+    "get_common_complete_suffix",
+    # Filesystem.
+    "PathCompleter",
+    "ExecutableCompleter",
+    # Fuzzy
+    "FuzzyCompleter",
+    "FuzzyWordCompleter",
+    # Nested.
+    "NestedCompleter",
+    # Word completer.
+    "WordCompleter",
+    # Deduplicate
+    "DeduplicateCompleter",
+]
diff --git a/src/prompt_toolkit/completion/base.py b/src/prompt_toolkit/completion/base.py
new file mode 100644
index 0000000..bd575ec
--- /dev/null
+++ b/src/prompt_toolkit/completion/base.py
@@ -0,0 +1,455 @@
+"""
+"""
+from abc import ABCMeta, abstractmethod
+from typing import AsyncGenerator, Callable, Iterable, List, Optional, Sequence
+
+from prompt_toolkit.document import Document
+from prompt_toolkit.eventloop import (
+    aclosing,
+    generator_to_async_generator,
+    get_event_loop,
+)
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.formatted_text import AnyFormattedText, StyleAndTextTuples
+
+__all__ = [
+    "Completion",
+    "Completer",
+    "ThreadedCompleter",
+    "DummyCompleter",
+    "DynamicCompleter",
+    "CompleteEvent",
+    "ConditionalCompleter",
+    "merge_completers",
+    "get_common_complete_suffix",
+]
+
+
+class Completion:
+    """
+    :param text: The new string that will be inserted into the document.
+    :param start_position: Position relative to the cursor_position where the
+        new text will start. The text will be inserted between the
+        start_position and the original cursor position.
+    :param display: (optional string or formatted text) If the completion has
+        to be displayed differently in the completion menu.
+    :param display_meta: (Optional string or formatted text) Meta information
+        about the completion, e.g. the path or source where it's coming from.
+        This can also be a callable that returns a string.
+    :param style: Style string.
+    :param selected_style: Style string, used for a selected completion.
+        This can override the `style` parameter.
+    """
+
+    def __init__(
+        self,
+        text: str,
+        start_position: int = 0,
+        display: Optional[AnyFormattedText] = None,
+        display_meta: Optional[AnyFormattedText] = None,
+        style: str = "",
+        selected_style: str = "",
+    ) -> None:
+
+        from prompt_toolkit.formatted_text import to_formatted_text
+
+        self.text = text
+        self.start_position = start_position
+        self._display_meta = display_meta
+
+        if display is None:
+            display = text
+
+        self.display = to_formatted_text(display)
+
+        self.style = style
+        self.selected_style = selected_style
+
+        assert self.start_position <= 0
+
+    def __repr__(self) -> str:
+        if isinstance(self.display, str) and self.display == self.text:
+            return "{}(text={!r}, start_position={!r})".format(
+                self.__class__.__name__,
+                self.text,
+                self.start_position,
+            )
+        else:
+            return "{}(text={!r}, start_position={!r}, display={!r})".format(
+                self.__class__.__name__,
+                self.text,
+                self.start_position,
+                self.display,
+            )
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, Completion):
+            return False
+        return (
+            self.text == other.text
+            and self.start_position == other.start_position
+            and self.display == other.display
+            and self._display_meta == other._display_meta
+        )
+
+    def __hash__(self) -> int:
+        return hash((self.text, self.start_position, self.display, self._display_meta))
+
+    @property
+    def display_text(self) -> str:
+        "The 'display' field as plain text."
+        from prompt_toolkit.formatted_text import fragment_list_to_text
+
+        return fragment_list_to_text(self.display)
+
+    @property
+    def display_meta(self) -> StyleAndTextTuples:
+        "Return meta-text. (This is lazy when using a callable)."
+        from prompt_toolkit.formatted_text import to_formatted_text
+
+        return to_formatted_text(self._display_meta or "")
+
+    @property
+    def display_meta_text(self) -> str:
+        "The 'meta' field as plain text."
+        from prompt_toolkit.formatted_text import fragment_list_to_text
+
+        return fragment_list_to_text(self.display_meta)
+
+    def new_completion_from_position(self, position: int) -> "Completion":
+        """
+        (Only for internal use!)
+        Get a new completion by splitting this one. Used by `Application` when
+        it needs to have a list of new completions after inserting the common
+        prefix.
+        """
+        assert position - self.start_position >= 0
+
+        return Completion(
+            text=self.text[position - self.start_position :],
+            display=self.display,
+            display_meta=self._display_meta,
+        )
+
+
+class CompleteEvent:
+    """
+    Event that called the completer.
+
+    :param text_inserted: When True, it means that completions are requested
+        because of a text insert. (`Buffer.complete_while_typing`.)
+    :param completion_requested: When True, it means that the user explicitly
+        pressed the `Tab` key in order to view the completions.
+
+    These two flags can be used for instance to implement a completer that
+    shows some completions when ``Tab`` has been pressed, but not
+    automatically when the user presses a space. (Because of
+    `complete_while_typing`.)
+    """
+
+    def __init__(
+        self, text_inserted: bool = False, completion_requested: bool = False
+    ) -> None:
+        assert not (text_inserted and completion_requested)
+
+        #: Automatic completion while typing.
+        self.text_inserted = text_inserted
+
+        #: Used explicitly requested completion by pressing 'tab'.
+        self.completion_requested = completion_requested
+
+    def __repr__(self) -> str:
+        return "{}(text_inserted={!r}, completion_requested={!r})".format(
+            self.__class__.__name__,
+            self.text_inserted,
+            self.completion_requested,
+        )
+
+
+class Completer(metaclass=ABCMeta):
+    """
+    Base class for completer implementations.
+    """
+
+    @abstractmethod
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        """
+        This should be a generator that yields :class:`.Completion` instances.
+
+        If the generation of completions is something expensive (that takes a
+        lot of time), consider wrapping this `Completer` class in a
+        `ThreadedCompleter`. In that case, the completer algorithm runs in a
+        background thread and completions will be displayed as soon as they
+        arrive.
+
+        :param document: :class:`~prompt_toolkit.document.Document` instance.
+        :param complete_event: :class:`.CompleteEvent` instance.
+        """
+        while False:
+            yield
+
+    async def get_completions_async(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> AsyncGenerator[Completion, None]:
+        """
+        Asynchronous generator for completions. (Probably, you won't have to
+        override this.)
+
+        Asynchronous generator of :class:`.Completion` objects.
+        """
+        for item in self.get_completions(document, complete_event):
+            yield item
+
+
+class ThreadedCompleter(Completer):
+    """
+    Wrapper that runs the `get_completions` generator in a thread.
+
+    (Use this to prevent the user interface from becoming unresponsive if the
+    generation of completions takes too much time.)
+
+    The completions will be displayed as soon as they are produced. The user
+    can already select a completion, even if not all completions are displayed.
+    """
+
+    def __init__(self, completer: Completer) -> None:
+        self.completer = completer
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        return self.completer.get_completions(document, complete_event)
+
+    async def get_completions_async(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> AsyncGenerator[Completion, None]:
+        """
+        Asynchronous generator of completions.
+        """
+        # NOTE: Right now, we are consuming the `get_completions` generator in
+        #       a synchronous background thread, then passing the results one
+        #       at a time over a queue, and consuming this queue in the main
+        #       thread (that's what `generator_to_async_generator` does). That
+        #       means that if the completer is *very* slow, we'll be showing
+        #       completions in the UI once they are computed.
+
+        #       It's very tempting to replace this implementation with the
+        #       commented code below for several reasons:
+
+        #       - `generator_to_async_generator` is not perfect and hard to get
+        #         right. It's a lot of complexity for little gain. The
+        #         implementation needs a huge buffer for it to be efficient
+        #         when there are many completions (like 50k+).
+        #       - Normally, a completer is supposed to be fast, users can have
+        #         "complete while typing" enabled, and want to see the
+        #         completions within a second. Handling one completion at a
+        #         time, and rendering once we get it here doesn't make any
+        #         sense if this is quick anyway.
+        #       - Completers like `FuzzyCompleter` prepare all completions
+        #         anyway so that they can be sorted by accuracy before they are
+        #         yielded. At the point that we start yielding completions
+        #         here, we already have all completions.
+        #       - The `Buffer` class has complex logic to invalidate the UI
+        #         while it is consuming the completions. We don't want to
+        #         invalidate the UI for every completion (if there are many),
+        #         but we want to do it often enough so that completions are
+        #         being displayed while they are produced.
+
+        #       We keep the current behavior mainly for backward-compatibility.
+        #       Similarly, it would be better for this function to not return
+        #       an async generator, but simply be a coroutine that returns a
+        #       list of `Completion` objects, containing all completions at
+        #       once.
+
+        #       Note that this argument doesn't mean we shouldn't use
+        #       `ThreadedCompleter`. It still makes sense to produce
+        #       completions in a background thread, because we don't want to
+        #       freeze the UI while the user is typing. But sending the
+        #       completions one at a time to the UI maybe isn't worth it.
+
+        # def get_all_in_thread() -> List[Completion]:
+        #   return list(self.get_completions(document, complete_event))
+
+        # completions = await get_event_loop().run_in_executor(None, get_all_in_thread)
+        # for completion in completions:
+        #   yield completion
+
+        async with aclosing(
+            generator_to_async_generator(
+                lambda: self.completer.get_completions(document, complete_event)
+            )
+        ) as async_generator:
+            async for completion in async_generator:
+                yield completion
+
+    def __repr__(self) -> str:
+        return f"ThreadedCompleter({self.completer!r})"
+
+
+class DummyCompleter(Completer):
+    """
+    A completer that doesn't return any completion.
+    """
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        return []
+
+    def __repr__(self) -> str:
+        return "DummyCompleter()"
+
+
+class DynamicCompleter(Completer):
+    """
+    Completer class that can dynamically returns any Completer.
+
+    :param get_completer: Callable that returns a :class:`.Completer` instance.
+    """
+
+    def __init__(self, get_completer: Callable[[], Optional[Completer]]) -> None:
+        self.get_completer = get_completer
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        completer = self.get_completer() or DummyCompleter()
+        return completer.get_completions(document, complete_event)
+
+    async def get_completions_async(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> AsyncGenerator[Completion, None]:
+        completer = self.get_completer() or DummyCompleter()
+
+        async for completion in completer.get_completions_async(
+            document, complete_event
+        ):
+            yield completion
+
+    def __repr__(self) -> str:
+        return f"DynamicCompleter({self.get_completer!r} -> {self.get_completer()!r})"
+
+
+class ConditionalCompleter(Completer):
+    """
+    Wrapper around any other completer that will enable/disable the completions
+    depending on whether the received condition is satisfied.
+
+    :param completer: :class:`.Completer` instance.
+    :param filter: :class:`.Filter` instance.
+    """
+
+    def __init__(self, completer: Completer, filter: FilterOrBool) -> None:
+        self.completer = completer
+        self.filter = to_filter(filter)
+
+    def __repr__(self) -> str:
+        return f"ConditionalCompleter({self.completer!r}, filter={self.filter!r})"
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        # Get all completions in a blocking way.
+        if self.filter():
+            yield from self.completer.get_completions(document, complete_event)
+
+    async def get_completions_async(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> AsyncGenerator[Completion, None]:
+
+        # Get all completions in a non-blocking way.
+        if self.filter():
+            async with aclosing(
+                self.completer.get_completions_async(document, complete_event)
+            ) as async_generator:
+                async for item in async_generator:
+                    yield item
+
+
+class _MergedCompleter(Completer):
+    """
+    Combine several completers into one.
+    """
+
+    def __init__(self, completers: Sequence[Completer]) -> None:
+        self.completers = completers
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        # Get all completions from the other completers in a blocking way.
+        for completer in self.completers:
+            yield from completer.get_completions(document, complete_event)
+
+    async def get_completions_async(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> AsyncGenerator[Completion, None]:
+
+        # Get all completions from the other completers in a non-blocking way.
+        for completer in self.completers:
+            async with aclosing(
+                completer.get_completions_async(document, complete_event)
+            ) as async_generator:
+                async for item in async_generator:
+                    yield item
+
+
+def merge_completers(
+    completers: Sequence[Completer], deduplicate: bool = False
+) -> Completer:
+    """
+    Combine several completers into one.
+
+    :param deduplicate: If `True`, wrap the result in a `DeduplicateCompleter`
+        so that completions that would result in the same text will be
+        deduplicated.
+    """
+    if deduplicate:
+        from .deduplicate import DeduplicateCompleter
+
+        return DeduplicateCompleter(_MergedCompleter(completers))
+
+    return _MergedCompleter(completers)
+
+
+def get_common_complete_suffix(
+    document: Document, completions: Sequence[Completion]
+) -> str:
+    """
+    Return the common prefix for all completions.
+    """
+    # Take only completions that don't change the text before the cursor.
+    def doesnt_change_before_cursor(completion: Completion) -> bool:
+        end = completion.text[: -completion.start_position]
+        return document.text_before_cursor.endswith(end)
+
+    completions2 = [c for c in completions if doesnt_change_before_cursor(c)]
+
+    # When there is at least one completion that changes the text before the
+    # cursor, don't return any common part.
+    if len(completions2) != len(completions):
+        return ""
+
+    # Return the common prefix.
+    def get_suffix(completion: Completion) -> str:
+        return completion.text[-completion.start_position :]
+
+    return _commonprefix([get_suffix(c) for c in completions2])
+
+
+def _commonprefix(strings: Iterable[str]) -> str:
+    # Similar to os.path.commonprefix
+    if not strings:
+        return ""
+
+    else:
+        s1 = min(strings)
+        s2 = max(strings)
+
+        for i, c in enumerate(s1):
+            if c != s2[i]:
+                return s1[:i]
+
+        return s1
diff --git a/src/prompt_toolkit/completion/deduplicate.py b/src/prompt_toolkit/completion/deduplicate.py
new file mode 100644
index 0000000..6ef9522
--- /dev/null
+++ b/src/prompt_toolkit/completion/deduplicate.py
@@ -0,0 +1,43 @@
+from typing import Iterable, Set
+
+from prompt_toolkit.document import Document
+
+from .base import CompleteEvent, Completer, Completion
+
+__all__ = ["DeduplicateCompleter"]
+
+
+class DeduplicateCompleter(Completer):
+    """
+    Wrapper around a completer that removes duplicates. Only the first unique
+    completions are kept.
+
+    Completions are considered to be a duplicate if they result in the same
+    document text when they would be applied.
+    """
+
+    def __init__(self, completer: Completer) -> None:
+        self.completer = completer
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        # Keep track of the document strings we'd get after applying any completion.
+        found_so_far: Set[str] = set()
+
+        for completion in self.completer.get_completions(document, complete_event):
+            text_if_applied = (
+                document.text[: document.cursor_position + completion.start_position]
+                + completion.text
+                + document.text[document.cursor_position :]
+            )
+
+            if text_if_applied == document.text:
+                # Don't include completions that don't have any effect at all.
+                continue
+
+            if text_if_applied in found_so_far:
+                continue
+
+            found_so_far.add(text_if_applied)
+            yield completion
diff --git a/src/prompt_toolkit/completion/filesystem.py b/src/prompt_toolkit/completion/filesystem.py
new file mode 100644
index 0000000..719eac6
--- /dev/null
+++ b/src/prompt_toolkit/completion/filesystem.py
@@ -0,0 +1,117 @@
+import os
+from typing import Callable, Iterable, List, Optional
+
+from prompt_toolkit.completion import CompleteEvent, Completer, Completion
+from prompt_toolkit.document import Document
+
+__all__ = [
+    "PathCompleter",
+    "ExecutableCompleter",
+]
+
+
+class PathCompleter(Completer):
+    """
+    Complete for Path variables.
+
+    :param get_paths: Callable which returns a list of directories to look into
+                      when the user enters a relative path.
+    :param file_filter: Callable which takes a filename and returns whether
+                        this file should show up in the completion. ``None``
+                        when no filtering has to be done.
+    :param min_input_len: Don't do autocompletion when the input string is shorter.
+    """
+
+    def __init__(
+        self,
+        only_directories: bool = False,
+        get_paths: Optional[Callable[[], List[str]]] = None,
+        file_filter: Optional[Callable[[str], bool]] = None,
+        min_input_len: int = 0,
+        expanduser: bool = False,
+    ) -> None:
+
+        self.only_directories = only_directories
+        self.get_paths = get_paths or (lambda: ["."])
+        self.file_filter = file_filter or (lambda _: True)
+        self.min_input_len = min_input_len
+        self.expanduser = expanduser
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        text = document.text_before_cursor
+
+        # Complete only when we have at least the minimal input length,
+        # otherwise, we can too many results and autocompletion will become too
+        # heavy.
+        if len(text) < self.min_input_len:
+            return
+
+        try:
+            # Do tilde expansion.
+            if self.expanduser:
+                text = os.path.expanduser(text)
+
+            # Directories where to look.
+            dirname = os.path.dirname(text)
+            if dirname:
+                directories = [
+                    os.path.dirname(os.path.join(p, text)) for p in self.get_paths()
+                ]
+            else:
+                directories = self.get_paths()
+
+            # Start of current file.
+            prefix = os.path.basename(text)
+
+            # Get all filenames.
+            filenames = []
+            for directory in directories:
+                # Look for matches in this directory.
+                if os.path.isdir(directory):
+                    for filename in os.listdir(directory):
+                        if filename.startswith(prefix):
+                            filenames.append((directory, filename))
+
+            # Sort
+            filenames = sorted(filenames, key=lambda k: k[1])
+
+            # Yield them.
+            for directory, filename in filenames:
+                completion = filename[len(prefix) :]
+                full_name = os.path.join(directory, filename)
+
+                if os.path.isdir(full_name):
+                    # For directories, add a slash to the filename.
+                    # (We don't add them to the `completion`. Users can type it
+                    # to trigger the autocompletion themselves.)
+                    filename += "/"
+                elif self.only_directories:
+                    continue
+
+                if not self.file_filter(full_name):
+                    continue
+
+                yield Completion(
+                    text=completion,
+                    start_position=0,
+                    display=filename,
+                )
+        except OSError:
+            pass
+
+
+class ExecutableCompleter(PathCompleter):
+    """
+    Complete only executable files in the current path.
+    """
+
+    def __init__(self) -> None:
+        super().__init__(
+            only_directories=False,
+            min_input_len=1,
+            get_paths=lambda: os.environ.get("PATH", "").split(os.pathsep),
+            file_filter=lambda name: os.access(name, os.X_OK),
+            expanduser=True,
+        ),
diff --git a/src/prompt_toolkit/completion/fuzzy_completer.py b/src/prompt_toolkit/completion/fuzzy_completer.py
new file mode 100644
index 0000000..ab5402f
--- /dev/null
+++ b/src/prompt_toolkit/completion/fuzzy_completer.py
@@ -0,0 +1,213 @@
+import re
+from typing import Callable, Dict, Iterable, List, NamedTuple, Optional, Tuple, Union
+
+from prompt_toolkit.document import Document
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.formatted_text import AnyFormattedText, StyleAndTextTuples
+
+from .base import CompleteEvent, Completer, Completion
+from .word_completer import WordCompleter
+
+__all__ = [
+    "FuzzyCompleter",
+    "FuzzyWordCompleter",
+]
+
+
+class FuzzyCompleter(Completer):
+    """
+    Fuzzy completion.
+    This wraps any other completer and turns it into a fuzzy completer.
+
+    If the list of words is: ["leopard" , "gorilla", "dinosaur", "cat", "bee"]
+    Then trying to complete "oar" would yield "leopard" and "dinosaur", but not
+    the others, because they match the regular expression 'o.*a.*r'.
+    Similar, in another application "djm" could expand to "django_migrations".
+
+    The results are sorted by relevance, which is defined as the start position
+    and the length of the match.
+
+    Notice that this is not really a tool to work around spelling mistakes,
+    like what would be possible with difflib. The purpose is rather to have a
+    quicker or more intuitive way to filter the given completions, especially
+    when many completions have a common prefix.
+
+    Fuzzy algorithm is based on this post:
+    https://blog.amjith.com/fuzzyfinder-in-10-lines-of-python
+
+    :param completer: A :class:`~.Completer` instance.
+    :param WORD: When True, use WORD characters.
+    :param pattern: Regex pattern which selects the characters before the
+        cursor that are considered for the fuzzy matching.
+    :param enable_fuzzy: (bool or `Filter`) Enabled the fuzzy behavior. For
+        easily turning fuzzyness on or off according to a certain condition.
+    """
+
+    def __init__(
+        self,
+        completer: Completer,
+        WORD: bool = False,
+        pattern: Optional[str] = None,
+        enable_fuzzy: FilterOrBool = True,
+    ) -> None:
+
+        assert pattern is None or pattern.startswith("^")
+
+        self.completer = completer
+        self.pattern = pattern
+        self.WORD = WORD
+        self.pattern = pattern
+        self.enable_fuzzy = to_filter(enable_fuzzy)
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        if self.enable_fuzzy():
+            return self._get_fuzzy_completions(document, complete_event)
+        else:
+            return self.completer.get_completions(document, complete_event)
+
+    def _get_pattern(self) -> str:
+        if self.pattern:
+            return self.pattern
+        if self.WORD:
+            return r"[^\s]+"
+        return "^[a-zA-Z0-9_]*"
+
+    def _get_fuzzy_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        word_before_cursor = document.get_word_before_cursor(
+            pattern=re.compile(self._get_pattern())
+        )
+
+        # Get completions
+        document2 = Document(
+            text=document.text[: document.cursor_position - len(word_before_cursor)],
+            cursor_position=document.cursor_position - len(word_before_cursor),
+        )
+
+        inner_completions = list(
+            self.completer.get_completions(document2, complete_event)
+        )
+
+        fuzzy_matches: List[_FuzzyMatch] = []
+
+        if word_before_cursor == "":
+            # If word before the cursor is an empty string, consider all
+            # completions, without filtering everything with an empty regex
+            # pattern.
+            fuzzy_matches = [_FuzzyMatch(0, 0, compl) for compl in inner_completions]
+        else:
+            pat = ".*?".join(map(re.escape, word_before_cursor))
+            pat = f"(?=({pat}))"  # lookahead regex to manage overlapping matches
+            regex = re.compile(pat, re.IGNORECASE)
+            for compl in inner_completions:
+                matches = list(regex.finditer(compl.text))
+                if matches:
+                    # Prefer the match, closest to the left, then shortest.
+                    best = min(matches, key=lambda m: (m.start(), len(m.group(1))))
+                    fuzzy_matches.append(
+                        _FuzzyMatch(len(best.group(1)), best.start(), compl)
+                    )
+
+            def sort_key(fuzzy_match: "_FuzzyMatch") -> Tuple[int, int]:
+                "Sort by start position, then by the length of the match."
+                return fuzzy_match.start_pos, fuzzy_match.match_length
+
+            fuzzy_matches = sorted(fuzzy_matches, key=sort_key)
+
+        for match in fuzzy_matches:
+            # Include these completions, but set the correct `display`
+            # attribute and `start_position`.
+            yield Completion(
+                text=match.completion.text,
+                start_position=match.completion.start_position
+                - len(word_before_cursor),
+                # We access to private `_display_meta` attribute, because that one is lazy.
+                display_meta=match.completion._display_meta,
+                display=self._get_display(match, word_before_cursor),
+                style=match.completion.style,
+            )
+
+    def _get_display(
+        self, fuzzy_match: "_FuzzyMatch", word_before_cursor: str
+    ) -> AnyFormattedText:
+        """
+        Generate formatted text for the display label.
+        """
+
+        def get_display() -> AnyFormattedText:
+            m = fuzzy_match
+            word = m.completion.text
+
+            if m.match_length == 0:
+                # No highlighting when we have zero length matches (no input text).
+                # In this case, use the original display text (which can include
+                # additional styling or characters).
+                return m.completion.display
+
+            result: StyleAndTextTuples = []
+
+            # Text before match.
+            result.append(("class:fuzzymatch.outside", word[: m.start_pos]))
+
+            # The match itself.
+            characters = list(word_before_cursor)
+
+            for c in word[m.start_pos : m.start_pos + m.match_length]:
+                classname = "class:fuzzymatch.inside"
+                if characters and c.lower() == characters[0].lower():
+                    classname += ".character"
+                    del characters[0]
+
+                result.append((classname, c))
+
+            # Text after match.
+            result.append(
+                ("class:fuzzymatch.outside", word[m.start_pos + m.match_length :])
+            )
+
+            return result
+
+        return get_display()
+
+
+class FuzzyWordCompleter(Completer):
+    """
+    Fuzzy completion on a list of words.
+
+    (This is basically a `WordCompleter` wrapped in a `FuzzyCompleter`.)
+
+    :param words: List of words or callable that returns a list of words.
+    :param meta_dict: Optional dict mapping words to their meta-information.
+    :param WORD: When True, use WORD characters.
+    """
+
+    def __init__(
+        self,
+        words: Union[List[str], Callable[[], List[str]]],
+        meta_dict: Optional[Dict[str, str]] = None,
+        WORD: bool = False,
+    ) -> None:
+
+        self.words = words
+        self.meta_dict = meta_dict or {}
+        self.WORD = WORD
+
+        self.word_completer = WordCompleter(
+            words=self.words, WORD=self.WORD, meta_dict=self.meta_dict
+        )
+
+        self.fuzzy_completer = FuzzyCompleter(self.word_completer, WORD=self.WORD)
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        return self.fuzzy_completer.get_completions(document, complete_event)
+
+
+class _FuzzyMatch(NamedTuple):
+    match_length: int
+    start_pos: int
+    completion: Completion
diff --git a/src/prompt_toolkit/completion/nested.py b/src/prompt_toolkit/completion/nested.py
new file mode 100644
index 0000000..f8656b2
--- /dev/null
+++ b/src/prompt_toolkit/completion/nested.py
@@ -0,0 +1,107 @@
+"""
+Nestedcompleter for completion of hierarchical data structures.
+"""
+from typing import Any, Dict, Iterable, Mapping, Optional, Set, Union
+
+from prompt_toolkit.completion import CompleteEvent, Completer, Completion
+from prompt_toolkit.completion.word_completer import WordCompleter
+from prompt_toolkit.document import Document
+
+__all__ = ["NestedCompleter"]
+
+# NestedDict = Mapping[str, Union['NestedDict', Set[str], None, Completer]]
+NestedDict = Mapping[str, Union[Any, Set[str], None, Completer]]
+
+
+class NestedCompleter(Completer):
+    """
+    Completer which wraps around several other completers, and calls any the
+    one that corresponds with the first word of the input.
+
+    By combining multiple `NestedCompleter` instances, we can achieve multiple
+    hierarchical levels of autocompletion. This is useful when `WordCompleter`
+    is not sufficient.
+
+    If you need multiple levels, check out the `from_nested_dict` classmethod.
+    """
+
+    def __init__(
+        self, options: Dict[str, Optional[Completer]], ignore_case: bool = True
+    ) -> None:
+
+        self.options = options
+        self.ignore_case = ignore_case
+
+    def __repr__(self) -> str:
+        return f"NestedCompleter({self.options!r}, ignore_case={self.ignore_case!r})"
+
+    @classmethod
+    def from_nested_dict(cls, data: NestedDict) -> "NestedCompleter":
+        """
+        Create a `NestedCompleter`, starting from a nested dictionary data
+        structure, like this:
+
+        .. code::
+
+            data = {
+                'show': {
+                    'version': None,
+                    'interfaces': None,
+                    'clock': None,
+                    'ip': {'interface': {'brief'}}
+                },
+                'exit': None
+                'enable': None
+            }
+
+        The value should be `None` if there is no further completion at some
+        point. If all values in the dictionary are None, it is also possible to
+        use a set instead.
+
+        Values in this data structure can be a completers as well.
+        """
+        options: Dict[str, Optional[Completer]] = {}
+        for key, value in data.items():
+            if isinstance(value, Completer):
+                options[key] = value
+            elif isinstance(value, dict):
+                options[key] = cls.from_nested_dict(value)
+            elif isinstance(value, set):
+                options[key] = cls.from_nested_dict({item: None for item in value})
+            else:
+                assert value is None
+                options[key] = None
+
+        return cls(options)
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        # Split document.
+        text = document.text_before_cursor.lstrip()
+        stripped_len = len(document.text_before_cursor) - len(text)
+
+        # If there is a space, check for the first term, and use a
+        # subcompleter.
+        if " " in text:
+            first_term = text.split()[0]
+            completer = self.options.get(first_term)
+
+            # If we have a sub completer, use this for the completions.
+            if completer is not None:
+                remaining_text = text[len(first_term) :].lstrip()
+                move_cursor = len(text) - len(remaining_text) + stripped_len
+
+                new_document = Document(
+                    remaining_text,
+                    cursor_position=document.cursor_position - move_cursor,
+                )
+
+                yield from completer.get_completions(new_document, complete_event)
+
+        # No space in the input: behave exactly like `WordCompleter`.
+        else:
+            completer = WordCompleter(
+                list(self.options.keys()), ignore_case=self.ignore_case
+            )
+            yield from completer.get_completions(document, complete_event)
diff --git a/src/prompt_toolkit/completion/word_completer.py b/src/prompt_toolkit/completion/word_completer.py
new file mode 100644
index 0000000..28c133e
--- /dev/null
+++ b/src/prompt_toolkit/completion/word_completer.py
@@ -0,0 +1,93 @@
+from typing import Callable, Iterable, List, Mapping, Optional, Pattern, Union
+
+from prompt_toolkit.completion import CompleteEvent, Completer, Completion
+from prompt_toolkit.document import Document
+from prompt_toolkit.formatted_text import AnyFormattedText
+
+__all__ = [
+    "WordCompleter",
+]
+
+
+class WordCompleter(Completer):
+    """
+    Simple autocompletion on a list of words.
+
+    :param words: List of words or callable that returns a list of words.
+    :param ignore_case: If True, case-insensitive completion.
+    :param meta_dict: Optional dict mapping words to their meta-text. (This
+        should map strings to strings or formatted text.)
+    :param WORD: When True, use WORD characters.
+    :param sentence: When True, don't complete by comparing the word before the
+        cursor, but by comparing all the text before the cursor. In this case,
+        the list of words is just a list of strings, where each string can
+        contain spaces. (Can not be used together with the WORD option.)
+    :param match_middle: When True, match not only the start, but also in the
+                         middle of the word.
+    :param pattern: Optional compiled regex for finding the word before
+        the cursor to complete. When given, use this regex pattern instead of
+        default one (see document._FIND_WORD_RE)
+    """
+
+    def __init__(
+        self,
+        words: Union[List[str], Callable[[], List[str]]],
+        ignore_case: bool = False,
+        display_dict: Optional[Mapping[str, AnyFormattedText]] = None,
+        meta_dict: Optional[Mapping[str, AnyFormattedText]] = None,
+        WORD: bool = False,
+        sentence: bool = False,
+        match_middle: bool = False,
+        pattern: Optional[Pattern[str]] = None,
+    ) -> None:
+
+        assert not (WORD and sentence)
+
+        self.words = words
+        self.ignore_case = ignore_case
+        self.display_dict = display_dict or {}
+        self.meta_dict = meta_dict or {}
+        self.WORD = WORD
+        self.sentence = sentence
+        self.match_middle = match_middle
+        self.pattern = pattern
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        # Get list of words.
+        words = self.words
+        if callable(words):
+            words = words()
+
+        # Get word/text before cursor.
+        if self.sentence:
+            word_before_cursor = document.text_before_cursor
+        else:
+            word_before_cursor = document.get_word_before_cursor(
+                WORD=self.WORD, pattern=self.pattern
+            )
+
+        if self.ignore_case:
+            word_before_cursor = word_before_cursor.lower()
+
+        def word_matches(word: str) -> bool:
+            """True when the word before the cursor matches."""
+            if self.ignore_case:
+                word = word.lower()
+
+            if self.match_middle:
+                return word_before_cursor in word
+            else:
+                return word.startswith(word_before_cursor)
+
+        for a in words:
+            if word_matches(a):
+                display = self.display_dict.get(a, a)
+                display_meta = self.meta_dict.get(a, "")
+                yield Completion(
+                    text=a,
+                    start_position=-len(word_before_cursor),
+                    display=display,
+                    display_meta=display_meta,
+                )
diff --git a/src/prompt_toolkit/contrib/__init__.py b/src/prompt_toolkit/contrib/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/prompt_toolkit/contrib/__init__.py
diff --git a/src/prompt_toolkit/contrib/completers/__init__.py b/src/prompt_toolkit/contrib/completers/__init__.py
new file mode 100644
index 0000000..50ca2f9
--- /dev/null
+++ b/src/prompt_toolkit/contrib/completers/__init__.py
@@ -0,0 +1,3 @@
+from .system import SystemCompleter
+
+__all__ = ["SystemCompleter"]
diff --git a/src/prompt_toolkit/contrib/completers/system.py b/src/prompt_toolkit/contrib/completers/system.py
new file mode 100644
index 0000000..9e63268
--- /dev/null
+++ b/src/prompt_toolkit/contrib/completers/system.py
@@ -0,0 +1,62 @@
+from prompt_toolkit.completion.filesystem import ExecutableCompleter, PathCompleter
+from prompt_toolkit.contrib.regular_languages.compiler import compile
+from prompt_toolkit.contrib.regular_languages.completion import GrammarCompleter
+
+__all__ = [
+    "SystemCompleter",
+]
+
+
+class SystemCompleter(GrammarCompleter):
+    """
+    Completer for system commands.
+    """
+
+    def __init__(self) -> None:
+        # Compile grammar.
+        g = compile(
+            r"""
+                # First we have an executable.
+                (?P<executable>[^\s]+)
+
+                # Ignore literals in between.
+                (
+                    \s+
+                    ("[^"]*" | '[^']*' | [^'"]+ )
+                )*
+
+                \s+
+
+                # Filename as parameters.
+                (
+                    (?P<filename>[^\s]+) |
+                    "(?P<double_quoted_filename>[^\s]+)" |
+                    '(?P<single_quoted_filename>[^\s]+)'
+                )
+            """,
+            escape_funcs={
+                "double_quoted_filename": (lambda string: string.replace('"', '\\"')),
+                "single_quoted_filename": (lambda string: string.replace("'", "\\'")),
+            },
+            unescape_funcs={
+                "double_quoted_filename": (
+                    lambda string: string.replace('\\"', '"')
+                ),  # XXX: not entirely correct.
+                "single_quoted_filename": (lambda string: string.replace("\\'", "'")),
+            },
+        )
+
+        # Create GrammarCompleter
+        super().__init__(
+            g,
+            {
+                "executable": ExecutableCompleter(),
+                "filename": PathCompleter(only_directories=False, expanduser=True),
+                "double_quoted_filename": PathCompleter(
+                    only_directories=False, expanduser=True
+                ),
+                "single_quoted_filename": PathCompleter(
+                    only_directories=False, expanduser=True
+                ),
+            },
+        )
diff --git a/src/prompt_toolkit/contrib/regular_languages/__init__.py b/src/prompt_toolkit/contrib/regular_languages/__init__.py
new file mode 100644
index 0000000..3f30614
--- /dev/null
+++ b/src/prompt_toolkit/contrib/regular_languages/__init__.py
@@ -0,0 +1,77 @@
+r"""
+Tool for expressing the grammar of an input as a regular language.
+==================================================================
+
+The grammar for the input of many simple command line interfaces can be
+expressed by a regular language. Examples are PDB (the Python debugger); a
+simple (bash-like) shell with "pwd", "cd", "cat" and "ls" commands; arguments
+that you can pass to an executable; etc. It is possible to use regular
+expressions for validation and parsing of such a grammar. (More about regular
+languages: http://en.wikipedia.org/wiki/Regular_language)
+
+Example
+-------
+
+Let's take the pwd/cd/cat/ls example. We want to have a shell that accepts
+these three commands. "cd" is followed by a quoted directory name and "cat" is
+followed by a quoted file name. (We allow quotes inside the filename when
+they're escaped with a backslash.) We could define the grammar using the
+following regular expression::
+
+    grammar = \s* (
+        pwd |
+        ls |
+        (cd  \s+ " ([^"]|\.)+ ") |
+        (cat \s+ " ([^"]|\.)+ ")
+    ) \s*
+
+
+What can we do with this grammar?
+---------------------------------
+
+- Syntax highlighting: We could use this for instance to give file names
+                       different colour.
+- Parse the result: .. We can extract the file names and commands by using a
+                       regular expression with named groups.
+- Input validation: .. Don't accept anything that does not match this grammar.
+                       When combined with a parser, we can also recursively do
+                       filename validation (and accept only existing files.)
+- Autocompletion: .... Each part of the grammar can have its own autocompleter.
+                       "cat" has to be completed using file names, while "cd"
+                       has to be completed using directory names.
+
+How does it work?
+-----------------
+
+As a user of this library, you have to define the grammar of the input as a
+regular expression. The parts of this grammar where autocompletion, validation
+or any other processing is required need to be marked using a regex named
+group. Like ``(?P<varname>...)`` for instance.
+
+When the input is processed for validation (for instance), the regex will
+execute, the named group is captured, and the validator associated with this
+named group will test the captured string.
+
+There is one tricky bit:
+
+    Often we operate on incomplete input (this is by definition the case for
+    autocompletion) and we have to decide for the cursor position in which
+    possible state the grammar it could be and in which way variables could be
+    matched up to that point.
+
+To solve this problem, the compiler takes the original regular expression and
+translates it into a set of other regular expressions which each match certain
+prefixes of the original regular expression. We generate one prefix regular
+expression for every named variable (with this variable being the end of that
+expression).
+
+
+TODO: some examples of:
+    - How to create a highlighter from this grammar.
+    - How to create a validator from this grammar.
+    - How to create an autocompleter from this grammar.
+    - How to create a parser from this grammar.
+"""
+from .compiler import compile
+
+__all__ = ["compile"]
diff --git a/src/prompt_toolkit/contrib/regular_languages/compiler.py b/src/prompt_toolkit/contrib/regular_languages/compiler.py
new file mode 100644
index 0000000..fed7849
--- /dev/null
+++ b/src/prompt_toolkit/contrib/regular_languages/compiler.py
@@ -0,0 +1,574 @@
+r"""
+Compiler for a regular grammar.
+
+Example usage::
+
+    # Create and compile grammar.
+    p = compile('add \s+ (?P<var1>[^\s]+)  \s+  (?P<var2>[^\s]+)')
+
+    # Match input string.
+    m = p.match('add 23 432')
+
+    # Get variables.
+    m.variables().get('var1')  # Returns "23"
+    m.variables().get('var2')  # Returns "432"
+
+
+Partial matches are possible::
+
+    # Create and compile grammar.
+    p = compile('''
+        # Operators with two arguments.
+        ((?P<operator1>[^\s]+)  \s+ (?P<var1>[^\s]+)  \s+  (?P<var2>[^\s]+)) |
+
+        # Operators with only one arguments.
+        ((?P<operator2>[^\s]+)  \s+ (?P<var1>[^\s]+))
+    ''')
+
+    # Match partial input string.
+    m = p.match_prefix('add 23')
+
+    # Get variables. (Notice that both operator1 and operator2 contain the
+    # value "add".) This is because our input is incomplete, and we don't know
+    # yet in which rule of the regex we we'll end up. It could also be that
+    # `operator1` and `operator2` have a different autocompleter and we want to
+    # call all possible autocompleters that would result in valid input.)
+    m.variables().get('var1')  # Returns "23"
+    m.variables().get('operator1')  # Returns "add"
+    m.variables().get('operator2')  # Returns "add"
+
+"""
+import re
+from typing import Callable, Dict, Iterable, Iterator, List
+from typing import Match as RegexMatch
+from typing import Optional, Pattern, Tuple
+
+from .regex_parser import (
+    AnyNode,
+    Lookahead,
+    Node,
+    NodeSequence,
+    Regex,
+    Repeat,
+    Variable,
+    parse_regex,
+    tokenize_regex,
+)
+
+__all__ = [
+    "compile",
+]
+
+
+# Name of the named group in the regex, matching trailing input.
+# (Trailing input is when the input contains characters after the end of the
+# expression has been matched.)
+_INVALID_TRAILING_INPUT = "invalid_trailing"
+
+EscapeFuncDict = Dict[str, Callable[[str], str]]
+
+
+class _CompiledGrammar:
+    """
+    Compiles a grammar. This will take the parse tree of a regular expression
+    and compile the grammar.
+
+    :param root_node: :class~`.regex_parser.Node` instance.
+    :param escape_funcs: `dict` mapping variable names to escape callables.
+    :param unescape_funcs: `dict` mapping variable names to unescape callables.
+    """
+
+    def __init__(
+        self,
+        root_node: Node,
+        escape_funcs: Optional[EscapeFuncDict] = None,
+        unescape_funcs: Optional[EscapeFuncDict] = None,
+    ) -> None:
+
+        self.root_node = root_node
+        self.escape_funcs = escape_funcs or {}
+        self.unescape_funcs = unescape_funcs or {}
+
+        #: Dictionary that will map the regex names to Node instances.
+        self._group_names_to_nodes: Dict[
+            str, str
+        ] = {}  # Maps regex group names to varnames.
+        counter = [0]
+
+        def create_group_func(node: Variable) -> str:
+            name = "n%s" % counter[0]
+            self._group_names_to_nodes[name] = node.varname
+            counter[0] += 1
+            return name
+
+        # Compile regex strings.
+        self._re_pattern = "^%s$" % self._transform(root_node, create_group_func)
+        self._re_prefix_patterns = list(
+            self._transform_prefix(root_node, create_group_func)
+        )
+
+        # Compile the regex itself.
+        flags = re.DOTALL  # Note that we don't need re.MULTILINE! (^ and $
+        # still represent the start and end of input text.)
+        self._re = re.compile(self._re_pattern, flags)
+        self._re_prefix = [re.compile(t, flags) for t in self._re_prefix_patterns]
+
+        # We compile one more set of regexes, similar to `_re_prefix`, but accept any trailing
+        # input. This will ensure that we can still highlight the input correctly, even when the
+        # input contains some additional characters at the end that don't match the grammar.)
+        self._re_prefix_with_trailing_input = [
+            re.compile(
+                r"(?:{})(?P<{}>.*?)$".format(t.rstrip("$"), _INVALID_TRAILING_INPUT),
+                flags,
+            )
+            for t in self._re_prefix_patterns
+        ]
+
+    def escape(self, varname: str, value: str) -> str:
+        """
+        Escape `value` to fit in the place of this variable into the grammar.
+        """
+        f = self.escape_funcs.get(varname)
+        return f(value) if f else value
+
+    def unescape(self, varname: str, value: str) -> str:
+        """
+        Unescape `value`.
+        """
+        f = self.unescape_funcs.get(varname)
+        return f(value) if f else value
+
+    @classmethod
+    def _transform(
+        cls, root_node: Node, create_group_func: Callable[[Variable], str]
+    ) -> str:
+        """
+        Turn a :class:`Node` object into a regular expression.
+
+        :param root_node: The :class:`Node` instance for which we generate the grammar.
+        :param create_group_func: A callable which takes a `Node` and returns the next
+            free name for this node.
+        """
+
+        def transform(node: Node) -> str:
+            # Turn `AnyNode` into an OR.
+            if isinstance(node, AnyNode):
+                return "(?:%s)" % "|".join(transform(c) for c in node.children)
+
+            # Concatenate a `NodeSequence`
+            elif isinstance(node, NodeSequence):
+                return "".join(transform(c) for c in node.children)
+
+            # For Regex and Lookahead nodes, just insert them literally.
+            elif isinstance(node, Regex):
+                return node.regex
+
+            elif isinstance(node, Lookahead):
+                before = "(?!" if node.negative else "(="
+                return before + transform(node.childnode) + ")"
+
+            # A `Variable` wraps the children into a named group.
+            elif isinstance(node, Variable):
+                return "(?P<{}>{})".format(
+                    create_group_func(node),
+                    transform(node.childnode),
+                )
+
+            # `Repeat`.
+            elif isinstance(node, Repeat):
+                if node.max_repeat is None:
+                    if node.min_repeat == 0:
+                        repeat_sign = "*"
+                    elif node.min_repeat == 1:
+                        repeat_sign = "+"
+                else:
+                    repeat_sign = "{%i,%s}" % (
+                        node.min_repeat,
+                        ("" if node.max_repeat is None else str(node.max_repeat)),
+                    )
+
+                return "(?:{}){}{}".format(
+                    transform(node.childnode),
+                    repeat_sign,
+                    ("" if node.greedy else "?"),
+                )
+            else:
+                raise TypeError(f"Got {node!r}")
+
+        return transform(root_node)
+
+    @classmethod
+    def _transform_prefix(
+        cls, root_node: Node, create_group_func: Callable[[Variable], str]
+    ) -> Iterable[str]:
+        """
+        Yield all the regular expressions matching a prefix of the grammar
+        defined by the `Node` instance.
+
+        For each `Variable`, one regex pattern will be generated, with this
+        named group at the end. This is required because a regex engine will
+        terminate once a match is found. For autocompletion however, we need
+        the matches for all possible paths, so that we can provide completions
+        for each `Variable`.
+
+        - So, in the case of an `Any` (`A|B|C)', we generate a pattern for each
+          clause. This is one for `A`, one for `B` and one for `C`. Unless some
+          groups don't contain a `Variable`, then these can be merged together.
+        - In the case of a `NodeSequence` (`ABC`), we generate a pattern for
+          each prefix that ends with a variable, and one pattern for the whole
+          sequence. So, that's one for `A`, one for `AB` and one for `ABC`.
+
+        :param root_node: The :class:`Node` instance for which we generate the grammar.
+        :param create_group_func: A callable which takes a `Node` and returns the next
+            free name for this node.
+        """
+
+        def contains_variable(node: Node) -> bool:
+            if isinstance(node, Regex):
+                return False
+            elif isinstance(node, Variable):
+                return True
+            elif isinstance(node, (Lookahead, Repeat)):
+                return contains_variable(node.childnode)
+            elif isinstance(node, (NodeSequence, AnyNode)):
+                return any(contains_variable(child) for child in node.children)
+
+            return False
+
+        def transform(node: Node) -> Iterable[str]:
+            # Generate separate pattern for all terms that contain variables
+            # within this OR. Terms that don't contain a variable can be merged
+            # together in one pattern.
+            if isinstance(node, AnyNode):
+                # If we have a definition like:
+                #           (?P<name> .*)  | (?P<city> .*)
+                # Then we want to be able to generate completions for both the
+                # name as well as the city. We do this by yielding two
+                # different regular expressions, because the engine won't
+                # follow multiple paths, if multiple are possible.
+                children_with_variable = []
+                children_without_variable = []
+                for c in node.children:
+                    if contains_variable(c):
+                        children_with_variable.append(c)
+                    else:
+                        children_without_variable.append(c)
+
+                for c in children_with_variable:
+                    yield from transform(c)
+
+                # Merge options without variable together.
+                if children_without_variable:
+                    yield "|".join(
+                        r for c in children_without_variable for r in transform(c)
+                    )
+
+            # For a sequence, generate a pattern for each prefix that ends with
+            # a variable + one pattern of the complete sequence.
+            # (This is because, for autocompletion, we match the text before
+            # the cursor, and completions are given for the variable that we
+            # match right before the cursor.)
+            elif isinstance(node, NodeSequence):
+                # For all components in the sequence, compute prefix patterns,
+                # as well as full patterns.
+                complete = [cls._transform(c, create_group_func) for c in node.children]
+                prefixes = [list(transform(c)) for c in node.children]
+                variable_nodes = [contains_variable(c) for c in node.children]
+
+                # If any child is contains a variable, we should yield a
+                # pattern up to that point, so that we are sure this will be
+                # matched.
+                for i in range(len(node.children)):
+                    if variable_nodes[i]:
+                        for c_str in prefixes[i]:
+                            yield "".join(complete[:i]) + c_str
+
+                # If there are non-variable nodes, merge all the prefixes into
+                # one pattern. If the input is: "[part1] [part2] [part3]", then
+                # this gets compiled into:
+                #  (complete1 + (complete2 + (complete3  | partial3) | partial2) | partial1 )
+                # For nodes that contain a variable, we skip the "|partial"
+                # part here, because thees are matched with the previous
+                # patterns.
+                if not all(variable_nodes):
+                    result = []
+
+                    # Start with complete patterns.
+                    for i in range(len(node.children)):
+                        result.append("(?:")
+                        result.append(complete[i])
+
+                    # Add prefix patterns.
+                    for i in range(len(node.children) - 1, -1, -1):
+                        if variable_nodes[i]:
+                            # No need to yield a prefix for this one, we did
+                            # the variable prefixes earlier.
+                            result.append(")")
+                        else:
+                            result.append("|(?:")
+                            # If this yields multiple, we should yield all combinations.
+                            assert len(prefixes[i]) == 1
+                            result.append(prefixes[i][0])
+                            result.append("))")
+
+                    yield "".join(result)
+
+            elif isinstance(node, Regex):
+                yield "(?:%s)?" % node.regex
+
+            elif isinstance(node, Lookahead):
+                if node.negative:
+                    yield "(?!%s)" % cls._transform(node.childnode, create_group_func)
+                else:
+                    # Not sure what the correct semantics are in this case.
+                    # (Probably it's not worth implementing this.)
+                    raise Exception("Positive lookahead not yet supported.")
+
+            elif isinstance(node, Variable):
+                # (Note that we should not append a '?' here. the 'transform'
+                # method will already recursively do that.)
+                for c_str in transform(node.childnode):
+                    yield f"(?P<{create_group_func(node)}>{c_str})"
+
+            elif isinstance(node, Repeat):
+                # If we have a repetition of 8 times. That would mean that the
+                # current input could have for instance 7 times a complete
+                # match, followed by a partial match.
+                prefix = cls._transform(node.childnode, create_group_func)
+
+                if node.max_repeat == 1:
+                    yield from transform(node.childnode)
+                else:
+                    for c_str in transform(node.childnode):
+                        if node.max_repeat:
+                            repeat_sign = "{,%i}" % (node.max_repeat - 1)
+                        else:
+                            repeat_sign = "*"
+                        yield "(?:{}){}{}{}".format(
+                            prefix,
+                            repeat_sign,
+                            ("" if node.greedy else "?"),
+                            c_str,
+                        )
+
+            else:
+                raise TypeError("Got %r" % node)
+
+        for r in transform(root_node):
+            yield "^(?:%s)$" % r
+
+    def match(self, string: str) -> Optional["Match"]:
+        """
+        Match the string with the grammar.
+        Returns a :class:`Match` instance or `None` when the input doesn't match the grammar.
+
+        :param string: The input string.
+        """
+        m = self._re.match(string)
+
+        if m:
+            return Match(
+                string, [(self._re, m)], self._group_names_to_nodes, self.unescape_funcs
+            )
+        return None
+
+    def match_prefix(self, string: str) -> Optional["Match"]:
+        """
+        Do a partial match of the string with the grammar. The returned
+        :class:`Match` instance can contain multiple representations of the
+        match. This will never return `None`. If it doesn't match at all, the "trailing input"
+        part will capture all of the input.
+
+        :param string: The input string.
+        """
+        # First try to match using `_re_prefix`. If nothing is found, use the patterns that
+        # also accept trailing characters.
+        for patterns in [self._re_prefix, self._re_prefix_with_trailing_input]:
+            matches = [(r, r.match(string)) for r in patterns]
+            matches2 = [(r, m) for r, m in matches if m]
+
+            if matches2 != []:
+                return Match(
+                    string, matches2, self._group_names_to_nodes, self.unescape_funcs
+                )
+
+        return None
+
+
+class Match:
+    """
+    :param string: The input string.
+    :param re_matches: List of (compiled_re_pattern, re_match) tuples.
+    :param group_names_to_nodes: Dictionary mapping all the re group names to the matching Node instances.
+    """
+
+    def __init__(
+        self,
+        string: str,
+        re_matches: List[Tuple[Pattern[str], RegexMatch[str]]],
+        group_names_to_nodes: Dict[str, str],
+        unescape_funcs: Dict[str, Callable[[str], str]],
+    ):
+        self.string = string
+        self._re_matches = re_matches
+        self._group_names_to_nodes = group_names_to_nodes
+        self._unescape_funcs = unescape_funcs
+
+    def _nodes_to_regs(self) -> List[Tuple[str, Tuple[int, int]]]:
+        """
+        Return a list of (varname, reg) tuples.
+        """
+
+        def get_tuples() -> Iterable[Tuple[str, Tuple[int, int]]]:
+            for r, re_match in self._re_matches:
+                for group_name, group_index in r.groupindex.items():
+                    if group_name != _INVALID_TRAILING_INPUT:
+                        regs = re_match.regs
+                        reg = regs[group_index]
+                        node = self._group_names_to_nodes[group_name]
+                        yield (node, reg)
+
+        return list(get_tuples())
+
+    def _nodes_to_values(self) -> List[Tuple[str, str, Tuple[int, int]]]:
+        """
+        Returns list of (Node, string_value) tuples.
+        """
+
+        def is_none(sl: Tuple[int, int]) -> bool:
+            return sl[0] == -1 and sl[1] == -1
+
+        def get(sl: Tuple[int, int]) -> str:
+            return self.string[sl[0] : sl[1]]
+
+        return [
+            (varname, get(slice), slice)
+            for varname, slice in self._nodes_to_regs()
+            if not is_none(slice)
+        ]
+
+    def _unescape(self, varname: str, value: str) -> str:
+        unwrapper = self._unescape_funcs.get(varname)
+        return unwrapper(value) if unwrapper else value
+
+    def variables(self) -> "Variables":
+        """
+        Returns :class:`Variables` instance.
+        """
+        return Variables(
+            [(k, self._unescape(k, v), sl) for k, v, sl in self._nodes_to_values()]
+        )
+
+    def trailing_input(self) -> Optional["MatchVariable"]:
+        """
+        Get the `MatchVariable` instance, representing trailing input, if there is any.
+        "Trailing input" is input at the end that does not match the grammar anymore, but
+        when this is removed from the end of the input, the input would be a valid string.
+        """
+        slices: List[Tuple[int, int]] = []
+
+        # Find all regex group for the name _INVALID_TRAILING_INPUT.
+        for r, re_match in self._re_matches:
+            for group_name, group_index in r.groupindex.items():
+                if group_name == _INVALID_TRAILING_INPUT:
+                    slices.append(re_match.regs[group_index])
+
+        # Take the smallest part. (Smaller trailing text means that a larger input has
+        # been matched, so that is better.)
+        if slices:
+            slice = (max(i[0] for i in slices), max(i[1] for i in slices))
+            value = self.string[slice[0] : slice[1]]
+            return MatchVariable("<trailing_input>", value, slice)
+        return None
+
+    def end_nodes(self) -> Iterable["MatchVariable"]:
+        """
+        Yields `MatchVariable` instances for all the nodes having their end
+        position at the end of the input string.
+        """
+        for varname, reg in self._nodes_to_regs():
+            # If this part goes until the end of the input string.
+            if reg[1] == len(self.string):
+                value = self._unescape(varname, self.string[reg[0] : reg[1]])
+                yield MatchVariable(varname, value, (reg[0], reg[1]))
+
+
+class Variables:
+    def __init__(self, tuples: List[Tuple[str, str, Tuple[int, int]]]) -> None:
+        #: List of (varname, value, slice) tuples.
+        self._tuples = tuples
+
+    def __repr__(self) -> str:
+        return "{}({})".format(
+            self.__class__.__name__,
+            ", ".join(f"{k}={v!r}" for k, v, _ in self._tuples),
+        )
+
+    def get(self, key: str, default: Optional[str] = None) -> Optional[str]:
+        items = self.getall(key)
+        return items[0] if items else default
+
+    def getall(self, key: str) -> List[str]:
+        return [v for k, v, _ in self._tuples if k == key]
+
+    def __getitem__(self, key: str) -> Optional[str]:
+        return self.get(key)
+
+    def __iter__(self) -> Iterator["MatchVariable"]:
+        """
+        Yield `MatchVariable` instances.
+        """
+        for varname, value, slice in self._tuples:
+            yield MatchVariable(varname, value, slice)
+
+
+class MatchVariable:
+    """
+    Represents a match of a variable in the grammar.
+
+    :param varname: (string) Name of the variable.
+    :param value: (string) Value of this variable.
+    :param slice: (start, stop) tuple, indicating the position of this variable
+                  in the input string.
+    """
+
+    def __init__(self, varname: str, value: str, slice: Tuple[int, int]) -> None:
+        self.varname = varname
+        self.value = value
+        self.slice = slice
+
+        self.start = self.slice[0]
+        self.stop = self.slice[1]
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.varname!r}, {self.value!r})"
+
+
+def compile(
+    expression: str,
+    escape_funcs: Optional[EscapeFuncDict] = None,
+    unescape_funcs: Optional[EscapeFuncDict] = None,
+) -> _CompiledGrammar:
+    """
+    Compile grammar (given as regex string), returning a `CompiledGrammar`
+    instance.
+    """
+    return _compile_from_parse_tree(
+        parse_regex(tokenize_regex(expression)),
+        escape_funcs=escape_funcs,
+        unescape_funcs=unescape_funcs,
+    )
+
+
+def _compile_from_parse_tree(
+    root_node: Node,
+    escape_funcs: Optional[EscapeFuncDict] = None,
+    unescape_funcs: Optional[EscapeFuncDict] = None,
+) -> _CompiledGrammar:
+    """
+    Compile grammar (given as parse tree), returning a `CompiledGrammar`
+    instance.
+    """
+    return _CompiledGrammar(
+        root_node, escape_funcs=escape_funcs, unescape_funcs=unescape_funcs
+    )
diff --git a/src/prompt_toolkit/contrib/regular_languages/completion.py b/src/prompt_toolkit/contrib/regular_languages/completion.py
new file mode 100644
index 0000000..3cebcc0
--- /dev/null
+++ b/src/prompt_toolkit/contrib/regular_languages/completion.py
@@ -0,0 +1,93 @@
+"""
+Completer for a regular grammar.
+"""
+from typing import Dict, Iterable, List
+
+from prompt_toolkit.completion import CompleteEvent, Completer, Completion
+from prompt_toolkit.document import Document
+
+from .compiler import Match, _CompiledGrammar
+
+__all__ = [
+    "GrammarCompleter",
+]
+
+
+class GrammarCompleter(Completer):
+    """
+    Completer which can be used for autocompletion according to variables in
+    the grammar. Each variable can have a different autocompleter.
+
+    :param compiled_grammar: `GrammarCompleter` instance.
+    :param completers: `dict` mapping variable names of the grammar to the
+                       `Completer` instances to be used for each variable.
+    """
+
+    def __init__(
+        self, compiled_grammar: _CompiledGrammar, completers: Dict[str, Completer]
+    ) -> None:
+
+        self.compiled_grammar = compiled_grammar
+        self.completers = completers
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        m = self.compiled_grammar.match_prefix(document.text_before_cursor)
+
+        if m:
+            completions = self._remove_duplicates(
+                self._get_completions_for_match(m, complete_event)
+            )
+
+            yield from completions
+
+    def _get_completions_for_match(
+        self, match: Match, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        """
+        Yield all the possible completions for this input string.
+        (The completer assumes that the cursor position was at the end of the
+        input string.)
+        """
+        for match_variable in match.end_nodes():
+            varname = match_variable.varname
+            start = match_variable.start
+
+            completer = self.completers.get(varname)
+
+            if completer:
+                text = match_variable.value
+
+                # Unwrap text.
+                unwrapped_text = self.compiled_grammar.unescape(varname, text)
+
+                # Create a document, for the completions API (text/cursor_position)
+                document = Document(unwrapped_text, len(unwrapped_text))
+
+                # Call completer
+                for completion in completer.get_completions(document, complete_event):
+                    new_text = (
+                        unwrapped_text[: len(text) + completion.start_position]
+                        + completion.text
+                    )
+
+                    # Wrap again.
+                    yield Completion(
+                        text=self.compiled_grammar.escape(varname, new_text),
+                        start_position=start - len(match.string),
+                        display=completion.display,
+                        display_meta=completion.display_meta,
+                    )
+
+    def _remove_duplicates(self, items: Iterable[Completion]) -> List[Completion]:
+        """
+        Remove duplicates, while keeping the order.
+        (Sometimes we have duplicates, because the there several matches of the
+        same grammar, each yielding similar completions.)
+        """
+        result: List[Completion] = []
+        for i in items:
+            if i not in result:
+                result.append(i)
+        return result
diff --git a/src/prompt_toolkit/contrib/regular_languages/lexer.py b/src/prompt_toolkit/contrib/regular_languages/lexer.py
new file mode 100644
index 0000000..1ddeede
--- /dev/null
+++ b/src/prompt_toolkit/contrib/regular_languages/lexer.py
@@ -0,0 +1,92 @@
+"""
+`GrammarLexer` is compatible with other lexers and can be used to highlight
+the input using a regular grammar with annotations.
+"""
+from typing import Callable, Dict, Optional
+
+from prompt_toolkit.document import Document
+from prompt_toolkit.formatted_text.base import StyleAndTextTuples
+from prompt_toolkit.formatted_text.utils import split_lines
+from prompt_toolkit.lexers import Lexer
+
+from .compiler import _CompiledGrammar
+
+__all__ = [
+    "GrammarLexer",
+]
+
+
+class GrammarLexer(Lexer):
+    """
+    Lexer which can be used for highlighting of fragments according to variables in the grammar.
+
+    (It does not actual lexing of the string, but it exposes an API, compatible
+    with the Pygments lexer class.)
+
+    :param compiled_grammar: Grammar as returned by the `compile()` function.
+    :param lexers: Dictionary mapping variable names of the regular grammar to
+                   the lexers that should be used for this part. (This can
+                   call other lexers recursively.) If you wish a part of the
+                   grammar to just get one fragment, use a
+                   `prompt_toolkit.lexers.SimpleLexer`.
+    """
+
+    def __init__(
+        self,
+        compiled_grammar: _CompiledGrammar,
+        default_style: str = "",
+        lexers: Optional[Dict[str, Lexer]] = None,
+    ) -> None:
+
+        self.compiled_grammar = compiled_grammar
+        self.default_style = default_style
+        self.lexers = lexers or {}
+
+    def _get_text_fragments(self, text: str) -> StyleAndTextTuples:
+        m = self.compiled_grammar.match_prefix(text)
+
+        if m:
+            characters: StyleAndTextTuples = [(self.default_style, c) for c in text]
+
+            for v in m.variables():
+                # If we have a `Lexer` instance for this part of the input.
+                # Tokenize recursively and apply tokens.
+                lexer = self.lexers.get(v.varname)
+
+                if lexer:
+                    document = Document(text[v.start : v.stop])
+                    lexer_tokens_for_line = lexer.lex_document(document)
+                    text_fragments: StyleAndTextTuples = []
+                    for i in range(len(document.lines)):
+                        text_fragments.extend(lexer_tokens_for_line(i))
+                        text_fragments.append(("", "\n"))
+                    if text_fragments:
+                        text_fragments.pop()
+
+                    i = v.start
+                    for t, s, *_ in text_fragments:
+                        for c in s:
+                            if characters[i][0] == self.default_style:
+                                characters[i] = (t, characters[i][1])
+                            i += 1
+
+            # Highlight trailing input.
+            trailing_input = m.trailing_input()
+            if trailing_input:
+                for i in range(trailing_input.start, trailing_input.stop):
+                    characters[i] = ("class:trailing-input", characters[i][1])
+
+            return characters
+        else:
+            return [("", text)]
+
+    def lex_document(self, document: Document) -> Callable[[int], StyleAndTextTuples]:
+        lines = list(split_lines(self._get_text_fragments(document.text)))
+
+        def get_line(lineno: int) -> StyleAndTextTuples:
+            try:
+                return lines[lineno]
+            except IndexError:
+                return []
+
+        return get_line
diff --git a/src/prompt_toolkit/contrib/regular_languages/regex_parser.py b/src/prompt_toolkit/contrib/regular_languages/regex_parser.py
new file mode 100644
index 0000000..87e39d4
--- /dev/null
+++ b/src/prompt_toolkit/contrib/regular_languages/regex_parser.py
@@ -0,0 +1,281 @@
+"""
+Parser for parsing a regular expression.
+Take a string representing a regular expression and return the root node of its
+parse tree.
+
+usage::
+
+    root_node = parse_regex('(hello|world)')
+
+Remarks:
+- The regex parser processes multiline, it ignores all whitespace and supports
+  multiple named groups with the same name and #-style comments.
+
+Limitations:
+- Lookahead is not supported.
+"""
+import re
+from typing import List, Optional
+
+__all__ = [
+    "Repeat",
+    "Variable",
+    "Regex",
+    "Lookahead",
+    "tokenize_regex",
+    "parse_regex",
+]
+
+
+class Node:
+    """
+    Base class for all the grammar nodes.
+    (You don't initialize this one.)
+    """
+
+    def __add__(self, other_node: "Node") -> "NodeSequence":
+        return NodeSequence([self, other_node])
+
+    def __or__(self, other_node: "Node") -> "AnyNode":
+        return AnyNode([self, other_node])
+
+
+class AnyNode(Node):
+    """
+    Union operation (OR operation) between several grammars. You don't
+    initialize this yourself, but it's a result of a "Grammar1 | Grammar2"
+    operation.
+    """
+
+    def __init__(self, children: List[Node]) -> None:
+        self.children = children
+
+    def __or__(self, other_node: Node) -> "AnyNode":
+        return AnyNode(self.children + [other_node])
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.children!r})"
+
+
+class NodeSequence(Node):
+    """
+    Concatenation operation of several grammars. You don't initialize this
+    yourself, but it's a result of a "Grammar1 + Grammar2" operation.
+    """
+
+    def __init__(self, children: List[Node]) -> None:
+        self.children = children
+
+    def __add__(self, other_node: Node) -> "NodeSequence":
+        return NodeSequence(self.children + [other_node])
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.children!r})"
+
+
+class Regex(Node):
+    """
+    Regular expression.
+    """
+
+    def __init__(self, regex: str) -> None:
+        re.compile(regex)  # Validate
+
+        self.regex = regex
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}(/{self.regex}/)"
+
+
+class Lookahead(Node):
+    """
+    Lookahead expression.
+    """
+
+    def __init__(self, childnode: Node, negative: bool = False) -> None:
+        self.childnode = childnode
+        self.negative = negative
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.childnode!r})"
+
+
+class Variable(Node):
+    """
+    Mark a variable in the regular grammar. This will be translated into a
+    named group. Each variable can have his own completer, validator, etc..
+
+    :param childnode: The grammar which is wrapped inside this variable.
+    :param varname: String.
+    """
+
+    def __init__(self, childnode: Node, varname: str = "") -> None:
+        self.childnode = childnode
+        self.varname = varname
+
+    def __repr__(self) -> str:
+        return "{}(childnode={!r}, varname={!r})".format(
+            self.__class__.__name__,
+            self.childnode,
+            self.varname,
+        )
+
+
+class Repeat(Node):
+    def __init__(
+        self,
+        childnode: Node,
+        min_repeat: int = 0,
+        max_repeat: Optional[int] = None,
+        greedy: bool = True,
+    ) -> None:
+        self.childnode = childnode
+        self.min_repeat = min_repeat
+        self.max_repeat = max_repeat
+        self.greedy = greedy
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}(childnode={self.childnode!r})"
+
+
+def tokenize_regex(input: str) -> List[str]:
+    """
+    Takes a string, representing a regular expression as input, and tokenizes
+    it.
+
+    :param input: string, representing a regular expression.
+    :returns: List of tokens.
+    """
+    # Regular expression for tokenizing other regular expressions.
+    p = re.compile(
+        r"""^(
+        \(\?P\<[a-zA-Z0-9_-]+\>  | # Start of named group.
+        \(\?#[^)]*\)             | # Comment
+        \(\?=                    | # Start of lookahead assertion
+        \(\?!                    | # Start of negative lookahead assertion
+        \(\?<=                   | # If preceded by.
+        \(\?<                    | # If not preceded by.
+        \(?:                     | # Start of group. (non capturing.)
+        \(                       | # Start of group.
+        \(?[iLmsux]              | # Flags.
+        \(?P=[a-zA-Z]+\)         | # Back reference to named group
+        \)                       | # End of group.
+        \{[^{}]*\}               | # Repetition
+        \*\? | \+\? | \?\?\      | # Non greedy repetition.
+        \* | \+ | \?             | # Repetition
+        \#.*\n                   | # Comment
+        \\. |
+
+        # Character group.
+        \[
+            ( [^\]\\]  |  \\.)*
+        \]                  |
+
+        [^(){}]             |
+        .
+    )""",
+        re.VERBOSE,
+    )
+
+    tokens = []
+
+    while input:
+        m = p.match(input)
+        if m:
+            token, input = input[: m.end()], input[m.end() :]
+            if not token.isspace():
+                tokens.append(token)
+        else:
+            raise Exception("Could not tokenize input regex.")
+
+    return tokens
+
+
+def parse_regex(regex_tokens: List[str]) -> Node:
+    """
+    Takes a list of tokens from the tokenizer, and returns a parse tree.
+    """
+    # We add a closing brace because that represents the final pop of the stack.
+    tokens: List[str] = [")"] + regex_tokens[::-1]
+
+    def wrap(lst: List[Node]) -> Node:
+        """Turn list into sequence when it contains several items."""
+        if len(lst) == 1:
+            return lst[0]
+        else:
+            return NodeSequence(lst)
+
+    def _parse() -> Node:
+        or_list: List[List[Node]] = []
+        result: List[Node] = []
+
+        def wrapped_result() -> Node:
+            if or_list == []:
+                return wrap(result)
+            else:
+                or_list.append(result)
+                return AnyNode([wrap(i) for i in or_list])
+
+        while tokens:
+            t = tokens.pop()
+
+            if t.startswith("(?P<"):
+                variable = Variable(_parse(), varname=t[4:-1])
+                result.append(variable)
+
+            elif t in ("*", "*?"):
+                greedy = t == "*"
+                result[-1] = Repeat(result[-1], greedy=greedy)
+
+            elif t in ("+", "+?"):
+                greedy = t == "+"
+                result[-1] = Repeat(result[-1], min_repeat=1, greedy=greedy)
+
+            elif t in ("?", "??"):
+                if result == []:
+                    raise Exception("Nothing to repeat." + repr(tokens))
+                else:
+                    greedy = t == "?"
+                    result[-1] = Repeat(
+                        result[-1], min_repeat=0, max_repeat=1, greedy=greedy
+                    )
+
+            elif t == "|":
+                or_list.append(result)
+                result = []
+
+            elif t in ("(", "(?:"):
+                result.append(_parse())
+
+            elif t == "(?!":
+                result.append(Lookahead(_parse(), negative=True))
+
+            elif t == "(?=":
+                result.append(Lookahead(_parse(), negative=False))
+
+            elif t == ")":
+                return wrapped_result()
+
+            elif t.startswith("#"):
+                pass
+
+            elif t.startswith("{"):
+                # TODO: implement!
+                raise Exception(f"{t}-style repetition not yet supported")
+
+            elif t.startswith("(?"):
+                raise Exception("%r not supported" % t)
+
+            elif t.isspace():
+                pass
+            else:
+                result.append(Regex(t))
+
+        raise Exception("Expecting ')' token")
+
+    result = _parse()
+
+    if len(tokens) != 0:
+        raise Exception("Unmatched parentheses.")
+    else:
+        return result
diff --git a/src/prompt_toolkit/contrib/regular_languages/validation.py b/src/prompt_toolkit/contrib/regular_languages/validation.py
new file mode 100644
index 0000000..71d3434
--- /dev/null
+++ b/src/prompt_toolkit/contrib/regular_languages/validation.py
@@ -0,0 +1,60 @@
+"""
+Validator for a regular language.
+"""
+from typing import Dict
+
+from prompt_toolkit.document import Document
+from prompt_toolkit.validation import ValidationError, Validator
+
+from .compiler import _CompiledGrammar
+
+__all__ = [
+    "GrammarValidator",
+]
+
+
+class GrammarValidator(Validator):
+    """
+    Validator which can be used for validation according to variables in
+    the grammar. Each variable can have its own validator.
+
+    :param compiled_grammar: `GrammarCompleter` instance.
+    :param validators: `dict` mapping variable names of the grammar to the
+                       `Validator` instances to be used for each variable.
+    """
+
+    def __init__(
+        self, compiled_grammar: _CompiledGrammar, validators: Dict[str, Validator]
+    ) -> None:
+
+        self.compiled_grammar = compiled_grammar
+        self.validators = validators
+
+    def validate(self, document: Document) -> None:
+        # Parse input document.
+        # We use `match`, not `match_prefix`, because for validation, we want
+        # the actual, unambiguous interpretation of the input.
+        m = self.compiled_grammar.match(document.text)
+
+        if m:
+            for v in m.variables():
+                validator = self.validators.get(v.varname)
+
+                if validator:
+                    # Unescape text.
+                    unwrapped_text = self.compiled_grammar.unescape(v.varname, v.value)
+
+                    # Create a document, for the completions API (text/cursor_position)
+                    inner_document = Document(unwrapped_text, len(unwrapped_text))
+
+                    try:
+                        validator.validate(inner_document)
+                    except ValidationError as e:
+                        raise ValidationError(
+                            cursor_position=v.start + e.cursor_position,
+                            message=e.message,
+                        ) from e
+        else:
+            raise ValidationError(
+                cursor_position=len(document.text), message="Invalid command"
+            )
diff --git a/src/prompt_toolkit/contrib/ssh/__init__.py b/src/prompt_toolkit/contrib/ssh/__init__.py
new file mode 100644
index 0000000..a895ca2
--- /dev/null
+++ b/src/prompt_toolkit/contrib/ssh/__init__.py
@@ -0,0 +1,6 @@
+from .server import PromptToolkitSSHServer, PromptToolkitSSHSession
+
+__all__ = [
+    "PromptToolkitSSHSession",
+    "PromptToolkitSSHServer",
+]
diff --git a/src/prompt_toolkit/contrib/ssh/server.py b/src/prompt_toolkit/contrib/ssh/server.py
new file mode 100644
index 0000000..793d259
--- /dev/null
+++ b/src/prompt_toolkit/contrib/ssh/server.py
@@ -0,0 +1,175 @@
+"""
+Utility for running a prompt_toolkit application in an asyncssh server.
+"""
+import asyncio
+import traceback
+from typing import Any, Awaitable, Callable, Optional, TextIO, cast
+
+import asyncssh
+
+from prompt_toolkit.application.current import AppSession, create_app_session
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.eventloop import get_event_loop
+from prompt_toolkit.input import PipeInput, create_pipe_input
+from prompt_toolkit.output.vt100 import Vt100_Output
+
+__all__ = ["PromptToolkitSSHSession", "PromptToolkitSSHServer"]
+
+
+class PromptToolkitSSHSession(asyncssh.SSHServerSession):  # type: ignore
+    def __init__(
+        self,
+        interact: Callable[["PromptToolkitSSHSession"], Awaitable[None]],
+        *,
+        enable_cpr: bool,
+    ) -> None:
+        self.interact = interact
+        self.enable_cpr = enable_cpr
+        self.interact_task: Optional[asyncio.Task[None]] = None
+        self._chan: Optional[Any] = None
+        self.app_session: Optional[AppSession] = None
+
+        # PipInput object, for sending input in the CLI.
+        # (This is something that we can use in the prompt_toolkit event loop,
+        # but still write date in manually.)
+        self._input: Optional[PipeInput] = None
+        self._output: Optional[Vt100_Output] = None
+
+        # Output object. Don't render to the real stdout, but write everything
+        # in the SSH channel.
+        class Stdout:
+            def write(s, data: str) -> None:
+                try:
+                    if self._chan is not None:
+                        self._chan.write(data.replace("\n", "\r\n"))
+                except BrokenPipeError:
+                    pass  # Channel not open for sending.
+
+            def isatty(s) -> bool:
+                return True
+
+            def flush(s) -> None:
+                pass
+
+            @property
+            def encoding(s) -> str:
+                assert self._chan is not None
+                return str(self._chan._orig_chan.get_encoding()[0])
+
+        self.stdout = cast(TextIO, Stdout())
+
+    def _get_size(self) -> Size:
+        """
+        Callable that returns the current `Size`, required by Vt100_Output.
+        """
+        if self._chan is None:
+            return Size(rows=20, columns=79)
+        else:
+            width, height, pixwidth, pixheight = self._chan.get_terminal_size()
+            return Size(rows=height, columns=width)
+
+    def connection_made(self, chan: Any) -> None:
+        self._chan = chan
+
+    def shell_requested(self) -> bool:
+        return True
+
+    def session_started(self) -> None:
+        self.interact_task = get_event_loop().create_task(self._interact())
+
+    async def _interact(self) -> None:
+        if self._chan is None:
+            # Should not happen.
+            raise Exception("`_interact` called before `connection_made`.")
+
+        if hasattr(self._chan, "set_line_mode") and self._chan._editor is not None:
+            # Disable the line editing provided by asyncssh. Prompt_toolkit
+            # provides the line editing.
+            self._chan.set_line_mode(False)
+
+        term = self._chan.get_terminal_type()
+
+        self._output = Vt100_Output(
+            self.stdout, self._get_size, term=term, enable_cpr=self.enable_cpr
+        )
+
+        with create_pipe_input() as self._input:
+            with create_app_session(input=self._input, output=self._output) as session:
+                self.app_session = session
+                try:
+                    await self.interact(self)
+                except BaseException:
+                    traceback.print_exc()
+                finally:
+                    # Close the connection.
+                    self._chan.close()
+                    self._input.close()
+
+    def terminal_size_changed(
+        self, width: int, height: int, pixwidth: object, pixheight: object
+    ) -> None:
+        # Send resize event to the current application.
+        if self.app_session and self.app_session.app:
+            self.app_session.app._on_resize()
+
+    def data_received(self, data: str, datatype: object) -> None:
+        if self._input is None:
+            # Should not happen.
+            return
+
+        self._input.send_text(data)
+
+
+class PromptToolkitSSHServer(asyncssh.SSHServer):
+    """
+    Run a prompt_toolkit application over an asyncssh server.
+
+    This takes one argument, an `interact` function, which is called for each
+    connection. This should be an asynchronous function that runs the
+    prompt_toolkit applications. This function runs in an `AppSession`, which
+    means that we can have multiple UI interactions concurrently.
+
+    Example usage:
+
+    .. code:: python
+
+        async def interact(ssh_session: PromptToolkitSSHSession) -> None:
+            await yes_no_dialog("my title", "my text").run_async()
+
+            prompt_session = PromptSession()
+            text = await prompt_session.prompt_async("Type something: ")
+            print_formatted_text('You said: ', text)
+
+        server = PromptToolkitSSHServer(interact=interact)
+        loop = get_event_loop()
+        loop.run_until_complete(
+            asyncssh.create_server(
+                lambda: MySSHServer(interact),
+                "",
+                port,
+                server_host_keys=["/etc/ssh/..."],
+            )
+        )
+        loop.run_forever()
+
+    :param enable_cpr: When `True`, the default, try to detect whether the SSH
+        client runs in a terminal that responds to "cursor position requests".
+        That way, we can properly determine how much space there is available
+        for the UI (especially for drop down menus) to render.
+    """
+
+    def __init__(
+        self,
+        interact: Callable[[PromptToolkitSSHSession], Awaitable[None]],
+        *,
+        enable_cpr: bool = True,
+    ) -> None:
+        self.interact = interact
+        self.enable_cpr = enable_cpr
+
+    def begin_auth(self, username: str) -> bool:
+        # No authentication.
+        return False
+
+    def session_requested(self) -> PromptToolkitSSHSession:
+        return PromptToolkitSSHSession(self.interact, enable_cpr=self.enable_cpr)
diff --git a/src/prompt_toolkit/contrib/telnet/__init__.py b/src/prompt_toolkit/contrib/telnet/__init__.py
new file mode 100644
index 0000000..b29f7d2
--- /dev/null
+++ b/src/prompt_toolkit/contrib/telnet/__init__.py
@@ -0,0 +1,5 @@
+from .server import TelnetServer
+
+__all__ = [
+    "TelnetServer",
+]
diff --git a/src/prompt_toolkit/contrib/telnet/log.py b/src/prompt_toolkit/contrib/telnet/log.py
new file mode 100644
index 0000000..24487ab
--- /dev/null
+++ b/src/prompt_toolkit/contrib/telnet/log.py
@@ -0,0 +1,10 @@
+"""
+Python logger for the telnet server.
+"""
+import logging
+
+logger = logging.getLogger(__package__)
+
+__all__ = [
+    "logger",
+]
diff --git a/src/prompt_toolkit/contrib/telnet/protocol.py b/src/prompt_toolkit/contrib/telnet/protocol.py
new file mode 100644
index 0000000..68f3639
--- /dev/null
+++ b/src/prompt_toolkit/contrib/telnet/protocol.py
@@ -0,0 +1,207 @@
+"""
+Parser for the Telnet protocol. (Not a complete implementation of the telnet
+specification, but sufficient for a command line interface.)
+
+Inspired by `Twisted.conch.telnet`.
+"""
+import struct
+from typing import Callable, Generator
+
+from .log import logger
+
+__all__ = [
+    "TelnetProtocolParser",
+]
+
+
+def int2byte(number: int) -> bytes:
+    return bytes((number,))
+
+
+# Telnet constants.
+NOP = int2byte(0)
+SGA = int2byte(3)
+
+IAC = int2byte(255)
+DO = int2byte(253)
+DONT = int2byte(254)
+LINEMODE = int2byte(34)
+SB = int2byte(250)
+WILL = int2byte(251)
+WONT = int2byte(252)
+MODE = int2byte(1)
+SE = int2byte(240)
+ECHO = int2byte(1)
+NAWS = int2byte(31)
+LINEMODE = int2byte(34)
+SUPPRESS_GO_AHEAD = int2byte(3)
+
+TTYPE = int2byte(24)
+SEND = int2byte(1)
+IS = int2byte(0)
+
+DM = int2byte(242)
+BRK = int2byte(243)
+IP = int2byte(244)
+AO = int2byte(245)
+AYT = int2byte(246)
+EC = int2byte(247)
+EL = int2byte(248)
+GA = int2byte(249)
+
+
+class TelnetProtocolParser:
+    """
+    Parser for the Telnet protocol.
+    Usage::
+
+        def data_received(data):
+            print(data)
+
+        def size_received(rows, columns):
+            print(rows, columns)
+
+        p = TelnetProtocolParser(data_received, size_received)
+        p.feed(binary_data)
+    """
+
+    def __init__(
+        self,
+        data_received_callback: Callable[[bytes], None],
+        size_received_callback: Callable[[int, int], None],
+        ttype_received_callback: Callable[[str], None],
+    ) -> None:
+
+        self.data_received_callback = data_received_callback
+        self.size_received_callback = size_received_callback
+        self.ttype_received_callback = ttype_received_callback
+
+        self._parser = self._parse_coroutine()
+        self._parser.send(None)  # type: ignore
+
+    def received_data(self, data: bytes) -> None:
+        self.data_received_callback(data)
+
+    def do_received(self, data: bytes) -> None:
+        """Received telnet DO command."""
+        logger.info("DO %r", data)
+
+    def dont_received(self, data: bytes) -> None:
+        """Received telnet DONT command."""
+        logger.info("DONT %r", data)
+
+    def will_received(self, data: bytes) -> None:
+        """Received telnet WILL command."""
+        logger.info("WILL %r", data)
+
+    def wont_received(self, data: bytes) -> None:
+        """Received telnet WONT command."""
+        logger.info("WONT %r", data)
+
+    def command_received(self, command: bytes, data: bytes) -> None:
+        if command == DO:
+            self.do_received(data)
+
+        elif command == DONT:
+            self.dont_received(data)
+
+        elif command == WILL:
+            self.will_received(data)
+
+        elif command == WONT:
+            self.wont_received(data)
+
+        else:
+            logger.info("command received %r %r", command, data)
+
+    def naws(self, data: bytes) -> None:
+        """
+        Received NAWS. (Window dimensions.)
+        """
+        if len(data) == 4:
+            # NOTE: the first parameter of struct.unpack should be
+            # a 'str' object. Both on Py2/py3. This crashes on OSX
+            # otherwise.
+            columns, rows = struct.unpack("!HH", data)
+            self.size_received_callback(rows, columns)
+        else:
+            logger.warning("Wrong number of NAWS bytes")
+
+    def ttype(self, data: bytes) -> None:
+        """
+        Received terminal type.
+        """
+        subcmd, data = data[0:1], data[1:]
+        if subcmd == IS:
+            ttype = data.decode("ascii")
+            self.ttype_received_callback(ttype)
+        else:
+            logger.warning("Received a non-IS terminal type Subnegotiation")
+
+    def negotiate(self, data: bytes) -> None:
+        """
+        Got negotiate data.
+        """
+        command, payload = data[0:1], data[1:]
+
+        if command == NAWS:
+            self.naws(payload)
+        elif command == TTYPE:
+            self.ttype(payload)
+        else:
+            logger.info("Negotiate (%r got bytes)", len(data))
+
+    def _parse_coroutine(self) -> Generator[None, bytes, None]:
+        """
+        Parser state machine.
+        Every 'yield' expression returns the next byte.
+        """
+        while True:
+            d = yield
+
+            if d == int2byte(0):
+                pass  # NOP
+
+            # Go to state escaped.
+            elif d == IAC:
+                d2 = yield
+
+                if d2 == IAC:
+                    self.received_data(d2)
+
+                # Handle simple commands.
+                elif d2 in (NOP, DM, BRK, IP, AO, AYT, EC, EL, GA):
+                    self.command_received(d2, b"")
+
+                # Handle IAC-[DO/DONT/WILL/WONT] commands.
+                elif d2 in (DO, DONT, WILL, WONT):
+                    d3 = yield
+                    self.command_received(d2, d3)
+
+                # Subnegotiation
+                elif d2 == SB:
+                    # Consume everything until next IAC-SE
+                    data = []
+
+                    while True:
+                        d3 = yield
+
+                        if d3 == IAC:
+                            d4 = yield
+                            if d4 == SE:
+                                break
+                            else:
+                                data.append(d4)
+                        else:
+                            data.append(d3)
+
+                    self.negotiate(b"".join(data))
+            else:
+                self.received_data(d)
+
+    def feed(self, data: bytes) -> None:
+        """
+        Feed data to the parser.
+        """
+        for b in data:
+            self._parser.send(int2byte(b))
diff --git a/src/prompt_toolkit/contrib/telnet/server.py b/src/prompt_toolkit/contrib/telnet/server.py
new file mode 100644
index 0000000..11e4e0c
--- /dev/null
+++ b/src/prompt_toolkit/contrib/telnet/server.py
@@ -0,0 +1,385 @@
+"""
+Telnet server.
+"""
+import asyncio
+import socket
+import sys
+from typing import Any, Awaitable, Callable, List, Optional, Set, TextIO, Tuple, cast
+
+from prompt_toolkit.application.current import create_app_session, get_app
+from prompt_toolkit.application.run_in_terminal import run_in_terminal
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.eventloop import get_event_loop
+from prompt_toolkit.formatted_text import AnyFormattedText, to_formatted_text
+from prompt_toolkit.input import PipeInput, create_pipe_input
+from prompt_toolkit.output.vt100 import Vt100_Output
+from prompt_toolkit.renderer import print_formatted_text as print_formatted_text
+from prompt_toolkit.styles import BaseStyle, DummyStyle
+
+from .log import logger
+from .protocol import (
+    DO,
+    ECHO,
+    IAC,
+    LINEMODE,
+    MODE,
+    NAWS,
+    SB,
+    SE,
+    SEND,
+    SUPPRESS_GO_AHEAD,
+    TTYPE,
+    WILL,
+    TelnetProtocolParser,
+)
+
+if sys.version_info >= (3, 7):
+    import contextvars  # Requires Python3.7!
+else:
+    contextvars: Any = None
+
+__all__ = [
+    "TelnetServer",
+]
+
+
+def int2byte(number: int) -> bytes:
+    return bytes((number,))
+
+
+def _initialize_telnet(connection: socket.socket) -> None:
+    logger.info("Initializing telnet connection")
+
+    # Iac Do Linemode
+    connection.send(IAC + DO + LINEMODE)
+
+    # Suppress Go Ahead. (This seems important for Putty to do correct echoing.)
+    # This will allow bi-directional operation.
+    connection.send(IAC + WILL + SUPPRESS_GO_AHEAD)
+
+    # Iac sb
+    connection.send(IAC + SB + LINEMODE + MODE + int2byte(0) + IAC + SE)
+
+    # IAC Will Echo
+    connection.send(IAC + WILL + ECHO)
+
+    # Negotiate window size
+    connection.send(IAC + DO + NAWS)
+
+    # Negotiate terminal type
+    # Assume the client will accept the negociation with `IAC +  WILL + TTYPE`
+    connection.send(IAC + DO + TTYPE)
+
+    # We can then select the first terminal type supported by the client,
+    # which is generally the best type the client supports
+    # The client should reply with a `IAC + SB  + TTYPE + IS + ttype + IAC + SE`
+    connection.send(IAC + SB + TTYPE + SEND + IAC + SE)
+
+
+class _ConnectionStdout:
+    """
+    Wrapper around socket which provides `write` and `flush` methods for the
+    Vt100_Output output.
+    """
+
+    def __init__(self, connection: socket.socket, encoding: str) -> None:
+        self._encoding = encoding
+        self._connection = connection
+        self._errors = "strict"
+        self._buffer: List[bytes] = []
+        self._closed = False
+
+    def write(self, data: str) -> None:
+        data = data.replace("\n", "\r\n")
+        self._buffer.append(data.encode(self._encoding, errors=self._errors))
+        self.flush()
+
+    def isatty(self) -> bool:
+        return True
+
+    def flush(self) -> None:
+        try:
+            if not self._closed:
+                self._connection.send(b"".join(self._buffer))
+        except OSError as e:
+            logger.warning("Couldn't send data over socket: %s" % e)
+
+        self._buffer = []
+
+    def close(self) -> None:
+        self._closed = True
+
+    @property
+    def encoding(self) -> str:
+        return self._encoding
+
+    @property
+    def errors(self) -> str:
+        return self._errors
+
+
+class TelnetConnection:
+    """
+    Class that represents one Telnet connection.
+    """
+
+    def __init__(
+        self,
+        conn: socket.socket,
+        addr: Tuple[str, int],
+        interact: Callable[["TelnetConnection"], Awaitable[None]],
+        server: "TelnetServer",
+        encoding: str,
+        style: Optional[BaseStyle],
+        vt100_input: PipeInput,
+        enable_cpr: bool = True,
+    ) -> None:
+
+        self.conn = conn
+        self.addr = addr
+        self.interact = interact
+        self.server = server
+        self.encoding = encoding
+        self.style = style
+        self._closed = False
+        self._ready = asyncio.Event()
+        self.vt100_input = vt100_input
+        self.enable_cpr = enable_cpr
+        self.vt100_output: Optional[Vt100_Output] = None
+
+        # Create "Output" object.
+        self.size = Size(rows=40, columns=79)
+
+        # Initialize.
+        _initialize_telnet(conn)
+
+        # Create output.
+        def get_size() -> Size:
+            return self.size
+
+        self.stdout = cast(TextIO, _ConnectionStdout(conn, encoding=encoding))
+
+        def data_received(data: bytes) -> None:
+            """TelnetProtocolParser 'data_received' callback"""
+            self.vt100_input.send_bytes(data)
+
+        def size_received(rows: int, columns: int) -> None:
+            """TelnetProtocolParser 'size_received' callback"""
+            self.size = Size(rows=rows, columns=columns)
+            if self.vt100_output is not None and self.context:
+                self.context.run(lambda: get_app()._on_resize())
+
+        def ttype_received(ttype: str) -> None:
+            """TelnetProtocolParser 'ttype_received' callback"""
+            self.vt100_output = Vt100_Output(
+                self.stdout, get_size, term=ttype, enable_cpr=enable_cpr
+            )
+            self._ready.set()
+
+        self.parser = TelnetProtocolParser(data_received, size_received, ttype_received)
+        self.context: Optional[contextvars.Context] = None
+
+    async def run_application(self) -> None:
+        """
+        Run application.
+        """
+
+        def handle_incoming_data() -> None:
+            data = self.conn.recv(1024)
+            if data:
+                self.feed(data)
+            else:
+                # Connection closed by client.
+                logger.info("Connection closed by client. %r %r" % self.addr)
+                self.close()
+
+        # Add reader.
+        loop = get_event_loop()
+        loop.add_reader(self.conn, handle_incoming_data)
+
+        try:
+            # Wait for v100_output to be properly instantiated
+            await self._ready.wait()
+            with create_app_session(input=self.vt100_input, output=self.vt100_output):
+                self.context = contextvars.copy_context()
+                await self.interact(self)
+        finally:
+            self.close()
+
+    def feed(self, data: bytes) -> None:
+        """
+        Handler for incoming data. (Called by TelnetServer.)
+        """
+        self.parser.feed(data)
+
+    def close(self) -> None:
+        """
+        Closed by client.
+        """
+        if not self._closed:
+            self._closed = True
+
+            self.vt100_input.close()
+            get_event_loop().remove_reader(self.conn)
+            self.conn.close()
+            self.stdout.close()
+
+    def send(self, formatted_text: AnyFormattedText) -> None:
+        """
+        Send text to the client.
+        """
+        if self.vt100_output is None:
+            return
+        formatted_text = to_formatted_text(formatted_text)
+        print_formatted_text(
+            self.vt100_output, formatted_text, self.style or DummyStyle()
+        )
+
+    def send_above_prompt(self, formatted_text: AnyFormattedText) -> None:
+        """
+        Send text to the client.
+        This is asynchronous, returns a `Future`.
+        """
+        formatted_text = to_formatted_text(formatted_text)
+        return self._run_in_terminal(lambda: self.send(formatted_text))
+
+    def _run_in_terminal(self, func: Callable[[], None]) -> None:
+        # Make sure that when an application was active for this connection,
+        # that we print the text above the application.
+        if self.context:
+            self.context.run(run_in_terminal, func)  # type: ignore
+        else:
+            raise RuntimeError("Called _run_in_terminal outside `run_application`.")
+
+    def erase_screen(self) -> None:
+        """
+        Erase the screen and move the cursor to the top.
+        """
+        if self.vt100_output is None:
+            return
+        self.vt100_output.erase_screen()
+        self.vt100_output.cursor_goto(0, 0)
+        self.vt100_output.flush()
+
+
+async def _dummy_interact(connection: TelnetConnection) -> None:
+    pass
+
+
+class TelnetServer:
+    """
+    Telnet server implementation.
+    """
+
+    def __init__(
+        self,
+        host: str = "127.0.0.1",
+        port: int = 23,
+        interact: Callable[[TelnetConnection], Awaitable[None]] = _dummy_interact,
+        encoding: str = "utf-8",
+        style: Optional[BaseStyle] = None,
+        enable_cpr: bool = True,
+    ) -> None:
+
+        self.host = host
+        self.port = port
+        self.interact = interact
+        self.encoding = encoding
+        self.style = style
+        self.enable_cpr = enable_cpr
+        self._application_tasks: List[asyncio.Task[None]] = []
+
+        self.connections: Set[TelnetConnection] = set()
+        self._listen_socket: Optional[socket.socket] = None
+
+    @classmethod
+    def _create_socket(cls, host: str, port: int) -> socket.socket:
+        # Create and bind socket
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        s.bind((host, port))
+
+        s.listen(4)
+        return s
+
+    def start(self) -> None:
+        """
+        Start the telnet server.
+        Don't forget to call `loop.run_forever()` after doing this.
+        """
+        self._listen_socket = self._create_socket(self.host, self.port)
+        logger.info(
+            "Listening for telnet connections on %s port %r", self.host, self.port
+        )
+
+        get_event_loop().add_reader(self._listen_socket, self._accept)
+
+    async def stop(self) -> None:
+        if self._listen_socket:
+            get_event_loop().remove_reader(self._listen_socket)
+            self._listen_socket.close()
+
+        # Wait for all applications to finish.
+        for t in self._application_tasks:
+            t.cancel()
+
+        # (This is similar to
+        # `Application.cancel_and_wait_for_background_tasks`. We wait for the
+        # background tasks to complete, but don't propagate exceptions, because
+        # we can't use `ExceptionGroup` yet.)
+        if len(self._application_tasks) > 0:
+            await asyncio.wait(
+                self._application_tasks, timeout=None, return_when=asyncio.ALL_COMPLETED
+            )
+
+    def _accept(self) -> None:
+        """
+        Accept new incoming connection.
+        """
+        if self._listen_socket is None:
+            return  # Should not happen. `_accept` is called after `start`.
+
+        conn, addr = self._listen_socket.accept()
+        logger.info("New connection %r %r", *addr)
+
+        # Run application for this connection.
+        async def run() -> None:
+            try:
+                with create_pipe_input() as vt100_input:
+                    connection = TelnetConnection(
+                        conn,
+                        addr,
+                        self.interact,
+                        self,
+                        encoding=self.encoding,
+                        style=self.style,
+                        vt100_input=vt100_input,
+                        enable_cpr=self.enable_cpr,
+                    )
+                    self.connections.add(connection)
+
+                    logger.info("Starting interaction %r %r", *addr)
+                    try:
+                        await connection.run_application()
+                    finally:
+                        self.connections.remove(connection)
+                        logger.info("Stopping interaction %r %r", *addr)
+            except EOFError:
+                # Happens either when the connection is closed by the client
+                # (e.g., when the user types 'control-]', then 'quit' in the
+                # telnet client) or when the user types control-d in a prompt
+                # and this is not handled by the interact function.
+                logger.info("Unhandled EOFError in telnet application.")
+            except KeyboardInterrupt:
+                # Unhandled control-c propagated by a prompt.
+                logger.info("Unhandled KeyboardInterrupt in telnet application.")
+            except BaseException as e:
+                print("Got %s" % type(e).__name__, e)
+                import traceback
+
+                traceback.print_exc()
+            finally:
+                self._application_tasks.remove(task)
+
+        task = get_event_loop().create_task(run())
+        self._application_tasks.append(task)
diff --git a/src/prompt_toolkit/cursor_shapes.py b/src/prompt_toolkit/cursor_shapes.py
new file mode 100644
index 0000000..59172f2
--- /dev/null
+++ b/src/prompt_toolkit/cursor_shapes.py
@@ -0,0 +1,102 @@
+from abc import ABC, abstractmethod
+from enum import Enum
+from typing import TYPE_CHECKING, Any, Callable, Union
+
+from prompt_toolkit.enums import EditingMode
+from prompt_toolkit.key_binding.vi_state import InputMode
+
+if TYPE_CHECKING:
+    from .application import Application
+
+__all__ = [
+    "CursorShape",
+    "CursorShapeConfig",
+    "SimpleCursorShapeConfig",
+    "ModalCursorShapeConfig",
+    "DynamicCursorShapeConfig",
+    "to_cursor_shape_config",
+]
+
+
+class CursorShape(Enum):
+    # Default value that should tell the output implementation to never send
+    # cursor shape escape sequences. This is the default right now, because
+    # before this `CursorShape` functionality was introduced into
+    # prompt_toolkit itself, people had workarounds to send cursor shapes
+    # escapes into the terminal, by monkey patching some of prompt_toolkit's
+    # internals. We don't want the default prompt_toolkit implemetation to
+    # interfere with that. E.g., IPython patches the `ViState.input_mode`
+    # property. See: https://github.com/ipython/ipython/pull/13501/files
+    _NEVER_CHANGE = "_NEVER_CHANGE"
+
+    BLOCK = "BLOCK"
+    BEAM = "BEAM"
+    UNDERLINE = "UNDERLINE"
+    BLINKING_BLOCK = "BLINKING_BLOCK"
+    BLINKING_BEAM = "BLINKING_BEAM"
+    BLINKING_UNDERLINE = "BLINKING_UNDERLINE"
+
+
+class CursorShapeConfig(ABC):
+    @abstractmethod
+    def get_cursor_shape(self, application: "Application[Any]") -> CursorShape:
+        """
+        Return the cursor shape to be used in the current state.
+        """
+
+
+AnyCursorShapeConfig = Union[CursorShape, CursorShapeConfig, None]
+
+
+class SimpleCursorShapeConfig(CursorShapeConfig):
+    """
+    Always show the given cursor shape.
+    """
+
+    def __init__(self, cursor_shape: CursorShape = CursorShape._NEVER_CHANGE) -> None:
+        self.cursor_shape = cursor_shape
+
+    def get_cursor_shape(self, application: "Application[Any]") -> CursorShape:
+        return self.cursor_shape
+
+
+class ModalCursorShapeConfig(CursorShapeConfig):
+    """
+    Show cursor shape according to the current input mode.
+    """
+
+    def get_cursor_shape(self, application: "Application[Any]") -> CursorShape:
+        if application.editing_mode == EditingMode.VI:
+            if application.vi_state.input_mode == InputMode.INSERT:
+                return CursorShape.BEAM
+            if application.vi_state.input_mode == InputMode.REPLACE:
+                return CursorShape.UNDERLINE
+
+        # Default
+        return CursorShape.BLOCK
+
+
+class DynamicCursorShapeConfig(CursorShapeConfig):
+    def __init__(
+        self, get_cursor_shape_config: Callable[[], AnyCursorShapeConfig]
+    ) -> None:
+        self.get_cursor_shape_config = get_cursor_shape_config
+
+    def get_cursor_shape(self, application: "Application[Any]") -> CursorShape:
+        return to_cursor_shape_config(self.get_cursor_shape_config()).get_cursor_shape(
+            application
+        )
+
+
+def to_cursor_shape_config(value: AnyCursorShapeConfig) -> CursorShapeConfig:
+    """
+    Take a `CursorShape` instance or `CursorShapeConfig` and turn it into a
+    `CursorShapeConfig`.
+    """
+    if value is None:
+        return SimpleCursorShapeConfig()
+
+    if isinstance(value, CursorShape):
+        return SimpleCursorShapeConfig(value)
+
+    return value
diff --git a/src/prompt_toolkit/data_structures.py b/src/prompt_toolkit/data_structures.py
new file mode 100644
index 0000000..d031acf
--- /dev/null
+++ b/src/prompt_toolkit/data_structures.py
@@ -0,0 +1,16 @@
+from typing import NamedTuple
+
+__all__ = [
+    "Point",
+    "Size",
+]
+
+
+class Point(NamedTuple):
+    x: int
+    y: int
+
+
+class Size(NamedTuple):
+    rows: int
+    columns: int
diff --git a/src/prompt_toolkit/document.py b/src/prompt_toolkit/document.py
new file mode 100644
index 0000000..1984155
--- /dev/null
+++ b/src/prompt_toolkit/document.py
@@ -0,0 +1,1190 @@
+"""
+The `Document` that implements all the text operations/querying.
+"""
+import bisect
+import re
+import string
+import weakref
+from typing import (
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    NoReturn,
+    Optional,
+    Pattern,
+    Tuple,
+    cast,
+)
+
+from .clipboard import ClipboardData
+from .filters import vi_mode
+from .selection import PasteMode, SelectionState, SelectionType
+
+__all__ = [
+    "Document",
+]
+
+
+# Regex for finding "words" in documents. (We consider a group of alnum
+# characters a word, but also a group of special characters a word, as long as
+# it doesn't contain a space.)
+# (This is a 'word' in Vi.)
+_FIND_WORD_RE = re.compile(r"([a-zA-Z0-9_]+|[^a-zA-Z0-9_\s]+)")
+_FIND_CURRENT_WORD_RE = re.compile(r"^([a-zA-Z0-9_]+|[^a-zA-Z0-9_\s]+)")
+_FIND_CURRENT_WORD_INCLUDE_TRAILING_WHITESPACE_RE = re.compile(
+    r"^(([a-zA-Z0-9_]+|[^a-zA-Z0-9_\s]+)\s*)"
+)
+
+# Regex for finding "WORDS" in documents.
+# (This is a 'WORD in Vi.)
+_FIND_BIG_WORD_RE = re.compile(r"([^\s]+)")
+_FIND_CURRENT_BIG_WORD_RE = re.compile(r"^([^\s]+)")
+_FIND_CURRENT_BIG_WORD_INCLUDE_TRAILING_WHITESPACE_RE = re.compile(r"^([^\s]+\s*)")
+
+# Share the Document._cache between all Document instances.
+# (Document instances are considered immutable. That means that if another
+# `Document` is constructed with the same text, it should have the same
+# `_DocumentCache`.)
+_text_to_document_cache: Dict[str, "_DocumentCache"] = cast(
+    Dict[str, "_DocumentCache"],
+    weakref.WeakValueDictionary(),  # Maps document.text to DocumentCache instance.
+)
+
+
+class _ImmutableLineList(List[str]):
+    """
+    Some protection for our 'lines' list, which is assumed to be immutable in the cache.
+    (Useful for detecting obvious bugs.)
+    """
+
+    def _error(self, *a: object, **kw: object) -> NoReturn:
+        raise NotImplementedError("Attempt to modify an immutable list.")
+
+    __setitem__ = _error  # type: ignore
+    append = _error
+    clear = _error
+    extend = _error
+    insert = _error
+    pop = _error
+    remove = _error
+    reverse = _error
+    sort = _error  # type: ignore
+
+
+class _DocumentCache:
+    def __init__(self) -> None:
+        #: List of lines for the Document text.
+        self.lines: Optional[_ImmutableLineList] = None
+
+        #: List of index positions, pointing to the start of all the lines.
+        self.line_indexes: Optional[List[int]] = None
+
+
+class Document:
+    """
+    This is a immutable class around the text and cursor position, and contains
+    methods for querying this data, e.g. to give the text before the cursor.
+
+    This class is usually instantiated by a :class:`~prompt_toolkit.buffer.Buffer`
+    object, and accessed as the `document` property of that class.
+
+    :param text: string
+    :param cursor_position: int
+    :param selection: :class:`.SelectionState`
+    """
+
+    __slots__ = ("_text", "_cursor_position", "_selection", "_cache")
+
+    def __init__(
+        self,
+        text: str = "",
+        cursor_position: Optional[int] = None,
+        selection: Optional[SelectionState] = None,
+    ) -> None:
+
+        # Check cursor position. It can also be right after the end. (Where we
+        # insert text.)
+        assert cursor_position is None or cursor_position <= len(text), AssertionError(
+            f"cursor_position={cursor_position!r}, len_text={len(text)!r}"
+        )
+
+        # By default, if no cursor position was given, make sure to put the
+        # cursor position is at the end of the document. This is what makes
+        # sense in most places.
+        if cursor_position is None:
+            cursor_position = len(text)
+
+        # Keep these attributes private. A `Document` really has to be
+        # considered to be immutable, because otherwise the caching will break
+        # things. Because of that, we wrap these into read-only properties.
+        self._text = text
+        self._cursor_position = cursor_position
+        self._selection = selection
+
+        # Cache for lines/indexes. (Shared with other Document instances that
+        # contain the same text.
+        try:
+            self._cache = _text_to_document_cache[self.text]
+        except KeyError:
+            self._cache = _DocumentCache()
+            _text_to_document_cache[self.text] = self._cache
+
+        # XX: For some reason, above, we can't use 'WeakValueDictionary.setdefault'.
+        #     This fails in Pypy3. `self._cache` becomes None, because that's what
+        #     'setdefault' returns.
+        # self._cache = _text_to_document_cache.setdefault(self.text, _DocumentCache())
+        # assert self._cache
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.text!r}, {self.cursor_position!r})"
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, Document):
+            return False
+
+        return (
+            self.text == other.text
+            and self.cursor_position == other.cursor_position
+            and self.selection == other.selection
+        )
+
+    @property
+    def text(self) -> str:
+        "The document text."
+        return self._text
+
+    @property
+    def cursor_position(self) -> int:
+        "The document cursor position."
+        return self._cursor_position
+
+    @property
+    def selection(self) -> Optional[SelectionState]:
+        ":class:`.SelectionState` object."
+        return self._selection
+
+    @property
+    def current_char(self) -> str:
+        """Return character under cursor or an empty string."""
+        return self._get_char_relative_to_cursor(0) or ""
+
+    @property
+    def char_before_cursor(self) -> str:
+        """Return character before the cursor or an empty string."""
+        return self._get_char_relative_to_cursor(-1) or ""
+
+    @property
+    def text_before_cursor(self) -> str:
+        return self.text[: self.cursor_position :]
+
+    @property
+    def text_after_cursor(self) -> str:
+        return self.text[self.cursor_position :]
+
+    @property
+    def current_line_before_cursor(self) -> str:
+        """Text from the start of the line until the cursor."""
+        _, _, text = self.text_before_cursor.rpartition("\n")
+        return text
+
+    @property
+    def current_line_after_cursor(self) -> str:
+        """Text from the cursor until the end of the line."""
+        text, _, _ = self.text_after_cursor.partition("\n")
+        return text
+
+    @property
+    def lines(self) -> List[str]:
+        """
+        Array of all the lines.
+        """
+        # Cache, because this one is reused very often.
+        if self._cache.lines is None:
+            self._cache.lines = _ImmutableLineList(self.text.split("\n"))
+
+        return self._cache.lines
+
+    @property
+    def _line_start_indexes(self) -> List[int]:
+        """
+        Array pointing to the start indexes of all the lines.
+        """
+        # Cache, because this is often reused. (If it is used, it's often used
+        # many times. And this has to be fast for editing big documents!)
+        if self._cache.line_indexes is None:
+            # Create list of line lengths.
+            line_lengths = map(len, self.lines)
+
+            # Calculate cumulative sums.
+            indexes = [0]
+            append = indexes.append
+            pos = 0
+
+            for line_length in line_lengths:
+                pos += line_length + 1
+                append(pos)
+
+            # Remove the last item. (This is not a new line.)
+            if len(indexes) > 1:
+                indexes.pop()
+
+            self._cache.line_indexes = indexes
+
+        return self._cache.line_indexes
+
+    @property
+    def lines_from_current(self) -> List[str]:
+        """
+        Array of the lines starting from the current line, until the last line.
+        """
+        return self.lines[self.cursor_position_row :]
+
+    @property
+    def line_count(self) -> int:
+        r"""Return the number of lines in this document. If the document ends
+        with a trailing \n, that counts as the beginning of a new line."""
+        return len(self.lines)
+
+    @property
+    def current_line(self) -> str:
+        """Return the text on the line where the cursor is. (when the input
+        consists of just one line, it equals `text`."""
+        return self.current_line_before_cursor + self.current_line_after_cursor
+
+    @property
+    def leading_whitespace_in_current_line(self) -> str:
+        """The leading whitespace in the left margin of the current line."""
+        current_line = self.current_line
+        length = len(current_line) - len(current_line.lstrip())
+        return current_line[:length]
+
+    def _get_char_relative_to_cursor(self, offset: int = 0) -> str:
+        """
+        Return character relative to cursor position, or empty string
+        """
+        try:
+            return self.text[self.cursor_position + offset]
+        except IndexError:
+            return ""
+
+    @property
+    def on_first_line(self) -> bool:
+        """
+        True when we are at the first line.
+        """
+        return self.cursor_position_row == 0
+
+    @property
+    def on_last_line(self) -> bool:
+        """
+        True when we are at the last line.
+        """
+        return self.cursor_position_row == self.line_count - 1
+
+    @property
+    def cursor_position_row(self) -> int:
+        """
+        Current row. (0-based.)
+        """
+        row, _ = self._find_line_start_index(self.cursor_position)
+        return row
+
+    @property
+    def cursor_position_col(self) -> int:
+        """
+        Current column. (0-based.)
+        """
+        # (Don't use self.text_before_cursor to calculate this. Creating
+        # substrings and doing rsplit is too expensive for getting the cursor
+        # position.)
+        _, line_start_index = self._find_line_start_index(self.cursor_position)
+        return self.cursor_position - line_start_index
+
+    def _find_line_start_index(self, index: int) -> Tuple[int, int]:
+        """
+        For the index of a character at a certain line, calculate the index of
+        the first character on that line.
+
+        Return (row, index) tuple.
+        """
+        indexes = self._line_start_indexes
+
+        pos = bisect.bisect_right(indexes, index) - 1
+        return pos, indexes[pos]
+
+    def translate_index_to_position(self, index: int) -> Tuple[int, int]:
+        """
+        Given an index for the text, return the corresponding (row, col) tuple.
+        (0-based. Returns (0, 0) for index=0.)
+        """
+        # Find start of this line.
+        row, row_index = self._find_line_start_index(index)
+        col = index - row_index
+
+        return row, col
+
+    def translate_row_col_to_index(self, row: int, col: int) -> int:
+        """
+        Given a (row, col) tuple, return the corresponding index.
+        (Row and col params are 0-based.)
+
+        Negative row/col values are turned into zero.
+        """
+        try:
+            result = self._line_start_indexes[row]
+            line = self.lines[row]
+        except IndexError:
+            if row < 0:
+                result = self._line_start_indexes[0]
+                line = self.lines[0]
+            else:
+                result = self._line_start_indexes[-1]
+                line = self.lines[-1]
+
+        result += max(0, min(col, len(line)))
+
+        # Keep in range. (len(self.text) is included, because the cursor can be
+        # right after the end of the text as well.)
+        result = max(0, min(result, len(self.text)))
+        return result
+
+    @property
+    def is_cursor_at_the_end(self) -> bool:
+        """True when the cursor is at the end of the text."""
+        return self.cursor_position == len(self.text)
+
+    @property
+    def is_cursor_at_the_end_of_line(self) -> bool:
+        """True when the cursor is at the end of this line."""
+        return self.current_char in ("\n", "")
+
+    def has_match_at_current_position(self, sub: str) -> bool:
+        """
+        `True` when this substring is found at the cursor position.
+        """
+        return self.text.find(sub, self.cursor_position) == self.cursor_position
+
+    def find(
+        self,
+        sub: str,
+        in_current_line: bool = False,
+        include_current_position: bool = False,
+        ignore_case: bool = False,
+        count: int = 1,
+    ) -> Optional[int]:
+        """
+        Find `text` after the cursor, return position relative to the cursor
+        position. Return `None` if nothing was found.
+
+        :param count: Find the n-th occurrence.
+        """
+        assert isinstance(ignore_case, bool)
+
+        if in_current_line:
+            text = self.current_line_after_cursor
+        else:
+            text = self.text_after_cursor
+
+        if not include_current_position:
+            if len(text) == 0:
+                return None  # (Otherwise, we always get a match for the empty string.)
+            else:
+                text = text[1:]
+
+        flags = re.IGNORECASE if ignore_case else 0
+        iterator = re.finditer(re.escape(sub), text, flags)
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    if include_current_position:
+                        return match.start(0)
+                    else:
+                        return match.start(0) + 1
+        except StopIteration:
+            pass
+        return None
+
+    def find_all(self, sub: str, ignore_case: bool = False) -> List[int]:
+        """
+        Find all occurrences of the substring. Return a list of absolute
+        positions in the document.
+        """
+        flags = re.IGNORECASE if ignore_case else 0
+        return [a.start() for a in re.finditer(re.escape(sub), self.text, flags)]
+
+    def find_backwards(
+        self,
+        sub: str,
+        in_current_line: bool = False,
+        ignore_case: bool = False,
+        count: int = 1,
+    ) -> Optional[int]:
+        """
+        Find `text` before the cursor, return position relative to the cursor
+        position. Return `None` if nothing was found.
+
+        :param count: Find the n-th occurrence.
+        """
+        if in_current_line:
+            before_cursor = self.current_line_before_cursor[::-1]
+        else:
+            before_cursor = self.text_before_cursor[::-1]
+
+        flags = re.IGNORECASE if ignore_case else 0
+        iterator = re.finditer(re.escape(sub[::-1]), before_cursor, flags)
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    return -match.start(0) - len(sub)
+        except StopIteration:
+            pass
+        return None
+
+    def get_word_before_cursor(
+        self, WORD: bool = False, pattern: Optional[Pattern[str]] = None
+    ) -> str:
+        """
+        Give the word before the cursor.
+        If we have whitespace before the cursor this returns an empty string.
+
+        :param pattern: (None or compiled regex). When given, use this regex
+            pattern.
+        """
+        if self._is_word_before_cursor_complete(WORD=WORD, pattern=pattern):
+            # Space before the cursor or no text before cursor.
+            return ""
+
+        text_before_cursor = self.text_before_cursor
+        start = self.find_start_of_previous_word(WORD=WORD, pattern=pattern) or 0
+
+        return text_before_cursor[len(text_before_cursor) + start :]
+
+    def _is_word_before_cursor_complete(
+        self, WORD: bool = False, pattern: Optional[Pattern[str]] = None
+    ) -> bool:
+        if pattern:
+            return self.find_start_of_previous_word(WORD=WORD, pattern=pattern) is None
+        else:
+            return (
+                self.text_before_cursor == "" or self.text_before_cursor[-1:].isspace()
+            )
+
+    def find_start_of_previous_word(
+        self, count: int = 1, WORD: bool = False, pattern: Optional[Pattern[str]] = None
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the start
+        of the previous word. Return `None` if nothing was found.
+
+        :param pattern: (None or compiled regex). When given, use this regex
+            pattern.
+        """
+        assert not (WORD and pattern)
+
+        # Reverse the text before the cursor, in order to do an efficient
+        # backwards search.
+        text_before_cursor = self.text_before_cursor[::-1]
+
+        if pattern:
+            regex = pattern
+        elif WORD:
+            regex = _FIND_BIG_WORD_RE
+        else:
+            regex = _FIND_WORD_RE
+
+        iterator = regex.finditer(text_before_cursor)
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    return -match.end(0)
+        except StopIteration:
+            pass
+        return None
+
+    def find_boundaries_of_current_word(
+        self,
+        WORD: bool = False,
+        include_leading_whitespace: bool = False,
+        include_trailing_whitespace: bool = False,
+    ) -> Tuple[int, int]:
+        """
+        Return the relative boundaries (startpos, endpos) of the current word under the
+        cursor. (This is at the current line, because line boundaries obviously
+        don't belong to any word.)
+        If not on a word, this returns (0,0)
+        """
+        text_before_cursor = self.current_line_before_cursor[::-1]
+        text_after_cursor = self.current_line_after_cursor
+
+        def get_regex(include_whitespace: bool) -> Pattern[str]:
+            return {
+                (False, False): _FIND_CURRENT_WORD_RE,
+                (False, True): _FIND_CURRENT_WORD_INCLUDE_TRAILING_WHITESPACE_RE,
+                (True, False): _FIND_CURRENT_BIG_WORD_RE,
+                (True, True): _FIND_CURRENT_BIG_WORD_INCLUDE_TRAILING_WHITESPACE_RE,
+            }[(WORD, include_whitespace)]
+
+        match_before = get_regex(include_leading_whitespace).search(text_before_cursor)
+        match_after = get_regex(include_trailing_whitespace).search(text_after_cursor)
+
+        # When there is a match before and after, and we're not looking for
+        # WORDs, make sure that both the part before and after the cursor are
+        # either in the [a-zA-Z_] alphabet or not. Otherwise, drop the part
+        # before the cursor.
+        if not WORD and match_before and match_after:
+            c1 = self.text[self.cursor_position - 1]
+            c2 = self.text[self.cursor_position]
+            alphabet = string.ascii_letters + "0123456789_"
+
+            if (c1 in alphabet) != (c2 in alphabet):
+                match_before = None
+
+        return (
+            -match_before.end(1) if match_before else 0,
+            match_after.end(1) if match_after else 0,
+        )
+
+    def get_word_under_cursor(self, WORD: bool = False) -> str:
+        """
+        Return the word, currently below the cursor.
+        This returns an empty string when the cursor is on a whitespace region.
+        """
+        start, end = self.find_boundaries_of_current_word(WORD=WORD)
+        return self.text[self.cursor_position + start : self.cursor_position + end]
+
+    def find_next_word_beginning(
+        self, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the start
+        of the next word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_previous_word_beginning(count=-count, WORD=WORD)
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterator = regex.finditer(self.text_after_cursor)
+
+        try:
+            for i, match in enumerate(iterator):
+                # Take first match, unless it's the word on which we're right now.
+                if i == 0 and match.start(1) == 0:
+                    count += 1
+
+                if i + 1 == count:
+                    return match.start(1)
+        except StopIteration:
+            pass
+        return None
+
+    def find_next_word_ending(
+        self, include_current_position: bool = False, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the end
+        of the next word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_previous_word_ending(count=-count, WORD=WORD)
+
+        if include_current_position:
+            text = self.text_after_cursor
+        else:
+            text = self.text_after_cursor[1:]
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterable = regex.finditer(text)
+
+        try:
+            for i, match in enumerate(iterable):
+                if i + 1 == count:
+                    value = match.end(1)
+
+                    if include_current_position:
+                        return value
+                    else:
+                        return value + 1
+
+        except StopIteration:
+            pass
+        return None
+
+    def find_previous_word_beginning(
+        self, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the start
+        of the previous word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_next_word_beginning(count=-count, WORD=WORD)
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterator = regex.finditer(self.text_before_cursor[::-1])
+
+        try:
+            for i, match in enumerate(iterator):
+                if i + 1 == count:
+                    return -match.end(1)
+        except StopIteration:
+            pass
+        return None
+
+    def find_previous_word_ending(
+        self, count: int = 1, WORD: bool = False
+    ) -> Optional[int]:
+        """
+        Return an index relative to the cursor position pointing to the end
+        of the previous word. Return `None` if nothing was found.
+        """
+        if count < 0:
+            return self.find_next_word_ending(count=-count, WORD=WORD)
+
+        text_before_cursor = self.text_after_cursor[:1] + self.text_before_cursor[::-1]
+
+        regex = _FIND_BIG_WORD_RE if WORD else _FIND_WORD_RE
+        iterator = regex.finditer(text_before_cursor)
+
+        try:
+            for i, match in enumerate(iterator):
+                # Take first match, unless it's the word on which we're right now.
+                if i == 0 and match.start(1) == 0:
+                    count += 1
+
+                if i + 1 == count:
+                    return -match.start(1) + 1
+        except StopIteration:
+            pass
+        return None
+
+    def find_next_matching_line(
+        self, match_func: Callable[[str], bool], count: int = 1
+    ) -> Optional[int]:
+        """
+        Look downwards for empty lines.
+        Return the line index, relative to the current line.
+        """
+        result = None
+
+        for index, line in enumerate(self.lines[self.cursor_position_row + 1 :]):
+            if match_func(line):
+                result = 1 + index
+                count -= 1
+
+            if count == 0:
+                break
+
+        return result
+
+    def find_previous_matching_line(
+        self, match_func: Callable[[str], bool], count: int = 1
+    ) -> Optional[int]:
+        """
+        Look upwards for empty lines.
+        Return the line index, relative to the current line.
+        """
+        result = None
+
+        for index, line in enumerate(self.lines[: self.cursor_position_row][::-1]):
+            if match_func(line):
+                result = -1 - index
+                count -= 1
+
+            if count == 0:
+                break
+
+        return result
+
+    def get_cursor_left_position(self, count: int = 1) -> int:
+        """
+        Relative position for cursor left.
+        """
+        if count < 0:
+            return self.get_cursor_right_position(-count)
+
+        return -min(self.cursor_position_col, count)
+
+    def get_cursor_right_position(self, count: int = 1) -> int:
+        """
+        Relative position for cursor_right.
+        """
+        if count < 0:
+            return self.get_cursor_left_position(-count)
+
+        return min(count, len(self.current_line_after_cursor))
+
+    def get_cursor_up_position(
+        self, count: int = 1, preferred_column: Optional[int] = None
+    ) -> int:
+        """
+        Return the relative cursor position (character index) where we would be if the
+        user pressed the arrow-up button.
+
+        :param preferred_column: When given, go to this column instead of
+                                 staying at the current column.
+        """
+        assert count >= 1
+        column = (
+            self.cursor_position_col if preferred_column is None else preferred_column
+        )
+
+        return (
+            self.translate_row_col_to_index(
+                max(0, self.cursor_position_row - count), column
+            )
+            - self.cursor_position
+        )
+
+    def get_cursor_down_position(
+        self, count: int = 1, preferred_column: Optional[int] = None
+    ) -> int:
+        """
+        Return the relative cursor position (character index) where we would be if the
+        user pressed the arrow-down button.
+
+        :param preferred_column: When given, go to this column instead of
+                                 staying at the current column.
+        """
+        assert count >= 1
+        column = (
+            self.cursor_position_col if preferred_column is None else preferred_column
+        )
+
+        return (
+            self.translate_row_col_to_index(self.cursor_position_row + count, column)
+            - self.cursor_position
+        )
+
+    def find_enclosing_bracket_right(
+        self, left_ch: str, right_ch: str, end_pos: Optional[int] = None
+    ) -> Optional[int]:
+        """
+        Find the right bracket enclosing current position. Return the relative
+        position to the cursor position.
+
+        When `end_pos` is given, don't look past the position.
+        """
+        if self.current_char == right_ch:
+            return 0
+
+        if end_pos is None:
+            end_pos = len(self.text)
+        else:
+            end_pos = min(len(self.text), end_pos)
+
+        stack = 1
+
+        # Look forward.
+        for i in range(self.cursor_position + 1, end_pos):
+            c = self.text[i]
+
+            if c == left_ch:
+                stack += 1
+            elif c == right_ch:
+                stack -= 1
+
+            if stack == 0:
+                return i - self.cursor_position
+
+        return None
+
+    def find_enclosing_bracket_left(
+        self, left_ch: str, right_ch: str, start_pos: Optional[int] = None
+    ) -> Optional[int]:
+        """
+        Find the left bracket enclosing current position. Return the relative
+        position to the cursor position.
+
+        When `start_pos` is given, don't look past the position.
+        """
+        if self.current_char == left_ch:
+            return 0
+
+        if start_pos is None:
+            start_pos = 0
+        else:
+            start_pos = max(0, start_pos)
+
+        stack = 1
+
+        # Look backward.
+        for i in range(self.cursor_position - 1, start_pos - 1, -1):
+            c = self.text[i]
+
+            if c == right_ch:
+                stack += 1
+            elif c == left_ch:
+                stack -= 1
+
+            if stack == 0:
+                return i - self.cursor_position
+
+        return None
+
+    def find_matching_bracket_position(
+        self, start_pos: Optional[int] = None, end_pos: Optional[int] = None
+    ) -> int:
+        """
+        Return relative cursor position of matching [, (, { or < bracket.
+
+        When `start_pos` or `end_pos` are given. Don't look past the positions.
+        """
+
+        # Look for a match.
+        for pair in "()", "[]", "{}", "<>":
+            A = pair[0]
+            B = pair[1]
+            if self.current_char == A:
+                return self.find_enclosing_bracket_right(A, B, end_pos=end_pos) or 0
+            elif self.current_char == B:
+                return self.find_enclosing_bracket_left(A, B, start_pos=start_pos) or 0
+
+        return 0
+
+    def get_start_of_document_position(self) -> int:
+        """Relative position for the start of the document."""
+        return -self.cursor_position
+
+    def get_end_of_document_position(self) -> int:
+        """Relative position for the end of the document."""
+        return len(self.text) - self.cursor_position
+
+    def get_start_of_line_position(self, after_whitespace: bool = False) -> int:
+        """Relative position for the start of this line."""
+        if after_whitespace:
+            current_line = self.current_line
+            return (
+                len(current_line)
+                - len(current_line.lstrip())
+                - self.cursor_position_col
+            )
+        else:
+            return -len(self.current_line_before_cursor)
+
+    def get_end_of_line_position(self) -> int:
+        """Relative position for the end of this line."""
+        return len(self.current_line_after_cursor)
+
+    def last_non_blank_of_current_line_position(self) -> int:
+        """
+        Relative position for the last non blank character of this line.
+        """
+        return len(self.current_line.rstrip()) - self.cursor_position_col - 1
+
+    def get_column_cursor_position(self, column: int) -> int:
+        """
+        Return the relative cursor position for this column at the current
+        line. (It will stay between the boundaries of the line in case of a
+        larger number.)
+        """
+        line_length = len(self.current_line)
+        current_column = self.cursor_position_col
+        column = max(0, min(line_length, column))
+
+        return column - current_column
+
+    def selection_range(
+        self,
+    ) -> Tuple[
+        int, int
+    ]:  # XXX: shouldn't this return `None` if there is no selection???
+        """
+        Return (from, to) tuple of the selection.
+        start and end position are included.
+
+        This doesn't take the selection type into account. Use
+        `selection_ranges` instead.
+        """
+        if self.selection:
+            from_, to = sorted(
+                [self.cursor_position, self.selection.original_cursor_position]
+            )
+        else:
+            from_, to = self.cursor_position, self.cursor_position
+
+        return from_, to
+
+    def selection_ranges(self) -> Iterable[Tuple[int, int]]:
+        """
+        Return a list of `(from, to)` tuples for the selection or none if
+        nothing was selected. The upper boundary is not included.
+
+        This will yield several (from, to) tuples in case of a BLOCK selection.
+        This will return zero ranges, like (8,8) for empty lines in a block
+        selection.
+        """
+        if self.selection:
+            from_, to = sorted(
+                [self.cursor_position, self.selection.original_cursor_position]
+            )
+
+            if self.selection.type == SelectionType.BLOCK:
+                from_line, from_column = self.translate_index_to_position(from_)
+                to_line, to_column = self.translate_index_to_position(to)
+                from_column, to_column = sorted([from_column, to_column])
+                lines = self.lines
+
+                if vi_mode():
+                    to_column += 1
+
+                for l in range(from_line, to_line + 1):
+                    line_length = len(lines[l])
+
+                    if from_column <= line_length:
+                        yield (
+                            self.translate_row_col_to_index(l, from_column),
+                            self.translate_row_col_to_index(
+                                l, min(line_length, to_column)
+                            ),
+                        )
+            else:
+                # In case of a LINES selection, go to the start/end of the lines.
+                if self.selection.type == SelectionType.LINES:
+                    from_ = max(0, self.text.rfind("\n", 0, from_) + 1)
+
+                    if self.text.find("\n", to) >= 0:
+                        to = self.text.find("\n", to)
+                    else:
+                        to = len(self.text) - 1
+
+                # In Vi mode, the upper boundary is always included. For Emacs,
+                # that's not the case.
+                if vi_mode():
+                    to += 1
+
+                yield from_, to
+
+    def selection_range_at_line(self, row: int) -> Optional[Tuple[int, int]]:
+        """
+        If the selection spans a portion of the given line, return a (from, to) tuple.
+
+        The returned upper boundary is not included in the selection, so
+        `(0, 0)` is an empty selection.  `(0, 1)`, is a one character selection.
+
+        Returns None if the selection doesn't cover this line at all.
+        """
+        if self.selection:
+            line = self.lines[row]
+
+            row_start = self.translate_row_col_to_index(row, 0)
+            row_end = self.translate_row_col_to_index(row, len(line))
+
+            from_, to = sorted(
+                [self.cursor_position, self.selection.original_cursor_position]
+            )
+
+            # Take the intersection of the current line and the selection.
+            intersection_start = max(row_start, from_)
+            intersection_end = min(row_end, to)
+
+            if intersection_start <= intersection_end:
+                if self.selection.type == SelectionType.LINES:
+                    intersection_start = row_start
+                    intersection_end = row_end
+
+                elif self.selection.type == SelectionType.BLOCK:
+                    _, col1 = self.translate_index_to_position(from_)
+                    _, col2 = self.translate_index_to_position(to)
+                    col1, col2 = sorted([col1, col2])
+
+                    if col1 > len(line):
+                        return None  # Block selection doesn't cross this line.
+
+                    intersection_start = self.translate_row_col_to_index(row, col1)
+                    intersection_end = self.translate_row_col_to_index(row, col2)
+
+                _, from_column = self.translate_index_to_position(intersection_start)
+                _, to_column = self.translate_index_to_position(intersection_end)
+
+                # In Vi mode, the upper boundary is always included. For Emacs
+                # mode, that's not the case.
+                if vi_mode():
+                    to_column += 1
+
+                return from_column, to_column
+        return None
+
+    def cut_selection(self) -> Tuple["Document", ClipboardData]:
+        """
+        Return a (:class:`.Document`, :class:`.ClipboardData`) tuple, where the
+        document represents the new document when the selection is cut, and the
+        clipboard data, represents whatever has to be put on the clipboard.
+        """
+        if self.selection:
+            cut_parts = []
+            remaining_parts = []
+            new_cursor_position = self.cursor_position
+
+            last_to = 0
+            for from_, to in self.selection_ranges():
+                if last_to == 0:
+                    new_cursor_position = from_
+
+                remaining_parts.append(self.text[last_to:from_])
+                cut_parts.append(self.text[from_:to])
+                last_to = to
+
+            remaining_parts.append(self.text[last_to:])
+
+            cut_text = "\n".join(cut_parts)
+            remaining_text = "".join(remaining_parts)
+
+            # In case of a LINES selection, don't include the trailing newline.
+            if self.selection.type == SelectionType.LINES and cut_text.endswith("\n"):
+                cut_text = cut_text[:-1]
+
+            return (
+                Document(text=remaining_text, cursor_position=new_cursor_position),
+                ClipboardData(cut_text, self.selection.type),
+            )
+        else:
+            return self, ClipboardData("")
+
+    def paste_clipboard_data(
+        self,
+        data: ClipboardData,
+        paste_mode: PasteMode = PasteMode.EMACS,
+        count: int = 1,
+    ) -> "Document":
+        """
+        Return a new :class:`.Document` instance which contains the result if
+        we would paste this data at the current cursor position.
+
+        :param paste_mode: Where to paste. (Before/after/emacs.)
+        :param count: When >1, Paste multiple times.
+        """
+        before = paste_mode == PasteMode.VI_BEFORE
+        after = paste_mode == PasteMode.VI_AFTER
+
+        if data.type == SelectionType.CHARACTERS:
+            if after:
+                new_text = (
+                    self.text[: self.cursor_position + 1]
+                    + data.text * count
+                    + self.text[self.cursor_position + 1 :]
+                )
+            else:
+                new_text = (
+                    self.text_before_cursor + data.text * count + self.text_after_cursor
+                )
+
+            new_cursor_position = self.cursor_position + len(data.text) * count
+            if before:
+                new_cursor_position -= 1
+
+        elif data.type == SelectionType.LINES:
+            l = self.cursor_position_row
+            if before:
+                lines = self.lines[:l] + [data.text] * count + self.lines[l:]
+                new_text = "\n".join(lines)
+                new_cursor_position = len("".join(self.lines[:l])) + l
+            else:
+                lines = self.lines[: l + 1] + [data.text] * count + self.lines[l + 1 :]
+                new_cursor_position = len("".join(self.lines[: l + 1])) + l + 1
+                new_text = "\n".join(lines)
+
+        elif data.type == SelectionType.BLOCK:
+            lines = self.lines[:]
+            start_line = self.cursor_position_row
+            start_column = self.cursor_position_col + (0 if before else 1)
+
+            for i, line in enumerate(data.text.split("\n")):
+                index = i + start_line
+                if index >= len(lines):
+                    lines.append("")
+
+                lines[index] = lines[index].ljust(start_column)
+                lines[index] = (
+                    lines[index][:start_column]
+                    + line * count
+                    + lines[index][start_column:]
+                )
+
+            new_text = "\n".join(lines)
+            new_cursor_position = self.cursor_position + (0 if before else 1)
+
+        return Document(text=new_text, cursor_position=new_cursor_position)
+
+    def empty_line_count_at_the_end(self) -> int:
+        """
+        Return number of empty lines at the end of the document.
+        """
+        count = 0
+        for line in self.lines[::-1]:
+            if not line or line.isspace():
+                count += 1
+            else:
+                break
+
+        return count
+
+    def start_of_paragraph(self, count: int = 1, before: bool = False) -> int:
+        """
+        Return the start of the current paragraph. (Relative cursor position.)
+        """
+
+        def match_func(text: str) -> bool:
+            return not text or text.isspace()
+
+        line_index = self.find_previous_matching_line(
+            match_func=match_func, count=count
+        )
+
+        if line_index:
+            add = 0 if before else 1
+            return min(0, self.get_cursor_up_position(count=-line_index) + add)
+        else:
+            return -self.cursor_position
+
+    def end_of_paragraph(self, count: int = 1, after: bool = False) -> int:
+        """
+        Return the end of the current paragraph. (Relative cursor position.)
+        """
+
+        def match_func(text: str) -> bool:
+            return not text or text.isspace()
+
+        line_index = self.find_next_matching_line(match_func=match_func, count=count)
+
+        if line_index:
+            add = 0 if after else 1
+            return max(0, self.get_cursor_down_position(count=line_index) - add)
+        else:
+            return len(self.text_after_cursor)
+
+    # Modifiers.
+
+    def insert_after(self, text: str) -> "Document":
+        """
+        Create a new document, with this text inserted after the buffer.
+        It keeps selection ranges and cursor position in sync.
+        """
+        return Document(
+            text=self.text + text,
+            cursor_position=self.cursor_position,
+            selection=self.selection,
+        )
+
+    def insert_before(self, text: str) -> "Document":
+        """
+        Create a new document, with this text inserted before the buffer.
+        It keeps selection ranges and cursor position in sync.
+        """
+        selection_state = self.selection
+
+        if selection_state:
+            selection_state = SelectionState(
+                original_cursor_position=selection_state.original_cursor_position
+                + len(text),
+                type=selection_state.type,
+            )
+
+        return Document(
+            text=text + self.text,
+            cursor_position=self.cursor_position + len(text),
+            selection=selection_state,
+        )
diff --git a/src/prompt_toolkit/enums.py b/src/prompt_toolkit/enums.py
new file mode 100644
index 0000000..4f496e6
--- /dev/null
+++ b/src/prompt_toolkit/enums.py
@@ -0,0 +1,17 @@
+from enum import Enum
+
+
+class EditingMode(Enum):
+    # The set of key bindings that is active.
+    VI = "VI"
+    EMACS = "EMACS"
+
+
+#: Name of the search buffer.
+SEARCH_BUFFER = "SEARCH_BUFFER"
+
+#: Name of the default buffer.
+DEFAULT_BUFFER = "DEFAULT_BUFFER"
+
+#: Name of the system buffer.
+SYSTEM_BUFFER = "SYSTEM_BUFFER"
diff --git a/src/prompt_toolkit/eventloop/__init__.py b/src/prompt_toolkit/eventloop/__init__.py
new file mode 100644
index 0000000..e92e7a2
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/__init__.py
@@ -0,0 +1,29 @@
+from .async_generator import aclosing, generator_to_async_generator
+from .inputhook import (
+    InputHookContext,
+    InputHookSelector,
+    new_eventloop_with_inputhook,
+    set_eventloop_with_inputhook,
+)
+from .utils import (
+    call_soon_threadsafe,
+    get_event_loop,
+    get_traceback_from_context,
+    run_in_executor_with_context,
+)
+
+__all__ = [
+    # Async generator
+    "generator_to_async_generator",
+    "aclosing",
+    # Utils.
+    "run_in_executor_with_context",
+    "call_soon_threadsafe",
+    "get_traceback_from_context",
+    "get_event_loop",
+    # Inputhooks.
+    "new_eventloop_with_inputhook",
+    "set_eventloop_with_inputhook",
+    "InputHookSelector",
+    "InputHookContext",
+]
diff --git a/src/prompt_toolkit/eventloop/async_context_manager.py b/src/prompt_toolkit/eventloop/async_context_manager.py
new file mode 100644
index 0000000..3914616
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/async_context_manager.py
@@ -0,0 +1,132 @@
+"""
+@asynccontextmanager code, copied from Python 3.7's contextlib.
+For usage in Python 3.6.
+Types have been added to this file, just enough to make Mypy happy.
+"""
+# mypy: allow-untyped-defs
+import abc
+from functools import wraps
+from typing import AsyncContextManager, AsyncIterator, Callable, TypeVar
+
+import _collections_abc
+
+__all__ = ["asynccontextmanager"]
+
+
+class AbstractAsyncContextManager(abc.ABC):
+
+    """An abstract base class for asynchronous context managers."""
+
+    async def __aenter__(self):
+        """Return `self` upon entering the runtime context."""
+        return self
+
+    @abc.abstractmethod
+    async def __aexit__(self, exc_type, exc_value, traceback):
+        """Raise any exception triggered within the runtime context."""
+        return None
+
+    @classmethod
+    def __subclasshook__(cls, C):
+        if cls is AbstractAsyncContextManager:
+            return _collections_abc._check_methods(C, "__aenter__", "__aexit__")  # type: ignore
+        return NotImplemented
+
+
+class _GeneratorContextManagerBase:
+    """Shared functionality for @contextmanager and @asynccontextmanager."""
+
+    def __init__(self, func, args, kwds):
+        self.gen = func(*args, **kwds)
+        self.func, self.args, self.kwds = func, args, kwds
+        # Issue 19330: ensure context manager instances have good docstrings
+        doc = getattr(func, "__doc__", None)
+        if doc is None:
+            doc = type(self).__doc__
+        self.__doc__ = doc
+        # Unfortunately, this still doesn't provide good help output when
+        # inspecting the created context manager instances, since pydoc
+        # currently bypasses the instance docstring and shows the docstring
+        # for the class instead.
+        # See http://bugs.python.org/issue19404 for more details.
+
+
+class _AsyncGeneratorContextManager(
+    _GeneratorContextManagerBase, AbstractAsyncContextManager
+):
+    """Helper for @asynccontextmanager."""
+
+    async def __aenter__(self):
+        try:
+            return await self.gen.__anext__()
+        except StopAsyncIteration:
+            raise RuntimeError("generator didn't yield") from None
+
+    async def __aexit__(self, typ, value, traceback):
+        if typ is None:
+            try:
+                await self.gen.__anext__()
+            except StopAsyncIteration:
+                return
+            else:
+                raise RuntimeError("generator didn't stop")
+        else:
+            if value is None:
+                value = typ()
+            # See _GeneratorContextManager.__exit__ for comments on subtleties
+            # in this implementation
+            try:
+                await self.gen.athrow(typ, value, traceback)
+                raise RuntimeError("generator didn't stop after athrow()")
+            except StopAsyncIteration as exc:
+                return exc is not value
+            except RuntimeError as exc:
+                if exc is value:
+                    return False
+                # Avoid suppressing if a StopIteration exception
+                # was passed to throw() and later wrapped into a RuntimeError
+                # (see PEP 479 for sync generators; async generators also
+                # have this behavior). But do this only if the exception wrapped
+                # by the RuntimeError is actully Stop(Async)Iteration (see
+                # issue29692).
+                if isinstance(value, (StopIteration, StopAsyncIteration)):
+                    if exc.__cause__ is value:
+                        return False
+                raise
+            except BaseException as exc:
+                if exc is not value:
+                    raise
+
+
+_T = TypeVar("_T")
+
+
+def asynccontextmanager(
+    func: Callable[..., AsyncIterator[_T]]
+) -> Callable[..., AsyncContextManager[_T]]:
+    """@asynccontextmanager decorator.
+    Typical usage:
+        @asynccontextmanager
+        async def some_async_generator(<arguments>):
+            <setup>
+            try:
+                yield <value>
+            finally:
+                <cleanup>
+    This makes this:
+        async with some_async_generator(<arguments>) as <variable>:
+            <body>
+    equivalent to this:
+        <setup>
+        try:
+            <variable> = <value>
+            <body>
+        finally:
+            <cleanup>
+    """
+
+    @wraps(func)
+    def helper(*args, **kwds):
+        return _AsyncGeneratorContextManager(func, args, kwds)  # type: ignore
+
+    return helper
diff --git a/src/prompt_toolkit/eventloop/async_generator.py b/src/prompt_toolkit/eventloop/async_generator.py
new file mode 100644
index 0000000..a4997b4
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/async_generator.py
@@ -0,0 +1,139 @@
+"""
+Implementation for async generators.
+"""
+from queue import Empty, Full, Queue
+from threading import Event
+from typing import (
+    TYPE_CHECKING,
+    AsyncGenerator,
+    Awaitable,
+    Callable,
+    Iterable,
+    TypeVar,
+    Union,
+)
+
+from .async_context_manager import asynccontextmanager
+from .utils import get_event_loop, run_in_executor_with_context
+
+__all__ = [
+    "aclosing",
+    "generator_to_async_generator",
+]
+
+
+if TYPE_CHECKING:
+    # Thanks: https://github.com/python/typeshed/blob/main/stdlib/contextlib.pyi
+    from typing_extensions import Protocol
+
+    class _SupportsAclose(Protocol):
+        def aclose(self) -> Awaitable[object]:
+            ...
+
+    _SupportsAcloseT = TypeVar("_SupportsAcloseT", bound=_SupportsAclose)
+
+
+@asynccontextmanager
+async def aclosing(
+    thing: "_SupportsAcloseT",
+) -> AsyncGenerator["_SupportsAcloseT", None]:
+    "Similar to `contextlib.aclosing`, in Python 3.10."
+    try:
+        yield thing
+    finally:
+        await thing.aclose()
+
+
+# By default, choose a buffer size that's a good balance between having enough
+# throughput, but not consuming too much memory. We use this to consume a sync
+# generator of completions as an async generator. If the queue size is very
+# small (like 1), consuming the completions goes really slow (when there are a
+# lot of items). If the queue size would be unlimited or too big, this can
+# cause overconsumption of memory, and cause CPU time spent producing items
+# that are no longer needed (if the consumption of the async generator stops at
+# some point). We need a fixed size in order to get some back pressure from the
+# async consumer to the sync producer. We choose 1000 by default here. If we
+# have around 50k completions, measurements show that 1000 is still
+# significantly faster than a buffer of 100.
+DEFAULT_BUFFER_SIZE: int = 1000
+
+_T = TypeVar("_T")
+
+
+class _Done:
+    pass
+
+
+async def generator_to_async_generator(
+    get_iterable: Callable[[], Iterable[_T]],
+    buffer_size: int = DEFAULT_BUFFER_SIZE,
+) -> AsyncGenerator[_T, None]:
+    """
+    Turn a generator or iterable into an async generator.
+
+    This works by running the generator in a background thread.
+
+    :param get_iterable: Function that returns a generator or iterable when
+        called.
+    :param buffer_size: Size of the queue between the async consumer and the
+        synchronous generator that produces items.
+    """
+    quitting = False
+    # NOTE: We are limiting the queue size in order to have back-pressure.
+    q: Queue[Union[_T, _Done]] = Queue(maxsize=buffer_size)
+    loop = get_event_loop()
+
+    def runner() -> None:
+        """
+        Consume the generator in background thread.
+        When items are received, they'll be pushed to the queue.
+        """
+        try:
+            for item in get_iterable():
+                # When this async generator was cancelled (closed), stop this
+                # thread.
+                if quitting:
+                    return
+
+                while True:
+                    try:
+                        q.put(item, timeout=1)
+                    except Full:
+                        if quitting:
+                            return
+                        continue
+                    else:
+                        break
+
+        finally:
+            while True:
+                try:
+                    q.put(_Done(), timeout=1)
+                except Full:
+                    if quitting:
+                        return
+                    continue
+                else:
+                    break
+
+    # Start background thread.
+    runner_f = run_in_executor_with_context(runner)
+
+    try:
+        while True:
+            try:
+                item = q.get_nowait()
+            except Empty:
+                item = await loop.run_in_executor(None, q.get)
+            if isinstance(item, _Done):
+                break
+            else:
+                yield item
+    finally:
+        # When this async generator is closed (GeneratorExit exception, stop
+        # the background thread as well. - we don't need that anymore.)
+        quitting = True
+
+        # Wait for the background thread to finish. (should happen right after
+        # the last item is yielded).
+        await runner_f
diff --git a/src/prompt_toolkit/eventloop/dummy_contextvars.py b/src/prompt_toolkit/eventloop/dummy_contextvars.py
new file mode 100644
index 0000000..3fcd260
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/dummy_contextvars.py
@@ -0,0 +1,56 @@
+"""
+Dummy contextvars implementation, to make prompt_toolkit work on Python 3.6.
+
+As long as there is only one application running at a time, we don't need the
+real contextvars. So, stuff like the telnet-server and so on requires 3.7.
+"""
+from typing import TYPE_CHECKING, Any, Callable, Generic, Optional, TypeVar
+
+if TYPE_CHECKING:
+    from typing_extensions import ParamSpec
+
+
+def copy_context() -> "Context":
+    return Context()
+
+
+if TYPE_CHECKING:
+    _P = ParamSpec("_P")
+_T = TypeVar("_T")
+
+
+class Context:
+    def run(
+        self, callable: "Callable[_P, _T]", *args: "_P.args", **kwargs: "_P.kwargs"
+    ) -> _T:
+        return callable(*args, **kwargs)
+
+    def copy(self) -> "Context":
+        return self
+
+
+class Token(Generic[_T]):
+    pass
+
+
+class ContextVar(Generic[_T]):
+    def __init__(self, name: str, *, default: Optional[_T] = None) -> None:
+        self._name = name
+        self._value = default
+
+    @property
+    def name(self) -> str:
+        return self._name
+
+    def get(self, default: Optional[_T] = None) -> _T:
+        result = self._value or default
+        if result is None:
+            raise LookupError
+        return result
+
+    def set(self, value: _T) -> Token[_T]:
+        self._value = value
+        return Token()
+
+    def reset(self, token: Token[_T]) -> None:
+        pass
diff --git a/src/prompt_toolkit/eventloop/inputhook.py b/src/prompt_toolkit/eventloop/inputhook.py
new file mode 100644
index 0000000..05d2981
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/inputhook.py
@@ -0,0 +1,183 @@
+"""
+Similar to `PyOS_InputHook` of the Python API, we can plug in an input hook in
+the asyncio event loop.
+
+The way this works is by using a custom 'selector' that runs the other event
+loop until the real selector is ready.
+
+It's the responsibility of this event hook to return when there is input ready.
+There are two ways to detect when input is ready:
+
+The inputhook itself is a callable that receives an `InputHookContext`. This
+callable should run the other event loop, and return when the main loop has
+stuff to do. There are two ways to detect when to return:
+
+- Call the `input_is_ready` method periodically. Quit when this returns `True`.
+
+- Add the `fileno` as a watch to the external eventloop. Quit when file descriptor
+  becomes readable. (But don't read from it.)
+
+  Note that this is not the same as checking for `sys.stdin.fileno()`. The
+  eventloop of prompt-toolkit allows thread-based executors, for example for
+  asynchronous autocompletion. When the completion for instance is ready, we
+  also want prompt-toolkit to gain control again in order to display that.
+"""
+import asyncio
+import os
+import select
+import selectors
+import sys
+import threading
+from asyncio import AbstractEventLoop
+from selectors import BaseSelector, SelectorKey
+from typing import TYPE_CHECKING, Any, Callable, List, Mapping, Optional, Tuple
+
+from .utils import get_event_loop
+
+__all__ = [
+    "new_eventloop_with_inputhook",
+    "set_eventloop_with_inputhook",
+    "InputHookSelector",
+    "InputHookContext",
+]
+
+if TYPE_CHECKING:
+    from _typeshed import FileDescriptorLike
+
+    _EventMask = int
+
+
+def new_eventloop_with_inputhook(
+    inputhook: Callable[["InputHookContext"], None]
+) -> AbstractEventLoop:
+    """
+    Create a new event loop with the given inputhook.
+    """
+    selector = InputHookSelector(selectors.DefaultSelector(), inputhook)
+    loop = asyncio.SelectorEventLoop(selector)
+    return loop
+
+
+def set_eventloop_with_inputhook(
+    inputhook: Callable[["InputHookContext"], None]
+) -> AbstractEventLoop:
+    """
+    Create a new event loop with the given inputhook, and activate it.
+    """
+    loop = new_eventloop_with_inputhook(inputhook)
+    asyncio.set_event_loop(loop)
+    return loop
+
+
+class InputHookSelector(BaseSelector):
+    """
+    Usage:
+
+        selector = selectors.SelectSelector()
+        loop = asyncio.SelectorEventLoop(InputHookSelector(selector, inputhook))
+        asyncio.set_event_loop(loop)
+    """
+
+    def __init__(
+        self, selector: BaseSelector, inputhook: Callable[["InputHookContext"], None]
+    ) -> None:
+        self.selector = selector
+        self.inputhook = inputhook
+        self._r, self._w = os.pipe()
+
+    def register(
+        self, fileobj: "FileDescriptorLike", events: "_EventMask", data: Any = None
+    ) -> "SelectorKey":
+        return self.selector.register(fileobj, events, data=data)
+
+    def unregister(self, fileobj: "FileDescriptorLike") -> "SelectorKey":
+        return self.selector.unregister(fileobj)
+
+    def modify(
+        self, fileobj: "FileDescriptorLike", events: "_EventMask", data: Any = None
+    ) -> "SelectorKey":
+        return self.selector.modify(fileobj, events, data=None)
+
+    def select(
+        self, timeout: Optional[float] = None
+    ) -> List[Tuple["SelectorKey", "_EventMask"]]:
+        # If there are tasks in the current event loop,
+        # don't run the input hook.
+        if len(getattr(get_event_loop(), "_ready", [])) > 0:
+            return self.selector.select(timeout=timeout)
+
+        ready = False
+        result = None
+
+        # Run selector in other thread.
+        def run_selector() -> None:
+            nonlocal ready, result
+            result = self.selector.select(timeout=timeout)
+            os.write(self._w, b"x")
+            ready = True
+
+        th = threading.Thread(target=run_selector)
+        th.start()
+
+        def input_is_ready() -> bool:
+            return ready
+
+        # Call inputhook.
+        # The inputhook function is supposed to return when our selector
+        # becomes ready. The inputhook can do that by registering the fd in its
+        # own loop, or by checking the `input_is_ready` function regularly.
+        self.inputhook(InputHookContext(self._r, input_is_ready))
+
+        # Flush the read end of the pipe.
+        try:
+            # Before calling 'os.read', call select.select. This is required
+            # when the gevent monkey patch has been applied. 'os.read' is never
+            # monkey patched and won't be cooperative, so that would block all
+            # other select() calls otherwise.
+            # See: http://www.gevent.org/gevent.os.html
+
+            # Note: On Windows, this is apparently not an issue.
+            #       However, if we would ever want to add a select call, it
+            #       should use `windll.kernel32.WaitForMultipleObjects`,
+            #       because `select.select` can't wait for a pipe on Windows.
+            if sys.platform != "win32":
+                select.select([self._r], [], [], None)
+
+            os.read(self._r, 1024)
+        except OSError:
+            # This happens when the window resizes and a SIGWINCH was received.
+            # We get 'Error: [Errno 4] Interrupted system call'
+            # Just ignore.
+            pass
+
+        # Wait for the real selector to be done.
+        th.join()
+        assert result is not None
+        return result
+
+    def close(self) -> None:
+        """
+        Clean up resources.
+        """
+        if self._r:
+            os.close(self._r)
+            os.close(self._w)
+
+        self._r = self._w = -1
+        self.selector.close()
+
+    def get_map(self) -> Mapping["FileDescriptorLike", "SelectorKey"]:
+        return self.selector.get_map()
+
+
+class InputHookContext:
+    """
+    Given as a parameter to the inputhook.
+    """
+
+    def __init__(self, fileno: int, input_is_ready: Callable[[], bool]) -> None:
+        self._fileno = fileno
+        self.input_is_ready = input_is_ready
+
+    def fileno(self) -> int:
+        return self._fileno
diff --git a/src/prompt_toolkit/eventloop/utils.py b/src/prompt_toolkit/eventloop/utils.py
new file mode 100644
index 0000000..2e5a05e
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/utils.py
@@ -0,0 +1,118 @@
+import asyncio
+import sys
+import time
+from types import TracebackType
+from typing import Any, Awaitable, Callable, Dict, Optional, TypeVar, cast
+
+try:
+    import contextvars
+except ImportError:
+    from . import dummy_contextvars as contextvars  # type: ignore
+
+__all__ = [
+    "run_in_executor_with_context",
+    "call_soon_threadsafe",
+    "get_traceback_from_context",
+    "get_event_loop",
+]
+
+_T = TypeVar("_T")
+
+
+def run_in_executor_with_context(
+    func: Callable[..., _T],
+    *args: Any,
+    loop: Optional[asyncio.AbstractEventLoop] = None,
+) -> Awaitable[_T]:
+    """
+    Run a function in an executor, but make sure it uses the same contextvars.
+    This is required so that the function will see the right application.
+
+    See also: https://bugs.python.org/issue34014
+    """
+    loop = loop or get_event_loop()
+    ctx: contextvars.Context = contextvars.copy_context()
+
+    return loop.run_in_executor(None, ctx.run, func, *args)
+
+
+def call_soon_threadsafe(
+    func: Callable[[], None],
+    max_postpone_time: Optional[float] = None,
+    loop: Optional[asyncio.AbstractEventLoop] = None,
+) -> None:
+    """
+    Wrapper around asyncio's `call_soon_threadsafe`.
+
+    This takes a `max_postpone_time` which can be used to tune the urgency of
+    the method.
+
+    Asyncio runs tasks in first-in-first-out. However, this is not what we
+    want for the render function of the prompt_toolkit UI. Rendering is
+    expensive, but since the UI is invalidated very often, in some situations
+    we render the UI too often, so much that the rendering CPU usage slows down
+    the rest of the processing of the application.  (Pymux is an example where
+    we have to balance the CPU time spend on rendering the UI, and parsing
+    process output.)
+    However, we want to set a deadline value, for when the rendering should
+    happen. (The UI should stay responsive).
+    """
+    loop2 = loop or get_event_loop()
+
+    # If no `max_postpone_time` has been given, schedule right now.
+    if max_postpone_time is None:
+        loop2.call_soon_threadsafe(func)
+        return
+
+    max_postpone_until = time.time() + max_postpone_time
+
+    def schedule() -> None:
+        # When there are no other tasks scheduled in the event loop. Run it
+        # now.
+        # Notice: uvloop doesn't have this _ready attribute. In that case,
+        #         always call immediately.
+        if not getattr(loop2, "_ready", []):
+            func()
+            return
+
+        # If the timeout expired, run this now.
+        if time.time() > max_postpone_until:
+            func()
+            return
+
+        # Schedule again for later.
+        loop2.call_soon_threadsafe(schedule)
+
+    loop2.call_soon_threadsafe(schedule)
+
+
+def get_traceback_from_context(context: Dict[str, Any]) -> Optional[TracebackType]:
+    """
+    Get the traceback object from the context.
+    """
+    exception = context.get("exception")
+    if exception:
+        if hasattr(exception, "__traceback__"):
+            return cast(TracebackType, exception.__traceback__)
+        else:
+            # call_exception_handler() is usually called indirectly
+            # from an except block. If it's not the case, the traceback
+            # is undefined...
+            return sys.exc_info()[2]
+
+    return None
+
+
+def get_event_loop() -> asyncio.AbstractEventLoop:
+    """Backward compatible way to get the event loop"""
+    # Python 3.6 doesn't have get_running_loop
+    # Python 3.10 deprecated get_event_loop
+    if sys.version_info >= (3, 7):
+        getloop = asyncio.get_running_loop
+    else:
+        getloop = asyncio.get_event_loop
+
+    try:
+        return getloop()
+    except RuntimeError:
+        return asyncio.get_event_loop_policy().get_event_loop()
diff --git a/src/prompt_toolkit/eventloop/win32.py b/src/prompt_toolkit/eventloop/win32.py
new file mode 100644
index 0000000..fbc02d4
--- /dev/null
+++ b/src/prompt_toolkit/eventloop/win32.py
@@ -0,0 +1,73 @@
+import sys
+
+assert sys.platform == "win32"
+
+from ctypes import pointer
+
+from ..utils import SPHINX_AUTODOC_RUNNING
+
+# Do not import win32-specific stuff when generating documentation.
+# Otherwise RTD would be unable to generate docs for this module.
+if not SPHINX_AUTODOC_RUNNING:
+    from ctypes import windll
+
+from ctypes.wintypes import BOOL, DWORD, HANDLE
+from typing import List, Optional
+
+from prompt_toolkit.win32_types import SECURITY_ATTRIBUTES
+
+__all__ = ["wait_for_handles", "create_win32_event"]
+
+
+WAIT_TIMEOUT = 0x00000102
+INFINITE = -1
+
+
+def wait_for_handles(
+    handles: List[HANDLE], timeout: int = INFINITE
+) -> Optional[HANDLE]:
+    """
+    Waits for multiple handles. (Similar to 'select') Returns the handle which is ready.
+    Returns `None` on timeout.
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms687025(v=vs.85).aspx
+
+    Note that handles should be a list of `HANDLE` objects, not integers. See
+    this comment in the patch by @quark-zju for the reason why:
+
+        ''' Make sure HANDLE on Windows has a correct size
+
+        Previously, the type of various HANDLEs are native Python integer
+        types. The ctypes library will treat them as 4-byte integer when used
+        in function arguments. On 64-bit Windows, HANDLE is 8-byte and usually
+        a small integer. Depending on whether the extra 4 bytes are zero-ed out
+        or not, things can happen to work, or break. '''
+
+    This function returns either `None` or one of the given `HANDLE` objects.
+    (The return value can be tested with the `is` operator.)
+    """
+    arrtype = HANDLE * len(handles)
+    handle_array = arrtype(*handles)
+
+    ret: int = windll.kernel32.WaitForMultipleObjects(
+        len(handle_array), handle_array, BOOL(False), DWORD(timeout)
+    )
+
+    if ret == WAIT_TIMEOUT:
+        return None
+    else:
+        return handles[ret]
+
+
+def create_win32_event() -> HANDLE:
+    """
+    Creates a Win32 unnamed Event .
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms682396(v=vs.85).aspx
+    """
+    return HANDLE(
+        windll.kernel32.CreateEventA(
+            pointer(SECURITY_ATTRIBUTES()),
+            BOOL(True),  # Manual reset event.
+            BOOL(False),  # Initial state.
+            None,  # Unnamed event object.
+        )
+    )
diff --git a/src/prompt_toolkit/filters/__init__.py b/src/prompt_toolkit/filters/__init__.py
new file mode 100644
index 0000000..d97195f
--- /dev/null
+++ b/src/prompt_toolkit/filters/__init__.py
@@ -0,0 +1,68 @@
+"""
+Filters decide whether something is active or not (they decide about a boolean
+state). This is used to enable/disable features, like key bindings, parts of
+the layout and other stuff. For instance, we could have a `HasSearch` filter
+attached to some part of the layout, in order to show that part of the user
+interface only while the user is searching.
+
+Filters are made to avoid having to attach callbacks to all event in order to
+propagate state. However, they are lazy, they don't automatically propagate the
+state of what they are observing. Only when a filter is called (it's actually a
+callable), it will calculate its value. So, its not really reactive
+programming, but it's made to fit for this framework.
+
+Filters can be chained using ``&`` and ``|`` operations, and inverted using the
+``~`` operator, for instance::
+
+    filter = has_focus('default') & ~ has_selection
+"""
+from .app import *
+from .base import Always, Condition, Filter, FilterOrBool, Never
+from .cli import *
+from .utils import is_true, to_filter
+
+__all__ = [
+    # app
+    "has_arg",
+    "has_completions",
+    "completion_is_selected",
+    "has_focus",
+    "buffer_has_focus",
+    "has_selection",
+    "has_validation_error",
+    "is_done",
+    "is_read_only",
+    "is_multiline",
+    "renderer_height_is_known",
+    "in_editing_mode",
+    "in_paste_mode",
+    "vi_mode",
+    "vi_navigation_mode",
+    "vi_insert_mode",
+    "vi_insert_multiple_mode",
+    "vi_replace_mode",
+    "vi_selection_mode",
+    "vi_waiting_for_text_object_mode",
+    "vi_digraph_mode",
+    "vi_recording_macro",
+    "emacs_mode",
+    "emacs_insert_mode",
+    "emacs_selection_mode",
+    "shift_selection_mode",
+    "is_searching",
+    "control_is_searchable",
+    "vi_search_direction_reversed",
+    # base.
+    "Filter",
+    "Never",
+    "Always",
+    "Condition",
+    "FilterOrBool",
+    # utils.
+    "is_true",
+    "to_filter",
+]
+
+from .cli import __all__ as cli_all
+
+__all__.extend(cli_all)
diff --git a/src/prompt_toolkit/filters/app.py b/src/prompt_toolkit/filters/app.py
new file mode 100644
index 0000000..dcc3fc0
--- /dev/null
+++ b/src/prompt_toolkit/filters/app.py
@@ -0,0 +1,412 @@
+"""
+Filters that accept a `Application` as argument.
+"""
+from typing import TYPE_CHECKING, cast
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.cache import memoized
+from prompt_toolkit.enums import EditingMode
+
+from .base import Condition
+
+if TYPE_CHECKING:
+    from prompt_toolkit.layout.layout import FocusableElement
+
+
+__all__ = [
+    "has_arg",
+    "has_completions",
+    "completion_is_selected",
+    "has_focus",
+    "buffer_has_focus",
+    "has_selection",
+    "has_suggestion",
+    "has_validation_error",
+    "is_done",
+    "is_read_only",
+    "is_multiline",
+    "renderer_height_is_known",
+    "in_editing_mode",
+    "in_paste_mode",
+    "vi_mode",
+    "vi_navigation_mode",
+    "vi_insert_mode",
+    "vi_insert_multiple_mode",
+    "vi_replace_mode",
+    "vi_selection_mode",
+    "vi_waiting_for_text_object_mode",
+    "vi_digraph_mode",
+    "vi_recording_macro",
+    "emacs_mode",
+    "emacs_insert_mode",
+    "emacs_selection_mode",
+    "shift_selection_mode",
+    "is_searching",
+    "control_is_searchable",
+    "vi_search_direction_reversed",
+]
+
+
+@memoized()
+def has_focus(value: "FocusableElement") -> Condition:
+    """
+    Enable when this buffer has the focus.
+    """
+    from prompt_toolkit.buffer import Buffer
+    from prompt_toolkit.layout import walk
+    from prompt_toolkit.layout.containers import Container, Window, to_container
+    from prompt_toolkit.layout.controls import UIControl
+
+    if isinstance(value, str):
+
+        def test() -> bool:
+            return get_app().current_buffer.name == value
+
+    elif isinstance(value, Buffer):
+
+        def test() -> bool:
+            return get_app().current_buffer == value
+
+    elif isinstance(value, UIControl):
+
+        def test() -> bool:
+            return get_app().layout.current_control == value
+
+    else:
+        value = to_container(value)
+
+        if isinstance(value, Window):
+
+            def test() -> bool:
+                return get_app().layout.current_window == value
+
+        else:
+
+            def test() -> bool:
+                # Consider focused when any window inside this container is
+                # focused.
+                current_window = get_app().layout.current_window
+
+                for c in walk(cast(Container, value)):
+                    if isinstance(c, Window) and c == current_window:
+                        return True
+                return False
+
+    @Condition
+    def has_focus_filter() -> bool:
+        return test()
+
+    return has_focus_filter
+
+
+@Condition
+def buffer_has_focus() -> bool:
+    """
+    Enabled when the currently focused control is a `BufferControl`.
+    """
+    return get_app().layout.buffer_has_focus
+
+
+@Condition
+def has_selection() -> bool:
+    """
+    Enable when the current buffer has a selection.
+    """
+    return bool(get_app().current_buffer.selection_state)
+
+
+@Condition
+def has_suggestion() -> bool:
+    """
+    Enable when the current buffer has a suggestion.
+    """
+    buffer = get_app().current_buffer
+    return buffer.suggestion is not None and buffer.suggestion.text != ""
+
+
+@Condition
+def has_completions() -> bool:
+    """
+    Enable when the current buffer has completions.
+    """
+    state = get_app().current_buffer.complete_state
+    return state is not None and len(state.completions) > 0
+
+
+@Condition
+def completion_is_selected() -> bool:
+    """
+    True when the user selected a completion.
+    """
+    complete_state = get_app().current_buffer.complete_state
+    return complete_state is not None and complete_state.current_completion is not None
+
+
+@Condition
+def is_read_only() -> bool:
+    """
+    True when the current buffer is read only.
+    """
+    return get_app().current_buffer.read_only()
+
+
+@Condition
+def is_multiline() -> bool:
+    """
+    True when the current buffer has been marked as multiline.
+    """
+    return get_app().current_buffer.multiline()
+
+
+@Condition
+def has_validation_error() -> bool:
+    "Current buffer has validation error."
+    return get_app().current_buffer.validation_error is not None
+
+
+@Condition
+def has_arg() -> bool:
+    "Enable when the input processor has an 'arg'."
+    return get_app().key_processor.arg is not None
+
+
+@Condition
+def is_done() -> bool:
+    """
+    True when the CLI is returning, aborting or exiting.
+    """
+    return get_app().is_done
+
+
+@Condition
+def renderer_height_is_known() -> bool:
+    """
+    Only True when the renderer knows it's real height.
+
+    (On VT100 terminals, we have to wait for a CPR response, before we can be
+    sure of the available height between the cursor position and the bottom of
+    the terminal. And usually it's nicer to wait with drawing bottom toolbars
+    until we receive the height, in order to avoid flickering -- first drawing
+    somewhere in the middle, and then again at the bottom.)
+    """
+    return get_app().renderer.height_is_known
+
+
+@memoized()
+def in_editing_mode(editing_mode: EditingMode) -> Condition:
+    """
+    Check whether a given editing mode is active. (Vi or Emacs.)
+    """
+
+    @Condition
+    def in_editing_mode_filter() -> bool:
+        return get_app().editing_mode == editing_mode
+
+    return in_editing_mode_filter
+
+
+@Condition
+def in_paste_mode() -> bool:
+    return get_app().paste_mode()
+
+
+@Condition
+def vi_mode() -> bool:
+    return get_app().editing_mode == EditingMode.VI
+
+
+@Condition
+def vi_navigation_mode() -> bool:
+    """
+    Active when the set for Vi navigation key bindings are active.
+    """
+    from prompt_toolkit.key_binding.vi_state import InputMode
+
+    app = get_app()
+
+    if (
+        app.editing_mode != EditingMode.VI
+        or app.vi_state.operator_func
+        or app.vi_state.waiting_for_digraph
+        or app.current_buffer.selection_state
+    ):
+        return False
+
+    return (
+        app.vi_state.input_mode == InputMode.NAVIGATION
+        or app.vi_state.temporary_navigation_mode
+        or app.current_buffer.read_only()
+    )
+
+
+@Condition
+def vi_insert_mode() -> bool:
+    from prompt_toolkit.key_binding.vi_state import InputMode
+
+    app = get_app()
+
+    if (
+        app.editing_mode != EditingMode.VI
+        or app.vi_state.operator_func
+        or app.vi_state.waiting_for_digraph
+        or app.current_buffer.selection_state
+        or app.vi_state.temporary_navigation_mode
+        or app.current_buffer.read_only()
+    ):
+        return False
+
+    return app.vi_state.input_mode == InputMode.INSERT
+
+
+@Condition
+def vi_insert_multiple_mode() -> bool:
+    from prompt_toolkit.key_binding.vi_state import InputMode
+
+    app = get_app()
+
+    if (
+        app.editing_mode != EditingMode.VI
+        or app.vi_state.operator_func
+        or app.vi_state.waiting_for_digraph
+        or app.current_buffer.selection_state
+        or app.vi_state.temporary_navigation_mode
+        or app.current_buffer.read_only()
+    ):
+        return False
+
+    return app.vi_state.input_mode == InputMode.INSERT_MULTIPLE
+
+
+@Condition
+def vi_replace_mode() -> bool:
+    from prompt_toolkit.key_binding.vi_state import InputMode
+
+    app = get_app()
+
+    if (
+        app.editing_mode != EditingMode.VI
+        or app.vi_state.operator_func
+        or app.vi_state.waiting_for_digraph
+        or app.current_buffer.selection_state
+        or app.vi_state.temporary_navigation_mode
+        or app.current_buffer.read_only()
+    ):
+        return False
+
+    return app.vi_state.input_mode == InputMode.REPLACE
+
+
+@Condition
+def vi_replace_single_mode() -> bool:
+    from prompt_toolkit.key_binding.vi_state import InputMode
+
+    app = get_app()
+
+    if (
+        app.editing_mode != EditingMode.VI
+        or app.vi_state.operator_func
+        or app.vi_state.waiting_for_digraph
+        or app.current_buffer.selection_state
+        or app.vi_state.temporary_navigation_mode
+        or app.current_buffer.read_only()
+    ):
+        return False
+
+    return app.vi_state.input_mode == InputMode.REPLACE_SINGLE
+
+
+@Condition
+def vi_selection_mode() -> bool:
+    app = get_app()
+    if app.editing_mode != EditingMode.VI:
+        return False
+
+    return bool(app.current_buffer.selection_state)
+
+
+@Condition
+def vi_waiting_for_text_object_mode() -> bool:
+    app = get_app()
+    if app.editing_mode != EditingMode.VI:
+        return False
+
+    return app.vi_state.operator_func is not None
+
+
+@Condition
+def vi_digraph_mode() -> bool:
+    app = get_app()
+    if app.editing_mode != EditingMode.VI:
+        return False
+
+    return app.vi_state.waiting_for_digraph
+
+
+@Condition
+def vi_recording_macro() -> bool:
+    "When recording a Vi macro."
+    app = get_app()
+    if app.editing_mode != EditingMode.VI:
+        return False
+
+    return app.vi_state.recording_register is not None
+
+
+@Condition
+def emacs_mode() -> bool:
+    "When the Emacs bindings are active."
+    return get_app().editing_mode == EditingMode.EMACS
+
+
+@Condition
+def emacs_insert_mode() -> bool:
+    app = get_app()
+    if (
+        app.editing_mode != EditingMode.EMACS
+        or app.current_buffer.selection_state
+        or app.current_buffer.read_only()
+    ):
+        return False
+    return True
+
+
+@Condition
+def emacs_selection_mode() -> bool:
+    app = get_app()
+    return bool(
+        app.editing_mode == EditingMode.EMACS and app.current_buffer.selection_state
+    )
+
+
+@Condition
+def shift_selection_mode() -> bool:
+    app = get_app()
+    return bool(
+        app.current_buffer.selection_state
+        and app.current_buffer.selection_state.shift_mode
+    )
+
+
+@Condition
+def is_searching() -> bool:
+    "When we are searching."
+    app = get_app()
+    return app.layout.is_searching
+
+
+@Condition
+def control_is_searchable() -> bool:
+    "When the current UIControl is searchable."
+    from prompt_toolkit.layout.controls import BufferControl
+
+    control = get_app().layout.current_control
+
+    return (
+        isinstance(control, BufferControl) and control.search_buffer_control is not None
+    )
+
+
+@Condition
+def vi_search_direction_reversed() -> bool:
+    "When the '/' and '?' key bindings for Vi-style searching have been reversed."
+    return get_app().reverse_vi_search_direction()
diff --git a/src/prompt_toolkit/filters/base.py b/src/prompt_toolkit/filters/base.py
new file mode 100644
index 0000000..fd57cca
--- /dev/null
+++ b/src/prompt_toolkit/filters/base.py
@@ -0,0 +1,217 @@
+from abc import ABCMeta, abstractmethod
+from typing import Callable, Dict, Iterable, List, Tuple, Union
+
+__all__ = ["Filter", "Never", "Always", "Condition", "FilterOrBool"]
+
+
+class Filter(metaclass=ABCMeta):
+    """
+    Base class for any filter to activate/deactivate a feature, depending on a
+    condition.
+
+    The return value of ``__call__`` will tell if the feature should be active.
+    """
+
+    @abstractmethod
+    def __call__(self) -> bool:
+        """
+        The actual call to evaluate the filter.
+        """
+        return True
+
+    def __and__(self, other: "Filter") -> "Filter":
+        """
+        Chaining of filters using the & operator.
+        """
+        return _and_cache[self, other]
+
+    def __or__(self, other: "Filter") -> "Filter":
+        """
+        Chaining of filters using the | operator.
+        """
+        return _or_cache[self, other]
+
+    def __invert__(self) -> "Filter":
+        """
+        Inverting of filters using the ~ operator.
+        """
+        return _invert_cache[self]
+
+    def __bool__(self) -> None:
+        """
+        By purpose, we don't allow bool(...) operations directly on a filter,
+        because the meaning is ambiguous.
+
+        Executing a filter has to be done always by calling it. Providing
+        defaults for `None` values should be done through an `is None` check
+        instead of for instance ``filter1 or Always()``.
+        """
+        raise ValueError(
+            "The truth value of a Filter is ambiguous. "
+            "Instead, call it as a function."
+        )
+
+
+class _AndCache(Dict[Tuple[Filter, Filter], "_AndList"]):
+    """
+    Cache for And operation between filters.
+    (Filter classes are stateless, so we can reuse them.)
+
+    Note: This could be a memory leak if we keep creating filters at runtime.
+          If that is True, the filters should be weakreffed (not the tuple of
+          filters), and tuples should be removed when one of these filters is
+          removed. In practise however, there is a finite amount of filters.
+    """
+
+    def __missing__(self, filters: Tuple[Filter, Filter]) -> Filter:
+        a, b = filters
+        assert isinstance(b, Filter), "Expecting filter, got %r" % b
+
+        if isinstance(b, Always) or isinstance(a, Never):
+            return a
+        elif isinstance(b, Never) or isinstance(a, Always):
+            return b
+
+        result = _AndList(filters)
+        self[filters] = result
+        return result
+
+
+class _OrCache(Dict[Tuple[Filter, Filter], "_OrList"]):
+    """Cache for Or operation between filters."""
+
+    def __missing__(self, filters: Tuple[Filter, Filter]) -> Filter:
+        a, b = filters
+        assert isinstance(b, Filter), "Expecting filter, got %r" % b
+
+        if isinstance(b, Always) or isinstance(a, Never):
+            return b
+        elif isinstance(b, Never) or isinstance(a, Always):
+            return a
+
+        result = _OrList(filters)
+        self[filters] = result
+        return result
+
+
+class _InvertCache(Dict[Filter, "_Invert"]):
+    """Cache for inversion operator."""
+
+    def __missing__(self, filter: Filter) -> Filter:
+        result = _Invert(filter)
+        self[filter] = result
+        return result
+
+
+_and_cache = _AndCache()
+_or_cache = _OrCache()
+_invert_cache = _InvertCache()
+
+
+class _AndList(Filter):
+    """
+    Result of &-operation between several filters.
+    """
+
+    def __init__(self, filters: Iterable[Filter]) -> None:
+        self.filters: List[Filter] = []
+
+        for f in filters:
+            if isinstance(f, _AndList):  # Turn nested _AndLists into one.
+                self.filters.extend(f.filters)
+            else:
+                self.filters.append(f)
+
+    def __call__(self) -> bool:
+        return all(f() for f in self.filters)
+
+    def __repr__(self) -> str:
+        return "&".join(repr(f) for f in self.filters)
+
+
+class _OrList(Filter):
+    """
+    Result of |-operation between several filters.
+    """
+
+    def __init__(self, filters: Iterable[Filter]) -> None:
+        self.filters: List[Filter] = []
+
+        for f in filters:
+            if isinstance(f, _OrList):  # Turn nested _OrLists into one.
+                self.filters.extend(f.filters)
+            else:
+                self.filters.append(f)
+
+    def __call__(self) -> bool:
+        return any(f() for f in self.filters)
+
+    def __repr__(self) -> str:
+        return "|".join(repr(f) for f in self.filters)
+
+
+class _Invert(Filter):
+    """
+    Negation of another filter.
+    """
+
+    def __init__(self, filter: Filter) -> None:
+        self.filter = filter
+
+    def __call__(self) -> bool:
+        return not self.filter()
+
+    def __repr__(self) -> str:
+        return "~%r" % self.filter
+
+
+class Always(Filter):
+    """
+    Always enable feature.
+    """
+
+    def __call__(self) -> bool:
+        return True
+
+    def __invert__(self) -> "Never":
+        return Never()
+
+
+class Never(Filter):
+    """
+    Never enable feature.
+    """
+
+    def __call__(self) -> bool:
+        return False
+
+    def __invert__(self) -> Always:
+        return Always()
+
+
+class Condition(Filter):
+    """
+    Turn any callable into a Filter. The callable is supposed to not take any
+    arguments.
+
+    This can be used as a decorator::
+
+        @Condition
+        def feature_is_active():  # `feature_is_active` becomes a Filter.
+            return True
+
+    :param func: Callable which takes no inputs and returns a boolean.
+    """
+
+    def __init__(self, func: Callable[[], bool]) -> None:
+        self.func = func
+
+    def __call__(self) -> bool:
+        return self.func()
+
+    def __repr__(self) -> str:
+        return "Condition(%r)" % self.func
+
+
+# Often used as type annotation.
+FilterOrBool = Union[Filter, bool]
diff --git a/src/prompt_toolkit/filters/cli.py b/src/prompt_toolkit/filters/cli.py
new file mode 100644
index 0000000..7135196
--- /dev/null
+++ b/src/prompt_toolkit/filters/cli.py
@@ -0,0 +1,62 @@
+"""
+For backwards-compatibility. keep this file.
+(Many people are going to have key bindings that rely on this file.)
+"""
+from .app import *
+
+__all__ = [
+    # Old names.
+    "HasArg",
+    "HasCompletions",
+    "HasFocus",
+    "HasSelection",
+    "HasValidationError",
+    "IsDone",
+    "IsReadOnly",
+    "IsMultiline",
+    "RendererHeightIsKnown",
+    "InEditingMode",
+    "InPasteMode",
+    "ViMode",
+    "ViNavigationMode",
+    "ViInsertMode",
+    "ViInsertMultipleMode",
+    "ViReplaceMode",
+    "ViSelectionMode",
+    "ViWaitingForTextObjectMode",
+    "ViDigraphMode",
+    "EmacsMode",
+    "EmacsInsertMode",
+    "EmacsSelectionMode",
+    "IsSearching",
+    "HasSearch",
+    "ControlIsSearchable",
+]
+
+# Keep the original classnames for backwards compatibility.
+HasValidationError = lambda: has_validation_error
+HasArg = lambda: has_arg
+IsDone = lambda: is_done
+RendererHeightIsKnown = lambda: renderer_height_is_known
+ViNavigationMode = lambda: vi_navigation_mode
+InPasteMode = lambda: in_paste_mode
+EmacsMode = lambda: emacs_mode
+EmacsInsertMode = lambda: emacs_insert_mode
+ViMode = lambda: vi_mode
+IsSearching = lambda: is_searching
+HasSearch = lambda: is_searching
+ControlIsSearchable = lambda: control_is_searchable
+EmacsSelectionMode = lambda: emacs_selection_mode
+ViDigraphMode = lambda: vi_digraph_mode
+ViWaitingForTextObjectMode = lambda: vi_waiting_for_text_object_mode
+ViSelectionMode = lambda: vi_selection_mode
+ViReplaceMode = lambda: vi_replace_mode
+ViInsertMultipleMode = lambda: vi_insert_multiple_mode
+ViInsertMode = lambda: vi_insert_mode
+HasSelection = lambda: has_selection
+HasCompletions = lambda: has_completions
+IsReadOnly = lambda: is_read_only
+IsMultiline = lambda: is_multiline
+
+HasFocus = has_focus  # No lambda here! (Has_focus is callable that returns a callable.)
+InEditingMode = in_editing_mode
diff --git a/src/prompt_toolkit/filters/utils.py b/src/prompt_toolkit/filters/utils.py
new file mode 100644
index 0000000..aaf44aa
--- /dev/null
+++ b/src/prompt_toolkit/filters/utils.py
@@ -0,0 +1,41 @@
+from typing import Dict
+
+from .base import Always, Filter, FilterOrBool, Never
+
+__all__ = [
+    "to_filter",
+    "is_true",
+]
+
+
+_always = Always()
+_never = Never()
+
+
+_bool_to_filter: Dict[bool, Filter] = {
+    True: _always,
+    False: _never,
+}
+
+
+def to_filter(bool_or_filter: FilterOrBool) -> Filter:
+    """
+    Accept both booleans and Filters as input and
+    turn it into a Filter.
+    """
+    if isinstance(bool_or_filter, bool):
+        return _bool_to_filter[bool_or_filter]
+
+    if isinstance(bool_or_filter, Filter):
+        return bool_or_filter
+
+    raise TypeError("Expecting a bool or a Filter instance. Got %r" % bool_or_filter)
+
+
+def is_true(value: FilterOrBool) -> bool:
+    """
+    Test whether `value` is True. In case of a Filter, call it.
+
+    :param value: Boolean or `Filter` instance.
+    """
+    return to_filter(value)()
diff --git a/src/prompt_toolkit/formatted_text/__init__.py b/src/prompt_toolkit/formatted_text/__init__.py
new file mode 100644
index 0000000..f0c92c9
--- /dev/null
+++ b/src/prompt_toolkit/formatted_text/__init__.py
@@ -0,0 +1,54 @@
+"""
+Many places in prompt_toolkit can take either plain text, or formatted text.
+For instance the :func:`~prompt_toolkit.shortcuts.prompt` function takes either
+plain text or formatted text for the prompt. The
+:class:`~prompt_toolkit.layout.FormattedTextControl` can also take either plain
+text or formatted text.
+
+In any case, there is an input that can either be just plain text (a string),
+an :class:`.HTML` object, an :class:`.ANSI` object or a sequence of
+`(style_string, text)` tuples. The :func:`.to_formatted_text` conversion
+function takes any of these and turns all of them into such a tuple sequence.
+"""
+from .ansi import ANSI
+from .base import (
+    AnyFormattedText,
+    FormattedText,
+    StyleAndTextTuples,
+    Template,
+    is_formatted_text,
+    merge_formatted_text,
+    to_formatted_text,
+)
+from .html import HTML
+from .pygments import PygmentsTokens
+from .utils import (
+    fragment_list_len,
+    fragment_list_to_text,
+    fragment_list_width,
+    split_lines,
+    to_plain_text,
+)
+
+__all__ = [
+    # Base.
+    "AnyFormattedText",
+    "to_formatted_text",
+    "is_formatted_text",
+    "Template",
+    "merge_formatted_text",
+    "FormattedText",
+    "StyleAndTextTuples",
+    # HTML.
+    "HTML",
+    # ANSI.
+    "ANSI",
+    # Pygments.
+    "PygmentsTokens",
+    # Utils.
+    "fragment_list_len",
+    "fragment_list_width",
+    "fragment_list_to_text",
+    "split_lines",
+    "to_plain_text",
+]
diff --git a/src/prompt_toolkit/formatted_text/ansi.py b/src/prompt_toolkit/formatted_text/ansi.py
new file mode 100644
index 0000000..2a30b09
--- /dev/null
+++ b/src/prompt_toolkit/formatted_text/ansi.py
@@ -0,0 +1,297 @@
+from string import Formatter
+from typing import Generator, List, Optional, Tuple, Union
+
+from prompt_toolkit.output.vt100 import BG_ANSI_COLORS, FG_ANSI_COLORS
+from prompt_toolkit.output.vt100 import _256_colors as _256_colors_table
+
+from .base import StyleAndTextTuples
+
+__all__ = [
+    "ANSI",
+    "ansi_escape",
+]
+
+
+class ANSI:
+    """
+    ANSI formatted text.
+    Take something ANSI escaped text, for use as a formatted string. E.g.
+
+    ::
+
+        ANSI('\\x1b[31mhello \\x1b[32mworld')
+
+    Characters between ``\\001`` and ``\\002`` are supposed to have a zero width
+    when printed, but these are literally sent to the terminal output. This can
+    be used for instance, for inserting Final Term prompt commands.  They will
+    be translated into a prompt_toolkit '[ZeroWidthEscape]' fragment.
+    """
+
+    def __init__(self, value: str) -> None:
+        self.value = value
+        self._formatted_text: StyleAndTextTuples = []
+
+        # Default style attributes.
+        self._color: Optional[str] = None
+        self._bgcolor: Optional[str] = None
+        self._bold = False
+        self._underline = False
+        self._strike = False
+        self._italic = False
+        self._blink = False
+        self._reverse = False
+        self._hidden = False
+
+        # Process received text.
+        parser = self._parse_corot()
+        parser.send(None)  # type: ignore
+        for c in value:
+            parser.send(c)
+
+    def _parse_corot(self) -> Generator[None, str, None]:
+        """
+        Coroutine that parses the ANSI escape sequences.
+        """
+        style = ""
+        formatted_text = self._formatted_text
+
+        while True:
+            # NOTE: CSI is a special token within a stream of characters that
+            #       introduces an ANSI control sequence used to set the
+            #       style attributes of the following characters.
+            csi = False
+
+            c = yield
+
+            # Everything between \001 and \002 should become a ZeroWidthEscape.
+            if c == "\001":
+                escaped_text = ""
+                while c != "\002":
+                    c = yield
+                    if c == "\002":
+                        formatted_text.append(("[ZeroWidthEscape]", escaped_text))
+                        c = yield
+                        break
+                    else:
+                        escaped_text += c
+
+            # Check for CSI
+            if c == "\x1b":
+                # Start of color escape sequence.
+                square_bracket = yield
+                if square_bracket == "[":
+                    csi = True
+                else:
+                    continue
+            elif c == "\x9b":
+                csi = True
+
+            if csi:
+                # Got a CSI sequence. Color codes are following.
+                current = ""
+                params = []
+
+                while True:
+                    char = yield
+
+                    # Construct number
+                    if char.isdigit():
+                        current += char
+
+                    # Eval number
+                    else:
+                        # Limit and save number value
+                        params.append(min(int(current or 0), 9999))
+
+                        # Get delimiter token if present
+                        if char == ";":
+                            current = ""
+
+                        # Check and evaluate color codes
+                        elif char == "m":
+                            # Set attributes and token.
+                            self._select_graphic_rendition(params)
+                            style = self._create_style_string()
+                            break
+
+                        # Check and evaluate cursor forward
+                        elif char == "C":
+                            for i in range(params[0]):
+                                # add <SPACE> using current style
+                                formatted_text.append((style, " "))
+                            break
+
+                        else:
+                            # Ignore unsupported sequence.
+                            break
+            else:
+                # Add current character.
+                # NOTE: At this point, we could merge the current character
+                #       into the previous tuple if the style did not change,
+                #       however, it's not worth the effort given that it will
+                #       be "Exploded" once again when it's rendered to the
+                #       output.
+                formatted_text.append((style, c))
+
+    def _select_graphic_rendition(self, attrs: List[int]) -> None:
+        """
+        Taken a list of graphics attributes and apply changes.
+        """
+        if not attrs:
+            attrs = [0]
+        else:
+            attrs = list(attrs[::-1])
+
+        while attrs:
+            attr = attrs.pop()
+
+            if attr in _fg_colors:
+                self._color = _fg_colors[attr]
+            elif attr in _bg_colors:
+                self._bgcolor = _bg_colors[attr]
+            elif attr == 1:
+                self._bold = True
+            # elif attr == 2:
+            #   self._faint = True
+            elif attr == 3:
+                self._italic = True
+            elif attr == 4:
+                self._underline = True
+            elif attr == 5:
+                self._blink = True  # Slow blink
+            elif attr == 6:
+                self._blink = True  # Fast blink
+            elif attr == 7:
+                self._reverse = True
+            elif attr == 8:
+                self._hidden = True
+            elif attr == 9:
+                self._strike = True
+            elif attr == 22:
+                self._bold = False  # Normal intensity
+            elif attr == 23:
+                self._italic = False
+            elif attr == 24:
+                self._underline = False
+            elif attr == 25:
+                self._blink = False
+            elif attr == 27:
+                self._reverse = False
+            elif attr == 28:
+                self._hidden = False
+            elif attr == 29:
+                self._strike = False
+            elif not attr:
+                # Reset all style attributes
+                self._color = None
+                self._bgcolor = None
+                self._bold = False
+                self._underline = False
+                self._strike = False
+                self._italic = False
+                self._blink = False
+                self._reverse = False
+                self._hidden = False
+
+            elif attr in (38, 48) and len(attrs) > 1:
+                n = attrs.pop()
+
+                # 256 colors.
+                if n == 5 and len(attrs) >= 1:
+                    if attr == 38:
+                        m = attrs.pop()
+                        self._color = _256_colors.get(m)
+                    elif attr == 48:
+                        m = attrs.pop()
+                        self._bgcolor = _256_colors.get(m)
+
+                # True colors.
+                if n == 2 and len(attrs) >= 3:
+                    try:
+                        color_str = "#{:02x}{:02x}{:02x}".format(
+                            attrs.pop(),
+                            attrs.pop(),
+                            attrs.pop(),
+                        )
+                    except IndexError:
+                        pass
+                    else:
+                        if attr == 38:
+                            self._color = color_str
+                        elif attr == 48:
+                            self._bgcolor = color_str
+
+    def _create_style_string(self) -> str:
+        """
+        Turn current style flags into a string for usage in a formatted text.
+        """
+        result = []
+        if self._color:
+            result.append(self._color)
+        if self._bgcolor:
+            result.append("bg:" + self._bgcolor)
+        if self._bold:
+            result.append("bold")
+        if self._underline:
+            result.append("underline")
+        if self._strike:
+            result.append("strike")
+        if self._italic:
+            result.append("italic")
+        if self._blink:
+            result.append("blink")
+        if self._reverse:
+            result.append("reverse")
+        if self._hidden:
+            result.append("hidden")
+
+        return " ".join(result)
+
+    def __repr__(self) -> str:
+        return f"ANSI({self.value!r})"
+
+    def __pt_formatted_text__(self) -> StyleAndTextTuples:
+        return self._formatted_text
+
+    def format(self, *args: str, **kwargs: str) -> "ANSI":
+        """
+        Like `str.format`, but make sure that the arguments are properly
+        escaped. (No ANSI escapes can be injected.)
+        """
+        return ANSI(FORMATTER.vformat(self.value, args, kwargs))
+
+    def __mod__(self, value: object) -> "ANSI":
+        """
+        ANSI('<b>%s</b>') % value
+        """
+        if not isinstance(value, tuple):
+            value = (value,)
+
+        value = tuple(ansi_escape(i) for i in value)
+        return ANSI(self.value % value)
+
+
+# Mapping of the ANSI color codes to their names.
+_fg_colors = {v: k for k, v in FG_ANSI_COLORS.items()}
+_bg_colors = {v: k for k, v in BG_ANSI_COLORS.items()}
+
+# Mapping of the escape codes for 256colors to their 'ffffff' value.
+_256_colors = {}
+
+for i, (r, g, b) in enumerate(_256_colors_table.colors):
+    _256_colors[i] = f"#{r:02x}{g:02x}{b:02x}"
+
+
+def ansi_escape(text: object) -> str:
+    """
+    Replace characters with a special meaning.
+    """
+    return str(text).replace("\x1b", "?").replace("\b", "?")
+
+
+class ANSIFormatter(Formatter):
+    def format_field(self, value: object, format_spec: str) -> str:
+        return ansi_escape(format(value, format_spec))
+
+
+FORMATTER = ANSIFormatter()
diff --git a/src/prompt_toolkit/formatted_text/base.py b/src/prompt_toolkit/formatted_text/base.py
new file mode 100644
index 0000000..9d991ce
--- /dev/null
+++ b/src/prompt_toolkit/formatted_text/base.py
@@ -0,0 +1,178 @@
+from typing import TYPE_CHECKING, Any, Callable, Iterable, List, Tuple, Union, cast
+
+from prompt_toolkit.mouse_events import MouseEvent
+
+if TYPE_CHECKING:
+    from typing_extensions import Protocol
+
+    from prompt_toolkit.key_binding.key_bindings import NotImplementedOrNone
+
+__all__ = [
+    "OneStyleAndTextTuple",
+    "StyleAndTextTuples",
+    "MagicFormattedText",
+    "AnyFormattedText",
+    "to_formatted_text",
+    "is_formatted_text",
+    "Template",
+    "merge_formatted_text",
+    "FormattedText",
+]
+
+OneStyleAndTextTuple = Union[
+    Tuple[str, str], Tuple[str, str, Callable[[MouseEvent], "NotImplementedOrNone"]]
+]
+
+# List of (style, text) tuples.
+StyleAndTextTuples = List[OneStyleAndTextTuple]
+
+
+if TYPE_CHECKING:
+    from typing_extensions import TypeGuard
+
+    class MagicFormattedText(Protocol):
+        """
+        Any object that implements ``__pt_formatted_text__`` represents formatted
+        text.
+        """
+
+        def __pt_formatted_text__(self) -> StyleAndTextTuples:
+            ...
+
+
+AnyFormattedText = Union[
+    str,
+    "MagicFormattedText",
+    StyleAndTextTuples,
+    # Callable[[], 'AnyFormattedText']  # Recursive definition not supported by mypy.
+    Callable[[], Any],
+    None,
+]
+
+
+def to_formatted_text(
+    value: AnyFormattedText, style: str = "", auto_convert: bool = False
+) -> "FormattedText":
+    """
+    Convert the given value (which can be formatted text) into a list of text
+    fragments. (Which is the canonical form of formatted text.) The outcome is
+    always a `FormattedText` instance, which is a list of (style, text) tuples.
+
+    It can take a plain text string, an `HTML` or `ANSI` object, anything that
+    implements `__pt_formatted_text__` or a callable that takes no arguments and
+    returns one of those.
+
+    :param style: An additional style string which is applied to all text
+        fragments.
+    :param auto_convert: If `True`, also accept other types, and convert them
+        to a string first.
+    """
+    result: Union[FormattedText, StyleAndTextTuples]
+
+    if value is None:
+        result = []
+    elif isinstance(value, str):
+        result = [("", value)]
+    elif isinstance(value, list):
+        result = value  # StyleAndTextTuples
+    elif hasattr(value, "__pt_formatted_text__"):
+        result = cast("MagicFormattedText", value).__pt_formatted_text__()
+    elif callable(value):
+        return to_formatted_text(value(), style=style)
+    elif auto_convert:
+        result = [("", f"{value}")]
+    else:
+        raise ValueError(
+            "No formatted text. Expecting a unicode object, "
+            "HTML, ANSI or a FormattedText instance. Got %r" % (value,)
+        )
+
+    # Apply extra style.
+    if style:
+        result = cast(
+            StyleAndTextTuples,
+            [(style + " " + item_style, *rest) for item_style, *rest in result],
+        )
+
+    # Make sure the result is wrapped in a `FormattedText`. Among other
+    # reasons, this is important for `print_formatted_text` to work correctly
+    # and distinguish between lists and formatted text.
+    if isinstance(result, FormattedText):
+        return result
+    else:
+        return FormattedText(result)
+
+
+def is_formatted_text(value: object) -> "TypeGuard[AnyFormattedText]":
+    """
+    Check whether the input is valid formatted text (for use in assert
+    statements).
+    In case of a callable, it doesn't check the return type.
+    """
+    if callable(value):
+        return True
+    if isinstance(value, (str, list)):
+        return True
+    if hasattr(value, "__pt_formatted_text__"):
+        return True
+    return False
+
+
+class FormattedText(StyleAndTextTuples):
+    """
+    A list of ``(style, text)`` tuples.
+
+    (In some situations, this can also be ``(style, text, mouse_handler)``
+    tuples.)
+    """
+
+    def __pt_formatted_text__(self) -> StyleAndTextTuples:
+        return self
+
+    def __repr__(self) -> str:
+        return "FormattedText(%s)" % super().__repr__()
+
+
+class Template:
+    """
+    Template for string interpolation with formatted text.
+
+    Example::
+
+        Template(' ... {} ... ').format(HTML(...))
+
+    :param text: Plain text.
+    """
+
+    def __init__(self, text: str) -> None:
+        assert "{0}" not in text
+        self.text = text
+
+    def format(self, *values: AnyFormattedText) -> AnyFormattedText:
+        def get_result() -> AnyFormattedText:
+            # Split the template in parts.
+            parts = self.text.split("{}")
+            assert len(parts) - 1 == len(values)
+
+            result = FormattedText()
+            for part, val in zip(parts, values):
+                result.append(("", part))
+                result.extend(to_formatted_text(val))
+            result.append(("", parts[-1]))
+            return result
+
+        return get_result
+
+
+def merge_formatted_text(items: Iterable[AnyFormattedText]) -> AnyFormattedText:
+    """
+    Merge (Concatenate) several pieces of formatted text together.
+    """
+
+    def _merge_formatted_text() -> AnyFormattedText:
+        result = FormattedText()
+        for i in items:
+            result.extend(to_formatted_text(i))
+        return result
+
+    return _merge_formatted_text
diff --git a/src/prompt_toolkit/formatted_text/html.py b/src/prompt_toolkit/formatted_text/html.py
new file mode 100644
index 0000000..0af2b18
--- /dev/null
+++ b/src/prompt_toolkit/formatted_text/html.py
@@ -0,0 +1,143 @@
+import xml.dom.minidom as minidom
+from string import Formatter
+from typing import Any, List, Tuple, Union
+
+from .base import FormattedText, StyleAndTextTuples
+
+__all__ = ["HTML"]
+
+
+class HTML:
+    """
+    HTML formatted text.
+    Take something HTML-like, for use as a formatted string.
+
+    ::
+
+        # Turn something into red.
+        HTML('<style fg="ansired" bg="#00ff44">...</style>')
+
+        # Italic, bold, underline and strike.
+        HTML('<i>...</i>')
+        HTML('<b>...</b>')
+        HTML('<u>...</u>')
+        HTML('<s>...</s>')
+
+    All HTML elements become available as a "class" in the style sheet.
+    E.g. ``<username>...</username>`` can be styled, by setting a style for
+    ``username``.
+    """
+
+    def __init__(self, value: str) -> None:
+        self.value = value
+        document = minidom.parseString(f"<html-root>{value}</html-root>")
+
+        result: StyleAndTextTuples = []
+        name_stack: List[str] = []
+        fg_stack: List[str] = []
+        bg_stack: List[str] = []
+
+        def get_current_style() -> str:
+            "Build style string for current node."
+            parts = []
+            if name_stack:
+                parts.append("class:" + ",".join(name_stack))
+
+            if fg_stack:
+                parts.append("fg:" + fg_stack[-1])
+            if bg_stack:
+                parts.append("bg:" + bg_stack[-1])
+            return " ".join(parts)
+
+        def process_node(node: Any) -> None:
+            "Process node recursively."
+            for child in node.childNodes:
+                if child.nodeType == child.TEXT_NODE:
+                    result.append((get_current_style(), child.data))
+                else:
+                    add_to_name_stack = child.nodeName not in (
+                        "#document",
+                        "html-root",
+                        "style",
+                    )
+                    fg = bg = ""
+
+                    for k, v in child.attributes.items():
+                        if k == "fg":
+                            fg = v
+                        if k == "bg":
+                            bg = v
+                        if k == "color":
+                            fg = v  # Alias for 'fg'.
+
+                    # Check for spaces in attributes. This would result in
+                    # invalid style strings otherwise.
+                    if " " in fg:
+                        raise ValueError('"fg" attribute contains a space.')
+                    if " " in bg:
+                        raise ValueError('"bg" attribute contains a space.')
+
+                    if add_to_name_stack:
+                        name_stack.append(child.nodeName)
+                    if fg:
+                        fg_stack.append(fg)
+                    if bg:
+                        bg_stack.append(bg)
+
+                    process_node(child)
+
+                    if add_to_name_stack:
+                        name_stack.pop()
+                    if fg:
+                        fg_stack.pop()
+                    if bg:
+                        bg_stack.pop()
+
+        process_node(document)
+
+        self.formatted_text = FormattedText(result)
+
+    def __repr__(self) -> str:
+        return f"HTML({self.value!r})"
+
+    def __pt_formatted_text__(self) -> StyleAndTextTuples:
+        return self.formatted_text
+
+    def format(self, *args: object, **kwargs: object) -> "HTML":
+        """
+        Like `str.format`, but make sure that the arguments are properly
+        escaped.
+        """
+        return HTML(FORMATTER.vformat(self.value, args, kwargs))
+
+    def __mod__(self, value: object) -> "HTML":
+        """
+        HTML('<b>%s</b>') % value
+        """
+        if not isinstance(value, tuple):
+            value = (value,)
+
+        value = tuple(html_escape(i) for i in value)
+        return HTML(self.value % value)
+
+
+class HTMLFormatter(Formatter):
+    def format_field(self, value: object, format_spec: str) -> str:
+        return html_escape(format(value, format_spec))
+
+
+def html_escape(text: object) -> str:
+    # The string interpolation functions also take integers and other types.
+    # Convert to string first.
+    if not isinstance(text, str):
+        text = f"{text}"
+
+    return (
+        text.replace("&", "&amp;")
+        .replace("<", "&lt;")
+        .replace(">", "&gt;")
+        .replace('"', "&quot;")
+    )
+
+
+FORMATTER = HTMLFormatter()
diff --git a/src/prompt_toolkit/formatted_text/pygments.py b/src/prompt_toolkit/formatted_text/pygments.py
new file mode 100644
index 0000000..dd16f0e
--- /dev/null
+++ b/src/prompt_toolkit/formatted_text/pygments.py
@@ -0,0 +1,30 @@
+from typing import TYPE_CHECKING, List, Tuple
+
+from prompt_toolkit.styles.pygments import pygments_token_to_classname
+
+from .base import StyleAndTextTuples
+
+if TYPE_CHECKING:
+    from pygments.token import Token
+
+__all__ = [
+    "PygmentsTokens",
+]
+
+
+class PygmentsTokens:
+    """
+    Turn a pygments token list into a list of prompt_toolkit text fragments
+    (``(style_str, text)`` tuples).
+    """
+
+    def __init__(self, token_list: List[Tuple["Token", str]]) -> None:
+        self.token_list = token_list
+
+    def __pt_formatted_text__(self) -> StyleAndTextTuples:
+        result: StyleAndTextTuples = []
+
+        for token, text in self.token_list:
+            result.append(("class:" + pygments_token_to_classname(token), text))
+
+        return result
diff --git a/src/prompt_toolkit/formatted_text/utils.py b/src/prompt_toolkit/formatted_text/utils.py
new file mode 100644
index 0000000..cda4233
--- /dev/null
+++ b/src/prompt_toolkit/formatted_text/utils.py
@@ -0,0 +1,98 @@
+"""
+Utilities for manipulating formatted text.
+
+When ``to_formatted_text`` has been called, we get a list of ``(style, text)``
+tuples. This file contains functions for manipulating such a list.
+"""
+from typing import Iterable, cast
+
+from prompt_toolkit.utils import get_cwidth
+
+from .base import (
+    AnyFormattedText,
+    OneStyleAndTextTuple,
+    StyleAndTextTuples,
+    to_formatted_text,
+)
+
+__all__ = [
+    "to_plain_text",
+    "fragment_list_len",
+    "fragment_list_width",
+    "fragment_list_to_text",
+    "split_lines",
+]
+
+
+def to_plain_text(value: AnyFormattedText) -> str:
+    """
+    Turn any kind of formatted text back into plain text.
+    """
+    return fragment_list_to_text(to_formatted_text(value))
+
+
+def fragment_list_len(fragments: StyleAndTextTuples) -> int:
+    """
+    Return the amount of characters in this text fragment list.
+
+    :param fragments: List of ``(style_str, text)`` or
+        ``(style_str, text, mouse_handler)`` tuples.
+    """
+    ZeroWidthEscape = "[ZeroWidthEscape]"
+    return sum(len(item[1]) for item in fragments if ZeroWidthEscape not in item[0])
+
+
+def fragment_list_width(fragments: StyleAndTextTuples) -> int:
+    """
+    Return the character width of this text fragment list.
+    (Take double width characters into account.)
+
+    :param fragments: List of ``(style_str, text)`` or
+        ``(style_str, text, mouse_handler)`` tuples.
+    """
+    ZeroWidthEscape = "[ZeroWidthEscape]"
+    return sum(
+        get_cwidth(c)
+        for item in fragments
+        for c in item[1]
+        if ZeroWidthEscape not in item[0]
+    )
+
+
+def fragment_list_to_text(fragments: StyleAndTextTuples) -> str:
+    """
+    Concatenate all the text parts again.
+
+    :param fragments: List of ``(style_str, text)`` or
+        ``(style_str, text, mouse_handler)`` tuples.
+    """
+    ZeroWidthEscape = "[ZeroWidthEscape]"
+    return "".join(item[1] for item in fragments if ZeroWidthEscape not in item[0])
+
+
+def split_lines(fragments: StyleAndTextTuples) -> Iterable[StyleAndTextTuples]:
+    """
+    Take a single list of (style_str, text) tuples and yield one such list for each
+    line. Just like str.split, this will yield at least one item.
+
+    :param fragments: List of (style_str, text) or (style_str, text, mouse_handler)
+                      tuples.
+    """
+    line: StyleAndTextTuples = []
+
+    for style, string, *mouse_handler in fragments:
+        parts = string.split("\n")
+
+        for part in parts[:-1]:
+            if part:
+                line.append(cast(OneStyleAndTextTuple, (style, part, *mouse_handler)))
+            yield line
+            line = []
+
+        line.append(cast(OneStyleAndTextTuple, (style, parts[-1], *mouse_handler)))
+
+    # Always yield the last line, even when this is an empty line. This ensures
+    # that when `fragments` ends with a newline character, an additional empty
+    # line is yielded. (Otherwise, there's no way to differentiate between the
+    # cases where `fragments` does and doesn't end with a newline.)
+    yield line
diff --git a/src/prompt_toolkit/history.py b/src/prompt_toolkit/history.py
new file mode 100644
index 0000000..987d717
--- /dev/null
+++ b/src/prompt_toolkit/history.py
@@ -0,0 +1,301 @@
+"""
+Implementations for the history of a `Buffer`.
+
+NOTE: There is no `DynamicHistory`:
+      This doesn't work well, because the `Buffer` needs to be able to attach
+      an event handler to the event when a history entry is loaded. This
+      loading can be done asynchronously and making the history swappable would
+      probably break this.
+"""
+import datetime
+import os
+import threading
+from abc import ABCMeta, abstractmethod
+from typing import AsyncGenerator, Iterable, List, Optional, Sequence, Tuple
+
+from prompt_toolkit.eventloop import get_event_loop
+
+__all__ = [
+    "History",
+    "ThreadedHistory",
+    "DummyHistory",
+    "FileHistory",
+    "InMemoryHistory",
+]
+
+
+class History(metaclass=ABCMeta):
+    """
+    Base ``History`` class.
+
+    This also includes abstract methods for loading/storing history.
+    """
+
+    def __init__(self) -> None:
+        # In memory storage for strings.
+        self._loaded = False
+
+        # History that's loaded already, in reverse order. Latest, most recent
+        # item first.
+        self._loaded_strings: List[str] = []
+
+    #
+    # Methods expected by `Buffer`.
+    #
+
+    async def load(self) -> AsyncGenerator[str, None]:
+        """
+        Load the history and yield all the entries in reverse order (latest,
+        most recent history entry first).
+
+        This method can be called multiple times from the `Buffer` to
+        repopulate the history when prompting for a new input. So we are
+        responsible here for both caching, and making sure that strings that
+        were were appended to the history will be incorporated next time this
+        method is called.
+        """
+        if not self._loaded:
+            self._loaded_strings = list(self.load_history_strings())
+            self._loaded = True
+
+        for item in self._loaded_strings:
+            yield item
+
+    def get_strings(self) -> List[str]:
+        """
+        Get the strings from the history that are loaded so far.
+        (In order. Oldest item first.)
+        """
+        return self._loaded_strings[::-1]
+
+    def append_string(self, string: str) -> None:
+        "Add string to the history."
+        self._loaded_strings.insert(0, string)
+        self.store_string(string)
+
+    #
+    # Implementation for specific backends.
+    #
+
+    @abstractmethod
+    def load_history_strings(self) -> Iterable[str]:
+        """
+        This should be a generator that yields `str` instances.
+
+        It should yield the most recent items first, because they are the most
+        important. (The history can already be used, even when it's only
+        partially loaded.)
+        """
+        while False:
+            yield
+
+    @abstractmethod
+    def store_string(self, string: str) -> None:
+        """
+        Store the string in persistent storage.
+        """
+
+
+class ThreadedHistory(History):
+    """
+    Wrapper around `History` implementations that run the `load()` generator in
+    a thread.
+
+    Use this to increase the start-up time of prompt_toolkit applications.
+    History entries are available as soon as they are loaded. We don't have to
+    wait for everything to be loaded.
+    """
+
+    def __init__(self, history: History) -> None:
+        super().__init__()
+
+        self.history = history
+
+        self._load_thread: Optional[threading.Thread] = None
+
+        # Lock for accessing/manipulating `_loaded_strings` and `_loaded`
+        # together in a consistent state.
+        self._lock = threading.Lock()
+
+        # Events created by each `load()` call. Used to wait for new history
+        # entries from the loader thread.
+        self._string_load_events: List[threading.Event] = []
+
+    async def load(self) -> AsyncGenerator[str, None]:
+        """
+        Like `History.load(), but call `self.load_history_strings()` in a
+        background thread.
+        """
+        # Start the load thread, if this is called for the first time.
+        if not self._load_thread:
+            self._load_thread = threading.Thread(
+                target=self._in_load_thread,
+                daemon=True,
+            )
+            self._load_thread.start()
+
+        # Consume the `_loaded_strings` list, using asyncio.
+        loop = get_event_loop()
+
+        # Create threading Event so that we can wait for new items.
+        event = threading.Event()
+        event.set()
+        self._string_load_events.append(event)
+
+        items_yielded = 0
+
+        try:
+            while True:
+                # Wait for new items to be available.
+                # (Use a timeout, because the executor thread is not a daemon
+                # thread. The "slow-history.py" example would otherwise hang if
+                # Control-C is pressed before the history is fully loaded,
+                # because there's still this non-daemon executor thread waiting
+                # for this event.)
+                got_timeout = await loop.run_in_executor(
+                    None, lambda: event.wait(timeout=0.5)
+                )
+                if not got_timeout:
+                    continue
+
+                # Read new items (in lock).
+                def in_executor() -> Tuple[List[str], bool]:
+                    with self._lock:
+                        new_items = self._loaded_strings[items_yielded:]
+                        done = self._loaded
+                        event.clear()
+                    return new_items, done
+
+                new_items, done = await loop.run_in_executor(None, in_executor)
+
+                items_yielded += len(new_items)
+
+                for item in new_items:
+                    yield item
+
+                if done:
+                    break
+        finally:
+            self._string_load_events.remove(event)
+
+    def _in_load_thread(self) -> None:
+        try:
+            # Start with an empty list. In case `append_string()` was called
+            # before `load()` happened. Then `.store_string()` will have
+            # written these entries back to disk and we will reload it.
+            self._loaded_strings = []
+
+            for item in self.history.load_history_strings():
+                with self._lock:
+                    self._loaded_strings.append(item)
+
+                for event in self._string_load_events:
+                    event.set()
+        finally:
+            with self._lock:
+                self._loaded = True
+            for event in self._string_load_events:
+                event.set()
+
+    def append_string(self, string: str) -> None:
+        with self._lock:
+            self._loaded_strings.insert(0, string)
+        self.store_string(string)
+
+    # All of the following are proxied to `self.history`.
+
+    def load_history_strings(self) -> Iterable[str]:
+        return self.history.load_history_strings()
+
+    def store_string(self, string: str) -> None:
+        self.history.store_string(string)
+
+    def __repr__(self) -> str:
+        return f"ThreadedHistory({self.history!r})"
+
+
+class InMemoryHistory(History):
+    """
+    :class:`.History` class that keeps a list of all strings in memory.
+
+    In order to prepopulate the history, it's possible to call either
+    `append_string` for all items or pass a list of strings to `__init__` here.
+    """
+
+    def __init__(self, history_strings: Optional[Sequence[str]] = None) -> None:
+        super().__init__()
+        # Emulating disk storage.
+        if history_strings is None:
+            self._storage = []
+        else:
+            self._storage = list(history_strings)
+
+    def load_history_strings(self) -> Iterable[str]:
+        yield from self._storage[::-1]
+
+    def store_string(self, string: str) -> None:
+        self._storage.append(string)
+
+
+class DummyHistory(History):
+    """
+    :class:`.History` object that doesn't remember anything.
+    """
+
+    def load_history_strings(self) -> Iterable[str]:
+        return []
+
+    def store_string(self, string: str) -> None:
+        pass
+
+    def append_string(self, string: str) -> None:
+        # Don't remember this.
+        pass
+
+
+class FileHistory(History):
+    """
+    :class:`.History` class that stores all strings in a file.
+    """
+
+    def __init__(self, filename: str) -> None:
+        self.filename = filename
+        super().__init__()
+
+    def load_history_strings(self) -> Iterable[str]:
+        strings: List[str] = []
+        lines: List[str] = []
+
+        def add() -> None:
+            if lines:
+                # Join and drop trailing newline.
+                string = "".join(lines)[:-1]
+
+                strings.append(string)
+
+        if os.path.exists(self.filename):
+            with open(self.filename, "rb") as f:
+                for line_bytes in f:
+                    line = line_bytes.decode("utf-8", errors="replace")
+
+                    if line.startswith("+"):
+                        lines.append(line[1:])
+                    else:
+                        add()
+                        lines = []
+
+                add()
+
+        # Reverse the order, because newest items have to go first.
+        return reversed(strings)
+
+    def store_string(self, string: str) -> None:
+        # Save to file.
+        with open(self.filename, "ab") as f:
+
+            def write(t: str) -> None:
+                f.write(t.encode("utf-8"))
+
+            write("\n# %s\n" % datetime.datetime.now())
+            for line in string.split("\n"):
+                write("+%s\n" % line)
diff --git a/src/prompt_toolkit/input/__init__.py b/src/prompt_toolkit/input/__init__.py
new file mode 100644
index 0000000..dc31976
--- /dev/null
+++ b/src/prompt_toolkit/input/__init__.py
@@ -0,0 +1,12 @@
+from .base import DummyInput, Input, PipeInput
+from .defaults import create_input, create_pipe_input
+
+__all__ = [
+    # Base.
+    "Input",
+    "PipeInput",
+    "DummyInput",
+    # Defaults.
+    "create_input",
+    "create_pipe_input",
+]
diff --git a/src/prompt_toolkit/input/ansi_escape_sequences.py b/src/prompt_toolkit/input/ansi_escape_sequences.py
new file mode 100644
index 0000000..2e6c5b9
--- /dev/null
+++ b/src/prompt_toolkit/input/ansi_escape_sequences.py
@@ -0,0 +1,343 @@
+"""
+Mappings from VT100 (ANSI) escape sequences to the corresponding prompt_toolkit
+keys.
+
+We are not using the terminfo/termcap databases to detect the ANSI escape
+sequences for the input. Instead, we recognize 99% of the most common
+sequences. This works well, because in practice, every modern terminal is
+mostly Xterm compatible.
+
+Some useful docs:
+- Mintty: https://github.com/mintty/mintty/blob/master/wiki/Keycodes.md
+"""
+from typing import Dict, Tuple, Union
+
+from ..keys import Keys
+
+__all__ = [
+    "ANSI_SEQUENCES",
+    "REVERSE_ANSI_SEQUENCES",
+]
+
+# Mapping of vt100 escape codes to Keys.
+ANSI_SEQUENCES: Dict[str, Union[Keys, Tuple[Keys, ...]]] = {
+    # Control keys.
+    "\x00": Keys.ControlAt,  # Control-At (Also for Ctrl-Space)
+    "\x01": Keys.ControlA,  # Control-A (home)
+    "\x02": Keys.ControlB,  # Control-B (emacs cursor left)
+    "\x03": Keys.ControlC,  # Control-C (interrupt)
+    "\x04": Keys.ControlD,  # Control-D (exit)
+    "\x05": Keys.ControlE,  # Control-E (end)
+    "\x06": Keys.ControlF,  # Control-F (cursor forward)
+    "\x07": Keys.ControlG,  # Control-G
+    "\x08": Keys.ControlH,  # Control-H (8) (Identical to '\b')
+    "\x09": Keys.ControlI,  # Control-I (9) (Identical to '\t')
+    "\x0a": Keys.ControlJ,  # Control-J (10) (Identical to '\n')
+    "\x0b": Keys.ControlK,  # Control-K (delete until end of line; vertical tab)
+    "\x0c": Keys.ControlL,  # Control-L (clear; form feed)
+    "\x0d": Keys.ControlM,  # Control-M (13) (Identical to '\r')
+    "\x0e": Keys.ControlN,  # Control-N (14) (history forward)
+    "\x0f": Keys.ControlO,  # Control-O (15)
+    "\x10": Keys.ControlP,  # Control-P (16) (history back)
+    "\x11": Keys.ControlQ,  # Control-Q
+    "\x12": Keys.ControlR,  # Control-R (18) (reverse search)
+    "\x13": Keys.ControlS,  # Control-S (19) (forward search)
+    "\x14": Keys.ControlT,  # Control-T
+    "\x15": Keys.ControlU,  # Control-U
+    "\x16": Keys.ControlV,  # Control-V
+    "\x17": Keys.ControlW,  # Control-W
+    "\x18": Keys.ControlX,  # Control-X
+    "\x19": Keys.ControlY,  # Control-Y (25)
+    "\x1a": Keys.ControlZ,  # Control-Z
+    "\x1b": Keys.Escape,  # Also Control-[
+    "\x9b": Keys.ShiftEscape,
+    "\x1c": Keys.ControlBackslash,  # Both Control-\ (also Ctrl-| )
+    "\x1d": Keys.ControlSquareClose,  # Control-]
+    "\x1e": Keys.ControlCircumflex,  # Control-^
+    "\x1f": Keys.ControlUnderscore,  # Control-underscore (Also for Ctrl-hyphen.)
+    # ASCII Delete (0x7f)
+    # Vt220 (and Linux terminal) send this when pressing backspace. We map this
+    # to ControlH, because that will make it easier to create key bindings that
+    # work everywhere, with the trade-off that it's no longer possible to
+    # handle backspace and control-h individually for the few terminals that
+    # support it. (Most terminals send ControlH when backspace is pressed.)
+    # See: http://www.ibb.net/~anne/keyboard.html
+    "\x7f": Keys.ControlH,
+    # --
+    # Various
+    "\x1b[1~": Keys.Home,  # tmux
+    "\x1b[2~": Keys.Insert,
+    "\x1b[3~": Keys.Delete,
+    "\x1b[4~": Keys.End,  # tmux
+    "\x1b[5~": Keys.PageUp,
+    "\x1b[6~": Keys.PageDown,
+    "\x1b[7~": Keys.Home,  # xrvt
+    "\x1b[8~": Keys.End,  # xrvt
+    "\x1b[Z": Keys.BackTab,  # shift + tab
+    "\x1b\x09": Keys.BackTab,  # Linux console
+    "\x1b[~": Keys.BackTab,  # Windows console
+    # --
+    # Function keys.
+    "\x1bOP": Keys.F1,
+    "\x1bOQ": Keys.F2,
+    "\x1bOR": Keys.F3,
+    "\x1bOS": Keys.F4,
+    "\x1b[[A": Keys.F1,  # Linux console.
+    "\x1b[[B": Keys.F2,  # Linux console.
+    "\x1b[[C": Keys.F3,  # Linux console.
+    "\x1b[[D": Keys.F4,  # Linux console.
+    "\x1b[[E": Keys.F5,  # Linux console.
+    "\x1b[11~": Keys.F1,  # rxvt-unicode
+    "\x1b[12~": Keys.F2,  # rxvt-unicode
+    "\x1b[13~": Keys.F3,  # rxvt-unicode
+    "\x1b[14~": Keys.F4,  # rxvt-unicode
+    "\x1b[15~": Keys.F5,
+    "\x1b[17~": Keys.F6,
+    "\x1b[18~": Keys.F7,
+    "\x1b[19~": Keys.F8,
+    "\x1b[20~": Keys.F9,
+    "\x1b[21~": Keys.F10,
+    "\x1b[23~": Keys.F11,
+    "\x1b[24~": Keys.F12,
+    "\x1b[25~": Keys.F13,
+    "\x1b[26~": Keys.F14,
+    "\x1b[28~": Keys.F15,
+    "\x1b[29~": Keys.F16,
+    "\x1b[31~": Keys.F17,
+    "\x1b[32~": Keys.F18,
+    "\x1b[33~": Keys.F19,
+    "\x1b[34~": Keys.F20,
+    # Xterm
+    "\x1b[1;2P": Keys.F13,
+    "\x1b[1;2Q": Keys.F14,
+    # '\x1b[1;2R': Keys.F15,  # Conflicts with CPR response.
+    "\x1b[1;2S": Keys.F16,
+    "\x1b[15;2~": Keys.F17,
+    "\x1b[17;2~": Keys.F18,
+    "\x1b[18;2~": Keys.F19,
+    "\x1b[19;2~": Keys.F20,
+    "\x1b[20;2~": Keys.F21,
+    "\x1b[21;2~": Keys.F22,
+    "\x1b[23;2~": Keys.F23,
+    "\x1b[24;2~": Keys.F24,
+    # --
+    # CSI 27 disambiguated modified "other" keys (xterm)
+    # Ref: https://invisible-island.net/xterm/modified-keys.html
+    # These are currently unsupported, so just re-map some common ones to the
+    # unmodified versions
+    "\x1b[27;2;13~": Keys.ControlM,  # Shift + Enter
+    "\x1b[27;5;13~": Keys.ControlM,  # Ctrl + Enter
+    "\x1b[27;6;13~": Keys.ControlM,  # Ctrl + Shift + Enter
+    # --
+    # Control + function keys.
+    "\x1b[1;5P": Keys.ControlF1,
+    "\x1b[1;5Q": Keys.ControlF2,
+    # "\x1b[1;5R": Keys.ControlF3,  # Conflicts with CPR response.
+    "\x1b[1;5S": Keys.ControlF4,
+    "\x1b[15;5~": Keys.ControlF5,
+    "\x1b[17;5~": Keys.ControlF6,
+    "\x1b[18;5~": Keys.ControlF7,
+    "\x1b[19;5~": Keys.ControlF8,
+    "\x1b[20;5~": Keys.ControlF9,
+    "\x1b[21;5~": Keys.ControlF10,
+    "\x1b[23;5~": Keys.ControlF11,
+    "\x1b[24;5~": Keys.ControlF12,
+    "\x1b[1;6P": Keys.ControlF13,
+    "\x1b[1;6Q": Keys.ControlF14,
+    # "\x1b[1;6R": Keys.ControlF15,  # Conflicts with CPR response.
+    "\x1b[1;6S": Keys.ControlF16,
+    "\x1b[15;6~": Keys.ControlF17,
+    "\x1b[17;6~": Keys.ControlF18,
+    "\x1b[18;6~": Keys.ControlF19,
+    "\x1b[19;6~": Keys.ControlF20,
+    "\x1b[20;6~": Keys.ControlF21,
+    "\x1b[21;6~": Keys.ControlF22,
+    "\x1b[23;6~": Keys.ControlF23,
+    "\x1b[24;6~": Keys.ControlF24,
+    # --
+    # Tmux (Win32 subsystem) sends the following scroll events.
+    "\x1b[62~": Keys.ScrollUp,
+    "\x1b[63~": Keys.ScrollDown,
+    "\x1b[200~": Keys.BracketedPaste,  # Start of bracketed paste.
+    # --
+    # Sequences generated by numpad 5. Not sure what it means. (It doesn't
+    # appear in 'infocmp'. Just ignore.
+    "\x1b[E": Keys.Ignore,  # Xterm.
+    "\x1b[G": Keys.Ignore,  # Linux console.
+    # --
+    # Meta/control/escape + pageup/pagedown/insert/delete.
+    "\x1b[3;2~": Keys.ShiftDelete,  # xterm, gnome-terminal.
+    "\x1b[5;2~": Keys.ShiftPageUp,
+    "\x1b[6;2~": Keys.ShiftPageDown,
+    "\x1b[2;3~": (Keys.Escape, Keys.Insert),
+    "\x1b[3;3~": (Keys.Escape, Keys.Delete),
+    "\x1b[5;3~": (Keys.Escape, Keys.PageUp),
+    "\x1b[6;3~": (Keys.Escape, Keys.PageDown),
+    "\x1b[2;4~": (Keys.Escape, Keys.ShiftInsert),
+    "\x1b[3;4~": (Keys.Escape, Keys.ShiftDelete),
+    "\x1b[5;4~": (Keys.Escape, Keys.ShiftPageUp),
+    "\x1b[6;4~": (Keys.Escape, Keys.ShiftPageDown),
+    "\x1b[3;5~": Keys.ControlDelete,  # xterm, gnome-terminal.
+    "\x1b[5;5~": Keys.ControlPageUp,
+    "\x1b[6;5~": Keys.ControlPageDown,
+    "\x1b[3;6~": Keys.ControlShiftDelete,
+    "\x1b[5;6~": Keys.ControlShiftPageUp,
+    "\x1b[6;6~": Keys.ControlShiftPageDown,
+    "\x1b[2;7~": (Keys.Escape, Keys.ControlInsert),
+    "\x1b[5;7~": (Keys.Escape, Keys.ControlPageDown),
+    "\x1b[6;7~": (Keys.Escape, Keys.ControlPageDown),
+    "\x1b[2;8~": (Keys.Escape, Keys.ControlShiftInsert),
+    "\x1b[5;8~": (Keys.Escape, Keys.ControlShiftPageDown),
+    "\x1b[6;8~": (Keys.Escape, Keys.ControlShiftPageDown),
+    # --
+    # Arrows.
+    # (Normal cursor mode).
+    "\x1b[A": Keys.Up,
+    "\x1b[B": Keys.Down,
+    "\x1b[C": Keys.Right,
+    "\x1b[D": Keys.Left,
+    "\x1b[H": Keys.Home,
+    "\x1b[F": Keys.End,
+    # Tmux sends following keystrokes when control+arrow is pressed, but for
+    # Emacs ansi-term sends the same sequences for normal arrow keys. Consider
+    # it a normal arrow press, because that's more important.
+    # (Application cursor mode).
+    "\x1bOA": Keys.Up,
+    "\x1bOB": Keys.Down,
+    "\x1bOC": Keys.Right,
+    "\x1bOD": Keys.Left,
+    "\x1bOF": Keys.End,
+    "\x1bOH": Keys.Home,
+    # Shift + arrows.
+    "\x1b[1;2A": Keys.ShiftUp,
+    "\x1b[1;2B": Keys.ShiftDown,
+    "\x1b[1;2C": Keys.ShiftRight,
+    "\x1b[1;2D": Keys.ShiftLeft,
+    "\x1b[1;2F": Keys.ShiftEnd,
+    "\x1b[1;2H": Keys.ShiftHome,
+    # Meta + arrow keys. Several terminals handle this differently.
+    # The following sequences are for xterm and gnome-terminal.
+    #     (Iterm sends ESC followed by the normal arrow_up/down/left/right
+    #     sequences, and the OSX Terminal sends ESCb and ESCf for "alt
+    #     arrow_left" and "alt arrow_right." We don't handle these
+    #     explicitly, in here, because would could not distinguish between
+    #     pressing ESC (to go to Vi navigation mode), followed by just the
+    #     'b' or 'f' key. These combinations are handled in
+    #     the input processor.)
+    "\x1b[1;3A": (Keys.Escape, Keys.Up),
+    "\x1b[1;3B": (Keys.Escape, Keys.Down),
+    "\x1b[1;3C": (Keys.Escape, Keys.Right),
+    "\x1b[1;3D": (Keys.Escape, Keys.Left),
+    "\x1b[1;3F": (Keys.Escape, Keys.End),
+    "\x1b[1;3H": (Keys.Escape, Keys.Home),
+    # Alt+shift+number.
+    "\x1b[1;4A": (Keys.Escape, Keys.ShiftDown),
+    "\x1b[1;4B": (Keys.Escape, Keys.ShiftUp),
+    "\x1b[1;4C": (Keys.Escape, Keys.ShiftRight),
+    "\x1b[1;4D": (Keys.Escape, Keys.ShiftLeft),
+    "\x1b[1;4F": (Keys.Escape, Keys.ShiftEnd),
+    "\x1b[1;4H": (Keys.Escape, Keys.ShiftHome),
+    # Control + arrows.
+    "\x1b[1;5A": Keys.ControlUp,  # Cursor Mode
+    "\x1b[1;5B": Keys.ControlDown,  # Cursor Mode
+    "\x1b[1;5C": Keys.ControlRight,  # Cursor Mode
+    "\x1b[1;5D": Keys.ControlLeft,  # Cursor Mode
+    "\x1b[1;5F": Keys.ControlEnd,
+    "\x1b[1;5H": Keys.ControlHome,
+    # Tmux sends following keystrokes when control+arrow is pressed, but for
+    # Emacs ansi-term sends the same sequences for normal arrow keys. Consider
+    # it a normal arrow press, because that's more important.
+    "\x1b[5A": Keys.ControlUp,
+    "\x1b[5B": Keys.ControlDown,
+    "\x1b[5C": Keys.ControlRight,
+    "\x1b[5D": Keys.ControlLeft,
+    "\x1bOc": Keys.ControlRight,  # rxvt
+    "\x1bOd": Keys.ControlLeft,  # rxvt
+    # Control + shift + arrows.
+    "\x1b[1;6A": Keys.ControlShiftDown,
+    "\x1b[1;6B": Keys.ControlShiftUp,
+    "\x1b[1;6C": Keys.ControlShiftRight,
+    "\x1b[1;6D": Keys.ControlShiftLeft,
+    "\x1b[1;6F": Keys.ControlShiftEnd,
+    "\x1b[1;6H": Keys.ControlShiftHome,
+    # Control + Meta + arrows.
+    "\x1b[1;7A": (Keys.Escape, Keys.ControlDown),
+    "\x1b[1;7B": (Keys.Escape, Keys.ControlUp),
+    "\x1b[1;7C": (Keys.Escape, Keys.ControlRight),
+    "\x1b[1;7D": (Keys.Escape, Keys.ControlLeft),
+    "\x1b[1;7F": (Keys.Escape, Keys.ControlEnd),
+    "\x1b[1;7H": (Keys.Escape, Keys.ControlHome),
+    # Meta + Shift + arrows.
+    "\x1b[1;8A": (Keys.Escape, Keys.ControlShiftDown),
+    "\x1b[1;8B": (Keys.Escape, Keys.ControlShiftUp),
+    "\x1b[1;8C": (Keys.Escape, Keys.ControlShiftRight),
+    "\x1b[1;8D": (Keys.Escape, Keys.ControlShiftLeft),
+    "\x1b[1;8F": (Keys.Escape, Keys.ControlShiftEnd),
+    "\x1b[1;8H": (Keys.Escape, Keys.ControlShiftHome),
+    # Meta + arrow on (some?) Macs when using iTerm defaults (see issue #483).
+    "\x1b[1;9A": (Keys.Escape, Keys.Up),
+    "\x1b[1;9B": (Keys.Escape, Keys.Down),
+    "\x1b[1;9C": (Keys.Escape, Keys.Right),
+    "\x1b[1;9D": (Keys.Escape, Keys.Left),
+    # --
+    # Control/shift/meta + number in mintty.
+    # (c-2 will actually send c-@ and c-6 will send c-^.)
+    "\x1b[1;5p": Keys.Control0,
+    "\x1b[1;5q": Keys.Control1,
+    "\x1b[1;5r": Keys.Control2,
+    "\x1b[1;5s": Keys.Control3,
+    "\x1b[1;5t": Keys.Control4,
+    "\x1b[1;5u": Keys.Control5,
+    "\x1b[1;5v": Keys.Control6,
+    "\x1b[1;5w": Keys.Control7,
+    "\x1b[1;5x": Keys.Control8,
+    "\x1b[1;5y": Keys.Control9,
+    "\x1b[1;6p": Keys.ControlShift0,
+    "\x1b[1;6q": Keys.ControlShift1,
+    "\x1b[1;6r": Keys.ControlShift2,
+    "\x1b[1;6s": Keys.ControlShift3,
+    "\x1b[1;6t": Keys.ControlShift4,
+    "\x1b[1;6u": Keys.ControlShift5,
+    "\x1b[1;6v": Keys.ControlShift6,
+    "\x1b[1;6w": Keys.ControlShift7,
+    "\x1b[1;6x": Keys.ControlShift8,
+    "\x1b[1;6y": Keys.ControlShift9,
+    "\x1b[1;7p": (Keys.Escape, Keys.Control0),
+    "\x1b[1;7q": (Keys.Escape, Keys.Control1),
+    "\x1b[1;7r": (Keys.Escape, Keys.Control2),
+    "\x1b[1;7s": (Keys.Escape, Keys.Control3),
+    "\x1b[1;7t": (Keys.Escape, Keys.Control4),
+    "\x1b[1;7u": (Keys.Escape, Keys.Control5),
+    "\x1b[1;7v": (Keys.Escape, Keys.Control6),
+    "\x1b[1;7w": (Keys.Escape, Keys.Control7),
+    "\x1b[1;7x": (Keys.Escape, Keys.Control8),
+    "\x1b[1;7y": (Keys.Escape, Keys.Control9),
+    "\x1b[1;8p": (Keys.Escape, Keys.ControlShift0),
+    "\x1b[1;8q": (Keys.Escape, Keys.ControlShift1),
+    "\x1b[1;8r": (Keys.Escape, Keys.ControlShift2),
+    "\x1b[1;8s": (Keys.Escape, Keys.ControlShift3),
+    "\x1b[1;8t": (Keys.Escape, Keys.ControlShift4),
+    "\x1b[1;8u": (Keys.Escape, Keys.ControlShift5),
+    "\x1b[1;8v": (Keys.Escape, Keys.ControlShift6),
+    "\x1b[1;8w": (Keys.Escape, Keys.ControlShift7),
+    "\x1b[1;8x": (Keys.Escape, Keys.ControlShift8),
+    "\x1b[1;8y": (Keys.Escape, Keys.ControlShift9),
+}
+
+
+def _get_reverse_ansi_sequences() -> Dict[Keys, str]:
+    """
+    Create a dictionary that maps prompt_toolkit keys back to the VT100 escape
+    sequences.
+    """
+    result: Dict[Keys, str] = {}
+
+    for sequence, key in ANSI_SEQUENCES.items():
+        if not isinstance(key, tuple):
+            if key not in result:
+                result[key] = sequence
+
+    return result
+
+
+REVERSE_ANSI_SEQUENCES = _get_reverse_ansi_sequences()
diff --git a/src/prompt_toolkit/input/base.py b/src/prompt_toolkit/input/base.py
new file mode 100644
index 0000000..313622d
--- /dev/null
+++ b/src/prompt_toolkit/input/base.py
@@ -0,0 +1,150 @@
+"""
+Abstraction of CLI Input.
+"""
+from abc import ABCMeta, abstractmethod, abstractproperty
+from contextlib import contextmanager
+from typing import Callable, ContextManager, Generator, List
+
+from prompt_toolkit.key_binding import KeyPress
+
+__all__ = [
+    "Input",
+    "PipeInput",
+    "DummyInput",
+]
+
+
+class Input(metaclass=ABCMeta):
+    """
+    Abstraction for any input.
+
+    An instance of this class can be given to the constructor of a
+    :class:`~prompt_toolkit.application.Application` and will also be
+    passed to the :class:`~prompt_toolkit.eventloop.base.EventLoop`.
+    """
+
+    @abstractmethod
+    def fileno(self) -> int:
+        """
+        Fileno for putting this in an event loop.
+        """
+
+    @abstractmethod
+    def typeahead_hash(self) -> str:
+        """
+        Identifier for storing type ahead key presses.
+        """
+
+    @abstractmethod
+    def read_keys(self) -> List[KeyPress]:
+        """
+        Return a list of Key objects which are read/parsed from the input.
+        """
+
+    def flush_keys(self) -> List[KeyPress]:
+        """
+        Flush the underlying parser. and return the pending keys.
+        (Used for vt100 input.)
+        """
+        return []
+
+    def flush(self) -> None:
+        "The event loop can call this when the input has to be flushed."
+        pass
+
+    @abstractproperty
+    def closed(self) -> bool:
+        "Should be true when the input stream is closed."
+        return False
+
+    @abstractmethod
+    def raw_mode(self) -> ContextManager[None]:
+        """
+        Context manager that turns the input into raw mode.
+        """
+
+    @abstractmethod
+    def cooked_mode(self) -> ContextManager[None]:
+        """
+        Context manager that turns the input into cooked mode.
+        """
+
+    @abstractmethod
+    def attach(self, input_ready_callback: Callable[[], None]) -> ContextManager[None]:
+        """
+        Return a context manager that makes this input active in the current
+        event loop.
+        """
+
+    @abstractmethod
+    def detach(self) -> ContextManager[None]:
+        """
+        Return a context manager that makes sure that this input is not active
+        in the current event loop.
+        """
+
+    def close(self) -> None:
+        "Close input."
+        pass
+
+
+class PipeInput(Input):
+    """
+    Abstraction for pipe input.
+    """
+
+    @abstractmethod
+    def send_bytes(self, data: bytes) -> None:
+        """Feed byte string into the pipe"""
+
+    @abstractmethod
+    def send_text(self, data: str) -> None:
+        """Feed a text string into the pipe"""
+
+
+class DummyInput(Input):
+    """
+    Input for use in a `DummyApplication`
+
+    If used in an actual application, it will make the application render
+    itself once and exit immediately, due to an `EOFError`.
+    """
+
+    def fileno(self) -> int:
+        raise NotImplementedError
+
+    def typeahead_hash(self) -> str:
+        return "dummy-%s" % id(self)
+
+    def read_keys(self) -> List[KeyPress]:
+        return []
+
+    @property
+    def closed(self) -> bool:
+        # This needs to be true, so that the dummy input will trigger an
+        # `EOFError` immediately in the application.
+        return True
+
+    def raw_mode(self) -> ContextManager[None]:
+        return _dummy_context_manager()
+
+    def cooked_mode(self) -> ContextManager[None]:
+        return _dummy_context_manager()
+
+    def attach(self, input_ready_callback: Callable[[], None]) -> ContextManager[None]:
+        # Call the callback immediately once after attaching.
+        # This tells the callback to call `read_keys` and check the
+        # `input.closed` flag, after which it won't receive any keys, but knows
+        # that `EOFError` should be raised. This unblocks `read_from_input` in
+        # `application.py`.
+        input_ready_callback()
+
+        return _dummy_context_manager()
+
+    def detach(self) -> ContextManager[None]:
+        return _dummy_context_manager()
+
+
+@contextmanager
+def _dummy_context_manager() -> Generator[None, None, None]:
+    yield
diff --git a/src/prompt_toolkit/input/defaults.py b/src/prompt_toolkit/input/defaults.py
new file mode 100644
index 0000000..564f848
--- /dev/null
+++ b/src/prompt_toolkit/input/defaults.py
@@ -0,0 +1,79 @@
+import io
+import sys
+from typing import ContextManager, Optional, TextIO
+
+from .base import DummyInput, Input, PipeInput
+
+__all__ = [
+    "create_input",
+    "create_pipe_input",
+]
+
+
+def create_input(
+    stdin: Optional[TextIO] = None, always_prefer_tty: bool = False
+) -> Input:
+    """
+    Create the appropriate `Input` object for the current os/environment.
+
+    :param always_prefer_tty: When set, if `sys.stdin` is connected to a Unix
+        `pipe`, check whether `sys.stdout` or `sys.stderr` are connected to a
+        pseudo terminal. If so, open the tty for reading instead of reading for
+        `sys.stdin`. (We can open `stdout` or `stderr` for reading, this is how
+        a `$PAGER` works.)
+    """
+    if sys.platform == "win32":
+        from .win32 import Win32Input
+
+        # If `stdin` was assigned `None` (which happens with pythonw.exe), use
+        # a `DummyInput`. This triggers `EOFError` in the application code.
+        if stdin is None and sys.stdin is None:
+            return DummyInput()
+
+        return Win32Input(stdin or sys.stdin)
+    else:
+        from .vt100 import Vt100Input
+
+        # If no input TextIO is given, use stdin/stdout.
+        if stdin is None:
+            stdin = sys.stdin
+
+            if always_prefer_tty:
+                for obj in [sys.stdin, sys.stdout, sys.stderr]:
+                    if obj.isatty():
+                        stdin = obj
+                        break
+
+        # If we can't access the file descriptor for the selected stdin, return
+        # a `DummyInput` instead. This can happen for instance in unit tests,
+        # when `sys.stdin` is patched by something that's not an actual file.
+        # (Instantiating `Vt100Input` would fail in this case.)
+        try:
+            stdin.fileno()
+        except io.UnsupportedOperation:
+            return DummyInput()
+
+        return Vt100Input(stdin)
+
+
+def create_pipe_input() -> ContextManager[PipeInput]:
+    """
+    Create an input pipe.
+    This is mostly useful for unit testing.
+
+    Usage::
+
+        with create_pipe_input() as input:
+            input.send_text('inputdata')
+
+    Breaking change: In prompt_toolkit 3.0.28 and earlier, this was returning
+    the `PipeInput` directly, rather than through a context manager.
+    """
+    if sys.platform == "win32":
+        from .win32_pipe import Win32PipeInput
+
+        return Win32PipeInput.create()
+    else:
+        from .posix_pipe import PosixPipeInput
+
+        return PosixPipeInput.create()
diff --git a/src/prompt_toolkit/input/posix_pipe.py b/src/prompt_toolkit/input/posix_pipe.py
new file mode 100644
index 0000000..1e7dec7
--- /dev/null
+++ b/src/prompt_toolkit/input/posix_pipe.py
@@ -0,0 +1,116 @@
+import sys
+
+assert sys.platform != "win32"
+
+import os
+from contextlib import contextmanager
+from typing import ContextManager, Iterator, TextIO, cast
+
+from ..utils import DummyContext
+from .base import PipeInput
+from .vt100 import Vt100Input
+
+__all__ = [
+    "PosixPipeInput",
+]
+
+
+class _Pipe:
+    "Wrapper around os.pipe, that ensures we don't double close any end."
+
+    def __init__(self) -> None:
+        self.read_fd, self.write_fd = os.pipe()
+        self._read_closed = False
+        self._write_closed = False
+
+    def close_read(self) -> None:
+        "Close read-end if not yet closed."
+        if self._read_closed:
+            return
+
+        os.close(self.read_fd)
+        self._read_closed = True
+
+    def close_write(self) -> None:
+        "Close write-end if not yet closed."
+        if self._write_closed:
+            return
+
+        os.close(self.write_fd)
+        self._write_closed = True
+
+    def close(self) -> None:
+        "Close both read and write ends."
+        self.close_read()
+        self.close_write()
+
+
+class PosixPipeInput(Vt100Input, PipeInput):
+    """
+    Input that is send through a pipe.
+    This is useful if we want to send the input programmatically into the
+    application. Mostly useful for unit testing.
+
+    Usage::
+
+        with PosixPipeInput.create() as input:
+            input.send_text('inputdata')
+    """
+
+    _id = 0
+
+    def __init__(self, _pipe: _Pipe, _text: str = "") -> None:
+        # Private constructor. Users should use the public `.create()` method.
+        self.pipe = _pipe
+
+        class Stdin:
+            encoding = "utf-8"
+
+            def isatty(stdin) -> bool:
+                return True
+
+            def fileno(stdin) -> int:
+                return self.pipe.read_fd
+
+        super().__init__(cast(TextIO, Stdin()))
+        self.send_text(_text)
+
+        # Identifier for every PipeInput for the hash.
+        self.__class__._id += 1
+        self._id = self.__class__._id
+
+    @classmethod
+    @contextmanager
+    def create(cls, text: str = "") -> Iterator["PosixPipeInput"]:
+        pipe = _Pipe()
+        try:
+            yield PosixPipeInput(_pipe=pipe, _text=text)
+        finally:
+            pipe.close()
+
+    def send_bytes(self, data: bytes) -> None:
+        os.write(self.pipe.write_fd, data)
+
+    def send_text(self, data: str) -> None:
+        "Send text to the input."
+        os.write(self.pipe.write_fd, data.encode("utf-8"))
+
+    def raw_mode(self) -> ContextManager[None]:
+        return DummyContext()
+
+    def cooked_mode(self) -> ContextManager[None]:
+        return DummyContext()
+
+    def close(self) -> None:
+        "Close pipe fds."
+        # Only close the write-end of the pipe. This will unblock the reader
+        # callback (in vt100.py > _attached_input), which eventually will raise
+        # `EOFError`. If we'd also close the read-end, then the event loop
+        # won't wake up the corresponding callback because of this.
+        self.pipe.close_write()
+
+    def typeahead_hash(self) -> str:
+        """
+        This needs to be unique for every `PipeInput`.
+        """
+        return f"pipe-input-{self._id}"
diff --git a/src/prompt_toolkit/input/posix_utils.py b/src/prompt_toolkit/input/posix_utils.py
new file mode 100644
index 0000000..7cf31ee
--- /dev/null
+++ b/src/prompt_toolkit/input/posix_utils.py
@@ -0,0 +1,95 @@
+import os
+import select
+from codecs import getincrementaldecoder
+
+__all__ = [
+    "PosixStdinReader",
+]
+
+
+class PosixStdinReader:
+    """
+    Wrapper around stdin which reads (nonblocking) the next available 1024
+    bytes and decodes it.
+
+    Note that you can't be sure that the input file is closed if the ``read``
+    function returns an empty string. When ``errors=ignore`` is passed,
+    ``read`` can return an empty string if all malformed input was replaced by
+    an empty string. (We can't block here and wait for more input.) So, because
+    of that, check the ``closed`` attribute, to be sure that the file has been
+    closed.
+
+    :param stdin_fd: File descriptor from which we read.
+    :param errors:  Can be 'ignore', 'strict' or 'replace'.
+        On Python3, this can be 'surrogateescape', which is the default.
+
+        'surrogateescape' is preferred, because this allows us to transfer
+        unrecognised bytes to the key bindings. Some terminals, like lxterminal
+        and Guake, use the 'Mxx' notation to send mouse events, where each 'x'
+        can be any possible byte.
+    """
+
+    # By default, we want to 'ignore' errors here. The input stream can be full
+    # of junk.  One occurrence of this that I had was when using iTerm2 on OS X,
+    # with "Option as Meta" checked (You should choose "Option as +Esc".)
+
+    def __init__(
+        self, stdin_fd: int, errors: str = "surrogateescape", encoding: str = "utf-8"
+    ) -> None:
+        self.stdin_fd = stdin_fd
+        self.errors = errors
+
+        # Create incremental decoder for decoding stdin.
+        # We can not just do `os.read(stdin.fileno(), 1024).decode('utf-8')`, because
+        # it could be that we are in the middle of a utf-8 byte sequence.
+        self._stdin_decoder_cls = getincrementaldecoder(encoding)
+        self._stdin_decoder = self._stdin_decoder_cls(errors=errors)
+
+        #: True when there is nothing anymore to read.
+        self.closed = False
+
+    def read(self, count: int = 1024) -> str:
+        # By default we choose a rather small chunk size, because reading
+        # big amounts of input at once, causes the event loop to process
+        # all these key bindings also at once without going back to the
+        # loop. This will make the application feel unresponsive.
+        """
+        Read the input and return it as a string.
+
+        Return the text. Note that this can return an empty string, even when
+        the input stream was not yet closed. This means that something went
+        wrong during the decoding.
+        """
+        if self.closed:
+            return ""
+
+        # Check whether there is some input to read. `os.read` would block
+        # otherwise.
+        # (Actually, the event loop is responsible to make sure that this
+        # function is only called when there is something to read, but for some
+        # reason this happens in certain situations.)
+        try:
+            if not select.select([self.stdin_fd], [], [], 0)[0]:
+                return ""
+        except OSError:
+            # Happens for instance when the file descriptor was closed.
+            # (We had this in ptterm, where the FD became ready, a callback was
+            # scheduled, but in the meantime another callback closed it already.)
+            self.closed = True
+
+        # Note: the following works better than wrapping `self.stdin` like
+        #       `codecs.getreader('utf-8')(stdin)` and doing `read(1)`.
+        #       Somehow that causes some latency when the escape
+        #       character is pressed. (Especially on combination with the `select`.)
+        try:
+            data = os.read(self.stdin_fd, count)
+
+            # Nothing more to read, stream is closed.
+            if data == b"":
+                self.closed = True
+                return ""
+        except OSError:
+            # In case of SIGWINCH
+            data = b""
+
+        return self._stdin_decoder.decode(data)
diff --git a/src/prompt_toolkit/input/typeahead.py b/src/prompt_toolkit/input/typeahead.py
new file mode 100644
index 0000000..a3d7866
--- /dev/null
+++ b/src/prompt_toolkit/input/typeahead.py
@@ -0,0 +1,76 @@
+r"""
+Store input key strokes if we did read more than was required.
+
+The input classes `Vt100Input` and `Win32Input` read the input text in chunks
+of a few kilobytes. This means that if we read input from stdin, it could be
+that we read a couple of lines (with newlines in between) at once.
+
+This creates a problem: potentially, we read too much from stdin. Sometimes
+people paste several lines at once because they paste input in a REPL and
+expect each input() call to process one line. Or they rely on type ahead
+because the application can't keep up with the processing.
+
+However, we need to read input in bigger chunks. We need this mostly to support
+pasting of larger chunks of text. We don't want everything to become
+unresponsive because we:
+  - read one character;
+  - parse one character;
+  - call the key binding, which does a string operation with one character;
+  - and render the user interface.
+Doing text operations on single characters is very inefficient in Python, so we
+prefer to work on bigger chunks of text. This is why we have to read the input
+in bigger chunks.
+
+Further, line buffering is also not an option, because it doesn't work well in
+the architecture. We use lower level Posix APIs, that work better with the
+event loop and so on. In fact, there is also nothing that defines that only \n
+can accept the input, you could create a key binding for any key to accept the
+input.
+
+To support type ahead, this module will store all the key strokes that were
+read too early, so that they can be feed into to the next `prompt()` call or to
+the next prompt_toolkit `Application`.
+"""
+from collections import defaultdict
+from typing import Dict, List
+
+from ..key_binding import KeyPress
+from .base import Input
+
+__all__ = [
+    "store_typeahead",
+    "get_typeahead",
+    "clear_typeahead",
+]
+
+_buffer: Dict[str, List[KeyPress]] = defaultdict(list)
+
+
+def store_typeahead(input_obj: Input, key_presses: List[KeyPress]) -> None:
+    """
+    Insert typeahead key presses for the given input.
+    """
+    global _buffer
+    key = input_obj.typeahead_hash()
+    _buffer[key].extend(key_presses)
+
+
+def get_typeahead(input_obj: Input) -> List[KeyPress]:
+    """
+    Retrieve typeahead and reset the buffer for this input.
+    """
+    global _buffer
+
+    key = input_obj.typeahead_hash()
+    result = _buffer[key]
+    _buffer[key] = []
+    return result
+
+
+def clear_typeahead(input_obj: Input) -> None:
+    """
+    Clear typeahead buffer.
+    """
+    global _buffer
+    key = input_obj.typeahead_hash()
+    _buffer[key] = []
diff --git a/src/prompt_toolkit/input/vt100.py b/src/prompt_toolkit/input/vt100.py
new file mode 100644
index 0000000..45ce372
--- /dev/null
+++ b/src/prompt_toolkit/input/vt100.py
@@ -0,0 +1,320 @@
+import sys
+
+assert sys.platform != "win32"
+
+import contextlib
+import io
+import termios
+import tty
+from asyncio import AbstractEventLoop
+from typing import (
+    Callable,
+    ContextManager,
+    Dict,
+    Generator,
+    List,
+    Optional,
+    Set,
+    TextIO,
+    Tuple,
+    Union,
+)
+
+from prompt_toolkit.eventloop import get_event_loop
+
+from ..key_binding import KeyPress
+from .base import Input
+from .posix_utils import PosixStdinReader
+from .vt100_parser import Vt100Parser
+
+__all__ = [
+    "Vt100Input",
+    "raw_mode",
+    "cooked_mode",
+]
+
+
+class Vt100Input(Input):
+    """
+    Vt100 input for Posix systems.
+    (This uses a posix file descriptor that can be registered in the event loop.)
+    """
+
+    # For the error messages. Only display "Input is not a terminal" once per
+    # file descriptor.
+    _fds_not_a_terminal: Set[int] = set()
+
+    def __init__(self, stdin: TextIO) -> None:
+        # Test whether the given input object has a file descriptor.
+        # (Idle reports stdin to be a TTY, but fileno() is not implemented.)
+        try:
+            # This should not raise, but can return 0.
+            stdin.fileno()
+        except io.UnsupportedOperation as e:
+            if "idlelib.run" in sys.modules:
+                raise io.UnsupportedOperation(
+                    "Stdin is not a terminal. Running from Idle is not supported."
+                ) from e
+            else:
+                raise io.UnsupportedOperation("Stdin is not a terminal.") from e
+
+        # Even when we have a file descriptor, it doesn't mean it's a TTY.
+        # Normally, this requires a real TTY device, but people instantiate
+        # this class often during unit tests as well. They use for instance
+        # pexpect to pipe data into an application. For convenience, we print
+        # an error message and go on.
+        isatty = stdin.isatty()
+        fd = stdin.fileno()
+
+        if not isatty and fd not in Vt100Input._fds_not_a_terminal:
+            msg = "Warning: Input is not a terminal (fd=%r).\n"
+            sys.stderr.write(msg % fd)
+            sys.stderr.flush()
+            Vt100Input._fds_not_a_terminal.add(fd)
+
+        #
+        self.stdin = stdin
+
+        # Create a backup of the fileno(). We want this to work even if the
+        # underlying file is closed, so that `typeahead_hash()` keeps working.
+        self._fileno = stdin.fileno()
+
+        self._buffer: List[KeyPress] = []  # Buffer to collect the Key objects.
+        self.stdin_reader = PosixStdinReader(self._fileno, encoding=stdin.encoding)
+        self.vt100_parser = Vt100Parser(
+            lambda key_press: self._buffer.append(key_press)
+        )
+
+    def attach(self, input_ready_callback: Callable[[], None]) -> ContextManager[None]:
+        """
+        Return a context manager that makes this input active in the current
+        event loop.
+        """
+        return _attached_input(self, input_ready_callback)
+
+    def detach(self) -> ContextManager[None]:
+        """
+        Return a context manager that makes sure that this input is not active
+        in the current event loop.
+        """
+        return _detached_input(self)
+
+    def read_keys(self) -> List[KeyPress]:
+        "Read list of KeyPress."
+        # Read text from stdin.
+        data = self.stdin_reader.read()
+
+        # Pass it through our vt100 parser.
+        self.vt100_parser.feed(data)
+
+        # Return result.
+        result = self._buffer
+        self._buffer = []
+        return result
+
+    def flush_keys(self) -> List[KeyPress]:
+        """
+        Flush pending keys and return them.
+        (Used for flushing the 'escape' key.)
+        """
+        # Flush all pending keys. (This is most important to flush the vt100
+        # 'Escape' key early when nothing else follows.)
+        self.vt100_parser.flush()
+
+        # Return result.
+        result = self._buffer
+        self._buffer = []
+        return result
+
+    @property
+    def closed(self) -> bool:
+        return self.stdin_reader.closed
+
+    def raw_mode(self) -> ContextManager[None]:
+        return raw_mode(self.stdin.fileno())
+
+    def cooked_mode(self) -> ContextManager[None]:
+        return cooked_mode(self.stdin.fileno())
+
+    def fileno(self) -> int:
+        return self.stdin.fileno()
+
+    def typeahead_hash(self) -> str:
+        return f"fd-{self._fileno}"
+
+
+_current_callbacks: Dict[
+    Tuple[AbstractEventLoop, int], Optional[Callable[[], None]]
+] = {}  # (loop, fd) -> current callback
+
+
+@contextlib.contextmanager
+def _attached_input(
+    input: Vt100Input, callback: Callable[[], None]
+) -> Generator[None, None, None]:
+    """
+    Context manager that makes this input active in the current event loop.
+
+    :param input: :class:`~prompt_toolkit.input.Input` object.
+    :param callback: Called when the input is ready to read.
+    """
+    loop = get_event_loop()
+    fd = input.fileno()
+    previous = _current_callbacks.get((loop, fd))
+
+    def callback_wrapper() -> None:
+        """Wrapper around the callback that already removes the reader when
+        the input is closed. Otherwise, we keep continuously calling this
+        callback, until we leave the context manager (which can happen a bit
+        later). This fixes issues when piping /dev/null into a prompt_toolkit
+        application."""
+        if input.closed:
+            loop.remove_reader(fd)
+        callback()
+
+    try:
+        loop.add_reader(fd, callback_wrapper)
+    except PermissionError:
+        # For `EPollSelector`, adding /dev/null to the event loop will raise
+        # `PermisisonError` (that doesn't happen for `SelectSelector`
+        # apparently). Whenever we get a `PermissionError`, we can raise
+        # `EOFError`, because there's not more to be read anyway. `EOFError` is
+        # an exception that people expect in
+        # `prompt_toolkit.application.Application.run()`.
+        # To reproduce, do: `ptpython 0< /dev/null 1< /dev/null`
+        raise EOFError
+
+    _current_callbacks[loop, fd] = callback
+
+    try:
+        yield
+    finally:
+        loop.remove_reader(fd)
+
+        if previous:
+            loop.add_reader(fd, previous)
+            _current_callbacks[loop, fd] = previous
+        else:
+            del _current_callbacks[loop, fd]
+
+
+@contextlib.contextmanager
+def _detached_input(input: Vt100Input) -> Generator[None, None, None]:
+    loop = get_event_loop()
+    fd = input.fileno()
+    previous = _current_callbacks.get((loop, fd))
+
+    if previous:
+        loop.remove_reader(fd)
+        _current_callbacks[loop, fd] = None
+
+    try:
+        yield
+    finally:
+        if previous:
+            loop.add_reader(fd, previous)
+            _current_callbacks[loop, fd] = previous
+
+
+class raw_mode:
+    """
+    ::
+
+        with raw_mode(stdin):
+            ''' the pseudo-terminal stdin is now used in raw mode '''
+
+    We ignore errors when executing `tcgetattr` fails.
+    """
+
+    # There are several reasons for ignoring errors:
+    # 1. To avoid the "Inappropriate ioctl for device" crash if somebody would
+    #    execute this code (In a Python REPL, for instance):
+    #
+    #         import os; f = open(os.devnull); os.dup2(f.fileno(), 0)
+    #
+    #    The result is that the eventloop will stop correctly, because it has
+    #    to logic to quit when stdin is closed. However, we should not fail at
+    #    this point. See:
+    #      https://github.com/jonathanslenders/python-prompt-toolkit/pull/393
+    #      https://github.com/jonathanslenders/python-prompt-toolkit/issues/392
+
+    # 2. Related, when stdin is an SSH pipe, and no full terminal was allocated.
+    #    See: https://github.com/jonathanslenders/python-prompt-toolkit/pull/165
+    def __init__(self, fileno: int) -> None:
+        self.fileno = fileno
+        self.attrs_before: Optional[List[Union[int, List[Union[bytes, int]]]]]
+        try:
+            self.attrs_before = termios.tcgetattr(fileno)
+        except termios.error:
+            # Ignore attribute errors.
+            self.attrs_before = None
+
+    def __enter__(self) -> None:
+        # NOTE: On os X systems, using pty.setraw() fails. Therefor we are using this:
+        try:
+            newattr = termios.tcgetattr(self.fileno)
+        except termios.error:
+            pass
+        else:
+            newattr[tty.LFLAG] = self._patch_lflag(newattr[tty.LFLAG])
+            newattr[tty.IFLAG] = self._patch_iflag(newattr[tty.IFLAG])
+
+            # VMIN defines the number of characters read at a time in
+            # non-canonical mode. It seems to default to 1 on Linux, but on
+            # Solaris and derived operating systems it defaults to 4. (This is
+            # because the VMIN slot is the same as the VEOF slot, which
+            # defaults to ASCII EOT = Ctrl-D = 4.)
+            newattr[tty.CC][termios.VMIN] = 1
+
+            termios.tcsetattr(self.fileno, termios.TCSANOW, newattr)
+
+    @classmethod
+    def _patch_lflag(cls, attrs: int) -> int:
+        return attrs & ~(termios.ECHO | termios.ICANON | termios.IEXTEN | termios.ISIG)
+
+    @classmethod
+    def _patch_iflag(cls, attrs: int) -> int:
+        return attrs & ~(
+            # Disable XON/XOFF flow control on output and input.
+            # (Don't capture Ctrl-S and Ctrl-Q.)
+            # Like executing: "stty -ixon."
+            termios.IXON
+            | termios.IXOFF
+            |
+            # Don't translate carriage return into newline on input.
+            termios.ICRNL
+            | termios.INLCR
+            | termios.IGNCR
+        )
+
+    def __exit__(self, *a: object) -> None:
+        if self.attrs_before is not None:
+            try:
+                termios.tcsetattr(self.fileno, termios.TCSANOW, self.attrs_before)
+            except termios.error:
+                pass
+
+            # # Put the terminal in application mode.
+            # self._stdout.write('\x1b[?1h')
+
+
+class cooked_mode(raw_mode):
+    """
+    The opposite of ``raw_mode``, used when we need cooked mode inside a
+    `raw_mode` block.  Used in `Application.run_in_terminal`.::
+
+        with cooked_mode(stdin):
+            ''' the pseudo-terminal stdin is now used in cooked mode. '''
+    """
+
+    @classmethod
+    def _patch_lflag(cls, attrs: int) -> int:
+        return attrs | (termios.ECHO | termios.ICANON | termios.IEXTEN | termios.ISIG)
+
+    @classmethod
+    def _patch_iflag(cls, attrs: int) -> int:
+        # Turn the ICRNL flag back on. (Without this, calling `input()` in
+        # run_in_terminal doesn't work and displays ^M instead. Ptpython
+        # evaluates commands using `run_in_terminal`, so it's important that
+        # they translate ^M back into ^J.)
+        return attrs | termios.ICRNL
diff --git a/src/prompt_toolkit/input/vt100_parser.py b/src/prompt_toolkit/input/vt100_parser.py
new file mode 100644
index 0000000..3ee1e14
--- /dev/null
+++ b/src/prompt_toolkit/input/vt100_parser.py
@@ -0,0 +1,247 @@
+"""
+Parser for VT100 input stream.
+"""
+import re
+from typing import Callable, Dict, Generator, Tuple, Union
+
+from ..key_binding.key_processor import KeyPress
+from ..keys import Keys
+from .ansi_escape_sequences import ANSI_SEQUENCES
+
+__all__ = [
+    "Vt100Parser",
+]
+
+
+# Regex matching any CPR response
+# (Note that we use '\Z' instead of '$', because '$' could include a trailing
+# newline.)
+_cpr_response_re = re.compile("^" + re.escape("\x1b[") + r"\d+;\d+R\Z")
+
+# Mouse events:
+# Typical: "Esc[MaB*"  Urxvt: "Esc[96;14;13M" and for Xterm SGR: "Esc[<64;85;12M"
+_mouse_event_re = re.compile("^" + re.escape("\x1b[") + r"(<?[\d;]+[mM]|M...)\Z")
+
+# Regex matching any valid prefix of a CPR response.
+# (Note that it doesn't contain the last character, the 'R'. The prefix has to
+# be shorter.)
+_cpr_response_prefix_re = re.compile("^" + re.escape("\x1b[") + r"[\d;]*\Z")
+
+_mouse_event_prefix_re = re.compile("^" + re.escape("\x1b[") + r"(<?[\d;]*|M.{0,2})\Z")
+
+
+class _Flush:
+    """Helper object to indicate flush operation to the parser."""
+
+    pass
+
+
+class _IsPrefixOfLongerMatchCache(Dict[str, bool]):
+    """
+    Dictionary that maps input sequences to a boolean indicating whether there is
+    any key that start with this characters.
+    """
+
+    def __missing__(self, prefix: str) -> bool:
+        # (hard coded) If this could be a prefix of a CPR response, return
+        # True.
+        if _cpr_response_prefix_re.match(prefix) or _mouse_event_prefix_re.match(
+            prefix
+        ):
+            result = True
+        else:
+            # If this could be a prefix of anything else, also return True.
+            result = any(
+                v
+                for k, v in ANSI_SEQUENCES.items()
+                if k.startswith(prefix) and k != prefix
+            )
+
+        self[prefix] = result
+        return result
+
+
+_IS_PREFIX_OF_LONGER_MATCH_CACHE = _IsPrefixOfLongerMatchCache()
+
+
+class Vt100Parser:
+    """
+    Parser for VT100 input stream.
+    Data can be fed through the `feed` method and the given callback will be
+    called with KeyPress objects.
+
+    ::
+
+        def callback(key):
+            pass
+        i = Vt100Parser(callback)
+        i.feed('data\x01...')
+
+    :attr feed_key_callback: Function that will be called when a key is parsed.
+    """
+
+    # Lookup table of ANSI escape sequences for a VT100 terminal
+    # Hint: in order to know what sequences your terminal writes to stdin, run
+    #       "od -c" and start typing.
+    def __init__(self, feed_key_callback: Callable[[KeyPress], None]) -> None:
+        self.feed_key_callback = feed_key_callback
+        self.reset()
+
+    def reset(self, request: bool = False) -> None:
+        self._in_bracketed_paste = False
+        self._start_parser()
+
+    def _start_parser(self) -> None:
+        """
+        Start the parser coroutine.
+        """
+        self._input_parser = self._input_parser_generator()
+        self._input_parser.send(None)  # type: ignore
+
+    def _get_match(self, prefix: str) -> Union[None, Keys, Tuple[Keys, ...]]:
+        """
+        Return the key (or keys) that maps to this prefix.
+        """
+        # (hard coded) If we match a CPR response, return Keys.CPRResponse.
+        # (This one doesn't fit in the ANSI_SEQUENCES, because it contains
+        # integer variables.)
+        if _cpr_response_re.match(prefix):
+            return Keys.CPRResponse
+
+        elif _mouse_event_re.match(prefix):
+            return Keys.Vt100MouseEvent
+
+        # Otherwise, use the mappings.
+        try:
+            return ANSI_SEQUENCES[prefix]
+        except KeyError:
+            return None
+
+    def _input_parser_generator(self) -> Generator[None, Union[str, _Flush], None]:
+        """
+        Coroutine (state machine) for the input parser.
+        """
+        prefix = ""
+        retry = False
+        flush = False
+
+        while True:
+            flush = False
+
+            if retry:
+                retry = False
+            else:
+                # Get next character.
+                c = yield
+
+                if isinstance(c, _Flush):
+                    flush = True
+                else:
+                    prefix += c
+
+            # If we have some data, check for matches.
+            if prefix:
+                is_prefix_of_longer_match = _IS_PREFIX_OF_LONGER_MATCH_CACHE[prefix]
+                match = self._get_match(prefix)
+
+                # Exact matches found, call handlers..
+                if (flush or not is_prefix_of_longer_match) and match:
+                    self._call_handler(match, prefix)
+                    prefix = ""
+
+                # No exact match found.
+                elif (flush or not is_prefix_of_longer_match) and not match:
+                    found = False
+                    retry = True
+
+                    # Loop over the input, try the longest match first and
+                    # shift.
+                    for i in range(len(prefix), 0, -1):
+                        match = self._get_match(prefix[:i])
+                        if match:
+                            self._call_handler(match, prefix[:i])
+                            prefix = prefix[i:]
+                            found = True
+
+                    if not found:
+                        self._call_handler(prefix[0], prefix[0])
+                        prefix = prefix[1:]
+
+    def _call_handler(
+        self, key: Union[str, Keys, Tuple[Keys, ...]], insert_text: str
+    ) -> None:
+        """
+        Callback to handler.
+        """
+        if isinstance(key, tuple):
+            # Received ANSI sequence that corresponds with multiple keys
+            # (probably alt+something). Handle keys individually, but only pass
+            # data payload to first KeyPress (so that we won't insert it
+            # multiple times).
+            for i, k in enumerate(key):
+                self._call_handler(k, insert_text if i == 0 else "")
+        else:
+            if key == Keys.BracketedPaste:
+                self._in_bracketed_paste = True
+                self._paste_buffer = ""
+            else:
+                self.feed_key_callback(KeyPress(key, insert_text))
+
+    def feed(self, data: str) -> None:
+        """
+        Feed the input stream.
+
+        :param data: Input string (unicode).
+        """
+        # Handle bracketed paste. (We bypass the parser that matches all other
+        # key presses and keep reading input until we see the end mark.)
+        # This is much faster then parsing character by character.
+        if self._in_bracketed_paste:
+            self._paste_buffer += data
+            end_mark = "\x1b[201~"
+
+            if end_mark in self._paste_buffer:
+                end_index = self._paste_buffer.index(end_mark)
+
+                # Feed content to key bindings.
+                paste_content = self._paste_buffer[:end_index]
+                self.feed_key_callback(KeyPress(Keys.BracketedPaste, paste_content))
+
+                # Quit bracketed paste mode and handle remaining input.
+                self._in_bracketed_paste = False
+                remaining = self._paste_buffer[end_index + len(end_mark) :]
+                self._paste_buffer = ""
+
+                self.feed(remaining)
+
+        # Handle normal input character by character.
+        else:
+            for i, c in enumerate(data):
+                if self._in_bracketed_paste:
+                    # Quit loop and process from this position when the parser
+                    # entered bracketed paste.
+                    self.feed(data[i:])
+                    break
+                else:
+                    self._input_parser.send(c)
+
+    def flush(self) -> None:
+        """
+        Flush the buffer of the input stream.
+
+        This will allow us to handle the escape key (or maybe meta) sooner.
+        The input received by the escape key is actually the same as the first
+        characters of e.g. Arrow-Up, so without knowing what follows the escape
+        sequence, we don't know whether escape has been pressed, or whether
+        it's something else. This flush function should be called after a
+        timeout, and processes everything that's still in the buffer as-is, so
+        without assuming any characters will follow.
+        """
+        self._input_parser.send(_Flush())
+
+    def feed_and_flush(self, data: str) -> None:
+        """
+        Wrapper around ``feed`` and ``flush``.
+        """
+        self.feed(data)
+        self.flush()
diff --git a/src/prompt_toolkit/input/win32.py b/src/prompt_toolkit/input/win32.py
new file mode 100644
index 0000000..db3fa2b
--- /dev/null
+++ b/src/prompt_toolkit/input/win32.py
@@ -0,0 +1,757 @@
+import os
+import sys
+from abc import abstractmethod
+from contextlib import contextmanager
+
+from prompt_toolkit.eventloop import get_event_loop
+
+from ..utils import SPHINX_AUTODOC_RUNNING
+
+assert sys.platform == "win32"
+
+# Do not import win32-specific stuff when generating documentation.
+# Otherwise RTD would be unable to generate docs for this module.
+if not SPHINX_AUTODOC_RUNNING:
+    import msvcrt
+    from ctypes import windll
+
+from ctypes import Array, pointer
+from ctypes.wintypes import DWORD, HANDLE
+from typing import (
+    Callable,
+    ContextManager,
+    Dict,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    TextIO,
+)
+
+from prompt_toolkit.eventloop import run_in_executor_with_context
+from prompt_toolkit.eventloop.win32 import create_win32_event, wait_for_handles
+from prompt_toolkit.key_binding.key_processor import KeyPress
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.mouse_events import MouseButton, MouseEventType
+from prompt_toolkit.win32_types import (
+    INPUT_RECORD,
+    KEY_EVENT_RECORD,
+    MOUSE_EVENT_RECORD,
+    STD_INPUT_HANDLE,
+    EventTypes,
+)
+
+from .ansi_escape_sequences import REVERSE_ANSI_SEQUENCES
+from .base import Input
+
+__all__ = [
+    "Win32Input",
+    "ConsoleInputReader",
+    "raw_mode",
+    "cooked_mode",
+    "attach_win32_input",
+    "detach_win32_input",
+]
+
+# Win32 Constants for MOUSE_EVENT_RECORD.
+# See: https://docs.microsoft.com/en-us/windows/console/mouse-event-record-str
+FROM_LEFT_1ST_BUTTON_PRESSED = 0x1
+RIGHTMOST_BUTTON_PRESSED = 0x2
+MOUSE_MOVED = 0x0001
+MOUSE_WHEELED = 0x0004
+
+
+class _Win32InputBase(Input):
+    """
+    Base class for `Win32Input` and `Win32PipeInput`.
+    """
+
+    def __init__(self) -> None:
+        self.win32_handles = _Win32Handles()
+
+    @property
+    @abstractmethod
+    def handle(self) -> HANDLE:
+        pass
+
+
+class Win32Input(_Win32InputBase):
+    """
+    `Input` class that reads from the Windows console.
+    """
+
+    def __init__(self, stdin: Optional[TextIO] = None) -> None:
+        super().__init__()
+        self.console_input_reader = ConsoleInputReader()
+
+    def attach(self, input_ready_callback: Callable[[], None]) -> ContextManager[None]:
+        """
+        Return a context manager that makes this input active in the current
+        event loop.
+        """
+        return attach_win32_input(self, input_ready_callback)
+
+    def detach(self) -> ContextManager[None]:
+        """
+        Return a context manager that makes sure that this input is not active
+        in the current event loop.
+        """
+        return detach_win32_input(self)
+
+    def read_keys(self) -> List[KeyPress]:
+        return list(self.console_input_reader.read())
+
+    def flush(self) -> None:
+        pass
+
+    @property
+    def closed(self) -> bool:
+        return False
+
+    def raw_mode(self) -> ContextManager[None]:
+        return raw_mode()
+
+    def cooked_mode(self) -> ContextManager[None]:
+        return cooked_mode()
+
+    def fileno(self) -> int:
+        # The windows console doesn't depend on the file handle, so
+        # this is not used for the event loop (which uses the
+        # handle instead). But it's used in `Application.run_system_command`
+        # which opens a subprocess with a given stdin/stdout.
+        return sys.stdin.fileno()
+
+    def typeahead_hash(self) -> str:
+        return "win32-input"
+
+    def close(self) -> None:
+        self.console_input_reader.close()
+
+    @property
+    def handle(self) -> HANDLE:
+        return self.console_input_reader.handle
+
+
+class ConsoleInputReader:
+    """
+    :param recognize_paste: When True, try to discover paste actions and turn
+        the event into a BracketedPaste.
+    """
+
+    # Keys with character data.
+    mappings = {
+        b"\x1b": Keys.Escape,
+        b"\x00": Keys.ControlSpace,  # Control-Space (Also for Ctrl-@)
+        b"\x01": Keys.ControlA,  # Control-A (home)
+        b"\x02": Keys.ControlB,  # Control-B (emacs cursor left)
+        b"\x03": Keys.ControlC,  # Control-C (interrupt)
+        b"\x04": Keys.ControlD,  # Control-D (exit)
+        b"\x05": Keys.ControlE,  # Control-E (end)
+        b"\x06": Keys.ControlF,  # Control-F (cursor forward)
+        b"\x07": Keys.ControlG,  # Control-G
+        b"\x08": Keys.ControlH,  # Control-H (8) (Identical to '\b')
+        b"\x09": Keys.ControlI,  # Control-I (9) (Identical to '\t')
+        b"\x0a": Keys.ControlJ,  # Control-J (10) (Identical to '\n')
+        b"\x0b": Keys.ControlK,  # Control-K (delete until end of line; vertical tab)
+        b"\x0c": Keys.ControlL,  # Control-L (clear; form feed)
+        b"\x0d": Keys.ControlM,  # Control-M (enter)
+        b"\x0e": Keys.ControlN,  # Control-N (14) (history forward)
+        b"\x0f": Keys.ControlO,  # Control-O (15)
+        b"\x10": Keys.ControlP,  # Control-P (16) (history back)
+        b"\x11": Keys.ControlQ,  # Control-Q
+        b"\x12": Keys.ControlR,  # Control-R (18) (reverse search)
+        b"\x13": Keys.ControlS,  # Control-S (19) (forward search)
+        b"\x14": Keys.ControlT,  # Control-T
+        b"\x15": Keys.ControlU,  # Control-U
+        b"\x16": Keys.ControlV,  # Control-V
+        b"\x17": Keys.ControlW,  # Control-W
+        b"\x18": Keys.ControlX,  # Control-X
+        b"\x19": Keys.ControlY,  # Control-Y (25)
+        b"\x1a": Keys.ControlZ,  # Control-Z
+        b"\x1c": Keys.ControlBackslash,  # Both Control-\ and Ctrl-|
+        b"\x1d": Keys.ControlSquareClose,  # Control-]
+        b"\x1e": Keys.ControlCircumflex,  # Control-^
+        b"\x1f": Keys.ControlUnderscore,  # Control-underscore (Also for Ctrl-hyphen.)
+        b"\x7f": Keys.Backspace,  # (127) Backspace   (ASCII Delete.)
+    }
+
+    # Keys that don't carry character data.
+    keycodes = {
+        # Home/End
+        33: Keys.PageUp,
+        34: Keys.PageDown,
+        35: Keys.End,
+        36: Keys.Home,
+        # Arrows
+        37: Keys.Left,
+        38: Keys.Up,
+        39: Keys.Right,
+        40: Keys.Down,
+        45: Keys.Insert,
+        46: Keys.Delete,
+        # F-keys.
+        112: Keys.F1,
+        113: Keys.F2,
+        114: Keys.F3,
+        115: Keys.F4,
+        116: Keys.F5,
+        117: Keys.F6,
+        118: Keys.F7,
+        119: Keys.F8,
+        120: Keys.F9,
+        121: Keys.F10,
+        122: Keys.F11,
+        123: Keys.F12,
+    }
+
+    LEFT_ALT_PRESSED = 0x0002
+    RIGHT_ALT_PRESSED = 0x0001
+    SHIFT_PRESSED = 0x0010
+    LEFT_CTRL_PRESSED = 0x0008
+    RIGHT_CTRL_PRESSED = 0x0004
+
+    def __init__(self, recognize_paste: bool = True) -> None:
+        self._fdcon = None
+        self.recognize_paste = recognize_paste
+
+        # When stdin is a tty, use that handle, otherwise, create a handle from
+        # CONIN$.
+        self.handle: HANDLE
+        if sys.stdin.isatty():
+            self.handle = HANDLE(windll.kernel32.GetStdHandle(STD_INPUT_HANDLE))
+        else:
+            self._fdcon = os.open("CONIN$", os.O_RDWR | os.O_BINARY)
+            self.handle = HANDLE(msvcrt.get_osfhandle(self._fdcon))
+
+    def close(self) -> None:
+        "Close fdcon."
+        if self._fdcon is not None:
+            os.close(self._fdcon)
+
+    def read(self) -> Iterable[KeyPress]:
+        """
+        Return a list of `KeyPress` instances. It won't return anything when
+        there was nothing to read.  (This function doesn't block.)
+
+        http://msdn.microsoft.com/en-us/library/windows/desktop/ms684961(v=vs.85).aspx
+        """
+        max_count = 2048  # Max events to read at the same time.
+
+        read = DWORD(0)
+        arrtype = INPUT_RECORD * max_count
+        input_records = arrtype()
+
+        # Check whether there is some input to read. `ReadConsoleInputW` would
+        # block otherwise.
+        # (Actually, the event loop is responsible to make sure that this
+        # function is only called when there is something to read, but for some
+        # reason this happened in the asyncio_win32 loop, and it's better to be
+        # safe anyway.)
+        if not wait_for_handles([self.handle], timeout=0):
+            return
+
+        # Get next batch of input event.
+        windll.kernel32.ReadConsoleInputW(
+            self.handle, pointer(input_records), max_count, pointer(read)
+        )
+
+        # First, get all the keys from the input buffer, in order to determine
+        # whether we should consider this a paste event or not.
+        all_keys = list(self._get_keys(read, input_records))
+
+        # Fill in 'data' for key presses.
+        all_keys = [self._insert_key_data(key) for key in all_keys]
+
+        # Correct non-bmp characters that are passed as separate surrogate codes
+        all_keys = list(self._merge_paired_surrogates(all_keys))
+
+        if self.recognize_paste and self._is_paste(all_keys):
+            gen = iter(all_keys)
+            k: Optional[KeyPress]
+
+            for k in gen:
+                # Pasting: if the current key consists of text or \n, turn it
+                # into a BracketedPaste.
+                data = []
+                while k and (
+                    not isinstance(k.key, Keys)
+                    or k.key in {Keys.ControlJ, Keys.ControlM}
+                ):
+                    data.append(k.data)
+                    try:
+                        k = next(gen)
+                    except StopIteration:
+                        k = None
+
+                if data:
+                    yield KeyPress(Keys.BracketedPaste, "".join(data))
+                if k is not None:
+                    yield k
+        else:
+            yield from all_keys
+
+    def _insert_key_data(self, key_press: KeyPress) -> KeyPress:
+        """
+        Insert KeyPress data, for vt100 compatibility.
+        """
+        if key_press.data:
+            return key_press
+
+        if isinstance(key_press.key, Keys):
+            data = REVERSE_ANSI_SEQUENCES.get(key_press.key, "")
+        else:
+            data = ""
+
+        return KeyPress(key_press.key, data)
+
+    def _get_keys(
+        self, read: DWORD, input_records: "Array[INPUT_RECORD]"
+    ) -> Iterator[KeyPress]:
+        """
+        Generator that yields `KeyPress` objects from the input records.
+        """
+        for i in range(read.value):
+            ir = input_records[i]
+
+            # Get the right EventType from the EVENT_RECORD.
+            # (For some reason the Windows console application 'cmder'
+            # [http://gooseberrycreative.com/cmder/] can return '0' for
+            # ir.EventType. -- Just ignore that.)
+            if ir.EventType in EventTypes:
+                ev = getattr(ir.Event, EventTypes[ir.EventType])
+
+                # Process if this is a key event. (We also have mouse, menu and
+                # focus events.)
+                if type(ev) == KEY_EVENT_RECORD and ev.KeyDown:
+                    yield from self._event_to_key_presses(ev)
+
+                elif type(ev) == MOUSE_EVENT_RECORD:
+                    yield from self._handle_mouse(ev)
+
+    @staticmethod
+    def _merge_paired_surrogates(key_presses: List[KeyPress]) -> Iterator[KeyPress]:
+        """
+        Combines consecutive KeyPresses with high and low surrogates into
+        single characters
+        """
+        buffered_high_surrogate = None
+        for key in key_presses:
+            is_text = not isinstance(key.key, Keys)
+            is_high_surrogate = is_text and "\uD800" <= key.key <= "\uDBFF"
+            is_low_surrogate = is_text and "\uDC00" <= key.key <= "\uDFFF"
+
+            if buffered_high_surrogate:
+                if is_low_surrogate:
+                    # convert high surrogate + low surrogate to single character
+                    fullchar = (
+                        (buffered_high_surrogate.key + key.key)
+                        .encode("utf-16-le", "surrogatepass")
+                        .decode("utf-16-le")
+                    )
+                    key = KeyPress(fullchar, fullchar)
+                else:
+                    yield buffered_high_surrogate
+                buffered_high_surrogate = None
+
+            if is_high_surrogate:
+                buffered_high_surrogate = key
+            else:
+                yield key
+
+        if buffered_high_surrogate:
+            yield buffered_high_surrogate
+
+    @staticmethod
+    def _is_paste(keys: List[KeyPress]) -> bool:
+        """
+        Return `True` when we should consider this list of keys as a paste
+        event. Pasted text on windows will be turned into a
+        `Keys.BracketedPaste` event. (It's not 100% correct, but it is probably
+        the best possible way to detect pasting of text and handle that
+        correctly.)
+        """
+        # Consider paste when it contains at least one newline and at least one
+        # other character.
+        text_count = 0
+        newline_count = 0
+
+        for k in keys:
+            if not isinstance(k.key, Keys):
+                text_count += 1
+            if k.key == Keys.ControlM:
+                newline_count += 1
+
+        return newline_count >= 1 and text_count >= 1
+
+    def _event_to_key_presses(self, ev: KEY_EVENT_RECORD) -> List[KeyPress]:
+        """
+        For this `KEY_EVENT_RECORD`, return a list of `KeyPress` instances.
+        """
+        assert type(ev) == KEY_EVENT_RECORD and ev.KeyDown
+
+        result: Optional[KeyPress] = None
+
+        control_key_state = ev.ControlKeyState
+        u_char = ev.uChar.UnicodeChar
+        # Use surrogatepass because u_char may be an unmatched surrogate
+        ascii_char = u_char.encode("utf-8", "surrogatepass")
+
+        # NOTE: We don't use `ev.uChar.AsciiChar`. That appears to be the
+        # unicode code point truncated to 1 byte. See also:
+        # https://github.com/ipython/ipython/issues/10004
+        # https://github.com/jonathanslenders/python-prompt-toolkit/issues/389
+
+        if u_char == "\x00":
+            if ev.VirtualKeyCode in self.keycodes:
+                result = KeyPress(self.keycodes[ev.VirtualKeyCode], "")
+        else:
+            if ascii_char in self.mappings:
+                if self.mappings[ascii_char] == Keys.ControlJ:
+                    u_char = (
+                        "\n"  # Windows sends \n, turn into \r for unix compatibility.
+                    )
+                result = KeyPress(self.mappings[ascii_char], u_char)
+            else:
+                result = KeyPress(u_char, u_char)
+
+        # First we handle Shift-Control-Arrow/Home/End (need to do this first)
+        if (
+            (
+                control_key_state & self.LEFT_CTRL_PRESSED
+                or control_key_state & self.RIGHT_CTRL_PRESSED
+            )
+            and control_key_state & self.SHIFT_PRESSED
+            and result
+        ):
+            mapping: Dict[str, str] = {
+                Keys.Left: Keys.ControlShiftLeft,
+                Keys.Right: Keys.ControlShiftRight,
+                Keys.Up: Keys.ControlShiftUp,
+                Keys.Down: Keys.ControlShiftDown,
+                Keys.Home: Keys.ControlShiftHome,
+                Keys.End: Keys.ControlShiftEnd,
+                Keys.Insert: Keys.ControlShiftInsert,
+                Keys.PageUp: Keys.ControlShiftPageUp,
+                Keys.PageDown: Keys.ControlShiftPageDown,
+            }
+            result.key = mapping.get(result.key, result.key)
+
+        # Correctly handle Control-Arrow/Home/End and Control-Insert/Delete keys.
+        if (
+            control_key_state & self.LEFT_CTRL_PRESSED
+            or control_key_state & self.RIGHT_CTRL_PRESSED
+        ) and result:
+            mapping = {
+                Keys.Left: Keys.ControlLeft,
+                Keys.Right: Keys.ControlRight,
+                Keys.Up: Keys.ControlUp,
+                Keys.Down: Keys.ControlDown,
+                Keys.Home: Keys.ControlHome,
+                Keys.End: Keys.ControlEnd,
+                Keys.Insert: Keys.ControlInsert,
+                Keys.Delete: Keys.ControlDelete,
+                Keys.PageUp: Keys.ControlPageUp,
+                Keys.PageDown: Keys.ControlPageDown,
+            }
+            result.key = mapping.get(result.key, result.key)
+
+        # Turn 'Tab' into 'BackTab' when shift was pressed.
+        # Also handle other shift-key combination
+        if control_key_state & self.SHIFT_PRESSED and result:
+            mapping = {
+                Keys.Tab: Keys.BackTab,
+                Keys.Left: Keys.ShiftLeft,
+                Keys.Right: Keys.ShiftRight,
+                Keys.Up: Keys.ShiftUp,
+                Keys.Down: Keys.ShiftDown,
+                Keys.Home: Keys.ShiftHome,
+                Keys.End: Keys.ShiftEnd,
+                Keys.Insert: Keys.ShiftInsert,
+                Keys.Delete: Keys.ShiftDelete,
+                Keys.PageUp: Keys.ShiftPageUp,
+                Keys.PageDown: Keys.ShiftPageDown,
+            }
+            result.key = mapping.get(result.key, result.key)
+
+        # Turn 'Space' into 'ControlSpace' when control was pressed.
+        if (
+            (
+                control_key_state & self.LEFT_CTRL_PRESSED
+                or control_key_state & self.RIGHT_CTRL_PRESSED
+            )
+            and result
+            and result.data == " "
+        ):
+            result = KeyPress(Keys.ControlSpace, " ")
+
+        # Turn Control-Enter into META-Enter. (On a vt100 terminal, we cannot
+        # detect this combination. But it's really practical on Windows.)
+        if (
+            (
+                control_key_state & self.LEFT_CTRL_PRESSED
+                or control_key_state & self.RIGHT_CTRL_PRESSED
+            )
+            and result
+            and result.key == Keys.ControlJ
+        ):
+            return [KeyPress(Keys.Escape, ""), result]
+
+        # Return result. If alt was pressed, prefix the result with an
+        # 'Escape' key, just like unix VT100 terminals do.
+
+        # NOTE: Only replace the left alt with escape. The right alt key often
+        #       acts as altgr and is used in many non US keyboard layouts for
+        #       typing some special characters, like a backslash. We don't want
+        #       all backslashes to be prefixed with escape. (Esc-\ has a
+        #       meaning in E-macs, for instance.)
+        if result:
+            meta_pressed = control_key_state & self.LEFT_ALT_PRESSED
+
+            if meta_pressed:
+                return [KeyPress(Keys.Escape, ""), result]
+            else:
+                return [result]
+
+        else:
+            return []
+
+    def _handle_mouse(self, ev: MOUSE_EVENT_RECORD) -> List[KeyPress]:
+        """
+        Handle mouse events. Return a list of KeyPress instances.
+        """
+        event_flags = ev.EventFlags
+        button_state = ev.ButtonState
+
+        event_type: Optional[MouseEventType] = None
+        button: MouseButton = MouseButton.NONE
+
+        # Scroll events.
+        if event_flags & MOUSE_WHEELED:
+            if button_state > 0:
+                event_type = MouseEventType.SCROLL_UP
+            else:
+                event_type = MouseEventType.SCROLL_DOWN
+        else:
+            # Handle button state for non-scroll events.
+            if button_state == FROM_LEFT_1ST_BUTTON_PRESSED:
+                button = MouseButton.LEFT
+
+            elif button_state == RIGHTMOST_BUTTON_PRESSED:
+                button = MouseButton.RIGHT
+
+        # Move events.
+        if event_flags & MOUSE_MOVED:
+            event_type = MouseEventType.MOUSE_MOVE
+
+        # No key pressed anymore: mouse up.
+        if event_type is None:
+            if button_state > 0:
+                # Some button pressed.
+                event_type = MouseEventType.MOUSE_DOWN
+            else:
+                # No button pressed.
+                event_type = MouseEventType.MOUSE_UP
+
+        data = ";".join(
+            [
+                button.value,
+                event_type.value,
+                str(ev.MousePosition.X),
+                str(ev.MousePosition.Y),
+            ]
+        )
+        return [KeyPress(Keys.WindowsMouseEvent, data)]
+
+
+class _Win32Handles:
+    """
+    Utility to keep track of which handles are connectod to which callbacks.
+
+    `add_win32_handle` starts a tiny event loop in another thread which waits
+    for the Win32 handle to become ready. When this happens, the callback will
+    be called in the current asyncio event loop using `call_soon_threadsafe`.
+
+    `remove_win32_handle` will stop this tiny event loop.
+
+    NOTE: We use this technique, so that we don't have to use the
+          `ProactorEventLoop` on Windows and we can wait for things like stdin
+          in a `SelectorEventLoop`. This is important, because our inputhook
+          mechanism (used by IPython), only works with the `SelectorEventLoop`.
+    """
+
+    def __init__(self) -> None:
+        self._handle_callbacks: Dict[int, Callable[[], None]] = {}
+
+        # Windows Events that are triggered when we have to stop watching this
+        # handle.
+        self._remove_events: Dict[int, HANDLE] = {}
+
+    def add_win32_handle(self, handle: HANDLE, callback: Callable[[], None]) -> None:
+        """
+        Add a Win32 handle to the event loop.
+        """
+        handle_value = handle.value
+
+        if handle_value is None:
+            raise ValueError("Invalid handle.")
+
+        # Make sure to remove a previous registered handler first.
+        self.remove_win32_handle(handle)
+
+        loop = get_event_loop()
+        self._handle_callbacks[handle_value] = callback
+
+        # Create remove event.
+        remove_event = create_win32_event()
+        self._remove_events[handle_value] = remove_event
+
+        # Add reader.
+        def ready() -> None:
+            # Tell the callback that input's ready.
+            try:
+                callback()
+            finally:
+                run_in_executor_with_context(wait, loop=loop)
+
+        # Wait for the input to become ready.
+        # (Use an executor for this, the Windows asyncio event loop doesn't
+        # allow us to wait for handles like stdin.)
+        def wait() -> None:
+            # Wait until either the handle becomes ready, or the remove event
+            # has been set.
+            result = wait_for_handles([remove_event, handle])
+
+            if result is remove_event:
+                windll.kernel32.CloseHandle(remove_event)
+                return
+            else:
+                loop.call_soon_threadsafe(ready)
+
+        run_in_executor_with_context(wait, loop=loop)
+
+    def remove_win32_handle(self, handle: HANDLE) -> Optional[Callable[[], None]]:
+        """
+        Remove a Win32 handle from the event loop.
+        Return either the registered handler or `None`.
+        """
+        if handle.value is None:
+            return None  # Ignore.
+
+        # Trigger remove events, so that the reader knows to stop.
+        try:
+            event = self._remove_events.pop(handle.value)
+        except KeyError:
+            pass
+        else:
+            windll.kernel32.SetEvent(event)
+
+        try:
+            return self._handle_callbacks.pop(handle.value)
+        except KeyError:
+            return None
+
+
+@contextmanager
+def attach_win32_input(
+    input: _Win32InputBase, callback: Callable[[], None]
+) -> Iterator[None]:
+    """
+    Context manager that makes this input active in the current event loop.
+
+    :param input: :class:`~prompt_toolkit.input.Input` object.
+    :param input_ready_callback: Called when the input is ready to read.
+    """
+    win32_handles = input.win32_handles
+    handle = input.handle
+
+    if handle.value is None:
+        raise ValueError("Invalid handle.")
+
+    # Add reader.
+    previous_callback = win32_handles.remove_win32_handle(handle)
+    win32_handles.add_win32_handle(handle, callback)
+
+    try:
+        yield
+    finally:
+        win32_handles.remove_win32_handle(handle)
+
+        if previous_callback:
+            win32_handles.add_win32_handle(handle, previous_callback)
+
+
+@contextmanager
+def detach_win32_input(input: _Win32InputBase) -> Iterator[None]:
+    win32_handles = input.win32_handles
+    handle = input.handle
+
+    if handle.value is None:
+        raise ValueError("Invalid handle.")
+
+    previous_callback = win32_handles.remove_win32_handle(handle)
+
+    try:
+        yield
+    finally:
+        if previous_callback:
+            win32_handles.add_win32_handle(handle, previous_callback)
+
+
+class raw_mode:
+    """
+    ::
+
+        with raw_mode(stdin):
+            ''' the windows terminal is now in 'raw' mode. '''
+
+    The ``fileno`` attribute is ignored. This is to be compatible with the
+    `raw_input` method of `.vt100_input`.
+    """
+
+    def __init__(self, fileno: Optional[int] = None) -> None:
+        self.handle = HANDLE(windll.kernel32.GetStdHandle(STD_INPUT_HANDLE))
+
+    def __enter__(self) -> None:
+        # Remember original mode.
+        original_mode = DWORD()
+        windll.kernel32.GetConsoleMode(self.handle, pointer(original_mode))
+        self.original_mode = original_mode
+
+        self._patch()
+
+    def _patch(self) -> None:
+        # Set raw
+        ENABLE_ECHO_INPUT = 0x0004
+        ENABLE_LINE_INPUT = 0x0002
+        ENABLE_PROCESSED_INPUT = 0x0001
+
+        windll.kernel32.SetConsoleMode(
+            self.handle,
+            self.original_mode.value
+            & ~(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT),
+        )
+
+    def __exit__(self, *a: object) -> None:
+        # Restore original mode
+        windll.kernel32.SetConsoleMode(self.handle, self.original_mode)
+
+
+class cooked_mode(raw_mode):
+    """
+    ::
+
+        with cooked_mode(stdin):
+            ''' The pseudo-terminal stdin is now used in cooked mode. '''
+    """
+
+    def _patch(self) -> None:
+        # Set cooked.
+        ENABLE_ECHO_INPUT = 0x0004
+        ENABLE_LINE_INPUT = 0x0002
+        ENABLE_PROCESSED_INPUT = 0x0001
+
+        windll.kernel32.SetConsoleMode(
+            self.handle,
+            self.original_mode.value
+            | (ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT),
+        )
diff --git a/src/prompt_toolkit/input/win32_pipe.py b/src/prompt_toolkit/input/win32_pipe.py
new file mode 100644
index 0000000..ebee207
--- /dev/null
+++ b/src/prompt_toolkit/input/win32_pipe.py
@@ -0,0 +1,154 @@
+import sys
+
+assert sys.platform == "win32"
+
+from contextlib import contextmanager
+from ctypes import windll
+from ctypes.wintypes import HANDLE
+from typing import Callable, ContextManager, Iterator, List
+
+from prompt_toolkit.eventloop.win32 import create_win32_event
+
+from ..key_binding import KeyPress
+from ..utils import DummyContext
+from .base import PipeInput
+from .vt100_parser import Vt100Parser
+from .win32 import _Win32InputBase, attach_win32_input, detach_win32_input
+
+__all__ = ["Win32PipeInput"]
+
+
+class Win32PipeInput(_Win32InputBase, PipeInput):
+    """
+    This is an input pipe that works on Windows.
+    Text or bytes can be feed into the pipe, and key strokes can be read from
+    the pipe. This is useful if we want to send the input programmatically into
+    the application. Mostly useful for unit testing.
+
+    Notice that even though it's Windows, we use vt100 escape sequences over
+    the pipe.
+
+    Usage::
+
+        input = Win32PipeInput()
+        input.send_text('inputdata')
+    """
+
+    _id = 0
+
+    def __init__(self, _event: HANDLE) -> None:
+        super().__init__()
+        # Event (handle) for registering this input in the event loop.
+        # This event is set when there is data available to read from the pipe.
+        # Note: We use this approach instead of using a regular pipe, like
+        #       returned from `os.pipe()`, because making such a regular pipe
+        #       non-blocking is tricky and this works really well.
+        self._event = create_win32_event()
+
+        self._closed = False
+
+        # Parser for incoming keys.
+        self._buffer: List[KeyPress] = []  # Buffer to collect the Key objects.
+        self.vt100_parser = Vt100Parser(lambda key: self._buffer.append(key))
+
+        # Identifier for every PipeInput for the hash.
+        self.__class__._id += 1
+        self._id = self.__class__._id
+
+    @classmethod
+    @contextmanager
+    def create(cls) -> Iterator["Win32PipeInput"]:
+        event = create_win32_event()
+        try:
+            yield Win32PipeInput(_event=event)
+        finally:
+            windll.kernel32.CloseHandle(event)
+
+    @property
+    def closed(self) -> bool:
+        return self._closed
+
+    def fileno(self) -> int:
+        """
+        The windows pipe doesn't depend on the file handle.
+        """
+        raise NotImplementedError
+
+    @property
+    def handle(self) -> HANDLE:
+        "The handle used for registering this pipe in the event loop."
+        return self._event
+
+    def attach(self, input_ready_callback: Callable[[], None]) -> ContextManager[None]:
+        """
+        Return a context manager that makes this input active in the current
+        event loop.
+        """
+        return attach_win32_input(self, input_ready_callback)
+
+    def detach(self) -> ContextManager[None]:
+        """
+        Return a context manager that makes sure that this input is not active
+        in the current event loop.
+        """
+        return detach_win32_input(self)
+
+    def read_keys(self) -> List[KeyPress]:
+        "Read list of KeyPress."
+
+        # Return result.
+        result = self._buffer
+        self._buffer = []
+
+        # Reset event.
+        if not self._closed:
+            # (If closed, the event should not reset.)
+            windll.kernel32.ResetEvent(self._event)
+
+        return result
+
+    def flush_keys(self) -> List[KeyPress]:
+        """
+        Flush pending keys and return them.
+        (Used for flushing the 'escape' key.)
+        """
+        # Flush all pending keys. (This is most important to flush the vt100
+        # 'Escape' key early when nothing else follows.)
+        self.vt100_parser.flush()
+
+        # Return result.
+        result = self._buffer
+        self._buffer = []
+        return result
+
+    def send_bytes(self, data: bytes) -> None:
+        "Send bytes to the input."
+        self.send_text(data.decode("utf-8", "ignore"))
+
+    def send_text(self, text: str) -> None:
+        "Send text to the input."
+        if self._closed:
+            raise ValueError("Attempt to write into a closed pipe.")
+
+        # Pass it through our vt100 parser.
+        self.vt100_parser.feed(text)
+
+        # Set event.
+        windll.kernel32.SetEvent(self._event)
+
+    def raw_mode(self) -> ContextManager[None]:
+        return DummyContext()
+
+    def cooked_mode(self) -> ContextManager[None]:
+        return DummyContext()
+
+    def close(self) -> None:
+        "Close write-end of the pipe."
+        self._closed = True
+        windll.kernel32.SetEvent(self._event)
+
+    def typeahead_hash(self) -> str:
+        """
+        This needs to be unique for every `PipeInput`.
+        """
+        return f"pipe-input-{self._id}"
diff --git a/src/prompt_toolkit/key_binding/__init__.py b/src/prompt_toolkit/key_binding/__init__.py
new file mode 100644
index 0000000..be10536
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/__init__.py
@@ -0,0 +1,20 @@
+from .key_bindings import (
+    ConditionalKeyBindings,
+    DynamicKeyBindings,
+    KeyBindings,
+    KeyBindingsBase,
+    merge_key_bindings,
+)
+from .key_processor import KeyPress, KeyPressEvent
+
+__all__ = [
+    # key_bindings.
+    "ConditionalKeyBindings",
+    "DynamicKeyBindings",
+    "KeyBindings",
+    "KeyBindingsBase",
+    "merge_key_bindings",
+    # key_processor
+    "KeyPress",
+    "KeyPressEvent",
+]
diff --git a/src/prompt_toolkit/key_binding/bindings/__init__.py b/src/prompt_toolkit/key_binding/bindings/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/__init__.py
diff --git a/src/prompt_toolkit/key_binding/bindings/auto_suggest.py b/src/prompt_toolkit/key_binding/bindings/auto_suggest.py
new file mode 100644
index 0000000..c016c06
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/auto_suggest.py
@@ -0,0 +1,63 @@
+"""
+Key bindings for auto suggestion (for fish-style auto suggestion).
+"""
+import re
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.filters import Condition, emacs_mode
+from prompt_toolkit.key_binding.key_bindings import KeyBindings
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+
+__all__ = [
+    "load_auto_suggest_bindings",
+]
+
+E = KeyPressEvent
+
+
+def load_auto_suggest_bindings() -> KeyBindings:
+    """
+    Key bindings for accepting auto suggestion text.
+
+    (This has to come after the Vi bindings, because they also have an
+    implementation for the "right arrow", but we really want the suggestion
+    binding when a suggestion is available.)
+    """
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+
+    @Condition
+    def suggestion_available() -> bool:
+        app = get_app()
+        return (
+            app.current_buffer.suggestion is not None
+            and len(app.current_buffer.suggestion.text) > 0
+            and app.current_buffer.document.is_cursor_at_the_end
+        )
+
+    @handle("c-f", filter=suggestion_available)
+    @handle("c-e", filter=suggestion_available)
+    @handle("right", filter=suggestion_available)
+    def _accept(event: E) -> None:
+        """
+        Accept suggestion.
+        """
+        b = event.current_buffer
+        suggestion = b.suggestion
+
+        if suggestion:
+            b.insert_text(suggestion.text)
+
+    @handle("escape", "f", filter=suggestion_available & emacs_mode)
+    def _fill(event: E) -> None:
+        """
+        Fill partial suggestion.
+        """
+        b = event.current_buffer
+        suggestion = b.suggestion
+
+        if suggestion:
+            t = re.split(r"(\S+\s+)", suggestion.text)
+            b.insert_text(next(x for x in t if x))
+
+    return key_bindings
diff --git a/src/prompt_toolkit/key_binding/bindings/basic.py b/src/prompt_toolkit/key_binding/bindings/basic.py
new file mode 100644
index 0000000..fc8f964
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/basic.py
@@ -0,0 +1,253 @@
+# pylint: disable=function-redefined
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.filters import (
+    Condition,
+    emacs_insert_mode,
+    has_selection,
+    in_paste_mode,
+    is_multiline,
+    vi_insert_mode,
+)
+from prompt_toolkit.key_binding.key_processor import KeyPress, KeyPressEvent
+from prompt_toolkit.keys import Keys
+
+from ..key_bindings import KeyBindings
+from .named_commands import get_by_name
+
+__all__ = [
+    "load_basic_bindings",
+]
+
+E = KeyPressEvent
+
+
+def if_no_repeat(event: E) -> bool:
+    """Callable that returns True when the previous event was delivered to
+    another handler."""
+    return not event.is_repeat
+
+
+def load_basic_bindings() -> KeyBindings:
+    key_bindings = KeyBindings()
+    insert_mode = vi_insert_mode | emacs_insert_mode
+    handle = key_bindings.add
+
+    @handle("c-a")
+    @handle("c-b")
+    @handle("c-c")
+    @handle("c-d")
+    @handle("c-e")
+    @handle("c-f")
+    @handle("c-g")
+    @handle("c-h")
+    @handle("c-i")
+    @handle("c-j")
+    @handle("c-k")
+    @handle("c-l")
+    @handle("c-m")
+    @handle("c-n")
+    @handle("c-o")
+    @handle("c-p")
+    @handle("c-q")
+    @handle("c-r")
+    @handle("c-s")
+    @handle("c-t")
+    @handle("c-u")
+    @handle("c-v")
+    @handle("c-w")
+    @handle("c-x")
+    @handle("c-y")
+    @handle("c-z")
+    @handle("f1")
+    @handle("f2")
+    @handle("f3")
+    @handle("f4")
+    @handle("f5")
+    @handle("f6")
+    @handle("f7")
+    @handle("f8")
+    @handle("f9")
+    @handle("f10")
+    @handle("f11")
+    @handle("f12")
+    @handle("f13")
+    @handle("f14")
+    @handle("f15")
+    @handle("f16")
+    @handle("f17")
+    @handle("f18")
+    @handle("f19")
+    @handle("f20")
+    @handle("f21")
+    @handle("f22")
+    @handle("f23")
+    @handle("f24")
+    @handle("c-@")  # Also c-space.
+    @handle("c-\\")
+    @handle("c-]")
+    @handle("c-^")
+    @handle("c-_")
+    @handle("backspace")
+    @handle("up")
+    @handle("down")
+    @handle("right")
+    @handle("left")
+    @handle("s-up")
+    @handle("s-down")
+    @handle("s-right")
+    @handle("s-left")
+    @handle("home")
+    @handle("end")
+    @handle("s-home")
+    @handle("s-end")
+    @handle("delete")
+    @handle("s-delete")
+    @handle("c-delete")
+    @handle("pageup")
+    @handle("pagedown")
+    @handle("s-tab")
+    @handle("tab")
+    @handle("c-s-left")
+    @handle("c-s-right")
+    @handle("c-s-home")
+    @handle("c-s-end")
+    @handle("c-left")
+    @handle("c-right")
+    @handle("c-up")
+    @handle("c-down")
+    @handle("c-home")
+    @handle("c-end")
+    @handle("insert")
+    @handle("s-insert")
+    @handle("c-insert")
+    @handle("<sigint>")
+    @handle(Keys.Ignore)
+    def _ignore(event: E) -> None:
+        """
+        First, for any of these keys, Don't do anything by default. Also don't
+        catch them in the 'Any' handler which will insert them as data.
+
+        If people want to insert these characters as a literal, they can always
+        do by doing a quoted insert. (ControlQ in emacs mode, ControlV in Vi
+        mode.)
+        """
+        pass
+
+    # Readline-style bindings.
+    handle("home")(get_by_name("beginning-of-line"))
+    handle("end")(get_by_name("end-of-line"))
+    handle("left")(get_by_name("backward-char"))
+    handle("right")(get_by_name("forward-char"))
+    handle("c-up")(get_by_name("previous-history"))
+    handle("c-down")(get_by_name("next-history"))
+    handle("c-l")(get_by_name("clear-screen"))
+
+    handle("c-k", filter=insert_mode)(get_by_name("kill-line"))
+    handle("c-u", filter=insert_mode)(get_by_name("unix-line-discard"))
+    handle("backspace", filter=insert_mode, save_before=if_no_repeat)(
+        get_by_name("backward-delete-char")
+    )
+    handle("delete", filter=insert_mode, save_before=if_no_repeat)(
+        get_by_name("delete-char")
+    )
+    handle("c-delete", filter=insert_mode, save_before=if_no_repeat)(
+        get_by_name("delete-char")
+    )
+    handle(Keys.Any, filter=insert_mode, save_before=if_no_repeat)(
+        get_by_name("self-insert")
+    )
+    handle("c-t", filter=insert_mode)(get_by_name("transpose-chars"))
+    handle("c-i", filter=insert_mode)(get_by_name("menu-complete"))
+    handle("s-tab", filter=insert_mode)(get_by_name("menu-complete-backward"))
+
+    # Control-W should delete, using whitespace as separator, while M-Del
+    # should delete using [^a-zA-Z0-9] as a boundary.
+    handle("c-w", filter=insert_mode)(get_by_name("unix-word-rubout"))
+
+    handle("pageup", filter=~has_selection)(get_by_name("previous-history"))
+    handle("pagedown", filter=~has_selection)(get_by_name("next-history"))
+
+    # CTRL keys.
+
+    @Condition
+    def has_text_before_cursor() -> bool:
+        return bool(get_app().current_buffer.text)
+
+    handle("c-d", filter=has_text_before_cursor & insert_mode)(
+        get_by_name("delete-char")
+    )
+
+    @handle("enter", filter=insert_mode & is_multiline)
+    def _newline(event: E) -> None:
+        """
+        Newline (in case of multiline input.
+        """
+        event.current_buffer.newline(copy_margin=not in_paste_mode())
+
+    @handle("c-j")
+    def _newline2(event: E) -> None:
+        r"""
+        By default, handle \n as if it were a \r (enter).
+        (It appears that some terminals send \n instead of \r when pressing
+        enter. - at least the Linux subsystem for Windows.)
+        """
+        event.key_processor.feed(KeyPress(Keys.ControlM, "\r"), first=True)
+
+    # Delete the word before the cursor.
+
+    @handle("up")
+    def _go_up(event: E) -> None:
+        event.current_buffer.auto_up(count=event.arg)
+
+    @handle("down")
+    def _go_down(event: E) -> None:
+        event.current_buffer.auto_down(count=event.arg)
+
+    @handle("delete", filter=has_selection)
+    def _cut(event: E) -> None:
+        data = event.current_buffer.cut_selection()
+        event.app.clipboard.set_data(data)
+
+    # Global bindings.
+
+    @handle("c-z")
+    def _insert_ctrl_z(event: E) -> None:
+        """
+        By default, control-Z should literally insert Ctrl-Z.
+        (Ansi Ctrl-Z, code 26 in MSDOS means End-Of-File.
+        In a Python REPL for instance, it's possible to type
+        Control-Z followed by enter to quit.)
+
+        When the system bindings are loaded and suspend-to-background is
+        supported, that will override this binding.
+        """
+        event.current_buffer.insert_text(event.data)
+
+    @handle(Keys.BracketedPaste)
+    def _paste(event: E) -> None:
+        """
+        Pasting from clipboard.
+        """
+        data = event.data
+
+        # Be sure to use \n as line ending.
+        # Some terminals (Like iTerm2) seem to paste \r\n line endings in a
+        # bracketed paste. See: https://github.com/ipython/ipython/issues/9737
+        data = data.replace("\r\n", "\n")
+        data = data.replace("\r", "\n")
+
+        event.current_buffer.insert_text(data)
+
+    @Condition
+    def in_quoted_insert() -> bool:
+        return get_app().quoted_insert
+
+    @handle(Keys.Any, filter=in_quoted_insert, eager=True)
+    def _insert_text(event: E) -> None:
+        """
+        Handle quoted insert.
+        """
+        event.current_buffer.insert_text(event.data, overwrite=False)
+        event.app.quoted_insert = False
+
+    return key_bindings
diff --git a/src/prompt_toolkit/key_binding/bindings/completion.py b/src/prompt_toolkit/key_binding/bindings/completion.py
new file mode 100644
index 0000000..a30b54e
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/completion.py
@@ -0,0 +1,203 @@
+"""
+Key binding handlers for displaying completions.
+"""
+import asyncio
+import math
+from typing import TYPE_CHECKING, List
+
+from prompt_toolkit.application.run_in_terminal import in_terminal
+from prompt_toolkit.completion import (
+    CompleteEvent,
+    Completion,
+    get_common_complete_suffix,
+)
+from prompt_toolkit.formatted_text import StyleAndTextTuples
+from prompt_toolkit.key_binding.key_bindings import KeyBindings
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.utils import get_cwidth
+
+if TYPE_CHECKING:
+    from prompt_toolkit.application import Application
+    from prompt_toolkit.shortcuts import PromptSession
+
+__all__ = [
+    "generate_completions",
+    "display_completions_like_readline",
+]
+
+E = KeyPressEvent
+
+
+def generate_completions(event: E) -> None:
+    r"""
+    Tab-completion: where the first tab completes the common suffix and the
+    second tab lists all the completions.
+    """
+    b = event.current_buffer
+
+    # When already navigating through completions, select the next one.
+    if b.complete_state:
+        b.complete_next()
+    else:
+        b.start_completion(insert_common_part=True)
+
+
+def display_completions_like_readline(event: E) -> None:
+    """
+    Key binding handler for readline-style tab completion.
+    This is meant to be as similar as possible to the way how readline displays
+    completions.
+
+    Generate the completions immediately (blocking) and display them above the
+    prompt in columns.
+
+    Usage::
+
+        # Call this handler when 'Tab' has been pressed.
+        key_bindings.add(Keys.ControlI)(display_completions_like_readline)
+    """
+    # Request completions.
+    b = event.current_buffer
+    if b.completer is None:
+        return
+    complete_event = CompleteEvent(completion_requested=True)
+    completions = list(b.completer.get_completions(b.document, complete_event))
+
+    # Calculate the common suffix.
+    common_suffix = get_common_complete_suffix(b.document, completions)
+
+    # One completion: insert it.
+    if len(completions) == 1:
+        b.delete_before_cursor(-completions[0].start_position)
+        b.insert_text(completions[0].text)
+    # Multiple completions with common part.
+    elif common_suffix:
+        b.insert_text(common_suffix)
+    # Otherwise: display all completions.
+    elif completions:
+        _display_completions_like_readline(event.app, completions)
+
+
+def _display_completions_like_readline(
+    app: "Application[object]", completions: List[Completion]
+) -> "asyncio.Task[None]":
+    """
+    Display the list of completions in columns above the prompt.
+    This will ask for a confirmation if there are too many completions to fit
+    on a single page and provide a paginator to walk through them.
+    """
+    from prompt_toolkit.formatted_text import to_formatted_text
+    from prompt_toolkit.shortcuts.prompt import create_confirm_session
+
+    # Get terminal dimensions.
+    term_size = app.output.get_size()
+    term_width = term_size.columns
+    term_height = term_size.rows
+
+    # Calculate amount of required columns/rows for displaying the
+    # completions. (Keep in mind that completions are displayed
+    # alphabetically column-wise.)
+    max_compl_width = min(
+        term_width, max(get_cwidth(c.display_text) for c in completions) + 1
+    )
+    column_count = max(1, term_width // max_compl_width)
+    completions_per_page = column_count * (term_height - 1)
+    page_count = int(math.ceil(len(completions) / float(completions_per_page)))
+    # Note: math.ceil can return float on Python2.
+
+    def display(page: int) -> None:
+        # Display completions.
+        page_completions = completions[
+            page * completions_per_page : (page + 1) * completions_per_page
+        ]
+
+        page_row_count = int(math.ceil(len(page_completions) / float(column_count)))
+        page_columns = [
+            page_completions[i * page_row_count : (i + 1) * page_row_count]
+            for i in range(column_count)
+        ]
+
+        result: StyleAndTextTuples = []
+
+        for r in range(page_row_count):
+            for c in range(column_count):
+                try:
+                    completion = page_columns[c][r]
+                    style = "class:readline-like-completions.completion " + (
+                        completion.style or ""
+                    )
+
+                    result.extend(to_formatted_text(completion.display, style=style))
+
+                    # Add padding.
+                    padding = max_compl_width - get_cwidth(completion.display_text)
+                    result.append((completion.style, " " * padding))
+                except IndexError:
+                    pass
+            result.append(("", "\n"))
+
+        app.print_text(to_formatted_text(result, "class:readline-like-completions"))
+
+    # User interaction through an application generator function.
+    async def run_compl() -> None:
+        "Coroutine."
+        async with in_terminal(render_cli_done=True):
+            if len(completions) > completions_per_page:
+                # Ask confirmation if it doesn't fit on the screen.
+                confirm = await create_confirm_session(
+                    f"Display all {len(completions)} possibilities?",
+                ).prompt_async()
+
+                if confirm:
+                    # Display pages.
+                    for page in range(page_count):
+                        display(page)
+
+                        if page != page_count - 1:
+                            # Display --MORE-- and go to the next page.
+                            show_more = await _create_more_session(
+                                "--MORE--"
+                            ).prompt_async()
+
+                            if not show_more:
+                                return
+                else:
+                    app.output.flush()
+            else:
+                # Display all completions.
+                display(0)
+
+    return app.create_background_task(run_compl())
+
+
+def _create_more_session(message: str = "--MORE--") -> "PromptSession[bool]":
+    """
+    Create a `PromptSession` object for displaying the "--MORE--".
+    """
+    from prompt_toolkit.shortcuts import PromptSession
+
+    bindings = KeyBindings()
+
+    @bindings.add(" ")
+    @bindings.add("y")
+    @bindings.add("Y")
+    @bindings.add(Keys.ControlJ)
+    @bindings.add(Keys.ControlM)
+    @bindings.add(Keys.ControlI)  # Tab.
+    def _yes(event: E) -> None:
+        event.app.exit(result=True)
+
+    @bindings.add("n")
+    @bindings.add("N")
+    @bindings.add("q")
+    @bindings.add("Q")
+    @bindings.add(Keys.ControlC)
+    def _no(event: E) -> None:
+        event.app.exit(result=False)
+
+    @bindings.add(Keys.Any)
+    def _ignore(event: E) -> None:
+        "Disable inserting of text."
+
+    return PromptSession(message, key_bindings=bindings, erase_when_done=True)
diff --git a/src/prompt_toolkit/key_binding/bindings/cpr.py b/src/prompt_toolkit/key_binding/bindings/cpr.py
new file mode 100644
index 0000000..07b0fa7
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/cpr.py
@@ -0,0 +1,28 @@
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.keys import Keys
+
+from ..key_bindings import KeyBindings
+
+__all__ = [
+    "load_cpr_bindings",
+]
+
+E = KeyPressEvent
+
+
+def load_cpr_bindings() -> KeyBindings:
+    key_bindings = KeyBindings()
+
+    @key_bindings.add(Keys.CPRResponse, save_before=lambda e: False)
+    def _(event: E) -> None:
+        """
+        Handle incoming Cursor-Position-Request response.
+        """
+        # The incoming data looks like u'\x1b[35;1R'
+        # Parse row/col information.
+        row, col = map(int, event.data[2:-1].split(";"))
+
+        # Report absolute cursor position to the renderer.
+        event.app.renderer.report_absolute_cursor_row(row)
+
+    return key_bindings
diff --git a/src/prompt_toolkit/key_binding/bindings/emacs.py b/src/prompt_toolkit/key_binding/bindings/emacs.py
new file mode 100644
index 0000000..a4a5e34
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/emacs.py
@@ -0,0 +1,557 @@
+# pylint: disable=function-redefined
+from typing import Dict, Union
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.buffer import Buffer, indent, unindent
+from prompt_toolkit.completion import CompleteEvent
+from prompt_toolkit.filters import (
+    Condition,
+    emacs_insert_mode,
+    emacs_mode,
+    has_arg,
+    has_selection,
+    in_paste_mode,
+    is_multiline,
+    is_read_only,
+    shift_selection_mode,
+    vi_search_direction_reversed,
+)
+from prompt_toolkit.key_binding.key_bindings import Binding
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.selection import SelectionType
+
+from ..key_bindings import ConditionalKeyBindings, KeyBindings, KeyBindingsBase
+from .named_commands import get_by_name
+
+__all__ = [
+    "load_emacs_bindings",
+    "load_emacs_search_bindings",
+    "load_emacs_shift_selection_bindings",
+]
+
+E = KeyPressEvent
+
+
+def load_emacs_bindings() -> KeyBindingsBase:
+    """
+    Some e-macs extensions.
+    """
+    # Overview of Readline emacs commands:
+    # http://www.catonmat.net/download/readline-emacs-editing-mode-cheat-sheet.pdf
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+
+    insert_mode = emacs_insert_mode
+
+    @handle("escape")
+    def _esc(event: E) -> None:
+        """
+        By default, ignore escape key.
+
+        (If we don't put this here, and Esc is followed by a key which sequence
+        is not handled, we'll insert an Escape character in the input stream.
+        Something we don't want and happens to easily in emacs mode.
+        Further, people can always use ControlQ to do a quoted insert.)
+        """
+        pass
+
+    handle("c-a")(get_by_name("beginning-of-line"))
+    handle("c-b")(get_by_name("backward-char"))
+    handle("c-delete", filter=insert_mode)(get_by_name("kill-word"))
+    handle("c-e")(get_by_name("end-of-line"))
+    handle("c-f")(get_by_name("forward-char"))
+    handle("c-left")(get_by_name("backward-word"))
+    handle("c-right")(get_by_name("forward-word"))
+    handle("c-x", "r", "y", filter=insert_mode)(get_by_name("yank"))
+    handle("c-y", filter=insert_mode)(get_by_name("yank"))
+    handle("escape", "b")(get_by_name("backward-word"))
+    handle("escape", "c", filter=insert_mode)(get_by_name("capitalize-word"))
+    handle("escape", "d", filter=insert_mode)(get_by_name("kill-word"))
+    handle("escape", "f")(get_by_name("forward-word"))
+    handle("escape", "l", filter=insert_mode)(get_by_name("downcase-word"))
+    handle("escape", "u", filter=insert_mode)(get_by_name("uppercase-word"))
+    handle("escape", "y", filter=insert_mode)(get_by_name("yank-pop"))
+    handle("escape", "backspace", filter=insert_mode)(get_by_name("backward-kill-word"))
+    handle("escape", "\\", filter=insert_mode)(get_by_name("delete-horizontal-space"))
+
+    handle("c-home")(get_by_name("beginning-of-buffer"))
+    handle("c-end")(get_by_name("end-of-buffer"))
+
+    handle("c-_", save_before=(lambda e: False), filter=insert_mode)(
+        get_by_name("undo")
+    )
+
+    handle("c-x", "c-u", save_before=(lambda e: False), filter=insert_mode)(
+        get_by_name("undo")
+    )
+
+    handle("escape", "<", filter=~has_selection)(get_by_name("beginning-of-history"))
+    handle("escape", ">", filter=~has_selection)(get_by_name("end-of-history"))
+
+    handle("escape", ".", filter=insert_mode)(get_by_name("yank-last-arg"))
+    handle("escape", "_", filter=insert_mode)(get_by_name("yank-last-arg"))
+    handle("escape", "c-y", filter=insert_mode)(get_by_name("yank-nth-arg"))
+    handle("escape", "#", filter=insert_mode)(get_by_name("insert-comment"))
+    handle("c-o")(get_by_name("operate-and-get-next"))
+
+    # ControlQ does a quoted insert. Not that for vt100 terminals, you have to
+    # disable flow control by running ``stty -ixon``, otherwise Ctrl-Q and
+    # Ctrl-S are captured by the terminal.
+    handle("c-q", filter=~has_selection)(get_by_name("quoted-insert"))
+
+    handle("c-x", "(")(get_by_name("start-kbd-macro"))
+    handle("c-x", ")")(get_by_name("end-kbd-macro"))
+    handle("c-x", "e")(get_by_name("call-last-kbd-macro"))
+
+    @handle("c-n")
+    def _next(event: E) -> None:
+        "Next line."
+        event.current_buffer.auto_down()
+
+    @handle("c-p")
+    def _prev(event: E) -> None:
+        "Previous line."
+        event.current_buffer.auto_up(count=event.arg)
+
+    def handle_digit(c: str) -> None:
+        """
+        Handle input of arguments.
+        The first number needs to be preceded by escape.
+        """
+
+        @handle(c, filter=has_arg)
+        @handle("escape", c)
+        def _(event: E) -> None:
+            event.append_to_arg_count(c)
+
+    for c in "0123456789":
+        handle_digit(c)
+
+    @handle("escape", "-", filter=~has_arg)
+    def _meta_dash(event: E) -> None:
+        """"""
+        if event._arg is None:
+            event.append_to_arg_count("-")
+
+    @handle("-", filter=Condition(lambda: get_app().key_processor.arg == "-"))
+    def _dash(event: E) -> None:
+        """
+        When '-' is typed again, after exactly '-' has been given as an
+        argument, ignore this.
+        """
+        event.app.key_processor.arg = "-"
+
+    @Condition
+    def is_returnable() -> bool:
+        return get_app().current_buffer.is_returnable
+
+    # Meta + Enter: always accept input.
+    handle("escape", "enter", filter=insert_mode & is_returnable)(
+        get_by_name("accept-line")
+    )
+
+    # Enter: accept input in single line mode.
+    handle("enter", filter=insert_mode & is_returnable & ~is_multiline)(
+        get_by_name("accept-line")
+    )
+
+    def character_search(buff: Buffer, char: str, count: int) -> None:
+        if count < 0:
+            match = buff.document.find_backwards(
+                char, in_current_line=True, count=-count
+            )
+        else:
+            match = buff.document.find(char, in_current_line=True, count=count)
+
+        if match is not None:
+            buff.cursor_position += match
+
+    @handle("c-]", Keys.Any)
+    def _goto_char(event: E) -> None:
+        "When Ctl-] + a character is pressed. go to that character."
+        # Also named 'character-search'
+        character_search(event.current_buffer, event.data, event.arg)
+
+    @handle("escape", "c-]", Keys.Any)
+    def _goto_char_backwards(event: E) -> None:
+        "Like Ctl-], but backwards."
+        # Also named 'character-search-backward'
+        character_search(event.current_buffer, event.data, -event.arg)
+
+    @handle("escape", "a")
+    def _prev_sentence(event: E) -> None:
+        "Previous sentence."
+        # TODO:
+
+    @handle("escape", "e")
+    def _end_of_sentence(event: E) -> None:
+        "Move to end of sentence."
+        # TODO:
+
+    @handle("escape", "t", filter=insert_mode)
+    def _swap_characters(event: E) -> None:
+        """
+        Swap the last two words before the cursor.
+        """
+        # TODO
+
+    @handle("escape", "*", filter=insert_mode)
+    def _insert_all_completions(event: E) -> None:
+        """
+        `meta-*`: Insert all possible completions of the preceding text.
+        """
+        buff = event.current_buffer
+
+        # List all completions.
+        complete_event = CompleteEvent(text_inserted=False, completion_requested=True)
+        completions = list(
+            buff.completer.get_completions(buff.document, complete_event)
+        )
+
+        # Insert them.
+        text_to_insert = " ".join(c.text for c in completions)
+        buff.insert_text(text_to_insert)
+
+    @handle("c-x", "c-x")
+    def _toggle_start_end(event: E) -> None:
+        """
+        Move cursor back and forth between the start and end of the current
+        line.
+        """
+        buffer = event.current_buffer
+
+        if buffer.document.is_cursor_at_the_end_of_line:
+            buffer.cursor_position += buffer.document.get_start_of_line_position(
+                after_whitespace=False
+            )
+        else:
+            buffer.cursor_position += buffer.document.get_end_of_line_position()
+
+    @handle("c-@")  # Control-space or Control-@
+    def _start_selection(event: E) -> None:
+        """
+        Start of the selection (if the current buffer is not empty).
+        """
+        # Take the current cursor position as the start of this selection.
+        buff = event.current_buffer
+        if buff.text:
+            buff.start_selection(selection_type=SelectionType.CHARACTERS)
+
+    @handle("c-g", filter=~has_selection)
+    def _cancel(event: E) -> None:
+        """
+        Control + G: Cancel completion menu and validation state.
+        """
+        event.current_buffer.complete_state = None
+        event.current_buffer.validation_error = None
+
+    @handle("c-g", filter=has_selection)
+    def _cancel_selection(event: E) -> None:
+        """
+        Cancel selection.
+        """
+        event.current_buffer.exit_selection()
+
+    @handle("c-w", filter=has_selection)
+    @handle("c-x", "r", "k", filter=has_selection)
+    def _cut(event: E) -> None:
+        """
+        Cut selected text.
+        """
+        data = event.current_buffer.cut_selection()
+        event.app.clipboard.set_data(data)
+
+    @handle("escape", "w", filter=has_selection)
+    def _copy(event: E) -> None:
+        """
+        Copy selected text.
+        """
+        data = event.current_buffer.copy_selection()
+        event.app.clipboard.set_data(data)
+
+    @handle("escape", "left")
+    def _start_of_word(event: E) -> None:
+        """
+        Cursor to start of previous word.
+        """
+        buffer = event.current_buffer
+        buffer.cursor_position += (
+            buffer.document.find_previous_word_beginning(count=event.arg) or 0
+        )
+
+    @handle("escape", "right")
+    def _start_next_word(event: E) -> None:
+        """
+        Cursor to start of next word.
+        """
+        buffer = event.current_buffer
+        buffer.cursor_position += (
+            buffer.document.find_next_word_beginning(count=event.arg)
+            or buffer.document.get_end_of_document_position()
+        )
+
+    @handle("escape", "/", filter=insert_mode)
+    def _complete(event: E) -> None:
+        """
+        M-/: Complete.
+        """
+        b = event.current_buffer
+        if b.complete_state:
+            b.complete_next()
+        else:
+            b.start_completion(select_first=True)
+
+    @handle("c-c", ">", filter=has_selection)
+    def _indent(event: E) -> None:
+        """
+        Indent selected text.
+        """
+        buffer = event.current_buffer
+
+        buffer.cursor_position += buffer.document.get_start_of_line_position(
+            after_whitespace=True
+        )
+
+        from_, to = buffer.document.selection_range()
+        from_, _ = buffer.document.translate_index_to_position(from_)
+        to, _ = buffer.document.translate_index_to_position(to)
+
+        indent(buffer, from_, to + 1, count=event.arg)
+
+    @handle("c-c", "<", filter=has_selection)
+    def _unindent(event: E) -> None:
+        """
+        Unindent selected text.
+        """
+        buffer = event.current_buffer
+
+        from_, to = buffer.document.selection_range()
+        from_, _ = buffer.document.translate_index_to_position(from_)
+        to, _ = buffer.document.translate_index_to_position(to)
+
+        unindent(buffer, from_, to + 1, count=event.arg)
+
+    return ConditionalKeyBindings(key_bindings, emacs_mode)
+
+
+def load_emacs_search_bindings() -> KeyBindingsBase:
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+    from . import search
+
+    # NOTE: We don't bind 'Escape' to 'abort_search'. The reason is that we
+    #       want Alt+Enter to accept input directly in incremental search mode.
+    #       Instead, we have double escape.
+
+    handle("c-r")(search.start_reverse_incremental_search)
+    handle("c-s")(search.start_forward_incremental_search)
+
+    handle("c-c")(search.abort_search)
+    handle("c-g")(search.abort_search)
+    handle("c-r")(search.reverse_incremental_search)
+    handle("c-s")(search.forward_incremental_search)
+    handle("up")(search.reverse_incremental_search)
+    handle("down")(search.forward_incremental_search)
+    handle("enter")(search.accept_search)
+
+    # Handling of escape.
+    handle("escape", eager=True)(search.accept_search)
+
+    # Like Readline, it's more natural to accept the search when escape has
+    # been pressed, however instead the following two bindings could be used
+    # instead.
+    # #handle('escape', 'escape', eager=True)(search.abort_search)
+    # #handle('escape', 'enter', eager=True)(search.accept_search_and_accept_input)
+
+    # If Read-only: also include the following key bindings:
+
+    # '/' and '?' key bindings for searching, just like Vi mode.
+    handle("?", filter=is_read_only & ~vi_search_direction_reversed)(
+        search.start_reverse_incremental_search
+    )
+    handle("/", filter=is_read_only & ~vi_search_direction_reversed)(
+        search.start_forward_incremental_search
+    )
+    handle("?", filter=is_read_only & vi_search_direction_reversed)(
+        search.start_forward_incremental_search
+    )
+    handle("/", filter=is_read_only & vi_search_direction_reversed)(
+        search.start_reverse_incremental_search
+    )
+
+    @handle("n", filter=is_read_only)
+    def _jump_next(event: E) -> None:
+        "Jump to next match."
+        event.current_buffer.apply_search(
+            event.app.current_search_state,
+            include_current_position=False,
+            count=event.arg,
+        )
+
+    @handle("N", filter=is_read_only)
+    def _jump_prev(event: E) -> None:
+        "Jump to previous match."
+        event.current_buffer.apply_search(
+            ~event.app.current_search_state,
+            include_current_position=False,
+            count=event.arg,
+        )
+
+    return ConditionalKeyBindings(key_bindings, emacs_mode)
+
+
+def load_emacs_shift_selection_bindings() -> KeyBindingsBase:
+    """
+    Bindings to select text with shift + cursor movements
+    """
+
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+
+    def unshift_move(event: E) -> None:
+        """
+        Used for the shift selection mode. When called with
+        a shift + movement key press event, moves the cursor
+        as if shift is not pressed.
+        """
+        key = event.key_sequence[0].key
+
+        if key == Keys.ShiftUp:
+            event.current_buffer.auto_up(count=event.arg)
+            return
+        if key == Keys.ShiftDown:
+            event.current_buffer.auto_down(count=event.arg)
+            return
+
+        # the other keys are handled through their readline command
+        key_to_command: Dict[Union[Keys, str], str] = {
+            Keys.ShiftLeft: "backward-char",
+            Keys.ShiftRight: "forward-char",
+            Keys.ShiftHome: "beginning-of-line",
+            Keys.ShiftEnd: "end-of-line",
+            Keys.ControlShiftLeft: "backward-word",
+            Keys.ControlShiftRight: "forward-word",
+            Keys.ControlShiftHome: "beginning-of-buffer",
+            Keys.ControlShiftEnd: "end-of-buffer",
+        }
+
+        try:
+            # Both the dict lookup and `get_by_name` can raise KeyError.
+            binding = get_by_name(key_to_command[key])
+        except KeyError:
+            pass
+        else:  # (`else` is not really needed here.)
+            if isinstance(binding, Binding):
+                # (It should always be a binding here)
+                binding.call(event)
+
+    @handle("s-left", filter=~has_selection)
+    @handle("s-right", filter=~has_selection)
+    @handle("s-up", filter=~has_selection)
+    @handle("s-down", filter=~has_selection)
+    @handle("s-home", filter=~has_selection)
+    @handle("s-end", filter=~has_selection)
+    @handle("c-s-left", filter=~has_selection)
+    @handle("c-s-right", filter=~has_selection)
+    @handle("c-s-home", filter=~has_selection)
+    @handle("c-s-end", filter=~has_selection)
+    def _start_selection(event: E) -> None:
+        """
+        Start selection with shift + movement.
+        """
+        # Take the current cursor position as the start of this selection.
+        buff = event.current_buffer
+        if buff.text:
+            buff.start_selection(selection_type=SelectionType.CHARACTERS)
+
+            if buff.selection_state is not None:
+                # (`selection_state` should never be `None`, it is created by
+                # `start_selection`.)
+                buff.selection_state.enter_shift_mode()
+
+            # Then move the cursor
+            original_position = buff.cursor_position
+            unshift_move(event)
+            if buff.cursor_position == original_position:
+                # Cursor didn't actually move - so cancel selection
+                # to avoid having an empty selection
+                buff.exit_selection()
+
+    @handle("s-left", filter=shift_selection_mode)
+    @handle("s-right", filter=shift_selection_mode)
+    @handle("s-up", filter=shift_selection_mode)
+    @handle("s-down", filter=shift_selection_mode)
+    @handle("s-home", filter=shift_selection_mode)
+    @handle("s-end", filter=shift_selection_mode)
+    @handle("c-s-left", filter=shift_selection_mode)
+    @handle("c-s-right", filter=shift_selection_mode)
+    @handle("c-s-home", filter=shift_selection_mode)
+    @handle("c-s-end", filter=shift_selection_mode)
+    def _extend_selection(event: E) -> None:
+        """
+        Extend the selection
+        """
+        # Just move the cursor, like shift was not pressed
+        unshift_move(event)
+        buff = event.current_buffer
+
+        if buff.selection_state is not None:
+            if buff.cursor_position == buff.selection_state.original_cursor_position:
+                # selection is now empty, so cancel selection
+                buff.exit_selection()
+
+    @handle(Keys.Any, filter=shift_selection_mode)
+    def _replace_selection(event: E) -> None:
+        """
+        Replace selection by what is typed
+        """
+        event.current_buffer.cut_selection()
+        get_by_name("self-insert").call(event)
+
+    @handle("enter", filter=shift_selection_mode & is_multiline)
+    def _newline(event: E) -> None:
+        """
+        A newline replaces the selection
+        """
+        event.current_buffer.cut_selection()
+        event.current_buffer.newline(copy_margin=not in_paste_mode())
+
+    @handle("backspace", filter=shift_selection_mode)
+    def _delete(event: E) -> None:
+        """
+        Delete selection.
+        """
+        event.current_buffer.cut_selection()
+
+    @handle("c-y", filter=shift_selection_mode)
+    def _yank(event: E) -> None:
+        """
+        In shift selection mode, yanking (pasting) replace the selection.
+        """
+        buff = event.current_buffer
+        if buff.selection_state:
+            buff.cut_selection()
+        get_by_name("yank").call(event)
+
+    # moving the cursor in shift selection mode cancels the selection
+    @handle("left", filter=shift_selection_mode)
+    @handle("right", filter=shift_selection_mode)
+    @handle("up", filter=shift_selection_mode)
+    @handle("down", filter=shift_selection_mode)
+    @handle("home", filter=shift_selection_mode)
+    @handle("end", filter=shift_selection_mode)
+    @handle("c-left", filter=shift_selection_mode)
+    @handle("c-right", filter=shift_selection_mode)
+    @handle("c-home", filter=shift_selection_mode)
+    @handle("c-end", filter=shift_selection_mode)
+    def _cancel(event: E) -> None:
+        """
+        Cancel selection.
+        """
+        event.current_buffer.exit_selection()
+        # we then process the cursor movement
+        key_press = event.key_sequence[0]
+        event.key_processor.feed(key_press, first=True)
+
+    return ConditionalKeyBindings(key_bindings, emacs_mode)
diff --git a/src/prompt_toolkit/key_binding/bindings/focus.py b/src/prompt_toolkit/key_binding/bindings/focus.py
new file mode 100644
index 0000000..40844db
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/focus.py
@@ -0,0 +1,24 @@
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+
+__all__ = [
+    "focus_next",
+    "focus_previous",
+]
+
+E = KeyPressEvent
+
+
+def focus_next(event: E) -> None:
+    """
+    Focus the next visible Window.
+    (Often bound to the `Tab` key.)
+    """
+    event.app.layout.focus_next()
+
+
+def focus_previous(event: E) -> None:
+    """
+    Focus the previous visible Window.
+    (Often bound to the `BackTab` key.)
+    """
+    event.app.layout.focus_previous()
diff --git a/src/prompt_toolkit/key_binding/bindings/mouse.py b/src/prompt_toolkit/key_binding/bindings/mouse.py
new file mode 100644
index 0000000..916cd41
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/mouse.py
@@ -0,0 +1,347 @@
+import sys
+from typing import TYPE_CHECKING, FrozenSet
+
+from prompt_toolkit.data_structures import Point
+from prompt_toolkit.key_binding.key_processor import KeyPress, KeyPressEvent
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.mouse_events import (
+    MouseButton,
+    MouseEvent,
+    MouseEventType,
+    MouseModifier,
+)
+
+from ..key_bindings import KeyBindings
+
+if TYPE_CHECKING:
+    from prompt_toolkit.key_binding.key_bindings import NotImplementedOrNone
+
+__all__ = [
+    "load_mouse_bindings",
+]
+
+E = KeyPressEvent
+
+# fmt: off
+# flake8: noqa E201
+SCROLL_UP   = MouseEventType.SCROLL_UP
+SCROLL_DOWN = MouseEventType.SCROLL_DOWN
+MOUSE_DOWN  = MouseEventType.MOUSE_DOWN
+MOUSE_MOVE  = MouseEventType.MOUSE_MOVE
+MOUSE_UP    = MouseEventType.MOUSE_UP
+
+NO_MODIFIER      : FrozenSet[MouseModifier] = frozenset()
+SHIFT            : FrozenSet[MouseModifier] = frozenset({MouseModifier.SHIFT})
+ALT              : FrozenSet[MouseModifier] = frozenset({MouseModifier.ALT})
+SHIFT_ALT        : FrozenSet[MouseModifier] = frozenset({MouseModifier.SHIFT, MouseModifier.ALT})
+CONTROL          : FrozenSet[MouseModifier] = frozenset({MouseModifier.CONTROL})
+SHIFT_CONTROL    : FrozenSet[MouseModifier] = frozenset({MouseModifier.SHIFT, MouseModifier.CONTROL})
+ALT_CONTROL      : FrozenSet[MouseModifier] = frozenset({MouseModifier.ALT, MouseModifier.CONTROL})
+SHIFT_ALT_CONTROL: FrozenSet[MouseModifier] = frozenset({MouseModifier.SHIFT, MouseModifier.ALT, MouseModifier.CONTROL})
+UNKNOWN_MODIFIER : FrozenSet[MouseModifier] = frozenset()
+
+LEFT           = MouseButton.LEFT
+MIDDLE         = MouseButton.MIDDLE
+RIGHT          = MouseButton.RIGHT
+NO_BUTTON      = MouseButton.NONE
+UNKNOWN_BUTTON = MouseButton.UNKNOWN
+
+xterm_sgr_mouse_events = {
+    ( 0, 'm') : (LEFT, MOUSE_UP, NO_MODIFIER),                # left_up                       0+ + +  =0
+    ( 4, 'm') : (LEFT, MOUSE_UP, SHIFT),                      # left_up     Shift             0+4+ +  =4
+    ( 8, 'm') : (LEFT, MOUSE_UP, ALT),                        # left_up           Alt         0+ +8+  =8
+    (12, 'm') : (LEFT, MOUSE_UP, SHIFT_ALT),                  # left_up     Shift Alt         0+4+8+  =12
+    (16, 'm') : (LEFT, MOUSE_UP, CONTROL),                    # left_up               Control 0+ + +16=16
+    (20, 'm') : (LEFT, MOUSE_UP, SHIFT_CONTROL),              # left_up     Shift     Control 0+4+ +16=20
+    (24, 'm') : (LEFT, MOUSE_UP, ALT_CONTROL),                # left_up           Alt Control 0+ +8+16=24
+    (28, 'm') : (LEFT, MOUSE_UP, SHIFT_ALT_CONTROL),          # left_up     Shift Alt Control 0+4+8+16=28
+
+    ( 1, 'm') : (MIDDLE, MOUSE_UP, NO_MODIFIER),              # middle_up                     1+ + +  =1
+    ( 5, 'm') : (MIDDLE, MOUSE_UP, SHIFT),                    # middle_up   Shift             1+4+ +  =5
+    ( 9, 'm') : (MIDDLE, MOUSE_UP, ALT),                      # middle_up         Alt         1+ +8+  =9
+    (13, 'm') : (MIDDLE, MOUSE_UP, SHIFT_ALT),                # middle_up   Shift Alt         1+4+8+  =13
+    (17, 'm') : (MIDDLE, MOUSE_UP, CONTROL),                  # middle_up             Control 1+ + +16=17
+    (21, 'm') : (MIDDLE, MOUSE_UP, SHIFT_CONTROL),            # middle_up   Shift     Control 1+4+ +16=21
+    (25, 'm') : (MIDDLE, MOUSE_UP, ALT_CONTROL),              # middle_up         Alt Control 1+ +8+16=25
+    (29, 'm') : (MIDDLE, MOUSE_UP, SHIFT_ALT_CONTROL),        # middle_up   Shift Alt Control 1+4+8+16=29
+
+    ( 2, 'm') : (RIGHT, MOUSE_UP, NO_MODIFIER),               # right_up                      2+ + +  =2
+    ( 6, 'm') : (RIGHT, MOUSE_UP, SHIFT),                     # right_up    Shift             2+4+ +  =6
+    (10, 'm') : (RIGHT, MOUSE_UP, ALT),                       # right_up          Alt         2+ +8+  =10
+    (14, 'm') : (RIGHT, MOUSE_UP, SHIFT_ALT),                 # right_up    Shift Alt         2+4+8+  =14
+    (18, 'm') : (RIGHT, MOUSE_UP, CONTROL),                   # right_up              Control 2+ + +16=18
+    (22, 'm') : (RIGHT, MOUSE_UP, SHIFT_CONTROL),             # right_up    Shift     Control 2+4+ +16=22
+    (26, 'm') : (RIGHT, MOUSE_UP, ALT_CONTROL),               # right_up          Alt Control 2+ +8+16=26
+    (30, 'm') : (RIGHT, MOUSE_UP, SHIFT_ALT_CONTROL),         # right_up    Shift Alt Control 2+4+8+16=30
+
+    ( 0, 'M') : (LEFT, MOUSE_DOWN, NO_MODIFIER),              # left_down                     0+ + +  =0
+    ( 4, 'M') : (LEFT, MOUSE_DOWN, SHIFT),                    # left_down   Shift             0+4+ +  =4
+    ( 8, 'M') : (LEFT, MOUSE_DOWN, ALT),                      # left_down         Alt         0+ +8+  =8
+    (12, 'M') : (LEFT, MOUSE_DOWN, SHIFT_ALT),                # left_down   Shift Alt         0+4+8+  =12
+    (16, 'M') : (LEFT, MOUSE_DOWN, CONTROL),                  # left_down             Control 0+ + +16=16
+    (20, 'M') : (LEFT, MOUSE_DOWN, SHIFT_CONTROL),            # left_down   Shift     Control 0+4+ +16=20
+    (24, 'M') : (LEFT, MOUSE_DOWN, ALT_CONTROL),              # left_down         Alt Control 0+ +8+16=24
+    (28, 'M') : (LEFT, MOUSE_DOWN, SHIFT_ALT_CONTROL),        # left_down   Shift Alt Control 0+4+8+16=28
+
+    ( 1, 'M') : (MIDDLE, MOUSE_DOWN, NO_MODIFIER),            # middle_down                   1+ + +  =1
+    ( 5, 'M') : (MIDDLE, MOUSE_DOWN, SHIFT),                  # middle_down Shift             1+4+ +  =5
+    ( 9, 'M') : (MIDDLE, MOUSE_DOWN, ALT),                    # middle_down       Alt         1+ +8+  =9
+    (13, 'M') : (MIDDLE, MOUSE_DOWN, SHIFT_ALT),              # middle_down Shift Alt         1+4+8+  =13
+    (17, 'M') : (MIDDLE, MOUSE_DOWN, CONTROL),                # middle_down           Control 1+ + +16=17
+    (21, 'M') : (MIDDLE, MOUSE_DOWN, SHIFT_CONTROL),          # middle_down Shift     Control 1+4+ +16=21
+    (25, 'M') : (MIDDLE, MOUSE_DOWN, ALT_CONTROL),            # middle_down       Alt Control 1+ +8+16=25
+    (29, 'M') : (MIDDLE, MOUSE_DOWN, SHIFT_ALT_CONTROL),      # middle_down Shift Alt Control 1+4+8+16=29
+
+    ( 2, 'M') : (RIGHT, MOUSE_DOWN, NO_MODIFIER),             # right_down                    2+ + +  =2
+    ( 6, 'M') : (RIGHT, MOUSE_DOWN, SHIFT),                   # right_down  Shift             2+4+ +  =6
+    (10, 'M') : (RIGHT, MOUSE_DOWN, ALT),                     # right_down        Alt         2+ +8+  =10
+    (14, 'M') : (RIGHT, MOUSE_DOWN, SHIFT_ALT),               # right_down  Shift Alt         2+4+8+  =14
+    (18, 'M') : (RIGHT, MOUSE_DOWN, CONTROL),                 # right_down            Control 2+ + +16=18
+    (22, 'M') : (RIGHT, MOUSE_DOWN, SHIFT_CONTROL),           # right_down  Shift     Control 2+4+ +16=22
+    (26, 'M') : (RIGHT, MOUSE_DOWN, ALT_CONTROL),             # right_down        Alt Control 2+ +8+16=26
+    (30, 'M') : (RIGHT, MOUSE_DOWN, SHIFT_ALT_CONTROL),       # right_down  Shift Alt Control 2+4+8+16=30
+
+    (32, 'M') : (LEFT, MOUSE_MOVE, NO_MODIFIER),              # left_drag                     32+ + +  =32
+    (36, 'M') : (LEFT, MOUSE_MOVE, SHIFT),                    # left_drag   Shift             32+4+ +  =36
+    (40, 'M') : (LEFT, MOUSE_MOVE, ALT),                      # left_drag         Alt         32+ +8+  =40
+    (44, 'M') : (LEFT, MOUSE_MOVE, SHIFT_ALT),                # left_drag   Shift Alt         32+4+8+  =44
+    (48, 'M') : (LEFT, MOUSE_MOVE, CONTROL),                  # left_drag             Control 32+ + +16=48
+    (52, 'M') : (LEFT, MOUSE_MOVE, SHIFT_CONTROL),            # left_drag   Shift     Control 32+4+ +16=52
+    (56, 'M') : (LEFT, MOUSE_MOVE, ALT_CONTROL),              # left_drag         Alt Control 32+ +8+16=56
+    (60, 'M') : (LEFT, MOUSE_MOVE, SHIFT_ALT_CONTROL),        # left_drag   Shift Alt Control 32+4+8+16=60
+
+    (33, 'M') : (MIDDLE, MOUSE_MOVE, NO_MODIFIER),            # middle_drag                   33+ + +  =33
+    (37, 'M') : (MIDDLE, MOUSE_MOVE, SHIFT),                  # middle_drag Shift             33+4+ +  =37
+    (41, 'M') : (MIDDLE, MOUSE_MOVE, ALT),                    # middle_drag       Alt         33+ +8+  =41
+    (45, 'M') : (MIDDLE, MOUSE_MOVE, SHIFT_ALT),              # middle_drag Shift Alt         33+4+8+  =45
+    (49, 'M') : (MIDDLE, MOUSE_MOVE, CONTROL),                # middle_drag           Control 33+ + +16=49
+    (53, 'M') : (MIDDLE, MOUSE_MOVE, SHIFT_CONTROL),          # middle_drag Shift     Control 33+4+ +16=53
+    (57, 'M') : (MIDDLE, MOUSE_MOVE, ALT_CONTROL),            # middle_drag       Alt Control 33+ +8+16=57
+    (61, 'M') : (MIDDLE, MOUSE_MOVE, SHIFT_ALT_CONTROL),      # middle_drag Shift Alt Control 33+4+8+16=61
+
+    (34, 'M') : (RIGHT, MOUSE_MOVE, NO_MODIFIER),             # right_drag                    34+ + +  =34
+    (38, 'M') : (RIGHT, MOUSE_MOVE, SHIFT),                   # right_drag  Shift             34+4+ +  =38
+    (42, 'M') : (RIGHT, MOUSE_MOVE, ALT),                     # right_drag        Alt         34+ +8+  =42
+    (46, 'M') : (RIGHT, MOUSE_MOVE, SHIFT_ALT),               # right_drag  Shift Alt         34+4+8+  =46
+    (50, 'M') : (RIGHT, MOUSE_MOVE, CONTROL),                 # right_drag            Control 34+ + +16=50
+    (54, 'M') : (RIGHT, MOUSE_MOVE, SHIFT_CONTROL),           # right_drag  Shift     Control 34+4+ +16=54
+    (58, 'M') : (RIGHT, MOUSE_MOVE, ALT_CONTROL),             # right_drag        Alt Control 34+ +8+16=58
+    (62, 'M') : (RIGHT, MOUSE_MOVE, SHIFT_ALT_CONTROL),       # right_drag  Shift Alt Control 34+4+8+16=62
+
+    (35, 'M') : (NO_BUTTON, MOUSE_MOVE, NO_MODIFIER),         # none_drag                     35+ + +  =35
+    (39, 'M') : (NO_BUTTON, MOUSE_MOVE, SHIFT),               # none_drag   Shift             35+4+ +  =39
+    (43, 'M') : (NO_BUTTON, MOUSE_MOVE, ALT),                 # none_drag         Alt         35+ +8+  =43
+    (47, 'M') : (NO_BUTTON, MOUSE_MOVE, SHIFT_ALT),           # none_drag   Shift Alt         35+4+8+  =47
+    (51, 'M') : (NO_BUTTON, MOUSE_MOVE, CONTROL),             # none_drag             Control 35+ + +16=51
+    (55, 'M') : (NO_BUTTON, MOUSE_MOVE, SHIFT_CONTROL),       # none_drag   Shift     Control 35+4+ +16=55
+    (59, 'M') : (NO_BUTTON, MOUSE_MOVE, ALT_CONTROL),         # none_drag         Alt Control 35+ +8+16=59
+    (63, 'M') : (NO_BUTTON, MOUSE_MOVE, SHIFT_ALT_CONTROL),   # none_drag   Shift Alt Control 35+4+8+16=63
+
+    (64, 'M') : (NO_BUTTON, SCROLL_UP, NO_MODIFIER),          # scroll_up                     64+ + +  =64
+    (68, 'M') : (NO_BUTTON, SCROLL_UP, SHIFT),                # scroll_up   Shift             64+4+ +  =68
+    (72, 'M') : (NO_BUTTON, SCROLL_UP, ALT),                  # scroll_up         Alt         64+ +8+  =72
+    (76, 'M') : (NO_BUTTON, SCROLL_UP, SHIFT_ALT),            # scroll_up   Shift Alt         64+4+8+  =76
+    (80, 'M') : (NO_BUTTON, SCROLL_UP, CONTROL),              # scroll_up             Control 64+ + +16=80
+    (84, 'M') : (NO_BUTTON, SCROLL_UP, SHIFT_CONTROL),        # scroll_up   Shift     Control 64+4+ +16=84
+    (88, 'M') : (NO_BUTTON, SCROLL_UP, ALT_CONTROL),          # scroll_up         Alt Control 64+ +8+16=88
+    (92, 'M') : (NO_BUTTON, SCROLL_UP, SHIFT_ALT_CONTROL),    # scroll_up   Shift Alt Control 64+4+8+16=92
+
+    (65, 'M') : (NO_BUTTON, SCROLL_DOWN, NO_MODIFIER),        # scroll_down                   64+ + +  =65
+    (69, 'M') : (NO_BUTTON, SCROLL_DOWN, SHIFT),              # scroll_down Shift             64+4+ +  =69
+    (73, 'M') : (NO_BUTTON, SCROLL_DOWN, ALT),                # scroll_down       Alt         64+ +8+  =73
+    (77, 'M') : (NO_BUTTON, SCROLL_DOWN, SHIFT_ALT),          # scroll_down Shift Alt         64+4+8+  =77
+    (81, 'M') : (NO_BUTTON, SCROLL_DOWN, CONTROL),            # scroll_down           Control 64+ + +16=81
+    (85, 'M') : (NO_BUTTON, SCROLL_DOWN, SHIFT_CONTROL),      # scroll_down Shift     Control 64+4+ +16=85
+    (89, 'M') : (NO_BUTTON, SCROLL_DOWN, ALT_CONTROL),        # scroll_down       Alt Control 64+ +8+16=89
+    (93, 'M') : (NO_BUTTON, SCROLL_DOWN, SHIFT_ALT_CONTROL),  # scroll_down Shift Alt Control 64+4+8+16=93
+}
+
+typical_mouse_events = {
+    32: (LEFT           , MOUSE_DOWN , UNKNOWN_MODIFIER),
+    33: (MIDDLE         , MOUSE_DOWN , UNKNOWN_MODIFIER),
+    34: (RIGHT          , MOUSE_DOWN , UNKNOWN_MODIFIER),
+    35: (UNKNOWN_BUTTON , MOUSE_UP   , UNKNOWN_MODIFIER),
+
+    64: (LEFT           , MOUSE_MOVE , UNKNOWN_MODIFIER),
+    65: (MIDDLE         , MOUSE_MOVE , UNKNOWN_MODIFIER),
+    66: (RIGHT          , MOUSE_MOVE , UNKNOWN_MODIFIER),
+    67: (NO_BUTTON      , MOUSE_MOVE , UNKNOWN_MODIFIER),
+
+    96: (NO_BUTTON      , SCROLL_UP  , UNKNOWN_MODIFIER),
+    97: (NO_BUTTON      , SCROLL_DOWN, UNKNOWN_MODIFIER),
+}
+
+urxvt_mouse_events={
+    32: (UNKNOWN_BUTTON, MOUSE_DOWN , UNKNOWN_MODIFIER),
+    35: (UNKNOWN_BUTTON, MOUSE_UP   , UNKNOWN_MODIFIER),
+    96: (NO_BUTTON     , SCROLL_UP  , UNKNOWN_MODIFIER),
+    97: (NO_BUTTON     , SCROLL_DOWN, UNKNOWN_MODIFIER),
+}
+# fmt:on
+
+
+def load_mouse_bindings() -> KeyBindings:
+    """
+    Key bindings, required for mouse support.
+    (Mouse events enter through the key binding system.)
+    """
+    key_bindings = KeyBindings()
+
+    @key_bindings.add(Keys.Vt100MouseEvent)
+    def _(event: E) -> "NotImplementedOrNone":
+        """
+        Handling of incoming mouse event.
+        """
+        # TypicaL:   "eSC[MaB*"
+        # Urxvt:     "Esc[96;14;13M"
+        # Xterm SGR: "Esc[<64;85;12M"
+
+        # Parse incoming packet.
+        if event.data[2] == "M":
+            # Typical.
+            mouse_event, x, y = map(ord, event.data[3:])
+
+            # TODO: Is it possible to add modifiers here?
+            mouse_button, mouse_event_type, mouse_modifiers = typical_mouse_events[
+                mouse_event
+            ]
+
+            # Handle situations where `PosixStdinReader` used surrogateescapes.
+            if x >= 0xDC00:
+                x -= 0xDC00
+            if y >= 0xDC00:
+                y -= 0xDC00
+
+            x -= 32
+            y -= 32
+        else:
+            # Urxvt and Xterm SGR.
+            # When the '<' is not present, we are not using the Xterm SGR mode,
+            # but Urxvt instead.
+            data = event.data[2:]
+            if data[:1] == "<":
+                sgr = True
+                data = data[1:]
+            else:
+                sgr = False
+
+            # Extract coordinates.
+            mouse_event, x, y = map(int, data[:-1].split(";"))
+            m = data[-1]
+
+            # Parse event type.
+            if sgr:
+                try:
+                    (
+                        mouse_button,
+                        mouse_event_type,
+                        mouse_modifiers,
+                    ) = xterm_sgr_mouse_events[mouse_event, m]
+                except KeyError:
+                    return NotImplemented
+
+            else:
+                # Some other terminals, like urxvt, Hyper terminal, ...
+                (
+                    mouse_button,
+                    mouse_event_type,
+                    mouse_modifiers,
+                ) = urxvt_mouse_events.get(
+                    mouse_event, (UNKNOWN_BUTTON, MOUSE_MOVE, UNKNOWN_MODIFIER)
+                )
+
+        x -= 1
+        y -= 1
+
+        # Only handle mouse events when we know the window height.
+        if event.app.renderer.height_is_known and mouse_event_type is not None:
+            # Take region above the layout into account. The reported
+            # coordinates are absolute to the visible part of the terminal.
+            from prompt_toolkit.renderer import HeightIsUnknownError
+
+            try:
+                y -= event.app.renderer.rows_above_layout
+            except HeightIsUnknownError:
+                return NotImplemented
+
+            # Call the mouse handler from the renderer.
+
+            # Note: This can return `NotImplemented` if no mouse handler was
+            #       found for this position, or if no repainting needs to
+            #       happen. this way, we avoid excessive repaints during mouse
+            #       movements.
+            handler = event.app.renderer.mouse_handlers.mouse_handlers[y][x]
+            return handler(
+                MouseEvent(
+                    position=Point(x=x, y=y),
+                    event_type=mouse_event_type,
+                    button=mouse_button,
+                    modifiers=mouse_modifiers,
+                )
+            )
+
+        return NotImplemented
+
+    @key_bindings.add(Keys.ScrollUp)
+    def _scroll_up(event: E) -> None:
+        """
+        Scroll up event without cursor position.
+        """
+        # We don't receive a cursor position, so we don't know which window to
+        # scroll. Just send an 'up' key press instead.
+        event.key_processor.feed(KeyPress(Keys.Up), first=True)
+
+    @key_bindings.add(Keys.ScrollDown)
+    def _scroll_down(event: E) -> None:
+        """
+        Scroll down event without cursor position.
+        """
+        event.key_processor.feed(KeyPress(Keys.Down), first=True)
+
+    @key_bindings.add(Keys.WindowsMouseEvent)
+    def _mouse(event: E) -> "NotImplementedOrNone":
+        """
+        Handling of mouse events for Windows.
+        """
+        # This key binding should only exist for Windows.
+        if sys.platform == "win32":
+            # Parse data.
+            pieces = event.data.split(";")
+
+            button = MouseButton(pieces[0])
+            event_type = MouseEventType(pieces[1])
+            x = int(pieces[2])
+            y = int(pieces[3])
+
+            # Make coordinates absolute to the visible part of the terminal.
+            output = event.app.renderer.output
+
+            from prompt_toolkit.output.win32 import Win32Output
+            from prompt_toolkit.output.windows10 import Windows10_Output
+
+            if isinstance(output, (Win32Output, Windows10_Output)):
+                screen_buffer_info = output.get_win32_screen_buffer_info()
+                rows_above_cursor = (
+                    screen_buffer_info.dwCursorPosition.Y
+                    - event.app.renderer._cursor_pos.y
+                )
+                y -= rows_above_cursor
+
+                # Call the mouse event handler.
+                # (Can return `NotImplemented`.)
+                handler = event.app.renderer.mouse_handlers.mouse_handlers[y][x]
+
+                return handler(
+                    MouseEvent(
+                        position=Point(x=x, y=y),
+                        event_type=event_type,
+                        button=button,
+                        modifiers=UNKNOWN_MODIFIER,
+                    )
+                )
+
+        # No mouse handler found. Return `NotImplemented` so that we don't
+        # invalidate the UI.
+        return NotImplemented
+
+    return key_bindings
diff --git a/src/prompt_toolkit/key_binding/bindings/named_commands.py b/src/prompt_toolkit/key_binding/bindings/named_commands.py
new file mode 100644
index 0000000..e0796ef
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/named_commands.py
@@ -0,0 +1,687 @@
+"""
+Key bindings which are also known by GNU Readline by the given names.
+
+See: http://www.delorie.com/gnu/docs/readline/rlman_13.html
+"""
+from typing import Callable, Dict, TypeVar, Union, cast
+
+from prompt_toolkit.document import Document
+from prompt_toolkit.enums import EditingMode
+from prompt_toolkit.key_binding.key_bindings import Binding, key_binding
+from prompt_toolkit.key_binding.key_processor import KeyPress, KeyPressEvent
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.layout.controls import BufferControl
+from prompt_toolkit.search import SearchDirection
+from prompt_toolkit.selection import PasteMode
+
+from .completion import display_completions_like_readline, generate_completions
+
+__all__ = [
+    "get_by_name",
+]
+
+
+# Typing.
+_Handler = Callable[[KeyPressEvent], None]
+_HandlerOrBinding = Union[_Handler, Binding]
+_T = TypeVar("_T", bound=_HandlerOrBinding)
+E = KeyPressEvent
+
+
+# Registry that maps the Readline command names to their handlers.
+_readline_commands: Dict[str, Binding] = {}
+
+
+def register(name: str) -> Callable[[_T], _T]:
+    """
+    Store handler in the `_readline_commands` dictionary.
+    """
+
+    def decorator(handler: _T) -> _T:
+        "`handler` is a callable or Binding."
+        if isinstance(handler, Binding):
+            _readline_commands[name] = handler
+        else:
+            _readline_commands[name] = key_binding()(cast(_Handler, handler))
+
+        return handler
+
+    return decorator
+
+
+def get_by_name(name: str) -> Binding:
+    """
+    Return the handler for the (Readline) command with the given name.
+    """
+    try:
+        return _readline_commands[name]
+    except KeyError as e:
+        raise KeyError("Unknown Readline command: %r" % name) from e
+
+
+#
+# Commands for moving
+# See: http://www.delorie.com/gnu/docs/readline/rlman_14.html
+#
+
+
+@register("beginning-of-buffer")
+def beginning_of_buffer(event: E) -> None:
+    """
+    Move to the start of the buffer.
+    """
+    buff = event.current_buffer
+    buff.cursor_position = 0
+
+
+@register("end-of-buffer")
+def end_of_buffer(event: E) -> None:
+    """
+    Move to the end of the buffer.
+    """
+    buff = event.current_buffer
+    buff.cursor_position = len(buff.text)
+
+
+@register("beginning-of-line")
+def beginning_of_line(event: E) -> None:
+    """
+    Move to the start of the current line.
+    """
+    buff = event.current_buffer
+    buff.cursor_position += buff.document.get_start_of_line_position(
+        after_whitespace=False
+    )
+
+
+@register("end-of-line")
+def end_of_line(event: E) -> None:
+    """
+    Move to the end of the line.
+    """
+    buff = event.current_buffer
+    buff.cursor_position += buff.document.get_end_of_line_position()
+
+
+@register("forward-char")
+def forward_char(event: E) -> None:
+    """
+    Move forward a character.
+    """
+    buff = event.current_buffer
+    buff.cursor_position += buff.document.get_cursor_right_position(count=event.arg)
+
+
+@register("backward-char")
+def backward_char(event: E) -> None:
+    "Move back a character."
+    buff = event.current_buffer
+    buff.cursor_position += buff.document.get_cursor_left_position(count=event.arg)
+
+
+@register("forward-word")
+def forward_word(event: E) -> None:
+    """
+    Move forward to the end of the next word. Words are composed of letters and
+    digits.
+    """
+    buff = event.current_buffer
+    pos = buff.document.find_next_word_ending(count=event.arg)
+
+    if pos:
+        buff.cursor_position += pos
+
+
+@register("backward-word")
+def backward_word(event: E) -> None:
+    """
+    Move back to the start of the current or previous word. Words are composed
+    of letters and digits.
+    """
+    buff = event.current_buffer
+    pos = buff.document.find_previous_word_beginning(count=event.arg)
+
+    if pos:
+        buff.cursor_position += pos
+
+
+@register("clear-screen")
+def clear_screen(event: E) -> None:
+    """
+    Clear the screen and redraw everything at the top of the screen.
+    """
+    event.app.renderer.clear()
+
+
+@register("redraw-current-line")
+def redraw_current_line(event: E) -> None:
+    """
+    Refresh the current line.
+    (Readline defines this command, but prompt-toolkit doesn't have it.)
+    """
+    pass
+
+
+#
+# Commands for manipulating the history.
+# See: http://www.delorie.com/gnu/docs/readline/rlman_15.html
+#
+
+
+@register("accept-line")
+def accept_line(event: E) -> None:
+    """
+    Accept the line regardless of where the cursor is.
+    """
+    event.current_buffer.validate_and_handle()
+
+
+@register("previous-history")
+def previous_history(event: E) -> None:
+    """
+    Move `back` through the history list, fetching the previous command.
+    """
+    event.current_buffer.history_backward(count=event.arg)
+
+
+@register("next-history")
+def next_history(event: E) -> None:
+    """
+    Move `forward` through the history list, fetching the next command.
+    """
+    event.current_buffer.history_forward(count=event.arg)
+
+
+@register("beginning-of-history")
+def beginning_of_history(event: E) -> None:
+    """
+    Move to the first line in the history.
+    """
+    event.current_buffer.go_to_history(0)
+
+
+@register("end-of-history")
+def end_of_history(event: E) -> None:
+    """
+    Move to the end of the input history, i.e., the line currently being entered.
+    """
+    event.current_buffer.history_forward(count=10**100)
+    buff = event.current_buffer
+    buff.go_to_history(len(buff._working_lines) - 1)
+
+
+@register("reverse-search-history")
+def reverse_search_history(event: E) -> None:
+    """
+    Search backward starting at the current line and moving `up` through
+    the history as necessary. This is an incremental search.
+    """
+    control = event.app.layout.current_control
+
+    if isinstance(control, BufferControl) and control.search_buffer_control:
+        event.app.current_search_state.direction = SearchDirection.BACKWARD
+        event.app.layout.current_control = control.search_buffer_control
+
+
+#
+# Commands for changing text
+#
+
+
+@register("end-of-file")
+def end_of_file(event: E) -> None:
+    """
+    Exit.
+    """
+    event.app.exit()
+
+
+@register("delete-char")
+def delete_char(event: E) -> None:
+    """
+    Delete character before the cursor.
+    """
+    deleted = event.current_buffer.delete(count=event.arg)
+    if not deleted:
+        event.app.output.bell()
+
+
+@register("backward-delete-char")
+def backward_delete_char(event: E) -> None:
+    """
+    Delete the character behind the cursor.
+    """
+    if event.arg < 0:
+        # When a negative argument has been given, this should delete in front
+        # of the cursor.
+        deleted = event.current_buffer.delete(count=-event.arg)
+    else:
+        deleted = event.current_buffer.delete_before_cursor(count=event.arg)
+
+    if not deleted:
+        event.app.output.bell()
+
+
+@register("self-insert")
+def self_insert(event: E) -> None:
+    """
+    Insert yourself.
+    """
+    event.current_buffer.insert_text(event.data * event.arg)
+
+
+@register("transpose-chars")
+def transpose_chars(event: E) -> None:
+    """
+    Emulate Emacs transpose-char behavior: at the beginning of the buffer,
+    do nothing.  At the end of a line or buffer, swap the characters before
+    the cursor.  Otherwise, move the cursor right, and then swap the
+    characters before the cursor.
+    """
+    b = event.current_buffer
+    p = b.cursor_position
+    if p == 0:
+        return
+    elif p == len(b.text) or b.text[p] == "\n":
+        b.swap_characters_before_cursor()
+    else:
+        b.cursor_position += b.document.get_cursor_right_position()
+        b.swap_characters_before_cursor()
+
+
+@register("uppercase-word")
+def uppercase_word(event: E) -> None:
+    """
+    Uppercase the current (or following) word.
+    """
+    buff = event.current_buffer
+
+    for i in range(event.arg):
+        pos = buff.document.find_next_word_ending()
+        words = buff.document.text_after_cursor[:pos]
+        buff.insert_text(words.upper(), overwrite=True)
+
+
+@register("downcase-word")
+def downcase_word(event: E) -> None:
+    """
+    Lowercase the current (or following) word.
+    """
+    buff = event.current_buffer
+
+    for i in range(event.arg):  # XXX: not DRY: see meta_c and meta_u!!
+        pos = buff.document.find_next_word_ending()
+        words = buff.document.text_after_cursor[:pos]
+        buff.insert_text(words.lower(), overwrite=True)
+
+
+@register("capitalize-word")
+def capitalize_word(event: E) -> None:
+    """
+    Capitalize the current (or following) word.
+    """
+    buff = event.current_buffer
+
+    for i in range(event.arg):
+        pos = buff.document.find_next_word_ending()
+        words = buff.document.text_after_cursor[:pos]
+        buff.insert_text(words.title(), overwrite=True)
+
+
+@register("quoted-insert")
+def quoted_insert(event: E) -> None:
+    """
+    Add the next character typed to the line verbatim. This is how to insert
+    key sequences like C-q, for example.
+    """
+    event.app.quoted_insert = True
+
+
+#
+# Killing and yanking.
+#
+
+
+@register("kill-line")
+def kill_line(event: E) -> None:
+    """
+    Kill the text from the cursor to the end of the line.
+
+    If we are at the end of the line, this should remove the newline.
+    (That way, it is possible to delete multiple lines by executing this
+    command multiple times.)
+    """
+    buff = event.current_buffer
+    if event.arg < 0:
+        deleted = buff.delete_before_cursor(
+            count=-buff.document.get_start_of_line_position()
+        )
+    else:
+        if buff.document.current_char == "\n":
+            deleted = buff.delete(1)
+        else:
+            deleted = buff.delete(count=buff.document.get_end_of_line_position())
+    event.app.clipboard.set_text(deleted)
+
+
+@register("kill-word")
+def kill_word(event: E) -> None:
+    """
+    Kill from point to the end of the current word, or if between words, to the
+    end of the next word. Word boundaries are the same as forward-word.
+    """
+    buff = event.current_buffer
+    pos = buff.document.find_next_word_ending(count=event.arg)
+
+    if pos:
+        deleted = buff.delete(count=pos)
+
+        if event.is_repeat:
+            deleted = event.app.clipboard.get_data().text + deleted
+
+        event.app.clipboard.set_text(deleted)
+
+
+@register("unix-word-rubout")
+def unix_word_rubout(event: E, WORD: bool = True) -> None:
+    """
+    Kill the word behind point, using whitespace as a word boundary.
+    Usually bound to ControlW.
+    """
+    buff = event.current_buffer
+    pos = buff.document.find_start_of_previous_word(count=event.arg, WORD=WORD)
+
+    if pos is None:
+        # Nothing found? delete until the start of the document.  (The
+        # input starts with whitespace and no words were found before the
+        # cursor.)
+        pos = -buff.cursor_position
+
+    if pos:
+        deleted = buff.delete_before_cursor(count=-pos)
+
+        # If the previous key press was also Control-W, concatenate deleted
+        # text.
+        if event.is_repeat:
+            deleted += event.app.clipboard.get_data().text
+
+        event.app.clipboard.set_text(deleted)
+    else:
+        # Nothing to delete. Bell.
+        event.app.output.bell()
+
+
+@register("backward-kill-word")
+def backward_kill_word(event: E) -> None:
+    """
+    Kills the word before point, using "not a letter nor a digit" as a word boundary.
+    Usually bound to M-Del or M-Backspace.
+    """
+    unix_word_rubout(event, WORD=False)
+
+
+@register("delete-horizontal-space")
+def delete_horizontal_space(event: E) -> None:
+    """
+    Delete all spaces and tabs around point.
+    """
+    buff = event.current_buffer
+    text_before_cursor = buff.document.text_before_cursor
+    text_after_cursor = buff.document.text_after_cursor
+
+    delete_before = len(text_before_cursor) - len(text_before_cursor.rstrip("\t "))
+    delete_after = len(text_after_cursor) - len(text_after_cursor.lstrip("\t "))
+
+    buff.delete_before_cursor(count=delete_before)
+    buff.delete(count=delete_after)
+
+
+@register("unix-line-discard")
+def unix_line_discard(event: E) -> None:
+    """
+    Kill backward from the cursor to the beginning of the current line.
+    """
+    buff = event.current_buffer
+
+    if buff.document.cursor_position_col == 0 and buff.document.cursor_position > 0:
+        buff.delete_before_cursor(count=1)
+    else:
+        deleted = buff.delete_before_cursor(
+            count=-buff.document.get_start_of_line_position()
+        )
+        event.app.clipboard.set_text(deleted)
+
+
+@register("yank")
+def yank(event: E) -> None:
+    """
+    Paste before cursor.
+    """
+    event.current_buffer.paste_clipboard_data(
+        event.app.clipboard.get_data(), count=event.arg, paste_mode=PasteMode.EMACS
+    )
+
+
+@register("yank-nth-arg")
+def yank_nth_arg(event: E) -> None:
+    """
+    Insert the first argument of the previous command. With an argument, insert
+    the nth word from the previous command (start counting at 0).
+    """
+    n = event.arg if event.arg_present else None
+    event.current_buffer.yank_nth_arg(n)
+
+
+@register("yank-last-arg")
+def yank_last_arg(event: E) -> None:
+    """
+    Like `yank_nth_arg`, but if no argument has been given, yank the last word
+    of each line.
+    """
+    n = event.arg if event.arg_present else None
+    event.current_buffer.yank_last_arg(n)
+
+
+@register("yank-pop")
+def yank_pop(event: E) -> None:
+    """
+    Rotate the kill ring, and yank the new top. Only works following yank or
+    yank-pop.
+    """
+    buff = event.current_buffer
+    doc_before_paste = buff.document_before_paste
+    clipboard = event.app.clipboard
+
+    if doc_before_paste is not None:
+        buff.document = doc_before_paste
+        clipboard.rotate()
+        buff.paste_clipboard_data(clipboard.get_data(), paste_mode=PasteMode.EMACS)
+
+
+#
+# Completion.
+#
+
+
+@register("complete")
+def complete(event: E) -> None:
+    """
+    Attempt to perform completion.
+    """
+    display_completions_like_readline(event)
+
+
+@register("menu-complete")
+def menu_complete(event: E) -> None:
+    """
+    Generate completions, or go to the next completion. (This is the default
+    way of completing input in prompt_toolkit.)
+    """
+    generate_completions(event)
+
+
+@register("menu-complete-backward")
+def menu_complete_backward(event: E) -> None:
+    """
+    Move backward through the list of possible completions.
+    """
+    event.current_buffer.complete_previous()
+
+
+#
+# Keyboard macros.
+#
+
+
+@register("start-kbd-macro")
+def start_kbd_macro(event: E) -> None:
+    """
+    Begin saving the characters typed into the current keyboard macro.
+    """
+    event.app.emacs_state.start_macro()
+
+
+@register("end-kbd-macro")
+def end_kbd_macro(event: E) -> None:
+    """
+    Stop saving the characters typed into the current keyboard macro and save
+    the definition.
+    """
+    event.app.emacs_state.end_macro()
+
+
+@register("call-last-kbd-macro")
+@key_binding(record_in_macro=False)
+def call_last_kbd_macro(event: E) -> None:
+    """
+    Re-execute the last keyboard macro defined, by making the characters in the
+    macro appear as if typed at the keyboard.
+
+    Notice that we pass `record_in_macro=False`. This ensures that the 'c-x e'
+    key sequence doesn't appear in the recording itself. This function inserts
+    the body of the called macro back into the KeyProcessor, so these keys will
+    be added later on to the macro of their handlers have `record_in_macro=True`.
+    """
+    # Insert the macro.
+    macro = event.app.emacs_state.macro
+
+    if macro:
+        event.app.key_processor.feed_multiple(macro, first=True)
+
+
+@register("print-last-kbd-macro")
+def print_last_kbd_macro(event: E) -> None:
+    """
+    Print the last keyboard macro.
+    """
+    # TODO: Make the format suitable for the inputrc file.
+    def print_macro() -> None:
+        macro = event.app.emacs_state.macro
+        if macro:
+            for k in macro:
+                print(k)
+
+    from prompt_toolkit.application.run_in_terminal import run_in_terminal
+
+    run_in_terminal(print_macro)
+
+
+#
+# Miscellaneous Commands.
+#
+
+
+@register("undo")
+def undo(event: E) -> None:
+    """
+    Incremental undo.
+    """
+    event.current_buffer.undo()
+
+
+@register("insert-comment")
+def insert_comment(event: E) -> None:
+    """
+    Without numeric argument, comment all lines.
+    With numeric argument, uncomment all lines.
+    In any case accept the input.
+    """
+    buff = event.current_buffer
+
+    # Transform all lines.
+    if event.arg != 1:
+
+        def change(line: str) -> str:
+            return line[1:] if line.startswith("#") else line
+
+    else:
+
+        def change(line: str) -> str:
+            return "#" + line
+
+    buff.document = Document(
+        text="\n".join(map(change, buff.text.splitlines())), cursor_position=0
+    )
+
+    # Accept input.
+    buff.validate_and_handle()
+
+
+@register("vi-editing-mode")
+def vi_editing_mode(event: E) -> None:
+    """
+    Switch to Vi editing mode.
+    """
+    event.app.editing_mode = EditingMode.VI
+
+
+@register("emacs-editing-mode")
+def emacs_editing_mode(event: E) -> None:
+    """
+    Switch to Emacs editing mode.
+    """
+    event.app.editing_mode = EditingMode.EMACS
+
+
+@register("prefix-meta")
+def prefix_meta(event: E) -> None:
+    """
+    Metafy the next character typed. This is for keyboards without a meta key.
+
+    Sometimes people also want to bind other keys to Meta, e.g. 'jj'::
+
+        key_bindings.add_key_binding('j', 'j', filter=ViInsertMode())(prefix_meta)
+    """
+    # ('first' should be true, because we want to insert it at the current
+    # position in the queue.)
+    event.app.key_processor.feed(KeyPress(Keys.Escape), first=True)
+
+
+@register("operate-and-get-next")
+def operate_and_get_next(event: E) -> None:
+    """
+    Accept the current line for execution and fetch the next line relative to
+    the current line from the history for editing.
+    """
+    buff = event.current_buffer
+    new_index = buff.working_index + 1
+
+    # Accept the current input. (This will also redraw the interface in the
+    # 'done' state.)
+    buff.validate_and_handle()
+
+    # Set the new index at the start of the next run.
+    def set_working_index() -> None:
+        if new_index < len(buff._working_lines):
+            buff.working_index = new_index
+
+    event.app.pre_run_callables.append(set_working_index)
+
+
+@register("edit-and-execute-command")
+def edit_and_execute(event: E) -> None:
+    """
+    Invoke an editor on the current command line, and accept the result.
+    """
+    buff = event.current_buffer
+    buff.open_in_editor(validate_and_handle=True)
diff --git a/src/prompt_toolkit/key_binding/bindings/open_in_editor.py b/src/prompt_toolkit/key_binding/bindings/open_in_editor.py
new file mode 100644
index 0000000..f8699f4
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/open_in_editor.py
@@ -0,0 +1,49 @@
+"""
+Open in editor key bindings.
+"""
+from prompt_toolkit.filters import emacs_mode, has_selection, vi_navigation_mode
+
+from ..key_bindings import KeyBindings, KeyBindingsBase, merge_key_bindings
+from .named_commands import get_by_name
+
+__all__ = [
+    "load_open_in_editor_bindings",
+    "load_emacs_open_in_editor_bindings",
+    "load_vi_open_in_editor_bindings",
+]
+
+
+def load_open_in_editor_bindings() -> KeyBindingsBase:
+    """
+    Load both the Vi and emacs key bindings for handling edit-and-execute-command.
+    """
+    return merge_key_bindings(
+        [
+            load_emacs_open_in_editor_bindings(),
+            load_vi_open_in_editor_bindings(),
+        ]
+    )
+
+
+def load_emacs_open_in_editor_bindings() -> KeyBindings:
+    """
+    Pressing C-X C-E will open the buffer in an external editor.
+    """
+    key_bindings = KeyBindings()
+
+    key_bindings.add("c-x", "c-e", filter=emacs_mode & ~has_selection)(
+        get_by_name("edit-and-execute-command")
+    )
+
+    return key_bindings
+
+
+def load_vi_open_in_editor_bindings() -> KeyBindings:
+    """
+    Pressing 'v' in navigation mode will open the buffer in an external editor.
+    """
+    key_bindings = KeyBindings()
+    key_bindings.add("v", filter=vi_navigation_mode)(
+        get_by_name("edit-and-execute-command")
+    )
+    return key_bindings
diff --git a/src/prompt_toolkit/key_binding/bindings/page_navigation.py b/src/prompt_toolkit/key_binding/bindings/page_navigation.py
new file mode 100644
index 0000000..4d531c0
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/page_navigation.py
@@ -0,0 +1,82 @@
+"""
+Key bindings for extra page navigation: bindings for up/down scrolling through
+long pages, like in Emacs or Vi.
+"""
+from prompt_toolkit.filters import buffer_has_focus, emacs_mode, vi_mode
+from prompt_toolkit.key_binding.key_bindings import (
+    ConditionalKeyBindings,
+    KeyBindings,
+    KeyBindingsBase,
+    merge_key_bindings,
+)
+
+from .scroll import (
+    scroll_backward,
+    scroll_forward,
+    scroll_half_page_down,
+    scroll_half_page_up,
+    scroll_one_line_down,
+    scroll_one_line_up,
+    scroll_page_down,
+    scroll_page_up,
+)
+
+__all__ = [
+    "load_page_navigation_bindings",
+    "load_emacs_page_navigation_bindings",
+    "load_vi_page_navigation_bindings",
+]
+
+
+def load_page_navigation_bindings() -> KeyBindingsBase:
+    """
+    Load both the Vi and Emacs bindings for page navigation.
+    """
+    # Only enable when a `Buffer` is focused, otherwise, we would catch keys
+    # when another widget is focused (like for instance `c-d` in a
+    # ptterm.Terminal).
+    return ConditionalKeyBindings(
+        merge_key_bindings(
+            [
+                load_emacs_page_navigation_bindings(),
+                load_vi_page_navigation_bindings(),
+            ]
+        ),
+        buffer_has_focus,
+    )
+
+
+def load_emacs_page_navigation_bindings() -> KeyBindingsBase:
+    """
+    Key bindings, for scrolling up and down through pages.
+    This are separate bindings, because GNU readline doesn't have them.
+    """
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+
+    handle("c-v")(scroll_page_down)
+    handle("pagedown")(scroll_page_down)
+    handle("escape", "v")(scroll_page_up)
+    handle("pageup")(scroll_page_up)
+
+    return ConditionalKeyBindings(key_bindings, emacs_mode)
+
+
+def load_vi_page_navigation_bindings() -> KeyBindingsBase:
+    """
+    Key bindings, for scrolling up and down through pages.
+    This are separate bindings, because GNU readline doesn't have them.
+    """
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+
+    handle("c-f")(scroll_forward)
+    handle("c-b")(scroll_backward)
+    handle("c-d")(scroll_half_page_down)
+    handle("c-u")(scroll_half_page_up)
+    handle("c-e")(scroll_one_line_down)
+    handle("c-y")(scroll_one_line_up)
+    handle("pagedown")(scroll_page_down)
+    handle("pageup")(scroll_page_up)
+
+    return ConditionalKeyBindings(key_bindings, vi_mode)
diff --git a/src/prompt_toolkit/key_binding/bindings/scroll.py b/src/prompt_toolkit/key_binding/bindings/scroll.py
new file mode 100644
index 0000000..4a43ff5
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/scroll.py
@@ -0,0 +1,187 @@
+"""
+Key bindings, for scrolling up and down through pages.
+
+This are separate bindings, because GNU readline doesn't have them, but
+they are very useful for navigating through long multiline buffers, like in
+Vi, Emacs, etc...
+"""
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+
+__all__ = [
+    "scroll_forward",
+    "scroll_backward",
+    "scroll_half_page_up",
+    "scroll_half_page_down",
+    "scroll_one_line_up",
+    "scroll_one_line_down",
+]
+
+E = KeyPressEvent
+
+
+def scroll_forward(event: E, half: bool = False) -> None:
+    """
+    Scroll window down.
+    """
+    w = event.app.layout.current_window
+    b = event.app.current_buffer
+
+    if w and w.render_info:
+        info = w.render_info
+        ui_content = info.ui_content
+
+        # Height to scroll.
+        scroll_height = info.window_height
+        if half:
+            scroll_height //= 2
+
+        # Calculate how many lines is equivalent to that vertical space.
+        y = b.document.cursor_position_row + 1
+        height = 0
+        while y < ui_content.line_count:
+            line_height = info.get_height_for_line(y)
+
+            if height + line_height < scroll_height:
+                height += line_height
+                y += 1
+            else:
+                break
+
+        b.cursor_position = b.document.translate_row_col_to_index(y, 0)
+
+
+def scroll_backward(event: E, half: bool = False) -> None:
+    """
+    Scroll window up.
+    """
+    w = event.app.layout.current_window
+    b = event.app.current_buffer
+
+    if w and w.render_info:
+        info = w.render_info
+
+        # Height to scroll.
+        scroll_height = info.window_height
+        if half:
+            scroll_height //= 2
+
+        # Calculate how many lines is equivalent to that vertical space.
+        y = max(0, b.document.cursor_position_row - 1)
+        height = 0
+        while y > 0:
+            line_height = info.get_height_for_line(y)
+
+            if height + line_height < scroll_height:
+                height += line_height
+                y -= 1
+            else:
+                break
+
+        b.cursor_position = b.document.translate_row_col_to_index(y, 0)
+
+
+def scroll_half_page_down(event: E) -> None:
+    """
+    Same as ControlF, but only scroll half a page.
+    """
+    scroll_forward(event, half=True)
+
+
+def scroll_half_page_up(event: E) -> None:
+    """
+    Same as ControlB, but only scroll half a page.
+    """
+    scroll_backward(event, half=True)
+
+
+def scroll_one_line_down(event: E) -> None:
+    """
+    scroll_offset += 1
+    """
+    w = event.app.layout.current_window
+    b = event.app.current_buffer
+
+    if w:
+        # When the cursor is at the top, move to the next line. (Otherwise, only scroll.)
+        if w.render_info:
+            info = w.render_info
+
+            if w.vertical_scroll < info.content_height - info.window_height:
+                if info.cursor_position.y <= info.configured_scroll_offsets.top:
+                    b.cursor_position += b.document.get_cursor_down_position()
+
+                w.vertical_scroll += 1
+
+
+def scroll_one_line_up(event: E) -> None:
+    """
+    scroll_offset -= 1
+    """
+    w = event.app.layout.current_window
+    b = event.app.current_buffer
+
+    if w:
+        # When the cursor is at the bottom, move to the previous line. (Otherwise, only scroll.)
+        if w.render_info:
+            info = w.render_info
+
+            if w.vertical_scroll > 0:
+                first_line_height = info.get_height_for_line(info.first_visible_line())
+
+                cursor_up = info.cursor_position.y - (
+                    info.window_height
+                    - 1
+                    - first_line_height
+                    - info.configured_scroll_offsets.bottom
+                )
+
+                # Move cursor up, as many steps as the height of the first line.
+                # TODO: not entirely correct yet, in case of line wrapping and many long lines.
+                for _ in range(max(0, cursor_up)):
+                    b.cursor_position += b.document.get_cursor_up_position()
+
+                # Scroll window
+                w.vertical_scroll -= 1
+
+
+def scroll_page_down(event: E) -> None:
+    """
+    Scroll page down. (Prefer the cursor at the top of the page, after scrolling.)
+    """
+    w = event.app.layout.current_window
+    b = event.app.current_buffer
+
+    if w and w.render_info:
+        # Scroll down one page.
+        line_index = max(w.render_info.last_visible_line(), w.vertical_scroll + 1)
+        w.vertical_scroll = line_index
+
+        b.cursor_position = b.document.translate_row_col_to_index(line_index, 0)
+        b.cursor_position += b.document.get_start_of_line_position(
+            after_whitespace=True
+        )
+
+
+def scroll_page_up(event: E) -> None:
+    """
+    Scroll page up. (Prefer the cursor at the bottom of the page, after scrolling.)
+    """
+    w = event.app.layout.current_window
+    b = event.app.current_buffer
+
+    if w and w.render_info:
+        # Put cursor at the first visible line. (But make sure that the cursor
+        # moves at least one line up.)
+        line_index = max(
+            0,
+            min(w.render_info.first_visible_line(), b.document.cursor_position_row - 1),
+        )
+
+        b.cursor_position = b.document.translate_row_col_to_index(line_index, 0)
+        b.cursor_position += b.document.get_start_of_line_position(
+            after_whitespace=True
+        )
+
+        # Set the scroll offset. We can safely set it to zero; the Window will
+        # make sure that it scrolls at least until the cursor becomes visible.
+        w.vertical_scroll = 0
diff --git a/src/prompt_toolkit/key_binding/bindings/search.py b/src/prompt_toolkit/key_binding/bindings/search.py
new file mode 100644
index 0000000..06a047e
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/search.py
@@ -0,0 +1,93 @@
+"""
+Search related key bindings.
+"""
+from prompt_toolkit import search
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.filters import Condition, control_is_searchable, is_searching
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+
+from ..key_bindings import key_binding
+
+__all__ = [
+    "abort_search",
+    "accept_search",
+    "start_reverse_incremental_search",
+    "start_forward_incremental_search",
+    "reverse_incremental_search",
+    "forward_incremental_search",
+    "accept_search_and_accept_input",
+]
+
+E = KeyPressEvent
+
+
+@key_binding(filter=is_searching)
+def abort_search(event: E) -> None:
+    """
+    Abort an incremental search and restore the original
+    line.
+    (Usually bound to ControlG/ControlC.)
+    """
+    search.stop_search()
+
+
+@key_binding(filter=is_searching)
+def accept_search(event: E) -> None:
+    """
+    When enter pressed in isearch, quit isearch mode. (Multiline
+    isearch would be too complicated.)
+    (Usually bound to Enter.)
+    """
+    search.accept_search()
+
+
+@key_binding(filter=control_is_searchable)
+def start_reverse_incremental_search(event: E) -> None:
+    """
+    Enter reverse incremental search.
+    (Usually ControlR.)
+    """
+    search.start_search(direction=search.SearchDirection.BACKWARD)
+
+
+@key_binding(filter=control_is_searchable)
+def start_forward_incremental_search(event: E) -> None:
+    """
+    Enter forward incremental search.
+    (Usually ControlS.)
+    """
+    search.start_search(direction=search.SearchDirection.FORWARD)
+
+
+@key_binding(filter=is_searching)
+def reverse_incremental_search(event: E) -> None:
+    """
+    Apply reverse incremental search, but keep search buffer focused.
+    """
+    search.do_incremental_search(search.SearchDirection.BACKWARD, count=event.arg)
+
+
+@key_binding(filter=is_searching)
+def forward_incremental_search(event: E) -> None:
+    """
+    Apply forward incremental search, but keep search buffer focused.
+    """
+    search.do_incremental_search(search.SearchDirection.FORWARD, count=event.arg)
+
+
+@Condition
+def _previous_buffer_is_returnable() -> bool:
+    """
+    True if the previously focused buffer has a return handler.
+    """
+    prev_control = get_app().layout.search_target_buffer_control
+    return bool(prev_control and prev_control.buffer.is_returnable)
+
+
+@key_binding(filter=is_searching & _previous_buffer_is_returnable)
+def accept_search_and_accept_input(event: E) -> None:
+    """
+    Accept the search operation first, then accept the input.
+    """
+    search.accept_search()
+    event.current_buffer.validate_and_handle()
diff --git a/src/prompt_toolkit/key_binding/bindings/vi.py b/src/prompt_toolkit/key_binding/bindings/vi.py
new file mode 100644
index 0000000..9cb075c
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/bindings/vi.py
@@ -0,0 +1,2221 @@
+# pylint: disable=function-redefined
+import codecs
+import string
+from enum import Enum
+from itertools import accumulate
+from typing import Callable, Iterable, List, Optional, Tuple, TypeVar, Union
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.buffer import Buffer, indent, reshape_text, unindent
+from prompt_toolkit.clipboard import ClipboardData
+from prompt_toolkit.document import Document
+from prompt_toolkit.filters import (
+    Always,
+    Condition,
+    Filter,
+    has_arg,
+    is_read_only,
+    is_searching,
+)
+from prompt_toolkit.filters.app import (
+    in_paste_mode,
+    is_multiline,
+    vi_digraph_mode,
+    vi_insert_mode,
+    vi_insert_multiple_mode,
+    vi_mode,
+    vi_navigation_mode,
+    vi_recording_macro,
+    vi_replace_mode,
+    vi_replace_single_mode,
+    vi_search_direction_reversed,
+    vi_selection_mode,
+    vi_waiting_for_text_object_mode,
+)
+from prompt_toolkit.input.vt100_parser import Vt100Parser
+from prompt_toolkit.key_binding.digraphs import DIGRAPHS
+from prompt_toolkit.key_binding.key_processor import KeyPress, KeyPressEvent
+from prompt_toolkit.key_binding.vi_state import CharacterFind, InputMode
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.search import SearchDirection
+from prompt_toolkit.selection import PasteMode, SelectionState, SelectionType
+
+from ..key_bindings import ConditionalKeyBindings, KeyBindings, KeyBindingsBase
+from .named_commands import get_by_name
+
+__all__ = [
+    "load_vi_bindings",
+    "load_vi_search_bindings",
+]
+
+E = KeyPressEvent
+
+ascii_lowercase = string.ascii_lowercase
+
+vi_register_names = ascii_lowercase + "0123456789"
+
+
+class TextObjectType(Enum):
+    EXCLUSIVE = "EXCLUSIVE"
+    INCLUSIVE = "INCLUSIVE"
+    LINEWISE = "LINEWISE"
+    BLOCK = "BLOCK"
+
+
+class TextObject:
+    """
+    Return struct for functions wrapped in ``text_object``.
+    Both `start` and `end` are relative to the current cursor position.
+    """
+
+    def __init__(
+        self, start: int, end: int = 0, type: TextObjectType = TextObjectType.EXCLUSIVE
+    ):
+
+        self.start = start
+        self.end = end
+        self.type = type
+
+    @property
+    def selection_type(self) -> SelectionType:
+        if self.type == TextObjectType.LINEWISE:
+            return SelectionType.LINES
+        if self.type == TextObjectType.BLOCK:
+            return SelectionType.BLOCK
+        else:
+            return SelectionType.CHARACTERS
+
+    def sorted(self) -> Tuple[int, int]:
+        """
+        Return a (start, end) tuple where start <= end.
+        """
+        if self.start < self.end:
+            return self.start, self.end
+        else:
+            return self.end, self.start
+
+    def operator_range(self, document: Document) -> Tuple[int, int]:
+        """
+        Return a (start, end) tuple with start <= end that indicates the range
+        operators should operate on.
+        `buffer` is used to get start and end of line positions.
+
+        This should return something that can be used in a slice, so the `end`
+        position is *not* included.
+        """
+        start, end = self.sorted()
+        doc = document
+
+        if (
+            self.type == TextObjectType.EXCLUSIVE
+            and doc.translate_index_to_position(end + doc.cursor_position)[1] == 0
+        ):
+            # If the motion is exclusive and the end of motion is on the first
+            # column, the end position becomes end of previous line.
+            end -= 1
+        if self.type == TextObjectType.INCLUSIVE:
+            end += 1
+        if self.type == TextObjectType.LINEWISE:
+            # Select whole lines
+            row, col = doc.translate_index_to_position(start + doc.cursor_position)
+            start = doc.translate_row_col_to_index(row, 0) - doc.cursor_position
+            row, col = doc.translate_index_to_position(end + doc.cursor_position)
+            end = (
+                doc.translate_row_col_to_index(row, len(doc.lines[row]))
+                - doc.cursor_position
+            )
+        return start, end
+
+    def get_line_numbers(self, buffer: Buffer) -> Tuple[int, int]:
+        """
+        Return a (start_line, end_line) pair.
+        """
+        # Get absolute cursor positions from the text object.
+        from_, to = self.operator_range(buffer.document)
+        from_ += buffer.cursor_position
+        to += buffer.cursor_position
+
+        # Take the start of the lines.
+        from_, _ = buffer.document.translate_index_to_position(from_)
+        to, _ = buffer.document.translate_index_to_position(to)
+
+        return from_, to
+
+    def cut(self, buffer: Buffer) -> Tuple[Document, ClipboardData]:
+        """
+        Turn text object into `ClipboardData` instance.
+        """
+        from_, to = self.operator_range(buffer.document)
+
+        from_ += buffer.cursor_position
+        to += buffer.cursor_position
+
+        # For Vi mode, the SelectionState does include the upper position,
+        # while `self.operator_range` does not. So, go one to the left, unless
+        # we're in the line mode, then we don't want to risk going to the
+        # previous line, and missing one line in the selection.
+        if self.type != TextObjectType.LINEWISE:
+            to -= 1
+
+        document = Document(
+            buffer.text,
+            to,
+            SelectionState(original_cursor_position=from_, type=self.selection_type),
+        )
+
+        new_document, clipboard_data = document.cut_selection()
+        return new_document, clipboard_data
+
+
+# Typevar for any text object function:
+TextObjectFunction = Callable[[E], TextObject]
+_TOF = TypeVar("_TOF", bound=TextObjectFunction)
+
+
+def create_text_object_decorator(
+    key_bindings: KeyBindings,
+) -> Callable[..., Callable[[_TOF], _TOF]]:
+    """
+    Create a decorator that can be used to register Vi text object implementations.
+    """
+
+    def text_object_decorator(
+        *keys: Union[Keys, str],
+        filter: Filter = Always(),
+        no_move_handler: bool = False,
+        no_selection_handler: bool = False,
+        eager: bool = False,
+    ) -> Callable[[_TOF], _TOF]:
+        """
+        Register a text object function.
+
+        Usage::
+
+            @text_object('w', filter=..., no_move_handler=False)
+            def handler(event):
+                # Return a text object for this key.
+                return TextObject(...)
+
+        :param no_move_handler: Disable the move handler in navigation mode.
+            (It's still active in selection mode.)
+        """
+
+        def decorator(text_object_func: _TOF) -> _TOF:
+            @key_bindings.add(
+                *keys, filter=vi_waiting_for_text_object_mode & filter, eager=eager
+            )
+            def _apply_operator_to_text_object(event: E) -> None:
+                # Arguments are multiplied.
+                vi_state = event.app.vi_state
+                event._arg = str((vi_state.operator_arg or 1) * (event.arg or 1))
+
+                # Call the text object handler.
+                text_obj = text_object_func(event)
+
+                # Get the operator function.
+                # (Should never be None here, given the
+                # `vi_waiting_for_text_object_mode` filter state.)
+                operator_func = vi_state.operator_func
+
+                if text_obj is not None and operator_func is not None:
+                    # Call the operator function with the text object.
+                    operator_func(event, text_obj)
+
+                # Clear operator.
+                event.app.vi_state.operator_func = None
+                event.app.vi_state.operator_arg = None
+
+            # Register a move operation. (Doesn't need an operator.)
+            if not no_move_handler:
+
+                @key_bindings.add(
+                    *keys,
+                    filter=~vi_waiting_for_text_object_mode
+                    & filter
+                    & vi_navigation_mode,
+                    eager=eager,
+                )
+                def _move_in_navigation_mode(event: E) -> None:
+                    """
+                    Move handler for navigation mode.
+                    """
+                    text_object = text_object_func(event)
+                    event.current_buffer.cursor_position += text_object.start
+
+            # Register a move selection operation.
+            if not no_selection_handler:
+
+                @key_bindings.add(
+                    *keys,
+                    filter=~vi_waiting_for_text_object_mode
+                    & filter
+                    & vi_selection_mode,
+                    eager=eager,
+                )
+                def _move_in_selection_mode(event: E) -> None:
+                    """
+                    Move handler for selection mode.
+                    """
+                    text_object = text_object_func(event)
+                    buff = event.current_buffer
+                    selection_state = buff.selection_state
+
+                    if selection_state is None:
+                        return  # Should not happen, because of the `vi_selection_mode` filter.
+
+                    # When the text object has both a start and end position, like 'i(' or 'iw',
+                    # Turn this into a selection, otherwise the cursor.
+                    if text_object.end:
+                        # Take selection positions from text object.
+                        start, end = text_object.operator_range(buff.document)
+                        start += buff.cursor_position
+                        end += buff.cursor_position
+
+                        selection_state.original_cursor_position = start
+                        buff.cursor_position = end
+
+                        # Take selection type from text object.
+                        if text_object.type == TextObjectType.LINEWISE:
+                            selection_state.type = SelectionType.LINES
+                        else:
+                            selection_state.type = SelectionType.CHARACTERS
+                    else:
+                        event.current_buffer.cursor_position += text_object.start
+
+            # Make it possible to chain @text_object decorators.
+            return text_object_func
+
+        return decorator
+
+    return text_object_decorator
+
+
+# Typevar for any operator function:
+OperatorFunction = Callable[[E, TextObject], None]
+_OF = TypeVar("_OF", bound=OperatorFunction)
+
+
+def create_operator_decorator(
+    key_bindings: KeyBindings,
+) -> Callable[..., Callable[[_OF], _OF]]:
+    """
+    Create a decorator that can be used for registering Vi operators.
+    """
+
+    def operator_decorator(
+        *keys: Union[Keys, str], filter: Filter = Always(), eager: bool = False
+    ) -> Callable[[_OF], _OF]:
+        """
+        Register a Vi operator.
+
+        Usage::
+
+            @operator('d', filter=...)
+            def handler(event, text_object):
+                # Do something with the text object here.
+        """
+
+        def decorator(operator_func: _OF) -> _OF:
+            @key_bindings.add(
+                *keys,
+                filter=~vi_waiting_for_text_object_mode & filter & vi_navigation_mode,
+                eager=eager,
+            )
+            def _operator_in_navigation(event: E) -> None:
+                """
+                Handle operator in navigation mode.
+                """
+                # When this key binding is matched, only set the operator
+                # function in the ViState. We should execute it after a text
+                # object has been received.
+                event.app.vi_state.operator_func = operator_func
+                event.app.vi_state.operator_arg = event.arg
+
+            @key_bindings.add(
+                *keys,
+                filter=~vi_waiting_for_text_object_mode & filter & vi_selection_mode,
+                eager=eager,
+            )
+            def _operator_in_selection(event: E) -> None:
+                """
+                Handle operator in selection mode.
+                """
+                buff = event.current_buffer
+                selection_state = buff.selection_state
+
+                if selection_state is not None:
+                    # Create text object from selection.
+                    if selection_state.type == SelectionType.LINES:
+                        text_obj_type = TextObjectType.LINEWISE
+                    elif selection_state.type == SelectionType.BLOCK:
+                        text_obj_type = TextObjectType.BLOCK
+                    else:
+                        text_obj_type = TextObjectType.INCLUSIVE
+
+                    text_object = TextObject(
+                        selection_state.original_cursor_position - buff.cursor_position,
+                        type=text_obj_type,
+                    )
+
+                    # Execute operator.
+                    operator_func(event, text_object)
+
+                    # Quit selection mode.
+                    buff.selection_state = None
+
+            return operator_func
+
+        return decorator
+
+    return operator_decorator
+
+
+def load_vi_bindings() -> KeyBindingsBase:
+    """
+    Vi extensions.
+
+    # Overview of Readline Vi commands:
+    # http://www.catonmat.net/download/bash-vi-editing-mode-cheat-sheet.pdf
+    """
+    # Note: Some key bindings have the "~IsReadOnly()" filter added. This
+    #       prevents the handler to be executed when the focus is on a
+    #       read-only buffer.
+    #       This is however only required for those that change the ViState to
+    #       INSERT mode. The `Buffer` class itself throws the
+    #       `EditReadOnlyBuffer` exception for any text operations which is
+    #       handled correctly. There is no need to add "~IsReadOnly" to all key
+    #       bindings that do text manipulation.
+
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+
+    # (Note: Always take the navigation bindings in read-only mode, even when
+    #  ViState says different.)
+
+    TransformFunction = Tuple[Tuple[str, ...], Filter, Callable[[str], str]]
+
+    vi_transform_functions: List[TransformFunction] = [
+        # Rot 13 transformation
+        (
+            ("g", "?"),
+            Always(),
+            lambda string: codecs.encode(string, "rot_13"),
+        ),
+        # To lowercase
+        (("g", "u"), Always(), lambda string: string.lower()),
+        # To uppercase.
+        (("g", "U"), Always(), lambda string: string.upper()),
+        # Swap case.
+        (("g", "~"), Always(), lambda string: string.swapcase()),
+        (
+            ("~",),
+            Condition(lambda: get_app().vi_state.tilde_operator),
+            lambda string: string.swapcase(),
+        ),
+    ]
+
+    # Insert a character literally (quoted insert).
+    handle("c-v", filter=vi_insert_mode)(get_by_name("quoted-insert"))
+
+    @handle("escape")
+    def _back_to_navigation(event: E) -> None:
+        """
+        Escape goes to vi navigation mode.
+        """
+        buffer = event.current_buffer
+        vi_state = event.app.vi_state
+
+        if vi_state.input_mode in (InputMode.INSERT, InputMode.REPLACE):
+            buffer.cursor_position += buffer.document.get_cursor_left_position()
+
+        vi_state.input_mode = InputMode.NAVIGATION
+
+        if bool(buffer.selection_state):
+            buffer.exit_selection()
+
+    @handle("k", filter=vi_selection_mode)
+    def _up_in_selection(event: E) -> None:
+        """
+        Arrow up in selection mode.
+        """
+        event.current_buffer.cursor_up(count=event.arg)
+
+    @handle("j", filter=vi_selection_mode)
+    def _down_in_selection(event: E) -> None:
+        """
+        Arrow down in selection mode.
+        """
+        event.current_buffer.cursor_down(count=event.arg)
+
+    @handle("up", filter=vi_navigation_mode)
+    @handle("c-p", filter=vi_navigation_mode)
+    def _up_in_navigation(event: E) -> None:
+        """
+        Arrow up and ControlP in navigation mode go up.
+        """
+        event.current_buffer.auto_up(count=event.arg)
+
+    @handle("k", filter=vi_navigation_mode)
+    def _go_up(event: E) -> None:
+        """
+        Go up, but if we enter a new history entry, move to the start of the
+        line.
+        """
+        event.current_buffer.auto_up(
+            count=event.arg, go_to_start_of_line_if_history_changes=True
+        )
+
+    @handle("down", filter=vi_navigation_mode)
+    @handle("c-n", filter=vi_navigation_mode)
+    def _go_down(event: E) -> None:
+        """
+        Arrow down and Control-N in navigation mode.
+        """
+        event.current_buffer.auto_down(count=event.arg)
+
+    @handle("j", filter=vi_navigation_mode)
+    def _go_down2(event: E) -> None:
+        """
+        Go down, but if we enter a new history entry, go to the start of the line.
+        """
+        event.current_buffer.auto_down(
+            count=event.arg, go_to_start_of_line_if_history_changes=True
+        )
+
+    @handle("backspace", filter=vi_navigation_mode)
+    def _go_left(event: E) -> None:
+        """
+        In navigation-mode, move cursor.
+        """
+        event.current_buffer.cursor_position += (
+            event.current_buffer.document.get_cursor_left_position(count=event.arg)
+        )
+
+    @handle("c-n", filter=vi_insert_mode)
+    def _complete_next(event: E) -> None:
+        b = event.current_buffer
+
+        if b.complete_state:
+            b.complete_next()
+        else:
+            b.start_completion(select_first=True)
+
+    @handle("c-p", filter=vi_insert_mode)
+    def _complete_prev(event: E) -> None:
+        """
+        Control-P: To previous completion.
+        """
+        b = event.current_buffer
+
+        if b.complete_state:
+            b.complete_previous()
+        else:
+            b.start_completion(select_last=True)
+
+    @handle("c-g", filter=vi_insert_mode)
+    @handle("c-y", filter=vi_insert_mode)
+    def _accept_completion(event: E) -> None:
+        """
+        Accept current completion.
+        """
+        event.current_buffer.complete_state = None
+
+    @handle("c-e", filter=vi_insert_mode)
+    def _cancel_completion(event: E) -> None:
+        """
+        Cancel completion. Go back to originally typed text.
+        """
+        event.current_buffer.cancel_completion()
+
+    @Condition
+    def is_returnable() -> bool:
+        return get_app().current_buffer.is_returnable
+
+    # In navigation mode, pressing enter will always return the input.
+    handle("enter", filter=vi_navigation_mode & is_returnable)(
+        get_by_name("accept-line")
+    )
+
+    # In insert mode, also accept input when enter is pressed, and the buffer
+    # has been marked as single line.
+    handle("enter", filter=is_returnable & ~is_multiline)(get_by_name("accept-line"))
+
+    @handle("enter", filter=~is_returnable & vi_navigation_mode)
+    def _start_of_next_line(event: E) -> None:
+        """
+        Go to the beginning of next line.
+        """
+        b = event.current_buffer
+        b.cursor_down(count=event.arg)
+        b.cursor_position += b.document.get_start_of_line_position(
+            after_whitespace=True
+        )
+
+    # ** In navigation mode **
+
+    # List of navigation commands: http://hea-www.harvard.edu/~fine/Tech/vi.html
+
+    @handle("insert", filter=vi_navigation_mode)
+    def _insert_mode(event: E) -> None:
+        """
+        Pressing the Insert key.
+        """
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("insert", filter=vi_insert_mode)
+    def _navigation_mode(event: E) -> None:
+        """
+        Pressing the Insert key.
+        """
+        event.app.vi_state.input_mode = InputMode.NAVIGATION
+
+    @handle("a", filter=vi_navigation_mode & ~is_read_only)
+    # ~IsReadOnly, because we want to stay in navigation mode for
+    # read-only buffers.
+    def _a(event: E) -> None:
+        event.current_buffer.cursor_position += (
+            event.current_buffer.document.get_cursor_right_position()
+        )
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("A", filter=vi_navigation_mode & ~is_read_only)
+    def _A(event: E) -> None:
+        event.current_buffer.cursor_position += (
+            event.current_buffer.document.get_end_of_line_position()
+        )
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("C", filter=vi_navigation_mode & ~is_read_only)
+    def _change_until_end_of_line(event: E) -> None:
+        """
+        Change to end of line.
+        Same as 'c$' (which is implemented elsewhere.)
+        """
+        buffer = event.current_buffer
+
+        deleted = buffer.delete(count=buffer.document.get_end_of_line_position())
+        event.app.clipboard.set_text(deleted)
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("c", "c", filter=vi_navigation_mode & ~is_read_only)
+    @handle("S", filter=vi_navigation_mode & ~is_read_only)
+    def _change_current_line(event: E) -> None:  # TODO: implement 'arg'
+        """
+        Change current line
+        """
+        buffer = event.current_buffer
+
+        # We copy the whole line.
+        data = ClipboardData(buffer.document.current_line, SelectionType.LINES)
+        event.app.clipboard.set_data(data)
+
+        # But we delete after the whitespace
+        buffer.cursor_position += buffer.document.get_start_of_line_position(
+            after_whitespace=True
+        )
+        buffer.delete(count=buffer.document.get_end_of_line_position())
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("D", filter=vi_navigation_mode)
+    def _delete_until_end_of_line(event: E) -> None:
+        """
+        Delete from cursor position until the end of the line.
+        """
+        buffer = event.current_buffer
+        deleted = buffer.delete(count=buffer.document.get_end_of_line_position())
+        event.app.clipboard.set_text(deleted)
+
+    @handle("d", "d", filter=vi_navigation_mode)
+    def _delete_line(event: E) -> None:
+        """
+        Delete line. (Or the following 'n' lines.)
+        """
+        buffer = event.current_buffer
+
+        # Split string in before/deleted/after text.
+        lines = buffer.document.lines
+
+        before = "\n".join(lines[: buffer.document.cursor_position_row])
+        deleted = "\n".join(
+            lines[
+                buffer.document.cursor_position_row : buffer.document.cursor_position_row
+                + event.arg
+            ]
+        )
+        after = "\n".join(lines[buffer.document.cursor_position_row + event.arg :])
+
+        # Set new text.
+        if before and after:
+            before = before + "\n"
+
+        # Set text and cursor position.
+        buffer.document = Document(
+            text=before + after,
+            # Cursor At the start of the first 'after' line, after the leading whitespace.
+            cursor_position=len(before) + len(after) - len(after.lstrip(" ")),
+        )
+
+        # Set clipboard data
+        event.app.clipboard.set_data(ClipboardData(deleted, SelectionType.LINES))
+
+    @handle("x", filter=vi_selection_mode)
+    def _cut(event: E) -> None:
+        """
+        Cut selection.
+        ('x' is not an operator.)
+        """
+        clipboard_data = event.current_buffer.cut_selection()
+        event.app.clipboard.set_data(clipboard_data)
+
+    @handle("i", filter=vi_navigation_mode & ~is_read_only)
+    def _i(event: E) -> None:
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("I", filter=vi_navigation_mode & ~is_read_only)
+    def _I(event: E) -> None:
+        event.app.vi_state.input_mode = InputMode.INSERT
+        event.current_buffer.cursor_position += (
+            event.current_buffer.document.get_start_of_line_position(
+                after_whitespace=True
+            )
+        )
+
+    @Condition
+    def in_block_selection() -> bool:
+        buff = get_app().current_buffer
+        return bool(
+            buff.selection_state and buff.selection_state.type == SelectionType.BLOCK
+        )
+
+    @handle("I", filter=in_block_selection & ~is_read_only)
+    def insert_in_block_selection(event: E, after: bool = False) -> None:
+        """
+        Insert in block selection mode.
+        """
+        buff = event.current_buffer
+
+        # Store all cursor positions.
+        positions = []
+
+        if after:
+
+            def get_pos(from_to: Tuple[int, int]) -> int:
+                return from_to[1]
+
+        else:
+
+            def get_pos(from_to: Tuple[int, int]) -> int:
+                return from_to[0]
+
+        for i, from_to in enumerate(buff.document.selection_ranges()):
+            positions.append(get_pos(from_to))
+            if i == 0:
+                buff.cursor_position = get_pos(from_to)
+
+        buff.multiple_cursor_positions = positions
+
+        # Go to 'INSERT_MULTIPLE' mode.
+        event.app.vi_state.input_mode = InputMode.INSERT_MULTIPLE
+        buff.exit_selection()
+
+    @handle("A", filter=in_block_selection & ~is_read_only)
+    def _append_after_block(event: E) -> None:
+        insert_in_block_selection(event, after=True)
+
+    @handle("J", filter=vi_navigation_mode & ~is_read_only)
+    def _join(event: E) -> None:
+        """
+        Join lines.
+        """
+        for i in range(event.arg):
+            event.current_buffer.join_next_line()
+
+    @handle("g", "J", filter=vi_navigation_mode & ~is_read_only)
+    def _join_nospace(event: E) -> None:
+        """
+        Join lines without space.
+        """
+        for i in range(event.arg):
+            event.current_buffer.join_next_line(separator="")
+
+    @handle("J", filter=vi_selection_mode & ~is_read_only)
+    def _join_selection(event: E) -> None:
+        """
+        Join selected lines.
+        """
+        event.current_buffer.join_selected_lines()
+
+    @handle("g", "J", filter=vi_selection_mode & ~is_read_only)
+    def _join_selection_nospace(event: E) -> None:
+        """
+        Join selected lines without space.
+        """
+        event.current_buffer.join_selected_lines(separator="")
+
+    @handle("p", filter=vi_navigation_mode)
+    def _paste(event: E) -> None:
+        """
+        Paste after
+        """
+        event.current_buffer.paste_clipboard_data(
+            event.app.clipboard.get_data(),
+            count=event.arg,
+            paste_mode=PasteMode.VI_AFTER,
+        )
+
+    @handle("P", filter=vi_navigation_mode)
+    def _paste_before(event: E) -> None:
+        """
+        Paste before
+        """
+        event.current_buffer.paste_clipboard_data(
+            event.app.clipboard.get_data(),
+            count=event.arg,
+            paste_mode=PasteMode.VI_BEFORE,
+        )
+
+    @handle('"', Keys.Any, "p", filter=vi_navigation_mode)
+    def _paste_register(event: E) -> None:
+        """
+        Paste from named register.
+        """
+        c = event.key_sequence[1].data
+        if c in vi_register_names:
+            data = event.app.vi_state.named_registers.get(c)
+            if data:
+                event.current_buffer.paste_clipboard_data(
+                    data, count=event.arg, paste_mode=PasteMode.VI_AFTER
+                )
+
+    @handle('"', Keys.Any, "P", filter=vi_navigation_mode)
+    def _paste_register_before(event: E) -> None:
+        """
+        Paste (before) from named register.
+        """
+        c = event.key_sequence[1].data
+        if c in vi_register_names:
+            data = event.app.vi_state.named_registers.get(c)
+            if data:
+                event.current_buffer.paste_clipboard_data(
+                    data, count=event.arg, paste_mode=PasteMode.VI_BEFORE
+                )
+
+    @handle("r", filter=vi_navigation_mode)
+    def _replace(event: E) -> None:
+        """
+        Go to 'replace-single'-mode.
+        """
+        event.app.vi_state.input_mode = InputMode.REPLACE_SINGLE
+
+    @handle("R", filter=vi_navigation_mode)
+    def _replace_mode(event: E) -> None:
+        """
+        Go to 'replace'-mode.
+        """
+        event.app.vi_state.input_mode = InputMode.REPLACE
+
+    @handle("s", filter=vi_navigation_mode & ~is_read_only)
+    def _substitute(event: E) -> None:
+        """
+        Substitute with new text
+        (Delete character(s) and go to insert mode.)
+        """
+        text = event.current_buffer.delete(count=event.arg)
+        event.app.clipboard.set_text(text)
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("u", filter=vi_navigation_mode, save_before=(lambda e: False))
+    def _undo(event: E) -> None:
+        for i in range(event.arg):
+            event.current_buffer.undo()
+
+    @handle("V", filter=vi_navigation_mode)
+    def _visual_line(event: E) -> None:
+        """
+        Start lines selection.
+        """
+        event.current_buffer.start_selection(selection_type=SelectionType.LINES)
+
+    @handle("c-v", filter=vi_navigation_mode)
+    def _visual_block(event: E) -> None:
+        """
+        Enter block selection mode.
+        """
+        event.current_buffer.start_selection(selection_type=SelectionType.BLOCK)
+
+    @handle("V", filter=vi_selection_mode)
+    def _visual_line2(event: E) -> None:
+        """
+        Exit line selection mode, or go from non line selection mode to line
+        selection mode.
+        """
+        selection_state = event.current_buffer.selection_state
+
+        if selection_state is not None:
+            if selection_state.type != SelectionType.LINES:
+                selection_state.type = SelectionType.LINES
+            else:
+                event.current_buffer.exit_selection()
+
+    @handle("v", filter=vi_navigation_mode)
+    def _visual(event: E) -> None:
+        """
+        Enter character selection mode.
+        """
+        event.current_buffer.start_selection(selection_type=SelectionType.CHARACTERS)
+
+    @handle("v", filter=vi_selection_mode)
+    def _visual2(event: E) -> None:
+        """
+        Exit character selection mode, or go from non-character-selection mode
+        to character selection mode.
+        """
+        selection_state = event.current_buffer.selection_state
+
+        if selection_state is not None:
+            if selection_state.type != SelectionType.CHARACTERS:
+                selection_state.type = SelectionType.CHARACTERS
+            else:
+                event.current_buffer.exit_selection()
+
+    @handle("c-v", filter=vi_selection_mode)
+    def _visual_block2(event: E) -> None:
+        """
+        Exit block selection mode, or go from non block selection mode to block
+        selection mode.
+        """
+        selection_state = event.current_buffer.selection_state
+
+        if selection_state is not None:
+            if selection_state.type != SelectionType.BLOCK:
+                selection_state.type = SelectionType.BLOCK
+            else:
+                event.current_buffer.exit_selection()
+
+    @handle("a", "w", filter=vi_selection_mode)
+    @handle("a", "W", filter=vi_selection_mode)
+    def _visual_auto_word(event: E) -> None:
+        """
+        Switch from visual linewise mode to visual characterwise mode.
+        """
+        buffer = event.current_buffer
+
+        if (
+            buffer.selection_state
+            and buffer.selection_state.type == SelectionType.LINES
+        ):
+            buffer.selection_state.type = SelectionType.CHARACTERS
+
+    @handle("x", filter=vi_navigation_mode)
+    def _delete(event: E) -> None:
+        """
+        Delete character.
+        """
+        buff = event.current_buffer
+        count = min(event.arg, len(buff.document.current_line_after_cursor))
+        if count:
+            text = event.current_buffer.delete(count=count)
+            event.app.clipboard.set_text(text)
+
+    @handle("X", filter=vi_navigation_mode)
+    def _delete_before_cursor(event: E) -> None:
+        buff = event.current_buffer
+        count = min(event.arg, len(buff.document.current_line_before_cursor))
+        if count:
+            text = event.current_buffer.delete_before_cursor(count=count)
+            event.app.clipboard.set_text(text)
+
+    @handle("y", "y", filter=vi_navigation_mode)
+    @handle("Y", filter=vi_navigation_mode)
+    def _yank_line(event: E) -> None:
+        """
+        Yank the whole line.
+        """
+        text = "\n".join(event.current_buffer.document.lines_from_current[: event.arg])
+        event.app.clipboard.set_data(ClipboardData(text, SelectionType.LINES))
+
+    @handle("+", filter=vi_navigation_mode)
+    def _next_line(event: E) -> None:
+        """
+        Move to first non whitespace of next line
+        """
+        buffer = event.current_buffer
+        buffer.cursor_position += buffer.document.get_cursor_down_position(
+            count=event.arg
+        )
+        buffer.cursor_position += buffer.document.get_start_of_line_position(
+            after_whitespace=True
+        )
+
+    @handle("-", filter=vi_navigation_mode)
+    def _prev_line(event: E) -> None:
+        """
+        Move to first non whitespace of previous line
+        """
+        buffer = event.current_buffer
+        buffer.cursor_position += buffer.document.get_cursor_up_position(
+            count=event.arg
+        )
+        buffer.cursor_position += buffer.document.get_start_of_line_position(
+            after_whitespace=True
+        )
+
+    @handle(">", ">", filter=vi_navigation_mode)
+    def _indent(event: E) -> None:
+        """
+        Indent lines.
+        """
+        buffer = event.current_buffer
+        current_row = buffer.document.cursor_position_row
+        indent(buffer, current_row, current_row + event.arg)
+
+    @handle("<", "<", filter=vi_navigation_mode)
+    def _unindent(event: E) -> None:
+        """
+        Unindent lines.
+        """
+        current_row = event.current_buffer.document.cursor_position_row
+        unindent(event.current_buffer, current_row, current_row + event.arg)
+
+    @handle("O", filter=vi_navigation_mode & ~is_read_only)
+    def _open_above(event: E) -> None:
+        """
+        Open line above and enter insertion mode
+        """
+        event.current_buffer.insert_line_above(copy_margin=not in_paste_mode())
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("o", filter=vi_navigation_mode & ~is_read_only)
+    def _open_below(event: E) -> None:
+        """
+        Open line below and enter insertion mode
+        """
+        event.current_buffer.insert_line_below(copy_margin=not in_paste_mode())
+        event.app.vi_state.input_mode = InputMode.INSERT
+
+    @handle("~", filter=vi_navigation_mode)
+    def _reverse_case(event: E) -> None:
+        """
+        Reverse case of current character and move cursor forward.
+        """
+        buffer = event.current_buffer
+        c = buffer.document.current_char
+
+        if c is not None and c != "\n":
+            buffer.insert_text(c.swapcase(), overwrite=True)
+
+    @handle("g", "u", "u", filter=vi_navigation_mode & ~is_read_only)
+    def _lowercase_line(event: E) -> None:
+        """
+        Lowercase current line.
+        """
+        buff = event.current_buffer
+        buff.transform_current_line(lambda s: s.lower())
+
+    @handle("g", "U", "U", filter=vi_navigation_mode & ~is_read_only)
+    def _uppercase_line(event: E) -> None:
+        """
+        Uppercase current line.
+        """
+        buff = event.current_buffer
+        buff.transform_current_line(lambda s: s.upper())
+
+    @handle("g", "~", "~", filter=vi_navigation_mode & ~is_read_only)
+    def _swapcase_line(event: E) -> None:
+        """
+        Swap case of the current line.
+        """
+        buff = event.current_buffer
+        buff.transform_current_line(lambda s: s.swapcase())
+
+    @handle("#", filter=vi_navigation_mode)
+    def _prev_occurence(event: E) -> None:
+        """
+        Go to previous occurrence of this word.
+        """
+        b = event.current_buffer
+        search_state = event.app.current_search_state
+
+        search_state.text = b.document.get_word_under_cursor()
+        search_state.direction = SearchDirection.BACKWARD
+
+        b.apply_search(search_state, count=event.arg, include_current_position=False)
+
+    @handle("*", filter=vi_navigation_mode)
+    def _next_occurance(event: E) -> None:
+        """
+        Go to next occurrence of this word.
+        """
+        b = event.current_buffer
+        search_state = event.app.current_search_state
+
+        search_state.text = b.document.get_word_under_cursor()
+        search_state.direction = SearchDirection.FORWARD
+
+        b.apply_search(search_state, count=event.arg, include_current_position=False)
+
+    @handle("(", filter=vi_navigation_mode)
+    def _begin_of_sentence(event: E) -> None:
+        # TODO: go to begin of sentence.
+        # XXX: should become text_object.
+        pass
+
+    @handle(")", filter=vi_navigation_mode)
+    def _end_of_sentence(event: E) -> None:
+        # TODO: go to end of sentence.
+        # XXX: should become text_object.
+        pass
+
+    operator = create_operator_decorator(key_bindings)
+    text_object = create_text_object_decorator(key_bindings)
+
+    @handle(Keys.Any, filter=vi_waiting_for_text_object_mode)
+    def _unknown_text_object(event: E) -> None:
+        """
+        Unknown key binding while waiting for a text object.
+        """
+        event.app.output.bell()
+
+    #
+    # *** Operators ***
+    #
+
+    def create_delete_and_change_operators(
+        delete_only: bool, with_register: bool = False
+    ) -> None:
+        """
+        Delete and change operators.
+
+        :param delete_only: Create an operator that deletes, but doesn't go to insert mode.
+        :param with_register: Copy the deleted text to this named register instead of the clipboard.
+        """
+        handler_keys: Iterable[str]
+        if with_register:
+            handler_keys = ('"', Keys.Any, "cd"[delete_only])
+        else:
+            handler_keys = "cd"[delete_only]
+
+        @operator(*handler_keys, filter=~is_read_only)
+        def delete_or_change_operator(event: E, text_object: TextObject) -> None:
+            clipboard_data = None
+            buff = event.current_buffer
+
+            if text_object:
+                new_document, clipboard_data = text_object.cut(buff)
+                buff.document = new_document
+
+            # Set deleted/changed text to clipboard or named register.
+            if clipboard_data and clipboard_data.text:
+                if with_register:
+                    reg_name = event.key_sequence[1].data
+                    if reg_name in vi_register_names:
+                        event.app.vi_state.named_registers[reg_name] = clipboard_data
+                else:
+                    event.app.clipboard.set_data(clipboard_data)
+
+            # Only go back to insert mode in case of 'change'.
+            if not delete_only:
+                event.app.vi_state.input_mode = InputMode.INSERT
+
+    create_delete_and_change_operators(False, False)
+    create_delete_and_change_operators(False, True)
+    create_delete_and_change_operators(True, False)
+    create_delete_and_change_operators(True, True)
+
+    def create_transform_handler(
+        filter: Filter, transform_func: Callable[[str], str], *a: str
+    ) -> None:
+        @operator(*a, filter=filter & ~is_read_only)
+        def _(event: E, text_object: TextObject) -> None:
+            """
+            Apply transformation (uppercase, lowercase, rot13, swap case).
+            """
+            buff = event.current_buffer
+            start, end = text_object.operator_range(buff.document)
+
+            if start < end:
+                # Transform.
+                buff.transform_region(
+                    buff.cursor_position + start,
+                    buff.cursor_position + end,
+                    transform_func,
+                )
+
+                # Move cursor
+                buff.cursor_position += text_object.end or text_object.start
+
+    for k, f, func in vi_transform_functions:
+        create_transform_handler(f, func, *k)
+
+    @operator("y")
+    def _yank(event: E, text_object: TextObject) -> None:
+        """
+        Yank operator. (Copy text.)
+        """
+        _, clipboard_data = text_object.cut(event.current_buffer)
+        if clipboard_data.text:
+            event.app.clipboard.set_data(clipboard_data)
+
+    @operator('"', Keys.Any, "y")
+    def _yank_to_register(event: E, text_object: TextObject) -> None:
+        """
+        Yank selection to named register.
+        """
+        c = event.key_sequence[1].data
+        if c in vi_register_names:
+            _, clipboard_data = text_object.cut(event.current_buffer)
+            event.app.vi_state.named_registers[c] = clipboard_data
+
+    @operator(">")
+    def _indent_text_object(event: E, text_object: TextObject) -> None:
+        """
+        Indent.
+        """
+        buff = event.current_buffer
+        from_, to = text_object.get_line_numbers(buff)
+        indent(buff, from_, to + 1, count=event.arg)
+
+    @operator("<")
+    def _unindent_text_object(event: E, text_object: TextObject) -> None:
+        """
+        Unindent.
+        """
+        buff = event.current_buffer
+        from_, to = text_object.get_line_numbers(buff)
+        unindent(buff, from_, to + 1, count=event.arg)
+
+    @operator("g", "q")
+    def _reshape(event: E, text_object: TextObject) -> None:
+        """
+        Reshape text.
+        """
+        buff = event.current_buffer
+        from_, to = text_object.get_line_numbers(buff)
+        reshape_text(buff, from_, to)
+
+    #
+    # *** Text objects ***
+    #
+
+    @text_object("b")
+    def _b(event: E) -> TextObject:
+        """
+        Move one word or token left.
+        """
+        return TextObject(
+            event.current_buffer.document.find_start_of_previous_word(count=event.arg)
+            or 0
+        )
+
+    @text_object("B")
+    def _B(event: E) -> TextObject:
+        """
+        Move one non-blank word left
+        """
+        return TextObject(
+            event.current_buffer.document.find_start_of_previous_word(
+                count=event.arg, WORD=True
+            )
+            or 0
+        )
+
+    @text_object("$")
+    def _dollar(event: E) -> TextObject:
+        """
+        'c$', 'd$' and '$':  Delete/change/move until end of line.
+        """
+        return TextObject(event.current_buffer.document.get_end_of_line_position())
+
+    @text_object("w")
+    def _word_forward(event: E) -> TextObject:
+        """
+        'word' forward. 'cw', 'dw', 'w': Delete/change/move one word.
+        """
+        return TextObject(
+            event.current_buffer.document.find_next_word_beginning(count=event.arg)
+            or event.current_buffer.document.get_end_of_document_position()
+        )
+
+    @text_object("W")
+    def _WORD_forward(event: E) -> TextObject:
+        """
+        'WORD' forward. 'cW', 'dW', 'W': Delete/change/move one WORD.
+        """
+        return TextObject(
+            event.current_buffer.document.find_next_word_beginning(
+                count=event.arg, WORD=True
+            )
+            or event.current_buffer.document.get_end_of_document_position()
+        )
+
+    @text_object("e")
+    def _end_of_word(event: E) -> TextObject:
+        """
+        End of 'word': 'ce', 'de', 'e'
+        """
+        end = event.current_buffer.document.find_next_word_ending(count=event.arg)
+        return TextObject(end - 1 if end else 0, type=TextObjectType.INCLUSIVE)
+
+    @text_object("E")
+    def _end_of_WORD(event: E) -> TextObject:
+        """
+        End of 'WORD': 'cE', 'dE', 'E'
+        """
+        end = event.current_buffer.document.find_next_word_ending(
+            count=event.arg, WORD=True
+        )
+        return TextObject(end - 1 if end else 0, type=TextObjectType.INCLUSIVE)
+
+    @text_object("i", "w", no_move_handler=True)
+    def _inner_word(event: E) -> TextObject:
+        """
+        Inner 'word': ciw and diw
+        """
+        start, end = event.current_buffer.document.find_boundaries_of_current_word()
+        return TextObject(start, end)
+
+    @text_object("a", "w", no_move_handler=True)
+    def _a_word(event: E) -> TextObject:
+        """
+        A 'word': caw and daw
+        """
+        start, end = event.current_buffer.document.find_boundaries_of_current_word(
+            include_trailing_whitespace=True
+        )
+        return TextObject(start, end)
+
+    @text_object("i", "W", no_move_handler=True)
+    def _inner_WORD(event: E) -> TextObject:
+        """
+        Inner 'WORD': ciW and diW
+        """
+        start, end = event.current_buffer.document.find_boundaries_of_current_word(
+            WORD=True
+        )
+        return TextObject(start, end)
+
+    @text_object("a", "W", no_move_handler=True)
+    def _a_WORD(event: E) -> TextObject:
+        """
+        A 'WORD': caw and daw
+        """
+        start, end = event.current_buffer.document.find_boundaries_of_current_word(
+            WORD=True, include_trailing_whitespace=True
+        )
+        return TextObject(start, end)
+
+    @text_object("a", "p", no_move_handler=True)
+    def _paragraph(event: E) -> TextObject:
+        """
+        Auto paragraph.
+        """
+        start = event.current_buffer.document.start_of_paragraph()
+        end = event.current_buffer.document.end_of_paragraph(count=event.arg)
+        return TextObject(start, end)
+
+    @text_object("^")
+    def _start_of_line(event: E) -> TextObject:
+        """'c^', 'd^' and '^': Soft start of line, after whitespace."""
+        return TextObject(
+            event.current_buffer.document.get_start_of_line_position(
+                after_whitespace=True
+            )
+        )
+
+    @text_object("0")
+    def _hard_start_of_line(event: E) -> TextObject:
+        """
+        'c0', 'd0': Hard start of line, before whitespace.
+        (The move '0' key is implemented elsewhere, because a '0' could also change the `arg`.)
+        """
+        return TextObject(
+            event.current_buffer.document.get_start_of_line_position(
+                after_whitespace=False
+            )
+        )
+
+    def create_ci_ca_handles(
+        ci_start: str, ci_end: str, inner: bool, key: Optional[str] = None
+    ) -> None:
+        # TODO: 'dat', 'dit', (tags (like xml)
+        """
+        Delete/Change string between this start and stop character. But keep these characters.
+        This implements all the ci", ci<, ci{, ci(, di", di<, ca", ca<, ... combinations.
+        """
+
+        def handler(event: E) -> TextObject:
+            if ci_start == ci_end:
+                # Quotes
+                start = event.current_buffer.document.find_backwards(
+                    ci_start, in_current_line=False
+                )
+                end = event.current_buffer.document.find(ci_end, in_current_line=False)
+            else:
+                # Brackets
+                start = event.current_buffer.document.find_enclosing_bracket_left(
+                    ci_start, ci_end
+                )
+                end = event.current_buffer.document.find_enclosing_bracket_right(
+                    ci_start, ci_end
+                )
+
+            if start is not None and end is not None:
+                offset = 0 if inner else 1
+                return TextObject(start + 1 - offset, end + offset)
+            else:
+                # Nothing found.
+                return TextObject(0)
+
+        if key is None:
+            text_object("ai"[inner], ci_start, no_move_handler=True)(handler)
+            text_object("ai"[inner], ci_end, no_move_handler=True)(handler)
+        else:
+            text_object("ai"[inner], key, no_move_handler=True)(handler)
+
+    for inner in (False, True):
+        for ci_start, ci_end in [
+            ('"', '"'),
+            ("'", "'"),
+            ("`", "`"),
+            ("[", "]"),
+            ("<", ">"),
+            ("{", "}"),
+            ("(", ")"),
+        ]:
+            create_ci_ca_handles(ci_start, ci_end, inner)
+
+        create_ci_ca_handles("(", ")", inner, "b")  # 'dab', 'dib'
+        create_ci_ca_handles("{", "}", inner, "B")  # 'daB', 'diB'
+
+    @text_object("{")
+    def _previous_section(event: E) -> TextObject:
+        """
+        Move to previous blank-line separated section.
+        Implements '{', 'c{', 'd{', 'y{'
+        """
+        index = event.current_buffer.document.start_of_paragraph(
+            count=event.arg, before=True
+        )
+        return TextObject(index)
+
+    @text_object("}")
+    def _next_section(event: E) -> TextObject:
+        """
+        Move to next blank-line separated section.
+        Implements '}', 'c}', 'd}', 'y}'
+        """
+        index = event.current_buffer.document.end_of_paragraph(
+            count=event.arg, after=True
+        )
+        return TextObject(index)
+
+    @text_object("f", Keys.Any)
+    def _next_occurence(event: E) -> TextObject:
+        """
+        Go to next occurrence of character. Typing 'fx' will move the
+        cursor to the next occurrence of character. 'x'.
+        """
+        event.app.vi_state.last_character_find = CharacterFind(event.data, False)
+        match = event.current_buffer.document.find(
+            event.data, in_current_line=True, count=event.arg
+        )
+        if match:
+            return TextObject(match, type=TextObjectType.INCLUSIVE)
+        else:
+            return TextObject(0)
+
+    @text_object("F", Keys.Any)
+    def _previous_occurance(event: E) -> TextObject:
+        """
+        Go to previous occurrence of character. Typing 'Fx' will move the
+        cursor to the previous occurrence of character. 'x'.
+        """
+        event.app.vi_state.last_character_find = CharacterFind(event.data, True)
+        return TextObject(
+            event.current_buffer.document.find_backwards(
+                event.data, in_current_line=True, count=event.arg
+            )
+            or 0
+        )
+
+    @text_object("t", Keys.Any)
+    def _t(event: E) -> TextObject:
+        """
+        Move right to the next occurrence of c, then one char backward.
+        """
+        event.app.vi_state.last_character_find = CharacterFind(event.data, False)
+        match = event.current_buffer.document.find(
+            event.data, in_current_line=True, count=event.arg
+        )
+        if match:
+            return TextObject(match - 1, type=TextObjectType.INCLUSIVE)
+        else:
+            return TextObject(0)
+
+    @text_object("T", Keys.Any)
+    def _T(event: E) -> TextObject:
+        """
+        Move left to the previous occurrence of c, then one char forward.
+        """
+        event.app.vi_state.last_character_find = CharacterFind(event.data, True)
+        match = event.current_buffer.document.find_backwards(
+            event.data, in_current_line=True, count=event.arg
+        )
+        return TextObject(match + 1 if match else 0)
+
+    def repeat(reverse: bool) -> None:
+        """
+        Create ',' and ';' commands.
+        """
+
+        @text_object("," if reverse else ";")
+        def _(event: E) -> TextObject:
+            """
+            Repeat the last 'f'/'F'/'t'/'T' command.
+            """
+            pos: Optional[int] = 0
+            vi_state = event.app.vi_state
+
+            type = TextObjectType.EXCLUSIVE
+
+            if vi_state.last_character_find:
+                char = vi_state.last_character_find.character
+                backwards = vi_state.last_character_find.backwards
+
+                if reverse:
+                    backwards = not backwards
+
+                if backwards:
+                    pos = event.current_buffer.document.find_backwards(
+                        char, in_current_line=True, count=event.arg
+                    )
+                else:
+                    pos = event.current_buffer.document.find(
+                        char, in_current_line=True, count=event.arg
+                    )
+                    type = TextObjectType.INCLUSIVE
+            if pos:
+                return TextObject(pos, type=type)
+            else:
+                return TextObject(0)
+
+    repeat(True)
+    repeat(False)
+
+    @text_object("h")
+    @text_object("left")
+    def _left(event: E) -> TextObject:
+        """
+        Implements 'ch', 'dh', 'h': Cursor left.
+        """
+        return TextObject(
+            event.current_buffer.document.get_cursor_left_position(count=event.arg)
+        )
+
+    @text_object("j", no_move_handler=True, no_selection_handler=True)
+    # Note: We also need `no_selection_handler`, because we in
+    #       selection mode, we prefer the other 'j' binding that keeps
+    #       `buffer.preferred_column`.
+    def _down(event: E) -> TextObject:
+        """
+        Implements 'cj', 'dj', 'j', ... Cursor up.
+        """
+        return TextObject(
+            event.current_buffer.document.get_cursor_down_position(count=event.arg),
+            type=TextObjectType.LINEWISE,
+        )
+
+    @text_object("k", no_move_handler=True, no_selection_handler=True)
+    def _up(event: E) -> TextObject:
+        """
+        Implements 'ck', 'dk', 'k', ... Cursor up.
+        """
+        return TextObject(
+            event.current_buffer.document.get_cursor_up_position(count=event.arg),
+            type=TextObjectType.LINEWISE,
+        )
+
+    @text_object("l")
+    @text_object(" ")
+    @text_object("right")
+    def _right(event: E) -> TextObject:
+        """
+        Implements 'cl', 'dl', 'l', 'c ', 'd ', ' '. Cursor right.
+        """
+        return TextObject(
+            event.current_buffer.document.get_cursor_right_position(count=event.arg)
+        )
+
+    @text_object("H")
+    def _top_of_screen(event: E) -> TextObject:
+        """
+        Moves to the start of the visible region. (Below the scroll offset.)
+        Implements 'cH', 'dH', 'H'.
+        """
+        w = event.app.layout.current_window
+        b = event.current_buffer
+
+        if w and w.render_info:
+            # When we find a Window that has BufferControl showing this window,
+            # move to the start of the visible area.
+            pos = (
+                b.document.translate_row_col_to_index(
+                    w.render_info.first_visible_line(after_scroll_offset=True), 0
+                )
+                - b.cursor_position
+            )
+
+        else:
+            # Otherwise, move to the start of the input.
+            pos = -len(b.document.text_before_cursor)
+        return TextObject(pos, type=TextObjectType.LINEWISE)
+
+    @text_object("M")
+    def _middle_of_screen(event: E) -> TextObject:
+        """
+        Moves cursor to the vertical center of the visible region.
+        Implements 'cM', 'dM', 'M'.
+        """
+        w = event.app.layout.current_window
+        b = event.current_buffer
+
+        if w and w.render_info:
+            # When we find a Window that has BufferControl showing this window,
+            # move to the center of the visible area.
+            pos = (
+                b.document.translate_row_col_to_index(
+                    w.render_info.center_visible_line(), 0
+                )
+                - b.cursor_position
+            )
+
+        else:
+            # Otherwise, move to the start of the input.
+            pos = -len(b.document.text_before_cursor)
+        return TextObject(pos, type=TextObjectType.LINEWISE)
+
+    @text_object("L")
+    def _end_of_screen(event: E) -> TextObject:
+        """
+        Moves to the end of the visible region. (Above the scroll offset.)
+        """
+        w = event.app.layout.current_window
+        b = event.current_buffer
+
+        if w and w.render_info:
+            # When we find a Window that has BufferControl showing this window,
+            # move to the end of the visible area.
+            pos = (
+                b.document.translate_row_col_to_index(
+                    w.render_info.last_visible_line(before_scroll_offset=True), 0
+                )
+                - b.cursor_position
+            )
+
+        else:
+            # Otherwise, move to the end of the input.
+            pos = len(b.document.text_after_cursor)
+        return TextObject(pos, type=TextObjectType.LINEWISE)
+
+    @text_object("n", no_move_handler=True)
+    def _search_next(event: E) -> TextObject:
+        """
+        Search next.
+        """
+        buff = event.current_buffer
+        search_state = event.app.current_search_state
+
+        cursor_position = buff.get_search_position(
+            search_state, include_current_position=False, count=event.arg
+        )
+        return TextObject(cursor_position - buff.cursor_position)
+
+    @handle("n", filter=vi_navigation_mode)
+    def _search_next2(event: E) -> None:
+        """
+        Search next in navigation mode. (This goes through the history.)
+        """
+        search_state = event.app.current_search_state
+
+        event.current_buffer.apply_search(
+            search_state, include_current_position=False, count=event.arg
+        )
+
+    @text_object("N", no_move_handler=True)
+    def _search_previous(event: E) -> TextObject:
+        """
+        Search previous.
+        """
+        buff = event.current_buffer
+        search_state = event.app.current_search_state
+
+        cursor_position = buff.get_search_position(
+            ~search_state, include_current_position=False, count=event.arg
+        )
+        return TextObject(cursor_position - buff.cursor_position)
+
+    @handle("N", filter=vi_navigation_mode)
+    def _search_previous2(event: E) -> None:
+        """
+        Search previous in navigation mode. (This goes through the history.)
+        """
+        search_state = event.app.current_search_state
+
+        event.current_buffer.apply_search(
+            ~search_state, include_current_position=False, count=event.arg
+        )
+
+    @handle("z", "+", filter=vi_navigation_mode | vi_selection_mode)
+    @handle("z", "t", filter=vi_navigation_mode | vi_selection_mode)
+    @handle("z", "enter", filter=vi_navigation_mode | vi_selection_mode)
+    def _scroll_top(event: E) -> None:
+        """
+        Scrolls the window to makes the current line the first line in the visible region.
+        """
+        b = event.current_buffer
+        event.app.layout.current_window.vertical_scroll = b.document.cursor_position_row
+
+    @handle("z", "-", filter=vi_navigation_mode | vi_selection_mode)
+    @handle("z", "b", filter=vi_navigation_mode | vi_selection_mode)
+    def _scroll_bottom(event: E) -> None:
+        """
+        Scrolls the window to makes the current line the last line in the visible region.
+        """
+        # We can safely set the scroll offset to zero; the Window will make
+        # sure that it scrolls at least enough to make the cursor visible
+        # again.
+        event.app.layout.current_window.vertical_scroll = 0
+
+    @handle("z", "z", filter=vi_navigation_mode | vi_selection_mode)
+    def _scroll_center(event: E) -> None:
+        """
+        Center Window vertically around cursor.
+        """
+        w = event.app.layout.current_window
+        b = event.current_buffer
+
+        if w and w.render_info:
+            info = w.render_info
+
+            # Calculate the offset that we need in order to position the row
+            # containing the cursor in the center.
+            scroll_height = info.window_height // 2
+
+            y = max(0, b.document.cursor_position_row - 1)
+            height = 0
+            while y > 0:
+                line_height = info.get_height_for_line(y)
+
+                if height + line_height < scroll_height:
+                    height += line_height
+                    y -= 1
+                else:
+                    break
+
+            w.vertical_scroll = y
+
+    @text_object("%")
+    def _goto_corresponding_bracket(event: E) -> TextObject:
+        """
+        Implements 'c%', 'd%', '%, 'y%' (Move to corresponding bracket.)
+        If an 'arg' has been given, go this this % position in the file.
+        """
+        buffer = event.current_buffer
+
+        if event._arg:
+            # If 'arg' has been given, the meaning of % is to go to the 'x%'
+            # row in the file.
+            if 0 < event.arg <= 100:
+                absolute_index = buffer.document.translate_row_col_to_index(
+                    int((event.arg * buffer.document.line_count - 1) / 100), 0
+                )
+                return TextObject(
+                    absolute_index - buffer.document.cursor_position,
+                    type=TextObjectType.LINEWISE,
+                )
+            else:
+                return TextObject(0)  # Do nothing.
+
+        else:
+            # Move to the corresponding opening/closing bracket (()'s, []'s and {}'s).
+            match = buffer.document.find_matching_bracket_position()
+            if match:
+                return TextObject(match, type=TextObjectType.INCLUSIVE)
+            else:
+                return TextObject(0)
+
+    @text_object("|")
+    def _to_column(event: E) -> TextObject:
+        """
+        Move to the n-th column (you may specify the argument n by typing it on
+        number keys, for example, 20|).
+        """
+        return TextObject(
+            event.current_buffer.document.get_column_cursor_position(event.arg - 1)
+        )
+
+    @text_object("g", "g")
+    def _goto_first_line(event: E) -> TextObject:
+        """
+        Go to the start of the very first line.
+        Implements 'gg', 'cgg', 'ygg'
+        """
+        d = event.current_buffer.document
+
+        if event._arg:
+            # Move to the given line.
+            return TextObject(
+                d.translate_row_col_to_index(event.arg - 1, 0) - d.cursor_position,
+                type=TextObjectType.LINEWISE,
+            )
+        else:
+            # Move to the top of the input.
+            return TextObject(
+                d.get_start_of_document_position(), type=TextObjectType.LINEWISE
+            )
+
+    @text_object("g", "_")
+    def _goto_last_line(event: E) -> TextObject:
+        """
+        Go to last non-blank of line.
+        'g_', 'cg_', 'yg_', etc..
+        """
+        return TextObject(
+            event.current_buffer.document.last_non_blank_of_current_line_position(),
+            type=TextObjectType.INCLUSIVE,
+        )
+
+    @text_object("g", "e")
+    def _ge(event: E) -> TextObject:
+        """
+        Go to last character of previous word.
+        'ge', 'cge', 'yge', etc..
+        """
+        prev_end = event.current_buffer.document.find_previous_word_ending(
+            count=event.arg
+        )
+        return TextObject(
+            prev_end - 1 if prev_end is not None else 0, type=TextObjectType.INCLUSIVE
+        )
+
+    @text_object("g", "E")
+    def _gE(event: E) -> TextObject:
+        """
+        Go to last character of previous WORD.
+        'gE', 'cgE', 'ygE', etc..
+        """
+        prev_end = event.current_buffer.document.find_previous_word_ending(
+            count=event.arg, WORD=True
+        )
+        return TextObject(
+            prev_end - 1 if prev_end is not None else 0, type=TextObjectType.INCLUSIVE
+        )
+
+    @text_object("g", "m")
+    def _gm(event: E) -> TextObject:
+        """
+        Like g0, but half a screenwidth to the right. (Or as much as possible.)
+        """
+        w = event.app.layout.current_window
+        buff = event.current_buffer
+
+        if w and w.render_info:
+            width = w.render_info.window_width
+            start = buff.document.get_start_of_line_position(after_whitespace=False)
+            start += int(min(width / 2, len(buff.document.current_line)))
+
+            return TextObject(start, type=TextObjectType.INCLUSIVE)
+        return TextObject(0)
+
+    @text_object("G")
+    def _last_line(event: E) -> TextObject:
+        """
+        Go to the end of the document. (If no arg has been given.)
+        """
+        buf = event.current_buffer
+        return TextObject(
+            buf.document.translate_row_col_to_index(buf.document.line_count - 1, 0)
+            - buf.cursor_position,
+            type=TextObjectType.LINEWISE,
+        )
+
+    #
+    # *** Other ***
+    #
+
+    @handle("G", filter=has_arg)
+    def _to_nth_history_line(event: E) -> None:
+        """
+        If an argument is given, move to this line in the  history. (for
+        example, 15G)
+        """
+        event.current_buffer.go_to_history(event.arg - 1)
+
+    for n in "123456789":
+
+        @handle(
+            n,
+            filter=vi_navigation_mode
+            | vi_selection_mode
+            | vi_waiting_for_text_object_mode,
+        )
+        def _arg(event: E) -> None:
+            """
+            Always handle numerics in navigation mode as arg.
+            """
+            event.append_to_arg_count(event.data)
+
+    @handle(
+        "0",
+        filter=(
+            vi_navigation_mode | vi_selection_mode | vi_waiting_for_text_object_mode
+        )
+        & has_arg,
+    )
+    def _0_arg(event: E) -> None:
+        """
+        Zero when an argument was already give.
+        """
+        event.append_to_arg_count(event.data)
+
+    @handle(Keys.Any, filter=vi_replace_mode)
+    def _insert_text(event: E) -> None:
+        """
+        Insert data at cursor position.
+        """
+        event.current_buffer.insert_text(event.data, overwrite=True)
+
+    @handle(Keys.Any, filter=vi_replace_single_mode)
+    def _replace_single(event: E) -> None:
+        """
+        Replace single character at cursor position.
+        """
+        event.current_buffer.insert_text(event.data, overwrite=True)
+        event.current_buffer.cursor_position -= 1
+        event.app.vi_state.input_mode = InputMode.NAVIGATION
+
+    @handle(
+        Keys.Any,
+        filter=vi_insert_multiple_mode,
+        save_before=(lambda e: not e.is_repeat),
+    )
+    def _insert_text_multiple_cursors(event: E) -> None:
+        """
+        Insert data at multiple cursor positions at once.
+        (Usually a result of pressing 'I' or 'A' in block-selection mode.)
+        """
+        buff = event.current_buffer
+        original_text = buff.text
+
+        # Construct new text.
+        text = []
+        p = 0
+
+        for p2 in buff.multiple_cursor_positions:
+            text.append(original_text[p:p2])
+            text.append(event.data)
+            p = p2
+
+        text.append(original_text[p:])
+
+        # Shift all cursor positions.
+        new_cursor_positions = [
+            pos + i + 1 for i, pos in enumerate(buff.multiple_cursor_positions)
+        ]
+
+        # Set result.
+        buff.text = "".join(text)
+        buff.multiple_cursor_positions = new_cursor_positions
+        buff.cursor_position += 1
+
+    @handle("backspace", filter=vi_insert_multiple_mode)
+    def _delete_before_multiple_cursors(event: E) -> None:
+        """
+        Backspace, using multiple cursors.
+        """
+        buff = event.current_buffer
+        original_text = buff.text
+
+        # Construct new text.
+        deleted_something = False
+        text = []
+        p = 0
+
+        for p2 in buff.multiple_cursor_positions:
+            if p2 > 0 and original_text[p2 - 1] != "\n":  # Don't delete across lines.
+                text.append(original_text[p : p2 - 1])
+                deleted_something = True
+            else:
+                text.append(original_text[p:p2])
+            p = p2
+
+        text.append(original_text[p:])
+
+        if deleted_something:
+            # Shift all cursor positions.
+            lengths = [len(part) for part in text[:-1]]
+            new_cursor_positions = list(accumulate(lengths))
+
+            # Set result.
+            buff.text = "".join(text)
+            buff.multiple_cursor_positions = new_cursor_positions
+            buff.cursor_position -= 1
+        else:
+            event.app.output.bell()
+
+    @handle("delete", filter=vi_insert_multiple_mode)
+    def _delete_after_multiple_cursors(event: E) -> None:
+        """
+        Delete, using multiple cursors.
+        """
+        buff = event.current_buffer
+        original_text = buff.text
+
+        # Construct new text.
+        deleted_something = False
+        text = []
+        new_cursor_positions = []
+        p = 0
+
+        for p2 in buff.multiple_cursor_positions:
+            text.append(original_text[p:p2])
+            if p2 >= len(original_text) or original_text[p2] == "\n":
+                # Don't delete across lines.
+                p = p2
+            else:
+                p = p2 + 1
+                deleted_something = True
+
+        text.append(original_text[p:])
+
+        if deleted_something:
+            # Shift all cursor positions.
+            lengths = [len(part) for part in text[:-1]]
+            new_cursor_positions = list(accumulate(lengths))
+
+            # Set result.
+            buff.text = "".join(text)
+            buff.multiple_cursor_positions = new_cursor_positions
+        else:
+            event.app.output.bell()
+
+    @handle("left", filter=vi_insert_multiple_mode)
+    def _left_multiple(event: E) -> None:
+        """
+        Move all cursors to the left.
+        (But keep all cursors on the same line.)
+        """
+        buff = event.current_buffer
+        new_positions = []
+
+        for p in buff.multiple_cursor_positions:
+            if buff.document.translate_index_to_position(p)[1] > 0:
+                p -= 1
+            new_positions.append(p)
+
+        buff.multiple_cursor_positions = new_positions
+
+        if buff.document.cursor_position_col > 0:
+            buff.cursor_position -= 1
+
+    @handle("right", filter=vi_insert_multiple_mode)
+    def _right_multiple(event: E) -> None:
+        """
+        Move all cursors to the right.
+        (But keep all cursors on the same line.)
+        """
+        buff = event.current_buffer
+        new_positions = []
+
+        for p in buff.multiple_cursor_positions:
+            row, column = buff.document.translate_index_to_position(p)
+            if column < len(buff.document.lines[row]):
+                p += 1
+            new_positions.append(p)
+
+        buff.multiple_cursor_positions = new_positions
+
+        if not buff.document.is_cursor_at_the_end_of_line:
+            buff.cursor_position += 1
+
+    @handle("up", filter=vi_insert_multiple_mode)
+    @handle("down", filter=vi_insert_multiple_mode)
+    def _updown_multiple(event: E) -> None:
+        """
+        Ignore all up/down key presses when in multiple cursor mode.
+        """
+
+    @handle("c-x", "c-l", filter=vi_insert_mode)
+    def _complete_line(event: E) -> None:
+        """
+        Pressing the ControlX - ControlL sequence in Vi mode does line
+        completion based on the other lines in the document and the history.
+        """
+        event.current_buffer.start_history_lines_completion()
+
+    @handle("c-x", "c-f", filter=vi_insert_mode)
+    def _complete_filename(event: E) -> None:
+        """
+        Complete file names.
+        """
+        # TODO
+        pass
+
+    @handle("c-k", filter=vi_insert_mode | vi_replace_mode)
+    def _digraph(event: E) -> None:
+        """
+        Go into digraph mode.
+        """
+        event.app.vi_state.waiting_for_digraph = True
+
+    @Condition
+    def digraph_symbol_1_given() -> bool:
+        return get_app().vi_state.digraph_symbol1 is not None
+
+    @handle(Keys.Any, filter=vi_digraph_mode & ~digraph_symbol_1_given)
+    def _digraph1(event: E) -> None:
+        """
+        First digraph symbol.
+        """
+        event.app.vi_state.digraph_symbol1 = event.data
+
+    @handle(Keys.Any, filter=vi_digraph_mode & digraph_symbol_1_given)
+    def _create_digraph(event: E) -> None:
+        """
+        Insert digraph.
+        """
+        try:
+            # Lookup.
+            code: Tuple[str, str] = (
+                event.app.vi_state.digraph_symbol1 or "",
+                event.data,
+            )
+            if code not in DIGRAPHS:
+                code = code[::-1]  # Try reversing.
+            symbol = DIGRAPHS[code]
+        except KeyError:
+            # Unknown digraph.
+            event.app.output.bell()
+        else:
+            # Insert digraph.
+            overwrite = event.app.vi_state.input_mode == InputMode.REPLACE
+            event.current_buffer.insert_text(chr(symbol), overwrite=overwrite)
+            event.app.vi_state.waiting_for_digraph = False
+        finally:
+            event.app.vi_state.waiting_for_digraph = False
+            event.app.vi_state.digraph_symbol1 = None
+
+    @handle("c-o", filter=vi_insert_mode | vi_replace_mode)
+    def _quick_normal_mode(event: E) -> None:
+        """
+        Go into normal mode for one single action.
+        """
+        event.app.vi_state.temporary_navigation_mode = True
+
+    @handle("q", Keys.Any, filter=vi_navigation_mode & ~vi_recording_macro)
+    def _start_macro(event: E) -> None:
+        """
+        Start recording macro.
+        """
+        c = event.key_sequence[1].data
+        if c in vi_register_names:
+            vi_state = event.app.vi_state
+
+            vi_state.recording_register = c
+            vi_state.current_recording = ""
+
+    @handle("q", filter=vi_navigation_mode & vi_recording_macro)
+    def _stop_macro(event: E) -> None:
+        """
+        Stop recording macro.
+        """
+        vi_state = event.app.vi_state
+
+        # Store and stop recording.
+        if vi_state.recording_register:
+            vi_state.named_registers[vi_state.recording_register] = ClipboardData(
+                vi_state.current_recording
+            )
+            vi_state.recording_register = None
+            vi_state.current_recording = ""
+
+    @handle("@", Keys.Any, filter=vi_navigation_mode, record_in_macro=False)
+    def _execute_macro(event: E) -> None:
+        """
+        Execute macro.
+
+        Notice that we pass `record_in_macro=False`. This ensures that the `@x`
+        keys don't appear in the recording itself. This function inserts the
+        body of the called macro back into the KeyProcessor, so these keys will
+        be added later on to the macro of their handlers have
+        `record_in_macro=True`.
+        """
+        # Retrieve macro.
+        c = event.key_sequence[1].data
+        try:
+            macro = event.app.vi_state.named_registers[c]
+        except KeyError:
+            return
+
+        # Expand macro (which is a string in the register), in individual keys.
+        # Use vt100 parser for this.
+        keys: List[KeyPress] = []
+
+        parser = Vt100Parser(keys.append)
+        parser.feed(macro.text)
+        parser.flush()
+
+        # Now feed keys back to the input processor.
+        for _ in range(event.arg):
+            event.app.key_processor.feed_multiple(keys, first=True)
+
+    return ConditionalKeyBindings(key_bindings, vi_mode)
+
+
+def load_vi_search_bindings() -> KeyBindingsBase:
+    key_bindings = KeyBindings()
+    handle = key_bindings.add
+    from . import search
+
+    @Condition
+    def search_buffer_is_empty() -> bool:
+        "Returns True when the search buffer is empty."
+        return get_app().current_buffer.text == ""
+
+    # Vi-style forward search.
+    handle(
+        "/",
+        filter=(vi_navigation_mode | vi_selection_mode) & ~vi_search_direction_reversed,
+    )(search.start_forward_incremental_search)
+    handle(
+        "?",
+        filter=(vi_navigation_mode | vi_selection_mode) & vi_search_direction_reversed,
+    )(search.start_forward_incremental_search)
+    handle("c-s")(search.start_forward_incremental_search)
+
+    # Vi-style backward search.
+    handle(
+        "?",
+        filter=(vi_navigation_mode | vi_selection_mode) & ~vi_search_direction_reversed,
+    )(search.start_reverse_incremental_search)
+    handle(
+        "/",
+        filter=(vi_navigation_mode | vi_selection_mode) & vi_search_direction_reversed,
+    )(search.start_reverse_incremental_search)
+    handle("c-r")(search.start_reverse_incremental_search)
+
+    # Apply the search. (At the / or ? prompt.)
+    handle("enter", filter=is_searching)(search.accept_search)
+
+    handle("c-r", filter=is_searching)(search.reverse_incremental_search)
+    handle("c-s", filter=is_searching)(search.forward_incremental_search)
+
+    handle("c-c")(search.abort_search)
+    handle("c-g")(search.abort_search)
+    handle("backspace", filter=search_buffer_is_empty)(search.abort_search)
+
+    # Handle escape. This should accept the search, just like readline.
+    # `abort_search` would be a meaningful alternative.
+    handle("escape")(search.accept_search)
+
+    return ConditionalKeyBindings(key_bindings, vi_mode)
diff --git a/src/prompt_toolkit/key_binding/defaults.py b/src/prompt_toolkit/key_binding/defaults.py
new file mode 100644
index 0000000..baa5974
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/defaults.py
@@ -0,0 +1,60 @@
+"""
+Default key bindings.::
+
+    key_bindings = load_key_bindings()
+    app = Application(key_bindings=key_bindings)
+"""
+from prompt_toolkit.filters import buffer_has_focus
+from prompt_toolkit.key_binding.bindings.basic import load_basic_bindings
+from prompt_toolkit.key_binding.bindings.cpr import load_cpr_bindings
+from prompt_toolkit.key_binding.bindings.emacs import (
+    load_emacs_bindings,
+    load_emacs_search_bindings,
+    load_emacs_shift_selection_bindings,
+)
+from prompt_toolkit.key_binding.bindings.mouse import load_mouse_bindings
+from prompt_toolkit.key_binding.bindings.vi import (
+    load_vi_bindings,
+    load_vi_search_bindings,
+)
+from prompt_toolkit.key_binding.key_bindings import (
+    ConditionalKeyBindings,
+    KeyBindingsBase,
+    merge_key_bindings,
+)
+
+__all__ = [
+    "load_key_bindings",
+]
+
+
+def load_key_bindings() -> KeyBindingsBase:
+    """
+    Create a KeyBindings object that contains the default key bindings.
+    """
+    all_bindings = merge_key_bindings(
+        [
+            # Load basic bindings.
+            load_basic_bindings(),
+            # Load emacs bindings.
+            load_emacs_bindings(),
+            load_emacs_search_bindings(),
+            load_emacs_shift_selection_bindings(),
+            # Load Vi bindings.
+            load_vi_bindings(),
+            load_vi_search_bindings(),
+        ]
+    )
+
+    return merge_key_bindings(
+        [
+            # Make sure that the above key bindings are only active if the
+            # currently focused control is a `BufferControl`. For other controls, we
+            # don't want these key bindings to intervene. (This would break "ptterm"
+            # for instance, which handles 'Keys.Any' in the user control itself.)
+            ConditionalKeyBindings(all_bindings, buffer_has_focus),
+            # Active, even when no buffer has been focused.
+            load_mouse_bindings(),
+            load_cpr_bindings(),
+        ]
+    )
diff --git a/src/prompt_toolkit/key_binding/digraphs.py b/src/prompt_toolkit/key_binding/digraphs.py
new file mode 100644
index 0000000..ad3d288
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/digraphs.py
@@ -0,0 +1,1377 @@
+"""
+Vi Digraphs.
+This is a list of special characters that can be inserted in Vi insert mode by
+pressing Control-K followed by to normal characters.
+
+Taken from Neovim and translated to Python:
+https://raw.githubusercontent.com/neovim/neovim/master/src/nvim/digraph.c
+"""
+from typing import Dict, Tuple
+
+__all__ = [
+    "DIGRAPHS",
+]
+
+# digraphs for Unicode from RFC1345
+# (also work for ISO-8859-1 aka latin1)
+DIGRAPHS: Dict[Tuple[str, str], int] = {
+    ("N", "U"): 0x00,
+    ("S", "H"): 0x01,
+    ("S", "X"): 0x02,
+    ("E", "X"): 0x03,
+    ("E", "T"): 0x04,
+    ("E", "Q"): 0x05,
+    ("A", "K"): 0x06,
+    ("B", "L"): 0x07,
+    ("B", "S"): 0x08,
+    ("H", "T"): 0x09,
+    ("L", "F"): 0x0A,
+    ("V", "T"): 0x0B,
+    ("F", "F"): 0x0C,
+    ("C", "R"): 0x0D,
+    ("S", "O"): 0x0E,
+    ("S", "I"): 0x0F,
+    ("D", "L"): 0x10,
+    ("D", "1"): 0x11,
+    ("D", "2"): 0x12,
+    ("D", "3"): 0x13,
+    ("D", "4"): 0x14,
+    ("N", "K"): 0x15,
+    ("S", "Y"): 0x16,
+    ("E", "B"): 0x17,
+    ("C", "N"): 0x18,
+    ("E", "M"): 0x19,
+    ("S", "B"): 0x1A,
+    ("E", "C"): 0x1B,
+    ("F", "S"): 0x1C,
+    ("G", "S"): 0x1D,
+    ("R", "S"): 0x1E,
+    ("U", "S"): 0x1F,
+    ("S", "P"): 0x20,
+    ("N", "b"): 0x23,
+    ("D", "O"): 0x24,
+    ("A", "t"): 0x40,
+    ("<", "("): 0x5B,
+    ("/", "/"): 0x5C,
+    (")", ">"): 0x5D,
+    ("'", ">"): 0x5E,
+    ("'", "!"): 0x60,
+    ("(", "!"): 0x7B,
+    ("!", "!"): 0x7C,
+    ("!", ")"): 0x7D,
+    ("'", "?"): 0x7E,
+    ("D", "T"): 0x7F,
+    ("P", "A"): 0x80,
+    ("H", "O"): 0x81,
+    ("B", "H"): 0x82,
+    ("N", "H"): 0x83,
+    ("I", "N"): 0x84,
+    ("N", "L"): 0x85,
+    ("S", "A"): 0x86,
+    ("E", "S"): 0x87,
+    ("H", "S"): 0x88,
+    ("H", "J"): 0x89,
+    ("V", "S"): 0x8A,
+    ("P", "D"): 0x8B,
+    ("P", "U"): 0x8C,
+    ("R", "I"): 0x8D,
+    ("S", "2"): 0x8E,
+    ("S", "3"): 0x8F,
+    ("D", "C"): 0x90,
+    ("P", "1"): 0x91,
+    ("P", "2"): 0x92,
+    ("T", "S"): 0x93,
+    ("C", "C"): 0x94,
+    ("M", "W"): 0x95,
+    ("S", "G"): 0x96,
+    ("E", "G"): 0x97,
+    ("S", "S"): 0x98,
+    ("G", "C"): 0x99,
+    ("S", "C"): 0x9A,
+    ("C", "I"): 0x9B,
+    ("S", "T"): 0x9C,
+    ("O", "C"): 0x9D,
+    ("P", "M"): 0x9E,
+    ("A", "C"): 0x9F,
+    ("N", "S"): 0xA0,
+    ("!", "I"): 0xA1,
+    ("C", "t"): 0xA2,
+    ("P", "d"): 0xA3,
+    ("C", "u"): 0xA4,
+    ("Y", "e"): 0xA5,
+    ("B", "B"): 0xA6,
+    ("S", "E"): 0xA7,
+    ("'", ":"): 0xA8,
+    ("C", "o"): 0xA9,
+    ("-", "a"): 0xAA,
+    ("<", "<"): 0xAB,
+    ("N", "O"): 0xAC,
+    ("-", "-"): 0xAD,
+    ("R", "g"): 0xAE,
+    ("'", "m"): 0xAF,
+    ("D", "G"): 0xB0,
+    ("+", "-"): 0xB1,
+    ("2", "S"): 0xB2,
+    ("3", "S"): 0xB3,
+    ("'", "'"): 0xB4,
+    ("M", "y"): 0xB5,
+    ("P", "I"): 0xB6,
+    (".", "M"): 0xB7,
+    ("'", ","): 0xB8,
+    ("1", "S"): 0xB9,
+    ("-", "o"): 0xBA,
+    (">", ">"): 0xBB,
+    ("1", "4"): 0xBC,
+    ("1", "2"): 0xBD,
+    ("3", "4"): 0xBE,
+    ("?", "I"): 0xBF,
+    ("A", "!"): 0xC0,
+    ("A", "'"): 0xC1,
+    ("A", ">"): 0xC2,
+    ("A", "?"): 0xC3,
+    ("A", ":"): 0xC4,
+    ("A", "A"): 0xC5,
+    ("A", "E"): 0xC6,
+    ("C", ","): 0xC7,
+    ("E", "!"): 0xC8,
+    ("E", "'"): 0xC9,
+    ("E", ">"): 0xCA,
+    ("E", ":"): 0xCB,
+    ("I", "!"): 0xCC,
+    ("I", "'"): 0xCD,
+    ("I", ">"): 0xCE,
+    ("I", ":"): 0xCF,
+    ("D", "-"): 0xD0,
+    ("N", "?"): 0xD1,
+    ("O", "!"): 0xD2,
+    ("O", "'"): 0xD3,
+    ("O", ">"): 0xD4,
+    ("O", "?"): 0xD5,
+    ("O", ":"): 0xD6,
+    ("*", "X"): 0xD7,
+    ("O", "/"): 0xD8,
+    ("U", "!"): 0xD9,
+    ("U", "'"): 0xDA,
+    ("U", ">"): 0xDB,
+    ("U", ":"): 0xDC,
+    ("Y", "'"): 0xDD,
+    ("T", "H"): 0xDE,
+    ("s", "s"): 0xDF,
+    ("a", "!"): 0xE0,
+    ("a", "'"): 0xE1,
+    ("a", ">"): 0xE2,
+    ("a", "?"): 0xE3,
+    ("a", ":"): 0xE4,
+    ("a", "a"): 0xE5,
+    ("a", "e"): 0xE6,
+    ("c", ","): 0xE7,
+    ("e", "!"): 0xE8,
+    ("e", "'"): 0xE9,
+    ("e", ">"): 0xEA,
+    ("e", ":"): 0xEB,
+    ("i", "!"): 0xEC,
+    ("i", "'"): 0xED,
+    ("i", ">"): 0xEE,
+    ("i", ":"): 0xEF,
+    ("d", "-"): 0xF0,
+    ("n", "?"): 0xF1,
+    ("o", "!"): 0xF2,
+    ("o", "'"): 0xF3,
+    ("o", ">"): 0xF4,
+    ("o", "?"): 0xF5,
+    ("o", ":"): 0xF6,
+    ("-", ":"): 0xF7,
+    ("o", "/"): 0xF8,
+    ("u", "!"): 0xF9,
+    ("u", "'"): 0xFA,
+    ("u", ">"): 0xFB,
+    ("u", ":"): 0xFC,
+    ("y", "'"): 0xFD,
+    ("t", "h"): 0xFE,
+    ("y", ":"): 0xFF,
+    ("A", "-"): 0x0100,
+    ("a", "-"): 0x0101,
+    ("A", "("): 0x0102,
+    ("a", "("): 0x0103,
+    ("A", ";"): 0x0104,
+    ("a", ";"): 0x0105,
+    ("C", "'"): 0x0106,
+    ("c", "'"): 0x0107,
+    ("C", ">"): 0x0108,
+    ("c", ">"): 0x0109,
+    ("C", "."): 0x010A,
+    ("c", "."): 0x010B,
+    ("C", "<"): 0x010C,
+    ("c", "<"): 0x010D,
+    ("D", "<"): 0x010E,
+    ("d", "<"): 0x010F,
+    ("D", "/"): 0x0110,
+    ("d", "/"): 0x0111,
+    ("E", "-"): 0x0112,
+    ("e", "-"): 0x0113,
+    ("E", "("): 0x0114,
+    ("e", "("): 0x0115,
+    ("E", "."): 0x0116,
+    ("e", "."): 0x0117,
+    ("E", ";"): 0x0118,
+    ("e", ";"): 0x0119,
+    ("E", "<"): 0x011A,
+    ("e", "<"): 0x011B,
+    ("G", ">"): 0x011C,
+    ("g", ">"): 0x011D,
+    ("G", "("): 0x011E,
+    ("g", "("): 0x011F,
+    ("G", "."): 0x0120,
+    ("g", "."): 0x0121,
+    ("G", ","): 0x0122,
+    ("g", ","): 0x0123,
+    ("H", ">"): 0x0124,
+    ("h", ">"): 0x0125,
+    ("H", "/"): 0x0126,
+    ("h", "/"): 0x0127,
+    ("I", "?"): 0x0128,
+    ("i", "?"): 0x0129,
+    ("I", "-"): 0x012A,
+    ("i", "-"): 0x012B,
+    ("I", "("): 0x012C,
+    ("i", "("): 0x012D,
+    ("I", ";"): 0x012E,
+    ("i", ";"): 0x012F,
+    ("I", "."): 0x0130,
+    ("i", "."): 0x0131,
+    ("I", "J"): 0x0132,
+    ("i", "j"): 0x0133,
+    ("J", ">"): 0x0134,
+    ("j", ">"): 0x0135,
+    ("K", ","): 0x0136,
+    ("k", ","): 0x0137,
+    ("k", "k"): 0x0138,
+    ("L", "'"): 0x0139,
+    ("l", "'"): 0x013A,
+    ("L", ","): 0x013B,
+    ("l", ","): 0x013C,
+    ("L", "<"): 0x013D,
+    ("l", "<"): 0x013E,
+    ("L", "."): 0x013F,
+    ("l", "."): 0x0140,
+    ("L", "/"): 0x0141,
+    ("l", "/"): 0x0142,
+    ("N", "'"): 0x0143,
+    ("n", "'"): 0x0144,
+    ("N", ","): 0x0145,
+    ("n", ","): 0x0146,
+    ("N", "<"): 0x0147,
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+    (")", "S"): 0x207E,
+    ("n", "S"): 0x207F,
+    ("0", "s"): 0x2080,
+    ("1", "s"): 0x2081,
+    ("2", "s"): 0x2082,
+    ("3", "s"): 0x2083,
+    ("4", "s"): 0x2084,
+    ("5", "s"): 0x2085,
+    ("6", "s"): 0x2086,
+    ("7", "s"): 0x2087,
+    ("8", "s"): 0x2088,
+    ("9", "s"): 0x2089,
+    ("+", "s"): 0x208A,
+    ("-", "s"): 0x208B,
+    ("=", "s"): 0x208C,
+    ("(", "s"): 0x208D,
+    (")", "s"): 0x208E,
+    ("L", "i"): 0x20A4,
+    ("P", "t"): 0x20A7,
+    ("W", "="): 0x20A9,
+    ("=", "e"): 0x20AC,  # euro
+    ("E", "u"): 0x20AC,  # euro
+    ("=", "R"): 0x20BD,  # rouble
+    ("=", "P"): 0x20BD,  # rouble
+    ("o", "C"): 0x2103,
+    ("c", "o"): 0x2105,
+    ("o", "F"): 0x2109,
+    ("N", "0"): 0x2116,
+    ("P", "O"): 0x2117,
+    ("R", "x"): 0x211E,
+    ("S", "M"): 0x2120,
+    ("T", "M"): 0x2122,
+    ("O", "m"): 0x2126,
+    ("A", "O"): 0x212B,
+    ("1", "3"): 0x2153,
+    ("2", "3"): 0x2154,
+    ("1", "5"): 0x2155,
+    ("2", "5"): 0x2156,
+    ("3", "5"): 0x2157,
+    ("4", "5"): 0x2158,
+    ("1", "6"): 0x2159,
+    ("5", "6"): 0x215A,
+    ("1", "8"): 0x215B,
+    ("3", "8"): 0x215C,
+    ("5", "8"): 0x215D,
+    ("7", "8"): 0x215E,
+    ("1", "R"): 0x2160,
+    ("2", "R"): 0x2161,
+    ("3", "R"): 0x2162,
+    ("4", "R"): 0x2163,
+    ("5", "R"): 0x2164,
+    ("6", "R"): 0x2165,
+    ("7", "R"): 0x2166,
+    ("8", "R"): 0x2167,
+    ("9", "R"): 0x2168,
+    ("a", "R"): 0x2169,
+    ("b", "R"): 0x216A,
+    ("c", "R"): 0x216B,
+    ("1", "r"): 0x2170,
+    ("2", "r"): 0x2171,
+    ("3", "r"): 0x2172,
+    ("4", "r"): 0x2173,
+    ("5", "r"): 0x2174,
+    ("6", "r"): 0x2175,
+    ("7", "r"): 0x2176,
+    ("8", "r"): 0x2177,
+    ("9", "r"): 0x2178,
+    ("a", "r"): 0x2179,
+    ("b", "r"): 0x217A,
+    ("c", "r"): 0x217B,
+    ("<", "-"): 0x2190,
+    ("-", "!"): 0x2191,
+    ("-", ">"): 0x2192,
+    ("-", "v"): 0x2193,
+    ("<", ">"): 0x2194,
+    ("U", "D"): 0x2195,
+    ("<", "="): 0x21D0,
+    ("=", ">"): 0x21D2,
+    ("=", "="): 0x21D4,
+    ("F", "A"): 0x2200,
+    ("d", "P"): 0x2202,
+    ("T", "E"): 0x2203,
+    ("/", "0"): 0x2205,
+    ("D", "E"): 0x2206,
+    ("N", "B"): 0x2207,
+    ("(", "-"): 0x2208,
+    ("-", ")"): 0x220B,
+    ("*", "P"): 0x220F,
+    ("+", "Z"): 0x2211,
+    ("-", "2"): 0x2212,
+    ("-", "+"): 0x2213,
+    ("*", "-"): 0x2217,
+    ("O", "b"): 0x2218,
+    ("S", "b"): 0x2219,
+    ("R", "T"): 0x221A,
+    ("0", "("): 0x221D,
+    ("0", "0"): 0x221E,
+    ("-", "L"): 0x221F,
+    ("-", "V"): 0x2220,
+    ("P", "P"): 0x2225,
+    ("A", "N"): 0x2227,
+    ("O", "R"): 0x2228,
+    ("(", "U"): 0x2229,
+    (")", "U"): 0x222A,
+    ("I", "n"): 0x222B,
+    ("D", "I"): 0x222C,
+    ("I", "o"): 0x222E,
+    (".", ":"): 0x2234,
+    (":", "."): 0x2235,
+    (":", "R"): 0x2236,
+    (":", ":"): 0x2237,
+    ("?", "1"): 0x223C,
+    ("C", "G"): 0x223E,
+    ("?", "-"): 0x2243,
+    ("?", "="): 0x2245,
+    ("?", "2"): 0x2248,
+    ("=", "?"): 0x224C,
+    ("H", "I"): 0x2253,
+    ("!", "="): 0x2260,
+    ("=", "3"): 0x2261,
+    ("=", "<"): 0x2264,
+    (">", "="): 0x2265,
+    ("<", "*"): 0x226A,
+    ("*", ">"): 0x226B,
+    ("!", "<"): 0x226E,
+    ("!", ">"): 0x226F,
+    ("(", "C"): 0x2282,
+    (")", "C"): 0x2283,
+    ("(", "_"): 0x2286,
+    (")", "_"): 0x2287,
+    ("0", "."): 0x2299,
+    ("0", "2"): 0x229A,
+    ("-", "T"): 0x22A5,
+    (".", "P"): 0x22C5,
+    (":", "3"): 0x22EE,
+    (".", "3"): 0x22EF,
+    ("E", "h"): 0x2302,
+    ("<", "7"): 0x2308,
+    (">", "7"): 0x2309,
+    ("7", "<"): 0x230A,
+    ("7", ">"): 0x230B,
+    ("N", "I"): 0x2310,
+    ("(", "A"): 0x2312,
+    ("T", "R"): 0x2315,
+    ("I", "u"): 0x2320,
+    ("I", "l"): 0x2321,
+    ("<", "/"): 0x2329,
+    ("/", ">"): 0x232A,
+    ("V", "s"): 0x2423,
+    ("1", "h"): 0x2440,
+    ("3", "h"): 0x2441,
+    ("2", "h"): 0x2442,
+    ("4", "h"): 0x2443,
+    ("1", "j"): 0x2446,
+    ("2", "j"): 0x2447,
+    ("3", "j"): 0x2448,
+    ("4", "j"): 0x2449,
+    ("1", "."): 0x2488,
+    ("2", "."): 0x2489,
+    ("3", "."): 0x248A,
+    ("4", "."): 0x248B,
+    ("5", "."): 0x248C,
+    ("6", "."): 0x248D,
+    ("7", "."): 0x248E,
+    ("8", "."): 0x248F,
+    ("9", "."): 0x2490,
+    ("h", "h"): 0x2500,
+    ("H", "H"): 0x2501,
+    ("v", "v"): 0x2502,
+    ("V", "V"): 0x2503,
+    ("3", "-"): 0x2504,
+    ("3", "_"): 0x2505,
+    ("3", "!"): 0x2506,
+    ("3", "/"): 0x2507,
+    ("4", "-"): 0x2508,
+    ("4", "_"): 0x2509,
+    ("4", "!"): 0x250A,
+    ("4", "/"): 0x250B,
+    ("d", "r"): 0x250C,
+    ("d", "R"): 0x250D,
+    ("D", "r"): 0x250E,
+    ("D", "R"): 0x250F,
+    ("d", "l"): 0x2510,
+    ("d", "L"): 0x2511,
+    ("D", "l"): 0x2512,
+    ("L", "D"): 0x2513,
+    ("u", "r"): 0x2514,
+    ("u", "R"): 0x2515,
+    ("U", "r"): 0x2516,
+    ("U", "R"): 0x2517,
+    ("u", "l"): 0x2518,
+    ("u", "L"): 0x2519,
+    ("U", "l"): 0x251A,
+    ("U", "L"): 0x251B,
+    ("v", "r"): 0x251C,
+    ("v", "R"): 0x251D,
+    ("V", "r"): 0x2520,
+    ("V", "R"): 0x2523,
+    ("v", "l"): 0x2524,
+    ("v", "L"): 0x2525,
+    ("V", "l"): 0x2528,
+    ("V", "L"): 0x252B,
+    ("d", "h"): 0x252C,
+    ("d", "H"): 0x252F,
+    ("D", "h"): 0x2530,
+    ("D", "H"): 0x2533,
+    ("u", "h"): 0x2534,
+    ("u", "H"): 0x2537,
+    ("U", "h"): 0x2538,
+    ("U", "H"): 0x253B,
+    ("v", "h"): 0x253C,
+    ("v", "H"): 0x253F,
+    ("V", "h"): 0x2542,
+    ("V", "H"): 0x254B,
+    ("F", "D"): 0x2571,
+    ("B", "D"): 0x2572,
+    ("T", "B"): 0x2580,
+    ("L", "B"): 0x2584,
+    ("F", "B"): 0x2588,
+    ("l", "B"): 0x258C,
+    ("R", "B"): 0x2590,
+    (".", "S"): 0x2591,
+    (":", "S"): 0x2592,
+    ("?", "S"): 0x2593,
+    ("f", "S"): 0x25A0,
+    ("O", "S"): 0x25A1,
+    ("R", "O"): 0x25A2,
+    ("R", "r"): 0x25A3,
+    ("R", "F"): 0x25A4,
+    ("R", "Y"): 0x25A5,
+    ("R", "H"): 0x25A6,
+    ("R", "Z"): 0x25A7,
+    ("R", "K"): 0x25A8,
+    ("R", "X"): 0x25A9,
+    ("s", "B"): 0x25AA,
+    ("S", "R"): 0x25AC,
+    ("O", "r"): 0x25AD,
+    ("U", "T"): 0x25B2,
+    ("u", "T"): 0x25B3,
+    ("P", "R"): 0x25B6,
+    ("T", "r"): 0x25B7,
+    ("D", "t"): 0x25BC,
+    ("d", "T"): 0x25BD,
+    ("P", "L"): 0x25C0,
+    ("T", "l"): 0x25C1,
+    ("D", "b"): 0x25C6,
+    ("D", "w"): 0x25C7,
+    ("L", "Z"): 0x25CA,
+    ("0", "m"): 0x25CB,
+    ("0", "o"): 0x25CE,
+    ("0", "M"): 0x25CF,
+    ("0", "L"): 0x25D0,
+    ("0", "R"): 0x25D1,
+    ("S", "n"): 0x25D8,
+    ("I", "c"): 0x25D9,
+    ("F", "d"): 0x25E2,
+    ("B", "d"): 0x25E3,
+    ("*", "2"): 0x2605,
+    ("*", "1"): 0x2606,
+    ("<", "H"): 0x261C,
+    (">", "H"): 0x261E,
+    ("0", "u"): 0x263A,
+    ("0", "U"): 0x263B,
+    ("S", "U"): 0x263C,
+    ("F", "m"): 0x2640,
+    ("M", "l"): 0x2642,
+    ("c", "S"): 0x2660,
+    ("c", "H"): 0x2661,
+    ("c", "D"): 0x2662,
+    ("c", "C"): 0x2663,
+    ("M", "d"): 0x2669,
+    ("M", "8"): 0x266A,
+    ("M", "2"): 0x266B,
+    ("M", "b"): 0x266D,
+    ("M", "x"): 0x266E,
+    ("M", "X"): 0x266F,
+    ("O", "K"): 0x2713,
+    ("X", "X"): 0x2717,
+    ("-", "X"): 0x2720,
+    ("I", "S"): 0x3000,
+    (",", "_"): 0x3001,
+    (".", "_"): 0x3002,
+    ("+", '"'): 0x3003,
+    ("+", "_"): 0x3004,
+    ("*", "_"): 0x3005,
+    (";", "_"): 0x3006,
+    ("0", "_"): 0x3007,
+    ("<", "+"): 0x300A,
+    (">", "+"): 0x300B,
+    ("<", "'"): 0x300C,
+    (">", "'"): 0x300D,
+    ("<", '"'): 0x300E,
+    (">", '"'): 0x300F,
+    ("(", '"'): 0x3010,
+    (")", '"'): 0x3011,
+    ("=", "T"): 0x3012,
+    ("=", "_"): 0x3013,
+    ("(", "'"): 0x3014,
+    (")", "'"): 0x3015,
+    ("(", "I"): 0x3016,
+    (")", "I"): 0x3017,
+    ("-", "?"): 0x301C,
+    ("A", "5"): 0x3041,
+    ("a", "5"): 0x3042,
+    ("I", "5"): 0x3043,
+    ("i", "5"): 0x3044,
+    ("U", "5"): 0x3045,
+    ("u", "5"): 0x3046,
+    ("E", "5"): 0x3047,
+    ("e", "5"): 0x3048,
+    ("O", "5"): 0x3049,
+    ("o", "5"): 0x304A,
+    ("k", "a"): 0x304B,
+    ("g", "a"): 0x304C,
+    ("k", "i"): 0x304D,
+    ("g", "i"): 0x304E,
+    ("k", "u"): 0x304F,
+    ("g", "u"): 0x3050,
+    ("k", "e"): 0x3051,
+    ("g", "e"): 0x3052,
+    ("k", "o"): 0x3053,
+    ("g", "o"): 0x3054,
+    ("s", "a"): 0x3055,
+    ("z", "a"): 0x3056,
+    ("s", "i"): 0x3057,
+    ("z", "i"): 0x3058,
+    ("s", "u"): 0x3059,
+    ("z", "u"): 0x305A,
+    ("s", "e"): 0x305B,
+    ("z", "e"): 0x305C,
+    ("s", "o"): 0x305D,
+    ("z", "o"): 0x305E,
+    ("t", "a"): 0x305F,
+    ("d", "a"): 0x3060,
+    ("t", "i"): 0x3061,
+    ("d", "i"): 0x3062,
+    ("t", "U"): 0x3063,
+    ("t", "u"): 0x3064,
+    ("d", "u"): 0x3065,
+    ("t", "e"): 0x3066,
+    ("d", "e"): 0x3067,
+    ("t", "o"): 0x3068,
+    ("d", "o"): 0x3069,
+    ("n", "a"): 0x306A,
+    ("n", "i"): 0x306B,
+    ("n", "u"): 0x306C,
+    ("n", "e"): 0x306D,
+    ("n", "o"): 0x306E,
+    ("h", "a"): 0x306F,
+    ("b", "a"): 0x3070,
+    ("p", "a"): 0x3071,
+    ("h", "i"): 0x3072,
+    ("b", "i"): 0x3073,
+    ("p", "i"): 0x3074,
+    ("h", "u"): 0x3075,
+    ("b", "u"): 0x3076,
+    ("p", "u"): 0x3077,
+    ("h", "e"): 0x3078,
+    ("b", "e"): 0x3079,
+    ("p", "e"): 0x307A,
+    ("h", "o"): 0x307B,
+    ("b", "o"): 0x307C,
+    ("p", "o"): 0x307D,
+    ("m", "a"): 0x307E,
+    ("m", "i"): 0x307F,
+    ("m", "u"): 0x3080,
+    ("m", "e"): 0x3081,
+    ("m", "o"): 0x3082,
+    ("y", "A"): 0x3083,
+    ("y", "a"): 0x3084,
+    ("y", "U"): 0x3085,
+    ("y", "u"): 0x3086,
+    ("y", "O"): 0x3087,
+    ("y", "o"): 0x3088,
+    ("r", "a"): 0x3089,
+    ("r", "i"): 0x308A,
+    ("r", "u"): 0x308B,
+    ("r", "e"): 0x308C,
+    ("r", "o"): 0x308D,
+    ("w", "A"): 0x308E,
+    ("w", "a"): 0x308F,
+    ("w", "i"): 0x3090,
+    ("w", "e"): 0x3091,
+    ("w", "o"): 0x3092,
+    ("n", "5"): 0x3093,
+    ("v", "u"): 0x3094,
+    ('"', "5"): 0x309B,
+    ("0", "5"): 0x309C,
+    ("*", "5"): 0x309D,
+    ("+", "5"): 0x309E,
+    ("a", "6"): 0x30A1,
+    ("A", "6"): 0x30A2,
+    ("i", "6"): 0x30A3,
+    ("I", "6"): 0x30A4,
+    ("u", "6"): 0x30A5,
+    ("U", "6"): 0x30A6,
+    ("e", "6"): 0x30A7,
+    ("E", "6"): 0x30A8,
+    ("o", "6"): 0x30A9,
+    ("O", "6"): 0x30AA,
+    ("K", "a"): 0x30AB,
+    ("G", "a"): 0x30AC,
+    ("K", "i"): 0x30AD,
+    ("G", "i"): 0x30AE,
+    ("K", "u"): 0x30AF,
+    ("G", "u"): 0x30B0,
+    ("K", "e"): 0x30B1,
+    ("G", "e"): 0x30B2,
+    ("K", "o"): 0x30B3,
+    ("G", "o"): 0x30B4,
+    ("S", "a"): 0x30B5,
+    ("Z", "a"): 0x30B6,
+    ("S", "i"): 0x30B7,
+    ("Z", "i"): 0x30B8,
+    ("S", "u"): 0x30B9,
+    ("Z", "u"): 0x30BA,
+    ("S", "e"): 0x30BB,
+    ("Z", "e"): 0x30BC,
+    ("S", "o"): 0x30BD,
+    ("Z", "o"): 0x30BE,
+    ("T", "a"): 0x30BF,
+    ("D", "a"): 0x30C0,
+    ("T", "i"): 0x30C1,
+    ("D", "i"): 0x30C2,
+    ("T", "U"): 0x30C3,
+    ("T", "u"): 0x30C4,
+    ("D", "u"): 0x30C5,
+    ("T", "e"): 0x30C6,
+    ("D", "e"): 0x30C7,
+    ("T", "o"): 0x30C8,
+    ("D", "o"): 0x30C9,
+    ("N", "a"): 0x30CA,
+    ("N", "i"): 0x30CB,
+    ("N", "u"): 0x30CC,
+    ("N", "e"): 0x30CD,
+    ("N", "o"): 0x30CE,
+    ("H", "a"): 0x30CF,
+    ("B", "a"): 0x30D0,
+    ("P", "a"): 0x30D1,
+    ("H", "i"): 0x30D2,
+    ("B", "i"): 0x30D3,
+    ("P", "i"): 0x30D4,
+    ("H", "u"): 0x30D5,
+    ("B", "u"): 0x30D6,
+    ("P", "u"): 0x30D7,
+    ("H", "e"): 0x30D8,
+    ("B", "e"): 0x30D9,
+    ("P", "e"): 0x30DA,
+    ("H", "o"): 0x30DB,
+    ("B", "o"): 0x30DC,
+    ("P", "o"): 0x30DD,
+    ("M", "a"): 0x30DE,
+    ("M", "i"): 0x30DF,
+    ("M", "u"): 0x30E0,
+    ("M", "e"): 0x30E1,
+    ("M", "o"): 0x30E2,
+    ("Y", "A"): 0x30E3,
+    ("Y", "a"): 0x30E4,
+    ("Y", "U"): 0x30E5,
+    ("Y", "u"): 0x30E6,
+    ("Y", "O"): 0x30E7,
+    ("Y", "o"): 0x30E8,
+    ("R", "a"): 0x30E9,
+    ("R", "i"): 0x30EA,
+    ("R", "u"): 0x30EB,
+    ("R", "e"): 0x30EC,
+    ("R", "o"): 0x30ED,
+    ("W", "A"): 0x30EE,
+    ("W", "a"): 0x30EF,
+    ("W", "i"): 0x30F0,
+    ("W", "e"): 0x30F1,
+    ("W", "o"): 0x30F2,
+    ("N", "6"): 0x30F3,
+    ("V", "u"): 0x30F4,
+    ("K", "A"): 0x30F5,
+    ("K", "E"): 0x30F6,
+    ("V", "a"): 0x30F7,
+    ("V", "i"): 0x30F8,
+    ("V", "e"): 0x30F9,
+    ("V", "o"): 0x30FA,
+    (".", "6"): 0x30FB,
+    ("-", "6"): 0x30FC,
+    ("*", "6"): 0x30FD,
+    ("+", "6"): 0x30FE,
+    ("b", "4"): 0x3105,
+    ("p", "4"): 0x3106,
+    ("m", "4"): 0x3107,
+    ("f", "4"): 0x3108,
+    ("d", "4"): 0x3109,
+    ("t", "4"): 0x310A,
+    ("n", "4"): 0x310B,
+    ("l", "4"): 0x310C,
+    ("g", "4"): 0x310D,
+    ("k", "4"): 0x310E,
+    ("h", "4"): 0x310F,
+    ("j", "4"): 0x3110,
+    ("q", "4"): 0x3111,
+    ("x", "4"): 0x3112,
+    ("z", "h"): 0x3113,
+    ("c", "h"): 0x3114,
+    ("s", "h"): 0x3115,
+    ("r", "4"): 0x3116,
+    ("z", "4"): 0x3117,
+    ("c", "4"): 0x3118,
+    ("s", "4"): 0x3119,
+    ("a", "4"): 0x311A,
+    ("o", "4"): 0x311B,
+    ("e", "4"): 0x311C,
+    ("a", "i"): 0x311E,
+    ("e", "i"): 0x311F,
+    ("a", "u"): 0x3120,
+    ("o", "u"): 0x3121,
+    ("a", "n"): 0x3122,
+    ("e", "n"): 0x3123,
+    ("a", "N"): 0x3124,
+    ("e", "N"): 0x3125,
+    ("e", "r"): 0x3126,
+    ("i", "4"): 0x3127,
+    ("u", "4"): 0x3128,
+    ("i", "u"): 0x3129,
+    ("v", "4"): 0x312A,
+    ("n", "G"): 0x312B,
+    ("g", "n"): 0x312C,
+    ("1", "c"): 0x3220,
+    ("2", "c"): 0x3221,
+    ("3", "c"): 0x3222,
+    ("4", "c"): 0x3223,
+    ("5", "c"): 0x3224,
+    ("6", "c"): 0x3225,
+    ("7", "c"): 0x3226,
+    ("8", "c"): 0x3227,
+    ("9", "c"): 0x3228,
+    # code points 0xe000 - 0xefff excluded, they have no assigned
+    # characters, only used in proposals.
+    ("f", "f"): 0xFB00,
+    ("f", "i"): 0xFB01,
+    ("f", "l"): 0xFB02,
+    ("f", "t"): 0xFB05,
+    ("s", "t"): 0xFB06,
+    # Vim 5.x compatible digraphs that don't conflict with the above
+    ("~", "!"): 161,
+    ("c", "|"): 162,
+    ("$", "$"): 163,
+    ("o", "x"): 164,  # currency symbol in ISO 8859-1
+    ("Y", "-"): 165,
+    ("|", "|"): 166,
+    ("c", "O"): 169,
+    ("-", ","): 172,
+    ("-", "="): 175,
+    ("~", "o"): 176,
+    ("2", "2"): 178,
+    ("3", "3"): 179,
+    ("p", "p"): 182,
+    ("~", "."): 183,
+    ("1", "1"): 185,
+    ("~", "?"): 191,
+    ("A", "`"): 192,
+    ("A", "^"): 194,
+    ("A", "~"): 195,
+    ("A", '"'): 196,
+    ("A", "@"): 197,
+    ("E", "`"): 200,
+    ("E", "^"): 202,
+    ("E", '"'): 203,
+    ("I", "`"): 204,
+    ("I", "^"): 206,
+    ("I", '"'): 207,
+    ("N", "~"): 209,
+    ("O", "`"): 210,
+    ("O", "^"): 212,
+    ("O", "~"): 213,
+    ("/", "\\"): 215,  # multiplication symbol in ISO 8859-1
+    ("U", "`"): 217,
+    ("U", "^"): 219,
+    ("I", "p"): 222,
+    ("a", "`"): 224,
+    ("a", "^"): 226,
+    ("a", "~"): 227,
+    ("a", '"'): 228,
+    ("a", "@"): 229,
+    ("e", "`"): 232,
+    ("e", "^"): 234,
+    ("e", '"'): 235,
+    ("i", "`"): 236,
+    ("i", "^"): 238,
+    ("n", "~"): 241,
+    ("o", "`"): 242,
+    ("o", "^"): 244,
+    ("o", "~"): 245,
+    ("u", "`"): 249,
+    ("u", "^"): 251,
+    ("y", '"'): 255,
+}
diff --git a/src/prompt_toolkit/key_binding/emacs_state.py b/src/prompt_toolkit/key_binding/emacs_state.py
new file mode 100644
index 0000000..4c99622
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/emacs_state.py
@@ -0,0 +1,36 @@
+from typing import List, Optional
+
+from .key_processor import KeyPress
+
+__all__ = [
+    "EmacsState",
+]
+
+
+class EmacsState:
+    """
+    Mutable class to hold Emacs specific state.
+    """
+
+    def __init__(self) -> None:
+        # Simple macro recording. (Like Readline does.)
+        # (For Emacs mode.)
+        self.macro: Optional[List[KeyPress]] = []
+        self.current_recording: Optional[List[KeyPress]] = None
+
+    def reset(self) -> None:
+        self.current_recording = None
+
+    @property
+    def is_recording(self) -> bool:
+        "Tell whether we are recording a macro."
+        return self.current_recording is not None
+
+    def start_macro(self) -> None:
+        "Start recording macro."
+        self.current_recording = []
+
+    def end_macro(self) -> None:
+        "End recording macro."
+        self.macro = self.current_recording
+        self.current_recording = None
diff --git a/src/prompt_toolkit/key_binding/key_bindings.py b/src/prompt_toolkit/key_binding/key_bindings.py
new file mode 100644
index 0000000..03bc79e
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/key_bindings.py
@@ -0,0 +1,672 @@
+"""
+Key bindings registry.
+
+A `KeyBindings` object is a container that holds a list of key bindings. It has a
+very efficient internal data structure for checking which key bindings apply
+for a pressed key.
+
+Typical usage::
+
+    kb = KeyBindings()
+
+    @kb.add(Keys.ControlX, Keys.ControlC, filter=INSERT)
+    def handler(event):
+        # Handle ControlX-ControlC key sequence.
+        pass
+
+It is also possible to combine multiple KeyBindings objects. We do this in the
+default key bindings. There are some KeyBindings objects that contain the Emacs
+bindings, while others contain the Vi bindings. They are merged together using
+`merge_key_bindings`.
+
+We also have a `ConditionalKeyBindings` object that can enable/disable a group of
+key bindings at once.
+
+
+It is also possible to add a filter to a function, before a key binding has
+been assigned, through the `key_binding` decorator.::
+
+    # First define a key handler with the `filter`.
+    @key_binding(filter=condition)
+    def my_key_binding(event):
+        ...
+
+    # Later, add it to the key bindings.
+    kb.add(Keys.A, my_key_binding)
+"""
+from abc import ABCMeta, abstractmethod, abstractproperty
+from inspect import isawaitable
+from typing import (
+    TYPE_CHECKING,
+    Awaitable,
+    Callable,
+    Hashable,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    TypeVar,
+    Union,
+    cast,
+)
+
+from prompt_toolkit.cache import SimpleCache
+from prompt_toolkit.filters import FilterOrBool, Never, to_filter
+from prompt_toolkit.keys import KEY_ALIASES, Keys
+
+if TYPE_CHECKING:
+    # Avoid circular imports.
+    from .key_processor import KeyPressEvent
+
+    # The only two return values for a mouse hander (and key bindings) are
+    # `None` and `NotImplemented`. For the type checker it's best to annotate
+    # this as `object`. (The consumer never expects a more specific instance:
+    # checking for NotImplemented can be done using `is NotImplemented`.)
+    NotImplementedOrNone = object
+    # Other non-working options are:
+    # * Optional[Literal[NotImplemented]]
+    #      --> Doesn't work, Literal can't take an Any.
+    # * None
+    #      --> Doesn't work. We can't assign the result of a function that
+    #          returns `None` to a variable.
+    # * Any
+    #      --> Works, but too broad.
+
+
+__all__ = [
+    "NotImplementedOrNone",
+    "Binding",
+    "KeyBindingsBase",
+    "KeyBindings",
+    "ConditionalKeyBindings",
+    "merge_key_bindings",
+    "DynamicKeyBindings",
+    "GlobalOnlyKeyBindings",
+]
+
+# Key bindings can be regular functions or coroutines.
+# In both cases, if they return `NotImplemented`, the UI won't be invalidated.
+# This is mainly used in case of mouse move events, to prevent excessive
+# repainting during mouse move events.
+KeyHandlerCallable = Callable[
+    ["KeyPressEvent"], Union["NotImplementedOrNone", Awaitable["NotImplementedOrNone"]]
+]
+
+
+class Binding:
+    """
+    Key binding: (key sequence + handler + filter).
+    (Immutable binding class.)
+
+    :param record_in_macro: When True, don't record this key binding when a
+        macro is recorded.
+    """
+
+    def __init__(
+        self,
+        keys: Tuple[Union[Keys, str], ...],
+        handler: KeyHandlerCallable,
+        filter: FilterOrBool = True,
+        eager: FilterOrBool = False,
+        is_global: FilterOrBool = False,
+        save_before: Callable[["KeyPressEvent"], bool] = (lambda e: True),
+        record_in_macro: FilterOrBool = True,
+    ) -> None:
+        self.keys = keys
+        self.handler = handler
+        self.filter = to_filter(filter)
+        self.eager = to_filter(eager)
+        self.is_global = to_filter(is_global)
+        self.save_before = save_before
+        self.record_in_macro = to_filter(record_in_macro)
+
+    def call(self, event: "KeyPressEvent") -> None:
+        result = self.handler(event)
+
+        # If the handler is a coroutine, create an asyncio task.
+        if isawaitable(result):
+            awaitable = cast(Awaitable["NotImplementedOrNone"], result)
+
+            async def bg_task() -> None:
+                result = await awaitable
+                if result != NotImplemented:
+                    event.app.invalidate()
+
+            event.app.create_background_task(bg_task())
+
+        elif result != NotImplemented:
+            event.app.invalidate()
+
+    def __repr__(self) -> str:
+        return "{}(keys={!r}, handler={!r})".format(
+            self.__class__.__name__,
+            self.keys,
+            self.handler,
+        )
+
+
+# Sequence of keys presses.
+KeysTuple = Tuple[Union[Keys, str], ...]
+
+
+class KeyBindingsBase(metaclass=ABCMeta):
+    """
+    Interface for a KeyBindings.
+    """
+
+    @abstractproperty
+    def _version(self) -> Hashable:
+        """
+        For cache invalidation. - This should increase every time that
+        something changes.
+        """
+        return 0
+
+    @abstractmethod
+    def get_bindings_for_keys(self, keys: KeysTuple) -> List[Binding]:
+        """
+        Return a list of key bindings that can handle these keys.
+        (This return also inactive bindings, so the `filter` still has to be
+        called, for checking it.)
+
+        :param keys: tuple of keys.
+        """
+        return []
+
+    @abstractmethod
+    def get_bindings_starting_with_keys(self, keys: KeysTuple) -> List[Binding]:
+        """
+        Return a list of key bindings that handle a key sequence starting with
+        `keys`. (It does only return bindings for which the sequences are
+        longer than `keys`. And like `get_bindings_for_keys`, it also includes
+        inactive bindings.)
+
+        :param keys: tuple of keys.
+        """
+        return []
+
+    @abstractproperty
+    def bindings(self) -> List[Binding]:
+        """
+        List of `Binding` objects.
+        (These need to be exposed, so that `KeyBindings` objects can be merged
+        together.)
+        """
+        return []
+
+    # `add` and `remove` don't have to be part of this interface.
+
+
+T = TypeVar("T", bound=Union[KeyHandlerCallable, Binding])
+
+
+class KeyBindings(KeyBindingsBase):
+    """
+    A container for a set of key bindings.
+
+    Example usage::
+
+        kb = KeyBindings()
+
+        @kb.add('c-t')
+        def _(event):
+            print('Control-T pressed')
+
+        @kb.add('c-a', 'c-b')
+        def _(event):
+            print('Control-A pressed, followed by Control-B')
+
+        @kb.add('c-x', filter=is_searching)
+        def _(event):
+            print('Control-X pressed')  # Works only if we are searching.
+
+    """
+
+    def __init__(self) -> None:
+        self._bindings: List[Binding] = []
+        self._get_bindings_for_keys_cache: SimpleCache[
+            KeysTuple, List[Binding]
+        ] = SimpleCache(maxsize=10000)
+        self._get_bindings_starting_with_keys_cache: SimpleCache[
+            KeysTuple, List[Binding]
+        ] = SimpleCache(maxsize=1000)
+        self.__version = 0  # For cache invalidation.
+
+    def _clear_cache(self) -> None:
+        self.__version += 1
+        self._get_bindings_for_keys_cache.clear()
+        self._get_bindings_starting_with_keys_cache.clear()
+
+    @property
+    def bindings(self) -> List[Binding]:
+        return self._bindings
+
+    @property
+    def _version(self) -> Hashable:
+        return self.__version
+
+    def add(
+        self,
+        *keys: Union[Keys, str],
+        filter: FilterOrBool = True,
+        eager: FilterOrBool = False,
+        is_global: FilterOrBool = False,
+        save_before: Callable[["KeyPressEvent"], bool] = (lambda e: True),
+        record_in_macro: FilterOrBool = True,
+    ) -> Callable[[T], T]:
+        """
+        Decorator for adding a key bindings.
+
+        :param filter: :class:`~prompt_toolkit.filters.Filter` to determine
+            when this key binding is active.
+        :param eager: :class:`~prompt_toolkit.filters.Filter` or `bool`.
+            When True, ignore potential longer matches when this key binding is
+            hit. E.g. when there is an active eager key binding for Ctrl-X,
+            execute the handler immediately and ignore the key binding for
+            Ctrl-X Ctrl-E of which it is a prefix.
+        :param is_global: When this key bindings is added to a `Container` or
+            `Control`, make it a global (always active) binding.
+        :param save_before: Callable that takes an `Event` and returns True if
+            we should save the current buffer, before handling the event.
+            (That's the default.)
+        :param record_in_macro: Record these key bindings when a macro is
+            being recorded. (True by default.)
+        """
+        assert keys
+
+        keys = tuple(_parse_key(k) for k in keys)
+
+        if isinstance(filter, Never):
+            # When a filter is Never, it will always stay disabled, so in that
+            # case don't bother putting it in the key bindings. It will slow
+            # down every key press otherwise.
+            def decorator(func: T) -> T:
+                return func
+
+        else:
+
+            def decorator(func: T) -> T:
+                if isinstance(func, Binding):
+                    # We're adding an existing Binding object.
+                    self.bindings.append(
+                        Binding(
+                            keys,
+                            func.handler,
+                            filter=func.filter & to_filter(filter),
+                            eager=to_filter(eager) | func.eager,
+                            is_global=to_filter(is_global) | func.is_global,
+                            save_before=func.save_before,
+                            record_in_macro=func.record_in_macro,
+                        )
+                    )
+                else:
+                    self.bindings.append(
+                        Binding(
+                            keys,
+                            cast(KeyHandlerCallable, func),
+                            filter=filter,
+                            eager=eager,
+                            is_global=is_global,
+                            save_before=save_before,
+                            record_in_macro=record_in_macro,
+                        )
+                    )
+                self._clear_cache()
+
+                return func
+
+        return decorator
+
+    def remove(self, *args: Union[Keys, str, KeyHandlerCallable]) -> None:
+        """
+        Remove a key binding.
+
+        This expects either a function that was given to `add` method as
+        parameter or a sequence of key bindings.
+
+        Raises `ValueError` when no bindings was found.
+
+        Usage::
+
+            remove(handler)  # Pass handler.
+            remove('c-x', 'c-a')  # Or pass the key bindings.
+        """
+        found = False
+
+        if callable(args[0]):
+            assert len(args) == 1
+            function = args[0]
+
+            # Remove the given function.
+            for b in self.bindings:
+                if b.handler == function:
+                    self.bindings.remove(b)
+                    found = True
+
+        else:
+            assert len(args) > 0
+            args = cast(Tuple[Union[Keys, str]], args)
+
+            # Remove this sequence of key bindings.
+            keys = tuple(_parse_key(k) for k in args)
+
+            for b in self.bindings:
+                if b.keys == keys:
+                    self.bindings.remove(b)
+                    found = True
+
+        if found:
+            self._clear_cache()
+        else:
+            # No key binding found for this function. Raise ValueError.
+            raise ValueError(f"Binding not found: {function!r}")
+
+    # For backwards-compatibility.
+    add_binding = add
+    remove_binding = remove
+
+    def get_bindings_for_keys(self, keys: KeysTuple) -> List[Binding]:
+        """
+        Return a list of key bindings that can handle this key.
+        (This return also inactive bindings, so the `filter` still has to be
+        called, for checking it.)
+
+        :param keys: tuple of keys.
+        """
+
+        def get() -> List[Binding]:
+            result: List[Tuple[int, Binding]] = []
+
+            for b in self.bindings:
+                if len(keys) == len(b.keys):
+                    match = True
+                    any_count = 0
+
+                    for i, j in zip(b.keys, keys):
+                        if i != j and i != Keys.Any:
+                            match = False
+                            break
+
+                        if i == Keys.Any:
+                            any_count += 1
+
+                    if match:
+                        result.append((any_count, b))
+
+            # Place bindings that have more 'Any' occurrences in them at the end.
+            result = sorted(result, key=lambda item: -item[0])
+
+            return [item[1] for item in result]
+
+        return self._get_bindings_for_keys_cache.get(keys, get)
+
+    def get_bindings_starting_with_keys(self, keys: KeysTuple) -> List[Binding]:
+        """
+        Return a list of key bindings that handle a key sequence starting with
+        `keys`. (It does only return bindings for which the sequences are
+        longer than `keys`. And like `get_bindings_for_keys`, it also includes
+        inactive bindings.)
+
+        :param keys: tuple of keys.
+        """
+
+        def get() -> List[Binding]:
+            result = []
+            for b in self.bindings:
+                if len(keys) < len(b.keys):
+                    match = True
+                    for i, j in zip(b.keys, keys):
+                        if i != j and i != Keys.Any:
+                            match = False
+                            break
+                    if match:
+                        result.append(b)
+            return result
+
+        return self._get_bindings_starting_with_keys_cache.get(keys, get)
+
+
+def _parse_key(key: Union[Keys, str]) -> Union[str, Keys]:
+    """
+    Replace key by alias and verify whether it's a valid one.
+    """
+    # Already a parse key? -> Return it.
+    if isinstance(key, Keys):
+        return key
+
+    # Lookup aliases.
+    key = KEY_ALIASES.get(key, key)
+
+    # Replace 'space' by ' '
+    if key == "space":
+        key = " "
+
+    # Return as `Key` object when it's a special key.
+    try:
+        return Keys(key)
+    except ValueError:
+        pass
+
+    # Final validation.
+    if len(key) != 1:
+        raise ValueError(f"Invalid key: {key}")
+
+    return key
+
+
+def key_binding(
+    filter: FilterOrBool = True,
+    eager: FilterOrBool = False,
+    is_global: FilterOrBool = False,
+    save_before: Callable[["KeyPressEvent"], bool] = (lambda event: True),
+    record_in_macro: FilterOrBool = True,
+) -> Callable[[KeyHandlerCallable], Binding]:
+    """
+    Decorator that turn a function into a `Binding` object. This can be added
+    to a `KeyBindings` object when a key binding is assigned.
+    """
+    assert save_before is None or callable(save_before)
+
+    filter = to_filter(filter)
+    eager = to_filter(eager)
+    is_global = to_filter(is_global)
+    save_before = save_before
+    record_in_macro = to_filter(record_in_macro)
+    keys = ()
+
+    def decorator(function: KeyHandlerCallable) -> Binding:
+        return Binding(
+            keys,
+            function,
+            filter=filter,
+            eager=eager,
+            is_global=is_global,
+            save_before=save_before,
+            record_in_macro=record_in_macro,
+        )
+
+    return decorator
+
+
+class _Proxy(KeyBindingsBase):
+    """
+    Common part for ConditionalKeyBindings and _MergedKeyBindings.
+    """
+
+    def __init__(self) -> None:
+        # `KeyBindings` to be synchronized with all the others.
+        self._bindings2: KeyBindingsBase = KeyBindings()
+        self._last_version: Hashable = ()
+
+    def _update_cache(self) -> None:
+        """
+        If `self._last_version` is outdated, then this should update
+        the version and `self._bindings2`.
+        """
+        raise NotImplementedError
+
+    # Proxy methods to self._bindings2.
+
+    @property
+    def bindings(self) -> List[Binding]:
+        self._update_cache()
+        return self._bindings2.bindings
+
+    @property
+    def _version(self) -> Hashable:
+        self._update_cache()
+        return self._last_version
+
+    def get_bindings_for_keys(self, keys: KeysTuple) -> List[Binding]:
+        self._update_cache()
+        return self._bindings2.get_bindings_for_keys(keys)
+
+    def get_bindings_starting_with_keys(self, keys: KeysTuple) -> List[Binding]:
+        self._update_cache()
+        return self._bindings2.get_bindings_starting_with_keys(keys)
+
+
+class ConditionalKeyBindings(_Proxy):
+    """
+    Wraps around a `KeyBindings`. Disable/enable all the key bindings according to
+    the given (additional) filter.::
+
+        @Condition
+        def setting_is_true():
+            return True  # or False
+
+        registry = ConditionalKeyBindings(key_bindings, setting_is_true)
+
+    When new key bindings are added to this object. They are also
+    enable/disabled according to the given `filter`.
+
+    :param registries: List of :class:`.KeyBindings` objects.
+    :param filter: :class:`~prompt_toolkit.filters.Filter` object.
+    """
+
+    def __init__(
+        self, key_bindings: KeyBindingsBase, filter: FilterOrBool = True
+    ) -> None:
+
+        _Proxy.__init__(self)
+
+        self.key_bindings = key_bindings
+        self.filter = to_filter(filter)
+
+    def _update_cache(self) -> None:
+        "If the original key bindings was changed. Update our copy version."
+        expected_version = self.key_bindings._version
+
+        if self._last_version != expected_version:
+            bindings2 = KeyBindings()
+
+            # Copy all bindings from `self.key_bindings`, adding our condition.
+            for b in self.key_bindings.bindings:
+                bindings2.bindings.append(
+                    Binding(
+                        keys=b.keys,
+                        handler=b.handler,
+                        filter=self.filter & b.filter,
+                        eager=b.eager,
+                        is_global=b.is_global,
+                        save_before=b.save_before,
+                        record_in_macro=b.record_in_macro,
+                    )
+                )
+
+            self._bindings2 = bindings2
+            self._last_version = expected_version
+
+
+class _MergedKeyBindings(_Proxy):
+    """
+    Merge multiple registries of key bindings into one.
+
+    This class acts as a proxy to multiple :class:`.KeyBindings` objects, but
+    behaves as if this is just one bigger :class:`.KeyBindings`.
+
+    :param registries: List of :class:`.KeyBindings` objects.
+    """
+
+    def __init__(self, registries: Sequence[KeyBindingsBase]) -> None:
+        _Proxy.__init__(self)
+        self.registries = registries
+
+    def _update_cache(self) -> None:
+        """
+        If one of the original registries was changed. Update our merged
+        version.
+        """
+        expected_version = tuple(r._version for r in self.registries)
+
+        if self._last_version != expected_version:
+            bindings2 = KeyBindings()
+
+            for reg in self.registries:
+                bindings2.bindings.extend(reg.bindings)
+
+            self._bindings2 = bindings2
+            self._last_version = expected_version
+
+
+def merge_key_bindings(bindings: Sequence[KeyBindingsBase]) -> _MergedKeyBindings:
+    """
+    Merge multiple :class:`.Keybinding` objects together.
+
+    Usage::
+
+        bindings = merge_key_bindings([bindings1, bindings2, ...])
+    """
+    return _MergedKeyBindings(bindings)
+
+
+class DynamicKeyBindings(_Proxy):
+    """
+    KeyBindings class that can dynamically returns any KeyBindings.
+
+    :param get_key_bindings: Callable that returns a :class:`.KeyBindings` instance.
+    """
+
+    def __init__(
+        self, get_key_bindings: Callable[[], Optional[KeyBindingsBase]]
+    ) -> None:
+        self.get_key_bindings = get_key_bindings
+        self.__version = 0
+        self._last_child_version = None
+        self._dummy = KeyBindings()  # Empty key bindings.
+
+    def _update_cache(self) -> None:
+        key_bindings = self.get_key_bindings() or self._dummy
+        assert isinstance(key_bindings, KeyBindingsBase)
+        version = id(key_bindings), key_bindings._version
+
+        self._bindings2 = key_bindings
+        self._last_version = version
+
+
+class GlobalOnlyKeyBindings(_Proxy):
+    """
+    Wrapper around a :class:`.KeyBindings` object that only exposes the global
+    key bindings.
+    """
+
+    def __init__(self, key_bindings: KeyBindingsBase) -> None:
+        _Proxy.__init__(self)
+        self.key_bindings = key_bindings
+
+    def _update_cache(self) -> None:
+        """
+        If one of the original registries was changed. Update our merged
+        version.
+        """
+        expected_version = self.key_bindings._version
+
+        if self._last_version != expected_version:
+            bindings2 = KeyBindings()
+
+            for b in self.key_bindings.bindings:
+                if b.is_global():
+                    bindings2.bindings.append(b)
+
+            self._bindings2 = bindings2
+            self._last_version = expected_version
diff --git a/src/prompt_toolkit/key_binding/key_processor.py b/src/prompt_toolkit/key_binding/key_processor.py
new file mode 100644
index 0000000..6fdd519
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/key_processor.py
@@ -0,0 +1,528 @@
+"""
+An :class:`~.KeyProcessor` receives callbacks for the keystrokes parsed from
+the input in the :class:`~prompt_toolkit.inputstream.InputStream` instance.
+
+The `KeyProcessor` will according to the implemented keybindings call the
+correct callbacks when new key presses are feed through `feed`.
+"""
+import weakref
+from asyncio import Task, sleep
+from collections import deque
+from typing import TYPE_CHECKING, Any, Deque, Generator, List, Optional, Union
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.enums import EditingMode
+from prompt_toolkit.filters.app import vi_navigation_mode
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.utils import Event
+
+from .key_bindings import Binding, KeyBindingsBase
+
+if TYPE_CHECKING:
+    from prompt_toolkit.application import Application
+    from prompt_toolkit.buffer import Buffer
+
+
+__all__ = [
+    "KeyProcessor",
+    "KeyPress",
+    "KeyPressEvent",
+]
+
+
+class KeyPress:
+    """
+    :param key: A `Keys` instance or text (one character).
+    :param data: The received string on stdin. (Often vt100 escape codes.)
+    """
+
+    def __init__(self, key: Union[Keys, str], data: Optional[str] = None) -> None:
+        assert isinstance(key, Keys) or len(key) == 1
+
+        if data is None:
+            if isinstance(key, Keys):
+                data = key.value
+            else:
+                data = key  # 'key' is a one character string.
+
+        self.key = key
+        self.data = data
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}(key={self.key!r}, data={self.data!r})"
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, KeyPress):
+            return False
+        return self.key == other.key and self.data == other.data
+
+
+"""
+Helper object to indicate flush operation in the KeyProcessor.
+NOTE: the implementation is very similar to the VT100 parser.
+"""
+_Flush = KeyPress("?", data="_Flush")
+
+
+class KeyProcessor:
+    """
+    Statemachine that receives :class:`KeyPress` instances and according to the
+    key bindings in the given :class:`KeyBindings`, calls the matching handlers.
+
+    ::
+
+        p = KeyProcessor(key_bindings)
+
+        # Send keys into the processor.
+        p.feed(KeyPress(Keys.ControlX, '\x18'))
+        p.feed(KeyPress(Keys.ControlC, '\x03')
+
+        # Process all the keys in the queue.
+        p.process_keys()
+
+        # Now the ControlX-ControlC callback will be called if this sequence is
+        # registered in the key bindings.
+
+    :param key_bindings: `KeyBindingsBase` instance.
+    """
+
+    def __init__(self, key_bindings: KeyBindingsBase) -> None:
+        self._bindings = key_bindings
+
+        self.before_key_press = Event(self)
+        self.after_key_press = Event(self)
+
+        self._flush_wait_task: Optional[Task[None]] = None
+
+        self.reset()
+
+    def reset(self) -> None:
+        self._previous_key_sequence: List[KeyPress] = []
+        self._previous_handler: Optional[Binding] = None
+
+        # The queue of keys not yet send to our _process generator/state machine.
+        self.input_queue: Deque[KeyPress] = deque()
+
+        # The key buffer that is matched in the generator state machine.
+        # (This is at at most the amount of keys that make up for one key binding.)
+        self.key_buffer: List[KeyPress] = []
+
+        #: Readline argument (for repetition of commands.)
+        #: https://www.gnu.org/software/bash/manual/html_node/Readline-Arguments.html
+        self.arg: Optional[str] = None
+
+        # Start the processor coroutine.
+        self._process_coroutine = self._process()
+        self._process_coroutine.send(None)  # type: ignore
+
+    def _get_matches(self, key_presses: List[KeyPress]) -> List[Binding]:
+        """
+        For a list of :class:`KeyPress` instances. Give the matching handlers
+        that would handle this.
+        """
+        keys = tuple(k.key for k in key_presses)
+
+        # Try match, with mode flag
+        return [b for b in self._bindings.get_bindings_for_keys(keys) if b.filter()]
+
+    def _is_prefix_of_longer_match(self, key_presses: List[KeyPress]) -> bool:
+        """
+        For a list of :class:`KeyPress` instances. Return True if there is any
+        handler that is bound to a suffix of this keys.
+        """
+        keys = tuple(k.key for k in key_presses)
+
+        # Get the filters for all the key bindings that have a longer match.
+        # Note that we transform it into a `set`, because we don't care about
+        # the actual bindings and executing it more than once doesn't make
+        # sense. (Many key bindings share the same filter.)
+        filters = {
+            b.filter for b in self._bindings.get_bindings_starting_with_keys(keys)
+        }
+
+        # When any key binding is active, return True.
+        return any(f() for f in filters)
+
+    def _process(self) -> Generator[None, KeyPress, None]:
+        """
+        Coroutine implementing the key match algorithm. Key strokes are sent
+        into this generator, and it calls the appropriate handlers.
+        """
+        buffer = self.key_buffer
+        retry = False
+
+        while True:
+            flush = False
+
+            if retry:
+                retry = False
+            else:
+                key = yield
+                if key is _Flush:
+                    flush = True
+                else:
+                    buffer.append(key)
+
+            # If we have some key presses, check for matches.
+            if buffer:
+                matches = self._get_matches(buffer)
+
+                if flush:
+                    is_prefix_of_longer_match = False
+                else:
+                    is_prefix_of_longer_match = self._is_prefix_of_longer_match(buffer)
+
+                # When eager matches were found, give priority to them and also
+                # ignore all the longer matches.
+                eager_matches = [m for m in matches if m.eager()]
+
+                if eager_matches:
+                    matches = eager_matches
+                    is_prefix_of_longer_match = False
+
+                # Exact matches found, call handler.
+                if not is_prefix_of_longer_match and matches:
+                    self._call_handler(matches[-1], key_sequence=buffer[:])
+                    del buffer[:]  # Keep reference.
+
+                # No match found.
+                elif not is_prefix_of_longer_match and not matches:
+                    retry = True
+                    found = False
+
+                    # Loop over the input, try longest match first and shift.
+                    for i in range(len(buffer), 0, -1):
+                        matches = self._get_matches(buffer[:i])
+                        if matches:
+                            self._call_handler(matches[-1], key_sequence=buffer[:i])
+                            del buffer[:i]
+                            found = True
+                            break
+
+                    if not found:
+                        del buffer[:1]
+
+    def feed(self, key_press: KeyPress, first: bool = False) -> None:
+        """
+        Add a new :class:`KeyPress` to the input queue.
+        (Don't forget to call `process_keys` in order to process the queue.)
+
+        :param first: If true, insert before everything else.
+        """
+        if first:
+            self.input_queue.appendleft(key_press)
+        else:
+            self.input_queue.append(key_press)
+
+    def feed_multiple(self, key_presses: List[KeyPress], first: bool = False) -> None:
+        """
+        :param first: If true, insert before everything else.
+        """
+        if first:
+            self.input_queue.extendleft(reversed(key_presses))
+        else:
+            self.input_queue.extend(key_presses)
+
+    def process_keys(self) -> None:
+        """
+        Process all the keys in the `input_queue`.
+        (To be called after `feed`.)
+
+        Note: because of the `feed`/`process_keys` separation, it is
+              possible to call `feed` from inside a key binding.
+              This function keeps looping until the queue is empty.
+        """
+        app = get_app()
+
+        def not_empty() -> bool:
+            # When the application result is set, stop processing keys.  (E.g.
+            # if ENTER was received, followed by a few additional key strokes,
+            # leave the other keys in the queue.)
+            if app.is_done:
+                # But if there are still CPRResponse keys in the queue, these
+                # need to be processed.
+                return any(k for k in self.input_queue if k.key == Keys.CPRResponse)
+            else:
+                return bool(self.input_queue)
+
+        def get_next() -> KeyPress:
+            if app.is_done:
+                # Only process CPR responses. Everything else is typeahead.
+                cpr = [k for k in self.input_queue if k.key == Keys.CPRResponse][0]
+                self.input_queue.remove(cpr)
+                return cpr
+            else:
+                return self.input_queue.popleft()
+
+        is_flush = False
+
+        while not_empty():
+            # Process next key.
+            key_press = get_next()
+
+            is_flush = key_press is _Flush
+            is_cpr = key_press.key == Keys.CPRResponse
+
+            if not is_flush and not is_cpr:
+                self.before_key_press.fire()
+
+            try:
+                self._process_coroutine.send(key_press)
+            except Exception:
+                # If for some reason something goes wrong in the parser, (maybe
+                # an exception was raised) restart the processor for next time.
+                self.reset()
+                self.empty_queue()
+                raise
+
+            if not is_flush and not is_cpr:
+                self.after_key_press.fire()
+
+        # Skip timeout if the last key was flush.
+        if not is_flush:
+            self._start_timeout()
+
+    def empty_queue(self) -> List[KeyPress]:
+        """
+        Empty the input queue. Return the unprocessed input.
+        """
+        key_presses = list(self.input_queue)
+        self.input_queue.clear()
+
+        # Filter out CPRs. We don't want to return these.
+        key_presses = [k for k in key_presses if k.key != Keys.CPRResponse]
+        return key_presses
+
+    def _call_handler(self, handler: Binding, key_sequence: List[KeyPress]) -> None:
+        app = get_app()
+        was_recording_emacs = app.emacs_state.is_recording
+        was_recording_vi = bool(app.vi_state.recording_register)
+        was_temporary_navigation_mode = app.vi_state.temporary_navigation_mode
+        arg = self.arg
+        self.arg = None
+
+        event = KeyPressEvent(
+            weakref.ref(self),
+            arg=arg,
+            key_sequence=key_sequence,
+            previous_key_sequence=self._previous_key_sequence,
+            is_repeat=(handler == self._previous_handler),
+        )
+
+        # Save the state of the current buffer.
+        if handler.save_before(event):
+            event.app.current_buffer.save_to_undo_stack()
+
+        # Call handler.
+        from prompt_toolkit.buffer import EditReadOnlyBuffer
+
+        try:
+            handler.call(event)
+            self._fix_vi_cursor_position(event)
+
+        except EditReadOnlyBuffer:
+            # When a key binding does an attempt to change a buffer which is
+            # read-only, we can ignore that. We sound a bell and go on.
+            app.output.bell()
+
+        if was_temporary_navigation_mode:
+            self._leave_vi_temp_navigation_mode(event)
+
+        self._previous_key_sequence = key_sequence
+        self._previous_handler = handler
+
+        # Record the key sequence in our macro. (Only if we're in macro mode
+        # before and after executing the key.)
+        if handler.record_in_macro():
+            if app.emacs_state.is_recording and was_recording_emacs:
+                recording = app.emacs_state.current_recording
+                if recording is not None:  # Should always be true, given that
+                    # `was_recording_emacs` is set.
+                    recording.extend(key_sequence)
+
+            if app.vi_state.recording_register and was_recording_vi:
+                for k in key_sequence:
+                    app.vi_state.current_recording += k.data
+
+    def _fix_vi_cursor_position(self, event: "KeyPressEvent") -> None:
+        """
+        After every command, make sure that if we are in Vi navigation mode, we
+        never put the cursor after the last character of a line. (Unless it's
+        an empty line.)
+        """
+        app = event.app
+        buff = app.current_buffer
+        preferred_column = buff.preferred_column
+
+        if (
+            vi_navigation_mode()
+            and buff.document.is_cursor_at_the_end_of_line
+            and len(buff.document.current_line) > 0
+        ):
+            buff.cursor_position -= 1
+
+            # Set the preferred_column for arrow up/down again.
+            # (This was cleared after changing the cursor position.)
+            buff.preferred_column = preferred_column
+
+    def _leave_vi_temp_navigation_mode(self, event: "KeyPressEvent") -> None:
+        """
+        If we're in Vi temporary navigation (normal) mode, return to
+        insert/replace mode after executing one action.
+        """
+        app = event.app
+
+        if app.editing_mode == EditingMode.VI:
+            # Not waiting for a text object and no argument has been given.
+            if app.vi_state.operator_func is None and self.arg is None:
+                app.vi_state.temporary_navigation_mode = False
+
+    def _start_timeout(self) -> None:
+        """
+        Start auto flush timeout. Similar to Vim's `timeoutlen` option.
+
+        Start a background coroutine with a timer. When this timeout expires
+        and no key was pressed in the meantime, we flush all data in the queue
+        and call the appropriate key binding handlers.
+        """
+        app = get_app()
+        timeout = app.timeoutlen
+
+        if timeout is None:
+            return
+
+        async def wait() -> None:
+            "Wait for timeout."
+            # This sleep can be cancelled. In that case we don't flush.
+            await sleep(timeout)
+
+            if len(self.key_buffer) > 0:
+                # (No keys pressed in the meantime.)
+                flush_keys()
+
+        def flush_keys() -> None:
+            "Flush keys."
+            self.feed(_Flush)
+            self.process_keys()
+
+        # Automatically flush keys.
+        if self._flush_wait_task:
+            self._flush_wait_task.cancel()
+        self._flush_wait_task = app.create_background_task(wait())
+
+    def send_sigint(self) -> None:
+        """
+        Send SIGINT. Immediately call the SIGINT key handler.
+        """
+        self.feed(KeyPress(key=Keys.SIGINT), first=True)
+        self.process_keys()
+
+
+class KeyPressEvent:
+    """
+    Key press event, delivered to key bindings.
+
+    :param key_processor_ref: Weak reference to the `KeyProcessor`.
+    :param arg: Repetition argument.
+    :param key_sequence: List of `KeyPress` instances.
+    :param previouskey_sequence: Previous list of `KeyPress` instances.
+    :param is_repeat: True when the previous event was delivered to the same handler.
+    """
+
+    def __init__(
+        self,
+        key_processor_ref: "weakref.ReferenceType[KeyProcessor]",
+        arg: Optional[str],
+        key_sequence: List[KeyPress],
+        previous_key_sequence: List[KeyPress],
+        is_repeat: bool,
+    ) -> None:
+
+        self._key_processor_ref = key_processor_ref
+        self.key_sequence = key_sequence
+        self.previous_key_sequence = previous_key_sequence
+
+        #: True when the previous key sequence was handled by the same handler.
+        self.is_repeat = is_repeat
+
+        self._arg = arg
+        self._app = get_app()
+
+    def __repr__(self) -> str:
+        return "KeyPressEvent(arg={!r}, key_sequence={!r}, is_repeat={!r})".format(
+            self.arg,
+            self.key_sequence,
+            self.is_repeat,
+        )
+
+    @property
+    def data(self) -> str:
+        return self.key_sequence[-1].data
+
+    @property
+    def key_processor(self) -> KeyProcessor:
+        processor = self._key_processor_ref()
+        if processor is None:
+            raise Exception("KeyProcessor was lost. This should not happen.")
+        return processor
+
+    @property
+    def app(self) -> "Application[Any]":
+        """
+        The current `Application` object.
+        """
+        return self._app
+
+    @property
+    def current_buffer(self) -> "Buffer":
+        """
+        The current buffer.
+        """
+        return self.app.current_buffer
+
+    @property
+    def arg(self) -> int:
+        """
+        Repetition argument.
+        """
+        if self._arg == "-":
+            return -1
+
+        result = int(self._arg or 1)
+
+        # Don't exceed a million.
+        if int(result) >= 1000000:
+            result = 1
+
+        return result
+
+    @property
+    def arg_present(self) -> bool:
+        """
+        True if repetition argument was explicitly provided.
+        """
+        return self._arg is not None
+
+    def append_to_arg_count(self, data: str) -> None:
+        """
+        Add digit to the input argument.
+
+        :param data: the typed digit as string
+        """
+        assert data in "-0123456789"
+        current = self._arg
+
+        if data == "-":
+            assert current is None or current == "-"
+            result = data
+        elif current is None:
+            result = data
+        else:
+            result = f"{current}{data}"
+
+        self.key_processor.arg = result
+
+    @property
+    def cli(self) -> "Application[Any]":
+        "For backward-compatibility."
+        return self.app
diff --git a/src/prompt_toolkit/key_binding/vi_state.py b/src/prompt_toolkit/key_binding/vi_state.py
new file mode 100644
index 0000000..10593a8
--- /dev/null
+++ b/src/prompt_toolkit/key_binding/vi_state.py
@@ -0,0 +1,107 @@
+from enum import Enum
+from typing import TYPE_CHECKING, Callable, Dict, Optional
+
+from prompt_toolkit.clipboard import ClipboardData
+
+if TYPE_CHECKING:
+    from .key_bindings.vi import TextObject
+    from .key_processor import KeyPressEvent
+
+__all__ = [
+    "InputMode",
+    "CharacterFind",
+    "ViState",
+]
+
+
+class InputMode(str, Enum):
+    value: str
+
+    INSERT = "vi-insert"
+    INSERT_MULTIPLE = "vi-insert-multiple"
+    NAVIGATION = "vi-navigation"  # Normal mode.
+    REPLACE = "vi-replace"
+    REPLACE_SINGLE = "vi-replace-single"
+
+
+class CharacterFind:
+    def __init__(self, character: str, backwards: bool = False) -> None:
+        self.character = character
+        self.backwards = backwards
+
+
+class ViState:
+    """
+    Mutable class to hold the state of the Vi navigation.
+    """
+
+    def __init__(self) -> None:
+        #: None or CharacterFind instance. (This is used to repeat the last
+        #: search in Vi mode, by pressing the 'n' or 'N' in navigation mode.)
+        self.last_character_find: Optional[CharacterFind] = None
+
+        # When an operator is given and we are waiting for text object,
+        # -- e.g. in the case of 'dw', after the 'd' --, an operator callback
+        # is set here.
+        self.operator_func: Optional[
+            Callable[["KeyPressEvent", "TextObject"], None]
+        ] = None
+        self.operator_arg: Optional[int] = None
+
+        #: Named registers. Maps register name (e.g. 'a') to
+        #: :class:`ClipboardData` instances.
+        self.named_registers: Dict[str, ClipboardData] = {}
+
+        #: The Vi mode we're currently in to.
+        self.__input_mode = InputMode.INSERT
+
+        #: Waiting for digraph.
+        self.waiting_for_digraph = False
+        self.digraph_symbol1: Optional[str] = None  # (None or a symbol.)
+
+        #: When true, make ~ act as an operator.
+        self.tilde_operator = False
+
+        #: Register in which we are recording a macro.
+        #: `None` when not recording anything.
+        # Note that the recording is only stored in the register after the
+        # recording is stopped. So we record in a separate `current_recording`
+        # variable.
+        self.recording_register: Optional[str] = None
+        self.current_recording: str = ""
+
+        # Temporary navigation (normal) mode.
+        # This happens when control-o has been pressed in insert or replace
+        # mode. The user can now do one navigation action and we'll return back
+        # to insert/replace.
+        self.temporary_navigation_mode = False
+
+    @property
+    def input_mode(self) -> InputMode:
+        "Get `InputMode`."
+        return self.__input_mode
+
+    @input_mode.setter
+    def input_mode(self, value: InputMode) -> None:
+        "Set `InputMode`."
+        if value == InputMode.NAVIGATION:
+            self.waiting_for_digraph = False
+            self.operator_func = None
+            self.operator_arg = None
+
+        self.__input_mode = value
+
+    def reset(self) -> None:
+        """
+        Reset state, go back to the given mode. INSERT by default.
+        """
+        # Go back to insert mode.
+        self.input_mode = InputMode.INSERT
+
+        self.waiting_for_digraph = False
+        self.operator_func = None
+        self.operator_arg = None
+
+        # Reset recording state.
+        self.recording_register = None
+        self.current_recording = ""
diff --git a/src/prompt_toolkit/keys.py b/src/prompt_toolkit/keys.py
new file mode 100644
index 0000000..e10ba9d
--- /dev/null
+++ b/src/prompt_toolkit/keys.py
@@ -0,0 +1,221 @@
+from enum import Enum
+from typing import Dict, List
+
+__all__ = [
+    "Keys",
+    "ALL_KEYS",
+]
+
+
+class Keys(str, Enum):
+    """
+    List of keys for use in key bindings.
+
+    Note that this is an "StrEnum", all values can be compared against
+    strings.
+    """
+
+    value: str
+
+    Escape = "escape"  # Also Control-[
+    ShiftEscape = "s-escape"
+
+    ControlAt = "c-@"  # Also Control-Space.
+
+    ControlA = "c-a"
+    ControlB = "c-b"
+    ControlC = "c-c"
+    ControlD = "c-d"
+    ControlE = "c-e"
+    ControlF = "c-f"
+    ControlG = "c-g"
+    ControlH = "c-h"
+    ControlI = "c-i"  # Tab
+    ControlJ = "c-j"  # Newline
+    ControlK = "c-k"
+    ControlL = "c-l"
+    ControlM = "c-m"  # Carriage return
+    ControlN = "c-n"
+    ControlO = "c-o"
+    ControlP = "c-p"
+    ControlQ = "c-q"
+    ControlR = "c-r"
+    ControlS = "c-s"
+    ControlT = "c-t"
+    ControlU = "c-u"
+    ControlV = "c-v"
+    ControlW = "c-w"
+    ControlX = "c-x"
+    ControlY = "c-y"
+    ControlZ = "c-z"
+
+    Control1 = "c-1"
+    Control2 = "c-2"
+    Control3 = "c-3"
+    Control4 = "c-4"
+    Control5 = "c-5"
+    Control6 = "c-6"
+    Control7 = "c-7"
+    Control8 = "c-8"
+    Control9 = "c-9"
+    Control0 = "c-0"
+
+    ControlShift1 = "c-s-1"
+    ControlShift2 = "c-s-2"
+    ControlShift3 = "c-s-3"
+    ControlShift4 = "c-s-4"
+    ControlShift5 = "c-s-5"
+    ControlShift6 = "c-s-6"
+    ControlShift7 = "c-s-7"
+    ControlShift8 = "c-s-8"
+    ControlShift9 = "c-s-9"
+    ControlShift0 = "c-s-0"
+
+    ControlBackslash = "c-\\"
+    ControlSquareClose = "c-]"
+    ControlCircumflex = "c-^"
+    ControlUnderscore = "c-_"
+
+    Left = "left"
+    Right = "right"
+    Up = "up"
+    Down = "down"
+    Home = "home"
+    End = "end"
+    Insert = "insert"
+    Delete = "delete"
+    PageUp = "pageup"
+    PageDown = "pagedown"
+
+    ControlLeft = "c-left"
+    ControlRight = "c-right"
+    ControlUp = "c-up"
+    ControlDown = "c-down"
+    ControlHome = "c-home"
+    ControlEnd = "c-end"
+    ControlInsert = "c-insert"
+    ControlDelete = "c-delete"
+    ControlPageUp = "c-pageup"
+    ControlPageDown = "c-pagedown"
+
+    ShiftLeft = "s-left"
+    ShiftRight = "s-right"
+    ShiftUp = "s-up"
+    ShiftDown = "s-down"
+    ShiftHome = "s-home"
+    ShiftEnd = "s-end"
+    ShiftInsert = "s-insert"
+    ShiftDelete = "s-delete"
+    ShiftPageUp = "s-pageup"
+    ShiftPageDown = "s-pagedown"
+
+    ControlShiftLeft = "c-s-left"
+    ControlShiftRight = "c-s-right"
+    ControlShiftUp = "c-s-up"
+    ControlShiftDown = "c-s-down"
+    ControlShiftHome = "c-s-home"
+    ControlShiftEnd = "c-s-end"
+    ControlShiftInsert = "c-s-insert"
+    ControlShiftDelete = "c-s-delete"
+    ControlShiftPageUp = "c-s-pageup"
+    ControlShiftPageDown = "c-s-pagedown"
+
+    BackTab = "s-tab"  # shift + tab
+
+    F1 = "f1"
+    F2 = "f2"
+    F3 = "f3"
+    F4 = "f4"
+    F5 = "f5"
+    F6 = "f6"
+    F7 = "f7"
+    F8 = "f8"
+    F9 = "f9"
+    F10 = "f10"
+    F11 = "f11"
+    F12 = "f12"
+    F13 = "f13"
+    F14 = "f14"
+    F15 = "f15"
+    F16 = "f16"
+    F17 = "f17"
+    F18 = "f18"
+    F19 = "f19"
+    F20 = "f20"
+    F21 = "f21"
+    F22 = "f22"
+    F23 = "f23"
+    F24 = "f24"
+
+    ControlF1 = "c-f1"
+    ControlF2 = "c-f2"
+    ControlF3 = "c-f3"
+    ControlF4 = "c-f4"
+    ControlF5 = "c-f5"
+    ControlF6 = "c-f6"
+    ControlF7 = "c-f7"
+    ControlF8 = "c-f8"
+    ControlF9 = "c-f9"
+    ControlF10 = "c-f10"
+    ControlF11 = "c-f11"
+    ControlF12 = "c-f12"
+    ControlF13 = "c-f13"
+    ControlF14 = "c-f14"
+    ControlF15 = "c-f15"
+    ControlF16 = "c-f16"
+    ControlF17 = "c-f17"
+    ControlF18 = "c-f18"
+    ControlF19 = "c-f19"
+    ControlF20 = "c-f20"
+    ControlF21 = "c-f21"
+    ControlF22 = "c-f22"
+    ControlF23 = "c-f23"
+    ControlF24 = "c-f24"
+
+    # Matches any key.
+    Any = "<any>"
+
+    # Special.
+    ScrollUp = "<scroll-up>"
+    ScrollDown = "<scroll-down>"
+
+    CPRResponse = "<cursor-position-response>"
+    Vt100MouseEvent = "<vt100-mouse-event>"
+    WindowsMouseEvent = "<windows-mouse-event>"
+    BracketedPaste = "<bracketed-paste>"
+
+    SIGINT = "<sigint>"
+
+    # For internal use: key which is ignored.
+    # (The key binding for this key should not do anything.)
+    Ignore = "<ignore>"
+
+    # Some 'Key' aliases (for backwards-compatibility).
+    ControlSpace = ControlAt
+    Tab = ControlI
+    Enter = ControlM
+    Backspace = ControlH
+
+    # ShiftControl was renamed to ControlShift in
+    # 888fcb6fa4efea0de8333177e1bbc792f3ff3c24 (20 Feb 2020).
+    ShiftControlLeft = ControlShiftLeft
+    ShiftControlRight = ControlShiftRight
+    ShiftControlHome = ControlShiftHome
+    ShiftControlEnd = ControlShiftEnd
+
+
+ALL_KEYS: List[str] = [k.value for k in Keys]
+
+
+# Aliases.
+KEY_ALIASES: Dict[str, str] = {
+    "backspace": "c-h",
+    "c-space": "c-@",
+    "enter": "c-m",
+    "tab": "c-i",
+    # ShiftControl was renamed to ControlShift.
+    "s-c-left": "c-s-left",
+    "s-c-right": "c-s-right",
+    "s-c-home": "c-s-home",
+    "s-c-end": "c-s-end",
+}
diff --git a/src/prompt_toolkit/layout/__init__.py b/src/prompt_toolkit/layout/__init__.py
new file mode 100644
index 0000000..6669da5
--- /dev/null
+++ b/src/prompt_toolkit/layout/__init__.py
@@ -0,0 +1,144 @@
+"""
+Command line layout definitions
+-------------------------------
+
+The layout of a command line interface is defined by a Container instance.
+There are two main groups of classes here. Containers and controls:
+
+- A container can contain other containers or controls, it can have multiple
+  children and it decides about the dimensions.
+- A control is responsible for rendering the actual content to a screen.
+  A control can propose some dimensions, but it's the container who decides
+  about the dimensions -- or when the control consumes more space -- which part
+  of the control will be visible.
+
+
+Container classes::
+
+    - Container (Abstract base class)
+       |- HSplit (Horizontal split)
+       |- VSplit (Vertical split)
+       |- FloatContainer (Container which can also contain menus and other floats)
+       `- Window (Container which contains one actual control
+
+Control classes::
+
+    - UIControl (Abstract base class)
+       |- FormattedTextControl (Renders formatted text, or a simple list of text fragments)
+       `- BufferControl (Renders an input buffer.)
+
+
+Usually, you end up wrapping every control inside a `Window` object, because
+that's the only way to render it in a layout.
+
+There are some prepared toolbars which are ready to use::
+
+- SystemToolbar (Shows the 'system' input buffer, for entering system commands.)
+- ArgToolbar (Shows the input 'arg', for repetition of input commands.)
+- SearchToolbar (Shows the 'search' input buffer, for incremental search.)
+- CompletionsToolbar (Shows the completions of the current buffer.)
+- ValidationToolbar (Shows validation errors of the current buffer.)
+
+And one prepared menu:
+
+- CompletionsMenu
+
+"""
+from .containers import (
+    AnyContainer,
+    ColorColumn,
+    ConditionalContainer,
+    Container,
+    DynamicContainer,
+    Float,
+    FloatContainer,
+    HorizontalAlign,
+    HSplit,
+    ScrollOffsets,
+    VerticalAlign,
+    VSplit,
+    Window,
+    WindowAlign,
+    WindowRenderInfo,
+    is_container,
+    to_container,
+    to_window,
+)
+from .controls import (
+    BufferControl,
+    DummyControl,
+    FormattedTextControl,
+    SearchBufferControl,
+    UIContent,
+    UIControl,
+)
+from .dimension import (
+    AnyDimension,
+    D,
+    Dimension,
+    is_dimension,
+    max_layout_dimensions,
+    sum_layout_dimensions,
+    to_dimension,
+)
+from .layout import InvalidLayoutError, Layout, walk
+from .margins import (
+    ConditionalMargin,
+    Margin,
+    NumberedMargin,
+    PromptMargin,
+    ScrollbarMargin,
+)
+from .menus import CompletionsMenu, MultiColumnCompletionsMenu
+from .scrollable_pane import ScrollablePane
+
+__all__ = [
+    # Layout.
+    "Layout",
+    "InvalidLayoutError",
+    "walk",
+    # Dimensions.
+    "AnyDimension",
+    "Dimension",
+    "D",
+    "sum_layout_dimensions",
+    "max_layout_dimensions",
+    "to_dimension",
+    "is_dimension",
+    # Containers.
+    "AnyContainer",
+    "Container",
+    "HorizontalAlign",
+    "VerticalAlign",
+    "HSplit",
+    "VSplit",
+    "FloatContainer",
+    "Float",
+    "WindowAlign",
+    "Window",
+    "WindowRenderInfo",
+    "ConditionalContainer",
+    "ScrollOffsets",
+    "ColorColumn",
+    "to_container",
+    "to_window",
+    "is_container",
+    "DynamicContainer",
+    "ScrollablePane",
+    # Controls.
+    "BufferControl",
+    "SearchBufferControl",
+    "DummyControl",
+    "FormattedTextControl",
+    "UIControl",
+    "UIContent",
+    # Margins.
+    "Margin",
+    "NumberedMargin",
+    "ScrollbarMargin",
+    "ConditionalMargin",
+    "PromptMargin",
+    # Menus.
+    "CompletionsMenu",
+    "MultiColumnCompletionsMenu",
+]
diff --git a/src/prompt_toolkit/layout/containers.py b/src/prompt_toolkit/layout/containers.py
new file mode 100644
index 0000000..03f9e7d
--- /dev/null
+++ b/src/prompt_toolkit/layout/containers.py
@@ -0,0 +1,2757 @@
+"""
+Container for the layout.
+(Containers can contain other containers or user interface controls.)
+"""
+from abc import ABCMeta, abstractmethod
+from enum import Enum
+from functools import partial
+from typing import (
+    TYPE_CHECKING,
+    Callable,
+    Dict,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    Union,
+    cast,
+)
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.cache import SimpleCache
+from prompt_toolkit.data_structures import Point
+from prompt_toolkit.filters import (
+    FilterOrBool,
+    emacs_insert_mode,
+    to_filter,
+    vi_insert_mode,
+)
+from prompt_toolkit.formatted_text import (
+    AnyFormattedText,
+    StyleAndTextTuples,
+    to_formatted_text,
+)
+from prompt_toolkit.formatted_text.utils import (
+    fragment_list_to_text,
+    fragment_list_width,
+)
+from prompt_toolkit.key_binding import KeyBindingsBase
+from prompt_toolkit.mouse_events import MouseEvent, MouseEventType
+from prompt_toolkit.utils import get_cwidth, take_using_weights, to_int, to_str
+
+from .controls import (
+    DummyControl,
+    FormattedTextControl,
+    GetLinePrefixCallable,
+    UIContent,
+    UIControl,
+)
+from .dimension import (
+    AnyDimension,
+    Dimension,
+    max_layout_dimensions,
+    sum_layout_dimensions,
+    to_dimension,
+)
+from .margins import Margin
+from .mouse_handlers import MouseHandlers
+from .screen import _CHAR_CACHE, Screen, WritePosition
+from .utils import explode_text_fragments
+
+if TYPE_CHECKING:
+    from typing_extensions import Protocol, TypeGuard
+
+    from prompt_toolkit.key_binding.key_bindings import NotImplementedOrNone
+
+
+__all__ = [
+    "AnyContainer",
+    "Container",
+    "HorizontalAlign",
+    "VerticalAlign",
+    "HSplit",
+    "VSplit",
+    "FloatContainer",
+    "Float",
+    "WindowAlign",
+    "Window",
+    "WindowRenderInfo",
+    "ConditionalContainer",
+    "ScrollOffsets",
+    "ColorColumn",
+    "to_container",
+    "to_window",
+    "is_container",
+    "DynamicContainer",
+]
+
+
+class Container(metaclass=ABCMeta):
+    """
+    Base class for user interface layout.
+    """
+
+    @abstractmethod
+    def reset(self) -> None:
+        """
+        Reset the state of this container and all the children.
+        (E.g. reset scroll offsets, etc...)
+        """
+
+    @abstractmethod
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        """
+        Return a :class:`~prompt_toolkit.layout.Dimension` that represents the
+        desired width for this container.
+        """
+
+    @abstractmethod
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        """
+        Return a :class:`~prompt_toolkit.layout.Dimension` that represents the
+        desired height for this container.
+        """
+
+    @abstractmethod
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        """
+        Write the actual content to the screen.
+
+        :param screen: :class:`~prompt_toolkit.layout.screen.Screen`
+        :param mouse_handlers: :class:`~prompt_toolkit.layout.mouse_handlers.MouseHandlers`.
+        :param parent_style: Style string to pass to the :class:`.Window`
+            object. This will be applied to all content of the windows.
+            :class:`.VSplit` and :class:`.HSplit` can use it to pass their
+            style down to the windows that they contain.
+        :param z_index: Used for propagating z_index from parent to child.
+        """
+
+    def is_modal(self) -> bool:
+        """
+        When this container is modal, key bindings from parent containers are
+        not taken into account if a user control in this container is focused.
+        """
+        return False
+
+    def get_key_bindings(self) -> Optional[KeyBindingsBase]:
+        """
+        Returns a :class:`.KeyBindings` object. These bindings become active when any
+        user control in this container has the focus, except if any containers
+        between this container and the focused user control is modal.
+        """
+        return None
+
+    @abstractmethod
+    def get_children(self) -> List["Container"]:
+        """
+        Return the list of child :class:`.Container` objects.
+        """
+        return []
+
+
+if TYPE_CHECKING:
+
+    class MagicContainer(Protocol):
+        """
+        Any object that implements ``__pt_container__`` represents a container.
+        """
+
+        def __pt_container__(self) -> "AnyContainer":
+            ...
+
+
+AnyContainer = Union[Container, "MagicContainer"]
+
+
+def _window_too_small() -> "Window":
+    "Create a `Window` that displays the 'Window too small' text."
+    return Window(
+        FormattedTextControl(text=[("class:window-too-small", " Window too small... ")])
+    )
+
+
+class VerticalAlign(Enum):
+    "Alignment for `HSplit`."
+    TOP = "TOP"
+    CENTER = "CENTER"
+    BOTTOM = "BOTTOM"
+    JUSTIFY = "JUSTIFY"
+
+
+class HorizontalAlign(Enum):
+    "Alignment for `VSplit`."
+    LEFT = "LEFT"
+    CENTER = "CENTER"
+    RIGHT = "RIGHT"
+    JUSTIFY = "JUSTIFY"
+
+
+class _Split(Container):
+    """
+    The common parts of `VSplit` and `HSplit`.
+    """
+
+    def __init__(
+        self,
+        children: Sequence[AnyContainer],
+        window_too_small: Optional[Container] = None,
+        padding: AnyDimension = Dimension.exact(0),
+        padding_char: Optional[str] = None,
+        padding_style: str = "",
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        z_index: Optional[int] = None,
+        modal: bool = False,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        style: Union[str, Callable[[], str]] = "",
+    ) -> None:
+
+        self.children = [to_container(c) for c in children]
+        self.window_too_small = window_too_small or _window_too_small()
+        self.padding = padding
+        self.padding_char = padding_char
+        self.padding_style = padding_style
+
+        self.width = width
+        self.height = height
+        self.z_index = z_index
+
+        self.modal = modal
+        self.key_bindings = key_bindings
+        self.style = style
+
+    def is_modal(self) -> bool:
+        return self.modal
+
+    def get_key_bindings(self) -> Optional[KeyBindingsBase]:
+        return self.key_bindings
+
+    def get_children(self) -> List[Container]:
+        return self.children
+
+
+class HSplit(_Split):
+    """
+    Several layouts, one stacked above/under the other. ::
+
+        +--------------------+
+        |                    |
+        +--------------------+
+        |                    |
+        +--------------------+
+
+    By default, this doesn't display a horizontal line between the children,
+    but if this is something you need, then create a HSplit as follows::
+
+        HSplit(children=[ ... ], padding_char='-',
+               padding=1, padding_style='#ffff00')
+
+    :param children: List of child :class:`.Container` objects.
+    :param window_too_small: A :class:`.Container` object that is displayed if
+        there is not enough space for all the children. By default, this is a
+        "Window too small" message.
+    :param align: `VerticalAlign` value.
+    :param width: When given, use this width instead of looking at the children.
+    :param height: When given, use this height instead of looking at the children.
+    :param z_index: (int or None) When specified, this can be used to bring
+        element in front of floating elements.  `None` means: inherit from parent.
+    :param style: A style string.
+    :param modal: ``True`` or ``False``.
+    :param key_bindings: ``None`` or a :class:`.KeyBindings` object.
+
+    :param padding: (`Dimension` or int), size to be used for the padding.
+    :param padding_char: Character to be used for filling in the padding.
+    :param padding_style: Style to applied to the padding.
+    """
+
+    def __init__(
+        self,
+        children: Sequence[AnyContainer],
+        window_too_small: Optional[Container] = None,
+        align: VerticalAlign = VerticalAlign.JUSTIFY,
+        padding: AnyDimension = 0,
+        padding_char: Optional[str] = None,
+        padding_style: str = "",
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        z_index: Optional[int] = None,
+        modal: bool = False,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        style: Union[str, Callable[[], str]] = "",
+    ) -> None:
+
+        super().__init__(
+            children=children,
+            window_too_small=window_too_small,
+            padding=padding,
+            padding_char=padding_char,
+            padding_style=padding_style,
+            width=width,
+            height=height,
+            z_index=z_index,
+            modal=modal,
+            key_bindings=key_bindings,
+            style=style,
+        )
+
+        self.align = align
+
+        self._children_cache: SimpleCache[
+            Tuple[Container, ...], List[Container]
+        ] = SimpleCache(maxsize=1)
+        self._remaining_space_window = Window()  # Dummy window.
+
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        if self.width is not None:
+            return to_dimension(self.width)
+
+        if self.children:
+            dimensions = [c.preferred_width(max_available_width) for c in self.children]
+            return max_layout_dimensions(dimensions)
+        else:
+            return Dimension()
+
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        if self.height is not None:
+            return to_dimension(self.height)
+
+        dimensions = [
+            c.preferred_height(width, max_available_height) for c in self._all_children
+        ]
+        return sum_layout_dimensions(dimensions)
+
+    def reset(self) -> None:
+        for c in self.children:
+            c.reset()
+
+    @property
+    def _all_children(self) -> List[Container]:
+        """
+        List of child objects, including padding.
+        """
+
+        def get() -> List[Container]:
+            result: List[Container] = []
+
+            # Padding Top.
+            if self.align in (VerticalAlign.CENTER, VerticalAlign.BOTTOM):
+                result.append(Window(width=Dimension(preferred=0)))
+
+            # The children with padding.
+            for child in self.children:
+                result.append(child)
+                result.append(
+                    Window(
+                        height=self.padding,
+                        char=self.padding_char,
+                        style=self.padding_style,
+                    )
+                )
+            if result:
+                result.pop()
+
+            # Padding right.
+            if self.align in (VerticalAlign.CENTER, VerticalAlign.TOP):
+                result.append(Window(width=Dimension(preferred=0)))
+
+            return result
+
+        return self._children_cache.get(tuple(self.children), get)
+
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        """
+        Render the prompt to a `Screen` instance.
+
+        :param screen: The :class:`~prompt_toolkit.layout.screen.Screen` class
+            to which the output has to be written.
+        """
+        sizes = self._divide_heights(write_position)
+        style = parent_style + " " + to_str(self.style)
+        z_index = z_index if self.z_index is None else self.z_index
+
+        if sizes is None:
+            self.window_too_small.write_to_screen(
+                screen, mouse_handlers, write_position, style, erase_bg, z_index
+            )
+        else:
+            #
+            ypos = write_position.ypos
+            xpos = write_position.xpos
+            width = write_position.width
+
+            # Draw child panes.
+            for s, c in zip(sizes, self._all_children):
+                c.write_to_screen(
+                    screen,
+                    mouse_handlers,
+                    WritePosition(xpos, ypos, width, s),
+                    style,
+                    erase_bg,
+                    z_index,
+                )
+                ypos += s
+
+            # Fill in the remaining space. This happens when a child control
+            # refuses to take more space and we don't have any padding. Adding a
+            # dummy child control for this (in `self._all_children`) is not
+            # desired, because in some situations, it would take more space, even
+            # when it's not required. This is required to apply the styling.
+            remaining_height = write_position.ypos + write_position.height - ypos
+            if remaining_height > 0:
+                self._remaining_space_window.write_to_screen(
+                    screen,
+                    mouse_handlers,
+                    WritePosition(xpos, ypos, width, remaining_height),
+                    style,
+                    erase_bg,
+                    z_index,
+                )
+
+    def _divide_heights(self, write_position: WritePosition) -> Optional[List[int]]:
+        """
+        Return the heights for all rows.
+        Or None when there is not enough space.
+        """
+        if not self.children:
+            return []
+
+        width = write_position.width
+        height = write_position.height
+
+        # Calculate heights.
+        dimensions = [c.preferred_height(width, height) for c in self._all_children]
+
+        # Sum dimensions
+        sum_dimensions = sum_layout_dimensions(dimensions)
+
+        # If there is not enough space for both.
+        # Don't do anything.
+        if sum_dimensions.min > height:
+            return None
+
+        # Find optimal sizes. (Start with minimal size, increase until we cover
+        # the whole height.)
+        sizes = [d.min for d in dimensions]
+
+        child_generator = take_using_weights(
+            items=list(range(len(dimensions))), weights=[d.weight for d in dimensions]
+        )
+
+        i = next(child_generator)
+
+        # Increase until we meet at least the 'preferred' size.
+        preferred_stop = min(height, sum_dimensions.preferred)
+        preferred_dimensions = [d.preferred for d in dimensions]
+
+        while sum(sizes) < preferred_stop:
+            if sizes[i] < preferred_dimensions[i]:
+                sizes[i] += 1
+            i = next(child_generator)
+
+        # Increase until we use all the available space. (or until "max")
+        if not get_app().is_done:
+            max_stop = min(height, sum_dimensions.max)
+            max_dimensions = [d.max for d in dimensions]
+
+            while sum(sizes) < max_stop:
+                if sizes[i] < max_dimensions[i]:
+                    sizes[i] += 1
+                i = next(child_generator)
+
+        return sizes
+
+
+class VSplit(_Split):
+    """
+    Several layouts, one stacked left/right of the other. ::
+
+        +---------+----------+
+        |         |          |
+        |         |          |
+        +---------+----------+
+
+    By default, this doesn't display a vertical line between the children, but
+    if this is something you need, then create a HSplit as follows::
+
+        VSplit(children=[ ... ], padding_char='|',
+               padding=1, padding_style='#ffff00')
+
+    :param children: List of child :class:`.Container` objects.
+    :param window_too_small: A :class:`.Container` object that is displayed if
+        there is not enough space for all the children. By default, this is a
+        "Window too small" message.
+    :param align: `HorizontalAlign` value.
+    :param width: When given, use this width instead of looking at the children.
+    :param height: When given, use this height instead of looking at the children.
+    :param z_index: (int or None) When specified, this can be used to bring
+        element in front of floating elements.  `None` means: inherit from parent.
+    :param style: A style string.
+    :param modal: ``True`` or ``False``.
+    :param key_bindings: ``None`` or a :class:`.KeyBindings` object.
+
+    :param padding: (`Dimension` or int), size to be used for the padding.
+    :param padding_char: Character to be used for filling in the padding.
+    :param padding_style: Style to applied to the padding.
+    """
+
+    def __init__(
+        self,
+        children: Sequence[AnyContainer],
+        window_too_small: Optional[Container] = None,
+        align: HorizontalAlign = HorizontalAlign.JUSTIFY,
+        padding: AnyDimension = 0,
+        padding_char: Optional[str] = None,
+        padding_style: str = "",
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        z_index: Optional[int] = None,
+        modal: bool = False,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        style: Union[str, Callable[[], str]] = "",
+    ) -> None:
+
+        super().__init__(
+            children=children,
+            window_too_small=window_too_small,
+            padding=padding,
+            padding_char=padding_char,
+            padding_style=padding_style,
+            width=width,
+            height=height,
+            z_index=z_index,
+            modal=modal,
+            key_bindings=key_bindings,
+            style=style,
+        )
+
+        self.align = align
+
+        self._children_cache: SimpleCache[
+            Tuple[Container, ...], List[Container]
+        ] = SimpleCache(maxsize=1)
+        self._remaining_space_window = Window()  # Dummy window.
+
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        if self.width is not None:
+            return to_dimension(self.width)
+
+        dimensions = [
+            c.preferred_width(max_available_width) for c in self._all_children
+        ]
+
+        return sum_layout_dimensions(dimensions)
+
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        if self.height is not None:
+            return to_dimension(self.height)
+
+        # At the point where we want to calculate the heights, the widths have
+        # already been decided. So we can trust `width` to be the actual
+        # `width` that's going to be used for the rendering. So,
+        # `divide_widths` is supposed to use all of the available width.
+        # Using only the `preferred` width caused a bug where the reported
+        # height was more than required. (we had a `BufferControl` which did
+        # wrap lines because of the smaller width returned by `_divide_widths`.
+
+        sizes = self._divide_widths(width)
+        children = self._all_children
+
+        if sizes is None:
+            return Dimension()
+        else:
+            dimensions = [
+                c.preferred_height(s, max_available_height)
+                for s, c in zip(sizes, children)
+            ]
+            return max_layout_dimensions(dimensions)
+
+    def reset(self) -> None:
+        for c in self.children:
+            c.reset()
+
+    @property
+    def _all_children(self) -> List[Container]:
+        """
+        List of child objects, including padding.
+        """
+
+        def get() -> List[Container]:
+            result: List[Container] = []
+
+            # Padding left.
+            if self.align in (HorizontalAlign.CENTER, HorizontalAlign.RIGHT):
+                result.append(Window(width=Dimension(preferred=0)))
+
+            # The children with padding.
+            for child in self.children:
+                result.append(child)
+                result.append(
+                    Window(
+                        width=self.padding,
+                        char=self.padding_char,
+                        style=self.padding_style,
+                    )
+                )
+            if result:
+                result.pop()
+
+            # Padding right.
+            if self.align in (HorizontalAlign.CENTER, HorizontalAlign.LEFT):
+                result.append(Window(width=Dimension(preferred=0)))
+
+            return result
+
+        return self._children_cache.get(tuple(self.children), get)
+
+    def _divide_widths(self, width: int) -> Optional[List[int]]:
+        """
+        Return the widths for all columns.
+        Or None when there is not enough space.
+        """
+        children = self._all_children
+
+        if not children:
+            return []
+
+        # Calculate widths.
+        dimensions = [c.preferred_width(width) for c in children]
+        preferred_dimensions = [d.preferred for d in dimensions]
+
+        # Sum dimensions
+        sum_dimensions = sum_layout_dimensions(dimensions)
+
+        # If there is not enough space for both.
+        # Don't do anything.
+        if sum_dimensions.min > width:
+            return None
+
+        # Find optimal sizes. (Start with minimal size, increase until we cover
+        # the whole width.)
+        sizes = [d.min for d in dimensions]
+
+        child_generator = take_using_weights(
+            items=list(range(len(dimensions))), weights=[d.weight for d in dimensions]
+        )
+
+        i = next(child_generator)
+
+        # Increase until we meet at least the 'preferred' size.
+        preferred_stop = min(width, sum_dimensions.preferred)
+
+        while sum(sizes) < preferred_stop:
+            if sizes[i] < preferred_dimensions[i]:
+                sizes[i] += 1
+            i = next(child_generator)
+
+        # Increase until we use all the available space.
+        max_dimensions = [d.max for d in dimensions]
+        max_stop = min(width, sum_dimensions.max)
+
+        while sum(sizes) < max_stop:
+            if sizes[i] < max_dimensions[i]:
+                sizes[i] += 1
+            i = next(child_generator)
+
+        return sizes
+
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        """
+        Render the prompt to a `Screen` instance.
+
+        :param screen: The :class:`~prompt_toolkit.layout.screen.Screen` class
+            to which the output has to be written.
+        """
+        if not self.children:
+            return
+
+        children = self._all_children
+        sizes = self._divide_widths(write_position.width)
+        style = parent_style + " " + to_str(self.style)
+        z_index = z_index if self.z_index is None else self.z_index
+
+        # If there is not enough space.
+        if sizes is None:
+            self.window_too_small.write_to_screen(
+                screen, mouse_handlers, write_position, style, erase_bg, z_index
+            )
+            return
+
+        # Calculate heights, take the largest possible, but not larger than
+        # write_position.height.
+        heights = [
+            child.preferred_height(width, write_position.height).preferred
+            for width, child in zip(sizes, children)
+        ]
+        height = max(write_position.height, min(write_position.height, max(heights)))
+
+        #
+        ypos = write_position.ypos
+        xpos = write_position.xpos
+
+        # Draw all child panes.
+        for s, c in zip(sizes, children):
+            c.write_to_screen(
+                screen,
+                mouse_handlers,
+                WritePosition(xpos, ypos, s, height),
+                style,
+                erase_bg,
+                z_index,
+            )
+            xpos += s
+
+        # Fill in the remaining space. This happens when a child control
+        # refuses to take more space and we don't have any padding. Adding a
+        # dummy child control for this (in `self._all_children`) is not
+        # desired, because in some situations, it would take more space, even
+        # when it's not required. This is required to apply the styling.
+        remaining_width = write_position.xpos + write_position.width - xpos
+        if remaining_width > 0:
+            self._remaining_space_window.write_to_screen(
+                screen,
+                mouse_handlers,
+                WritePosition(xpos, ypos, remaining_width, height),
+                style,
+                erase_bg,
+                z_index,
+            )
+
+
+class FloatContainer(Container):
+    """
+    Container which can contain another container for the background, as well
+    as a list of floating containers on top of it.
+
+    Example Usage::
+
+        FloatContainer(content=Window(...),
+                       floats=[
+                           Float(xcursor=True,
+                                ycursor=True,
+                                content=CompletionsMenu(...))
+                       ])
+
+    :param z_index: (int or None) When specified, this can be used to bring
+        element in front of floating elements.  `None` means: inherit from parent.
+        This is the z_index for the whole `Float` container as a whole.
+    """
+
+    def __init__(
+        self,
+        content: AnyContainer,
+        floats: List["Float"],
+        modal: bool = False,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        style: Union[str, Callable[[], str]] = "",
+        z_index: Optional[int] = None,
+    ) -> None:
+
+        self.content = to_container(content)
+        self.floats = floats
+
+        self.modal = modal
+        self.key_bindings = key_bindings
+        self.style = style
+        self.z_index = z_index
+
+    def reset(self) -> None:
+        self.content.reset()
+
+        for f in self.floats:
+            f.content.reset()
+
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        return self.content.preferred_width(max_available_width)
+
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        """
+        Return the preferred height of the float container.
+        (We don't care about the height of the floats, they should always fit
+        into the dimensions provided by the container.)
+        """
+        return self.content.preferred_height(width, max_available_height)
+
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        style = parent_style + " " + to_str(self.style)
+        z_index = z_index if self.z_index is None else self.z_index
+
+        self.content.write_to_screen(
+            screen, mouse_handlers, write_position, style, erase_bg, z_index
+        )
+
+        for number, fl in enumerate(self.floats):
+            # z_index of a Float is computed by summing the z_index of the
+            # container and the `Float`.
+            new_z_index = (z_index or 0) + fl.z_index
+            style = parent_style + " " + to_str(self.style)
+
+            # If the float that we have here, is positioned relative to the
+            # cursor position, but the Window that specifies the cursor
+            # position is not drawn yet, because it's a Float itself, we have
+            # to postpone this calculation. (This is a work-around, but good
+            # enough for now.)
+            postpone = fl.xcursor is not None or fl.ycursor is not None
+
+            if postpone:
+                new_z_index = (
+                    number + 10**8
+                )  # Draw as late as possible, but keep the order.
+                screen.draw_with_z_index(
+                    z_index=new_z_index,
+                    draw_func=partial(
+                        self._draw_float,
+                        fl,
+                        screen,
+                        mouse_handlers,
+                        write_position,
+                        style,
+                        erase_bg,
+                        new_z_index,
+                    ),
+                )
+            else:
+                self._draw_float(
+                    fl,
+                    screen,
+                    mouse_handlers,
+                    write_position,
+                    style,
+                    erase_bg,
+                    new_z_index,
+                )
+
+    def _draw_float(
+        self,
+        fl: "Float",
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        "Draw a single Float."
+        # When a menu_position was given, use this instead of the cursor
+        # position. (These cursor positions are absolute, translate again
+        # relative to the write_position.)
+        # Note: This should be inside the for-loop, because one float could
+        #       set the cursor position to be used for the next one.
+        cpos = screen.get_menu_position(
+            fl.attach_to_window or get_app().layout.current_window
+        )
+        cursor_position = Point(
+            x=cpos.x - write_position.xpos, y=cpos.y - write_position.ypos
+        )
+
+        fl_width = fl.get_width()
+        fl_height = fl.get_height()
+        width: int
+        height: int
+        xpos: int
+        ypos: int
+
+        # Left & width given.
+        if fl.left is not None and fl_width is not None:
+            xpos = fl.left
+            width = fl_width
+        # Left & right given -> calculate width.
+        elif fl.left is not None and fl.right is not None:
+            xpos = fl.left
+            width = write_position.width - fl.left - fl.right
+        # Width & right given -> calculate left.
+        elif fl_width is not None and fl.right is not None:
+            xpos = write_position.width - fl.right - fl_width
+            width = fl_width
+        # Near x position of cursor.
+        elif fl.xcursor:
+            if fl_width is None:
+                width = fl.content.preferred_width(write_position.width).preferred
+                width = min(write_position.width, width)
+            else:
+                width = fl_width
+
+            xpos = cursor_position.x
+            if xpos + width > write_position.width:
+                xpos = max(0, write_position.width - width)
+        # Only width given -> center horizontally.
+        elif fl_width:
+            xpos = int((write_position.width - fl_width) / 2)
+            width = fl_width
+        # Otherwise, take preferred width from float content.
+        else:
+            width = fl.content.preferred_width(write_position.width).preferred
+
+            if fl.left is not None:
+                xpos = fl.left
+            elif fl.right is not None:
+                xpos = max(0, write_position.width - width - fl.right)
+            else:  # Center horizontally.
+                xpos = max(0, int((write_position.width - width) / 2))
+
+            # Trim.
+            width = min(width, write_position.width - xpos)
+
+        # Top & height given.
+        if fl.top is not None and fl_height is not None:
+            ypos = fl.top
+            height = fl_height
+        # Top & bottom given -> calculate height.
+        elif fl.top is not None and fl.bottom is not None:
+            ypos = fl.top
+            height = write_position.height - fl.top - fl.bottom
+        # Height & bottom given -> calculate top.
+        elif fl_height is not None and fl.bottom is not None:
+            ypos = write_position.height - fl_height - fl.bottom
+            height = fl_height
+        # Near cursor.
+        elif fl.ycursor:
+            ypos = cursor_position.y + (0 if fl.allow_cover_cursor else 1)
+
+            if fl_height is None:
+                height = fl.content.preferred_height(
+                    width, write_position.height
+                ).preferred
+            else:
+                height = fl_height
+
+            # Reduce height if not enough space. (We can use the height
+            # when the content requires it.)
+            if height > write_position.height - ypos:
+                if write_position.height - ypos + 1 >= ypos:
+                    # When the space below the cursor is more than
+                    # the space above, just reduce the height.
+                    height = write_position.height - ypos
+                else:
+                    # Otherwise, fit the float above the cursor.
+                    height = min(height, cursor_position.y)
+                    ypos = cursor_position.y - height
+
+        # Only height given -> center vertically.
+        elif fl_height:
+            ypos = int((write_position.height - fl_height) / 2)
+            height = fl_height
+        # Otherwise, take preferred height from content.
+        else:
+            height = fl.content.preferred_height(width, write_position.height).preferred
+
+            if fl.top is not None:
+                ypos = fl.top
+            elif fl.bottom is not None:
+                ypos = max(0, write_position.height - height - fl.bottom)
+            else:  # Center vertically.
+                ypos = max(0, int((write_position.height - height) / 2))
+
+            # Trim.
+            height = min(height, write_position.height - ypos)
+
+        # Write float.
+        # (xpos and ypos can be negative: a float can be partially visible.)
+        if height > 0 and width > 0:
+            wp = WritePosition(
+                xpos=xpos + write_position.xpos,
+                ypos=ypos + write_position.ypos,
+                width=width,
+                height=height,
+            )
+
+            if not fl.hide_when_covering_content or self._area_is_empty(screen, wp):
+                fl.content.write_to_screen(
+                    screen,
+                    mouse_handlers,
+                    wp,
+                    style,
+                    erase_bg=not fl.transparent(),
+                    z_index=z_index,
+                )
+
+    def _area_is_empty(self, screen: Screen, write_position: WritePosition) -> bool:
+        """
+        Return True when the area below the write position is still empty.
+        (For floats that should not hide content underneath.)
+        """
+        wp = write_position
+
+        for y in range(wp.ypos, wp.ypos + wp.height):
+            if y in screen.data_buffer:
+                row = screen.data_buffer[y]
+
+                for x in range(wp.xpos, wp.xpos + wp.width):
+                    c = row[x]
+                    if c.char != " ":
+                        return False
+
+        return True
+
+    def is_modal(self) -> bool:
+        return self.modal
+
+    def get_key_bindings(self) -> Optional[KeyBindingsBase]:
+        return self.key_bindings
+
+    def get_children(self) -> List[Container]:
+        children = [self.content]
+        children.extend(f.content for f in self.floats)
+        return children
+
+
+class Float:
+    """
+    Float for use in a :class:`.FloatContainer`.
+    Except for the `content` parameter, all other options are optional.
+
+    :param content: :class:`.Container` instance.
+
+    :param width: :class:`.Dimension` or callable which returns a :class:`.Dimension`.
+    :param height: :class:`.Dimension` or callable which returns a :class:`.Dimension`.
+
+    :param left: Distance to the left edge of the :class:`.FloatContainer`.
+    :param right: Distance to the right edge of the :class:`.FloatContainer`.
+    :param top: Distance to the top of the :class:`.FloatContainer`.
+    :param bottom: Distance to the bottom of the :class:`.FloatContainer`.
+
+    :param attach_to_window: Attach to the cursor from this window, instead of
+        the current window.
+    :param hide_when_covering_content: Hide the float when it covers content underneath.
+    :param allow_cover_cursor: When `False`, make sure to display the float
+        below the cursor. Not on top of the indicated position.
+    :param z_index: Z-index position. For a Float, this needs to be at least
+        one. It is relative to the z_index of the parent container.
+    :param transparent: :class:`.Filter` indicating whether this float needs to be
+        drawn transparently.
+    """
+
+    def __init__(
+        self,
+        content: AnyContainer,
+        top: Optional[int] = None,
+        right: Optional[int] = None,
+        bottom: Optional[int] = None,
+        left: Optional[int] = None,
+        width: Optional[Union[int, Callable[[], int]]] = None,
+        height: Optional[Union[int, Callable[[], int]]] = None,
+        xcursor: bool = False,
+        ycursor: bool = False,
+        attach_to_window: Optional[AnyContainer] = None,
+        hide_when_covering_content: bool = False,
+        allow_cover_cursor: bool = False,
+        z_index: int = 1,
+        transparent: bool = False,
+    ) -> None:
+
+        assert z_index >= 1
+
+        self.left = left
+        self.right = right
+        self.top = top
+        self.bottom = bottom
+
+        self.width = width
+        self.height = height
+
+        self.xcursor = xcursor
+        self.ycursor = ycursor
+
+        self.attach_to_window = (
+            to_window(attach_to_window) if attach_to_window else None
+        )
+
+        self.content = to_container(content)
+        self.hide_when_covering_content = hide_when_covering_content
+        self.allow_cover_cursor = allow_cover_cursor
+        self.z_index = z_index
+        self.transparent = to_filter(transparent)
+
+    def get_width(self) -> Optional[int]:
+        if callable(self.width):
+            return self.width()
+        return self.width
+
+    def get_height(self) -> Optional[int]:
+        if callable(self.height):
+            return self.height()
+        return self.height
+
+    def __repr__(self) -> str:
+        return "Float(content=%r)" % self.content
+
+
+class WindowRenderInfo:
+    """
+    Render information for the last render time of this control.
+    It stores mapping information between the input buffers (in case of a
+    :class:`~prompt_toolkit.layout.controls.BufferControl`) and the actual
+    render position on the output screen.
+
+    (Could be used for implementation of the Vi 'H' and 'L' key bindings as
+    well as implementing mouse support.)
+
+    :param ui_content: The original :class:`.UIContent` instance that contains
+        the whole input, without clipping. (ui_content)
+    :param horizontal_scroll: The horizontal scroll of the :class:`.Window` instance.
+    :param vertical_scroll: The vertical scroll of the :class:`.Window` instance.
+    :param window_width: The width of the window that displays the content,
+        without the margins.
+    :param window_height: The height of the window that displays the content.
+    :param configured_scroll_offsets: The scroll offsets as configured for the
+        :class:`Window` instance.
+    :param visible_line_to_row_col: Mapping that maps the row numbers on the
+        displayed screen (starting from zero for the first visible line) to
+        (row, col) tuples pointing to the row and column of the :class:`.UIContent`.
+    :param rowcol_to_yx: Mapping that maps (row, column) tuples representing
+        coordinates of the :class:`UIContent` to (y, x) absolute coordinates at
+        the rendered screen.
+    """
+
+    def __init__(
+        self,
+        window: "Window",
+        ui_content: UIContent,
+        horizontal_scroll: int,
+        vertical_scroll: int,
+        window_width: int,
+        window_height: int,
+        configured_scroll_offsets: "ScrollOffsets",
+        visible_line_to_row_col: Dict[int, Tuple[int, int]],
+        rowcol_to_yx: Dict[Tuple[int, int], Tuple[int, int]],
+        x_offset: int,
+        y_offset: int,
+        wrap_lines: bool,
+    ) -> None:
+
+        self.window = window
+        self.ui_content = ui_content
+        self.vertical_scroll = vertical_scroll
+        self.window_width = window_width  # Width without margins.
+        self.window_height = window_height
+
+        self.configured_scroll_offsets = configured_scroll_offsets
+        self.visible_line_to_row_col = visible_line_to_row_col
+        self.wrap_lines = wrap_lines
+
+        self._rowcol_to_yx = rowcol_to_yx  # row/col from input to absolute y/x
+        # screen coordinates.
+        self._x_offset = x_offset
+        self._y_offset = y_offset
+
+    @property
+    def visible_line_to_input_line(self) -> Dict[int, int]:
+        return {
+            visible_line: rowcol[0]
+            for visible_line, rowcol in self.visible_line_to_row_col.items()
+        }
+
+    @property
+    def cursor_position(self) -> Point:
+        """
+        Return the cursor position coordinates, relative to the left/top corner
+        of the rendered screen.
+        """
+        cpos = self.ui_content.cursor_position
+        try:
+            y, x = self._rowcol_to_yx[cpos.y, cpos.x]
+        except KeyError:
+            # For `DummyControl` for instance, the content can be empty, and so
+            # will `_rowcol_to_yx` be. Return 0/0 by default.
+            return Point(x=0, y=0)
+        else:
+            return Point(x=x - self._x_offset, y=y - self._y_offset)
+
+    @property
+    def applied_scroll_offsets(self) -> "ScrollOffsets":
+        """
+        Return a :class:`.ScrollOffsets` instance that indicates the actual
+        offset. This can be less than or equal to what's configured. E.g, when
+        the cursor is completely at the top, the top offset will be zero rather
+        than what's configured.
+        """
+        if self.displayed_lines[0] == 0:
+            top = 0
+        else:
+            # Get row where the cursor is displayed.
+            y = self.input_line_to_visible_line[self.ui_content.cursor_position.y]
+            top = min(y, self.configured_scroll_offsets.top)
+
+        return ScrollOffsets(
+            top=top,
+            bottom=min(
+                self.ui_content.line_count - self.displayed_lines[-1] - 1,
+                self.configured_scroll_offsets.bottom,
+            ),
+            # For left/right, it probably doesn't make sense to return something.
+            # (We would have to calculate the widths of all the lines and keep
+            # double width characters in mind.)
+            left=0,
+            right=0,
+        )
+
+    @property
+    def displayed_lines(self) -> List[int]:
+        """
+        List of all the visible rows. (Line numbers of the input buffer.)
+        The last line may not be entirely visible.
+        """
+        return sorted(row for row, col in self.visible_line_to_row_col.values())
+
+    @property
+    def input_line_to_visible_line(self) -> Dict[int, int]:
+        """
+        Return the dictionary mapping the line numbers of the input buffer to
+        the lines of the screen. When a line spans several rows at the screen,
+        the first row appears in the dictionary.
+        """
+        result: Dict[int, int] = {}
+        for k, v in self.visible_line_to_input_line.items():
+            if v in result:
+                result[v] = min(result[v], k)
+            else:
+                result[v] = k
+        return result
+
+    def first_visible_line(self, after_scroll_offset: bool = False) -> int:
+        """
+        Return the line number (0 based) of the input document that corresponds
+        with the first visible line.
+        """
+        if after_scroll_offset:
+            return self.displayed_lines[self.applied_scroll_offsets.top]
+        else:
+            return self.displayed_lines[0]
+
+    def last_visible_line(self, before_scroll_offset: bool = False) -> int:
+        """
+        Like `first_visible_line`, but for the last visible line.
+        """
+        if before_scroll_offset:
+            return self.displayed_lines[-1 - self.applied_scroll_offsets.bottom]
+        else:
+            return self.displayed_lines[-1]
+
+    def center_visible_line(
+        self, before_scroll_offset: bool = False, after_scroll_offset: bool = False
+    ) -> int:
+        """
+        Like `first_visible_line`, but for the center visible line.
+        """
+        return (
+            self.first_visible_line(after_scroll_offset)
+            + (
+                self.last_visible_line(before_scroll_offset)
+                - self.first_visible_line(after_scroll_offset)
+            )
+            // 2
+        )
+
+    @property
+    def content_height(self) -> int:
+        """
+        The full height of the user control.
+        """
+        return self.ui_content.line_count
+
+    @property
+    def full_height_visible(self) -> bool:
+        """
+        True when the full height is visible (There is no vertical scroll.)
+        """
+        return (
+            self.vertical_scroll == 0
+            and self.last_visible_line() == self.content_height
+        )
+
+    @property
+    def top_visible(self) -> bool:
+        """
+        True when the top of the buffer is visible.
+        """
+        return self.vertical_scroll == 0
+
+    @property
+    def bottom_visible(self) -> bool:
+        """
+        True when the bottom of the buffer is visible.
+        """
+        return self.last_visible_line() == self.content_height - 1
+
+    @property
+    def vertical_scroll_percentage(self) -> int:
+        """
+        Vertical scroll as a percentage. (0 means: the top is visible,
+        100 means: the bottom is visible.)
+        """
+        if self.bottom_visible:
+            return 100
+        else:
+            return 100 * self.vertical_scroll // self.content_height
+
+    def get_height_for_line(self, lineno: int) -> int:
+        """
+        Return the height of the given line.
+        (The height that it would take, if this line became visible.)
+        """
+        if self.wrap_lines:
+            return self.ui_content.get_height_for_line(
+                lineno, self.window_width, self.window.get_line_prefix
+            )
+        else:
+            return 1
+
+
+class ScrollOffsets:
+    """
+    Scroll offsets for the :class:`.Window` class.
+
+    Note that left/right offsets only make sense if line wrapping is disabled.
+    """
+
+    def __init__(
+        self,
+        top: Union[int, Callable[[], int]] = 0,
+        bottom: Union[int, Callable[[], int]] = 0,
+        left: Union[int, Callable[[], int]] = 0,
+        right: Union[int, Callable[[], int]] = 0,
+    ) -> None:
+
+        self._top = top
+        self._bottom = bottom
+        self._left = left
+        self._right = right
+
+    @property
+    def top(self) -> int:
+        return to_int(self._top)
+
+    @property
+    def bottom(self) -> int:
+        return to_int(self._bottom)
+
+    @property
+    def left(self) -> int:
+        return to_int(self._left)
+
+    @property
+    def right(self) -> int:
+        return to_int(self._right)
+
+    def __repr__(self) -> str:
+        return "ScrollOffsets(top={!r}, bottom={!r}, left={!r}, right={!r})".format(
+            self._top,
+            self._bottom,
+            self._left,
+            self._right,
+        )
+
+
+class ColorColumn:
+    """
+    Column for a :class:`.Window` to be colored.
+    """
+
+    def __init__(self, position: int, style: str = "class:color-column") -> None:
+        self.position = position
+        self.style = style
+
+
+_in_insert_mode = vi_insert_mode | emacs_insert_mode
+
+
+class WindowAlign(Enum):
+    """
+    Alignment of the Window content.
+
+    Note that this is different from `HorizontalAlign` and `VerticalAlign`,
+    which are used for the alignment of the child containers in respectively
+    `VSplit` and `HSplit`.
+    """
+
+    LEFT = "LEFT"
+    RIGHT = "RIGHT"
+    CENTER = "CENTER"
+
+
+class Window(Container):
+    """
+    Container that holds a control.
+
+    :param content: :class:`.UIControl` instance.
+    :param width: :class:`.Dimension` instance or callable.
+    :param height: :class:`.Dimension` instance or callable.
+    :param z_index: When specified, this can be used to bring element in front
+        of floating elements.
+    :param dont_extend_width: When `True`, don't take up more width then the
+                              preferred width reported by the control.
+    :param dont_extend_height: When `True`, don't take up more width then the
+                               preferred height reported by the control.
+    :param ignore_content_width: A `bool` or :class:`.Filter` instance. Ignore
+        the :class:`.UIContent` width when calculating the dimensions.
+    :param ignore_content_height: A `bool` or :class:`.Filter` instance. Ignore
+        the :class:`.UIContent` height when calculating the dimensions.
+    :param left_margins: A list of :class:`.Margin` instance to be displayed on
+        the left. For instance: :class:`~prompt_toolkit.layout.NumberedMargin`
+        can be one of them in order to show line numbers.
+    :param right_margins: Like `left_margins`, but on the other side.
+    :param scroll_offsets: :class:`.ScrollOffsets` instance, representing the
+        preferred amount of lines/columns to be always visible before/after the
+        cursor. When both top and bottom are a very high number, the cursor
+        will be centered vertically most of the time.
+    :param allow_scroll_beyond_bottom: A `bool` or
+        :class:`.Filter` instance. When True, allow scrolling so far, that the
+        top part of the content is not visible anymore, while there is still
+        empty space available at the bottom of the window. In the Vi editor for
+        instance, this is possible. You will see tildes while the top part of
+        the body is hidden.
+    :param wrap_lines: A `bool` or :class:`.Filter` instance. When True, don't
+        scroll horizontally, but wrap lines instead.
+    :param get_vertical_scroll: Callable that takes this window
+        instance as input and returns a preferred vertical scroll.
+        (When this is `None`, the scroll is only determined by the last and
+        current cursor position.)
+    :param get_horizontal_scroll: Callable that takes this window
+        instance as input and returns a preferred vertical scroll.
+    :param always_hide_cursor: A `bool` or
+        :class:`.Filter` instance. When True, never display the cursor, even
+        when the user control specifies a cursor position.
+    :param cursorline: A `bool` or :class:`.Filter` instance. When True,
+        display a cursorline.
+    :param cursorcolumn: A `bool` or :class:`.Filter` instance. When True,
+        display a cursorcolumn.
+    :param colorcolumns: A list of :class:`.ColorColumn` instances that
+        describe the columns to be highlighted, or a callable that returns such
+        a list.
+    :param align: :class:`.WindowAlign` value or callable that returns an
+        :class:`.WindowAlign` value. alignment of content.
+    :param style: A style string. Style to be applied to all the cells in this
+        window. (This can be a callable that returns a string.)
+    :param char: (string) Character to be used for filling the background. This
+        can also be a callable that returns a character.
+    :param get_line_prefix: None or a callable that returns formatted text to
+        be inserted before a line. It takes a line number (int) and a
+        wrap_count and returns formatted text. This can be used for
+        implementation of line continuations, things like Vim "breakindent" and
+        so on.
+    """
+
+    def __init__(
+        self,
+        content: Optional[UIControl] = None,
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        z_index: Optional[int] = None,
+        dont_extend_width: FilterOrBool = False,
+        dont_extend_height: FilterOrBool = False,
+        ignore_content_width: FilterOrBool = False,
+        ignore_content_height: FilterOrBool = False,
+        left_margins: Optional[Sequence[Margin]] = None,
+        right_margins: Optional[Sequence[Margin]] = None,
+        scroll_offsets: Optional[ScrollOffsets] = None,
+        allow_scroll_beyond_bottom: FilterOrBool = False,
+        wrap_lines: FilterOrBool = False,
+        get_vertical_scroll: Optional[Callable[["Window"], int]] = None,
+        get_horizontal_scroll: Optional[Callable[["Window"], int]] = None,
+        always_hide_cursor: FilterOrBool = False,
+        cursorline: FilterOrBool = False,
+        cursorcolumn: FilterOrBool = False,
+        colorcolumns: Union[
+            None, List[ColorColumn], Callable[[], List[ColorColumn]]
+        ] = None,
+        align: Union[WindowAlign, Callable[[], WindowAlign]] = WindowAlign.LEFT,
+        style: Union[str, Callable[[], str]] = "",
+        char: Union[None, str, Callable[[], str]] = None,
+        get_line_prefix: Optional[GetLinePrefixCallable] = None,
+    ) -> None:
+
+        self.allow_scroll_beyond_bottom = to_filter(allow_scroll_beyond_bottom)
+        self.always_hide_cursor = to_filter(always_hide_cursor)
+        self.wrap_lines = to_filter(wrap_lines)
+        self.cursorline = to_filter(cursorline)
+        self.cursorcolumn = to_filter(cursorcolumn)
+
+        self.content = content or DummyControl()
+        self.dont_extend_width = to_filter(dont_extend_width)
+        self.dont_extend_height = to_filter(dont_extend_height)
+        self.ignore_content_width = to_filter(ignore_content_width)
+        self.ignore_content_height = to_filter(ignore_content_height)
+        self.left_margins = left_margins or []
+        self.right_margins = right_margins or []
+        self.scroll_offsets = scroll_offsets or ScrollOffsets()
+        self.get_vertical_scroll = get_vertical_scroll
+        self.get_horizontal_scroll = get_horizontal_scroll
+        self.colorcolumns = colorcolumns or []
+        self.align = align
+        self.style = style
+        self.char = char
+        self.get_line_prefix = get_line_prefix
+
+        self.width = width
+        self.height = height
+        self.z_index = z_index
+
+        # Cache for the screens generated by the margin.
+        self._ui_content_cache: SimpleCache[
+            Tuple[int, int, int], UIContent
+        ] = SimpleCache(maxsize=8)
+        self._margin_width_cache: SimpleCache[Tuple[Margin, int], int] = SimpleCache(
+            maxsize=1
+        )
+
+        self.reset()
+
+    def __repr__(self) -> str:
+        return "Window(content=%r)" % self.content
+
+    def reset(self) -> None:
+        self.content.reset()
+
+        #: Scrolling position of the main content.
+        self.vertical_scroll = 0
+        self.horizontal_scroll = 0
+
+        # Vertical scroll 2: this is the vertical offset that a line is
+        # scrolled if a single line (the one that contains the cursor) consumes
+        # all of the vertical space.
+        self.vertical_scroll_2 = 0
+
+        #: Keep render information (mappings between buffer input and render
+        #: output.)
+        self.render_info: Optional[WindowRenderInfo] = None
+
+    def _get_margin_width(self, margin: Margin) -> int:
+        """
+        Return the width for this margin.
+        (Calculate only once per render time.)
+        """
+        # Margin.get_width, needs to have a UIContent instance.
+        def get_ui_content() -> UIContent:
+            return self._get_ui_content(width=0, height=0)
+
+        def get_width() -> int:
+            return margin.get_width(get_ui_content)
+
+        key = (margin, get_app().render_counter)
+        return self._margin_width_cache.get(key, get_width)
+
+    def _get_total_margin_width(self) -> int:
+        """
+        Calculate and return the width of the margin (left + right).
+        """
+        return sum(self._get_margin_width(m) for m in self.left_margins) + sum(
+            self._get_margin_width(m) for m in self.right_margins
+        )
+
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        """
+        Calculate the preferred width for this window.
+        """
+
+        def preferred_content_width() -> Optional[int]:
+            """Content width: is only calculated if no exact width for the
+            window was given."""
+            if self.ignore_content_width():
+                return None
+
+            # Calculate the width of the margin.
+            total_margin_width = self._get_total_margin_width()
+
+            # Window of the content. (Can be `None`.)
+            preferred_width = self.content.preferred_width(
+                max_available_width - total_margin_width
+            )
+
+            if preferred_width is not None:
+                # Include width of the margins.
+                preferred_width += total_margin_width
+            return preferred_width
+
+        # Merge.
+        return self._merge_dimensions(
+            dimension=to_dimension(self.width),
+            get_preferred=preferred_content_width,
+            dont_extend=self.dont_extend_width(),
+        )
+
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        """
+        Calculate the preferred height for this window.
+        """
+
+        def preferred_content_height() -> Optional[int]:
+            """Content height: is only calculated if no exact height for the
+            window was given."""
+            if self.ignore_content_height():
+                return None
+
+            total_margin_width = self._get_total_margin_width()
+            wrap_lines = self.wrap_lines()
+
+            return self.content.preferred_height(
+                width - total_margin_width,
+                max_available_height,
+                wrap_lines,
+                self.get_line_prefix,
+            )
+
+        return self._merge_dimensions(
+            dimension=to_dimension(self.height),
+            get_preferred=preferred_content_height,
+            dont_extend=self.dont_extend_height(),
+        )
+
+    @staticmethod
+    def _merge_dimensions(
+        dimension: Optional[Dimension],
+        get_preferred: Callable[[], Optional[int]],
+        dont_extend: bool = False,
+    ) -> Dimension:
+        """
+        Take the Dimension from this `Window` class and the received preferred
+        size from the `UIControl` and return a `Dimension` to report to the
+        parent container.
+        """
+        dimension = dimension or Dimension()
+
+        # When a preferred dimension was explicitly given to the Window,
+        # ignore the UIControl.
+        preferred: Optional[int]
+
+        if dimension.preferred_specified:
+            preferred = dimension.preferred
+        else:
+            # Otherwise, calculate the preferred dimension from the UI control
+            # content.
+            preferred = get_preferred()
+
+        # When a 'preferred' dimension is given by the UIControl, make sure
+        # that it stays within the bounds of the Window.
+        if preferred is not None:
+            if dimension.max_specified:
+                preferred = min(preferred, dimension.max)
+
+            if dimension.min_specified:
+                preferred = max(preferred, dimension.min)
+
+        # When a `dont_extend` flag has been given, use the preferred dimension
+        # also as the max dimension.
+        max_: Optional[int]
+        min_: Optional[int]
+
+        if dont_extend and preferred is not None:
+            max_ = min(dimension.max, preferred)
+        else:
+            max_ = dimension.max if dimension.max_specified else None
+
+        min_ = dimension.min if dimension.min_specified else None
+
+        return Dimension(
+            min=min_, max=max_, preferred=preferred, weight=dimension.weight
+        )
+
+    def _get_ui_content(self, width: int, height: int) -> UIContent:
+        """
+        Create a `UIContent` instance.
+        """
+
+        def get_content() -> UIContent:
+            return self.content.create_content(width=width, height=height)
+
+        key = (get_app().render_counter, width, height)
+        return self._ui_content_cache.get(key, get_content)
+
+    def _get_digraph_char(self) -> Optional[str]:
+        "Return `False`, or the Digraph symbol to be used."
+        app = get_app()
+        if app.quoted_insert:
+            return "^"
+        if app.vi_state.waiting_for_digraph:
+            if app.vi_state.digraph_symbol1:
+                return app.vi_state.digraph_symbol1
+            return "?"
+        return None
+
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        """
+        Write window to screen. This renders the user control, the margins and
+        copies everything over to the absolute position at the given screen.
+        """
+        # If dont_extend_width/height was given. Then reduce width/height in
+        # WritePosition if the parent wanted us to paint in a bigger area.
+        # (This happens if this window is bundled with another window in a
+        # HSplit/VSplit, but with different size requirements.)
+        write_position = WritePosition(
+            xpos=write_position.xpos,
+            ypos=write_position.ypos,
+            width=write_position.width,
+            height=write_position.height,
+        )
+
+        if self.dont_extend_width():
+            write_position.width = min(
+                write_position.width,
+                self.preferred_width(write_position.width).preferred,
+            )
+
+        if self.dont_extend_height():
+            write_position.height = min(
+                write_position.height,
+                self.preferred_height(
+                    write_position.width, write_position.height
+                ).preferred,
+            )
+
+        # Draw
+        z_index = z_index if self.z_index is None else self.z_index
+
+        draw_func = partial(
+            self._write_to_screen_at_index,
+            screen,
+            mouse_handlers,
+            write_position,
+            parent_style,
+            erase_bg,
+        )
+
+        if z_index is None or z_index <= 0:
+            # When no z_index is given, draw right away.
+            draw_func()
+        else:
+            # Otherwise, postpone.
+            screen.draw_with_z_index(z_index=z_index, draw_func=draw_func)
+
+    def _write_to_screen_at_index(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+    ) -> None:
+        # Don't bother writing invisible windows.
+        # (We save some time, but also avoid applying last-line styling.)
+        if write_position.height <= 0 or write_position.width <= 0:
+            return
+
+        # Calculate margin sizes.
+        left_margin_widths = [self._get_margin_width(m) for m in self.left_margins]
+        right_margin_widths = [self._get_margin_width(m) for m in self.right_margins]
+        total_margin_width = sum(left_margin_widths + right_margin_widths)
+
+        # Render UserControl.
+        ui_content = self.content.create_content(
+            write_position.width - total_margin_width, write_position.height
+        )
+        assert isinstance(ui_content, UIContent)
+
+        # Scroll content.
+        wrap_lines = self.wrap_lines()
+        self._scroll(
+            ui_content, write_position.width - total_margin_width, write_position.height
+        )
+
+        # Erase background and fill with `char`.
+        self._fill_bg(screen, write_position, erase_bg)
+
+        # Resolve `align` attribute.
+        align = self.align() if callable(self.align) else self.align
+
+        # Write body
+        visible_line_to_row_col, rowcol_to_yx = self._copy_body(
+            ui_content,
+            screen,
+            write_position,
+            sum(left_margin_widths),
+            write_position.width - total_margin_width,
+            self.vertical_scroll,
+            self.horizontal_scroll,
+            wrap_lines=wrap_lines,
+            highlight_lines=True,
+            vertical_scroll_2=self.vertical_scroll_2,
+            always_hide_cursor=self.always_hide_cursor(),
+            has_focus=get_app().layout.current_control == self.content,
+            align=align,
+            get_line_prefix=self.get_line_prefix,
+        )
+
+        # Remember render info. (Set before generating the margins. They need this.)
+        x_offset = write_position.xpos + sum(left_margin_widths)
+        y_offset = write_position.ypos
+
+        render_info = WindowRenderInfo(
+            window=self,
+            ui_content=ui_content,
+            horizontal_scroll=self.horizontal_scroll,
+            vertical_scroll=self.vertical_scroll,
+            window_width=write_position.width - total_margin_width,
+            window_height=write_position.height,
+            configured_scroll_offsets=self.scroll_offsets,
+            visible_line_to_row_col=visible_line_to_row_col,
+            rowcol_to_yx=rowcol_to_yx,
+            x_offset=x_offset,
+            y_offset=y_offset,
+            wrap_lines=wrap_lines,
+        )
+        self.render_info = render_info
+
+        # Set mouse handlers.
+        def mouse_handler(mouse_event: MouseEvent) -> "NotImplementedOrNone":
+            """
+            Wrapper around the mouse_handler of the `UIControl` that turns
+            screen coordinates into line coordinates.
+            Returns `NotImplemented` if no UI invalidation should be done.
+            """
+            # Don't handle mouse events outside of the current modal part of
+            # the UI.
+            if self not in get_app().layout.walk_through_modal_area():
+                return NotImplemented
+
+            # Find row/col position first.
+            yx_to_rowcol = {v: k for k, v in rowcol_to_yx.items()}
+            y = mouse_event.position.y
+            x = mouse_event.position.x
+
+            # If clicked below the content area, look for a position in the
+            # last line instead.
+            max_y = write_position.ypos + len(visible_line_to_row_col) - 1
+            y = min(max_y, y)
+            result: NotImplementedOrNone
+
+            while x >= 0:
+                try:
+                    row, col = yx_to_rowcol[y, x]
+                except KeyError:
+                    # Try again. (When clicking on the right side of double
+                    # width characters, or on the right side of the input.)
+                    x -= 1
+                else:
+                    # Found position, call handler of UIControl.
+                    result = self.content.mouse_handler(
+                        MouseEvent(
+                            position=Point(x=col, y=row),
+                            event_type=mouse_event.event_type,
+                            button=mouse_event.button,
+                            modifiers=mouse_event.modifiers,
+                        )
+                    )
+                    break
+            else:
+                # nobreak.
+                # (No x/y coordinate found for the content. This happens in
+                # case of a DummyControl, that does not have any content.
+                # Report (0,0) instead.)
+                result = self.content.mouse_handler(
+                    MouseEvent(
+                        position=Point(x=0, y=0),
+                        event_type=mouse_event.event_type,
+                        button=mouse_event.button,
+                        modifiers=mouse_event.modifiers,
+                    )
+                )
+
+            # If it returns NotImplemented, handle it here.
+            if result == NotImplemented:
+                result = self._mouse_handler(mouse_event)
+
+            return result
+
+        mouse_handlers.set_mouse_handler_for_range(
+            x_min=write_position.xpos + sum(left_margin_widths),
+            x_max=write_position.xpos + write_position.width - total_margin_width,
+            y_min=write_position.ypos,
+            y_max=write_position.ypos + write_position.height,
+            handler=mouse_handler,
+        )
+
+        # Render and copy margins.
+        move_x = 0
+
+        def render_margin(m: Margin, width: int) -> UIContent:
+            "Render margin. Return `Screen`."
+            # Retrieve margin fragments.
+            fragments = m.create_margin(render_info, width, write_position.height)
+
+            # Turn it into a UIContent object.
+            # already rendered those fragments using this size.)
+            return FormattedTextControl(fragments).create_content(
+                width + 1, write_position.height
+            )
+
+        for m, width in zip(self.left_margins, left_margin_widths):
+            if width > 0:  # (ConditionalMargin returns a zero width. -- Don't render.)
+                # Create screen for margin.
+                margin_content = render_margin(m, width)
+
+                # Copy and shift X.
+                self._copy_margin(margin_content, screen, write_position, move_x, width)
+                move_x += width
+
+        move_x = write_position.width - sum(right_margin_widths)
+
+        for m, width in zip(self.right_margins, right_margin_widths):
+            # Create screen for margin.
+            margin_content = render_margin(m, width)
+
+            # Copy and shift X.
+            self._copy_margin(margin_content, screen, write_position, move_x, width)
+            move_x += width
+
+        # Apply 'self.style'
+        self._apply_style(screen, write_position, parent_style)
+
+        # Tell the screen that this user control has been painted at this
+        # position.
+        screen.visible_windows_to_write_positions[self] = write_position
+
+    def _copy_body(
+        self,
+        ui_content: UIContent,
+        new_screen: Screen,
+        write_position: WritePosition,
+        move_x: int,
+        width: int,
+        vertical_scroll: int = 0,
+        horizontal_scroll: int = 0,
+        wrap_lines: bool = False,
+        highlight_lines: bool = False,
+        vertical_scroll_2: int = 0,
+        always_hide_cursor: bool = False,
+        has_focus: bool = False,
+        align: WindowAlign = WindowAlign.LEFT,
+        get_line_prefix: Optional[Callable[[int, int], AnyFormattedText]] = None,
+    ) -> Tuple[Dict[int, Tuple[int, int]], Dict[Tuple[int, int], Tuple[int, int]]]:
+        """
+        Copy the UIContent into the output screen.
+        Return (visible_line_to_row_col, rowcol_to_yx) tuple.
+
+        :param get_line_prefix: None or a callable that takes a line number
+            (int) and a wrap_count (int) and returns formatted text.
+        """
+        xpos = write_position.xpos + move_x
+        ypos = write_position.ypos
+        line_count = ui_content.line_count
+        new_buffer = new_screen.data_buffer
+        empty_char = _CHAR_CACHE["", ""]
+
+        # Map visible line number to (row, col) of input.
+        # 'col' will always be zero if line wrapping is off.
+        visible_line_to_row_col: Dict[int, Tuple[int, int]] = {}
+
+        # Maps (row, col) from the input to (y, x) screen coordinates.
+        rowcol_to_yx: Dict[Tuple[int, int], Tuple[int, int]] = {}
+
+        def copy_line(
+            line: StyleAndTextTuples,
+            lineno: int,
+            x: int,
+            y: int,
+            is_input: bool = False,
+        ) -> Tuple[int, int]:
+            """
+            Copy over a single line to the output screen. This can wrap over
+            multiple lines in the output. It will call the prefix (prompt)
+            function before every line.
+            """
+            if is_input:
+                current_rowcol_to_yx = rowcol_to_yx
+            else:
+                current_rowcol_to_yx = {}  # Throwaway dictionary.
+
+            # Draw line prefix.
+            if is_input and get_line_prefix:
+                prompt = to_formatted_text(get_line_prefix(lineno, 0))
+                x, y = copy_line(prompt, lineno, x, y, is_input=False)
+
+            # Scroll horizontally.
+            skipped = 0  # Characters skipped because of horizontal scrolling.
+            if horizontal_scroll and is_input:
+                h_scroll = horizontal_scroll
+                line = explode_text_fragments(line)
+                while h_scroll > 0 and line:
+                    h_scroll -= get_cwidth(line[0][1])
+                    skipped += 1
+                    del line[:1]  # Remove first character.
+
+                x -= h_scroll  # When scrolling over double width character,
+                # this can end up being negative.
+
+            # Align this line. (Note that this doesn't work well when we use
+            # get_line_prefix and that function returns variable width prefixes.)
+            if align == WindowAlign.CENTER:
+                line_width = fragment_list_width(line)
+                if line_width < width:
+                    x += (width - line_width) // 2
+            elif align == WindowAlign.RIGHT:
+                line_width = fragment_list_width(line)
+                if line_width < width:
+                    x += width - line_width
+
+            col = 0
+            wrap_count = 0
+            for style, text, *_ in line:
+                new_buffer_row = new_buffer[y + ypos]
+
+                # Remember raw VT escape sequences. (E.g. FinalTerm's
+                # escape sequences.)
+                if "[ZeroWidthEscape]" in style:
+                    new_screen.zero_width_escapes[y + ypos][x + xpos] += text
+                    continue
+
+                for c in text:
+                    char = _CHAR_CACHE[c, style]
+                    char_width = char.width
+
+                    # Wrap when the line width is exceeded.
+                    if wrap_lines and x + char_width > width:
+                        visible_line_to_row_col[y + 1] = (
+                            lineno,
+                            visible_line_to_row_col[y][1] + x,
+                        )
+                        y += 1
+                        wrap_count += 1
+                        x = 0
+
+                        # Insert line prefix (continuation prompt).
+                        if is_input and get_line_prefix:
+                            prompt = to_formatted_text(
+                                get_line_prefix(lineno, wrap_count)
+                            )
+                            x, y = copy_line(prompt, lineno, x, y, is_input=False)
+
+                        new_buffer_row = new_buffer[y + ypos]
+
+                        if y >= write_position.height:
+                            return x, y  # Break out of all for loops.
+
+                    # Set character in screen and shift 'x'.
+                    if x >= 0 and y >= 0 and x < width:
+                        new_buffer_row[x + xpos] = char
+
+                        # When we print a multi width character, make sure
+                        # to erase the neighbours positions in the screen.
+                        # (The empty string if different from everything,
+                        # so next redraw this cell will repaint anyway.)
+                        if char_width > 1:
+                            for i in range(1, char_width):
+                                new_buffer_row[x + xpos + i] = empty_char
+
+                        # If this is a zero width characters, then it's
+                        # probably part of a decomposed unicode character.
+                        # See: https://en.wikipedia.org/wiki/Unicode_equivalence
+                        # Merge it in the previous cell.
+                        elif char_width == 0:
+                            # Handle all character widths. If the previous
+                            # character is a multiwidth character, then
+                            # merge it two positions back.
+                            for pw in [2, 1]:  # Previous character width.
+                                if (
+                                    x - pw >= 0
+                                    and new_buffer_row[x + xpos - pw].width == pw
+                                ):
+                                    prev_char = new_buffer_row[x + xpos - pw]
+                                    char2 = _CHAR_CACHE[
+                                        prev_char.char + c, prev_char.style
+                                    ]
+                                    new_buffer_row[x + xpos - pw] = char2
+
+                        # Keep track of write position for each character.
+                        current_rowcol_to_yx[lineno, col + skipped] = (
+                            y + ypos,
+                            x + xpos,
+                        )
+
+                    col += 1
+                    x += char_width
+            return x, y
+
+        # Copy content.
+        def copy() -> int:
+            y = -vertical_scroll_2
+            lineno = vertical_scroll
+
+            while y < write_position.height and lineno < line_count:
+                # Take the next line and copy it in the real screen.
+                line = ui_content.get_line(lineno)
+
+                visible_line_to_row_col[y] = (lineno, horizontal_scroll)
+
+                # Copy margin and actual line.
+                x = 0
+                x, y = copy_line(line, lineno, x, y, is_input=True)
+
+                lineno += 1
+                y += 1
+            return y
+
+        copy()
+
+        def cursor_pos_to_screen_pos(row: int, col: int) -> Point:
+            "Translate row/col from UIContent to real Screen coordinates."
+            try:
+                y, x = rowcol_to_yx[row, col]
+            except KeyError:
+                # Normally this should never happen. (It is a bug, if it happens.)
+                # But to be sure, return (0, 0)
+                return Point(x=0, y=0)
+
+                # raise ValueError(
+                #     'Invalid position. row=%r col=%r, vertical_scroll=%r, '
+                #     'horizontal_scroll=%r, height=%r' %
+                #     (row, col, vertical_scroll, horizontal_scroll, write_position.height))
+            else:
+                return Point(x=x, y=y)
+
+        # Set cursor and menu positions.
+        if ui_content.cursor_position:
+            screen_cursor_position = cursor_pos_to_screen_pos(
+                ui_content.cursor_position.y, ui_content.cursor_position.x
+            )
+
+            if has_focus:
+                new_screen.set_cursor_position(self, screen_cursor_position)
+
+                if always_hide_cursor:
+                    new_screen.show_cursor = False
+                else:
+                    new_screen.show_cursor = ui_content.show_cursor
+
+                self._highlight_digraph(new_screen)
+
+            if highlight_lines:
+                self._highlight_cursorlines(
+                    new_screen,
+                    screen_cursor_position,
+                    xpos,
+                    ypos,
+                    width,
+                    write_position.height,
+                )
+
+        # Draw input characters from the input processor queue.
+        if has_focus and ui_content.cursor_position:
+            self._show_key_processor_key_buffer(new_screen)
+
+        # Set menu position.
+        if ui_content.menu_position:
+            new_screen.set_menu_position(
+                self,
+                cursor_pos_to_screen_pos(
+                    ui_content.menu_position.y, ui_content.menu_position.x
+                ),
+            )
+
+        # Update output screen height.
+        new_screen.height = max(new_screen.height, ypos + write_position.height)
+
+        return visible_line_to_row_col, rowcol_to_yx
+
+    def _fill_bg(
+        self, screen: Screen, write_position: WritePosition, erase_bg: bool
+    ) -> None:
+        """
+        Erase/fill the background.
+        (Useful for floats and when a `char` has been given.)
+        """
+        char: Optional[str]
+        if callable(self.char):
+            char = self.char()
+        else:
+            char = self.char
+
+        if erase_bg or char:
+            wp = write_position
+            char_obj = _CHAR_CACHE[char or " ", ""]
+
+            for y in range(wp.ypos, wp.ypos + wp.height):
+                row = screen.data_buffer[y]
+                for x in range(wp.xpos, wp.xpos + wp.width):
+                    row[x] = char_obj
+
+    def _apply_style(
+        self, new_screen: Screen, write_position: WritePosition, parent_style: str
+    ) -> None:
+
+        # Apply `self.style`.
+        style = parent_style + " " + to_str(self.style)
+
+        new_screen.fill_area(write_position, style=style, after=False)
+
+        # Apply the 'last-line' class to the last line of each Window. This can
+        # be used to apply an 'underline' to the user control.
+        wp = WritePosition(
+            write_position.xpos,
+            write_position.ypos + write_position.height - 1,
+            write_position.width,
+            1,
+        )
+        new_screen.fill_area(wp, "class:last-line", after=True)
+
+    def _highlight_digraph(self, new_screen: Screen) -> None:
+        """
+        When we are in Vi digraph mode, put a question mark underneath the
+        cursor.
+        """
+        digraph_char = self._get_digraph_char()
+        if digraph_char:
+            cpos = new_screen.get_cursor_position(self)
+            new_screen.data_buffer[cpos.y][cpos.x] = _CHAR_CACHE[
+                digraph_char, "class:digraph"
+            ]
+
+    def _show_key_processor_key_buffer(self, new_screen: Screen) -> None:
+        """
+        When the user is typing a key binding that consists of several keys,
+        display the last pressed key if the user is in insert mode and the key
+        is meaningful to be displayed.
+        E.g. Some people want to bind 'jj' to escape in Vi insert mode. But the
+             first 'j' needs to be displayed in order to get some feedback.
+        """
+        app = get_app()
+        key_buffer = app.key_processor.key_buffer
+
+        if key_buffer and _in_insert_mode() and not app.is_done:
+            # The textual data for the given key. (Can be a VT100 escape
+            # sequence.)
+            data = key_buffer[-1].data
+
+            # Display only if this is a 1 cell width character.
+            if get_cwidth(data) == 1:
+                cpos = new_screen.get_cursor_position(self)
+                new_screen.data_buffer[cpos.y][cpos.x] = _CHAR_CACHE[
+                    data, "class:partial-key-binding"
+                ]
+
+    def _highlight_cursorlines(
+        self, new_screen: Screen, cpos: Point, x: int, y: int, width: int, height: int
+    ) -> None:
+        """
+        Highlight cursor row/column.
+        """
+        cursor_line_style = " class:cursor-line "
+        cursor_column_style = " class:cursor-column "
+
+        data_buffer = new_screen.data_buffer
+
+        # Highlight cursor line.
+        if self.cursorline():
+            row = data_buffer[cpos.y]
+            for x in range(x, x + width):
+                original_char = row[x]
+                row[x] = _CHAR_CACHE[
+                    original_char.char, original_char.style + cursor_line_style
+                ]
+
+        # Highlight cursor column.
+        if self.cursorcolumn():
+            for y2 in range(y, y + height):
+                row = data_buffer[y2]
+                original_char = row[cpos.x]
+                row[cpos.x] = _CHAR_CACHE[
+                    original_char.char, original_char.style + cursor_column_style
+                ]
+
+        # Highlight color columns
+        colorcolumns = self.colorcolumns
+        if callable(colorcolumns):
+            colorcolumns = colorcolumns()
+
+        for cc in colorcolumns:
+            assert isinstance(cc, ColorColumn)
+            column = cc.position
+
+            if column < x + width:  # Only draw when visible.
+                color_column_style = " " + cc.style
+
+                for y2 in range(y, y + height):
+                    row = data_buffer[y2]
+                    original_char = row[column + x]
+                    row[column + x] = _CHAR_CACHE[
+                        original_char.char, original_char.style + color_column_style
+                    ]
+
+    def _copy_margin(
+        self,
+        margin_content: UIContent,
+        new_screen: Screen,
+        write_position: WritePosition,
+        move_x: int,
+        width: int,
+    ) -> None:
+        """
+        Copy characters from the margin screen to the real screen.
+        """
+        xpos = write_position.xpos + move_x
+        ypos = write_position.ypos
+
+        margin_write_position = WritePosition(xpos, ypos, width, write_position.height)
+        self._copy_body(margin_content, new_screen, margin_write_position, 0, width)
+
+    def _scroll(self, ui_content: UIContent, width: int, height: int) -> None:
+        """
+        Scroll body. Ensure that the cursor is visible.
+        """
+        if self.wrap_lines():
+            func = self._scroll_when_linewrapping
+        else:
+            func = self._scroll_without_linewrapping
+
+        func(ui_content, width, height)
+
+    def _scroll_when_linewrapping(
+        self, ui_content: UIContent, width: int, height: int
+    ) -> None:
+        """
+        Scroll to make sure the cursor position is visible and that we maintain
+        the requested scroll offset.
+
+        Set `self.horizontal_scroll/vertical_scroll`.
+        """
+        scroll_offsets_bottom = self.scroll_offsets.bottom
+        scroll_offsets_top = self.scroll_offsets.top
+
+        # We don't have horizontal scrolling.
+        self.horizontal_scroll = 0
+
+        def get_line_height(lineno: int) -> int:
+            return ui_content.get_height_for_line(lineno, width, self.get_line_prefix)
+
+        # When there is no space, reset `vertical_scroll_2` to zero and abort.
+        # This can happen if the margin is bigger than the window width.
+        # Otherwise the text height will become "infinite" (a big number) and
+        # the copy_line will spend a huge amount of iterations trying to render
+        # nothing.
+        if width <= 0:
+            self.vertical_scroll = ui_content.cursor_position.y
+            self.vertical_scroll_2 = 0
+            return
+
+        # If the current line consumes more than the whole window height,
+        # then we have to scroll vertically inside this line. (We don't take
+        # the scroll offsets into account for this.)
+        # Also, ignore the scroll offsets in this case. Just set the vertical
+        # scroll to this line.
+        line_height = get_line_height(ui_content.cursor_position.y)
+        if line_height > height - scroll_offsets_top:
+            # Calculate the height of the text before the cursor (including
+            # line prefixes).
+            text_before_height = ui_content.get_height_for_line(
+                ui_content.cursor_position.y,
+                width,
+                self.get_line_prefix,
+                slice_stop=ui_content.cursor_position.x,
+            )
+
+            # Adjust scroll offset.
+            self.vertical_scroll = ui_content.cursor_position.y
+            self.vertical_scroll_2 = min(
+                text_before_height - 1,  # Keep the cursor visible.
+                line_height
+                - height,  # Avoid blank lines at the bottom when scolling up again.
+                self.vertical_scroll_2,
+            )
+            self.vertical_scroll_2 = max(
+                0, text_before_height - height, self.vertical_scroll_2
+            )
+            return
+        else:
+            self.vertical_scroll_2 = 0
+
+        # Current line doesn't consume the whole height. Take scroll offsets into account.
+        def get_min_vertical_scroll() -> int:
+            # Make sure that the cursor line is not below the bottom.
+            # (Calculate how many lines can be shown between the cursor and the .)
+            used_height = 0
+            prev_lineno = ui_content.cursor_position.y
+
+            for lineno in range(ui_content.cursor_position.y, -1, -1):
+                used_height += get_line_height(lineno)
+
+                if used_height > height - scroll_offsets_bottom:
+                    return prev_lineno
+                else:
+                    prev_lineno = lineno
+            return 0
+
+        def get_max_vertical_scroll() -> int:
+            # Make sure that the cursor line is not above the top.
+            prev_lineno = ui_content.cursor_position.y
+            used_height = 0
+
+            for lineno in range(ui_content.cursor_position.y - 1, -1, -1):
+                used_height += get_line_height(lineno)
+
+                if used_height > scroll_offsets_top:
+                    return prev_lineno
+                else:
+                    prev_lineno = lineno
+            return prev_lineno
+
+        def get_topmost_visible() -> int:
+            """
+            Calculate the upper most line that can be visible, while the bottom
+            is still visible. We should not allow scroll more than this if
+            `allow_scroll_beyond_bottom` is false.
+            """
+            prev_lineno = ui_content.line_count - 1
+            used_height = 0
+            for lineno in range(ui_content.line_count - 1, -1, -1):
+                used_height += get_line_height(lineno)
+                if used_height > height:
+                    return prev_lineno
+                else:
+                    prev_lineno = lineno
+            return prev_lineno
+
+        # Scroll vertically. (Make sure that the whole line which contains the
+        # cursor is visible.
+        topmost_visible = get_topmost_visible()
+
+        # Note: the `min(topmost_visible, ...)` is to make sure that we
+        # don't require scrolling up because of the bottom scroll offset,
+        # when we are at the end of the document.
+        self.vertical_scroll = max(
+            self.vertical_scroll, min(topmost_visible, get_min_vertical_scroll())
+        )
+        self.vertical_scroll = min(self.vertical_scroll, get_max_vertical_scroll())
+
+        # Disallow scrolling beyond bottom?
+        if not self.allow_scroll_beyond_bottom():
+            self.vertical_scroll = min(self.vertical_scroll, topmost_visible)
+
+    def _scroll_without_linewrapping(
+        self, ui_content: UIContent, width: int, height: int
+    ) -> None:
+        """
+        Scroll to make sure the cursor position is visible and that we maintain
+        the requested scroll offset.
+
+        Set `self.horizontal_scroll/vertical_scroll`.
+        """
+        cursor_position = ui_content.cursor_position or Point(x=0, y=0)
+
+        # Without line wrapping, we will never have to scroll vertically inside
+        # a single line.
+        self.vertical_scroll_2 = 0
+
+        if ui_content.line_count == 0:
+            self.vertical_scroll = 0
+            self.horizontal_scroll = 0
+            return
+        else:
+            current_line_text = fragment_list_to_text(
+                ui_content.get_line(cursor_position.y)
+            )
+
+        def do_scroll(
+            current_scroll: int,
+            scroll_offset_start: int,
+            scroll_offset_end: int,
+            cursor_pos: int,
+            window_size: int,
+            content_size: int,
+        ) -> int:
+            "Scrolling algorithm. Used for both horizontal and vertical scrolling."
+            # Calculate the scroll offset to apply.
+            # This can obviously never be more than have the screen size. Also, when the
+            # cursor appears at the top or bottom, we don't apply the offset.
+            scroll_offset_start = int(
+                min(scroll_offset_start, window_size / 2, cursor_pos)
+            )
+            scroll_offset_end = int(
+                min(scroll_offset_end, window_size / 2, content_size - 1 - cursor_pos)
+            )
+
+            # Prevent negative scroll offsets.
+            if current_scroll < 0:
+                current_scroll = 0
+
+            # Scroll back if we scrolled to much and there's still space to show more of the document.
+            if (
+                not self.allow_scroll_beyond_bottom()
+                and current_scroll > content_size - window_size
+            ):
+                current_scroll = max(0, content_size - window_size)
+
+            # Scroll up if cursor is before visible part.
+            if current_scroll > cursor_pos - scroll_offset_start:
+                current_scroll = max(0, cursor_pos - scroll_offset_start)
+
+            # Scroll down if cursor is after visible part.
+            if current_scroll < (cursor_pos + 1) - window_size + scroll_offset_end:
+                current_scroll = (cursor_pos + 1) - window_size + scroll_offset_end
+
+            return current_scroll
+
+        # When a preferred scroll is given, take that first into account.
+        if self.get_vertical_scroll:
+            self.vertical_scroll = self.get_vertical_scroll(self)
+            assert isinstance(self.vertical_scroll, int)
+        if self.get_horizontal_scroll:
+            self.horizontal_scroll = self.get_horizontal_scroll(self)
+            assert isinstance(self.horizontal_scroll, int)
+
+        # Update horizontal/vertical scroll to make sure that the cursor
+        # remains visible.
+        offsets = self.scroll_offsets
+
+        self.vertical_scroll = do_scroll(
+            current_scroll=self.vertical_scroll,
+            scroll_offset_start=offsets.top,
+            scroll_offset_end=offsets.bottom,
+            cursor_pos=ui_content.cursor_position.y,
+            window_size=height,
+            content_size=ui_content.line_count,
+        )
+
+        if self.get_line_prefix:
+            current_line_prefix_width = fragment_list_width(
+                to_formatted_text(self.get_line_prefix(ui_content.cursor_position.y, 0))
+            )
+        else:
+            current_line_prefix_width = 0
+
+        self.horizontal_scroll = do_scroll(
+            current_scroll=self.horizontal_scroll,
+            scroll_offset_start=offsets.left,
+            scroll_offset_end=offsets.right,
+            cursor_pos=get_cwidth(current_line_text[: ui_content.cursor_position.x]),
+            window_size=width - current_line_prefix_width,
+            # We can only analyse the current line. Calculating the width off
+            # all the lines is too expensive.
+            content_size=max(
+                get_cwidth(current_line_text), self.horizontal_scroll + width
+            ),
+        )
+
+    def _mouse_handler(self, mouse_event: MouseEvent) -> "NotImplementedOrNone":
+        """
+        Mouse handler. Called when the UI control doesn't handle this
+        particular event.
+
+        Return `NotImplemented` if nothing was done as a consequence of this
+        key binding (no UI invalidate required in that case).
+        """
+        if mouse_event.event_type == MouseEventType.SCROLL_DOWN:
+            self._scroll_down()
+            return None
+        elif mouse_event.event_type == MouseEventType.SCROLL_UP:
+            self._scroll_up()
+            return None
+
+        return NotImplemented
+
+    def _scroll_down(self) -> None:
+        "Scroll window down."
+        info = self.render_info
+
+        if info is None:
+            return
+
+        if self.vertical_scroll < info.content_height - info.window_height:
+            if info.cursor_position.y <= info.configured_scroll_offsets.top:
+                self.content.move_cursor_down()
+
+            self.vertical_scroll += 1
+
+    def _scroll_up(self) -> None:
+        "Scroll window up."
+        info = self.render_info
+
+        if info is None:
+            return
+
+        if info.vertical_scroll > 0:
+            # TODO: not entirely correct yet in case of line wrapping and long lines.
+            if (
+                info.cursor_position.y
+                >= info.window_height - 1 - info.configured_scroll_offsets.bottom
+            ):
+                self.content.move_cursor_up()
+
+            self.vertical_scroll -= 1
+
+    def get_key_bindings(self) -> Optional[KeyBindingsBase]:
+        return self.content.get_key_bindings()
+
+    def get_children(self) -> List[Container]:
+        return []
+
+
+class ConditionalContainer(Container):
+    """
+    Wrapper around any other container that can change the visibility. The
+    received `filter` determines whether the given container should be
+    displayed or not.
+
+    :param content: :class:`.Container` instance.
+    :param filter: :class:`.Filter` instance.
+    """
+
+    def __init__(self, content: AnyContainer, filter: FilterOrBool) -> None:
+        self.content = to_container(content)
+        self.filter = to_filter(filter)
+
+    def __repr__(self) -> str:
+        return f"ConditionalContainer({self.content!r}, filter={self.filter!r})"
+
+    def reset(self) -> None:
+        self.content.reset()
+
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        if self.filter():
+            return self.content.preferred_width(max_available_width)
+        else:
+            return Dimension.zero()
+
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        if self.filter():
+            return self.content.preferred_height(width, max_available_height)
+        else:
+            return Dimension.zero()
+
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        if self.filter():
+            return self.content.write_to_screen(
+                screen, mouse_handlers, write_position, parent_style, erase_bg, z_index
+            )
+
+    def get_children(self) -> List[Container]:
+        return [self.content]
+
+
+class DynamicContainer(Container):
+    """
+    Container class that dynamically returns any Container.
+
+    :param get_container: Callable that returns a :class:`.Container` instance
+        or any widget with a ``__pt_container__`` method.
+    """
+
+    def __init__(self, get_container: Callable[[], AnyContainer]) -> None:
+        self.get_container = get_container
+
+    def _get_container(self) -> Container:
+        """
+        Return the current container object.
+
+        We call `to_container`, because `get_container` can also return a
+        widget with a ``__pt_container__`` method.
+        """
+        obj = self.get_container()
+        return to_container(obj)
+
+    def reset(self) -> None:
+        self._get_container().reset()
+
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        return self._get_container().preferred_width(max_available_width)
+
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        return self._get_container().preferred_height(width, max_available_height)
+
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        self._get_container().write_to_screen(
+            screen, mouse_handlers, write_position, parent_style, erase_bg, z_index
+        )
+
+    def is_modal(self) -> bool:
+        return False
+
+    def get_key_bindings(self) -> Optional[KeyBindingsBase]:
+        # Key bindings will be collected when `layout.walk()` finds the child
+        # container.
+        return None
+
+    def get_children(self) -> List[Container]:
+        # Here we have to return the current active container itself, not its
+        # children. Otherwise, we run into issues where `layout.walk()` will
+        # never see an object of type `Window` if this contains a window. We
+        # can't/shouldn't proxy the "isinstance" check.
+        return [self._get_container()]
+
+
+def to_container(container: AnyContainer) -> Container:
+    """
+    Make sure that the given object is a :class:`.Container`.
+    """
+    if isinstance(container, Container):
+        return container
+    elif hasattr(container, "__pt_container__"):
+        return to_container(container.__pt_container__())
+    else:
+        raise ValueError(f"Not a container object: {container!r}")
+
+
+def to_window(container: AnyContainer) -> Window:
+    """
+    Make sure that the given argument is a :class:`.Window`.
+    """
+    if isinstance(container, Window):
+        return container
+    elif hasattr(container, "__pt_container__"):
+        return to_window(cast("MagicContainer", container).__pt_container__())
+    else:
+        raise ValueError(f"Not a Window object: {container!r}.")
+
+
+def is_container(value: object) -> "TypeGuard[AnyContainer]":
+    """
+    Checks whether the given value is a container object
+    (for use in assert statements).
+    """
+    if isinstance(value, Container):
+        return True
+    if hasattr(value, "__pt_container__"):
+        return is_container(cast("MagicContainer", value).__pt_container__())
+    return False
diff --git a/src/prompt_toolkit/layout/controls.py b/src/prompt_toolkit/layout/controls.py
new file mode 100644
index 0000000..016d289
--- /dev/null
+++ b/src/prompt_toolkit/layout/controls.py
@@ -0,0 +1,957 @@
+"""
+User interface Controls for the layout.
+"""
+import time
+from abc import ABCMeta, abstractmethod
+from typing import (
+    TYPE_CHECKING,
+    Callable,
+    Dict,
+    Hashable,
+    Iterable,
+    List,
+    NamedTuple,
+    Optional,
+    Union,
+)
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.buffer import Buffer
+from prompt_toolkit.cache import SimpleCache
+from prompt_toolkit.data_structures import Point
+from prompt_toolkit.document import Document
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.formatted_text import (
+    AnyFormattedText,
+    StyleAndTextTuples,
+    to_formatted_text,
+)
+from prompt_toolkit.formatted_text.utils import (
+    fragment_list_to_text,
+    fragment_list_width,
+    split_lines,
+)
+from prompt_toolkit.lexers import Lexer, SimpleLexer
+from prompt_toolkit.mouse_events import MouseButton, MouseEvent, MouseEventType
+from prompt_toolkit.search import SearchState
+from prompt_toolkit.selection import SelectionType
+from prompt_toolkit.utils import get_cwidth
+
+from .processors import (
+    DisplayMultipleCursors,
+    HighlightIncrementalSearchProcessor,
+    HighlightSearchProcessor,
+    HighlightSelectionProcessor,
+    Processor,
+    TransformationInput,
+    merge_processors,
+)
+
+if TYPE_CHECKING:
+    from prompt_toolkit.key_binding.key_bindings import (
+        KeyBindingsBase,
+        NotImplementedOrNone,
+    )
+    from prompt_toolkit.utils import Event
+
+
+__all__ = [
+    "BufferControl",
+    "SearchBufferControl",
+    "DummyControl",
+    "FormattedTextControl",
+    "UIControl",
+    "UIContent",
+]
+
+GetLinePrefixCallable = Callable[[int, int], AnyFormattedText]
+
+
+class UIControl(metaclass=ABCMeta):
+    """
+    Base class for all user interface controls.
+    """
+
+    def reset(self) -> None:
+        # Default reset. (Doesn't have to be implemented.)
+        pass
+
+    def preferred_width(self, max_available_width: int) -> Optional[int]:
+        return None
+
+    def preferred_height(
+        self,
+        width: int,
+        max_available_height: int,
+        wrap_lines: bool,
+        get_line_prefix: Optional[GetLinePrefixCallable],
+    ) -> Optional[int]:
+        return None
+
+    def is_focusable(self) -> bool:
+        """
+        Tell whether this user control is focusable.
+        """
+        return False
+
+    @abstractmethod
+    def create_content(self, width: int, height: int) -> "UIContent":
+        """
+        Generate the content for this user control.
+
+        Returns a :class:`.UIContent` instance.
+        """
+
+    def mouse_handler(self, mouse_event: MouseEvent) -> "NotImplementedOrNone":
+        """
+        Handle mouse events.
+
+        When `NotImplemented` is returned, it means that the given event is not
+        handled by the `UIControl` itself. The `Window` or key bindings can
+        decide to handle this event as scrolling or changing focus.
+
+        :param mouse_event: `MouseEvent` instance.
+        """
+        return NotImplemented
+
+    def move_cursor_down(self) -> None:
+        """
+        Request to move the cursor down.
+        This happens when scrolling down and the cursor is completely at the
+        top.
+        """
+
+    def move_cursor_up(self) -> None:
+        """
+        Request to move the cursor up.
+        """
+
+    def get_key_bindings(self) -> Optional["KeyBindingsBase"]:
+        """
+        The key bindings that are specific for this user control.
+
+        Return a :class:`.KeyBindings` object if some key bindings are
+        specified, or `None` otherwise.
+        """
+
+    def get_invalidate_events(self) -> Iterable["Event[object]"]:
+        """
+        Return a list of `Event` objects. This can be a generator.
+        (The application collects all these events, in order to bind redraw
+        handlers to these events.)
+        """
+        return []
+
+
+class UIContent:
+    """
+    Content generated by a user control. This content consists of a list of
+    lines.
+
+    :param get_line: Callable that takes a line number and returns the current
+        line. This is a list of (style_str, text) tuples.
+    :param line_count: The number of lines.
+    :param cursor_position: a :class:`.Point` for the cursor position.
+    :param menu_position: a :class:`.Point` for the menu position.
+    :param show_cursor: Make the cursor visible.
+    """
+
+    def __init__(
+        self,
+        get_line: Callable[[int], StyleAndTextTuples] = (lambda i: []),
+        line_count: int = 0,
+        cursor_position: Optional[Point] = None,
+        menu_position: Optional[Point] = None,
+        show_cursor: bool = True,
+    ):
+
+        self.get_line = get_line
+        self.line_count = line_count
+        self.cursor_position = cursor_position or Point(x=0, y=0)
+        self.menu_position = menu_position
+        self.show_cursor = show_cursor
+
+        # Cache for line heights. Maps cache key -> height
+        self._line_heights_cache: Dict[Hashable, int] = {}
+
+    def __getitem__(self, lineno: int) -> StyleAndTextTuples:
+        "Make it iterable (iterate line by line)."
+        if lineno < self.line_count:
+            return self.get_line(lineno)
+        else:
+            raise IndexError
+
+    def get_height_for_line(
+        self,
+        lineno: int,
+        width: int,
+        get_line_prefix: Optional[GetLinePrefixCallable],
+        slice_stop: Optional[int] = None,
+    ) -> int:
+        """
+        Return the height that a given line would need if it is rendered in a
+        space with the given width (using line wrapping).
+
+        :param get_line_prefix: None or a `Window.get_line_prefix` callable
+            that returns the prefix to be inserted before this line.
+        :param slice_stop: Wrap only "line[:slice_stop]" and return that
+            partial result. This is needed for scrolling the window correctly
+            when line wrapping.
+        :returns: The computed height.
+        """
+        # Instead of using `get_line_prefix` as key, we use render_counter
+        # instead. This is more reliable, because this function could still be
+        # the same, while the content would change over time.
+        key = get_app().render_counter, lineno, width, slice_stop
+
+        try:
+            return self._line_heights_cache[key]
+        except KeyError:
+            if width == 0:
+                height = 10**8
+            else:
+                # Calculate line width first.
+                line = fragment_list_to_text(self.get_line(lineno))[:slice_stop]
+                text_width = get_cwidth(line)
+
+                if get_line_prefix:
+                    # Add prefix width.
+                    text_width += fragment_list_width(
+                        to_formatted_text(get_line_prefix(lineno, 0))
+                    )
+
+                    # Slower path: compute path when there's a line prefix.
+                    height = 1
+
+                    # Keep wrapping as long as the line doesn't fit.
+                    # Keep adding new prefixes for every wrapped line.
+                    while text_width > width:
+                        height += 1
+                        text_width -= width
+
+                        fragments2 = to_formatted_text(
+                            get_line_prefix(lineno, height - 1)
+                        )
+                        prefix_width = get_cwidth(fragment_list_to_text(fragments2))
+
+                        if prefix_width >= width:  # Prefix doesn't fit.
+                            height = 10**8
+                            break
+
+                        text_width += prefix_width
+                else:
+                    # Fast path: compute height when there's no line prefix.
+                    try:
+                        quotient, remainder = divmod(text_width, width)
+                    except ZeroDivisionError:
+                        height = 10**8
+                    else:
+                        if remainder:
+                            quotient += 1  # Like math.ceil.
+                        height = max(1, quotient)
+
+            # Cache and return
+            self._line_heights_cache[key] = height
+            return height
+
+
+class FormattedTextControl(UIControl):
+    """
+    Control that displays formatted text. This can be either plain text, an
+    :class:`~prompt_toolkit.formatted_text.HTML` object an
+    :class:`~prompt_toolkit.formatted_text.ANSI` object, a list of ``(style_str,
+    text)`` tuples or a callable that takes no argument and returns one of
+    those, depending on how you prefer to do the formatting. See
+    ``prompt_toolkit.layout.formatted_text`` for more information.
+
+    (It's mostly optimized for rather small widgets, like toolbars, menus, etc...)
+
+    When this UI control has the focus, the cursor will be shown in the upper
+    left corner of this control by default. There are two ways for specifying
+    the cursor position:
+
+    - Pass a `get_cursor_position` function which returns a `Point` instance
+      with the current cursor position.
+
+    - If the (formatted) text is passed as a list of ``(style, text)`` tuples
+      and there is one that looks like ``('[SetCursorPosition]', '')``, then
+      this will specify the cursor position.
+
+    Mouse support:
+
+        The list of fragments can also contain tuples of three items, looking like:
+        (style_str, text, handler). When mouse support is enabled and the user
+        clicks on this fragment, then the given handler is called. That handler
+        should accept two inputs: (Application, MouseEvent) and it should
+        either handle the event or return `NotImplemented` in case we want the
+        containing Window to handle this event.
+
+    :param focusable: `bool` or :class:`.Filter`: Tell whether this control is
+        focusable.
+
+    :param text: Text or formatted text to be displayed.
+    :param style: Style string applied to the content. (If you want to style
+        the whole :class:`~prompt_toolkit.layout.Window`, pass the style to the
+        :class:`~prompt_toolkit.layout.Window` instead.)
+    :param key_bindings: a :class:`.KeyBindings` object.
+    :param get_cursor_position: A callable that returns the cursor position as
+        a `Point` instance.
+    """
+
+    def __init__(
+        self,
+        text: AnyFormattedText = "",
+        style: str = "",
+        focusable: FilterOrBool = False,
+        key_bindings: Optional["KeyBindingsBase"] = None,
+        show_cursor: bool = True,
+        modal: bool = False,
+        get_cursor_position: Optional[Callable[[], Optional[Point]]] = None,
+    ) -> None:
+
+        self.text = text  # No type check on 'text'. This is done dynamically.
+        self.style = style
+        self.focusable = to_filter(focusable)
+
+        # Key bindings.
+        self.key_bindings = key_bindings
+        self.show_cursor = show_cursor
+        self.modal = modal
+        self.get_cursor_position = get_cursor_position
+
+        #: Cache for the content.
+        self._content_cache: SimpleCache[Hashable, UIContent] = SimpleCache(maxsize=18)
+        self._fragment_cache: SimpleCache[int, StyleAndTextTuples] = SimpleCache(
+            maxsize=1
+        )
+        # Only cache one fragment list. We don't need the previous item.
+
+        # Render info for the mouse support.
+        self._fragments: Optional[StyleAndTextTuples] = None
+
+    def reset(self) -> None:
+        self._fragments = None
+
+    def is_focusable(self) -> bool:
+        return self.focusable()
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.text!r})"
+
+    def _get_formatted_text_cached(self) -> StyleAndTextTuples:
+        """
+        Get fragments, but only retrieve fragments once during one render run.
+        (This function is called several times during one rendering, because
+        we also need those for calculating the dimensions.)
+        """
+        return self._fragment_cache.get(
+            get_app().render_counter, lambda: to_formatted_text(self.text, self.style)
+        )
+
+    def preferred_width(self, max_available_width: int) -> int:
+        """
+        Return the preferred width for this control.
+        That is the width of the longest line.
+        """
+        text = fragment_list_to_text(self._get_formatted_text_cached())
+        line_lengths = [get_cwidth(l) for l in text.split("\n")]
+        return max(line_lengths)
+
+    def preferred_height(
+        self,
+        width: int,
+        max_available_height: int,
+        wrap_lines: bool,
+        get_line_prefix: Optional[GetLinePrefixCallable],
+    ) -> Optional[int]:
+        """
+        Return the preferred height for this control.
+        """
+        content = self.create_content(width, None)
+        if wrap_lines:
+            height = 0
+            for i in range(content.line_count):
+                height += content.get_height_for_line(i, width, get_line_prefix)
+                if height >= max_available_height:
+                    return max_available_height
+            return height
+        else:
+            return content.line_count
+
+    def create_content(self, width: int, height: Optional[int]) -> UIContent:
+        # Get fragments
+        fragments_with_mouse_handlers = self._get_formatted_text_cached()
+        fragment_lines_with_mouse_handlers = list(
+            split_lines(fragments_with_mouse_handlers)
+        )
+
+        # Strip mouse handlers from fragments.
+        fragment_lines: List[StyleAndTextTuples] = [
+            [(item[0], item[1]) for item in line]
+            for line in fragment_lines_with_mouse_handlers
+        ]
+
+        # Keep track of the fragments with mouse handler, for later use in
+        # `mouse_handler`.
+        self._fragments = fragments_with_mouse_handlers
+
+        # If there is a `[SetCursorPosition]` in the fragment list, set the
+        # cursor position here.
+        def get_cursor_position(
+            fragment: str = "[SetCursorPosition]",
+        ) -> Optional[Point]:
+            for y, line in enumerate(fragment_lines):
+                x = 0
+                for style_str, text, *_ in line:
+                    if fragment in style_str:
+                        return Point(x=x, y=y)
+                    x += len(text)
+            return None
+
+        # If there is a `[SetMenuPosition]`, set the menu over here.
+        def get_menu_position() -> Optional[Point]:
+            return get_cursor_position("[SetMenuPosition]")
+
+        cursor_position = (self.get_cursor_position or get_cursor_position)()
+
+        # Create content, or take it from the cache.
+        key = (tuple(fragments_with_mouse_handlers), width, cursor_position)
+
+        def get_content() -> UIContent:
+            return UIContent(
+                get_line=lambda i: fragment_lines[i],
+                line_count=len(fragment_lines),
+                show_cursor=self.show_cursor,
+                cursor_position=cursor_position,
+                menu_position=get_menu_position(),
+            )
+
+        return self._content_cache.get(key, get_content)
+
+    def mouse_handler(self, mouse_event: MouseEvent) -> "NotImplementedOrNone":
+        """
+        Handle mouse events.
+
+        (When the fragment list contained mouse handlers and the user clicked on
+        on any of these, the matching handler is called. This handler can still
+        return `NotImplemented` in case we want the
+        :class:`~prompt_toolkit.layout.Window` to handle this particular
+        event.)
+        """
+        if self._fragments:
+            # Read the generator.
+            fragments_for_line = list(split_lines(self._fragments))
+
+            try:
+                fragments = fragments_for_line[mouse_event.position.y]
+            except IndexError:
+                return NotImplemented
+            else:
+                # Find position in the fragment list.
+                xpos = mouse_event.position.x
+
+                # Find mouse handler for this character.
+                count = 0
+                for item in fragments:
+                    count += len(item[1])
+                    if count > xpos:
+                        if len(item) >= 3:
+                            # Handler found. Call it.
+                            # (Handler can return NotImplemented, so return
+                            # that result.)
+                            handler = item[2]  # type: ignore
+                            return handler(mouse_event)
+                        else:
+                            break
+
+        # Otherwise, don't handle here.
+        return NotImplemented
+
+    def is_modal(self) -> bool:
+        return self.modal
+
+    def get_key_bindings(self) -> Optional["KeyBindingsBase"]:
+        return self.key_bindings
+
+
+class DummyControl(UIControl):
+    """
+    A dummy control object that doesn't paint any content.
+
+    Useful for filling a :class:`~prompt_toolkit.layout.Window`. (The
+    `fragment` and `char` attributes of the `Window` class can be used to
+    define the filling.)
+    """
+
+    def create_content(self, width: int, height: int) -> UIContent:
+        def get_line(i: int) -> StyleAndTextTuples:
+            return []
+
+        return UIContent(
+            get_line=get_line, line_count=100**100
+        )  # Something very big.
+
+    def is_focusable(self) -> bool:
+        return False
+
+
+class _ProcessedLine(NamedTuple):
+    fragments: StyleAndTextTuples
+    source_to_display: Callable[[int], int]
+    display_to_source: Callable[[int], int]
+
+
+class BufferControl(UIControl):
+    """
+    Control for visualising the content of a :class:`.Buffer`.
+
+    :param buffer: The :class:`.Buffer` object to be displayed.
+    :param input_processors: A list of
+        :class:`~prompt_toolkit.layout.processors.Processor` objects.
+    :param include_default_input_processors: When True, include the default
+        processors for highlighting of selection, search and displaying of
+        multiple cursors.
+    :param lexer: :class:`.Lexer` instance for syntax highlighting.
+    :param preview_search: `bool` or :class:`.Filter`: Show search while
+        typing. When this is `True`, probably you want to add a
+        ``HighlightIncrementalSearchProcessor`` as well. Otherwise only the
+        cursor position will move, but the text won't be highlighted.
+    :param focusable: `bool` or :class:`.Filter`: Tell whether this control is focusable.
+    :param focus_on_click: Focus this buffer when it's click, but not yet focused.
+    :param key_bindings: a :class:`.KeyBindings` object.
+    """
+
+    def __init__(
+        self,
+        buffer: Optional[Buffer] = None,
+        input_processors: Optional[List[Processor]] = None,
+        include_default_input_processors: bool = True,
+        lexer: Optional[Lexer] = None,
+        preview_search: FilterOrBool = False,
+        focusable: FilterOrBool = True,
+        search_buffer_control: Union[
+            None, "SearchBufferControl", Callable[[], "SearchBufferControl"]
+        ] = None,
+        menu_position: Optional[Callable[[], Optional[int]]] = None,
+        focus_on_click: FilterOrBool = False,
+        key_bindings: Optional["KeyBindingsBase"] = None,
+    ):
+
+        self.input_processors = input_processors
+        self.include_default_input_processors = include_default_input_processors
+
+        self.default_input_processors = [
+            HighlightSearchProcessor(),
+            HighlightIncrementalSearchProcessor(),
+            HighlightSelectionProcessor(),
+            DisplayMultipleCursors(),
+        ]
+
+        self.preview_search = to_filter(preview_search)
+        self.focusable = to_filter(focusable)
+        self.focus_on_click = to_filter(focus_on_click)
+
+        self.buffer = buffer or Buffer()
+        self.menu_position = menu_position
+        self.lexer = lexer or SimpleLexer()
+        self.key_bindings = key_bindings
+        self._search_buffer_control = search_buffer_control
+
+        #: Cache for the lexer.
+        #: Often, due to cursor movement, undo/redo and window resizing
+        #: operations, it happens that a short time, the same document has to be
+        #: lexed. This is a fairly easy way to cache such an expensive operation.
+        self._fragment_cache: SimpleCache[
+            Hashable, Callable[[int], StyleAndTextTuples]
+        ] = SimpleCache(maxsize=8)
+
+        self._last_click_timestamp: Optional[float] = None
+        self._last_get_processed_line: Optional[Callable[[int], _ProcessedLine]] = None
+
+    def __repr__(self) -> str:
+        return f"<{self.__class__.__name__} buffer={self.buffer!r} at {id(self)!r}>"
+
+    @property
+    def search_buffer_control(self) -> Optional["SearchBufferControl"]:
+        result: Optional[SearchBufferControl]
+
+        if callable(self._search_buffer_control):
+            result = self._search_buffer_control()
+        else:
+            result = self._search_buffer_control
+
+        assert result is None or isinstance(result, SearchBufferControl)
+        return result
+
+    @property
+    def search_buffer(self) -> Optional[Buffer]:
+        control = self.search_buffer_control
+        if control is not None:
+            return control.buffer
+        return None
+
+    @property
+    def search_state(self) -> SearchState:
+        """
+        Return the `SearchState` for searching this `BufferControl`. This is
+        always associated with the search control. If one search bar is used
+        for searching multiple `BufferControls`, then they share the same
+        `SearchState`.
+        """
+        search_buffer_control = self.search_buffer_control
+        if search_buffer_control:
+            return search_buffer_control.searcher_search_state
+        else:
+            return SearchState()
+
+    def is_focusable(self) -> bool:
+        return self.focusable()
+
+    def preferred_width(self, max_available_width: int) -> Optional[int]:
+        """
+        This should return the preferred width.
+
+        Note: We don't specify a preferred width according to the content,
+              because it would be too expensive. Calculating the preferred
+              width can be done by calculating the longest line, but this would
+              require applying all the processors to each line. This is
+              unfeasible for a larger document, and doing it for small
+              documents only would result in inconsistent behaviour.
+        """
+        return None
+
+    def preferred_height(
+        self,
+        width: int,
+        max_available_height: int,
+        wrap_lines: bool,
+        get_line_prefix: Optional[GetLinePrefixCallable],
+    ) -> Optional[int]:
+
+        # Calculate the content height, if it was drawn on a screen with the
+        # given width.
+        height = 0
+        content = self.create_content(width, height=1)  # Pass a dummy '1' as height.
+
+        # When line wrapping is off, the height should be equal to the amount
+        # of lines.
+        if not wrap_lines:
+            return content.line_count
+
+        # When the number of lines exceeds the max_available_height, just
+        # return max_available_height. No need to calculate anything.
+        if content.line_count >= max_available_height:
+            return max_available_height
+
+        for i in range(content.line_count):
+            height += content.get_height_for_line(i, width, get_line_prefix)
+
+            if height >= max_available_height:
+                return max_available_height
+
+        return height
+
+    def _get_formatted_text_for_line_func(
+        self, document: Document
+    ) -> Callable[[int], StyleAndTextTuples]:
+        """
+        Create a function that returns the fragments for a given line.
+        """
+        # Cache using `document.text`.
+        def get_formatted_text_for_line() -> Callable[[int], StyleAndTextTuples]:
+            return self.lexer.lex_document(document)
+
+        key = (document.text, self.lexer.invalidation_hash())
+        return self._fragment_cache.get(key, get_formatted_text_for_line)
+
+    def _create_get_processed_line_func(
+        self, document: Document, width: int, height: int
+    ) -> Callable[[int], _ProcessedLine]:
+        """
+        Create a function that takes a line number of the current document and
+        returns a _ProcessedLine(processed_fragments, source_to_display, display_to_source)
+        tuple.
+        """
+        # Merge all input processors together.
+        input_processors = self.input_processors or []
+        if self.include_default_input_processors:
+            input_processors = self.default_input_processors + input_processors
+
+        merged_processor = merge_processors(input_processors)
+
+        def transform(lineno: int, fragments: StyleAndTextTuples) -> _ProcessedLine:
+            "Transform the fragments for a given line number."
+            # Get cursor position at this line.
+            def source_to_display(i: int) -> int:
+                """X position from the buffer to the x position in the
+                processed fragment list. By default, we start from the 'identity'
+                operation."""
+                return i
+
+            transformation = merged_processor.apply_transformation(
+                TransformationInput(
+                    self, document, lineno, source_to_display, fragments, width, height
+                )
+            )
+
+            return _ProcessedLine(
+                transformation.fragments,
+                transformation.source_to_display,
+                transformation.display_to_source,
+            )
+
+        def create_func() -> Callable[[int], _ProcessedLine]:
+            get_line = self._get_formatted_text_for_line_func(document)
+            cache: Dict[int, _ProcessedLine] = {}
+
+            def get_processed_line(i: int) -> _ProcessedLine:
+                try:
+                    return cache[i]
+                except KeyError:
+                    processed_line = transform(i, get_line(i))
+                    cache[i] = processed_line
+                    return processed_line
+
+            return get_processed_line
+
+        return create_func()
+
+    def create_content(
+        self, width: int, height: int, preview_search: bool = False
+    ) -> UIContent:
+        """
+        Create a UIContent.
+        """
+        buffer = self.buffer
+
+        # Trigger history loading of the buffer. We do this during the
+        # rendering of the UI here, because it needs to happen when an
+        # `Application` with its event loop is running. During the rendering of
+        # the buffer control is the earliest place we can achieve this, where
+        # we're sure the right event loop is active, and don't require user
+        # interaction (like in a key binding).
+        buffer.load_history_if_not_yet_loaded()
+
+        # Get the document to be shown. If we are currently searching (the
+        # search buffer has focus, and the preview_search filter is enabled),
+        # then use the search document, which has possibly a different
+        # text/cursor position.)
+        search_control = self.search_buffer_control
+        preview_now = preview_search or bool(
+            # Only if this feature is enabled.
+            self.preview_search()
+            and
+            # And something was typed in the associated search field.
+            search_control
+            and search_control.buffer.text
+            and
+            # And we are searching in this control. (Many controls can point to
+            # the same search field, like in Pyvim.)
+            get_app().layout.search_target_buffer_control == self
+        )
+
+        if preview_now and search_control is not None:
+            ss = self.search_state
+
+            document = buffer.document_for_search(
+                SearchState(
+                    text=search_control.buffer.text,
+                    direction=ss.direction,
+                    ignore_case=ss.ignore_case,
+                )
+            )
+        else:
+            document = buffer.document
+
+        get_processed_line = self._create_get_processed_line_func(
+            document, width, height
+        )
+        self._last_get_processed_line = get_processed_line
+
+        def translate_rowcol(row: int, col: int) -> Point:
+            "Return the content column for this coordinate."
+            return Point(x=get_processed_line(row).source_to_display(col), y=row)
+
+        def get_line(i: int) -> StyleAndTextTuples:
+            "Return the fragments for a given line number."
+            fragments = get_processed_line(i).fragments
+
+            # Add a space at the end, because that is a possible cursor
+            # position. (When inserting after the input.) We should do this on
+            # all the lines, not just the line containing the cursor. (Because
+            # otherwise, line wrapping/scrolling could change when moving the
+            # cursor around.)
+            fragments = fragments + [("", " ")]
+            return fragments
+
+        content = UIContent(
+            get_line=get_line,
+            line_count=document.line_count,
+            cursor_position=translate_rowcol(
+                document.cursor_position_row, document.cursor_position_col
+            ),
+        )
+
+        # If there is an auto completion going on, use that start point for a
+        # pop-up menu position. (But only when this buffer has the focus --
+        # there is only one place for a menu, determined by the focused buffer.)
+        if get_app().layout.current_control == self:
+            menu_position = self.menu_position() if self.menu_position else None
+            if menu_position is not None:
+                assert isinstance(menu_position, int)
+                menu_row, menu_col = buffer.document.translate_index_to_position(
+                    menu_position
+                )
+                content.menu_position = translate_rowcol(menu_row, menu_col)
+            elif buffer.complete_state:
+                # Position for completion menu.
+                # Note: We use 'min', because the original cursor position could be
+                #       behind the input string when the actual completion is for
+                #       some reason shorter than the text we had before. (A completion
+                #       can change and shorten the input.)
+                menu_row, menu_col = buffer.document.translate_index_to_position(
+                    min(
+                        buffer.cursor_position,
+                        buffer.complete_state.original_document.cursor_position,
+                    )
+                )
+                content.menu_position = translate_rowcol(menu_row, menu_col)
+            else:
+                content.menu_position = None
+
+        return content
+
+    def mouse_handler(self, mouse_event: MouseEvent) -> "NotImplementedOrNone":
+        """
+        Mouse handler for this control.
+        """
+        buffer = self.buffer
+        position = mouse_event.position
+
+        # Focus buffer when clicked.
+        if get_app().layout.current_control == self:
+            if self._last_get_processed_line:
+                processed_line = self._last_get_processed_line(position.y)
+
+                # Translate coordinates back to the cursor position of the
+                # original input.
+                xpos = processed_line.display_to_source(position.x)
+                index = buffer.document.translate_row_col_to_index(position.y, xpos)
+
+                # Set the cursor position.
+                if mouse_event.event_type == MouseEventType.MOUSE_DOWN:
+                    buffer.exit_selection()
+                    buffer.cursor_position = index
+
+                elif (
+                    mouse_event.event_type == MouseEventType.MOUSE_MOVE
+                    and mouse_event.button != MouseButton.NONE
+                ):
+                    # Click and drag to highlight a selection
+                    if (
+                        buffer.selection_state is None
+                        and abs(buffer.cursor_position - index) > 0
+                    ):
+                        buffer.start_selection(selection_type=SelectionType.CHARACTERS)
+                    buffer.cursor_position = index
+
+                elif mouse_event.event_type == MouseEventType.MOUSE_UP:
+                    # When the cursor was moved to another place, select the text.
+                    # (The >1 is actually a small but acceptable workaround for
+                    # selecting text in Vi navigation mode. In navigation mode,
+                    # the cursor can never be after the text, so the cursor
+                    # will be repositioned automatically.)
+                    if abs(buffer.cursor_position - index) > 1:
+                        if buffer.selection_state is None:
+                            buffer.start_selection(
+                                selection_type=SelectionType.CHARACTERS
+                            )
+                        buffer.cursor_position = index
+
+                    # Select word around cursor on double click.
+                    # Two MOUSE_UP events in a short timespan are considered a double click.
+                    double_click = (
+                        self._last_click_timestamp
+                        and time.time() - self._last_click_timestamp < 0.3
+                    )
+                    self._last_click_timestamp = time.time()
+
+                    if double_click:
+                        start, end = buffer.document.find_boundaries_of_current_word()
+                        buffer.cursor_position += start
+                        buffer.start_selection(selection_type=SelectionType.CHARACTERS)
+                        buffer.cursor_position += end - start
+                else:
+                    # Don't handle scroll events here.
+                    return NotImplemented
+
+        # Not focused, but focusing on click events.
+        else:
+            if (
+                self.focus_on_click()
+                and mouse_event.event_type == MouseEventType.MOUSE_UP
+            ):
+                # Focus happens on mouseup. (If we did this on mousedown, the
+                # up event will be received at the point where this widget is
+                # focused and be handled anyway.)
+                get_app().layout.current_control = self
+            else:
+                return NotImplemented
+
+        return None
+
+    def move_cursor_down(self) -> None:
+        b = self.buffer
+        b.cursor_position += b.document.get_cursor_down_position()
+
+    def move_cursor_up(self) -> None:
+        b = self.buffer
+        b.cursor_position += b.document.get_cursor_up_position()
+
+    def get_key_bindings(self) -> Optional["KeyBindingsBase"]:
+        """
+        When additional key bindings are given. Return these.
+        """
+        return self.key_bindings
+
+    def get_invalidate_events(self) -> Iterable["Event[object]"]:
+        """
+        Return the Window invalidate events.
+        """
+        # Whenever the buffer changes, the UI has to be updated.
+        yield self.buffer.on_text_changed
+        yield self.buffer.on_cursor_position_changed
+
+        yield self.buffer.on_completions_changed
+        yield self.buffer.on_suggestion_set
+
+
+class SearchBufferControl(BufferControl):
+    """
+    :class:`.BufferControl` which is used for searching another
+    :class:`.BufferControl`.
+
+    :param ignore_case: Search case insensitive.
+    """
+
+    def __init__(
+        self,
+        buffer: Optional[Buffer] = None,
+        input_processors: Optional[List[Processor]] = None,
+        lexer: Optional[Lexer] = None,
+        focus_on_click: FilterOrBool = False,
+        key_bindings: Optional["KeyBindingsBase"] = None,
+        ignore_case: FilterOrBool = False,
+    ):
+
+        super().__init__(
+            buffer=buffer,
+            input_processors=input_processors,
+            lexer=lexer,
+            focus_on_click=focus_on_click,
+            key_bindings=key_bindings,
+        )
+
+        # If this BufferControl is used as a search field for one or more other
+        # BufferControls, then represents the search state.
+        self.searcher_search_state = SearchState(ignore_case=ignore_case)
diff --git a/src/prompt_toolkit/layout/dimension.py b/src/prompt_toolkit/layout/dimension.py
new file mode 100644
index 0000000..04c2163
--- /dev/null
+++ b/src/prompt_toolkit/layout/dimension.py
@@ -0,0 +1,217 @@
+"""
+Layout dimensions are used to give the minimum, maximum and preferred
+dimensions for containers and controls.
+"""
+from typing import TYPE_CHECKING, Any, Callable, List, Optional, Union
+
+__all__ = [
+    "Dimension",
+    "D",
+    "sum_layout_dimensions",
+    "max_layout_dimensions",
+    "AnyDimension",
+    "to_dimension",
+    "is_dimension",
+]
+
+if TYPE_CHECKING:
+    from typing_extensions import TypeGuard
+
+
+class Dimension:
+    """
+    Specified dimension (width/height) of a user control or window.
+
+    The layout engine tries to honor the preferred size. If that is not
+    possible, because the terminal is larger or smaller, it tries to keep in
+    between min and max.
+
+    :param min: Minimum size.
+    :param max: Maximum size.
+    :param weight: For a VSplit/HSplit, the actual size will be determined
+                   by taking the proportion of weights from all the children.
+                   E.g. When there are two children, one with a weight of 1,
+                   and the other with a weight of 2, the second will always be
+                   twice as big as the first, if the min/max values allow it.
+    :param preferred: Preferred size.
+    """
+
+    def __init__(
+        self,
+        min: Optional[int] = None,
+        max: Optional[int] = None,
+        weight: Optional[int] = None,
+        preferred: Optional[int] = None,
+    ) -> None:
+        if weight is not None:
+            assert weight >= 0  # Also cannot be a float.
+
+        assert min is None or min >= 0
+        assert max is None or max >= 0
+        assert preferred is None or preferred >= 0
+
+        self.min_specified = min is not None
+        self.max_specified = max is not None
+        self.preferred_specified = preferred is not None
+        self.weight_specified = weight is not None
+
+        if min is None:
+            min = 0  # Smallest possible value.
+        if max is None:  # 0-values are allowed, so use "is None"
+            max = 1000**10  # Something huge.
+        if preferred is None:
+            preferred = min
+        if weight is None:
+            weight = 1
+
+        self.min = min
+        self.max = max
+        self.preferred = preferred
+        self.weight = weight
+
+        # Don't allow situations where max < min. (This would be a bug.)
+        if max < min:
+            raise ValueError("Invalid Dimension: max < min.")
+
+        # Make sure that the 'preferred' size is always in the min..max range.
+        if self.preferred < self.min:
+            self.preferred = self.min
+
+        if self.preferred > self.max:
+            self.preferred = self.max
+
+    @classmethod
+    def exact(cls, amount: int) -> "Dimension":
+        """
+        Return a :class:`.Dimension` with an exact size. (min, max and
+        preferred set to ``amount``).
+        """
+        return cls(min=amount, max=amount, preferred=amount)
+
+    @classmethod
+    def zero(cls) -> "Dimension":
+        """
+        Create a dimension that represents a zero size. (Used for 'invisible'
+        controls.)
+        """
+        return cls.exact(amount=0)
+
+    def is_zero(self) -> bool:
+        "True if this `Dimension` represents a zero size."
+        return self.preferred == 0 or self.max == 0
+
+    def __repr__(self) -> str:
+        fields = []
+        if self.min_specified:
+            fields.append("min=%r" % self.min)
+        if self.max_specified:
+            fields.append("max=%r" % self.max)
+        if self.preferred_specified:
+            fields.append("preferred=%r" % self.preferred)
+        if self.weight_specified:
+            fields.append("weight=%r" % self.weight)
+
+        return "Dimension(%s)" % ", ".join(fields)
+
+
+def sum_layout_dimensions(dimensions: List[Dimension]) -> Dimension:
+    """
+    Sum a list of :class:`.Dimension` instances.
+    """
+    min = sum(d.min for d in dimensions)
+    max = sum(d.max for d in dimensions)
+    preferred = sum(d.preferred for d in dimensions)
+
+    return Dimension(min=min, max=max, preferred=preferred)
+
+
+def max_layout_dimensions(dimensions: List[Dimension]) -> Dimension:
+    """
+    Take the maximum of a list of :class:`.Dimension` instances.
+    Used when we have a HSplit/VSplit, and we want to get the best width/height.)
+    """
+    if not len(dimensions):
+        return Dimension.zero()
+
+    # If all dimensions are size zero. Return zero.
+    # (This is important for HSplit/VSplit, to report the right values to their
+    # parent when all children are invisible.)
+    if all(d.is_zero() for d in dimensions):
+        return dimensions[0]
+
+    # Ignore empty dimensions. (They should not reduce the size of others.)
+    dimensions = [d for d in dimensions if not d.is_zero()]
+
+    if dimensions:
+        # Take the highest minimum dimension.
+        min_ = max(d.min for d in dimensions)
+
+        # For the maximum, we would prefer not to go larger than then smallest
+        # 'max' value, unless other dimensions have a bigger preferred value.
+        # This seems to work best:
+        #  - We don't want that a widget with a small height in a VSplit would
+        #    shrink other widgets in the split.
+        # If it doesn't work well enough, then it's up to the UI designer to
+        # explicitly pass dimensions.
+        max_ = min(d.max for d in dimensions)
+        max_ = max(max_, max(d.preferred for d in dimensions))
+
+        # Make sure that min>=max. In some scenarios, when certain min..max
+        # ranges don't have any overlap, we can end up in such an impossible
+        # situation. In that case, give priority to the max value.
+        # E.g. taking (1..5) and (8..9) would return (8..5). Instead take (8..8).
+        if min_ > max_:
+            max_ = min_
+
+        preferred = max(d.preferred for d in dimensions)
+
+        return Dimension(min=min_, max=max_, preferred=preferred)
+    else:
+        return Dimension()
+
+
+# Anything that can be converted to a dimension.
+AnyDimension = Union[
+    None,  # None is a valid dimension that will fit anything.
+    int,
+    Dimension,
+    # Callable[[], 'AnyDimension']  # Recursive definition not supported by mypy.
+    Callable[[], Any],
+]
+
+
+def to_dimension(value: AnyDimension) -> Dimension:
+    """
+    Turn the given object into a `Dimension` object.
+    """
+    if value is None:
+        return Dimension()
+    if isinstance(value, int):
+        return Dimension.exact(value)
+    if isinstance(value, Dimension):
+        return value
+    if callable(value):
+        return to_dimension(value())
+
+    raise ValueError("Not an integer or Dimension object.")
+
+
+def is_dimension(value: object) -> "TypeGuard[AnyDimension]":
+    """
+    Test whether the given value could be a valid dimension.
+    (For usage in an assertion. It's not guaranteed in case of a callable.)
+    """
+    if value is None:
+        return True
+    if callable(value):
+        return True  # Assume it's a callable that doesn't take arguments.
+    if isinstance(value, (int, Dimension)):
+        return True
+    return False
+
+
+# Common alias.
+D = Dimension
+
+# For backward-compatibility.
+LayoutDimension = Dimension
diff --git a/src/prompt_toolkit/layout/dummy.py b/src/prompt_toolkit/layout/dummy.py
new file mode 100644
index 0000000..dcd54e9
--- /dev/null
+++ b/src/prompt_toolkit/layout/dummy.py
@@ -0,0 +1,37 @@
+"""
+Dummy layout. Used when somebody creates an `Application` without specifying a
+`Layout`.
+"""
+from prompt_toolkit.formatted_text import HTML
+from prompt_toolkit.key_binding import KeyBindings
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+
+from .containers import Window
+from .controls import FormattedTextControl
+from .dimension import D
+from .layout import Layout
+
+__all__ = [
+    "create_dummy_layout",
+]
+
+E = KeyPressEvent
+
+
+def create_dummy_layout() -> Layout:
+    """
+    Create a dummy layout for use in an 'Application' that doesn't have a
+    layout specified. When ENTER is pressed, the application quits.
+    """
+    kb = KeyBindings()
+
+    @kb.add("enter")
+    def enter(event: E) -> None:
+        event.app.exit()
+
+    control = FormattedTextControl(
+        HTML("No layout specified. Press <reverse>ENTER</reverse> to quit."),
+        key_bindings=kb,
+    )
+    window = Window(content=control, height=D(min=1))
+    return Layout(container=window, focused_element=window)
diff --git a/src/prompt_toolkit/layout/layout.py b/src/prompt_toolkit/layout/layout.py
new file mode 100644
index 0000000..62a3184
--- /dev/null
+++ b/src/prompt_toolkit/layout/layout.py
@@ -0,0 +1,411 @@
+"""
+Wrapper for the layout.
+"""
+from typing import Dict, Generator, Iterable, List, Optional, Union
+
+from prompt_toolkit.buffer import Buffer
+
+from .containers import (
+    AnyContainer,
+    ConditionalContainer,
+    Container,
+    Window,
+    to_container,
+)
+from .controls import BufferControl, SearchBufferControl, UIControl
+
+__all__ = [
+    "Layout",
+    "InvalidLayoutError",
+    "walk",
+]
+
+FocusableElement = Union[str, Buffer, UIControl, AnyContainer]
+
+
+class Layout:
+    """
+    The layout for a prompt_toolkit
+    :class:`~prompt_toolkit.application.Application`.
+    This also keeps track of which user control is focused.
+
+    :param container: The "root" container for the layout.
+    :param focused_element: element to be focused initially. (Can be anything
+        the `focus` function accepts.)
+    """
+
+    def __init__(
+        self,
+        container: AnyContainer,
+        focused_element: Optional[FocusableElement] = None,
+    ) -> None:
+
+        self.container = to_container(container)
+        self._stack: List[Window] = []
+
+        # Map search BufferControl back to the original BufferControl.
+        # This is used to keep track of when exactly we are searching, and for
+        # applying the search.
+        # When a link exists in this dictionary, that means the search is
+        # currently active.
+        # Map: search_buffer_control -> original buffer control.
+        self.search_links: Dict[SearchBufferControl, BufferControl] = {}
+
+        # Mapping that maps the children in the layout to their parent.
+        # This relationship is calculated dynamically, each time when the UI
+        # is rendered.  (UI elements have only references to their children.)
+        self._child_to_parent: Dict[Container, Container] = {}
+
+        if focused_element is None:
+            try:
+                self._stack.append(next(self.find_all_windows()))
+            except StopIteration as e:
+                raise InvalidLayoutError(
+                    "Invalid layout. The layout does not contain any Window object."
+                ) from e
+        else:
+            self.focus(focused_element)
+
+        # List of visible windows.
+        self.visible_windows: List[Window] = []  # List of `Window` objects.
+
+    def __repr__(self) -> str:
+        return f"Layout({self.container!r}, current_window={self.current_window!r})"
+
+    def find_all_windows(self) -> Generator[Window, None, None]:
+        """
+        Find all the :class:`.UIControl` objects in this layout.
+        """
+        for item in self.walk():
+            if isinstance(item, Window):
+                yield item
+
+    def find_all_controls(self) -> Iterable[UIControl]:
+        for container in self.find_all_windows():
+            yield container.content
+
+    def focus(self, value: FocusableElement) -> None:
+        """
+        Focus the given UI element.
+
+        `value` can be either:
+
+        - a :class:`.UIControl`
+        - a :class:`.Buffer` instance or the name of a :class:`.Buffer`
+        - a :class:`.Window`
+        - Any container object. In this case we will focus the :class:`.Window`
+          from this container that was focused most recent, or the very first
+          focusable :class:`.Window` of the container.
+        """
+        # BufferControl by buffer name.
+        if isinstance(value, str):
+            for control in self.find_all_controls():
+                if isinstance(control, BufferControl) and control.buffer.name == value:
+                    self.focus(control)
+                    return
+            raise ValueError(f"Couldn't find Buffer in the current layout: {value!r}.")
+
+        # BufferControl by buffer object.
+        elif isinstance(value, Buffer):
+            for control in self.find_all_controls():
+                if isinstance(control, BufferControl) and control.buffer == value:
+                    self.focus(control)
+                    return
+            raise ValueError(f"Couldn't find Buffer in the current layout: {value!r}.")
+
+        # Focus UIControl.
+        elif isinstance(value, UIControl):
+            if value not in self.find_all_controls():
+                raise ValueError(
+                    "Invalid value. Container does not appear in the layout."
+                )
+            if not value.is_focusable():
+                raise ValueError("Invalid value. UIControl is not focusable.")
+
+            self.current_control = value
+
+        # Otherwise, expecting any Container object.
+        else:
+            value = to_container(value)
+
+            if isinstance(value, Window):
+                # This is a `Window`: focus that.
+                if value not in self.find_all_windows():
+                    raise ValueError(
+                        "Invalid value. Window does not appear in the layout: %r"
+                        % (value,)
+                    )
+
+                self.current_window = value
+            else:
+                # Focus a window in this container.
+                # If we have many windows as part of this container, and some
+                # of them have been focused before, take the last focused
+                # item. (This is very useful when the UI is composed of more
+                # complex sub components.)
+                windows = []
+                for c in walk(value, skip_hidden=True):
+                    if isinstance(c, Window) and c.content.is_focusable():
+                        windows.append(c)
+
+                # Take the first one that was focused before.
+                for w in reversed(self._stack):
+                    if w in windows:
+                        self.current_window = w
+                        return
+
+                # None was focused before: take the very first focusable window.
+                if windows:
+                    self.current_window = windows[0]
+                    return
+
+                raise ValueError(
+                    f"Invalid value. Container cannot be focused: {value!r}"
+                )
+
+    def has_focus(self, value: FocusableElement) -> bool:
+        """
+        Check whether the given control has the focus.
+        :param value: :class:`.UIControl` or :class:`.Window` instance.
+        """
+        if isinstance(value, str):
+            if self.current_buffer is None:
+                return False
+            return self.current_buffer.name == value
+        if isinstance(value, Buffer):
+            return self.current_buffer == value
+        if isinstance(value, UIControl):
+            return self.current_control == value
+        else:
+            value = to_container(value)
+            if isinstance(value, Window):
+                return self.current_window == value
+            else:
+                # Check whether this "container" is focused. This is true if
+                # one of the elements inside is focused.
+                for element in walk(value):
+                    if element == self.current_window:
+                        return True
+                return False
+
+    @property
+    def current_control(self) -> UIControl:
+        """
+        Get the :class:`.UIControl` to currently has the focus.
+        """
+        return self._stack[-1].content
+
+    @current_control.setter
+    def current_control(self, control: UIControl) -> None:
+        """
+        Set the :class:`.UIControl` to receive the focus.
+        """
+        for window in self.find_all_windows():
+            if window.content == control:
+                self.current_window = window
+                return
+
+        raise ValueError("Control not found in the user interface.")
+
+    @property
+    def current_window(self) -> Window:
+        "Return the :class:`.Window` object that is currently focused."
+        return self._stack[-1]
+
+    @current_window.setter
+    def current_window(self, value: Window) -> None:
+        "Set the :class:`.Window` object to be currently focused."
+        self._stack.append(value)
+
+    @property
+    def is_searching(self) -> bool:
+        "True if we are searching right now."
+        return self.current_control in self.search_links
+
+    @property
+    def search_target_buffer_control(self) -> Optional[BufferControl]:
+        """
+        Return the :class:`.BufferControl` in which we are searching or `None`.
+        """
+        # Not every `UIControl` is a `BufferControl`. This only applies to
+        # `BufferControl`.
+        control = self.current_control
+
+        if isinstance(control, SearchBufferControl):
+            return self.search_links.get(control)
+        else:
+            return None
+
+    def get_focusable_windows(self) -> Iterable[Window]:
+        """
+        Return all the :class:`.Window` objects which are focusable (in the
+        'modal' area).
+        """
+        for w in self.walk_through_modal_area():
+            if isinstance(w, Window) and w.content.is_focusable():
+                yield w
+
+    def get_visible_focusable_windows(self) -> List[Window]:
+        """
+        Return a list of :class:`.Window` objects that are focusable.
+        """
+        # focusable windows are windows that are visible, but also part of the
+        # modal container. Make sure to keep the ordering.
+        visible_windows = self.visible_windows
+        return [w for w in self.get_focusable_windows() if w in visible_windows]
+
+    @property
+    def current_buffer(self) -> Optional[Buffer]:
+        """
+        The currently focused :class:`~.Buffer` or `None`.
+        """
+        ui_control = self.current_control
+        if isinstance(ui_control, BufferControl):
+            return ui_control.buffer
+        return None
+
+    def get_buffer_by_name(self, buffer_name: str) -> Optional[Buffer]:
+        """
+        Look in the layout for a buffer with the given name.
+        Return `None` when nothing was found.
+        """
+        for w in self.walk():
+            if isinstance(w, Window) and isinstance(w.content, BufferControl):
+                if w.content.buffer.name == buffer_name:
+                    return w.content.buffer
+        return None
+
+    @property
+    def buffer_has_focus(self) -> bool:
+        """
+        Return `True` if the currently focused control is a
+        :class:`.BufferControl`. (For instance, used to determine whether the
+        default key bindings should be active or not.)
+        """
+        ui_control = self.current_control
+        return isinstance(ui_control, BufferControl)
+
+    @property
+    def previous_control(self) -> UIControl:
+        """
+        Get the :class:`.UIControl` to previously had the focus.
+        """
+        try:
+            return self._stack[-2].content
+        except IndexError:
+            return self._stack[-1].content
+
+    def focus_last(self) -> None:
+        """
+        Give the focus to the last focused control.
+        """
+        if len(self._stack) > 1:
+            self._stack = self._stack[:-1]
+
+    def focus_next(self) -> None:
+        """
+        Focus the next visible/focusable Window.
+        """
+        windows = self.get_visible_focusable_windows()
+
+        if len(windows) > 0:
+            try:
+                index = windows.index(self.current_window)
+            except ValueError:
+                index = 0
+            else:
+                index = (index + 1) % len(windows)
+
+            self.focus(windows[index])
+
+    def focus_previous(self) -> None:
+        """
+        Focus the previous visible/focusable Window.
+        """
+        windows = self.get_visible_focusable_windows()
+
+        if len(windows) > 0:
+            try:
+                index = windows.index(self.current_window)
+            except ValueError:
+                index = 0
+            else:
+                index = (index - 1) % len(windows)
+
+            self.focus(windows[index])
+
+    def walk(self) -> Iterable[Container]:
+        """
+        Walk through all the layout nodes (and their children) and yield them.
+        """
+        yield from walk(self.container)
+
+    def walk_through_modal_area(self) -> Iterable[Container]:
+        """
+        Walk through all the containers which are in the current 'modal' part
+        of the layout.
+        """
+        # Go up in the tree, and find the root. (it will be a part of the
+        # layout, if the focus is in a modal part.)
+        root: Container = self.current_window
+        while not root.is_modal() and root in self._child_to_parent:
+            root = self._child_to_parent[root]
+
+        yield from walk(root)
+
+    def update_parents_relations(self) -> None:
+        """
+        Update child->parent relationships mapping.
+        """
+        parents = {}
+
+        def walk(e: Container) -> None:
+            for c in e.get_children():
+                parents[c] = e
+                walk(c)
+
+        walk(self.container)
+
+        self._child_to_parent = parents
+
+    def reset(self) -> None:
+        # Remove all search links when the UI starts.
+        # (Important, for instance when control-c is been pressed while
+        #  searching. The prompt cancels, but next `run()` call the search
+        #  links are still there.)
+        self.search_links.clear()
+
+        self.container.reset()
+
+    def get_parent(self, container: Container) -> Optional[Container]:
+        """
+        Return the parent container for the given container, or ``None``, if it
+        wasn't found.
+        """
+        try:
+            return self._child_to_parent[container]
+        except KeyError:
+            return None
+
+
+class InvalidLayoutError(Exception):
+    pass
+
+
+def walk(container: Container, skip_hidden: bool = False) -> Iterable[Container]:
+    """
+    Walk through layout, starting at this container.
+    """
+    # When `skip_hidden` is set, don't go into disabled ConditionalContainer containers.
+    if (
+        skip_hidden
+        and isinstance(container, ConditionalContainer)
+        and not container.filter()
+    ):
+        return
+
+    yield container
+
+    for c in container.get_children():
+        # yield from walk(c)
+        yield from walk(c, skip_hidden=skip_hidden)
diff --git a/src/prompt_toolkit/layout/margins.py b/src/prompt_toolkit/layout/margins.py
new file mode 100644
index 0000000..7c46819
--- /dev/null
+++ b/src/prompt_toolkit/layout/margins.py
@@ -0,0 +1,305 @@
+"""
+Margin implementations for a :class:`~prompt_toolkit.layout.containers.Window`.
+"""
+from abc import ABCMeta, abstractmethod
+from typing import TYPE_CHECKING, Callable, Optional
+
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.formatted_text import (
+    StyleAndTextTuples,
+    fragment_list_to_text,
+    to_formatted_text,
+)
+from prompt_toolkit.utils import get_cwidth
+
+from .controls import UIContent
+
+if TYPE_CHECKING:
+    from .containers import WindowRenderInfo
+
+__all__ = [
+    "Margin",
+    "NumberedMargin",
+    "ScrollbarMargin",
+    "ConditionalMargin",
+    "PromptMargin",
+]
+
+
+class Margin(metaclass=ABCMeta):
+    """
+    Base interface for a margin.
+    """
+
+    @abstractmethod
+    def get_width(self, get_ui_content: Callable[[], UIContent]) -> int:
+        """
+        Return the width that this margin is going to consume.
+
+        :param get_ui_content: Callable that asks the user control to create
+            a :class:`.UIContent` instance. This can be used for instance to
+            obtain the number of lines.
+        """
+        return 0
+
+    @abstractmethod
+    def create_margin(
+        self, window_render_info: "WindowRenderInfo", width: int, height: int
+    ) -> StyleAndTextTuples:
+        """
+        Creates a margin.
+        This should return a list of (style_str, text) tuples.
+
+        :param window_render_info:
+            :class:`~prompt_toolkit.layout.containers.WindowRenderInfo`
+            instance, generated after rendering and copying the visible part of
+            the :class:`~prompt_toolkit.layout.controls.UIControl` into the
+            :class:`~prompt_toolkit.layout.containers.Window`.
+        :param width: The width that's available for this margin. (As reported
+            by :meth:`.get_width`.)
+        :param height: The height that's available for this margin. (The height
+            of the :class:`~prompt_toolkit.layout.containers.Window`.)
+        """
+        return []
+
+
+class NumberedMargin(Margin):
+    """
+    Margin that displays the line numbers.
+
+    :param relative: Number relative to the cursor position. Similar to the Vi
+                     'relativenumber' option.
+    :param display_tildes: Display tildes after the end of the document, just
+        like Vi does.
+    """
+
+    def __init__(
+        self, relative: FilterOrBool = False, display_tildes: FilterOrBool = False
+    ) -> None:
+
+        self.relative = to_filter(relative)
+        self.display_tildes = to_filter(display_tildes)
+
+    def get_width(self, get_ui_content: Callable[[], UIContent]) -> int:
+        line_count = get_ui_content().line_count
+        return max(3, len("%s" % line_count) + 1)
+
+    def create_margin(
+        self, window_render_info: "WindowRenderInfo", width: int, height: int
+    ) -> StyleAndTextTuples:
+        relative = self.relative()
+
+        style = "class:line-number"
+        style_current = "class:line-number.current"
+
+        # Get current line number.
+        current_lineno = window_render_info.ui_content.cursor_position.y
+
+        # Construct margin.
+        result: StyleAndTextTuples = []
+        last_lineno = None
+
+        for y, lineno in enumerate(window_render_info.displayed_lines):
+            # Only display line number if this line is not a continuation of the previous line.
+            if lineno != last_lineno:
+                if lineno is None:
+                    pass
+                elif lineno == current_lineno:
+                    # Current line.
+                    if relative:
+                        # Left align current number in relative mode.
+                        result.append((style_current, "%i" % (lineno + 1)))
+                    else:
+                        result.append(
+                            (style_current, ("%i " % (lineno + 1)).rjust(width))
+                        )
+                else:
+                    # Other lines.
+                    if relative:
+                        lineno = abs(lineno - current_lineno) - 1
+
+                    result.append((style, ("%i " % (lineno + 1)).rjust(width)))
+
+            last_lineno = lineno
+            result.append(("", "\n"))
+
+        # Fill with tildes.
+        if self.display_tildes():
+            while y < window_render_info.window_height:
+                result.append(("class:tilde", "~\n"))
+                y += 1
+
+        return result
+
+
+class ConditionalMargin(Margin):
+    """
+    Wrapper around other :class:`.Margin` classes to show/hide them.
+    """
+
+    def __init__(self, margin: Margin, filter: FilterOrBool) -> None:
+        self.margin = margin
+        self.filter = to_filter(filter)
+
+    def get_width(self, get_ui_content: Callable[[], UIContent]) -> int:
+        if self.filter():
+            return self.margin.get_width(get_ui_content)
+        else:
+            return 0
+
+    def create_margin(
+        self, window_render_info: "WindowRenderInfo", width: int, height: int
+    ) -> StyleAndTextTuples:
+        if width and self.filter():
+            return self.margin.create_margin(window_render_info, width, height)
+        else:
+            return []
+
+
+class ScrollbarMargin(Margin):
+    """
+    Margin displaying a scrollbar.
+
+    :param display_arrows: Display scroll up/down arrows.
+    """
+
+    def __init__(
+        self,
+        display_arrows: FilterOrBool = False,
+        up_arrow_symbol: str = "^",
+        down_arrow_symbol: str = "v",
+    ) -> None:
+
+        self.display_arrows = to_filter(display_arrows)
+        self.up_arrow_symbol = up_arrow_symbol
+        self.down_arrow_symbol = down_arrow_symbol
+
+    def get_width(self, get_ui_content: Callable[[], UIContent]) -> int:
+        return 1
+
+    def create_margin(
+        self, window_render_info: "WindowRenderInfo", width: int, height: int
+    ) -> StyleAndTextTuples:
+        content_height = window_render_info.content_height
+        window_height = window_render_info.window_height
+        display_arrows = self.display_arrows()
+
+        if display_arrows:
+            window_height -= 2
+
+        try:
+            fraction_visible = len(window_render_info.displayed_lines) / float(
+                content_height
+            )
+            fraction_above = window_render_info.vertical_scroll / float(content_height)
+
+            scrollbar_height = int(
+                min(window_height, max(1, window_height * fraction_visible))
+            )
+            scrollbar_top = int(window_height * fraction_above)
+        except ZeroDivisionError:
+            return []
+        else:
+
+            def is_scroll_button(row: int) -> bool:
+                "True if we should display a button on this row."
+                return scrollbar_top <= row <= scrollbar_top + scrollbar_height
+
+            # Up arrow.
+            result: StyleAndTextTuples = []
+            if display_arrows:
+                result.extend(
+                    [
+                        ("class:scrollbar.arrow", self.up_arrow_symbol),
+                        ("class:scrollbar", "\n"),
+                    ]
+                )
+
+            # Scrollbar body.
+            scrollbar_background = "class:scrollbar.background"
+            scrollbar_background_start = "class:scrollbar.background,scrollbar.start"
+            scrollbar_button = "class:scrollbar.button"
+            scrollbar_button_end = "class:scrollbar.button,scrollbar.end"
+
+            for i in range(window_height):
+                if is_scroll_button(i):
+                    if not is_scroll_button(i + 1):
+                        # Give the last cell a different style, because we
+                        # want to underline this.
+                        result.append((scrollbar_button_end, " "))
+                    else:
+                        result.append((scrollbar_button, " "))
+                else:
+                    if is_scroll_button(i + 1):
+                        result.append((scrollbar_background_start, " "))
+                    else:
+                        result.append((scrollbar_background, " "))
+                result.append(("", "\n"))
+
+            # Down arrow
+            if display_arrows:
+                result.append(("class:scrollbar.arrow", self.down_arrow_symbol))
+
+            return result
+
+
+class PromptMargin(Margin):
+    """
+    [Deprecated]
+
+    Create margin that displays a prompt.
+    This can display one prompt at the first line, and a continuation prompt
+    (e.g, just dots) on all the following lines.
+
+    This `PromptMargin` implementation has been largely superseded in favor of
+    the `get_line_prefix` attribute of `Window`. The reason is that a margin is
+    always a fixed width, while `get_line_prefix` can return a variable width
+    prefix in front of every line, making it more powerful, especially for line
+    continuations.
+
+    :param get_prompt: Callable returns formatted text or a list of
+        `(style_str, type)` tuples to be shown as the prompt at the first line.
+    :param get_continuation: Callable that takes three inputs. The width (int),
+        line_number (int), and is_soft_wrap (bool). It should return formatted
+        text or a list of `(style_str, type)` tuples for the next lines of the
+        input.
+    """
+
+    def __init__(
+        self,
+        get_prompt: Callable[[], StyleAndTextTuples],
+        get_continuation: Optional[
+            Callable[[int, int, bool], StyleAndTextTuples]
+        ] = None,
+    ) -> None:
+
+        self.get_prompt = get_prompt
+        self.get_continuation = get_continuation
+
+    def get_width(self, get_ui_content: Callable[[], UIContent]) -> int:
+        "Width to report to the `Window`."
+        # Take the width from the first line.
+        text = fragment_list_to_text(self.get_prompt())
+        return get_cwidth(text)
+
+    def create_margin(
+        self, window_render_info: "WindowRenderInfo", width: int, height: int
+    ) -> StyleAndTextTuples:
+        get_continuation = self.get_continuation
+        result: StyleAndTextTuples = []
+
+        # First line.
+        result.extend(to_formatted_text(self.get_prompt()))
+
+        # Next lines.
+        if get_continuation:
+            last_y = None
+
+            for y in window_render_info.displayed_lines[1:]:
+                result.append(("", "\n"))
+                result.extend(
+                    to_formatted_text(get_continuation(width, y, y == last_y))
+                )
+                last_y = y
+
+        return result
diff --git a/src/prompt_toolkit/layout/menus.py b/src/prompt_toolkit/layout/menus.py
new file mode 100644
index 0000000..db0f9cb
--- /dev/null
+++ b/src/prompt_toolkit/layout/menus.py
@@ -0,0 +1,765 @@
+import math
+from itertools import zip_longest
+from typing import (
+    TYPE_CHECKING,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    TypeVar,
+    Union,
+    cast,
+)
+from weakref import WeakKeyDictionary, WeakValueDictionary
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.buffer import CompletionState
+from prompt_toolkit.completion import Completion
+from prompt_toolkit.data_structures import Point
+from prompt_toolkit.filters import (
+    Condition,
+    FilterOrBool,
+    has_completions,
+    is_done,
+    to_filter,
+)
+from prompt_toolkit.formatted_text import (
+    StyleAndTextTuples,
+    fragment_list_width,
+    to_formatted_text,
+)
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.layout.utils import explode_text_fragments
+from prompt_toolkit.mouse_events import MouseEvent, MouseEventType
+from prompt_toolkit.utils import get_cwidth
+
+from .containers import ConditionalContainer, HSplit, ScrollOffsets, Window
+from .controls import GetLinePrefixCallable, UIContent, UIControl
+from .dimension import Dimension
+from .margins import ScrollbarMargin
+
+if TYPE_CHECKING:
+    from prompt_toolkit.key_binding.key_bindings import (
+        KeyBindings,
+        NotImplementedOrNone,
+    )
+
+
+__all__ = [
+    "CompletionsMenu",
+    "MultiColumnCompletionsMenu",
+]
+
+E = KeyPressEvent
+
+
+class CompletionsMenuControl(UIControl):
+    """
+    Helper for drawing the complete menu to the screen.
+
+    :param scroll_offset: Number (integer) representing the preferred amount of
+        completions to be displayed before and after the current one. When this
+        is a very high number, the current completion will be shown in the
+        middle most of the time.
+    """
+
+    # Preferred minimum size of the menu control.
+    # The CompletionsMenu class defines a width of 8, and there is a scrollbar
+    # of 1.)
+    MIN_WIDTH = 7
+
+    def has_focus(self) -> bool:
+        return False
+
+    def preferred_width(self, max_available_width: int) -> Optional[int]:
+        complete_state = get_app().current_buffer.complete_state
+        if complete_state:
+            menu_width = self._get_menu_width(500, complete_state)
+            menu_meta_width = self._get_menu_meta_width(500, complete_state)
+
+            return menu_width + menu_meta_width
+        else:
+            return 0
+
+    def preferred_height(
+        self,
+        width: int,
+        max_available_height: int,
+        wrap_lines: bool,
+        get_line_prefix: Optional[GetLinePrefixCallable],
+    ) -> Optional[int]:
+
+        complete_state = get_app().current_buffer.complete_state
+        if complete_state:
+            return len(complete_state.completions)
+        else:
+            return 0
+
+    def create_content(self, width: int, height: int) -> UIContent:
+        """
+        Create a UIContent object for this control.
+        """
+        complete_state = get_app().current_buffer.complete_state
+        if complete_state:
+            completions = complete_state.completions
+            index = complete_state.complete_index  # Can be None!
+
+            # Calculate width of completions menu.
+            menu_width = self._get_menu_width(width, complete_state)
+            menu_meta_width = self._get_menu_meta_width(
+                width - menu_width, complete_state
+            )
+            show_meta = self._show_meta(complete_state)
+
+            def get_line(i: int) -> StyleAndTextTuples:
+                c = completions[i]
+                is_current_completion = i == index
+                result = _get_menu_item_fragments(
+                    c, is_current_completion, menu_width, space_after=True
+                )
+
+                if show_meta:
+                    result += self._get_menu_item_meta_fragments(
+                        c, is_current_completion, menu_meta_width
+                    )
+                return result
+
+            return UIContent(
+                get_line=get_line,
+                cursor_position=Point(x=0, y=index or 0),
+                line_count=len(completions),
+            )
+
+        return UIContent()
+
+    def _show_meta(self, complete_state: CompletionState) -> bool:
+        """
+        Return ``True`` if we need to show a column with meta information.
+        """
+        return any(c.display_meta_text for c in complete_state.completions)
+
+    def _get_menu_width(self, max_width: int, complete_state: CompletionState) -> int:
+        """
+        Return the width of the main column.
+        """
+        return min(
+            max_width,
+            max(
+                self.MIN_WIDTH,
+                max(get_cwidth(c.display_text) for c in complete_state.completions) + 2,
+            ),
+        )
+
+    def _get_menu_meta_width(
+        self, max_width: int, complete_state: CompletionState
+    ) -> int:
+        """
+        Return the width of the meta column.
+        """
+
+        def meta_width(completion: Completion) -> int:
+            return get_cwidth(completion.display_meta_text)
+
+        if self._show_meta(complete_state):
+            # If the amount of completions is over 200, compute the width based
+            # on the first 200 completions, otherwise this can be very slow.
+            completions = complete_state.completions
+            if len(completions) > 200:
+                completions = completions[:200]
+
+            return min(max_width, max(meta_width(c) for c in completions) + 2)
+        else:
+            return 0
+
+    def _get_menu_item_meta_fragments(
+        self, completion: Completion, is_current_completion: bool, width: int
+    ) -> StyleAndTextTuples:
+
+        if is_current_completion:
+            style_str = "class:completion-menu.meta.completion.current"
+        else:
+            style_str = "class:completion-menu.meta.completion"
+
+        text, tw = _trim_formatted_text(completion.display_meta, width - 2)
+        padding = " " * (width - 1 - tw)
+
+        return to_formatted_text(
+            cast(StyleAndTextTuples, []) + [("", " ")] + text + [("", padding)],
+            style=style_str,
+        )
+
+    def mouse_handler(self, mouse_event: MouseEvent) -> "NotImplementedOrNone":
+        """
+        Handle mouse events: clicking and scrolling.
+        """
+        b = get_app().current_buffer
+
+        if mouse_event.event_type == MouseEventType.MOUSE_UP:
+            # Select completion.
+            b.go_to_completion(mouse_event.position.y)
+            b.complete_state = None
+
+        elif mouse_event.event_type == MouseEventType.SCROLL_DOWN:
+            # Scroll up.
+            b.complete_next(count=3, disable_wrap_around=True)
+
+        elif mouse_event.event_type == MouseEventType.SCROLL_UP:
+            # Scroll down.
+            b.complete_previous(count=3, disable_wrap_around=True)
+
+        return None
+
+
+def _get_menu_item_fragments(
+    completion: Completion,
+    is_current_completion: bool,
+    width: int,
+    space_after: bool = False,
+) -> StyleAndTextTuples:
+    """
+    Get the style/text tuples for a menu item, styled and trimmed to the given
+    width.
+    """
+    if is_current_completion:
+        style_str = "class:completion-menu.completion.current {} {}".format(
+            completion.style,
+            completion.selected_style,
+        )
+    else:
+        style_str = "class:completion-menu.completion " + completion.style
+
+    text, tw = _trim_formatted_text(
+        completion.display, (width - 2 if space_after else width - 1)
+    )
+
+    padding = " " * (width - 1 - tw)
+
+    return to_formatted_text(
+        cast(StyleAndTextTuples, []) + [("", " ")] + text + [("", padding)],
+        style=style_str,
+    )
+
+
+def _trim_formatted_text(
+    formatted_text: StyleAndTextTuples, max_width: int
+) -> Tuple[StyleAndTextTuples, int]:
+    """
+    Trim the text to `max_width`, append dots when the text is too long.
+    Returns (text, width) tuple.
+    """
+    width = fragment_list_width(formatted_text)
+
+    # When the text is too wide, trim it.
+    if width > max_width:
+        result = []  # Text fragments.
+        remaining_width = max_width - 3
+
+        for style_and_ch in explode_text_fragments(formatted_text):
+            ch_width = get_cwidth(style_and_ch[1])
+
+            if ch_width <= remaining_width:
+                result.append(style_and_ch)
+                remaining_width -= ch_width
+            else:
+                break
+
+        result.append(("", "..."))
+
+        return result, max_width - remaining_width
+    else:
+        return formatted_text, width
+
+
+class CompletionsMenu(ConditionalContainer):
+    # NOTE: We use a pretty big z_index by default. Menus are supposed to be
+    #       above anything else. We also want to make sure that the content is
+    #       visible at the point where we draw this menu.
+    def __init__(
+        self,
+        max_height: Optional[int] = None,
+        scroll_offset: Union[int, Callable[[], int]] = 0,
+        extra_filter: FilterOrBool = True,
+        display_arrows: FilterOrBool = False,
+        z_index: int = 10**8,
+    ) -> None:
+
+        extra_filter = to_filter(extra_filter)
+        display_arrows = to_filter(display_arrows)
+
+        super().__init__(
+            content=Window(
+                content=CompletionsMenuControl(),
+                width=Dimension(min=8),
+                height=Dimension(min=1, max=max_height),
+                scroll_offsets=ScrollOffsets(top=scroll_offset, bottom=scroll_offset),
+                right_margins=[ScrollbarMargin(display_arrows=display_arrows)],
+                dont_extend_width=True,
+                style="class:completion-menu",
+                z_index=z_index,
+            ),
+            # Show when there are completions but not at the point we are
+            # returning the input.
+            filter=has_completions & ~is_done & extra_filter,
+        )
+
+
+class MultiColumnCompletionMenuControl(UIControl):
+    """
+    Completion menu that displays all the completions in several columns.
+    When there are more completions than space for them to be displayed, an
+    arrow is shown on the left or right side.
+
+    `min_rows` indicates how many rows will be available in any possible case.
+    When this is larger than one, it will try to use less columns and more
+    rows until this value is reached.
+    Be careful passing in a too big value, if less than the given amount of
+    rows are available, more columns would have been required, but
+    `preferred_width` doesn't know about that and reports a too small value.
+    This results in less completions displayed and additional scrolling.
+    (It's a limitation of how the layout engine currently works: first the
+    widths are calculated, then the heights.)
+
+    :param suggested_max_column_width: The suggested max width of a column.
+        The column can still be bigger than this, but if there is place for two
+        columns of this width, we will display two columns. This to avoid that
+        if there is one very wide completion, that it doesn't significantly
+        reduce the amount of columns.
+    """
+
+    _required_margin = 3  # One extra padding on the right + space for arrows.
+
+    def __init__(self, min_rows: int = 3, suggested_max_column_width: int = 30) -> None:
+        assert min_rows >= 1
+
+        self.min_rows = min_rows
+        self.suggested_max_column_width = suggested_max_column_width
+        self.scroll = 0
+
+        # Cache for column width computations. This computation is not cheap,
+        # so we don't want to do it over and over again while the user
+        # navigates through the completions.
+        # (map `completion_state` to `(completion_count, width)`. We remember
+        # the count, because a completer can add new completions to the
+        # `CompletionState` while loading.)
+        self._column_width_for_completion_state: "WeakKeyDictionary[CompletionState, Tuple[int, int]]" = (
+            WeakKeyDictionary()
+        )
+
+        # Info of last rendering.
+        self._rendered_rows = 0
+        self._rendered_columns = 0
+        self._total_columns = 0
+        self._render_pos_to_completion: Dict[Tuple[int, int], Completion] = {}
+        self._render_left_arrow = False
+        self._render_right_arrow = False
+        self._render_width = 0
+
+    def reset(self) -> None:
+        self.scroll = 0
+
+    def has_focus(self) -> bool:
+        return False
+
+    def preferred_width(self, max_available_width: int) -> Optional[int]:
+        """
+        Preferred width: prefer to use at least min_rows, but otherwise as much
+        as possible horizontally.
+        """
+        complete_state = get_app().current_buffer.complete_state
+        if complete_state is None:
+            return 0
+
+        column_width = self._get_column_width(complete_state)
+        result = int(
+            column_width
+            * math.ceil(len(complete_state.completions) / float(self.min_rows))
+        )
+
+        # When the desired width is still more than the maximum available,
+        # reduce by removing columns until we are less than the available
+        # width.
+        while (
+            result > column_width
+            and result > max_available_width - self._required_margin
+        ):
+            result -= column_width
+        return result + self._required_margin
+
+    def preferred_height(
+        self,
+        width: int,
+        max_available_height: int,
+        wrap_lines: bool,
+        get_line_prefix: Optional[GetLinePrefixCallable],
+    ) -> Optional[int]:
+        """
+        Preferred height: as much as needed in order to display all the completions.
+        """
+        complete_state = get_app().current_buffer.complete_state
+        if complete_state is None:
+            return 0
+
+        column_width = self._get_column_width(complete_state)
+        column_count = max(1, (width - self._required_margin) // column_width)
+
+        return int(math.ceil(len(complete_state.completions) / float(column_count)))
+
+    def create_content(self, width: int, height: int) -> UIContent:
+        """
+        Create a UIContent object for this menu.
+        """
+        complete_state = get_app().current_buffer.complete_state
+        if complete_state is None:
+            return UIContent()
+
+        column_width = self._get_column_width(complete_state)
+        self._render_pos_to_completion = {}
+
+        _T = TypeVar("_T")
+
+        def grouper(
+            n: int, iterable: Iterable[_T], fillvalue: Optional[_T] = None
+        ) -> Iterable[Sequence[Optional[_T]]]:
+            "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
+            args = [iter(iterable)] * n
+            return zip_longest(fillvalue=fillvalue, *args)
+
+        def is_current_completion(completion: Completion) -> bool:
+            "Returns True when this completion is the currently selected one."
+            return (
+                complete_state is not None
+                and complete_state.complete_index is not None
+                and c == complete_state.current_completion
+            )
+
+        # Space required outside of the regular columns, for displaying the
+        # left and right arrow.
+        HORIZONTAL_MARGIN_REQUIRED = 3
+
+        # There should be at least one column, but it cannot be wider than
+        # the available width.
+        column_width = min(width - HORIZONTAL_MARGIN_REQUIRED, column_width)
+
+        # However, when the columns tend to be very wide, because there are
+        # some very wide entries, shrink it anyway.
+        if column_width > self.suggested_max_column_width:
+            # `column_width` can still be bigger that `suggested_max_column_width`,
+            # but if there is place for two columns, we divide by two.
+            column_width //= column_width // self.suggested_max_column_width
+
+        visible_columns = max(1, (width - self._required_margin) // column_width)
+
+        columns_ = list(grouper(height, complete_state.completions))
+        rows_ = list(zip(*columns_))
+
+        # Make sure the current completion is always visible: update scroll offset.
+        selected_column = (complete_state.complete_index or 0) // height
+        self.scroll = min(
+            selected_column, max(self.scroll, selected_column - visible_columns + 1)
+        )
+
+        render_left_arrow = self.scroll > 0
+        render_right_arrow = self.scroll < len(rows_[0]) - visible_columns
+
+        # Write completions to screen.
+        fragments_for_line = []
+
+        for row_index, row in enumerate(rows_):
+            fragments: StyleAndTextTuples = []
+            middle_row = row_index == len(rows_) // 2
+
+            # Draw left arrow if we have hidden completions on the left.
+            if render_left_arrow:
+                fragments.append(("class:scrollbar", "<" if middle_row else " "))
+            elif render_right_arrow:
+                # Reserve one column empty space. (If there is a right
+                # arrow right now, there can be a left arrow as well.)
+                fragments.append(("", " "))
+
+            # Draw row content.
+            for column_index, c in enumerate(row[self.scroll :][:visible_columns]):
+                if c is not None:
+                    fragments += _get_menu_item_fragments(
+                        c, is_current_completion(c), column_width, space_after=False
+                    )
+
+                    # Remember render position for mouse click handler.
+                    for x in range(column_width):
+                        self._render_pos_to_completion[
+                            (column_index * column_width + x, row_index)
+                        ] = c
+                else:
+                    fragments.append(("class:completion", " " * column_width))
+
+            # Draw trailing padding for this row.
+            # (_get_menu_item_fragments only returns padding on the left.)
+            if render_left_arrow or render_right_arrow:
+                fragments.append(("class:completion", " "))
+
+            # Draw right arrow if we have hidden completions on the right.
+            if render_right_arrow:
+                fragments.append(("class:scrollbar", ">" if middle_row else " "))
+            elif render_left_arrow:
+                fragments.append(("class:completion", " "))
+
+            # Add line.
+            fragments_for_line.append(
+                to_formatted_text(fragments, style="class:completion-menu")
+            )
+
+        self._rendered_rows = height
+        self._rendered_columns = visible_columns
+        self._total_columns = len(columns_)
+        self._render_left_arrow = render_left_arrow
+        self._render_right_arrow = render_right_arrow
+        self._render_width = (
+            column_width * visible_columns + render_left_arrow + render_right_arrow + 1
+        )
+
+        def get_line(i: int) -> StyleAndTextTuples:
+            return fragments_for_line[i]
+
+        return UIContent(get_line=get_line, line_count=len(rows_))
+
+    def _get_column_width(self, completion_state: CompletionState) -> int:
+        """
+        Return the width of each column.
+        """
+        try:
+            count, width = self._column_width_for_completion_state[completion_state]
+            if count != len(completion_state.completions):
+                # Number of completions changed, recompute.
+                raise KeyError
+            return width
+        except KeyError:
+            result = (
+                max(get_cwidth(c.display_text) for c in completion_state.completions)
+                + 1
+            )
+            self._column_width_for_completion_state[completion_state] = (
+                len(completion_state.completions),
+                result,
+            )
+            return result
+
+    def mouse_handler(self, mouse_event: MouseEvent) -> "NotImplementedOrNone":
+        """
+        Handle scroll and click events.
+        """
+        b = get_app().current_buffer
+
+        def scroll_left() -> None:
+            b.complete_previous(count=self._rendered_rows, disable_wrap_around=True)
+            self.scroll = max(0, self.scroll - 1)
+
+        def scroll_right() -> None:
+            b.complete_next(count=self._rendered_rows, disable_wrap_around=True)
+            self.scroll = min(
+                self._total_columns - self._rendered_columns, self.scroll + 1
+            )
+
+        if mouse_event.event_type == MouseEventType.SCROLL_DOWN:
+            scroll_right()
+
+        elif mouse_event.event_type == MouseEventType.SCROLL_UP:
+            scroll_left()
+
+        elif mouse_event.event_type == MouseEventType.MOUSE_UP:
+            x = mouse_event.position.x
+            y = mouse_event.position.y
+
+            # Mouse click on left arrow.
+            if x == 0:
+                if self._render_left_arrow:
+                    scroll_left()
+
+            # Mouse click on right arrow.
+            elif x == self._render_width - 1:
+                if self._render_right_arrow:
+                    scroll_right()
+
+            # Mouse click on completion.
+            else:
+                completion = self._render_pos_to_completion.get((x, y))
+                if completion:
+                    b.apply_completion(completion)
+
+        return None
+
+    def get_key_bindings(self) -> "KeyBindings":
+        """
+        Expose key bindings that handle the left/right arrow keys when the menu
+        is displayed.
+        """
+        from prompt_toolkit.key_binding.key_bindings import KeyBindings
+
+        kb = KeyBindings()
+
+        @Condition
+        def filter() -> bool:
+            "Only handle key bindings if this menu is visible."
+            app = get_app()
+            complete_state = app.current_buffer.complete_state
+
+            # There need to be completions, and one needs to be selected.
+            if complete_state is None or complete_state.complete_index is None:
+                return False
+
+            # This menu needs to be visible.
+            return any(window.content == self for window in app.layout.visible_windows)
+
+        def move(right: bool = False) -> None:
+            buff = get_app().current_buffer
+            complete_state = buff.complete_state
+
+            if complete_state is not None and complete_state.complete_index is not None:
+                # Calculate new complete index.
+                new_index = complete_state.complete_index
+                if right:
+                    new_index += self._rendered_rows
+                else:
+                    new_index -= self._rendered_rows
+
+                if 0 <= new_index < len(complete_state.completions):
+                    buff.go_to_completion(new_index)
+
+        # NOTE: the is_global is required because the completion menu will
+        #       never be focussed.
+
+        @kb.add("left", is_global=True, filter=filter)
+        def _left(event: E) -> None:
+            move()
+
+        @kb.add("right", is_global=True, filter=filter)
+        def _right(event: E) -> None:
+            move(True)
+
+        return kb
+
+
+class MultiColumnCompletionsMenu(HSplit):
+    """
+    Container that displays the completions in several columns.
+    When `show_meta` (a :class:`~prompt_toolkit.filters.Filter`) evaluates
+    to True, it shows the meta information at the bottom.
+    """
+
+    def __init__(
+        self,
+        min_rows: int = 3,
+        suggested_max_column_width: int = 30,
+        show_meta: FilterOrBool = True,
+        extra_filter: FilterOrBool = True,
+        z_index: int = 10**8,
+    ) -> None:
+
+        show_meta = to_filter(show_meta)
+        extra_filter = to_filter(extra_filter)
+
+        # Display filter: show when there are completions but not at the point
+        # we are returning the input.
+        full_filter = has_completions & ~is_done & extra_filter
+
+        @Condition
+        def any_completion_has_meta() -> bool:
+            complete_state = get_app().current_buffer.complete_state
+            return complete_state is not None and any(
+                c.display_meta for c in complete_state.completions
+            )
+
+        # Create child windows.
+        # NOTE: We don't set style='class:completion-menu' to the
+        #       `MultiColumnCompletionMenuControl`, because this is used in a
+        #       Float that is made transparent, and the size of the control
+        #       doesn't always correspond exactly with the size of the
+        #       generated content.
+        completions_window = ConditionalContainer(
+            content=Window(
+                content=MultiColumnCompletionMenuControl(
+                    min_rows=min_rows,
+                    suggested_max_column_width=suggested_max_column_width,
+                ),
+                width=Dimension(min=8),
+                height=Dimension(min=1),
+            ),
+            filter=full_filter,
+        )
+
+        meta_window = ConditionalContainer(
+            content=Window(content=_SelectedCompletionMetaControl()),
+            filter=show_meta & full_filter & any_completion_has_meta,
+        )
+
+        # Initialise split.
+        super().__init__([completions_window, meta_window], z_index=z_index)
+
+
+class _SelectedCompletionMetaControl(UIControl):
+    """
+    Control that shows the meta information of the selected completion.
+    """
+
+    def preferred_width(self, max_available_width: int) -> Optional[int]:
+        """
+        Report the width of the longest meta text as the preferred width of this control.
+
+        It could be that we use less width, but this way, we're sure that the
+        layout doesn't change when we select another completion (E.g. that
+        completions are suddenly shown in more or fewer columns.)
+        """
+        app = get_app()
+        if app.current_buffer.complete_state:
+            state = app.current_buffer.complete_state
+
+            if len(state.completions) >= 30:
+                # When there are many completions, calling `get_cwidth` for
+                # every `display_meta_text` is too expensive. In this case,
+                # just return the max available width. There will be enough
+                # columns anyway so that the whole screen is filled with
+                # completions and `create_content` will then take up as much
+                # space as needed.
+                return max_available_width
+
+            return 2 + max(
+                get_cwidth(c.display_meta_text) for c in state.completions[:100]
+            )
+        else:
+            return 0
+
+    def preferred_height(
+        self,
+        width: int,
+        max_available_height: int,
+        wrap_lines: bool,
+        get_line_prefix: Optional[GetLinePrefixCallable],
+    ) -> Optional[int]:
+        return 1
+
+    def create_content(self, width: int, height: int) -> UIContent:
+        fragments = self._get_text_fragments()
+
+        def get_line(i: int) -> StyleAndTextTuples:
+            return fragments
+
+        return UIContent(get_line=get_line, line_count=1 if fragments else 0)
+
+    def _get_text_fragments(self) -> StyleAndTextTuples:
+        style = "class:completion-menu.multi-column-meta"
+        state = get_app().current_buffer.complete_state
+
+        if (
+            state
+            and state.current_completion
+            and state.current_completion.display_meta_text
+        ):
+            return to_formatted_text(
+                cast(StyleAndTextTuples, [("", " ")])
+                + state.current_completion.display_meta
+                + [("", " ")],
+                style=style,
+            )
+
+        return []
diff --git a/src/prompt_toolkit/layout/mouse_handlers.py b/src/prompt_toolkit/layout/mouse_handlers.py
new file mode 100644
index 0000000..2562317
--- /dev/null
+++ b/src/prompt_toolkit/layout/mouse_handlers.py
@@ -0,0 +1,54 @@
+from collections import defaultdict
+from typing import TYPE_CHECKING, Callable, DefaultDict
+
+from prompt_toolkit.mouse_events import MouseEvent
+
+if TYPE_CHECKING:
+    from prompt_toolkit.key_binding.key_bindings import NotImplementedOrNone
+
+__all__ = [
+    "MouseHandler",
+    "MouseHandlers",
+]
+
+
+MouseHandler = Callable[[MouseEvent], "NotImplementedOrNone"]
+
+
+class MouseHandlers:
+    """
+    Two dimensional raster of callbacks for mouse events.
+    """
+
+    def __init__(self) -> None:
+        def dummy_callback(mouse_event: MouseEvent) -> "NotImplementedOrNone":
+            """
+            :param mouse_event: `MouseEvent` instance.
+            """
+            return NotImplemented
+
+        # NOTE: Previously, the data structure was a dictionary mapping (x,y)
+        # to the handlers. This however would be more inefficient when copying
+        # over the mouse handlers of the visible region in the scrollable pane.
+
+        # Map y (row) to x (column) to handlers.
+        self.mouse_handlers: DefaultDict[
+            int, DefaultDict[int, MouseHandler]
+        ] = defaultdict(lambda: defaultdict(lambda: dummy_callback))
+
+    def set_mouse_handler_for_range(
+        self,
+        x_min: int,
+        x_max: int,
+        y_min: int,
+        y_max: int,
+        handler: Callable[[MouseEvent], "NotImplementedOrNone"],
+    ) -> None:
+        """
+        Set mouse handler for a region.
+        """
+        for y in range(y_min, y_max):
+            row = self.mouse_handlers[y]
+
+            for x in range(x_min, x_max):
+                row[x] = handler
diff --git a/src/prompt_toolkit/layout/processors.py b/src/prompt_toolkit/layout/processors.py
new file mode 100644
index 0000000..722658a
--- /dev/null
+++ b/src/prompt_toolkit/layout/processors.py
@@ -0,0 +1,1029 @@
+"""
+Processors are little transformation blocks that transform the fragments list
+from a buffer before the BufferControl will render it to the screen.
+
+They can insert fragments before or after, or highlight fragments by replacing the
+fragment types.
+"""
+import re
+from abc import ABCMeta, abstractmethod
+from typing import (
+    TYPE_CHECKING,
+    Callable,
+    Hashable,
+    List,
+    Optional,
+    Tuple,
+    Type,
+    Union,
+    cast,
+)
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.cache import SimpleCache
+from prompt_toolkit.document import Document
+from prompt_toolkit.filters import FilterOrBool, to_filter, vi_insert_multiple_mode
+from prompt_toolkit.formatted_text import (
+    AnyFormattedText,
+    StyleAndTextTuples,
+    to_formatted_text,
+)
+from prompt_toolkit.formatted_text.utils import fragment_list_len, fragment_list_to_text
+from prompt_toolkit.search import SearchDirection
+from prompt_toolkit.utils import to_int, to_str
+
+from .utils import explode_text_fragments
+
+if TYPE_CHECKING:
+    from .controls import BufferControl, UIContent
+
+__all__ = [
+    "Processor",
+    "TransformationInput",
+    "Transformation",
+    "DummyProcessor",
+    "HighlightSearchProcessor",
+    "HighlightIncrementalSearchProcessor",
+    "HighlightSelectionProcessor",
+    "PasswordProcessor",
+    "HighlightMatchingBracketProcessor",
+    "DisplayMultipleCursors",
+    "BeforeInput",
+    "ShowArg",
+    "AfterInput",
+    "AppendAutoSuggestion",
+    "ConditionalProcessor",
+    "ShowLeadingWhiteSpaceProcessor",
+    "ShowTrailingWhiteSpaceProcessor",
+    "TabsProcessor",
+    "ReverseSearchProcessor",
+    "DynamicProcessor",
+    "merge_processors",
+]
+
+
+class Processor(metaclass=ABCMeta):
+    """
+    Manipulate the fragments for a given line in a
+    :class:`~prompt_toolkit.layout.controls.BufferControl`.
+    """
+
+    @abstractmethod
+    def apply_transformation(
+        self, transformation_input: "TransformationInput"
+    ) -> "Transformation":
+        """
+        Apply transformation. Returns a :class:`.Transformation` instance.
+
+        :param transformation_input: :class:`.TransformationInput` object.
+        """
+        return Transformation(transformation_input.fragments)
+
+
+SourceToDisplay = Callable[[int], int]
+DisplayToSource = Callable[[int], int]
+
+
+class TransformationInput:
+    """
+    :param buffer_control: :class:`.BufferControl` instance.
+    :param lineno: The number of the line to which we apply the processor.
+    :param source_to_display: A function that returns the position in the
+        `fragments` for any position in the source string. (This takes
+        previous processors into account.)
+    :param fragments: List of fragments that we can transform. (Received from the
+        previous processor.)
+    """
+
+    def __init__(
+        self,
+        buffer_control: "BufferControl",
+        document: Document,
+        lineno: int,
+        source_to_display: SourceToDisplay,
+        fragments: StyleAndTextTuples,
+        width: int,
+        height: int,
+    ) -> None:
+
+        self.buffer_control = buffer_control
+        self.document = document
+        self.lineno = lineno
+        self.source_to_display = source_to_display
+        self.fragments = fragments
+        self.width = width
+        self.height = height
+
+    def unpack(
+        self,
+    ) -> Tuple[
+        "BufferControl", Document, int, SourceToDisplay, StyleAndTextTuples, int, int
+    ]:
+        return (
+            self.buffer_control,
+            self.document,
+            self.lineno,
+            self.source_to_display,
+            self.fragments,
+            self.width,
+            self.height,
+        )
+
+
+class Transformation:
+    """
+    Transformation result, as returned by :meth:`.Processor.apply_transformation`.
+
+    Important: Always make sure that the length of `document.text` is equal to
+               the length of all the text in `fragments`!
+
+    :param fragments: The transformed fragments. To be displayed, or to pass to
+        the next processor.
+    :param source_to_display: Cursor position transformation from original
+        string to transformed string.
+    :param display_to_source: Cursor position transformed from source string to
+        original string.
+    """
+
+    def __init__(
+        self,
+        fragments: StyleAndTextTuples,
+        source_to_display: Optional[SourceToDisplay] = None,
+        display_to_source: Optional[DisplayToSource] = None,
+    ) -> None:
+
+        self.fragments = fragments
+        self.source_to_display = source_to_display or (lambda i: i)
+        self.display_to_source = display_to_source or (lambda i: i)
+
+
+class DummyProcessor(Processor):
+    """
+    A `Processor` that doesn't do anything.
+    """
+
+    def apply_transformation(
+        self, transformation_input: TransformationInput
+    ) -> Transformation:
+        return Transformation(transformation_input.fragments)
+
+
+class HighlightSearchProcessor(Processor):
+    """
+    Processor that highlights search matches in the document.
+    Note that this doesn't support multiline search matches yet.
+
+    The style classes 'search' and 'search.current' will be applied to the
+    content.
+    """
+
+    _classname = "search"
+    _classname_current = "search.current"
+
+    def _get_search_text(self, buffer_control: "BufferControl") -> str:
+        """
+        The text we are searching for.
+        """
+        return buffer_control.search_state.text
+
+    def apply_transformation(
+        self, transformation_input: TransformationInput
+    ) -> Transformation:
+
+        (
+            buffer_control,
+            document,
+            lineno,
+            source_to_display,
+            fragments,
+            _,
+            _,
+        ) = transformation_input.unpack()
+
+        search_text = self._get_search_text(buffer_control)
+        searchmatch_fragment = f" class:{self._classname} "
+        searchmatch_current_fragment = f" class:{self._classname_current} "
+
+        if search_text and not get_app().is_done:
+            # For each search match, replace the style string.
+            line_text = fragment_list_to_text(fragments)
+            fragments = explode_text_fragments(fragments)
+
+            if buffer_control.search_state.ignore_case():
+                flags = re.IGNORECASE
+            else:
+                flags = re.RegexFlag(0)
+
+            # Get cursor column.
+            cursor_column: Optional[int]
+            if document.cursor_position_row == lineno:
+                cursor_column = source_to_display(document.cursor_position_col)
+            else:
+                cursor_column = None
+
+            for match in re.finditer(re.escape(search_text), line_text, flags=flags):
+                if cursor_column is not None:
+                    on_cursor = match.start() <= cursor_column < match.end()
+                else:
+                    on_cursor = False
+
+                for i in range(match.start(), match.end()):
+                    old_fragment, text, *_ = fragments[i]
+                    if on_cursor:
+                        fragments[i] = (
+                            old_fragment + searchmatch_current_fragment,
+                            fragments[i][1],
+                        )
+                    else:
+                        fragments[i] = (
+                            old_fragment + searchmatch_fragment,
+                            fragments[i][1],
+                        )
+
+        return Transformation(fragments)
+
+
+class HighlightIncrementalSearchProcessor(HighlightSearchProcessor):
+    """
+    Highlight the search terms that are used for highlighting the incremental
+    search. The style class 'incsearch' will be applied to the content.
+
+    Important: this requires the `preview_search=True` flag to be set for the
+    `BufferControl`. Otherwise, the cursor position won't be set to the search
+    match while searching, and nothing happens.
+    """
+
+    _classname = "incsearch"
+    _classname_current = "incsearch.current"
+
+    def _get_search_text(self, buffer_control: "BufferControl") -> str:
+        """
+        The text we are searching for.
+        """
+        # When the search buffer has focus, take that text.
+        search_buffer = buffer_control.search_buffer
+        if search_buffer is not None and search_buffer.text:
+            return search_buffer.text
+        return ""
+
+
+class HighlightSelectionProcessor(Processor):
+    """
+    Processor that highlights the selection in the document.
+    """
+
+    def apply_transformation(
+        self, transformation_input: TransformationInput
+    ) -> Transformation:
+        (
+            buffer_control,
+            document,
+            lineno,
+            source_to_display,
+            fragments,
+            _,
+            _,
+        ) = transformation_input.unpack()
+
+        selected_fragment = " class:selected "
+
+        # In case of selection, highlight all matches.
+        selection_at_line = document.selection_range_at_line(lineno)
+
+        if selection_at_line:
+            from_, to = selection_at_line
+            from_ = source_to_display(from_)
+            to = source_to_display(to)
+
+            fragments = explode_text_fragments(fragments)
+
+            if from_ == 0 and to == 0 and len(fragments) == 0:
+                # When this is an empty line, insert a space in order to
+                # visualise the selection.
+                return Transformation([(selected_fragment, " ")])
+            else:
+                for i in range(from_, to):
+                    if i < len(fragments):
+                        old_fragment, old_text, *_ = fragments[i]
+                        fragments[i] = (old_fragment + selected_fragment, old_text)
+                    elif i == len(fragments):
+                        fragments.append((selected_fragment, " "))
+
+        return Transformation(fragments)
+
+
+class PasswordProcessor(Processor):
+    """
+    Processor that masks the input. (For passwords.)
+
+    :param char: (string) Character to be used. "*" by default.
+    """
+
+    def __init__(self, char: str = "*") -> None:
+        self.char = char
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        fragments: StyleAndTextTuples = cast(
+            StyleAndTextTuples,
+            [
+                (style, self.char * len(text), *handler)
+                for style, text, *handler in ti.fragments
+            ],
+        )
+
+        return Transformation(fragments)
+
+
+class HighlightMatchingBracketProcessor(Processor):
+    """
+    When the cursor is on or right after a bracket, it highlights the matching
+    bracket.
+
+    :param max_cursor_distance: Only highlight matching brackets when the
+        cursor is within this distance. (From inside a `Processor`, we can't
+        know which lines will be visible on the screen. But we also don't want
+        to scan the whole document for matching brackets on each key press, so
+        we limit to this value.)
+    """
+
+    _closing_braces = "])}>"
+
+    def __init__(
+        self, chars: str = "[](){}<>", max_cursor_distance: int = 1000
+    ) -> None:
+        self.chars = chars
+        self.max_cursor_distance = max_cursor_distance
+
+        self._positions_cache: SimpleCache[
+            Hashable, List[Tuple[int, int]]
+        ] = SimpleCache(maxsize=8)
+
+    def _get_positions_to_highlight(self, document: Document) -> List[Tuple[int, int]]:
+        """
+        Return a list of (row, col) tuples that need to be highlighted.
+        """
+        pos: Optional[int]
+
+        # Try for the character under the cursor.
+        if document.current_char and document.current_char in self.chars:
+            pos = document.find_matching_bracket_position(
+                start_pos=document.cursor_position - self.max_cursor_distance,
+                end_pos=document.cursor_position + self.max_cursor_distance,
+            )
+
+        # Try for the character before the cursor.
+        elif (
+            document.char_before_cursor
+            and document.char_before_cursor in self._closing_braces
+            and document.char_before_cursor in self.chars
+        ):
+            document = Document(document.text, document.cursor_position - 1)
+
+            pos = document.find_matching_bracket_position(
+                start_pos=document.cursor_position - self.max_cursor_distance,
+                end_pos=document.cursor_position + self.max_cursor_distance,
+            )
+        else:
+            pos = None
+
+        # Return a list of (row, col) tuples that need to be highlighted.
+        if pos:
+            pos += document.cursor_position  # pos is relative.
+            row, col = document.translate_index_to_position(pos)
+            return [
+                (row, col),
+                (document.cursor_position_row, document.cursor_position_col),
+            ]
+        else:
+            return []
+
+    def apply_transformation(
+        self, transformation_input: TransformationInput
+    ) -> Transformation:
+
+        (
+            buffer_control,
+            document,
+            lineno,
+            source_to_display,
+            fragments,
+            _,
+            _,
+        ) = transformation_input.unpack()
+
+        # When the application is in the 'done' state, don't highlight.
+        if get_app().is_done:
+            return Transformation(fragments)
+
+        # Get the highlight positions.
+        key = (get_app().render_counter, document.text, document.cursor_position)
+        positions = self._positions_cache.get(
+            key, lambda: self._get_positions_to_highlight(document)
+        )
+
+        # Apply if positions were found at this line.
+        if positions:
+            for row, col in positions:
+                if row == lineno:
+                    col = source_to_display(col)
+                    fragments = explode_text_fragments(fragments)
+                    style, text, *_ = fragments[col]
+
+                    if col == document.cursor_position_col:
+                        style += " class:matching-bracket.cursor "
+                    else:
+                        style += " class:matching-bracket.other "
+
+                    fragments[col] = (style, text)
+
+        return Transformation(fragments)
+
+
+class DisplayMultipleCursors(Processor):
+    """
+    When we're in Vi block insert mode, display all the cursors.
+    """
+
+    def apply_transformation(
+        self, transformation_input: TransformationInput
+    ) -> Transformation:
+
+        (
+            buffer_control,
+            document,
+            lineno,
+            source_to_display,
+            fragments,
+            _,
+            _,
+        ) = transformation_input.unpack()
+
+        buff = buffer_control.buffer
+
+        if vi_insert_multiple_mode():
+            cursor_positions = buff.multiple_cursor_positions
+            fragments = explode_text_fragments(fragments)
+
+            # If any cursor appears on the current line, highlight that.
+            start_pos = document.translate_row_col_to_index(lineno, 0)
+            end_pos = start_pos + len(document.lines[lineno])
+
+            fragment_suffix = " class:multiple-cursors"
+
+            for p in cursor_positions:
+                if start_pos <= p <= end_pos:
+                    column = source_to_display(p - start_pos)
+
+                    # Replace fragment.
+                    try:
+                        style, text, *_ = fragments[column]
+                    except IndexError:
+                        # Cursor needs to be displayed after the current text.
+                        fragments.append((fragment_suffix, " "))
+                    else:
+                        style += fragment_suffix
+                        fragments[column] = (style, text)
+
+            return Transformation(fragments)
+        else:
+            return Transformation(fragments)
+
+
+class BeforeInput(Processor):
+    """
+    Insert text before the input.
+
+    :param text: This can be either plain text or formatted text
+        (or a callable that returns any of those).
+    :param style: style to be applied to this prompt/prefix.
+    """
+
+    def __init__(self, text: AnyFormattedText, style: str = "") -> None:
+        self.text = text
+        self.style = style
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        source_to_display: Optional[SourceToDisplay]
+        display_to_source: Optional[DisplayToSource]
+
+        if ti.lineno == 0:
+            # Get fragments.
+            fragments_before = to_formatted_text(self.text, self.style)
+            fragments = fragments_before + ti.fragments
+
+            shift_position = fragment_list_len(fragments_before)
+            source_to_display = lambda i: i + shift_position
+            display_to_source = lambda i: i - shift_position
+        else:
+            fragments = ti.fragments
+            source_to_display = None
+            display_to_source = None
+
+        return Transformation(
+            fragments,
+            source_to_display=source_to_display,
+            display_to_source=display_to_source,
+        )
+
+    def __repr__(self) -> str:
+        return f"BeforeInput({self.text!r}, {self.style!r})"
+
+
+class ShowArg(BeforeInput):
+    """
+    Display the 'arg' in front of the input.
+
+    This was used by the `PromptSession`, but now it uses the
+    `Window.get_line_prefix` function instead.
+    """
+
+    def __init__(self) -> None:
+        super().__init__(self._get_text_fragments)
+
+    def _get_text_fragments(self) -> StyleAndTextTuples:
+        app = get_app()
+        if app.key_processor.arg is None:
+            return []
+        else:
+            arg = app.key_processor.arg
+
+            return [
+                ("class:prompt.arg", "(arg: "),
+                ("class:prompt.arg.text", str(arg)),
+                ("class:prompt.arg", ") "),
+            ]
+
+    def __repr__(self) -> str:
+        return "ShowArg()"
+
+
+class AfterInput(Processor):
+    """
+    Insert text after the input.
+
+    :param text: This can be either plain text or formatted text
+        (or a callable that returns any of those).
+    :param style: style to be applied to this prompt/prefix.
+    """
+
+    def __init__(self, text: AnyFormattedText, style: str = "") -> None:
+        self.text = text
+        self.style = style
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        # Insert fragments after the last line.
+        if ti.lineno == ti.document.line_count - 1:
+            # Get fragments.
+            fragments_after = to_formatted_text(self.text, self.style)
+            return Transformation(fragments=ti.fragments + fragments_after)
+        else:
+            return Transformation(fragments=ti.fragments)
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.text!r}, style={self.style!r})"
+
+
+class AppendAutoSuggestion(Processor):
+    """
+    Append the auto suggestion to the input.
+    (The user can then press the right arrow the insert the suggestion.)
+    """
+
+    def __init__(self, style: str = "class:auto-suggestion") -> None:
+        self.style = style
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        # Insert fragments after the last line.
+        if ti.lineno == ti.document.line_count - 1:
+            buffer = ti.buffer_control.buffer
+
+            if buffer.suggestion and ti.document.is_cursor_at_the_end:
+                suggestion = buffer.suggestion.text
+            else:
+                suggestion = ""
+
+            return Transformation(fragments=ti.fragments + [(self.style, suggestion)])
+        else:
+            return Transformation(fragments=ti.fragments)
+
+
+class ShowLeadingWhiteSpaceProcessor(Processor):
+    """
+    Make leading whitespace visible.
+
+    :param get_char: Callable that returns one character.
+    """
+
+    def __init__(
+        self,
+        get_char: Optional[Callable[[], str]] = None,
+        style: str = "class:leading-whitespace",
+    ) -> None:
+        def default_get_char() -> str:
+            if "\xb7".encode(get_app().output.encoding(), "replace") == b"?":
+                return "."
+            else:
+                return "\xb7"
+
+        self.style = style
+        self.get_char = get_char or default_get_char
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        fragments = ti.fragments
+
+        # Walk through all te fragments.
+        if fragments and fragment_list_to_text(fragments).startswith(" "):
+            t = (self.style, self.get_char())
+            fragments = explode_text_fragments(fragments)
+
+            for i in range(len(fragments)):
+                if fragments[i][1] == " ":
+                    fragments[i] = t
+                else:
+                    break
+
+        return Transformation(fragments)
+
+
+class ShowTrailingWhiteSpaceProcessor(Processor):
+    """
+    Make trailing whitespace visible.
+
+    :param get_char: Callable that returns one character.
+    """
+
+    def __init__(
+        self,
+        get_char: Optional[Callable[[], str]] = None,
+        style: str = "class:training-whitespace",
+    ) -> None:
+        def default_get_char() -> str:
+            if "\xb7".encode(get_app().output.encoding(), "replace") == b"?":
+                return "."
+            else:
+                return "\xb7"
+
+        self.style = style
+        self.get_char = get_char or default_get_char
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        fragments = ti.fragments
+
+        if fragments and fragments[-1][1].endswith(" "):
+            t = (self.style, self.get_char())
+            fragments = explode_text_fragments(fragments)
+
+            # Walk backwards through all te fragments and replace whitespace.
+            for i in range(len(fragments) - 1, -1, -1):
+                char = fragments[i][1]
+                if char == " ":
+                    fragments[i] = t
+                else:
+                    break
+
+        return Transformation(fragments)
+
+
+class TabsProcessor(Processor):
+    """
+    Render tabs as spaces (instead of ^I) or make them visible (for instance,
+    by replacing them with dots.)
+
+    :param tabstop: Horizontal space taken by a tab. (`int` or callable that
+        returns an `int`).
+    :param char1: Character or callable that returns a character (text of
+        length one). This one is used for the first space taken by the tab.
+    :param char2: Like `char1`, but for the rest of the space.
+    """
+
+    def __init__(
+        self,
+        tabstop: Union[int, Callable[[], int]] = 4,
+        char1: Union[str, Callable[[], str]] = "|",
+        char2: Union[str, Callable[[], str]] = "\u2508",
+        style: str = "class:tab",
+    ) -> None:
+
+        self.char1 = char1
+        self.char2 = char2
+        self.tabstop = tabstop
+        self.style = style
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        tabstop = to_int(self.tabstop)
+        style = self.style
+
+        # Create separator for tabs.
+        separator1 = to_str(self.char1)
+        separator2 = to_str(self.char2)
+
+        # Transform fragments.
+        fragments = explode_text_fragments(ti.fragments)
+
+        position_mappings = {}
+        result_fragments: StyleAndTextTuples = []
+        pos = 0
+
+        for i, fragment_and_text in enumerate(fragments):
+            position_mappings[i] = pos
+
+            if fragment_and_text[1] == "\t":
+                # Calculate how many characters we have to insert.
+                count = tabstop - (pos % tabstop)
+                if count == 0:
+                    count = tabstop
+
+                # Insert tab.
+                result_fragments.append((style, separator1))
+                result_fragments.append((style, separator2 * (count - 1)))
+                pos += count
+            else:
+                result_fragments.append(fragment_and_text)
+                pos += 1
+
+        position_mappings[len(fragments)] = pos
+        # Add `pos+1` to mapping, because the cursor can be right after the
+        # line as well.
+        position_mappings[len(fragments) + 1] = pos + 1
+
+        def source_to_display(from_position: int) -> int:
+            "Maps original cursor position to the new one."
+            return position_mappings[from_position]
+
+        def display_to_source(display_pos: int) -> int:
+            "Maps display cursor position to the original one."
+            position_mappings_reversed = {v: k for k, v in position_mappings.items()}
+
+            while display_pos >= 0:
+                try:
+                    return position_mappings_reversed[display_pos]
+                except KeyError:
+                    display_pos -= 1
+            return 0
+
+        return Transformation(
+            result_fragments,
+            source_to_display=source_to_display,
+            display_to_source=display_to_source,
+        )
+
+
+class ReverseSearchProcessor(Processor):
+    """
+    Process to display the "(reverse-i-search)`...`:..." stuff around
+    the search buffer.
+
+    Note: This processor is meant to be applied to the BufferControl that
+    contains the search buffer, it's not meant for the original input.
+    """
+
+    _excluded_input_processors: List[Type[Processor]] = [
+        HighlightSearchProcessor,
+        HighlightSelectionProcessor,
+        BeforeInput,
+        AfterInput,
+    ]
+
+    def _get_main_buffer(
+        self, buffer_control: "BufferControl"
+    ) -> Optional["BufferControl"]:
+        from prompt_toolkit.layout.controls import BufferControl
+
+        prev_control = get_app().layout.search_target_buffer_control
+        if (
+            isinstance(prev_control, BufferControl)
+            and prev_control.search_buffer_control == buffer_control
+        ):
+            return prev_control
+        return None
+
+    def _content(
+        self, main_control: "BufferControl", ti: TransformationInput
+    ) -> "UIContent":
+        from prompt_toolkit.layout.controls import BufferControl
+
+        # Emulate the BufferControl through which we are searching.
+        # For this we filter out some of the input processors.
+        excluded_processors = tuple(self._excluded_input_processors)
+
+        def filter_processor(item: Processor) -> Optional[Processor]:
+            """Filter processors from the main control that we want to disable
+            here. This returns either an accepted processor or None."""
+            # For a `_MergedProcessor`, check each individual processor, recursively.
+            if isinstance(item, _MergedProcessor):
+                accepted_processors = [filter_processor(p) for p in item.processors]
+                return merge_processors(
+                    [p for p in accepted_processors if p is not None]
+                )
+
+            # For a `ConditionalProcessor`, check the body.
+            elif isinstance(item, ConditionalProcessor):
+                p = filter_processor(item.processor)
+                if p:
+                    return ConditionalProcessor(p, item.filter)
+
+            # Otherwise, check the processor itself.
+            else:
+                if not isinstance(item, excluded_processors):
+                    return item
+
+            return None
+
+        filtered_processor = filter_processor(
+            merge_processors(main_control.input_processors or [])
+        )
+        highlight_processor = HighlightIncrementalSearchProcessor()
+
+        if filtered_processor:
+            new_processors = [filtered_processor, highlight_processor]
+        else:
+            new_processors = [highlight_processor]
+
+        from .controls import SearchBufferControl
+
+        assert isinstance(ti.buffer_control, SearchBufferControl)
+
+        buffer_control = BufferControl(
+            buffer=main_control.buffer,
+            input_processors=new_processors,
+            include_default_input_processors=False,
+            lexer=main_control.lexer,
+            preview_search=True,
+            search_buffer_control=ti.buffer_control,
+        )
+
+        return buffer_control.create_content(ti.width, ti.height, preview_search=True)
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        from .controls import SearchBufferControl
+
+        assert isinstance(
+            ti.buffer_control, SearchBufferControl
+        ), "`ReverseSearchProcessor` should be applied to a `SearchBufferControl` only."
+
+        source_to_display: Optional[SourceToDisplay]
+        display_to_source: Optional[DisplayToSource]
+
+        main_control = self._get_main_buffer(ti.buffer_control)
+
+        if ti.lineno == 0 and main_control:
+            content = self._content(main_control, ti)
+
+            # Get the line from the original document for this search.
+            line_fragments = content.get_line(content.cursor_position.y)
+
+            if main_control.search_state.direction == SearchDirection.FORWARD:
+                direction_text = "i-search"
+            else:
+                direction_text = "reverse-i-search"
+
+            fragments_before: StyleAndTextTuples = [
+                ("class:prompt.search", "("),
+                ("class:prompt.search", direction_text),
+                ("class:prompt.search", ")`"),
+            ]
+
+            fragments = (
+                fragments_before
+                + [
+                    ("class:prompt.search.text", fragment_list_to_text(ti.fragments)),
+                    ("", "': "),
+                ]
+                + line_fragments
+            )
+
+            shift_position = fragment_list_len(fragments_before)
+            source_to_display = lambda i: i + shift_position
+            display_to_source = lambda i: i - shift_position
+        else:
+            source_to_display = None
+            display_to_source = None
+            fragments = ti.fragments
+
+        return Transformation(
+            fragments,
+            source_to_display=source_to_display,
+            display_to_source=display_to_source,
+        )
+
+
+class ConditionalProcessor(Processor):
+    """
+    Processor that applies another processor, according to a certain condition.
+    Example::
+
+        # Create a function that returns whether or not the processor should
+        # currently be applied.
+        def highlight_enabled():
+            return true_or_false
+
+        # Wrapped it in a `ConditionalProcessor` for usage in a `BufferControl`.
+        BufferControl(input_processors=[
+            ConditionalProcessor(HighlightSearchProcessor(),
+                                 Condition(highlight_enabled))])
+
+    :param processor: :class:`.Processor` instance.
+    :param filter: :class:`~prompt_toolkit.filters.Filter` instance.
+    """
+
+    def __init__(self, processor: Processor, filter: FilterOrBool) -> None:
+        self.processor = processor
+        self.filter = to_filter(filter)
+
+    def apply_transformation(
+        self, transformation_input: TransformationInput
+    ) -> Transformation:
+        # Run processor when enabled.
+        if self.filter():
+            return self.processor.apply_transformation(transformation_input)
+        else:
+            return Transformation(transformation_input.fragments)
+
+    def __repr__(self) -> str:
+        return "{}(processor={!r}, filter={!r})".format(
+            self.__class__.__name__,
+            self.processor,
+            self.filter,
+        )
+
+
+class DynamicProcessor(Processor):
+    """
+    Processor class that dynamically returns any Processor.
+
+    :param get_processor: Callable that returns a :class:`.Processor` instance.
+    """
+
+    def __init__(self, get_processor: Callable[[], Optional[Processor]]) -> None:
+        self.get_processor = get_processor
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        processor = self.get_processor() or DummyProcessor()
+        return processor.apply_transformation(ti)
+
+
+def merge_processors(processors: List[Processor]) -> Processor:
+    """
+    Merge multiple `Processor` objects into one.
+    """
+    if len(processors) == 0:
+        return DummyProcessor()
+
+    if len(processors) == 1:
+        return processors[0]  # Nothing to merge.
+
+    return _MergedProcessor(processors)
+
+
+class _MergedProcessor(Processor):
+    """
+    Processor that groups multiple other `Processor` objects, but exposes an
+    API as if it is one `Processor`.
+    """
+
+    def __init__(self, processors: List[Processor]):
+        self.processors = processors
+
+    def apply_transformation(self, ti: TransformationInput) -> Transformation:
+        source_to_display_functions = [ti.source_to_display]
+        display_to_source_functions = []
+        fragments = ti.fragments
+
+        def source_to_display(i: int) -> int:
+            """Translate x position from the buffer to the x position in the
+            processor fragments list."""
+            for f in source_to_display_functions:
+                i = f(i)
+            return i
+
+        for p in self.processors:
+            transformation = p.apply_transformation(
+                TransformationInput(
+                    ti.buffer_control,
+                    ti.document,
+                    ti.lineno,
+                    source_to_display,
+                    fragments,
+                    ti.width,
+                    ti.height,
+                )
+            )
+            fragments = transformation.fragments
+            display_to_source_functions.append(transformation.display_to_source)
+            source_to_display_functions.append(transformation.source_to_display)
+
+        def display_to_source(i: int) -> int:
+            for f in reversed(display_to_source_functions):
+                i = f(i)
+            return i
+
+        # In the case of a nested _MergedProcessor, each processor wants to
+        # receive a 'source_to_display' function (as part of the
+        # TransformationInput) that has everything in the chain before
+        # included, because it can be called as part of the
+        # `apply_transformation` function. However, this first
+        # `source_to_display` should not be part of the output that we are
+        # returning. (This is the most consistent with `display_to_source`.)
+        del source_to_display_functions[:1]
+
+        return Transformation(fragments, source_to_display, display_to_source)
diff --git a/src/prompt_toolkit/layout/screen.py b/src/prompt_toolkit/layout/screen.py
new file mode 100644
index 0000000..2b58272
--- /dev/null
+++ b/src/prompt_toolkit/layout/screen.py
@@ -0,0 +1,328 @@
+from collections import defaultdict
+from typing import TYPE_CHECKING, Callable, DefaultDict, Dict, List, Optional, Tuple
+
+from prompt_toolkit.cache import FastDictCache
+from prompt_toolkit.data_structures import Point
+from prompt_toolkit.utils import get_cwidth
+
+if TYPE_CHECKING:
+    from .containers import Window
+
+
+__all__ = [
+    "Screen",
+    "Char",
+]
+
+
+class Char:
+    """
+    Represent a single character in a :class:`.Screen`.
+
+    This should be considered immutable.
+
+    :param char: A single character (can be a double-width character).
+    :param style: A style string. (Can contain classnames.)
+    """
+
+    __slots__ = ("char", "style", "width")
+
+    # If we end up having one of these special control sequences in the input string,
+    # we should display them as follows:
+    # Usually this happens after a "quoted insert".
+    display_mappings: Dict[str, str] = {
+        "\x00": "^@",  # Control space
+        "\x01": "^A",
+        "\x02": "^B",
+        "\x03": "^C",
+        "\x04": "^D",
+        "\x05": "^E",
+        "\x06": "^F",
+        "\x07": "^G",
+        "\x08": "^H",
+        "\x09": "^I",
+        "\x0a": "^J",
+        "\x0b": "^K",
+        "\x0c": "^L",
+        "\x0d": "^M",
+        "\x0e": "^N",
+        "\x0f": "^O",
+        "\x10": "^P",
+        "\x11": "^Q",
+        "\x12": "^R",
+        "\x13": "^S",
+        "\x14": "^T",
+        "\x15": "^U",
+        "\x16": "^V",
+        "\x17": "^W",
+        "\x18": "^X",
+        "\x19": "^Y",
+        "\x1a": "^Z",
+        "\x1b": "^[",  # Escape
+        "\x1c": "^\\",
+        "\x1d": "^]",
+        "\x1e": "^^",
+        "\x1f": "^_",
+        "\x7f": "^?",  # ASCII Delete (backspace).
+        # Special characters. All visualized like Vim does.
+        "\x80": "<80>",
+        "\x81": "<81>",
+        "\x82": "<82>",
+        "\x83": "<83>",
+        "\x84": "<84>",
+        "\x85": "<85>",
+        "\x86": "<86>",
+        "\x87": "<87>",
+        "\x88": "<88>",
+        "\x89": "<89>",
+        "\x8a": "<8a>",
+        "\x8b": "<8b>",
+        "\x8c": "<8c>",
+        "\x8d": "<8d>",
+        "\x8e": "<8e>",
+        "\x8f": "<8f>",
+        "\x90": "<90>",
+        "\x91": "<91>",
+        "\x92": "<92>",
+        "\x93": "<93>",
+        "\x94": "<94>",
+        "\x95": "<95>",
+        "\x96": "<96>",
+        "\x97": "<97>",
+        "\x98": "<98>",
+        "\x99": "<99>",
+        "\x9a": "<9a>",
+        "\x9b": "<9b>",
+        "\x9c": "<9c>",
+        "\x9d": "<9d>",
+        "\x9e": "<9e>",
+        "\x9f": "<9f>",
+        # For the non-breaking space: visualize like Emacs does by default.
+        # (Print a space, but attach the 'nbsp' class that applies the
+        # underline style.)
+        "\xa0": " ",
+    }
+
+    def __init__(self, char: str = " ", style: str = "") -> None:
+        # If this character has to be displayed otherwise, take that one.
+        if char in self.display_mappings:
+            if char == "\xa0":
+                style += " class:nbsp "  # Will be underlined.
+            else:
+                style += " class:control-character "
+
+            char = self.display_mappings[char]
+
+        self.char = char
+        self.style = style
+
+        # Calculate width. (We always need this, so better to store it directly
+        # as a member for performance.)
+        self.width = get_cwidth(char)
+
+    # In theory, `other` can be any type of object, but because of performance
+    # we don't want to do an `isinstance` check every time. We assume "other"
+    # is always a "Char".
+    def _equal(self, other: "Char") -> bool:
+        return self.char == other.char and self.style == other.style
+
+    def _not_equal(self, other: "Char") -> bool:
+        # Not equal: We don't do `not char.__eq__` here, because of the
+        # performance of calling yet another function.
+        return self.char != other.char or self.style != other.style
+
+    if not TYPE_CHECKING:
+        __eq__ = _equal
+        __ne__ = _not_equal
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.char!r}, {self.style!r})"
+
+
+_CHAR_CACHE: FastDictCache[Tuple[str, str], Char] = FastDictCache(
+    Char, size=1000 * 1000
+)
+Transparent = "[transparent]"
+
+
+class Screen:
+    """
+    Two dimensional buffer of :class:`.Char` instances.
+    """
+
+    def __init__(
+        self,
+        default_char: Optional[Char] = None,
+        initial_width: int = 0,
+        initial_height: int = 0,
+    ) -> None:
+
+        if default_char is None:
+            default_char2 = _CHAR_CACHE[" ", Transparent]
+        else:
+            default_char2 = default_char
+
+        self.data_buffer: DefaultDict[int, DefaultDict[int, Char]] = defaultdict(
+            lambda: defaultdict(lambda: default_char2)
+        )
+
+        #: Escape sequences to be injected.
+        self.zero_width_escapes: DefaultDict[int, DefaultDict[int, str]] = defaultdict(
+            lambda: defaultdict(lambda: "")
+        )
+
+        #: Position of the cursor.
+        self.cursor_positions: Dict[
+            "Window", Point
+        ] = {}  # Map `Window` objects to `Point` objects.
+
+        #: Visibility of the cursor.
+        self.show_cursor = True
+
+        #: (Optional) Where to position the menu. E.g. at the start of a completion.
+        #: (We can't use the cursor position, because we don't want the
+        #: completion menu to change its position when we browse through all the
+        #: completions.)
+        self.menu_positions: Dict[
+            "Window", Point
+        ] = {}  # Map `Window` objects to `Point` objects.
+
+        #: Currently used width/height of the screen. This will increase when
+        #: data is written to the screen.
+        self.width = initial_width or 0
+        self.height = initial_height or 0
+
+        # Windows that have been drawn. (Each `Window` class will add itself to
+        # this list.)
+        self.visible_windows_to_write_positions: Dict["Window", "WritePosition"] = {}
+
+        # List of (z_index, draw_func)
+        self._draw_float_functions: List[Tuple[int, Callable[[], None]]] = []
+
+    @property
+    def visible_windows(self) -> List["Window"]:
+        return list(self.visible_windows_to_write_positions.keys())
+
+    def set_cursor_position(self, window: "Window", position: Point) -> None:
+        """
+        Set the cursor position for a given window.
+        """
+        self.cursor_positions[window] = position
+
+    def set_menu_position(self, window: "Window", position: Point) -> None:
+        """
+        Set the cursor position for a given window.
+        """
+        self.menu_positions[window] = position
+
+    def get_cursor_position(self, window: "Window") -> Point:
+        """
+        Get the cursor position for a given window.
+        Returns a `Point`.
+        """
+        try:
+            return self.cursor_positions[window]
+        except KeyError:
+            return Point(x=0, y=0)
+
+    def get_menu_position(self, window: "Window") -> Point:
+        """
+        Get the menu position for a given window.
+        (This falls back to the cursor position if no menu position was set.)
+        """
+        try:
+            return self.menu_positions[window]
+        except KeyError:
+            try:
+                return self.cursor_positions[window]
+            except KeyError:
+                return Point(x=0, y=0)
+
+    def draw_with_z_index(self, z_index: int, draw_func: Callable[[], None]) -> None:
+        """
+        Add a draw-function for a `Window` which has a >= 0 z_index.
+        This will be postponed until `draw_all_floats` is called.
+        """
+        self._draw_float_functions.append((z_index, draw_func))
+
+    def draw_all_floats(self) -> None:
+        """
+        Draw all float functions in order of z-index.
+        """
+        # We keep looping because some draw functions could add new functions
+        # to this list. See `FloatContainer`.
+        while self._draw_float_functions:
+            # Sort the floats that we have so far by z_index.
+            functions = sorted(self._draw_float_functions, key=lambda item: item[0])
+
+            # Draw only one at a time, then sort everything again. Now floats
+            # might have been added.
+            self._draw_float_functions = functions[1:]
+            functions[0][1]()
+
+    def append_style_to_content(self, style_str: str) -> None:
+        """
+        For all the characters in the screen.
+        Set the style string to the given `style_str`.
+        """
+        b = self.data_buffer
+        char_cache = _CHAR_CACHE
+
+        append_style = " " + style_str
+
+        for y, row in b.items():
+            for x, char in row.items():
+                row[x] = char_cache[char.char, char.style + append_style]
+
+    def fill_area(
+        self, write_position: "WritePosition", style: str = "", after: bool = False
+    ) -> None:
+        """
+        Fill the content of this area, using the given `style`.
+        The style is prepended before whatever was here before.
+        """
+        if not style.strip():
+            return
+
+        xmin = write_position.xpos
+        xmax = write_position.xpos + write_position.width
+        char_cache = _CHAR_CACHE
+        data_buffer = self.data_buffer
+
+        if after:
+            append_style = " " + style
+            prepend_style = ""
+        else:
+            append_style = ""
+            prepend_style = style + " "
+
+        for y in range(
+            write_position.ypos, write_position.ypos + write_position.height
+        ):
+            row = data_buffer[y]
+            for x in range(xmin, xmax):
+                cell = row[x]
+                row[x] = char_cache[
+                    cell.char, prepend_style + cell.style + append_style
+                ]
+
+
+class WritePosition:
+    def __init__(self, xpos: int, ypos: int, width: int, height: int) -> None:
+        assert height >= 0
+        assert width >= 0
+        # xpos and ypos can be negative. (A float can be partially visible.)
+
+        self.xpos = xpos
+        self.ypos = ypos
+        self.width = width
+        self.height = height
+
+    def __repr__(self) -> str:
+        return "{}(x={!r}, y={!r}, width={!r}, height={!r})".format(
+            self.__class__.__name__,
+            self.xpos,
+            self.ypos,
+            self.width,
+            self.height,
+        )
diff --git a/src/prompt_toolkit/layout/scrollable_pane.py b/src/prompt_toolkit/layout/scrollable_pane.py
new file mode 100644
index 0000000..810e405
--- /dev/null
+++ b/src/prompt_toolkit/layout/scrollable_pane.py
@@ -0,0 +1,494 @@
+from typing import Dict, List, Optional
+
+from prompt_toolkit.data_structures import Point
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.key_binding import KeyBindingsBase
+from prompt_toolkit.mouse_events import MouseEvent
+
+from .containers import Container, ScrollOffsets
+from .dimension import AnyDimension, Dimension, sum_layout_dimensions, to_dimension
+from .mouse_handlers import MouseHandler, MouseHandlers
+from .screen import Char, Screen, WritePosition
+
+__all__ = ["ScrollablePane"]
+
+# Never go beyond this height, because performance will degrade.
+MAX_AVAILABLE_HEIGHT = 10_000
+
+
+class ScrollablePane(Container):
+    """
+    Container widget that exposes a larger virtual screen to its content and
+    displays it in a vertical scrollbale region.
+
+    Typically this is wrapped in a large `HSplit` container. Make sure in that
+    case to not specify a `height` dimension of the `HSplit`, so that it will
+    scale according to the content.
+
+    .. note::
+
+        If you want to display a completion menu for widgets in this
+        `ScrollablePane`, then it's still a good practice to use a
+        `FloatContainer` with a `CompletionsMenu` in a `Float` at the top-level
+        of the layout hierarchy, rather then nesting a `FloatContainer` in this
+        `ScrollablePane`. (Otherwise, it's possible that the completion menu
+        is clipped.)
+
+    :param content: The content container.
+    :param scrolloffset: Try to keep the cursor within this distance from the
+        top/bottom (left/right offset is not used).
+    :param keep_cursor_visible: When `True`, automatically scroll the pane so
+        that the cursor (of the focused window) is always visible.
+    :param keep_focused_window_visible: When `True`, automatically scroll th e
+        pane so that the focused window is visible, or as much visible as
+        possible if it doen't completely fit the screen.
+    :param max_available_height: Always constraint the height to this amount
+        for performance reasons.
+    :param width: When given, use this width instead of looking at the children.
+    :param height: When given, use this height instead of looking at the children.
+    :param show_scrollbar: When `True` display a scrollbar on the right.
+    """
+
+    def __init__(
+        self,
+        content: Container,
+        scroll_offsets: Optional[ScrollOffsets] = None,
+        keep_cursor_visible: FilterOrBool = True,
+        keep_focused_window_visible: FilterOrBool = True,
+        max_available_height: int = MAX_AVAILABLE_HEIGHT,
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        show_scrollbar: FilterOrBool = True,
+        display_arrows: FilterOrBool = True,
+        up_arrow_symbol: str = "^",
+        down_arrow_symbol: str = "v",
+    ) -> None:
+        self.content = content
+        self.scroll_offsets = scroll_offsets or ScrollOffsets(top=1, bottom=1)
+        self.keep_cursor_visible = to_filter(keep_cursor_visible)
+        self.keep_focused_window_visible = to_filter(keep_focused_window_visible)
+        self.max_available_height = max_available_height
+        self.width = width
+        self.height = height
+        self.show_scrollbar = to_filter(show_scrollbar)
+        self.display_arrows = to_filter(display_arrows)
+        self.up_arrow_symbol = up_arrow_symbol
+        self.down_arrow_symbol = down_arrow_symbol
+
+        self.vertical_scroll = 0
+
+    def __repr__(self) -> str:
+        return f"ScrollablePane({self.content!r})"
+
+    def reset(self) -> None:
+        self.content.reset()
+
+    def preferred_width(self, max_available_width: int) -> Dimension:
+        if self.width is not None:
+            return to_dimension(self.width)
+
+        # We're only scrolling vertical. So the preferred width is equal to
+        # that of the content.
+        content_width = self.content.preferred_width(max_available_width)
+
+        # If a scrollbar needs to be displayed, add +1 to the content width.
+        if self.show_scrollbar():
+            return sum_layout_dimensions([Dimension.exact(1), content_width])
+
+        return content_width
+
+    def preferred_height(self, width: int, max_available_height: int) -> Dimension:
+        if self.height is not None:
+            return to_dimension(self.height)
+
+        # Prefer a height large enough so that it fits all the content. If not,
+        # we'll make the pane scrollable.
+        if self.show_scrollbar():
+            # If `show_scrollbar` is set. Always reserve space for the scrollbar.
+            width -= 1
+
+        dimension = self.content.preferred_height(width, self.max_available_height)
+
+        # Only take 'preferred' into account. Min/max can be anything.
+        return Dimension(min=0, preferred=dimension.preferred)
+
+    def write_to_screen(
+        self,
+        screen: Screen,
+        mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        parent_style: str,
+        erase_bg: bool,
+        z_index: Optional[int],
+    ) -> None:
+        """
+        Render scrollable pane content.
+
+        This works by rendering on an off-screen canvas, and copying over the
+        visible region.
+        """
+        show_scrollbar = self.show_scrollbar()
+
+        if show_scrollbar:
+            virtual_width = write_position.width - 1
+        else:
+            virtual_width = write_position.width
+
+        # Compute preferred height again.
+        virtual_height = self.content.preferred_height(
+            virtual_width, self.max_available_height
+        ).preferred
+
+        # Ensure virtual height is at least the available height.
+        virtual_height = max(virtual_height, write_position.height)
+        virtual_height = min(virtual_height, self.max_available_height)
+
+        # First, write the content to a virtual screen, then copy over the
+        # visible part to the real screen.
+        temp_screen = Screen(default_char=Char(char=" ", style=parent_style))
+        temp_screen.show_cursor = screen.show_cursor
+        temp_write_position = WritePosition(
+            xpos=0, ypos=0, width=virtual_width, height=virtual_height
+        )
+
+        temp_mouse_handlers = MouseHandlers()
+
+        self.content.write_to_screen(
+            temp_screen,
+            temp_mouse_handlers,
+            temp_write_position,
+            parent_style,
+            erase_bg,
+            z_index,
+        )
+        temp_screen.draw_all_floats()
+
+        # If anything in the virtual screen is focused, move vertical scroll to
+        from prompt_toolkit.application import get_app
+
+        focused_window = get_app().layout.current_window
+
+        try:
+            visible_win_write_pos = temp_screen.visible_windows_to_write_positions[
+                focused_window
+            ]
+        except KeyError:
+            pass  # No window focused here. Don't scroll.
+        else:
+            # Make sure this window is visible.
+            self._make_window_visible(
+                write_position.height,
+                virtual_height,
+                visible_win_write_pos,
+                temp_screen.cursor_positions.get(focused_window),
+            )
+
+        # Copy over virtual screen and zero width escapes to real screen.
+        self._copy_over_screen(screen, temp_screen, write_position, virtual_width)
+
+        # Copy over mouse handlers.
+        self._copy_over_mouse_handlers(
+            mouse_handlers, temp_mouse_handlers, write_position, virtual_width
+        )
+
+        # Set screen.width/height.
+        ypos = write_position.ypos
+        xpos = write_position.xpos
+
+        screen.width = max(screen.width, xpos + virtual_width)
+        screen.height = max(screen.height, ypos + write_position.height)
+
+        # Copy over window write positions.
+        self._copy_over_write_positions(screen, temp_screen, write_position)
+
+        if temp_screen.show_cursor:
+            screen.show_cursor = True
+
+        # Copy over cursor positions, if they are visible.
+        for window, point in temp_screen.cursor_positions.items():
+            if (
+                0 <= point.x < write_position.width
+                and self.vertical_scroll
+                <= point.y
+                < write_position.height + self.vertical_scroll
+            ):
+                screen.cursor_positions[window] = Point(
+                    x=point.x + xpos, y=point.y + ypos - self.vertical_scroll
+                )
+
+        # Copy over menu positions, but clip them to the visible area.
+        for window, point in temp_screen.menu_positions.items():
+            screen.menu_positions[window] = self._clip_point_to_visible_area(
+                Point(x=point.x + xpos, y=point.y + ypos - self.vertical_scroll),
+                write_position,
+            )
+
+        # Draw scrollbar.
+        if show_scrollbar:
+            self._draw_scrollbar(
+                write_position,
+                virtual_height,
+                screen,
+            )
+
+    def _clip_point_to_visible_area(
+        self, point: Point, write_position: WritePosition
+    ) -> Point:
+        """
+        Ensure that the cursor and menu positions always are always reported
+        """
+        if point.x < write_position.xpos:
+            point = point._replace(x=write_position.xpos)
+        if point.y < write_position.ypos:
+            point = point._replace(y=write_position.ypos)
+        if point.x >= write_position.xpos + write_position.width:
+            point = point._replace(x=write_position.xpos + write_position.width - 1)
+        if point.y >= write_position.ypos + write_position.height:
+            point = point._replace(y=write_position.ypos + write_position.height - 1)
+
+        return point
+
+    def _copy_over_screen(
+        self,
+        screen: Screen,
+        temp_screen: Screen,
+        write_position: WritePosition,
+        virtual_width: int,
+    ) -> None:
+        """
+        Copy over visible screen content and "zero width escape sequences".
+        """
+        ypos = write_position.ypos
+        xpos = write_position.xpos
+
+        for y in range(write_position.height):
+            temp_row = temp_screen.data_buffer[y + self.vertical_scroll]
+            row = screen.data_buffer[y + ypos]
+            temp_zero_width_escapes = temp_screen.zero_width_escapes[
+                y + self.vertical_scroll
+            ]
+            zero_width_escapes = screen.zero_width_escapes[y + ypos]
+
+            for x in range(virtual_width):
+                row[x + xpos] = temp_row[x]
+
+                if x in temp_zero_width_escapes:
+                    zero_width_escapes[x + xpos] = temp_zero_width_escapes[x]
+
+    def _copy_over_mouse_handlers(
+        self,
+        mouse_handlers: MouseHandlers,
+        temp_mouse_handlers: MouseHandlers,
+        write_position: WritePosition,
+        virtual_width: int,
+    ) -> None:
+        """
+        Copy over mouse handlers from virtual screen to real screen.
+
+        Note: we take `virtual_width` because we don't want to copy over mouse
+              handlers that we possibly have behind the scrollbar.
+        """
+        ypos = write_position.ypos
+        xpos = write_position.xpos
+
+        # Cache mouse handlers when wrapping them. Very often the same mouse
+        # handler is registered for many positions.
+        mouse_handler_wrappers: Dict[MouseHandler, MouseHandler] = {}
+
+        def wrap_mouse_handler(handler: MouseHandler) -> MouseHandler:
+            "Wrap mouse handler. Translate coordinates in `MouseEvent`."
+            if handler not in mouse_handler_wrappers:
+
+                def new_handler(event: MouseEvent) -> None:
+                    new_event = MouseEvent(
+                        position=Point(
+                            x=event.position.x - xpos,
+                            y=event.position.y + self.vertical_scroll - ypos,
+                        ),
+                        event_type=event.event_type,
+                        button=event.button,
+                        modifiers=event.modifiers,
+                    )
+                    handler(new_event)
+
+                mouse_handler_wrappers[handler] = new_handler
+            return mouse_handler_wrappers[handler]
+
+        # Copy handlers.
+        mouse_handlers_dict = mouse_handlers.mouse_handlers
+        temp_mouse_handlers_dict = temp_mouse_handlers.mouse_handlers
+
+        for y in range(write_position.height):
+            if y in temp_mouse_handlers_dict:
+                temp_mouse_row = temp_mouse_handlers_dict[y + self.vertical_scroll]
+                mouse_row = mouse_handlers_dict[y + ypos]
+                for x in range(virtual_width):
+                    if x in temp_mouse_row:
+                        mouse_row[x + xpos] = wrap_mouse_handler(temp_mouse_row[x])
+
+    def _copy_over_write_positions(
+        self, screen: Screen, temp_screen: Screen, write_position: WritePosition
+    ) -> None:
+        """
+        Copy over window write positions.
+        """
+        ypos = write_position.ypos
+        xpos = write_position.xpos
+
+        for win, write_pos in temp_screen.visible_windows_to_write_positions.items():
+            screen.visible_windows_to_write_positions[win] = WritePosition(
+                xpos=write_pos.xpos + xpos,
+                ypos=write_pos.ypos + ypos - self.vertical_scroll,
+                # TODO: if the window is only partly visible, then truncate width/height.
+                #       This could be important if we have nested ScrollablePanes.
+                height=write_pos.height,
+                width=write_pos.width,
+            )
+
+    def is_modal(self) -> bool:
+        return self.content.is_modal()
+
+    def get_key_bindings(self) -> Optional[KeyBindingsBase]:
+        return self.content.get_key_bindings()
+
+    def get_children(self) -> List["Container"]:
+        return [self.content]
+
+    def _make_window_visible(
+        self,
+        visible_height: int,
+        virtual_height: int,
+        visible_win_write_pos: WritePosition,
+        cursor_position: Optional[Point],
+    ) -> None:
+        """
+        Scroll the scrollable pane, so that this window becomes visible.
+
+        :param visible_height: Height of this `ScrollablePane` that is rendered.
+        :param virtual_height: Height of the virtual, temp screen.
+        :param visible_win_write_pos: `WritePosition` of the nested window on the
+            temp screen.
+        :param cursor_position: The location of the cursor position of this
+            window on the temp screen.
+        """
+        # Start with maximum allowed scroll range, and then reduce according to
+        # the focused window and cursor position.
+        min_scroll = 0
+        max_scroll = virtual_height - visible_height
+
+        if self.keep_cursor_visible():
+            # Reduce min/max scroll according to the cursor in the focused window.
+            if cursor_position is not None:
+                offsets = self.scroll_offsets
+                cpos_min_scroll = (
+                    cursor_position.y - visible_height + 1 + offsets.bottom
+                )
+                cpos_max_scroll = cursor_position.y - offsets.top
+                min_scroll = max(min_scroll, cpos_min_scroll)
+                max_scroll = max(0, min(max_scroll, cpos_max_scroll))
+
+        if self.keep_focused_window_visible():
+            # Reduce min/max scroll according to focused window position.
+            # If the window is small enough, bot the top and bottom of the window
+            # should be visible.
+            if visible_win_write_pos.height <= visible_height:
+                window_min_scroll = (
+                    visible_win_write_pos.ypos
+                    + visible_win_write_pos.height
+                    - visible_height
+                )
+                window_max_scroll = visible_win_write_pos.ypos
+            else:
+                # Window does not fit on the screen. Make sure at least the whole
+                # screen is occupied with this window, and nothing else is shown.
+                window_min_scroll = visible_win_write_pos.ypos
+                window_max_scroll = (
+                    visible_win_write_pos.ypos
+                    + visible_win_write_pos.height
+                    - visible_height
+                )
+
+            min_scroll = max(min_scroll, window_min_scroll)
+            max_scroll = min(max_scroll, window_max_scroll)
+
+        if min_scroll > max_scroll:
+            min_scroll = max_scroll  # Should not happen.
+
+        # Finally, properly clip the vertical scroll.
+        if self.vertical_scroll > max_scroll:
+            self.vertical_scroll = max_scroll
+        if self.vertical_scroll < min_scroll:
+            self.vertical_scroll = min_scroll
+
+    def _draw_scrollbar(
+        self, write_position: WritePosition, content_height: int, screen: Screen
+    ) -> None:
+        """
+        Draw the scrollbar on the screen.
+
+        Note: There is some code duplication with the `ScrollbarMargin`
+              implementation.
+        """
+
+        window_height = write_position.height
+        display_arrows = self.display_arrows()
+
+        if display_arrows:
+            window_height -= 2
+
+        try:
+            fraction_visible = write_position.height / float(content_height)
+            fraction_above = self.vertical_scroll / float(content_height)
+
+            scrollbar_height = int(
+                min(window_height, max(1, window_height * fraction_visible))
+            )
+            scrollbar_top = int(window_height * fraction_above)
+        except ZeroDivisionError:
+            return
+        else:
+
+            def is_scroll_button(row: int) -> bool:
+                "True if we should display a button on this row."
+                return scrollbar_top <= row <= scrollbar_top + scrollbar_height
+
+            xpos = write_position.xpos + write_position.width - 1
+            ypos = write_position.ypos
+            data_buffer = screen.data_buffer
+
+            # Up arrow.
+            if display_arrows:
+                data_buffer[ypos][xpos] = Char(
+                    self.up_arrow_symbol, "class:scrollbar.arrow"
+                )
+                ypos += 1
+
+            # Scrollbar body.
+            scrollbar_background = "class:scrollbar.background"
+            scrollbar_background_start = "class:scrollbar.background,scrollbar.start"
+            scrollbar_button = "class:scrollbar.button"
+            scrollbar_button_end = "class:scrollbar.button,scrollbar.end"
+
+            for i in range(window_height):
+                style = ""
+                if is_scroll_button(i):
+                    if not is_scroll_button(i + 1):
+                        # Give the last cell a different style, because we want
+                        # to underline this.
+                        style = scrollbar_button_end
+                    else:
+                        style = scrollbar_button
+                else:
+                    if is_scroll_button(i + 1):
+                        style = scrollbar_background_start
+                    else:
+                        style = scrollbar_background
+
+                data_buffer[ypos][xpos] = Char(" ", style)
+                ypos += 1
+
+            # Down arrow
+            if display_arrows:
+                data_buffer[ypos][xpos] = Char(
+                    self.down_arrow_symbol, "class:scrollbar.arrow"
+                )
diff --git a/src/prompt_toolkit/layout/utils.py b/src/prompt_toolkit/layout/utils.py
new file mode 100644
index 0000000..cebdf28
--- /dev/null
+++ b/src/prompt_toolkit/layout/utils.py
@@ -0,0 +1,80 @@
+from typing import TYPE_CHECKING, Iterable, List, TypeVar, Union, cast, overload
+
+from prompt_toolkit.formatted_text.base import OneStyleAndTextTuple
+
+if TYPE_CHECKING:
+    from typing_extensions import SupportsIndex
+
+__all__ = [
+    "explode_text_fragments",
+]
+
+_T = TypeVar("_T", bound=OneStyleAndTextTuple)
+
+
+class _ExplodedList(List[_T]):
+    """
+    Wrapper around a list, that marks it as 'exploded'.
+
+    As soon as items are added or the list is extended, the new items are
+    automatically exploded as well.
+    """
+
+    exploded = True
+
+    def append(self, item: _T) -> None:
+        self.extend([item])
+
+    def extend(self, lst: Iterable[_T]) -> None:
+        super().extend(explode_text_fragments(lst))
+
+    def insert(self, index: "SupportsIndex", item: _T) -> None:
+        raise NotImplementedError  # TODO
+
+    # TODO: When creating a copy() or [:], return also an _ExplodedList.
+
+    @overload
+    def __setitem__(self, index: "SupportsIndex", value: _T) -> None:
+        ...
+
+    @overload
+    def __setitem__(self, index: slice, value: Iterable[_T]) -> None:
+        ...
+
+    def __setitem__(
+        self, index: Union["SupportsIndex", slice], value: Union[_T, Iterable[_T]]
+    ) -> None:
+        """
+        Ensure that when `(style_str, 'long string')` is set, the string will be
+        exploded.
+        """
+        if not isinstance(index, slice):
+            int_index = index.__index__()
+            index = slice(int_index, int_index + 1)
+        if isinstance(value, tuple):  # In case of `OneStyleAndTextTuple`.
+            value = cast("List[_T]", [value])
+
+        super().__setitem__(index, explode_text_fragments(cast("Iterable[_T]", value)))
+
+
+def explode_text_fragments(fragments: Iterable[_T]) -> _ExplodedList[_T]:
+    """
+    Turn a list of (style_str, text) tuples into another list where each string is
+    exactly one character.
+
+    It should be fine to call this function several times. Calling this on a
+    list that is already exploded, is a null operation.
+
+    :param fragments: List of (style, text) tuples.
+    """
+    # When the fragments is already exploded, don't explode again.
+    if isinstance(fragments, _ExplodedList):
+        return fragments
+
+    result: List[_T] = []
+
+    for style, string, *rest in fragments:
+        for c in string:
+            result.append((style, c, *rest))  # type: ignore
+
+    return _ExplodedList(result)
diff --git a/src/prompt_toolkit/lexers/__init__.py b/src/prompt_toolkit/lexers/__init__.py
new file mode 100644
index 0000000..3e875e6
--- /dev/null
+++ b/src/prompt_toolkit/lexers/__init__.py
@@ -0,0 +1,18 @@
+"""
+Lexer interface and implementations.
+Used for syntax highlighting.
+"""
+from .base import DynamicLexer, Lexer, SimpleLexer
+from .pygments import PygmentsLexer, RegexSync, SyncFromStart, SyntaxSync
+
+__all__ = [
+    # Base.
+    "Lexer",
+    "SimpleLexer",
+    "DynamicLexer",
+    # Pygments.
+    "PygmentsLexer",
+    "RegexSync",
+    "SyncFromStart",
+    "SyntaxSync",
+]
diff --git a/src/prompt_toolkit/lexers/base.py b/src/prompt_toolkit/lexers/base.py
new file mode 100644
index 0000000..dd9f245
--- /dev/null
+++ b/src/prompt_toolkit/lexers/base.py
@@ -0,0 +1,82 @@
+"""
+Base classes for prompt_toolkit lexers.
+"""
+from abc import ABCMeta, abstractmethod
+from typing import Callable, Hashable, Optional
+
+from prompt_toolkit.document import Document
+from prompt_toolkit.formatted_text.base import StyleAndTextTuples
+
+__all__ = [
+    "Lexer",
+    "SimpleLexer",
+    "DynamicLexer",
+]
+
+
+class Lexer(metaclass=ABCMeta):
+    """
+    Base class for all lexers.
+    """
+
+    @abstractmethod
+    def lex_document(self, document: Document) -> Callable[[int], StyleAndTextTuples]:
+        """
+        Takes a :class:`~prompt_toolkit.document.Document` and returns a
+        callable that takes a line number and returns a list of
+        ``(style_str, text)`` tuples for that line.
+
+        XXX: Note that in the past, this was supposed to return a list
+             of ``(Token, text)`` tuples, just like a Pygments lexer.
+        """
+
+    def invalidation_hash(self) -> Hashable:
+        """
+        When this changes, `lex_document` could give a different output.
+        (Only used for `DynamicLexer`.)
+        """
+        return id(self)
+
+
+class SimpleLexer(Lexer):
+    """
+    Lexer that doesn't do any tokenizing and returns the whole input as one
+    token.
+
+    :param style: The style string for this lexer.
+    """
+
+    def __init__(self, style: str = "") -> None:
+        self.style = style
+
+    def lex_document(self, document: Document) -> Callable[[int], StyleAndTextTuples]:
+        lines = document.lines
+
+        def get_line(lineno: int) -> StyleAndTextTuples:
+            "Return the tokens for the given line."
+            try:
+                return [(self.style, lines[lineno])]
+            except IndexError:
+                return []
+
+        return get_line
+
+
+class DynamicLexer(Lexer):
+    """
+    Lexer class that can dynamically returns any Lexer.
+
+    :param get_lexer: Callable that returns a :class:`.Lexer` instance.
+    """
+
+    def __init__(self, get_lexer: Callable[[], Optional[Lexer]]) -> None:
+        self.get_lexer = get_lexer
+        self._dummy = SimpleLexer()
+
+    def lex_document(self, document: Document) -> Callable[[int], StyleAndTextTuples]:
+        lexer = self.get_lexer() or self._dummy
+        return lexer.lex_document(document)
+
+    def invalidation_hash(self) -> Hashable:
+        lexer = self.get_lexer() or self._dummy
+        return id(lexer)
diff --git a/src/prompt_toolkit/lexers/pygments.py b/src/prompt_toolkit/lexers/pygments.py
new file mode 100644
index 0000000..d50f8af
--- /dev/null
+++ b/src/prompt_toolkit/lexers/pygments.py
@@ -0,0 +1,335 @@
+"""
+Adaptor classes for using Pygments lexers within prompt_toolkit.
+
+This includes syntax synchronization code, so that we don't have to start
+lexing at the beginning of a document, when displaying a very large text.
+"""
+import re
+from abc import ABCMeta, abstractmethod
+from typing import (
+    TYPE_CHECKING,
+    Callable,
+    Dict,
+    Generator,
+    Iterable,
+    Optional,
+    Tuple,
+    Type,
+)
+
+from prompt_toolkit.document import Document
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.formatted_text.base import StyleAndTextTuples
+from prompt_toolkit.formatted_text.utils import split_lines
+from prompt_toolkit.styles.pygments import pygments_token_to_classname
+
+from .base import Lexer, SimpleLexer
+
+if TYPE_CHECKING:
+    from pygments.lexer import Lexer as PygmentsLexerCls
+
+__all__ = [
+    "PygmentsLexer",
+    "SyntaxSync",
+    "SyncFromStart",
+    "RegexSync",
+]
+
+
+class SyntaxSync(metaclass=ABCMeta):
+    """
+    Syntax synchroniser. This is a tool that finds a start position for the
+    lexer. This is especially important when editing big documents; we don't
+    want to start the highlighting by running the lexer from the beginning of
+    the file. That is very slow when editing.
+    """
+
+    @abstractmethod
+    def get_sync_start_position(
+        self, document: Document, lineno: int
+    ) -> Tuple[int, int]:
+        """
+        Return the position from where we can start lexing as a (row, column)
+        tuple.
+
+        :param document: `Document` instance that contains all the lines.
+        :param lineno: The line that we want to highlight. (We need to return
+            this line, or an earlier position.)
+        """
+
+
+class SyncFromStart(SyntaxSync):
+    """
+    Always start the syntax highlighting from the beginning.
+    """
+
+    def get_sync_start_position(
+        self, document: Document, lineno: int
+    ) -> Tuple[int, int]:
+        return 0, 0
+
+
+class RegexSync(SyntaxSync):
+    """
+    Synchronize by starting at a line that matches the given regex pattern.
+    """
+
+    # Never go more than this amount of lines backwards for synchronisation.
+    # That would be too CPU intensive.
+    MAX_BACKWARDS = 500
+
+    # Start lexing at the start, if we are in the first 'n' lines and no
+    # synchronisation position was found.
+    FROM_START_IF_NO_SYNC_POS_FOUND = 100
+
+    def __init__(self, pattern: str) -> None:
+        self._compiled_pattern = re.compile(pattern)
+
+    def get_sync_start_position(
+        self, document: Document, lineno: int
+    ) -> Tuple[int, int]:
+        """
+        Scan backwards, and find a possible position to start.
+        """
+        pattern = self._compiled_pattern
+        lines = document.lines
+
+        # Scan upwards, until we find a point where we can start the syntax
+        # synchronisation.
+        for i in range(lineno, max(-1, lineno - self.MAX_BACKWARDS), -1):
+            match = pattern.match(lines[i])
+            if match:
+                return i, match.start()
+
+        # No synchronisation point found. If we aren't that far from the
+        # beginning, start at the very beginning, otherwise, just try to start
+        # at the current line.
+        if lineno < self.FROM_START_IF_NO_SYNC_POS_FOUND:
+            return 0, 0
+        else:
+            return lineno, 0
+
+    @classmethod
+    def from_pygments_lexer_cls(cls, lexer_cls: "PygmentsLexerCls") -> "RegexSync":
+        """
+        Create a :class:`.RegexSync` instance for this Pygments lexer class.
+        """
+        patterns = {
+            # For Python, start highlighting at any class/def block.
+            "Python": r"^\s*(class|def)\s+",
+            "Python 3": r"^\s*(class|def)\s+",
+            # For HTML, start at any open/close tag definition.
+            "HTML": r"<[/a-zA-Z]",
+            # For javascript, start at a function.
+            "JavaScript": r"\bfunction\b"
+            # TODO: Add definitions for other languages.
+            #       By default, we start at every possible line.
+        }
+        p = patterns.get(lexer_cls.name, "^")
+        return cls(p)
+
+
+class _TokenCache(Dict[Tuple[str, ...], str]):
+    """
+    Cache that converts Pygments tokens into `prompt_toolkit` style objects.
+
+    ``Token.A.B.C`` will be converted into:
+    ``class:pygments,pygments.A,pygments.A.B,pygments.A.B.C``
+    """
+
+    def __missing__(self, key: Tuple[str, ...]) -> str:
+        result = "class:" + pygments_token_to_classname(key)
+        self[key] = result
+        return result
+
+
+_token_cache = _TokenCache()
+
+
+class PygmentsLexer(Lexer):
+    """
+    Lexer that calls a pygments lexer.
+
+    Example::
+
+        from pygments.lexers.html import HtmlLexer
+        lexer = PygmentsLexer(HtmlLexer)
+
+    Note: Don't forget to also load a Pygments compatible style. E.g.::
+
+        from prompt_toolkit.styles.from_pygments import style_from_pygments_cls
+        from pygments.styles import get_style_by_name
+        style = style_from_pygments_cls(get_style_by_name('monokai'))
+
+    :param pygments_lexer_cls: A `Lexer` from Pygments.
+    :param sync_from_start: Start lexing at the start of the document. This
+        will always give the best results, but it will be slow for bigger
+        documents. (When the last part of the document is display, then the
+        whole document will be lexed by Pygments on every key stroke.) It is
+        recommended to disable this for inputs that are expected to be more
+        than 1,000 lines.
+    :param syntax_sync: `SyntaxSync` object.
+    """
+
+    # Minimum amount of lines to go backwards when starting the parser.
+    # This is important when the lines are retrieved in reverse order, or when
+    # scrolling upwards. (Due to the complexity of calculating the vertical
+    # scroll offset in the `Window` class, lines are not always retrieved in
+    # order.)
+    MIN_LINES_BACKWARDS = 50
+
+    # When a parser was started this amount of lines back, read the parser
+    # until we get the current line. Otherwise, start a new parser.
+    # (This should probably be bigger than MIN_LINES_BACKWARDS.)
+    REUSE_GENERATOR_MAX_DISTANCE = 100
+
+    def __init__(
+        self,
+        pygments_lexer_cls: Type["PygmentsLexerCls"],
+        sync_from_start: FilterOrBool = True,
+        syntax_sync: Optional[SyntaxSync] = None,
+    ) -> None:
+
+        self.pygments_lexer_cls = pygments_lexer_cls
+        self.sync_from_start = to_filter(sync_from_start)
+
+        # Instantiate the Pygments lexer.
+        self.pygments_lexer = pygments_lexer_cls(
+            stripnl=False, stripall=False, ensurenl=False
+        )
+
+        # Create syntax sync instance.
+        self.syntax_sync = syntax_sync or RegexSync.from_pygments_lexer_cls(
+            pygments_lexer_cls
+        )
+
+    @classmethod
+    def from_filename(
+        cls, filename: str, sync_from_start: FilterOrBool = True
+    ) -> "Lexer":
+        """
+        Create a `Lexer` from a filename.
+        """
+        # Inline imports: the Pygments dependency is optional!
+        from pygments.lexers import get_lexer_for_filename
+        from pygments.util import ClassNotFound
+
+        try:
+            pygments_lexer = get_lexer_for_filename(filename)
+        except ClassNotFound:
+            return SimpleLexer()
+        else:
+            return cls(pygments_lexer.__class__, sync_from_start=sync_from_start)
+
+    def lex_document(self, document: Document) -> Callable[[int], StyleAndTextTuples]:
+        """
+        Create a lexer function that takes a line number and returns the list
+        of (style_str, text) tuples as the Pygments lexer returns for that line.
+        """
+        LineGenerator = Generator[Tuple[int, StyleAndTextTuples], None, None]
+
+        # Cache of already lexed lines.
+        cache: Dict[int, StyleAndTextTuples] = {}
+
+        # Pygments generators that are currently lexing.
+        # Map lexer generator to the line number.
+        line_generators: Dict[LineGenerator, int] = {}
+
+        def get_syntax_sync() -> SyntaxSync:
+            "The Syntax synchronisation object that we currently use."
+            if self.sync_from_start():
+                return SyncFromStart()
+            else:
+                return self.syntax_sync
+
+        def find_closest_generator(i: int) -> Optional[LineGenerator]:
+            "Return a generator close to line 'i', or None if none was found."
+            for generator, lineno in line_generators.items():
+                if lineno < i and i - lineno < self.REUSE_GENERATOR_MAX_DISTANCE:
+                    return generator
+            return None
+
+        def create_line_generator(start_lineno: int, column: int = 0) -> LineGenerator:
+            """
+            Create a generator that yields the lexed lines.
+            Each iteration it yields a (line_number, [(style_str, text), ...]) tuple.
+            """
+
+            def get_text_fragments() -> Iterable[Tuple[str, str]]:
+                text = "\n".join(document.lines[start_lineno:])[column:]
+
+                # We call `get_text_fragments_unprocessed`, because `get_tokens` will
+                # still replace \r\n and \r by \n.  (We don't want that,
+                # Pygments should return exactly the same amount of text, as we
+                # have given as input.)
+                for _, t, v in self.pygments_lexer.get_tokens_unprocessed(text):
+                    # Turn Pygments `Token` object into prompt_toolkit style
+                    # strings.
+                    yield _token_cache[t], v
+
+            yield from enumerate(split_lines(list(get_text_fragments())), start_lineno)
+
+        def get_generator(i: int) -> LineGenerator:
+            """
+            Find an already started generator that is close, or create a new one.
+            """
+            # Find closest line generator.
+            generator = find_closest_generator(i)
+            if generator:
+                return generator
+
+            # No generator found. Determine starting point for the syntax
+            # synchronisation first.
+
+            # Go at least x lines back. (Make scrolling upwards more
+            # efficient.)
+            i = max(0, i - self.MIN_LINES_BACKWARDS)
+
+            if i == 0:
+                row = 0
+                column = 0
+            else:
+                row, column = get_syntax_sync().get_sync_start_position(document, i)
+
+            # Find generator close to this point, or otherwise create a new one.
+            generator = find_closest_generator(i)
+            if generator:
+                return generator
+            else:
+                generator = create_line_generator(row, column)
+
+            # If the column is not 0, ignore the first line. (Which is
+            # incomplete. This happens when the synchronisation algorithm tells
+            # us to start parsing in the middle of a line.)
+            if column:
+                next(generator)
+                row += 1
+
+            line_generators[generator] = row
+            return generator
+
+        def get_line(i: int) -> StyleAndTextTuples:
+            "Return the tokens for a given line number."
+            try:
+                return cache[i]
+            except KeyError:
+                generator = get_generator(i)
+
+                # Exhaust the generator, until we find the requested line.
+                for num, line in generator:
+                    cache[num] = line
+                    if num == i:
+                        line_generators[generator] = i
+
+                        # Remove the next item from the cache.
+                        # (It could happen that it's already there, because of
+                        # another generator that started filling these lines,
+                        # but we want to synchronise these lines with the
+                        # current lexer's state.)
+                        if num + 1 in cache:
+                            del cache[num + 1]
+
+                        return cache[num]
+            return []
+
+        return get_line
diff --git a/src/prompt_toolkit/log.py b/src/prompt_toolkit/log.py
new file mode 100644
index 0000000..36ceced
--- /dev/null
+++ b/src/prompt_toolkit/log.py
@@ -0,0 +1,10 @@
+"""
+Logging configuration.
+"""
+import logging
+
+__all__ = [
+    "logger",
+]
+
+logger = logging.getLogger(__package__)
diff --git a/src/prompt_toolkit/mouse_events.py b/src/prompt_toolkit/mouse_events.py
new file mode 100644
index 0000000..e10ff03
--- /dev/null
+++ b/src/prompt_toolkit/mouse_events.py
@@ -0,0 +1,88 @@
+"""
+Mouse events.
+
+
+How it works
+------------
+
+The renderer has a 2 dimensional grid of mouse event handlers.
+(`prompt_toolkit.layout.MouseHandlers`.) When the layout is rendered, the
+`Window` class will make sure that this grid will also be filled with
+callbacks. For vt100 terminals, mouse events are received through stdin, just
+like any other key press. There is a handler among the key bindings that
+catches these events and forwards them to such a mouse event handler. It passes
+through the `Window` class where the coordinates are translated from absolute
+coordinates to coordinates relative to the user control, and there
+`UIControl.mouse_handler` is called.
+"""
+from enum import Enum
+from typing import FrozenSet
+
+from .data_structures import Point
+
+__all__ = ["MouseEventType", "MouseButton", "MouseModifier", "MouseEvent"]
+
+
+class MouseEventType(Enum):
+    # Mouse up: This same event type is fired for all three events: left mouse
+    # up, right mouse up, or middle mouse up
+    MOUSE_UP = "MOUSE_UP"
+
+    # Mouse down: This implicitly refers to the left mouse down (this event is
+    # not fired upon pressing the middle or right mouse buttons).
+    MOUSE_DOWN = "MOUSE_DOWN"
+
+    SCROLL_UP = "SCROLL_UP"
+    SCROLL_DOWN = "SCROLL_DOWN"
+
+    # Triggered when the left mouse button is held down, and the mouse moves
+    MOUSE_MOVE = "MOUSE_MOVE"
+
+
+class MouseButton(Enum):
+    LEFT = "LEFT"
+    MIDDLE = "MIDDLE"
+    RIGHT = "RIGHT"
+
+    # When we're scrolling, or just moving the mouse and not pressing a button.
+    NONE = "NONE"
+
+    # This is for when we don't know which mouse button was pressed, but we do
+    # know that one has been pressed during this mouse event (as opposed to
+    # scrolling, for example)
+    UNKNOWN = "UNKNOWN"
+
+
+class MouseModifier(Enum):
+    SHIFT = "SHIFT"
+    ALT = "ALT"
+    CONTROL = "CONTROL"
+
+
+class MouseEvent:
+    """
+    Mouse event, sent to `UIControl.mouse_handler`.
+
+    :param position: `Point` instance.
+    :param event_type: `MouseEventType`.
+    """
+
+    def __init__(
+        self,
+        position: Point,
+        event_type: MouseEventType,
+        button: MouseButton,
+        modifiers: FrozenSet[MouseModifier],
+    ) -> None:
+        self.position = position
+        self.event_type = event_type
+        self.button = button
+        self.modifiers = modifiers
+
+    def __repr__(self) -> str:
+        return "MouseEvent({!r},{!r},{!r},{!r})".format(
+            self.position,
+            self.event_type,
+            self.button,
+            self.modifiers,
+        )
diff --git a/src/prompt_toolkit/output/__init__.py b/src/prompt_toolkit/output/__init__.py
new file mode 100644
index 0000000..7b90b47
--- /dev/null
+++ b/src/prompt_toolkit/output/__init__.py
@@ -0,0 +1,13 @@
+from .base import DummyOutput, Output
+from .color_depth import ColorDepth
+from .defaults import create_output
+
+__all__ = [
+    # Base.
+    "Output",
+    "DummyOutput",
+    # Color depth.
+    "ColorDepth",
+    # Defaults.
+    "create_output",
+]
diff --git a/src/prompt_toolkit/output/base.py b/src/prompt_toolkit/output/base.py
new file mode 100644
index 0000000..c78677b
--- /dev/null
+++ b/src/prompt_toolkit/output/base.py
@@ -0,0 +1,329 @@
+"""
+Interface for an output.
+"""
+from abc import ABCMeta, abstractmethod
+from typing import Optional, TextIO
+
+from prompt_toolkit.cursor_shapes import CursorShape
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.styles import Attrs
+
+from .color_depth import ColorDepth
+
+__all__ = [
+    "Output",
+    "DummyOutput",
+]
+
+
+class Output(metaclass=ABCMeta):
+    """
+    Base class defining the output interface for a
+    :class:`~prompt_toolkit.renderer.Renderer`.
+
+    Actual implementations are
+    :class:`~prompt_toolkit.output.vt100.Vt100_Output` and
+    :class:`~prompt_toolkit.output.win32.Win32Output`.
+    """
+
+    stdout: Optional[TextIO] = None
+
+    @abstractmethod
+    def fileno(self) -> int:
+        "Return the file descriptor to which we can write for the output."
+
+    @abstractmethod
+    def encoding(self) -> str:
+        """
+        Return the encoding for this output, e.g. 'utf-8'.
+        (This is used mainly to know which characters are supported by the
+        output the data, so that the UI can provide alternatives, when
+        required.)
+        """
+
+    @abstractmethod
+    def write(self, data: str) -> None:
+        "Write text (Terminal escape sequences will be removed/escaped.)"
+
+    @abstractmethod
+    def write_raw(self, data: str) -> None:
+        "Write text."
+
+    @abstractmethod
+    def set_title(self, title: str) -> None:
+        "Set terminal title."
+
+    @abstractmethod
+    def clear_title(self) -> None:
+        "Clear title again. (or restore previous title.)"
+
+    @abstractmethod
+    def flush(self) -> None:
+        "Write to output stream and flush."
+
+    @abstractmethod
+    def erase_screen(self) -> None:
+        """
+        Erases the screen with the background colour and moves the cursor to
+        home.
+        """
+
+    @abstractmethod
+    def enter_alternate_screen(self) -> None:
+        "Go to the alternate screen buffer. (For full screen applications)."
+
+    @abstractmethod
+    def quit_alternate_screen(self) -> None:
+        "Leave the alternate screen buffer."
+
+    @abstractmethod
+    def enable_mouse_support(self) -> None:
+        "Enable mouse."
+
+    @abstractmethod
+    def disable_mouse_support(self) -> None:
+        "Disable mouse."
+
+    @abstractmethod
+    def erase_end_of_line(self) -> None:
+        """
+        Erases from the current cursor position to the end of the current line.
+        """
+
+    @abstractmethod
+    def erase_down(self) -> None:
+        """
+        Erases the screen from the current line down to the bottom of the
+        screen.
+        """
+
+    @abstractmethod
+    def reset_attributes(self) -> None:
+        "Reset color and styling attributes."
+
+    @abstractmethod
+    def set_attributes(self, attrs: Attrs, color_depth: ColorDepth) -> None:
+        "Set new color and styling attributes."
+
+    @abstractmethod
+    def disable_autowrap(self) -> None:
+        "Disable auto line wrapping."
+
+    @abstractmethod
+    def enable_autowrap(self) -> None:
+        "Enable auto line wrapping."
+
+    @abstractmethod
+    def cursor_goto(self, row: int = 0, column: int = 0) -> None:
+        "Move cursor position."
+
+    @abstractmethod
+    def cursor_up(self, amount: int) -> None:
+        "Move cursor `amount` place up."
+
+    @abstractmethod
+    def cursor_down(self, amount: int) -> None:
+        "Move cursor `amount` place down."
+
+    @abstractmethod
+    def cursor_forward(self, amount: int) -> None:
+        "Move cursor `amount` place forward."
+
+    @abstractmethod
+    def cursor_backward(self, amount: int) -> None:
+        "Move cursor `amount` place backward."
+
+    @abstractmethod
+    def hide_cursor(self) -> None:
+        "Hide cursor."
+
+    @abstractmethod
+    def show_cursor(self) -> None:
+        "Show cursor."
+
+    @abstractmethod
+    def set_cursor_shape(self, cursor_shape: CursorShape) -> None:
+        "Set cursor shape to block, beam or underline."
+
+    @abstractmethod
+    def reset_cursor_shape(self) -> None:
+        "Reset cursor shape."
+
+    def ask_for_cpr(self) -> None:
+        """
+        Asks for a cursor position report (CPR).
+        (VT100 only.)
+        """
+
+    @property
+    def responds_to_cpr(self) -> bool:
+        """
+        `True` if the `Application` can expect to receive a CPR response after
+        calling `ask_for_cpr` (this will come back through the corresponding
+        `Input`).
+
+        This is used to determine the amount of available rows we have below
+        the cursor position. In the first place, we have this so that the drop
+        down autocompletion menus are sized according to the available space.
+
+        On Windows, we don't need this, there we have
+        `get_rows_below_cursor_position`.
+        """
+        return False
+
+    @abstractmethod
+    def get_size(self) -> Size:
+        "Return the size of the output window."
+
+    def bell(self) -> None:
+        "Sound bell."
+
+    def enable_bracketed_paste(self) -> None:
+        "For vt100 only."
+
+    def disable_bracketed_paste(self) -> None:
+        "For vt100 only."
+
+    def reset_cursor_key_mode(self) -> None:
+        """
+        For vt100 only.
+        Put the terminal in normal cursor mode (instead of application mode).
+
+        See: https://vt100.net/docs/vt100-ug/chapter3.html
+        """
+
+    def scroll_buffer_to_prompt(self) -> None:
+        "For Win32 only."
+
+    def get_rows_below_cursor_position(self) -> int:
+        "For Windows only."
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_default_color_depth(self) -> ColorDepth:
+        """
+        Get default color depth for this output.
+
+        This value will be used if no color depth was explicitely passed to the
+        `Application`.
+
+        .. note::
+
+            If the `$PROMPT_TOOLKIT_COLOR_DEPTH` environment variable has been
+            set, then `outputs.defaults.create_output` will pass this value to
+            the implementation as the default_color_depth, which is returned
+            here. (This is not used when the output corresponds to a
+            prompt_toolkit SSH/Telnet session.)
+        """
+
+
+class DummyOutput(Output):
+    """
+    For testing. An output class that doesn't render anything.
+    """
+
+    def fileno(self) -> int:
+        "There is no sensible default for fileno()."
+        raise NotImplementedError
+
+    def encoding(self) -> str:
+        return "utf-8"
+
+    def write(self, data: str) -> None:
+        pass
+
+    def write_raw(self, data: str) -> None:
+        pass
+
+    def set_title(self, title: str) -> None:
+        pass
+
+    def clear_title(self) -> None:
+        pass
+
+    def flush(self) -> None:
+        pass
+
+    def erase_screen(self) -> None:
+        pass
+
+    def enter_alternate_screen(self) -> None:
+        pass
+
+    def quit_alternate_screen(self) -> None:
+        pass
+
+    def enable_mouse_support(self) -> None:
+        pass
+
+    def disable_mouse_support(self) -> None:
+        pass
+
+    def erase_end_of_line(self) -> None:
+        pass
+
+    def erase_down(self) -> None:
+        pass
+
+    def reset_attributes(self) -> None:
+        pass
+
+    def set_attributes(self, attrs: Attrs, color_depth: ColorDepth) -> None:
+        pass
+
+    def disable_autowrap(self) -> None:
+        pass
+
+    def enable_autowrap(self) -> None:
+        pass
+
+    def cursor_goto(self, row: int = 0, column: int = 0) -> None:
+        pass
+
+    def cursor_up(self, amount: int) -> None:
+        pass
+
+    def cursor_down(self, amount: int) -> None:
+        pass
+
+    def cursor_forward(self, amount: int) -> None:
+        pass
+
+    def cursor_backward(self, amount: int) -> None:
+        pass
+
+    def hide_cursor(self) -> None:
+        pass
+
+    def show_cursor(self) -> None:
+        pass
+
+    def set_cursor_shape(self, cursor_shape: CursorShape) -> None:
+        pass
+
+    def reset_cursor_shape(self) -> None:
+        pass
+
+    def ask_for_cpr(self) -> None:
+        pass
+
+    def bell(self) -> None:
+        pass
+
+    def enable_bracketed_paste(self) -> None:
+        pass
+
+    def disable_bracketed_paste(self) -> None:
+        pass
+
+    def scroll_buffer_to_prompt(self) -> None:
+        pass
+
+    def get_size(self) -> Size:
+        return Size(rows=40, columns=80)
+
+    def get_rows_below_cursor_position(self) -> int:
+        return 40
+
+    def get_default_color_depth(self) -> ColorDepth:
+        return ColorDepth.DEPTH_1_BIT
diff --git a/src/prompt_toolkit/output/color_depth.py b/src/prompt_toolkit/output/color_depth.py
new file mode 100644
index 0000000..a6166ba
--- /dev/null
+++ b/src/prompt_toolkit/output/color_depth.py
@@ -0,0 +1,58 @@
+import os
+from enum import Enum
+from typing import Optional
+
+__all__ = [
+    "ColorDepth",
+]
+
+
+class ColorDepth(str, Enum):
+    """
+    Possible color depth values for the output.
+    """
+
+    value: str
+
+    #: One color only.
+    DEPTH_1_BIT = "DEPTH_1_BIT"
+
+    #: ANSI Colors.
+    DEPTH_4_BIT = "DEPTH_4_BIT"
+
+    #: The default.
+    DEPTH_8_BIT = "DEPTH_8_BIT"
+
+    #: 24 bit True color.
+    DEPTH_24_BIT = "DEPTH_24_BIT"
+
+    # Aliases.
+    MONOCHROME = DEPTH_1_BIT
+    ANSI_COLORS_ONLY = DEPTH_4_BIT
+    DEFAULT = DEPTH_8_BIT
+    TRUE_COLOR = DEPTH_24_BIT
+
+    @classmethod
+    def from_env(cls) -> Optional["ColorDepth"]:
+        """
+        Return the color depth if the $PROMPT_TOOLKIT_COLOR_DEPTH environment
+        variable has been set.
+
+        This is a way to enforce a certain color depth in all prompt_toolkit
+        applications.
+        """
+        # Check the `PROMPT_TOOLKIT_COLOR_DEPTH` environment variable.
+        all_values = [i.value for i in ColorDepth]
+        if os.environ.get("PROMPT_TOOLKIT_COLOR_DEPTH") in all_values:
+            return cls(os.environ["PROMPT_TOOLKIT_COLOR_DEPTH"])
+
+        return None
+
+    @classmethod
+    def default(cls) -> "ColorDepth":
+        """
+        Return the default color depth for the default output.
+        """
+        from .defaults import create_output
+
+        return create_output().get_default_color_depth()
diff --git a/src/prompt_toolkit/output/conemu.py b/src/prompt_toolkit/output/conemu.py
new file mode 100644
index 0000000..fc46cc4
--- /dev/null
+++ b/src/prompt_toolkit/output/conemu.py
@@ -0,0 +1,63 @@
+import sys
+
+assert sys.platform == "win32"
+
+from typing import Any, Optional, TextIO
+
+from prompt_toolkit.data_structures import Size
+
+from .base import Output
+from .color_depth import ColorDepth
+from .vt100 import Vt100_Output
+from .win32 import Win32Output
+
+__all__ = [
+    "ConEmuOutput",
+]
+
+
+class ConEmuOutput:
+    """
+    ConEmu (Windows) output abstraction.
+
+    ConEmu is a Windows console application, but it also supports ANSI escape
+    sequences. This output class is actually a proxy to both `Win32Output` and
+    `Vt100_Output`. It uses `Win32Output` for console sizing and scrolling, but
+    all cursor movements and scrolling happens through the `Vt100_Output`.
+
+    This way, we can have 256 colors in ConEmu and Cmder. Rendering will be
+    even a little faster as well.
+
+    http://conemu.github.io/
+    http://gooseberrycreative.com/cmder/
+    """
+
+    def __init__(
+        self, stdout: TextIO, default_color_depth: Optional[ColorDepth] = None
+    ) -> None:
+        self.win32_output = Win32Output(stdout, default_color_depth=default_color_depth)
+        self.vt100_output = Vt100_Output(
+            stdout, lambda: Size(0, 0), default_color_depth=default_color_depth
+        )
+
+    @property
+    def responds_to_cpr(self) -> bool:
+        return False  # We don't need this on Windows.
+
+    def __getattr__(self, name: str) -> Any:
+        if name in (
+            "get_size",
+            "get_rows_below_cursor_position",
+            "enable_mouse_support",
+            "disable_mouse_support",
+            "scroll_buffer_to_prompt",
+            "get_win32_screen_buffer_info",
+            "enable_bracketed_paste",
+            "disable_bracketed_paste",
+        ):
+            return getattr(self.win32_output, name)
+        else:
+            return getattr(self.vt100_output, name)
+
+
+Output.register(ConEmuOutput)
diff --git a/src/prompt_toolkit/output/defaults.py b/src/prompt_toolkit/output/defaults.py
new file mode 100644
index 0000000..7fb0f89
--- /dev/null
+++ b/src/prompt_toolkit/output/defaults.py
@@ -0,0 +1,100 @@
+import sys
+from typing import Optional, TextIO, cast
+
+from prompt_toolkit.utils import (
+    get_bell_environment_variable,
+    get_term_environment_variable,
+    is_conemu_ansi,
+)
+
+from .base import DummyOutput, Output
+from .color_depth import ColorDepth
+from .plain_text import PlainTextOutput
+
+__all__ = [
+    "create_output",
+]
+
+
+def create_output(
+    stdout: Optional[TextIO] = None, always_prefer_tty: bool = False
+) -> Output:
+    """
+    Return an :class:`~prompt_toolkit.output.Output` instance for the command
+    line.
+
+    :param stdout: The stdout object
+    :param always_prefer_tty: When set, look for `sys.stderr` if `sys.stdout`
+        is not a TTY. Useful if `sys.stdout` is redirected to a file, but we
+        still want user input and output on the terminal.
+
+        By default, this is `False`. If `sys.stdout` is not a terminal (maybe
+        it's redirected to a file), then a `PlainTextOutput` will be returned.
+        That way, tools like `print_formatted_text` will write plain text into
+        that file.
+    """
+    # Consider TERM, PROMPT_TOOLKIT_BELL, and PROMPT_TOOLKIT_COLOR_DEPTH
+    # environment variables. Notice that PROMPT_TOOLKIT_COLOR_DEPTH value is
+    # the default that's used if the Application doesn't override it.
+    term_from_env = get_term_environment_variable()
+    bell_from_env = get_bell_environment_variable()
+    color_depth_from_env = ColorDepth.from_env()
+
+    if stdout is None:
+        # By default, render to stdout. If the output is piped somewhere else,
+        # render to stderr.
+        stdout = sys.stdout
+
+        if always_prefer_tty:
+            for io in [sys.stdout, sys.stderr]:
+                if io is not None and io.isatty():
+                    # (This is `None` when using `pythonw.exe` on Windows.)
+                    stdout = io
+                    break
+
+    # If the output is still `None`, use a DummyOutput.
+    # This happens for instance on Windows, when running the application under
+    # `pythonw.exe`. In that case, there won't be a terminal Window, and
+    # stdin/stdout/stderr are `None`.
+    if stdout is None:
+        return DummyOutput()
+
+    # If the patch_stdout context manager has been used, then sys.stdout is
+    # replaced by this proxy. For prompt_toolkit applications, we want to use
+    # the real stdout.
+    from prompt_toolkit.patch_stdout import StdoutProxy
+
+    while isinstance(stdout, StdoutProxy):
+        stdout = stdout.original_stdout
+
+    if sys.platform == "win32":
+        from .conemu import ConEmuOutput
+        from .win32 import Win32Output
+        from .windows10 import Windows10_Output, is_win_vt100_enabled
+
+        if is_win_vt100_enabled():
+            return cast(
+                Output,
+                Windows10_Output(stdout, default_color_depth=color_depth_from_env),
+            )
+        if is_conemu_ansi():
+            return cast(
+                Output, ConEmuOutput(stdout, default_color_depth=color_depth_from_env)
+            )
+        else:
+            return Win32Output(stdout, default_color_depth=color_depth_from_env)
+    else:
+        from .vt100 import Vt100_Output
+
+        # Stdout is not a TTY? Render as plain text.
+        # This is mostly useful if stdout is redirected to a file, and
+        # `print_formatted_text` is used.
+        if not stdout.isatty():
+            return PlainTextOutput(stdout)
+
+        return Vt100_Output.from_pty(
+            stdout,
+            term=term_from_env,
+            default_color_depth=color_depth_from_env,
+            enable_bell=bell_from_env,
+        )
diff --git a/src/prompt_toolkit/output/flush_stdout.py b/src/prompt_toolkit/output/flush_stdout.py
new file mode 100644
index 0000000..e98d253
--- /dev/null
+++ b/src/prompt_toolkit/output/flush_stdout.py
@@ -0,0 +1,85 @@
+import errno
+import os
+import sys
+from contextlib import contextmanager
+from typing import IO, Iterator, TextIO, cast
+
+__all__ = ["flush_stdout"]
+
+
+def flush_stdout(stdout: TextIO, data: str) -> None:
+    # If the IO object has an `encoding` and `buffer` attribute, it means that
+    # we can access the underlying BinaryIO object and write into it in binary
+    # mode. This is preferred if possible.
+    # NOTE: When used in a Jupyter notebook, don't write binary.
+    #       `ipykernel.iostream.OutStream` has an `encoding` attribute, but not
+    #       a `buffer` attribute, so we can't write binary in it.
+    has_binary_io = hasattr(stdout, "encoding") and hasattr(stdout, "buffer")
+
+    try:
+        # Ensure that `stdout` is made blocking when writing into it.
+        # Otherwise, when uvloop is activated (which makes stdout
+        # non-blocking), and we write big amounts of text, then we get a
+        # `BlockingIOError` here.
+        with _blocking_io(stdout):
+            # (We try to encode ourself, because that way we can replace
+            # characters that don't exist in the character set, avoiding
+            # UnicodeEncodeError crashes. E.g. u'\xb7' does not appear in 'ascii'.)
+            # My Arch Linux installation of july 2015 reported 'ANSI_X3.4-1968'
+            # for sys.stdout.encoding in xterm.
+            if has_binary_io:
+                stdout.buffer.write(data.encode(stdout.encoding or "utf-8", "replace"))
+            else:
+                stdout.write(data)
+
+            stdout.flush()
+    except OSError as e:
+        if e.args and e.args[0] == errno.EINTR:
+            # Interrupted system call. Can happen in case of a window
+            # resize signal. (Just ignore. The resize handler will render
+            # again anyway.)
+            pass
+        elif e.args and e.args[0] == 0:
+            # This can happen when there is a lot of output and the user
+            # sends a KeyboardInterrupt by pressing Control-C. E.g. in
+            # a Python REPL when we execute "while True: print('test')".
+            # (The `ptpython` REPL uses this `Output` class instead of
+            # `stdout` directly -- in order to be network transparent.)
+            # So, just ignore.
+            pass
+        else:
+            raise
+
+
+@contextmanager
+def _blocking_io(io: IO[str]) -> Iterator[None]:
+    """
+    Ensure that the FD for `io` is set to blocking in here.
+    """
+    if sys.platform == "win32":
+        # On Windows, the `os` module doesn't have a `get/set_blocking`
+        # function.
+        yield
+        return
+
+    try:
+        fd = io.fileno()
+        blocking = os.get_blocking(fd)
+    except:  # noqa
+        # Failed somewhere.
+        # `get_blocking` can raise `OSError`.
+        # The io object can raise `AttributeError` when no `fileno()` method is
+        # present if we're not a real file object.
+        blocking = True  # Assume we're good, and don't do anything.
+
+    try:
+        # Make blocking if we weren't blocking yet.
+        if not blocking:
+            os.set_blocking(fd, True)
+
+        yield
+
+    finally:
+        # Restore original blocking mode.
+        if not blocking:
+            os.set_blocking(fd, blocking)
diff --git a/src/prompt_toolkit/output/plain_text.py b/src/prompt_toolkit/output/plain_text.py
new file mode 100644
index 0000000..4360355
--- /dev/null
+++ b/src/prompt_toolkit/output/plain_text.py
@@ -0,0 +1,141 @@
+from typing import List, TextIO
+
+from prompt_toolkit.cursor_shapes import CursorShape
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.styles import Attrs
+
+from .base import Output
+from .color_depth import ColorDepth
+from .flush_stdout import flush_stdout
+
+__all__ = ["PlainTextOutput"]
+
+
+class PlainTextOutput(Output):
+    """
+    Output that won't include any ANSI escape sequences.
+
+    Useful when stdout is not a terminal. Maybe stdout is redirected to a file.
+    In this case, if `print_formatted_text` is used, for instance, we don't
+    want to include formatting.
+
+    (The code is mostly identical to `Vt100_Output`, but without the
+    formatting.)
+    """
+
+    def __init__(self, stdout: TextIO) -> None:
+        assert all(hasattr(stdout, a) for a in ("write", "flush"))
+
+        self.stdout: TextIO = stdout
+        self._buffer: List[str] = []
+
+    def fileno(self) -> int:
+        "There is no sensible default for fileno()."
+        return self.stdout.fileno()
+
+    def encoding(self) -> str:
+        return "utf-8"
+
+    def write(self, data: str) -> None:
+        self._buffer.append(data)
+
+    def write_raw(self, data: str) -> None:
+        self._buffer.append(data)
+
+    def set_title(self, title: str) -> None:
+        pass
+
+    def clear_title(self) -> None:
+        pass
+
+    def flush(self) -> None:
+        if not self._buffer:
+            return
+
+        data = "".join(self._buffer)
+        self._buffer = []
+        flush_stdout(self.stdout, data)
+
+    def erase_screen(self) -> None:
+        pass
+
+    def enter_alternate_screen(self) -> None:
+        pass
+
+    def quit_alternate_screen(self) -> None:
+        pass
+
+    def enable_mouse_support(self) -> None:
+        pass
+
+    def disable_mouse_support(self) -> None:
+        pass
+
+    def erase_end_of_line(self) -> None:
+        pass
+
+    def erase_down(self) -> None:
+        pass
+
+    def reset_attributes(self) -> None:
+        pass
+
+    def set_attributes(self, attrs: Attrs, color_depth: ColorDepth) -> None:
+        pass
+
+    def disable_autowrap(self) -> None:
+        pass
+
+    def enable_autowrap(self) -> None:
+        pass
+
+    def cursor_goto(self, row: int = 0, column: int = 0) -> None:
+        pass
+
+    def cursor_up(self, amount: int) -> None:
+        pass
+
+    def cursor_down(self, amount: int) -> None:
+        self._buffer.append("\n")
+
+    def cursor_forward(self, amount: int) -> None:
+        self._buffer.append(" " * amount)
+
+    def cursor_backward(self, amount: int) -> None:
+        pass
+
+    def hide_cursor(self) -> None:
+        pass
+
+    def show_cursor(self) -> None:
+        pass
+
+    def set_cursor_shape(self, cursor_shape: CursorShape) -> None:
+        pass
+
+    def reset_cursor_shape(self) -> None:
+        pass
+
+    def ask_for_cpr(self) -> None:
+        pass
+
+    def bell(self) -> None:
+        pass
+
+    def enable_bracketed_paste(self) -> None:
+        pass
+
+    def disable_bracketed_paste(self) -> None:
+        pass
+
+    def scroll_buffer_to_prompt(self) -> None:
+        pass
+
+    def get_size(self) -> Size:
+        return Size(rows=40, columns=80)
+
+    def get_rows_below_cursor_position(self) -> int:
+        return 8
+
+    def get_default_color_depth(self) -> ColorDepth:
+        return ColorDepth.DEPTH_1_BIT
diff --git a/src/prompt_toolkit/output/vt100.py b/src/prompt_toolkit/output/vt100.py
new file mode 100644
index 0000000..6fbf068
--- /dev/null
+++ b/src/prompt_toolkit/output/vt100.py
@@ -0,0 +1,758 @@
+"""
+Output for vt100 terminals.
+
+A lot of thanks, regarding outputting of colors, goes to the Pygments project:
+(We don't rely on Pygments anymore, because many things are very custom, and
+everything has been highly optimized.)
+http://pygments.org/
+"""
+import io
+import os
+import sys
+from typing import (
+    Callable,
+    Dict,
+    Hashable,
+    Iterable,
+    List,
+    Optional,
+    Sequence,
+    Set,
+    TextIO,
+    Tuple,
+)
+
+from prompt_toolkit.cursor_shapes import CursorShape
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.output import Output
+from prompt_toolkit.styles import ANSI_COLOR_NAMES, Attrs
+from prompt_toolkit.utils import is_dumb_terminal
+
+from .color_depth import ColorDepth
+from .flush_stdout import flush_stdout
+
+__all__ = [
+    "Vt100_Output",
+]
+
+
+FG_ANSI_COLORS = {
+    "ansidefault": 39,
+    # Low intensity.
+    "ansiblack": 30,
+    "ansired": 31,
+    "ansigreen": 32,
+    "ansiyellow": 33,
+    "ansiblue": 34,
+    "ansimagenta": 35,
+    "ansicyan": 36,
+    "ansigray": 37,
+    # High intensity.
+    "ansibrightblack": 90,
+    "ansibrightred": 91,
+    "ansibrightgreen": 92,
+    "ansibrightyellow": 93,
+    "ansibrightblue": 94,
+    "ansibrightmagenta": 95,
+    "ansibrightcyan": 96,
+    "ansiwhite": 97,
+}
+
+BG_ANSI_COLORS = {
+    "ansidefault": 49,
+    # Low intensity.
+    "ansiblack": 40,
+    "ansired": 41,
+    "ansigreen": 42,
+    "ansiyellow": 43,
+    "ansiblue": 44,
+    "ansimagenta": 45,
+    "ansicyan": 46,
+    "ansigray": 47,
+    # High intensity.
+    "ansibrightblack": 100,
+    "ansibrightred": 101,
+    "ansibrightgreen": 102,
+    "ansibrightyellow": 103,
+    "ansibrightblue": 104,
+    "ansibrightmagenta": 105,
+    "ansibrightcyan": 106,
+    "ansiwhite": 107,
+}
+
+
+ANSI_COLORS_TO_RGB = {
+    "ansidefault": (
+        0x00,
+        0x00,
+        0x00,
+    ),  # Don't use, 'default' doesn't really have a value.
+    "ansiblack": (0x00, 0x00, 0x00),
+    "ansigray": (0xE5, 0xE5, 0xE5),
+    "ansibrightblack": (0x7F, 0x7F, 0x7F),
+    "ansiwhite": (0xFF, 0xFF, 0xFF),
+    # Low intensity.
+    "ansired": (0xCD, 0x00, 0x00),
+    "ansigreen": (0x00, 0xCD, 0x00),
+    "ansiyellow": (0xCD, 0xCD, 0x00),
+    "ansiblue": (0x00, 0x00, 0xCD),
+    "ansimagenta": (0xCD, 0x00, 0xCD),
+    "ansicyan": (0x00, 0xCD, 0xCD),
+    # High intensity.
+    "ansibrightred": (0xFF, 0x00, 0x00),
+    "ansibrightgreen": (0x00, 0xFF, 0x00),
+    "ansibrightyellow": (0xFF, 0xFF, 0x00),
+    "ansibrightblue": (0x00, 0x00, 0xFF),
+    "ansibrightmagenta": (0xFF, 0x00, 0xFF),
+    "ansibrightcyan": (0x00, 0xFF, 0xFF),
+}
+
+
+assert set(FG_ANSI_COLORS) == set(ANSI_COLOR_NAMES)
+assert set(BG_ANSI_COLORS) == set(ANSI_COLOR_NAMES)
+assert set(ANSI_COLORS_TO_RGB) == set(ANSI_COLOR_NAMES)
+
+
+def _get_closest_ansi_color(r: int, g: int, b: int, exclude: Sequence[str] = ()) -> str:
+    """
+    Find closest ANSI color. Return it by name.
+
+    :param r: Red (Between 0 and 255.)
+    :param g: Green (Between 0 and 255.)
+    :param b: Blue (Between 0 and 255.)
+    :param exclude: A tuple of color names to exclude. (E.g. ``('ansired', )``.)
+    """
+    exclude = list(exclude)
+
+    # When we have a bit of saturation, avoid the gray-like colors, otherwise,
+    # too often the distance to the gray color is less.
+    saturation = abs(r - g) + abs(g - b) + abs(b - r)  # Between 0..510
+
+    if saturation > 30:
+        exclude.extend(["ansilightgray", "ansidarkgray", "ansiwhite", "ansiblack"])
+
+    # Take the closest color.
+    # (Thanks to Pygments for this part.)
+    distance = 257 * 257 * 3  # "infinity" (>distance from #000000 to #ffffff)
+    match = "ansidefault"
+
+    for name, (r2, g2, b2) in ANSI_COLORS_TO_RGB.items():
+        if name != "ansidefault" and name not in exclude:
+            d = (r - r2) ** 2 + (g - g2) ** 2 + (b - b2) ** 2
+
+            if d < distance:
+                match = name
+                distance = d
+
+    return match
+
+
+_ColorCodeAndName = Tuple[int, str]
+
+
+class _16ColorCache:
+    """
+    Cache which maps (r, g, b) tuples to 16 ansi colors.
+
+    :param bg: Cache for background colors, instead of foreground.
+    """
+
+    def __init__(self, bg: bool = False) -> None:
+        self.bg = bg
+        self._cache: Dict[Hashable, _ColorCodeAndName] = {}
+
+    def get_code(
+        self, value: Tuple[int, int, int], exclude: Sequence[str] = ()
+    ) -> _ColorCodeAndName:
+        """
+        Return a (ansi_code, ansi_name) tuple. (E.g. ``(44, 'ansiblue')``.) for
+        a given (r,g,b) value.
+        """
+        key: Hashable = (value, tuple(exclude))
+        cache = self._cache
+
+        if key not in cache:
+            cache[key] = self._get(value, exclude)
+
+        return cache[key]
+
+    def _get(
+        self, value: Tuple[int, int, int], exclude: Sequence[str] = ()
+    ) -> _ColorCodeAndName:
+
+        r, g, b = value
+        match = _get_closest_ansi_color(r, g, b, exclude=exclude)
+
+        # Turn color name into code.
+        if self.bg:
+            code = BG_ANSI_COLORS[match]
+        else:
+            code = FG_ANSI_COLORS[match]
+
+        return code, match
+
+
+class _256ColorCache(Dict[Tuple[int, int, int], int]):
+    """
+    Cache which maps (r, g, b) tuples to 256 colors.
+    """
+
+    def __init__(self) -> None:
+        # Build color table.
+        colors: List[Tuple[int, int, int]] = []
+
+        # colors 0..15: 16 basic colors
+        colors.append((0x00, 0x00, 0x00))  # 0
+        colors.append((0xCD, 0x00, 0x00))  # 1
+        colors.append((0x00, 0xCD, 0x00))  # 2
+        colors.append((0xCD, 0xCD, 0x00))  # 3
+        colors.append((0x00, 0x00, 0xEE))  # 4
+        colors.append((0xCD, 0x00, 0xCD))  # 5
+        colors.append((0x00, 0xCD, 0xCD))  # 6
+        colors.append((0xE5, 0xE5, 0xE5))  # 7
+        colors.append((0x7F, 0x7F, 0x7F))  # 8
+        colors.append((0xFF, 0x00, 0x00))  # 9
+        colors.append((0x00, 0xFF, 0x00))  # 10
+        colors.append((0xFF, 0xFF, 0x00))  # 11
+        colors.append((0x5C, 0x5C, 0xFF))  # 12
+        colors.append((0xFF, 0x00, 0xFF))  # 13
+        colors.append((0x00, 0xFF, 0xFF))  # 14
+        colors.append((0xFF, 0xFF, 0xFF))  # 15
+
+        # colors 16..232: the 6x6x6 color cube
+        valuerange = (0x00, 0x5F, 0x87, 0xAF, 0xD7, 0xFF)
+
+        for i in range(217):
+            r = valuerange[(i // 36) % 6]
+            g = valuerange[(i // 6) % 6]
+            b = valuerange[i % 6]
+            colors.append((r, g, b))
+
+        # colors 233..253: grayscale
+        for i in range(1, 22):
+            v = 8 + i * 10
+            colors.append((v, v, v))
+
+        self.colors = colors
+
+    def __missing__(self, value: Tuple[int, int, int]) -> int:
+        r, g, b = value
+
+        # Find closest color.
+        # (Thanks to Pygments for this!)
+        distance = 257 * 257 * 3  # "infinity" (>distance from #000000 to #ffffff)
+        match = 0
+
+        for i, (r2, g2, b2) in enumerate(self.colors):
+            if i >= 16:  # XXX: We ignore the 16 ANSI colors when mapping RGB
+                # to the 256 colors, because these highly depend on
+                # the color scheme of the terminal.
+                d = (r - r2) ** 2 + (g - g2) ** 2 + (b - b2) ** 2
+
+                if d < distance:
+                    match = i
+                    distance = d
+
+        # Turn color name into code.
+        self[value] = match
+        return match
+
+
+_16_fg_colors = _16ColorCache(bg=False)
+_16_bg_colors = _16ColorCache(bg=True)
+_256_colors = _256ColorCache()
+
+
+class _EscapeCodeCache(Dict[Attrs, str]):
+    """
+    Cache for VT100 escape codes. It maps
+    (fgcolor, bgcolor, bold, underline, strike, reverse) tuples to VT100
+    escape sequences.
+
+    :param true_color: When True, use 24bit colors instead of 256 colors.
+    """
+
+    def __init__(self, color_depth: ColorDepth) -> None:
+        self.color_depth = color_depth
+
+    def __missing__(self, attrs: Attrs) -> str:
+        (
+            fgcolor,
+            bgcolor,
+            bold,
+            underline,
+            strike,
+            italic,
+            blink,
+            reverse,
+            hidden,
+        ) = attrs
+        parts: List[str] = []
+
+        parts.extend(self._colors_to_code(fgcolor or "", bgcolor or ""))
+
+        if bold:
+            parts.append("1")
+        if italic:
+            parts.append("3")
+        if blink:
+            parts.append("5")
+        if underline:
+            parts.append("4")
+        if reverse:
+            parts.append("7")
+        if hidden:
+            parts.append("8")
+        if strike:
+            parts.append("9")
+
+        if parts:
+            result = "\x1b[0;" + ";".join(parts) + "m"
+        else:
+            result = "\x1b[0m"
+
+        self[attrs] = result
+        return result
+
+    def _color_name_to_rgb(self, color: str) -> Tuple[int, int, int]:
+        "Turn 'ffffff', into (0xff, 0xff, 0xff)."
+        try:
+            rgb = int(color, 16)
+        except ValueError:
+            raise
+        else:
+            r = (rgb >> 16) & 0xFF
+            g = (rgb >> 8) & 0xFF
+            b = rgb & 0xFF
+            return r, g, b
+
+    def _colors_to_code(self, fg_color: str, bg_color: str) -> Iterable[str]:
+        """
+        Return a tuple with the vt100 values  that represent this color.
+        """
+        # When requesting ANSI colors only, and both fg/bg color were converted
+        # to ANSI, ensure that the foreground and background color are not the
+        # same. (Unless they were explicitly defined to be the same color.)
+        fg_ansi = ""
+
+        def get(color: str, bg: bool) -> List[int]:
+            nonlocal fg_ansi
+
+            table = BG_ANSI_COLORS if bg else FG_ANSI_COLORS
+
+            if not color or self.color_depth == ColorDepth.DEPTH_1_BIT:
+                return []
+
+            # 16 ANSI colors. (Given by name.)
+            elif color in table:
+                return [table[color]]
+
+            # RGB colors. (Defined as 'ffffff'.)
+            else:
+                try:
+                    rgb = self._color_name_to_rgb(color)
+                except ValueError:
+                    return []
+
+                # When only 16 colors are supported, use that.
+                if self.color_depth == ColorDepth.DEPTH_4_BIT:
+                    if bg:  # Background.
+                        if fg_color != bg_color:
+                            exclude = [fg_ansi]
+                        else:
+                            exclude = []
+                        code, name = _16_bg_colors.get_code(rgb, exclude=exclude)
+                        return [code]
+                    else:  # Foreground.
+                        code, name = _16_fg_colors.get_code(rgb)
+                        fg_ansi = name
+                        return [code]
+
+                # True colors. (Only when this feature is enabled.)
+                elif self.color_depth == ColorDepth.DEPTH_24_BIT:
+                    r, g, b = rgb
+                    return [(48 if bg else 38), 2, r, g, b]
+
+                # 256 RGB colors.
+                else:
+                    return [(48 if bg else 38), 5, _256_colors[rgb]]
+
+        result: List[int] = []
+        result.extend(get(fg_color, False))
+        result.extend(get(bg_color, True))
+
+        return map(str, result)
+
+
+def _get_size(fileno: int) -> Tuple[int, int]:
+    """
+    Get the size of this pseudo terminal.
+
+    :param fileno: stdout.fileno()
+    :returns: A (rows, cols) tuple.
+    """
+    size = os.get_terminal_size(fileno)
+    return size.lines, size.columns
+
+
+class Vt100_Output(Output):
+    """
+    :param get_size: A callable which returns the `Size` of the output terminal.
+    :param stdout: Any object with has a `write` and `flush` method + an 'encoding' property.
+    :param term: The terminal environment variable. (xterm, xterm-256color, linux, ...)
+    :param enable_cpr: When `True` (the default), send "cursor position
+        request" escape sequences to the output in order to detect the cursor
+        position. That way, we can properly determine how much space there is
+        available for the UI (especially for drop down menus) to render. The
+        `Renderer` will still try to figure out whether the current terminal
+        does respond to CPR escapes. When `False`, never attempt to send CPR
+        requests.
+    """
+
+    # For the error messages. Only display "Output is not a terminal" once per
+    # file descriptor.
+    _fds_not_a_terminal: Set[int] = set()
+
+    def __init__(
+        self,
+        stdout: TextIO,
+        get_size: Callable[[], Size],
+        term: Optional[str] = None,
+        default_color_depth: Optional[ColorDepth] = None,
+        enable_bell: bool = True,
+        enable_cpr: bool = True,
+    ) -> None:
+
+        assert all(hasattr(stdout, a) for a in ("write", "flush"))
+
+        self._buffer: List[str] = []
+        self.stdout: TextIO = stdout
+        self.default_color_depth = default_color_depth
+        self._get_size = get_size
+        self.term = term
+        self.enable_bell = enable_bell
+        self.enable_cpr = enable_cpr
+
+        # Cache for escape codes.
+        self._escape_code_caches: Dict[ColorDepth, _EscapeCodeCache] = {
+            ColorDepth.DEPTH_1_BIT: _EscapeCodeCache(ColorDepth.DEPTH_1_BIT),
+            ColorDepth.DEPTH_4_BIT: _EscapeCodeCache(ColorDepth.DEPTH_4_BIT),
+            ColorDepth.DEPTH_8_BIT: _EscapeCodeCache(ColorDepth.DEPTH_8_BIT),
+            ColorDepth.DEPTH_24_BIT: _EscapeCodeCache(ColorDepth.DEPTH_24_BIT),
+        }
+
+        # Keep track of whether the cursor shape was ever changed.
+        # (We don't restore the cursor shape if it was never changed - by
+        # default, we don't change them.)
+        self._cursor_shape_changed = False
+
+    @classmethod
+    def from_pty(
+        cls,
+        stdout: TextIO,
+        term: Optional[str] = None,
+        default_color_depth: Optional[ColorDepth] = None,
+        enable_bell: bool = True,
+    ) -> "Vt100_Output":
+        """
+        Create an Output class from a pseudo terminal.
+        (This will take the dimensions by reading the pseudo
+        terminal attributes.)
+        """
+        fd: Optional[int]
+        # Normally, this requires a real TTY device, but people instantiate
+        # this class often during unit tests as well. For convenience, we print
+        # an error message, use standard dimensions, and go on.
+        try:
+            fd = stdout.fileno()
+        except io.UnsupportedOperation:
+            fd = None
+
+        if not stdout.isatty() and (fd is None or fd not in cls._fds_not_a_terminal):
+            msg = "Warning: Output is not a terminal (fd=%r).\n"
+            sys.stderr.write(msg % fd)
+            sys.stderr.flush()
+            if fd is not None:
+                cls._fds_not_a_terminal.add(fd)
+
+        def get_size() -> Size:
+            # If terminal (incorrectly) reports its size as 0, pick a
+            # reasonable default.  See
+            # https://github.com/ipython/ipython/issues/10071
+            rows, columns = (None, None)
+
+            # It is possible that `stdout` is no longer a TTY device at this
+            # point. In that case we get an `OSError` in the ioctl call in
+            # `get_size`. See:
+            # https://github.com/prompt-toolkit/python-prompt-toolkit/pull/1021
+            try:
+                rows, columns = _get_size(stdout.fileno())
+            except OSError:
+                pass
+            return Size(rows=rows or 24, columns=columns or 80)
+
+        return cls(
+            stdout,
+            get_size,
+            term=term,
+            default_color_depth=default_color_depth,
+            enable_bell=enable_bell,
+        )
+
+    def get_size(self) -> Size:
+        return self._get_size()
+
+    def fileno(self) -> int:
+        "Return file descriptor."
+        return self.stdout.fileno()
+
+    def encoding(self) -> str:
+        "Return encoding used for stdout."
+        return self.stdout.encoding
+
+    def write_raw(self, data: str) -> None:
+        """
+        Write raw data to output.
+        """
+        self._buffer.append(data)
+
+    def write(self, data: str) -> None:
+        """
+        Write text to output.
+        (Removes vt100 escape codes. -- used for safely writing text.)
+        """
+        self._buffer.append(data.replace("\x1b", "?"))
+
+    def set_title(self, title: str) -> None:
+        """
+        Set terminal title.
+        """
+        if self.term not in (
+            "linux",
+            "eterm-color",
+        ):  # Not supported by the Linux console.
+            self.write_raw(
+                "\x1b]2;%s\x07" % title.replace("\x1b", "").replace("\x07", "")
+            )
+
+    def clear_title(self) -> None:
+        self.set_title("")
+
+    def erase_screen(self) -> None:
+        """
+        Erases the screen with the background colour and moves the cursor to
+        home.
+        """
+        self.write_raw("\x1b[2J")
+
+    def enter_alternate_screen(self) -> None:
+        self.write_raw("\x1b[?1049h\x1b[H")
+
+    def quit_alternate_screen(self) -> None:
+        self.write_raw("\x1b[?1049l")
+
+    def enable_mouse_support(self) -> None:
+        self.write_raw("\x1b[?1000h")
+
+        # Enable mouse-drag support.
+        self.write_raw("\x1b[?1003h")
+
+        # Enable urxvt Mouse mode. (For terminals that understand this.)
+        self.write_raw("\x1b[?1015h")
+
+        # Also enable Xterm SGR mouse mode. (For terminals that understand this.)
+        self.write_raw("\x1b[?1006h")
+
+        # Note: E.g. lxterminal understands 1000h, but not the urxvt or sgr
+        #       extensions.
+
+    def disable_mouse_support(self) -> None:
+        self.write_raw("\x1b[?1000l")
+        self.write_raw("\x1b[?1015l")
+        self.write_raw("\x1b[?1006l")
+        self.write_raw("\x1b[?1003l")
+
+    def erase_end_of_line(self) -> None:
+        """
+        Erases from the current cursor position to the end of the current line.
+        """
+        self.write_raw("\x1b[K")
+
+    def erase_down(self) -> None:
+        """
+        Erases the screen from the current line down to the bottom of the
+        screen.
+        """
+        self.write_raw("\x1b[J")
+
+    def reset_attributes(self) -> None:
+        self.write_raw("\x1b[0m")
+
+    def set_attributes(self, attrs: Attrs, color_depth: ColorDepth) -> None:
+        """
+        Create new style and output.
+
+        :param attrs: `Attrs` instance.
+        """
+        # Get current depth.
+        escape_code_cache = self._escape_code_caches[color_depth]
+
+        # Write escape character.
+        self.write_raw(escape_code_cache[attrs])
+
+    def disable_autowrap(self) -> None:
+        self.write_raw("\x1b[?7l")
+
+    def enable_autowrap(self) -> None:
+        self.write_raw("\x1b[?7h")
+
+    def enable_bracketed_paste(self) -> None:
+        self.write_raw("\x1b[?2004h")
+
+    def disable_bracketed_paste(self) -> None:
+        self.write_raw("\x1b[?2004l")
+
+    def reset_cursor_key_mode(self) -> None:
+        """
+        For vt100 only.
+        Put the terminal in cursor mode (instead of application mode).
+        """
+        # Put the terminal in cursor mode. (Instead of application mode.)
+        self.write_raw("\x1b[?1l")
+
+    def cursor_goto(self, row: int = 0, column: int = 0) -> None:
+        """
+        Move cursor position.
+        """
+        self.write_raw("\x1b[%i;%iH" % (row, column))
+
+    def cursor_up(self, amount: int) -> None:
+        if amount == 0:
+            pass
+        elif amount == 1:
+            self.write_raw("\x1b[A")
+        else:
+            self.write_raw("\x1b[%iA" % amount)
+
+    def cursor_down(self, amount: int) -> None:
+        if amount == 0:
+            pass
+        elif amount == 1:
+            # Note: Not the same as '\n', '\n' can cause the window content to
+            #       scroll.
+            self.write_raw("\x1b[B")
+        else:
+            self.write_raw("\x1b[%iB" % amount)
+
+    def cursor_forward(self, amount: int) -> None:
+        if amount == 0:
+            pass
+        elif amount == 1:
+            self.write_raw("\x1b[C")
+        else:
+            self.write_raw("\x1b[%iC" % amount)
+
+    def cursor_backward(self, amount: int) -> None:
+        if amount == 0:
+            pass
+        elif amount == 1:
+            self.write_raw("\b")  # '\x1b[D'
+        else:
+            self.write_raw("\x1b[%iD" % amount)
+
+    def hide_cursor(self) -> None:
+        self.write_raw("\x1b[?25l")
+
+    def show_cursor(self) -> None:
+        self.write_raw("\x1b[?12l\x1b[?25h")  # Stop blinking cursor and show.
+
+    def set_cursor_shape(self, cursor_shape: CursorShape) -> None:
+        if cursor_shape == CursorShape._NEVER_CHANGE:
+            return
+
+        self._cursor_shape_changed = True
+        self.write_raw(
+            {
+                CursorShape.BLOCK: "\x1b[2 q",
+                CursorShape.BEAM: "\x1b[6 q",
+                CursorShape.UNDERLINE: "\x1b[4 q",
+                CursorShape.BLINKING_BLOCK: "\x1b[1 q",
+                CursorShape.BLINKING_BEAM: "\x1b[5 q",
+                CursorShape.BLINKING_UNDERLINE: "\x1b[3 q",
+            }.get(cursor_shape, "")
+        )
+
+    def reset_cursor_shape(self) -> None:
+        "Reset cursor shape."
+        # (Only reset cursor shape, if we ever changed it.)
+        if self._cursor_shape_changed:
+            self._cursor_shape_changed = False
+
+            # Reset cursor shape.
+            self.write_raw("\x1b[0 q")
+
+    def flush(self) -> None:
+        """
+        Write to output stream and flush.
+        """
+        if not self._buffer:
+            return
+
+        data = "".join(self._buffer)
+        self._buffer = []
+
+        flush_stdout(self.stdout, data)
+
+    def ask_for_cpr(self) -> None:
+        """
+        Asks for a cursor position report (CPR).
+        """
+        self.write_raw("\x1b[6n")
+        self.flush()
+
+    @property
+    def responds_to_cpr(self) -> bool:
+        if not self.enable_cpr:
+            return False
+
+        # When the input is a tty, we assume that CPR is supported.
+        # It's not when the input is piped from Pexpect.
+        if os.environ.get("PROMPT_TOOLKIT_NO_CPR", "") == "1":
+            return False
+
+        if is_dumb_terminal(self.term):
+            return False
+        try:
+            return self.stdout.isatty()
+        except ValueError:
+            return False  # ValueError: I/O operation on closed file
+
+    def bell(self) -> None:
+        "Sound bell."
+        if self.enable_bell:
+            self.write_raw("\a")
+            self.flush()
+
+    def get_default_color_depth(self) -> ColorDepth:
+        """
+        Return the default color depth for a vt100 terminal, according to the
+        our term value.
+
+        We prefer 256 colors almost always, because this is what most terminals
+        support these days, and is a good default.
+        """
+        if self.default_color_depth is not None:
+            return self.default_color_depth
+
+        term = self.term
+
+        if term is None:
+            return ColorDepth.DEFAULT
+
+        if is_dumb_terminal(term):
+            return ColorDepth.DEPTH_1_BIT
+
+        if term in ("linux", "eterm-color"):
+            return ColorDepth.DEPTH_4_BIT
+
+        return ColorDepth.DEFAULT
diff --git a/src/prompt_toolkit/output/win32.py b/src/prompt_toolkit/output/win32.py
new file mode 100644
index 0000000..1724eae
--- /dev/null
+++ b/src/prompt_toolkit/output/win32.py
@@ -0,0 +1,687 @@
+import sys
+
+assert sys.platform == "win32"
+
+import os
+from ctypes import ArgumentError, byref, c_char, c_long, c_uint, c_ulong, pointer
+
+from ..utils import SPHINX_AUTODOC_RUNNING
+
+# Do not import win32-specific stuff when generating documentation.
+# Otherwise RTD would be unable to generate docs for this module.
+if not SPHINX_AUTODOC_RUNNING:
+    from ctypes import windll
+
+from ctypes.wintypes import DWORD, HANDLE
+from typing import Callable, Dict, List, Optional, TextIO, Tuple, Type, TypeVar, Union
+
+from prompt_toolkit.cursor_shapes import CursorShape
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.styles import ANSI_COLOR_NAMES, Attrs
+from prompt_toolkit.utils import get_cwidth
+from prompt_toolkit.win32_types import (
+    CONSOLE_SCREEN_BUFFER_INFO,
+    COORD,
+    SMALL_RECT,
+    STD_INPUT_HANDLE,
+    STD_OUTPUT_HANDLE,
+)
+
+from .base import Output
+from .color_depth import ColorDepth
+
+__all__ = [
+    "Win32Output",
+]
+
+
+def _coord_byval(coord: COORD) -> c_long:
+    """
+    Turns a COORD object into a c_long.
+    This will cause it to be passed by value instead of by reference. (That is what I think at least.)
+
+    When running ``ptipython`` is run (only with IPython), we often got the following error::
+
+         Error in 'SetConsoleCursorPosition'.
+         ArgumentError("argument 2: <class 'TypeError'>: wrong type",)
+     argument 2: <class 'TypeError'>: wrong type
+
+    It was solved by turning ``COORD`` parameters into a ``c_long`` like this.
+
+    More info: http://msdn.microsoft.com/en-us/library/windows/desktop/ms686025(v=vs.85).aspx
+    """
+    return c_long(coord.Y * 0x10000 | coord.X & 0xFFFF)
+
+
+#: If True: write the output of the renderer also to the following file. This
+#: is very useful for debugging. (e.g.: to see that we don't write more bytes
+#: than required.)
+_DEBUG_RENDER_OUTPUT = False
+_DEBUG_RENDER_OUTPUT_FILENAME = r"prompt-toolkit-windows-output.log"
+
+
+class NoConsoleScreenBufferError(Exception):
+    """
+    Raised when the application is not running inside a Windows Console, but
+    the user tries to instantiate Win32Output.
+    """
+
+    def __init__(self) -> None:
+        # Are we running in 'xterm' on Windows, like git-bash for instance?
+        xterm = "xterm" in os.environ.get("TERM", "")
+
+        if xterm:
+            message = (
+                "Found %s, while expecting a Windows console. "
+                'Maybe try to run this program using "winpty" '
+                "or run it in cmd.exe instead. Or otherwise, "
+                "in case of Cygwin, use the Python executable "
+                "that is compiled for Cygwin." % os.environ["TERM"]
+            )
+        else:
+            message = "No Windows console found. Are you running cmd.exe?"
+        super().__init__(message)
+
+
+_T = TypeVar("_T")
+
+
+class Win32Output(Output):
+    """
+    I/O abstraction for rendering to Windows consoles.
+    (cmd.exe and similar.)
+    """
+
+    def __init__(
+        self,
+        stdout: TextIO,
+        use_complete_width: bool = False,
+        default_color_depth: Optional[ColorDepth] = None,
+    ) -> None:
+        self.use_complete_width = use_complete_width
+        self.default_color_depth = default_color_depth
+
+        self._buffer: List[str] = []
+        self.stdout: TextIO = stdout
+        self.hconsole = HANDLE(windll.kernel32.GetStdHandle(STD_OUTPUT_HANDLE))
+
+        self._in_alternate_screen = False
+        self._hidden = False
+
+        self.color_lookup_table = ColorLookupTable()
+
+        # Remember the default console colors.
+        info = self.get_win32_screen_buffer_info()
+        self.default_attrs = info.wAttributes if info else 15
+
+        if _DEBUG_RENDER_OUTPUT:
+            self.LOG = open(_DEBUG_RENDER_OUTPUT_FILENAME, "ab")
+
+    def fileno(self) -> int:
+        "Return file descriptor."
+        return self.stdout.fileno()
+
+    def encoding(self) -> str:
+        "Return encoding used for stdout."
+        return self.stdout.encoding
+
+    def write(self, data: str) -> None:
+        if self._hidden:
+            data = " " * get_cwidth(data)
+
+        self._buffer.append(data)
+
+    def write_raw(self, data: str) -> None:
+        "For win32, there is no difference between write and write_raw."
+        self.write(data)
+
+    def get_size(self) -> Size:
+        info = self.get_win32_screen_buffer_info()
+
+        # We take the width of the *visible* region as the size. Not the width
+        # of the complete screen buffer. (Unless use_complete_width has been
+        # set.)
+        if self.use_complete_width:
+            width = info.dwSize.X
+        else:
+            width = info.srWindow.Right - info.srWindow.Left
+
+        height = info.srWindow.Bottom - info.srWindow.Top + 1
+
+        # We avoid the right margin, windows will wrap otherwise.
+        maxwidth = info.dwSize.X - 1
+        width = min(maxwidth, width)
+
+        # Create `Size` object.
+        return Size(rows=height, columns=width)
+
+    def _winapi(self, func: Callable[..., _T], *a: object, **kw: object) -> _T:
+        """
+        Flush and call win API function.
+        """
+        self.flush()
+
+        if _DEBUG_RENDER_OUTPUT:
+            self.LOG.write(("%r" % func.__name__).encode("utf-8") + b"\n")
+            self.LOG.write(
+                b"     " + ", ".join(["%r" % i for i in a]).encode("utf-8") + b"\n"
+            )
+            self.LOG.write(
+                b"     "
+                + ", ".join(["%r" % type(i) for i in a]).encode("utf-8")
+                + b"\n"
+            )
+            self.LOG.flush()
+
+        try:
+            return func(*a, **kw)
+        except ArgumentError as e:
+            if _DEBUG_RENDER_OUTPUT:
+                self.LOG.write((f"    Error in {func.__name__!r} {e!r} {e}\n").encode())
+
+            raise
+
+    def get_win32_screen_buffer_info(self) -> CONSOLE_SCREEN_BUFFER_INFO:
+        """
+        Return Screen buffer info.
+        """
+        # NOTE: We don't call the `GetConsoleScreenBufferInfo` API through
+        #     `self._winapi`. Doing so causes Python to crash on certain 64bit
+        #     Python versions. (Reproduced with 64bit Python 2.7.6, on Windows
+        #     10). It is not clear why. Possibly, it has to do with passing
+        #     these objects as an argument, or through *args.
+
+        # The Python documentation contains the following - possibly related - warning:
+        #     ctypes does not support passing unions or structures with
+        #     bit-fields to functions by value. While this may work on 32-bit
+        #     x86, it's not guaranteed by the library to work in the general
+        #     case. Unions and structures with bit-fields should always be
+        #     passed to functions by pointer.
+
+        # Also see:
+        #    - https://github.com/ipython/ipython/issues/10070
+        #    - https://github.com/jonathanslenders/python-prompt-toolkit/issues/406
+        #    - https://github.com/jonathanslenders/python-prompt-toolkit/issues/86
+
+        self.flush()
+        sbinfo = CONSOLE_SCREEN_BUFFER_INFO()
+        success = windll.kernel32.GetConsoleScreenBufferInfo(
+            self.hconsole, byref(sbinfo)
+        )
+
+        # success = self._winapi(windll.kernel32.GetConsoleScreenBufferInfo,
+        #                        self.hconsole, byref(sbinfo))
+
+        if success:
+            return sbinfo
+        else:
+            raise NoConsoleScreenBufferError
+
+    def set_title(self, title: str) -> None:
+        """
+        Set terminal title.
+        """
+        self._winapi(windll.kernel32.SetConsoleTitleW, title)
+
+    def clear_title(self) -> None:
+        self._winapi(windll.kernel32.SetConsoleTitleW, "")
+
+    def erase_screen(self) -> None:
+        start = COORD(0, 0)
+        sbinfo = self.get_win32_screen_buffer_info()
+        length = sbinfo.dwSize.X * sbinfo.dwSize.Y
+
+        self.cursor_goto(row=0, column=0)
+        self._erase(start, length)
+
+    def erase_down(self) -> None:
+        sbinfo = self.get_win32_screen_buffer_info()
+        size = sbinfo.dwSize
+
+        start = sbinfo.dwCursorPosition
+        length = (size.X - size.X) + size.X * (size.Y - sbinfo.dwCursorPosition.Y)
+
+        self._erase(start, length)
+
+    def erase_end_of_line(self) -> None:
+        """"""
+        sbinfo = self.get_win32_screen_buffer_info()
+        start = sbinfo.dwCursorPosition
+        length = sbinfo.dwSize.X - sbinfo.dwCursorPosition.X
+
+        self._erase(start, length)
+
+    def _erase(self, start: COORD, length: int) -> None:
+        chars_written = c_ulong()
+
+        self._winapi(
+            windll.kernel32.FillConsoleOutputCharacterA,
+            self.hconsole,
+            c_char(b" "),
+            DWORD(length),
+            _coord_byval(start),
+            byref(chars_written),
+        )
+
+        # Reset attributes.
+        sbinfo = self.get_win32_screen_buffer_info()
+        self._winapi(
+            windll.kernel32.FillConsoleOutputAttribute,
+            self.hconsole,
+            sbinfo.wAttributes,
+            length,
+            _coord_byval(start),
+            byref(chars_written),
+        )
+
+    def reset_attributes(self) -> None:
+        "Reset the console foreground/background color."
+        self._winapi(
+            windll.kernel32.SetConsoleTextAttribute, self.hconsole, self.default_attrs
+        )
+        self._hidden = False
+
+    def set_attributes(self, attrs: Attrs, color_depth: ColorDepth) -> None:
+        (
+            fgcolor,
+            bgcolor,
+            bold,
+            underline,
+            strike,
+            italic,
+            blink,
+            reverse,
+            hidden,
+        ) = attrs
+        self._hidden = bool(hidden)
+
+        # Start from the default attributes.
+        win_attrs: int = self.default_attrs
+
+        if color_depth != ColorDepth.DEPTH_1_BIT:
+            # Override the last four bits: foreground color.
+            if fgcolor:
+                win_attrs = win_attrs & ~0xF
+                win_attrs |= self.color_lookup_table.lookup_fg_color(fgcolor)
+
+            # Override the next four bits: background color.
+            if bgcolor:
+                win_attrs = win_attrs & ~0xF0
+                win_attrs |= self.color_lookup_table.lookup_bg_color(bgcolor)
+
+        # Reverse: swap these four bits groups.
+        if reverse:
+            win_attrs = (
+                (win_attrs & ~0xFF)
+                | ((win_attrs & 0xF) << 4)
+                | ((win_attrs & 0xF0) >> 4)
+            )
+
+        self._winapi(windll.kernel32.SetConsoleTextAttribute, self.hconsole, win_attrs)
+
+    def disable_autowrap(self) -> None:
+        # Not supported by Windows.
+        pass
+
+    def enable_autowrap(self) -> None:
+        # Not supported by Windows.
+        pass
+
+    def cursor_goto(self, row: int = 0, column: int = 0) -> None:
+        pos = COORD(X=column, Y=row)
+        self._winapi(
+            windll.kernel32.SetConsoleCursorPosition, self.hconsole, _coord_byval(pos)
+        )
+
+    def cursor_up(self, amount: int) -> None:
+        sr = self.get_win32_screen_buffer_info().dwCursorPosition
+        pos = COORD(X=sr.X, Y=sr.Y - amount)
+        self._winapi(
+            windll.kernel32.SetConsoleCursorPosition, self.hconsole, _coord_byval(pos)
+        )
+
+    def cursor_down(self, amount: int) -> None:
+        self.cursor_up(-amount)
+
+    def cursor_forward(self, amount: int) -> None:
+        sr = self.get_win32_screen_buffer_info().dwCursorPosition
+        #        assert sr.X + amount >= 0, 'Negative cursor position: x=%r amount=%r' % (sr.X, amount)
+
+        pos = COORD(X=max(0, sr.X + amount), Y=sr.Y)
+        self._winapi(
+            windll.kernel32.SetConsoleCursorPosition, self.hconsole, _coord_byval(pos)
+        )
+
+    def cursor_backward(self, amount: int) -> None:
+        self.cursor_forward(-amount)
+
+    def flush(self) -> None:
+        """
+        Write to output stream and flush.
+        """
+        if not self._buffer:
+            # Only flush stdout buffer. (It could be that Python still has
+            # something in its buffer. -- We want to be sure to print that in
+            # the correct color.)
+            self.stdout.flush()
+            return
+
+        data = "".join(self._buffer)
+
+        if _DEBUG_RENDER_OUTPUT:
+            self.LOG.write(("%r" % data).encode("utf-8") + b"\n")
+            self.LOG.flush()
+
+        # Print characters one by one. This appears to be the best solution
+        # in oder to avoid traces of vertical lines when the completion
+        # menu disappears.
+        for b in data:
+            written = DWORD()
+
+            retval = windll.kernel32.WriteConsoleW(
+                self.hconsole, b, 1, byref(written), None
+            )
+            assert retval != 0
+
+        self._buffer = []
+
+    def get_rows_below_cursor_position(self) -> int:
+        info = self.get_win32_screen_buffer_info()
+        return info.srWindow.Bottom - info.dwCursorPosition.Y + 1
+
+    def scroll_buffer_to_prompt(self) -> None:
+        """
+        To be called before drawing the prompt. This should scroll the console
+        to left, with the cursor at the bottom (if possible).
+        """
+        # Get current window size
+        info = self.get_win32_screen_buffer_info()
+        sr = info.srWindow
+        cursor_pos = info.dwCursorPosition
+
+        result = SMALL_RECT()
+
+        # Scroll to the left.
+        result.Left = 0
+        result.Right = sr.Right - sr.Left
+
+        # Scroll vertical
+        win_height = sr.Bottom - sr.Top
+        if 0 < sr.Bottom - cursor_pos.Y < win_height - 1:
+            # no vertical scroll if cursor already on the screen
+            result.Bottom = sr.Bottom
+        else:
+            result.Bottom = max(win_height, cursor_pos.Y)
+        result.Top = result.Bottom - win_height
+
+        # Scroll API
+        self._winapi(
+            windll.kernel32.SetConsoleWindowInfo, self.hconsole, True, byref(result)
+        )
+
+    def enter_alternate_screen(self) -> None:
+        """
+        Go to alternate screen buffer.
+        """
+        if not self._in_alternate_screen:
+            GENERIC_READ = 0x80000000
+            GENERIC_WRITE = 0x40000000
+
+            # Create a new console buffer and activate that one.
+            handle = HANDLE(
+                self._winapi(
+                    windll.kernel32.CreateConsoleScreenBuffer,
+                    GENERIC_READ | GENERIC_WRITE,
+                    DWORD(0),
+                    None,
+                    DWORD(1),
+                    None,
+                )
+            )
+
+            self._winapi(windll.kernel32.SetConsoleActiveScreenBuffer, handle)
+            self.hconsole = handle
+            self._in_alternate_screen = True
+
+    def quit_alternate_screen(self) -> None:
+        """
+        Make stdout again the active buffer.
+        """
+        if self._in_alternate_screen:
+            stdout = HANDLE(
+                self._winapi(windll.kernel32.GetStdHandle, STD_OUTPUT_HANDLE)
+            )
+            self._winapi(windll.kernel32.SetConsoleActiveScreenBuffer, stdout)
+            self._winapi(windll.kernel32.CloseHandle, self.hconsole)
+            self.hconsole = stdout
+            self._in_alternate_screen = False
+
+    def enable_mouse_support(self) -> None:
+        ENABLE_MOUSE_INPUT = 0x10
+
+        # This `ENABLE_QUICK_EDIT_MODE` flag needs to be cleared for mouse
+        # support to work, but it's possible that it was already cleared
+        # before.
+        ENABLE_QUICK_EDIT_MODE = 0x0040
+
+        handle = HANDLE(windll.kernel32.GetStdHandle(STD_INPUT_HANDLE))
+
+        original_mode = DWORD()
+        self._winapi(windll.kernel32.GetConsoleMode, handle, pointer(original_mode))
+        self._winapi(
+            windll.kernel32.SetConsoleMode,
+            handle,
+            (original_mode.value | ENABLE_MOUSE_INPUT) & ~ENABLE_QUICK_EDIT_MODE,
+        )
+
+    def disable_mouse_support(self) -> None:
+        ENABLE_MOUSE_INPUT = 0x10
+        handle = HANDLE(windll.kernel32.GetStdHandle(STD_INPUT_HANDLE))
+
+        original_mode = DWORD()
+        self._winapi(windll.kernel32.GetConsoleMode, handle, pointer(original_mode))
+        self._winapi(
+            windll.kernel32.SetConsoleMode,
+            handle,
+            original_mode.value & ~ENABLE_MOUSE_INPUT,
+        )
+
+    def hide_cursor(self) -> None:
+        pass
+
+    def show_cursor(self) -> None:
+        pass
+
+    def set_cursor_shape(self, cursor_shape: CursorShape) -> None:
+        pass
+
+    def reset_cursor_shape(self) -> None:
+        pass
+
+    @classmethod
+    def win32_refresh_window(cls) -> None:
+        """
+        Call win32 API to refresh the whole Window.
+
+        This is sometimes necessary when the application paints background
+        for completion menus. When the menu disappears, it leaves traces due
+        to a bug in the Windows Console. Sending a repaint request solves it.
+        """
+        # Get console handle
+        handle = HANDLE(windll.kernel32.GetConsoleWindow())
+
+        RDW_INVALIDATE = 0x0001
+        windll.user32.RedrawWindow(handle, None, None, c_uint(RDW_INVALIDATE))
+
+    def get_default_color_depth(self) -> ColorDepth:
+        """
+        Return the default color depth for a windows terminal.
+
+        Contrary to the Vt100 implementation, this doesn't depend on a $TERM
+        variable.
+        """
+        if self.default_color_depth is not None:
+            return self.default_color_depth
+
+        # For now, by default, always use 4 bit color on Windows 10 by default,
+        # even when vt100 escape sequences with
+        # ENABLE_VIRTUAL_TERMINAL_PROCESSING are supported. We don't have a
+        # reliable way yet to know whether our console supports true color or
+        # only 4-bit.
+        return ColorDepth.DEPTH_4_BIT
+
+
+class FOREGROUND_COLOR:
+    BLACK = 0x0000
+    BLUE = 0x0001
+    GREEN = 0x0002
+    CYAN = 0x0003
+    RED = 0x0004
+    MAGENTA = 0x0005
+    YELLOW = 0x0006
+    GRAY = 0x0007
+    INTENSITY = 0x0008  # Foreground color is intensified.
+
+
+class BACKGROUND_COLOR:
+    BLACK = 0x0000
+    BLUE = 0x0010
+    GREEN = 0x0020
+    CYAN = 0x0030
+    RED = 0x0040
+    MAGENTA = 0x0050
+    YELLOW = 0x0060
+    GRAY = 0x0070
+    INTENSITY = 0x0080  # Background color is intensified.
+
+
+def _create_ansi_color_dict(
+    color_cls: Union[Type[FOREGROUND_COLOR], Type[BACKGROUND_COLOR]]
+) -> Dict[str, int]:
+    "Create a table that maps the 16 named ansi colors to their Windows code."
+    return {
+        "ansidefault": color_cls.BLACK,
+        "ansiblack": color_cls.BLACK,
+        "ansigray": color_cls.GRAY,
+        "ansibrightblack": color_cls.BLACK | color_cls.INTENSITY,
+        "ansiwhite": color_cls.GRAY | color_cls.INTENSITY,
+        # Low intensity.
+        "ansired": color_cls.RED,
+        "ansigreen": color_cls.GREEN,
+        "ansiyellow": color_cls.YELLOW,
+        "ansiblue": color_cls.BLUE,
+        "ansimagenta": color_cls.MAGENTA,
+        "ansicyan": color_cls.CYAN,
+        # High intensity.
+        "ansibrightred": color_cls.RED | color_cls.INTENSITY,
+        "ansibrightgreen": color_cls.GREEN | color_cls.INTENSITY,
+        "ansibrightyellow": color_cls.YELLOW | color_cls.INTENSITY,
+        "ansibrightblue": color_cls.BLUE | color_cls.INTENSITY,
+        "ansibrightmagenta": color_cls.MAGENTA | color_cls.INTENSITY,
+        "ansibrightcyan": color_cls.CYAN | color_cls.INTENSITY,
+    }
+
+
+FG_ANSI_COLORS = _create_ansi_color_dict(FOREGROUND_COLOR)
+BG_ANSI_COLORS = _create_ansi_color_dict(BACKGROUND_COLOR)
+
+assert set(FG_ANSI_COLORS) == set(ANSI_COLOR_NAMES)
+assert set(BG_ANSI_COLORS) == set(ANSI_COLOR_NAMES)
+
+
+class ColorLookupTable:
+    """
+    Inspired by pygments/formatters/terminal256.py
+    """
+
+    def __init__(self) -> None:
+        self._win32_colors = self._build_color_table()
+
+        # Cache (map color string to foreground and background code).
+        self.best_match: Dict[str, Tuple[int, int]] = {}
+
+    @staticmethod
+    def _build_color_table() -> List[Tuple[int, int, int, int, int]]:
+        """
+        Build an RGB-to-256 color conversion table
+        """
+        FG = FOREGROUND_COLOR
+        BG = BACKGROUND_COLOR
+
+        return [
+            (0x00, 0x00, 0x00, FG.BLACK, BG.BLACK),
+            (0x00, 0x00, 0xAA, FG.BLUE, BG.BLUE),
+            (0x00, 0xAA, 0x00, FG.GREEN, BG.GREEN),
+            (0x00, 0xAA, 0xAA, FG.CYAN, BG.CYAN),
+            (0xAA, 0x00, 0x00, FG.RED, BG.RED),
+            (0xAA, 0x00, 0xAA, FG.MAGENTA, BG.MAGENTA),
+            (0xAA, 0xAA, 0x00, FG.YELLOW, BG.YELLOW),
+            (0x88, 0x88, 0x88, FG.GRAY, BG.GRAY),
+            (0x44, 0x44, 0xFF, FG.BLUE | FG.INTENSITY, BG.BLUE | BG.INTENSITY),
+            (0x44, 0xFF, 0x44, FG.GREEN | FG.INTENSITY, BG.GREEN | BG.INTENSITY),
+            (0x44, 0xFF, 0xFF, FG.CYAN | FG.INTENSITY, BG.CYAN | BG.INTENSITY),
+            (0xFF, 0x44, 0x44, FG.RED | FG.INTENSITY, BG.RED | BG.INTENSITY),
+            (0xFF, 0x44, 0xFF, FG.MAGENTA | FG.INTENSITY, BG.MAGENTA | BG.INTENSITY),
+            (0xFF, 0xFF, 0x44, FG.YELLOW | FG.INTENSITY, BG.YELLOW | BG.INTENSITY),
+            (0x44, 0x44, 0x44, FG.BLACK | FG.INTENSITY, BG.BLACK | BG.INTENSITY),
+            (0xFF, 0xFF, 0xFF, FG.GRAY | FG.INTENSITY, BG.GRAY | BG.INTENSITY),
+        ]
+
+    def _closest_color(self, r: int, g: int, b: int) -> Tuple[int, int]:
+        distance = 257 * 257 * 3  # "infinity" (>distance from #000000 to #ffffff)
+        fg_match = 0
+        bg_match = 0
+
+        for r_, g_, b_, fg_, bg_ in self._win32_colors:
+            rd = r - r_
+            gd = g - g_
+            bd = b - b_
+
+            d = rd * rd + gd * gd + bd * bd
+
+            if d < distance:
+                fg_match = fg_
+                bg_match = bg_
+                distance = d
+        return fg_match, bg_match
+
+    def _color_indexes(self, color: str) -> Tuple[int, int]:
+        indexes = self.best_match.get(color, None)
+        if indexes is None:
+            try:
+                rgb = int(str(color), 16)
+            except ValueError:
+                rgb = 0
+
+            r = (rgb >> 16) & 0xFF
+            g = (rgb >> 8) & 0xFF
+            b = rgb & 0xFF
+            indexes = self._closest_color(r, g, b)
+            self.best_match[color] = indexes
+        return indexes
+
+    def lookup_fg_color(self, fg_color: str) -> int:
+        """
+        Return the color for use in the
+        `windll.kernel32.SetConsoleTextAttribute` API call.
+
+        :param fg_color: Foreground as text. E.g. 'ffffff' or 'red'
+        """
+        # Foreground.
+        if fg_color in FG_ANSI_COLORS:
+            return FG_ANSI_COLORS[fg_color]
+        else:
+            return self._color_indexes(fg_color)[0]
+
+    def lookup_bg_color(self, bg_color: str) -> int:
+        """
+        Return the color for use in the
+        `windll.kernel32.SetConsoleTextAttribute` API call.
+
+        :param bg_color: Background as text. E.g. 'ffffff' or 'red'
+        """
+        # Background.
+        if bg_color in BG_ANSI_COLORS:
+            return BG_ANSI_COLORS[bg_color]
+        else:
+            return self._color_indexes(bg_color)[1]
diff --git a/src/prompt_toolkit/output/windows10.py b/src/prompt_toolkit/output/windows10.py
new file mode 100644
index 0000000..d5d55f1
--- /dev/null
+++ b/src/prompt_toolkit/output/windows10.py
@@ -0,0 +1,107 @@
+import sys
+
+assert sys.platform == "win32"
+
+from ctypes import byref, windll
+from ctypes.wintypes import DWORD, HANDLE
+from typing import Any, Optional, TextIO
+
+from prompt_toolkit.data_structures import Size
+from prompt_toolkit.win32_types import STD_OUTPUT_HANDLE
+
+from .base import Output
+from .color_depth import ColorDepth
+from .vt100 import Vt100_Output
+from .win32 import Win32Output
+
+__all__ = [
+    "Windows10_Output",
+]
+
+# See: https://msdn.microsoft.com/pl-pl/library/windows/desktop/ms686033(v=vs.85).aspx
+ENABLE_PROCESSED_INPUT = 0x0001
+ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x0004
+
+
+class Windows10_Output:
+    """
+    Windows 10 output abstraction. This enables and uses vt100 escape sequences.
+    """
+
+    def __init__(
+        self, stdout: TextIO, default_color_depth: Optional[ColorDepth] = None
+    ) -> None:
+        self.win32_output = Win32Output(stdout, default_color_depth=default_color_depth)
+        self.vt100_output = Vt100_Output(
+            stdout, lambda: Size(0, 0), default_color_depth=default_color_depth
+        )
+        self._hconsole = HANDLE(windll.kernel32.GetStdHandle(STD_OUTPUT_HANDLE))
+
+    def flush(self) -> None:
+        """
+        Write to output stream and flush.
+        """
+        original_mode = DWORD(0)
+
+        # Remember the previous console mode.
+        windll.kernel32.GetConsoleMode(self._hconsole, byref(original_mode))
+
+        # Enable processing of vt100 sequences.
+        windll.kernel32.SetConsoleMode(
+            self._hconsole,
+            DWORD(ENABLE_PROCESSED_INPUT | ENABLE_VIRTUAL_TERMINAL_PROCESSING),
+        )
+
+        try:
+            self.vt100_output.flush()
+        finally:
+            # Restore console mode.
+            windll.kernel32.SetConsoleMode(self._hconsole, original_mode)
+
+    @property
+    def responds_to_cpr(self) -> bool:
+        return False  # We don't need this on Windows.
+
+    def __getattr__(self, name: str) -> Any:
+        if name in (
+            "get_size",
+            "get_rows_below_cursor_position",
+            "enable_mouse_support",
+            "disable_mouse_support",
+            "scroll_buffer_to_prompt",
+            "get_win32_screen_buffer_info",
+            "enable_bracketed_paste",
+            "disable_bracketed_paste",
+            "get_default_color_depth",
+        ):
+            return getattr(self.win32_output, name)
+        else:
+            return getattr(self.vt100_output, name)
+
+
+Output.register(Windows10_Output)
+
+
+def is_win_vt100_enabled() -> bool:
+    """
+    Returns True when we're running Windows and VT100 escape sequences are
+    supported.
+    """
+    if sys.platform != "win32":
+        return False
+
+    hconsole = HANDLE(windll.kernel32.GetStdHandle(STD_OUTPUT_HANDLE))
+
+    # Get original console mode.
+    original_mode = DWORD(0)
+    windll.kernel32.GetConsoleMode(hconsole, byref(original_mode))
+
+    try:
+        # Try to enable VT100 sequences.
+        result: int = windll.kernel32.SetConsoleMode(
+            hconsole, DWORD(ENABLE_PROCESSED_INPUT | ENABLE_VIRTUAL_TERMINAL_PROCESSING)
+        )
+
+        return result == 1
+    finally:
+        windll.kernel32.SetConsoleMode(hconsole, original_mode)
diff --git a/src/prompt_toolkit/patch_stdout.py b/src/prompt_toolkit/patch_stdout.py
new file mode 100644
index 0000000..0abbcdb
--- /dev/null
+++ b/src/prompt_toolkit/patch_stdout.py
@@ -0,0 +1,288 @@
+"""
+patch_stdout
+============
+
+This implements a context manager that ensures that print statements within
+it won't destroy the user interface. The context manager will replace
+`sys.stdout` by something that draws the output above the current prompt,
+rather than overwriting the UI.
+
+Usage::
+
+    with patch_stdout(application):
+        ...
+        application.run()
+        ...
+
+Multiple applications can run in the body of the context manager, one after the
+other.
+"""
+import asyncio
+import queue
+import sys
+import threading
+import time
+from contextlib import contextmanager
+from typing import Generator, List, Optional, TextIO, Union, cast
+
+from .application import get_app_session, run_in_terminal
+from .output import Output
+
+__all__ = [
+    "patch_stdout",
+    "StdoutProxy",
+]
+
+
+@contextmanager
+def patch_stdout(raw: bool = False) -> Generator[None, None, None]:
+    """
+    Replace `sys.stdout` by an :class:`_StdoutProxy` instance.
+
+    Writing to this proxy will make sure that the text appears above the
+    prompt, and that it doesn't destroy the output from the renderer.  If no
+    application is curring, the behaviour should be identical to writing to
+    `sys.stdout` directly.
+
+    Warning: If a new event loop is installed using `asyncio.set_event_loop()`,
+        then make sure that the context manager is applied after the event loop
+        is changed. Printing to stdout will be scheduled in the event loop
+        that's active when the context manager is created.
+
+    :param raw: (`bool`) When True, vt100 terminal escape sequences are not
+                removed/escaped.
+    """
+    with StdoutProxy(raw=raw) as proxy:
+        original_stdout = sys.stdout
+        original_stderr = sys.stderr
+
+        # Enter.
+        sys.stdout = cast(TextIO, proxy)
+        sys.stderr = cast(TextIO, proxy)
+
+        try:
+            yield
+        finally:
+            sys.stdout = original_stdout
+            sys.stderr = original_stderr
+
+
+class _Done:
+    "Sentinel value for stopping the stdout proxy."
+
+
+class StdoutProxy:
+    """
+    File-like object, which prints everything written to it, output above the
+    current application/prompt. This class is compatible with other file
+    objects and can be used as a drop-in replacement for `sys.stdout` or can
+    for instance be passed to `logging.StreamHandler`.
+
+    The current application, above which we print, is determined by looking
+    what application currently runs in the `AppSession` that is active during
+    the creation of this instance.
+
+    This class can be used as a context manager.
+
+    In order to avoid having to repaint the prompt continuously for every
+    little write, a short delay of `sleep_between_writes` seconds will be added
+    between writes in order to bundle many smaller writes in a short timespan.
+    """
+
+    def __init__(
+        self,
+        sleep_between_writes: float = 0.2,
+        raw: bool = False,
+    ) -> None:
+
+        self.sleep_between_writes = sleep_between_writes
+        self.raw = raw
+
+        self._lock = threading.RLock()
+        self._buffer: List[str] = []
+
+        # Keep track of the curret app session.
+        self.app_session = get_app_session()
+
+        # See what output is active *right now*. We should do it at this point,
+        # before this `StdoutProxy` instance is possibly assigned to `sys.stdout`.
+        # Otherwise, if `patch_stdout` is used, and no `Output` instance has
+        # been created, then the default output creation code will see this
+        # proxy object as `sys.stdout`, and get in a recursive loop trying to
+        # access `StdoutProxy.isatty()` which will again retrieve the output.
+        self._output: Output = self.app_session.output
+
+        # Flush thread
+        self._flush_queue: queue.Queue[Union[str, _Done]] = queue.Queue()
+        self._flush_thread = self._start_write_thread()
+        self.closed = False
+
+    def __enter__(self) -> "StdoutProxy":
+        return self
+
+    def __exit__(self, *args: object) -> None:
+        self.close()
+
+    def close(self) -> None:
+        """
+        Stop `StdoutProxy` proxy.
+
+        This will terminate the write thread, make sure everything is flushed
+        and wait for the write thread to finish.
+        """
+        if not self.closed:
+            self._flush_queue.put(_Done())
+            self._flush_thread.join()
+            self.closed = True
+
+    def _start_write_thread(self) -> threading.Thread:
+        thread = threading.Thread(
+            target=self._write_thread,
+            name="patch-stdout-flush-thread",
+            daemon=True,
+        )
+        thread.start()
+        return thread
+
+    def _write_thread(self) -> None:
+        done = False
+
+        while not done:
+            item = self._flush_queue.get()
+
+            if isinstance(item, _Done):
+                break
+
+            # Don't bother calling when we got an empty string.
+            if not item:
+                continue
+
+            text = []
+            text.append(item)
+
+            # Read the rest of the queue if more data was queued up.
+            while True:
+                try:
+                    item = self._flush_queue.get_nowait()
+                except queue.Empty:
+                    break
+                else:
+                    if isinstance(item, _Done):
+                        done = True
+                    else:
+                        text.append(item)
+
+            app_loop = self._get_app_loop()
+            self._write_and_flush(app_loop, "".join(text))
+
+            # If an application was running that requires repainting, then wait
+            # for a very short time, in order to bundle actual writes and avoid
+            # having to repaint to often.
+            if app_loop is not None:
+                time.sleep(self.sleep_between_writes)
+
+    def _get_app_loop(self) -> Optional[asyncio.AbstractEventLoop]:
+        """
+        Return the event loop for the application currently running in our
+        `AppSession`.
+        """
+        app = self.app_session.app
+
+        if app is None:
+            return None
+
+        return app.loop
+
+    def _write_and_flush(
+        self, loop: Optional[asyncio.AbstractEventLoop], text: str
+    ) -> None:
+        """
+        Write the given text to stdout and flush.
+        If an application is running, use `run_in_terminal`.
+        """
+
+        def write_and_flush() -> None:
+            if self.raw:
+                self._output.write_raw(text)
+            else:
+                self._output.write(text)
+
+            self._output.flush()
+
+        def write_and_flush_in_loop() -> None:
+            # If an application is running, use `run_in_terminal`, otherwise
+            # call it directly.
+            run_in_terminal(write_and_flush, in_executor=False)
+
+        if loop is None:
+            # No loop, write immediately.
+            write_and_flush()
+        else:
+            # Make sure `write_and_flush` is executed *in* the event loop, not
+            # in another thread.
+            loop.call_soon_threadsafe(write_and_flush_in_loop)
+
+    def _write(self, data: str) -> None:
+        """
+        Note: print()-statements cause to multiple write calls.
+              (write('line') and write('\n')). Of course we don't want to call
+              `run_in_terminal` for every individual call, because that's too
+              expensive, and as long as the newline hasn't been written, the
+              text itself is again overwritten by the rendering of the input
+              command line. Therefor, we have a little buffer which holds the
+              text until a newline is written to stdout.
+        """
+        if "\n" in data:
+            # When there is a newline in the data, write everything before the
+            # newline, including the newline itself.
+            before, after = data.rsplit("\n", 1)
+            to_write = self._buffer + [before, "\n"]
+            self._buffer = [after]
+
+            text = "".join(to_write)
+            self._flush_queue.put(text)
+        else:
+            # Otherwise, cache in buffer.
+            self._buffer.append(data)
+
+    def _flush(self) -> None:
+        text = "".join(self._buffer)
+        self._buffer = []
+        self._flush_queue.put(text)
+
+    def write(self, data: str) -> int:
+        with self._lock:
+            self._write(data)
+
+        return len(data)  # Pretend everything was written.
+
+    def flush(self) -> None:
+        """
+        Flush buffered output.
+        """
+        with self._lock:
+            self._flush()
+
+    @property
+    def original_stdout(self) -> TextIO:
+        return self._output.stdout or sys.__stdout__
+
+    # Attributes for compatibility with sys.__stdout__:
+
+    def fileno(self) -> int:
+        return self._output.fileno()
+
+    def isatty(self) -> bool:
+        stdout = self._output.stdout
+        if stdout is None:
+            return False
+
+        return stdout.isatty()
+
+    @property
+    def encoding(self) -> str:
+        return self._output.encoding()
+
+    @property
+    def errors(self) -> str:
+        return "strict"
diff --git a/src/prompt_toolkit/py.typed b/src/prompt_toolkit/py.typed
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/prompt_toolkit/py.typed
diff --git a/src/prompt_toolkit/renderer.py b/src/prompt_toolkit/renderer.py
new file mode 100644
index 0000000..d9bb171
--- /dev/null
+++ b/src/prompt_toolkit/renderer.py
@@ -0,0 +1,813 @@
+"""
+Renders the command line on the console.
+(Redraws parts of the input line that were changed.)
+"""
+from asyncio import FIRST_COMPLETED, Future, ensure_future, sleep, wait
+from collections import deque
+from enum import Enum
+from typing import TYPE_CHECKING, Any, Callable, Deque, Dict, Hashable, Optional, Tuple
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.cursor_shapes import CursorShape
+from prompt_toolkit.data_structures import Point, Size
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.formatted_text import AnyFormattedText, to_formatted_text
+from prompt_toolkit.layout.mouse_handlers import MouseHandlers
+from prompt_toolkit.layout.screen import Char, Screen, WritePosition
+from prompt_toolkit.output import ColorDepth, Output
+from prompt_toolkit.styles import (
+    Attrs,
+    BaseStyle,
+    DummyStyleTransformation,
+    StyleTransformation,
+)
+
+if TYPE_CHECKING:
+    from prompt_toolkit.application import Application
+    from prompt_toolkit.layout.layout import Layout
+
+
+__all__ = [
+    "Renderer",
+    "print_formatted_text",
+]
+
+
+def _output_screen_diff(
+    app: "Application[Any]",
+    output: Output,
+    screen: Screen,
+    current_pos: Point,
+    color_depth: ColorDepth,
+    previous_screen: Optional[Screen],
+    last_style: Optional[str],
+    is_done: bool,  # XXX: drop is_done
+    full_screen: bool,
+    attrs_for_style_string: "_StyleStringToAttrsCache",
+    style_string_has_style: "_StyleStringHasStyleCache",
+    size: Size,
+    previous_width: int,
+) -> Tuple[Point, Optional[str]]:
+    """
+    Render the diff between this screen and the previous screen.
+
+    This takes two `Screen` instances. The one that represents the output like
+    it was during the last rendering and one that represents the current
+    output raster. Looking at these two `Screen` instances, this function will
+    render the difference by calling the appropriate methods of the `Output`
+    object that only paint the changes to the terminal.
+
+    This is some performance-critical code which is heavily optimized.
+    Don't change things without profiling first.
+
+    :param current_pos: Current cursor position.
+    :param last_style: The style string, used for drawing the last drawn
+        character.  (Color/attributes.)
+    :param attrs_for_style_string: :class:`._StyleStringToAttrsCache` instance.
+    :param width: The width of the terminal.
+    :param previous_width: The width of the terminal during the last rendering.
+    """
+    width, height = size.columns, size.rows
+
+    #: Variable for capturing the output.
+    write = output.write
+    write_raw = output.write_raw
+
+    # Create locals for the most used output methods.
+    # (Save expensive attribute lookups.)
+    _output_set_attributes = output.set_attributes
+    _output_reset_attributes = output.reset_attributes
+    _output_cursor_forward = output.cursor_forward
+    _output_cursor_up = output.cursor_up
+    _output_cursor_backward = output.cursor_backward
+
+    # Hide cursor before rendering. (Avoid flickering.)
+    output.hide_cursor()
+
+    def reset_attributes() -> None:
+        "Wrapper around Output.reset_attributes."
+        nonlocal last_style
+        _output_reset_attributes()
+        last_style = None  # Forget last char after resetting attributes.
+
+    def move_cursor(new: Point) -> Point:
+        "Move cursor to this `new` point. Returns the given Point."
+        current_x, current_y = current_pos.x, current_pos.y
+
+        if new.y > current_y:
+            # Use newlines instead of CURSOR_DOWN, because this might add new lines.
+            # CURSOR_DOWN will never create new lines at the bottom.
+            # Also reset attributes, otherwise the newline could draw a
+            # background color.
+            reset_attributes()
+            write("\r\n" * (new.y - current_y))
+            current_x = 0
+            _output_cursor_forward(new.x)
+            return new
+        elif new.y < current_y:
+            _output_cursor_up(current_y - new.y)
+
+        if current_x >= width - 1:
+            write("\r")
+            _output_cursor_forward(new.x)
+        elif new.x < current_x or current_x >= width - 1:
+            _output_cursor_backward(current_x - new.x)
+        elif new.x > current_x:
+            _output_cursor_forward(new.x - current_x)
+
+        return new
+
+    def output_char(char: Char) -> None:
+        """
+        Write the output of this character.
+        """
+        nonlocal last_style
+
+        # If the last printed character has the same style, don't output the
+        # style again.
+        if last_style == char.style:
+            write(char.char)
+        else:
+            # Look up `Attr` for this style string. Only set attributes if different.
+            # (Two style strings can still have the same formatting.)
+            # Note that an empty style string can have formatting that needs to
+            # be applied, because of style transformations.
+            new_attrs = attrs_for_style_string[char.style]
+            if not last_style or new_attrs != attrs_for_style_string[last_style]:
+                _output_set_attributes(new_attrs, color_depth)
+
+            write(char.char)
+            last_style = char.style
+
+    def get_max_column_index(row: Dict[int, Char]) -> int:
+        """
+        Return max used column index, ignoring whitespace (without style) at
+        the end of the line. This is important for people that copy/paste
+        terminal output.
+
+        There are two reasons we are sometimes seeing whitespace at the end:
+        - `BufferControl` adds a trailing space to each line, because it's a
+          possible cursor position, so that the line wrapping won't change if
+          the cursor position moves around.
+        - The `Window` adds a style class to the current line for highlighting
+          (cursor-line).
+        """
+        numbers = (
+            index
+            for index, cell in row.items()
+            if cell.char != " " or style_string_has_style[cell.style]
+        )
+        return max(numbers, default=0)
+
+    # Render for the first time: reset styling.
+    if not previous_screen:
+        reset_attributes()
+
+    # Disable autowrap. (When entering a the alternate screen, or anytime when
+    # we have a prompt. - In the case of a REPL, like IPython, people can have
+    # background threads, and it's hard for debugging if their output is not
+    # wrapped.)
+    if not previous_screen or not full_screen:
+        output.disable_autowrap()
+
+    # When the previous screen has a different size, redraw everything anyway.
+    # Also when we are done. (We might take up less rows, so clearing is important.)
+    if (
+        is_done or not previous_screen or previous_width != width
+    ):  # XXX: also consider height??
+        current_pos = move_cursor(Point(x=0, y=0))
+        reset_attributes()
+        output.erase_down()
+
+        previous_screen = Screen()
+
+    # Get height of the screen.
+    # (height changes as we loop over data_buffer, so remember the current value.)
+    # (Also make sure to clip the height to the size of the output.)
+    current_height = min(screen.height, height)
+
+    # Loop over the rows.
+    row_count = min(max(screen.height, previous_screen.height), height)
+
+    for y in range(row_count):
+        new_row = screen.data_buffer[y]
+        previous_row = previous_screen.data_buffer[y]
+        zero_width_escapes_row = screen.zero_width_escapes[y]
+
+        new_max_line_len = min(width - 1, get_max_column_index(new_row))
+        previous_max_line_len = min(width - 1, get_max_column_index(previous_row))
+
+        # Loop over the columns.
+        c = 0  # Column counter.
+        while c <= new_max_line_len:
+            new_char = new_row[c]
+            old_char = previous_row[c]
+            char_width = new_char.width or 1
+
+            # When the old and new character at this position are different,
+            # draw the output. (Because of the performance, we don't call
+            # `Char.__ne__`, but inline the same expression.)
+            if new_char.char != old_char.char or new_char.style != old_char.style:
+                current_pos = move_cursor(Point(x=c, y=y))
+
+                # Send injected escape sequences to output.
+                if c in zero_width_escapes_row:
+                    write_raw(zero_width_escapes_row[c])
+
+                output_char(new_char)
+                current_pos = Point(x=current_pos.x + char_width, y=current_pos.y)
+
+            c += char_width
+
+        # If the new line is shorter, trim it.
+        if previous_screen and new_max_line_len < previous_max_line_len:
+            current_pos = move_cursor(Point(x=new_max_line_len + 1, y=y))
+            reset_attributes()
+            output.erase_end_of_line()
+
+    # Correctly reserve vertical space as required by the layout.
+    # When this is a new screen (drawn for the first time), or for some reason
+    # higher than the previous one. Move the cursor once to the bottom of the
+    # output. That way, we're sure that the terminal scrolls up, even when the
+    # lower lines of the canvas just contain whitespace.
+
+    # The most obvious reason that we actually want this behaviour is the avoid
+    # the artifact of the input scrolling when the completion menu is shown.
+    # (If the scrolling is actually wanted, the layout can still be build in a
+    # way to behave that way by setting a dynamic height.)
+    if current_height > previous_screen.height:
+        current_pos = move_cursor(Point(x=0, y=current_height - 1))
+
+    # Move cursor:
+    if is_done:
+        current_pos = move_cursor(Point(x=0, y=current_height))
+        output.erase_down()
+    else:
+        current_pos = move_cursor(screen.get_cursor_position(app.layout.current_window))
+
+    if is_done or not full_screen:
+        output.enable_autowrap()
+
+    # Always reset the color attributes. This is important because a background
+    # thread could print data to stdout and we want that to be displayed in the
+    # default colors. (Also, if a background color has been set, many terminals
+    # give weird artifacts on resize events.)
+    reset_attributes()
+
+    if screen.show_cursor or is_done:
+        output.show_cursor()
+
+    return current_pos, last_style
+
+
+class HeightIsUnknownError(Exception):
+    "Information unavailable. Did not yet receive the CPR response."
+
+
+class _StyleStringToAttrsCache(Dict[str, Attrs]):
+    """
+    A cache structure that maps style strings to :class:`.Attr`.
+    (This is an important speed up.)
+    """
+
+    def __init__(
+        self,
+        get_attrs_for_style_str: Callable[["str"], Attrs],
+        style_transformation: StyleTransformation,
+    ) -> None:
+
+        self.get_attrs_for_style_str = get_attrs_for_style_str
+        self.style_transformation = style_transformation
+
+    def __missing__(self, style_str: str) -> Attrs:
+        attrs = self.get_attrs_for_style_str(style_str)
+        attrs = self.style_transformation.transform_attrs(attrs)
+
+        self[style_str] = attrs
+        return attrs
+
+
+class _StyleStringHasStyleCache(Dict[str, bool]):
+    """
+    Cache for remember which style strings don't render the default output
+    style (default fg/bg, no underline and no reverse and no blink). That way
+    we know that we should render these cells, even when they're empty (when
+    they contain a space).
+
+    Note: we don't consider bold/italic/hidden because they don't change the
+    output if there's no text in the cell.
+    """
+
+    def __init__(self, style_string_to_attrs: Dict[str, Attrs]) -> None:
+        self.style_string_to_attrs = style_string_to_attrs
+
+    def __missing__(self, style_str: str) -> bool:
+        attrs = self.style_string_to_attrs[style_str]
+        is_default = bool(
+            attrs.color
+            or attrs.bgcolor
+            or attrs.underline
+            or attrs.strike
+            or attrs.blink
+            or attrs.reverse
+        )
+
+        self[style_str] = is_default
+        return is_default
+
+
+class CPR_Support(Enum):
+    "Enum: whether or not CPR is supported."
+    SUPPORTED = "SUPPORTED"
+    NOT_SUPPORTED = "NOT_SUPPORTED"
+    UNKNOWN = "UNKNOWN"
+
+
+class Renderer:
+    """
+    Typical usage:
+
+    ::
+
+        output = Vt100_Output.from_pty(sys.stdout)
+        r = Renderer(style, output)
+        r.render(app, layout=...)
+    """
+
+    CPR_TIMEOUT = 2  # Time to wait until we consider CPR to be not supported.
+
+    def __init__(
+        self,
+        style: BaseStyle,
+        output: Output,
+        full_screen: bool = False,
+        mouse_support: FilterOrBool = False,
+        cpr_not_supported_callback: Optional[Callable[[], None]] = None,
+    ) -> None:
+
+        self.style = style
+        self.output = output
+        self.full_screen = full_screen
+        self.mouse_support = to_filter(mouse_support)
+        self.cpr_not_supported_callback = cpr_not_supported_callback
+
+        self._in_alternate_screen = False
+        self._mouse_support_enabled = False
+        self._bracketed_paste_enabled = False
+        self._cursor_key_mode_reset = False
+
+        # Future set when we are waiting for a CPR flag.
+        self._waiting_for_cpr_futures: Deque[Future[None]] = deque()
+        self.cpr_support = CPR_Support.UNKNOWN
+
+        if not output.responds_to_cpr:
+            self.cpr_support = CPR_Support.NOT_SUPPORTED
+
+        # Cache for the style.
+        self._attrs_for_style: Optional[_StyleStringToAttrsCache] = None
+        self._style_string_has_style: Optional[_StyleStringHasStyleCache] = None
+        self._last_style_hash: Optional[Hashable] = None
+        self._last_transformation_hash: Optional[Hashable] = None
+        self._last_color_depth: Optional[ColorDepth] = None
+
+        self.reset(_scroll=True)
+
+    def reset(self, _scroll: bool = False, leave_alternate_screen: bool = True) -> None:
+
+        # Reset position
+        self._cursor_pos = Point(x=0, y=0)
+
+        # Remember the last screen instance between renderers. This way,
+        # we can create a `diff` between two screens and only output the
+        # difference. It's also to remember the last height. (To show for
+        # instance a toolbar at the bottom position.)
+        self._last_screen: Optional[Screen] = None
+        self._last_size: Optional[Size] = None
+        self._last_style: Optional[str] = None
+        self._last_cursor_shape: Optional[CursorShape] = None
+
+        # Default MouseHandlers. (Just empty.)
+        self.mouse_handlers = MouseHandlers()
+
+        #: Space from the top of the layout, until the bottom of the terminal.
+        #: We don't know this until a `report_absolute_cursor_row` call.
+        self._min_available_height = 0
+
+        # In case of Windows, also make sure to scroll to the current cursor
+        # position. (Only when rendering the first time.)
+        # It does nothing for vt100 terminals.
+        if _scroll:
+            self.output.scroll_buffer_to_prompt()
+
+        # Quit alternate screen.
+        if self._in_alternate_screen and leave_alternate_screen:
+            self.output.quit_alternate_screen()
+            self._in_alternate_screen = False
+
+        # Disable mouse support.
+        if self._mouse_support_enabled:
+            self.output.disable_mouse_support()
+            self._mouse_support_enabled = False
+
+        # Disable bracketed paste.
+        if self._bracketed_paste_enabled:
+            self.output.disable_bracketed_paste()
+            self._bracketed_paste_enabled = False
+
+        self.output.reset_cursor_shape()
+
+        # NOTE: No need to set/reset cursor key mode here.
+
+        # Flush output. `disable_mouse_support` needs to write to stdout.
+        self.output.flush()
+
+    @property
+    def last_rendered_screen(self) -> Optional[Screen]:
+        """
+        The `Screen` class that was generated during the last rendering.
+        This can be `None`.
+        """
+        return self._last_screen
+
+    @property
+    def height_is_known(self) -> bool:
+        """
+        True when the height from the cursor until the bottom of the terminal
+        is known. (It's often nicer to draw bottom toolbars only if the height
+        is known, in order to avoid flickering when the CPR response arrives.)
+        """
+        if self.full_screen or self._min_available_height > 0:
+            return True
+        try:
+            self._min_available_height = self.output.get_rows_below_cursor_position()
+            return True
+        except NotImplementedError:
+            return False
+
+    @property
+    def rows_above_layout(self) -> int:
+        """
+        Return the number of rows visible in the terminal above the layout.
+        """
+        if self._in_alternate_screen:
+            return 0
+        elif self._min_available_height > 0:
+            total_rows = self.output.get_size().rows
+            last_screen_height = self._last_screen.height if self._last_screen else 0
+            return total_rows - max(self._min_available_height, last_screen_height)
+        else:
+            raise HeightIsUnknownError("Rows above layout is unknown.")
+
+    def request_absolute_cursor_position(self) -> None:
+        """
+        Get current cursor position.
+
+        We do this to calculate the minimum available height that we can
+        consume for rendering the prompt. This is the available space below te
+        cursor.
+
+        For vt100: Do CPR request. (answer will arrive later.)
+        For win32: Do API call. (Answer comes immediately.)
+        """
+        # Only do this request when the cursor is at the top row. (after a
+        # clear or reset). We will rely on that in `report_absolute_cursor_row`.
+        assert self._cursor_pos.y == 0
+
+        # In full-screen mode, always use the total height as min-available-height.
+        if self.full_screen:
+            self._min_available_height = self.output.get_size().rows
+            return
+
+        # For Win32, we have an API call to get the number of rows below the
+        # cursor.
+        try:
+            self._min_available_height = self.output.get_rows_below_cursor_position()
+            return
+        except NotImplementedError:
+            pass
+
+        # Use CPR.
+        if self.cpr_support == CPR_Support.NOT_SUPPORTED:
+            return
+
+        def do_cpr() -> None:
+            # Asks for a cursor position report (CPR).
+            self._waiting_for_cpr_futures.append(Future())
+            self.output.ask_for_cpr()
+
+        if self.cpr_support == CPR_Support.SUPPORTED:
+            do_cpr()
+            return
+
+        # If we don't know whether CPR is supported, only do a request if
+        # none is pending, and test it, using a timer.
+        if self.waiting_for_cpr:
+            return
+
+        do_cpr()
+
+        async def timer() -> None:
+            await sleep(self.CPR_TIMEOUT)
+
+            # Not set in the meantime -> not supported.
+            if self.cpr_support == CPR_Support.UNKNOWN:
+                self.cpr_support = CPR_Support.NOT_SUPPORTED
+
+                if self.cpr_not_supported_callback:
+                    # Make sure to call this callback in the main thread.
+                    self.cpr_not_supported_callback()
+
+        get_app().create_background_task(timer())
+
+    def report_absolute_cursor_row(self, row: int) -> None:
+        """
+        To be called when we know the absolute cursor position.
+        (As an answer of a "Cursor Position Request" response.)
+        """
+        self.cpr_support = CPR_Support.SUPPORTED
+
+        # Calculate the amount of rows from the cursor position until the
+        # bottom of the terminal.
+        total_rows = self.output.get_size().rows
+        rows_below_cursor = total_rows - row + 1
+
+        # Set the minimum available height.
+        self._min_available_height = rows_below_cursor
+
+        # Pop and set waiting for CPR future.
+        try:
+            f = self._waiting_for_cpr_futures.popleft()
+        except IndexError:
+            pass  # Received CPR response without having a CPR.
+        else:
+            f.set_result(None)
+
+    @property
+    def waiting_for_cpr(self) -> bool:
+        """
+        Waiting for CPR flag. True when we send the request, but didn't got a
+        response.
+        """
+        return bool(self._waiting_for_cpr_futures)
+
+    async def wait_for_cpr_responses(self, timeout: int = 1) -> None:
+        """
+        Wait for a CPR response.
+        """
+        cpr_futures = list(self._waiting_for_cpr_futures)  # Make copy.
+
+        # When there are no CPRs in the queue. Don't do anything.
+        if not cpr_futures or self.cpr_support == CPR_Support.NOT_SUPPORTED:
+            return None
+
+        async def wait_for_responses() -> None:
+            for response_f in cpr_futures:
+                await response_f
+
+        async def wait_for_timeout() -> None:
+            await sleep(timeout)
+
+            # Got timeout, erase queue.
+            for response_f in cpr_futures:
+                response_f.cancel()
+            self._waiting_for_cpr_futures = deque()
+
+        tasks = {
+            ensure_future(wait_for_responses()),
+            ensure_future(wait_for_timeout()),
+        }
+        _, pending = await wait(tasks, return_when=FIRST_COMPLETED)
+        for task in pending:
+            task.cancel()
+
+    def render(
+        self, app: "Application[Any]", layout: "Layout", is_done: bool = False
+    ) -> None:
+        """
+        Render the current interface to the output.
+
+        :param is_done: When True, put the cursor at the end of the interface. We
+                won't print any changes to this part.
+        """
+        output = self.output
+
+        # Enter alternate screen.
+        if self.full_screen and not self._in_alternate_screen:
+            self._in_alternate_screen = True
+            output.enter_alternate_screen()
+
+        # Enable bracketed paste.
+        if not self._bracketed_paste_enabled:
+            self.output.enable_bracketed_paste()
+            self._bracketed_paste_enabled = True
+
+        # Reset cursor key mode.
+        if not self._cursor_key_mode_reset:
+            self.output.reset_cursor_key_mode()
+            self._cursor_key_mode_reset = True
+
+        # Enable/disable mouse support.
+        needs_mouse_support = self.mouse_support()
+
+        if needs_mouse_support and not self._mouse_support_enabled:
+            output.enable_mouse_support()
+            self._mouse_support_enabled = True
+
+        elif not needs_mouse_support and self._mouse_support_enabled:
+            output.disable_mouse_support()
+            self._mouse_support_enabled = False
+
+        # Create screen and write layout to it.
+        size = output.get_size()
+        screen = Screen()
+        screen.show_cursor = False  # Hide cursor by default, unless one of the
+        # containers decides to display it.
+        mouse_handlers = MouseHandlers()
+
+        # Calculate height.
+        if self.full_screen:
+            height = size.rows
+        elif is_done:
+            # When we are done, we don't necessary want to fill up until the bottom.
+            height = layout.container.preferred_height(
+                size.columns, size.rows
+            ).preferred
+        else:
+            last_height = self._last_screen.height if self._last_screen else 0
+            height = max(
+                self._min_available_height,
+                last_height,
+                layout.container.preferred_height(size.columns, size.rows).preferred,
+            )
+
+        height = min(height, size.rows)
+
+        # When the size changes, don't consider the previous screen.
+        if self._last_size != size:
+            self._last_screen = None
+
+        # When we render using another style or another color depth, do a full
+        # repaint. (Forget about the previous rendered screen.)
+        # (But note that we still use _last_screen to calculate the height.)
+        if (
+            self.style.invalidation_hash() != self._last_style_hash
+            or app.style_transformation.invalidation_hash()
+            != self._last_transformation_hash
+            or app.color_depth != self._last_color_depth
+        ):
+            self._last_screen = None
+            self._attrs_for_style = None
+            self._style_string_has_style = None
+
+        if self._attrs_for_style is None:
+            self._attrs_for_style = _StyleStringToAttrsCache(
+                self.style.get_attrs_for_style_str, app.style_transformation
+            )
+        if self._style_string_has_style is None:
+            self._style_string_has_style = _StyleStringHasStyleCache(
+                self._attrs_for_style
+            )
+
+        self._last_style_hash = self.style.invalidation_hash()
+        self._last_transformation_hash = app.style_transformation.invalidation_hash()
+        self._last_color_depth = app.color_depth
+
+        layout.container.write_to_screen(
+            screen,
+            mouse_handlers,
+            WritePosition(xpos=0, ypos=0, width=size.columns, height=height),
+            parent_style="",
+            erase_bg=False,
+            z_index=None,
+        )
+        screen.draw_all_floats()
+
+        # When grayed. Replace all styles in the new screen.
+        if app.exit_style:
+            screen.append_style_to_content(app.exit_style)
+
+        # Process diff and write to output.
+        self._cursor_pos, self._last_style = _output_screen_diff(
+            app,
+            output,
+            screen,
+            self._cursor_pos,
+            app.color_depth,
+            self._last_screen,
+            self._last_style,
+            is_done,
+            full_screen=self.full_screen,
+            attrs_for_style_string=self._attrs_for_style,
+            style_string_has_style=self._style_string_has_style,
+            size=size,
+            previous_width=(self._last_size.columns if self._last_size else 0),
+        )
+        self._last_screen = screen
+        self._last_size = size
+        self.mouse_handlers = mouse_handlers
+
+        # Handle cursor shapes.
+        new_cursor_shape = app.cursor.get_cursor_shape(app)
+        if (
+            self._last_cursor_shape is None
+            or self._last_cursor_shape != new_cursor_shape
+        ):
+            output.set_cursor_shape(new_cursor_shape)
+            self._last_cursor_shape = new_cursor_shape
+
+        # Flush buffered output.
+        output.flush()
+
+        # Set visible windows in layout.
+        app.layout.visible_windows = screen.visible_windows
+
+        if is_done:
+            self.reset()
+
+    def erase(self, leave_alternate_screen: bool = True) -> None:
+        """
+        Hide all output and put the cursor back at the first line. This is for
+        instance used for running a system command (while hiding the CLI) and
+        later resuming the same CLI.)
+
+        :param leave_alternate_screen: When True, and when inside an alternate
+            screen buffer, quit the alternate screen.
+        """
+        output = self.output
+
+        output.cursor_backward(self._cursor_pos.x)
+        output.cursor_up(self._cursor_pos.y)
+        output.erase_down()
+        output.reset_attributes()
+        output.enable_autowrap()
+
+        output.flush()
+
+        self.reset(leave_alternate_screen=leave_alternate_screen)
+
+    def clear(self) -> None:
+        """
+        Clear screen and go to 0,0
+        """
+        # Erase current output first.
+        self.erase()
+
+        # Send "Erase Screen" command and go to (0, 0).
+        output = self.output
+
+        output.erase_screen()
+        output.cursor_goto(0, 0)
+        output.flush()
+
+        self.request_absolute_cursor_position()
+
+
+def print_formatted_text(
+    output: Output,
+    formatted_text: AnyFormattedText,
+    style: BaseStyle,
+    style_transformation: Optional[StyleTransformation] = None,
+    color_depth: Optional[ColorDepth] = None,
+) -> None:
+    """
+    Print a list of (style_str, text) tuples in the given style to the output.
+    """
+    fragments = to_formatted_text(formatted_text)
+    style_transformation = style_transformation or DummyStyleTransformation()
+    color_depth = color_depth or output.get_default_color_depth()
+
+    # Reset first.
+    output.reset_attributes()
+    output.enable_autowrap()
+    last_attrs: Optional[Attrs] = None
+
+    # Print all (style_str, text) tuples.
+    attrs_for_style_string = _StyleStringToAttrsCache(
+        style.get_attrs_for_style_str, style_transformation
+    )
+
+    for style_str, text, *_ in fragments:
+        attrs = attrs_for_style_string[style_str]
+
+        # Set style attributes if something changed.
+        if attrs != last_attrs:
+            if attrs:
+                output.set_attributes(attrs, color_depth)
+            else:
+                output.reset_attributes()
+        last_attrs = attrs
+
+        # Print escape sequences as raw output
+        if "[ZeroWidthEscape]" in style_str:
+            output.write_raw(text)
+        else:
+            # Eliminate carriage returns
+            text = text.replace("\r", "")
+            # Insert a carriage return before every newline (important when the
+            # front-end is a telnet client).
+            text = text.replace("\n", "\r\n")
+            output.write(text)
+
+    # Reset again.
+    output.reset_attributes()
+    output.flush()
diff --git a/src/prompt_toolkit/search.py b/src/prompt_toolkit/search.py
new file mode 100644
index 0000000..413cc6a
--- /dev/null
+++ b/src/prompt_toolkit/search.py
@@ -0,0 +1,229 @@
+"""
+Search operations.
+
+For the key bindings implementation with attached filters, check
+`prompt_toolkit.key_binding.bindings.search`. (Use these for new key bindings
+instead of calling these function directly.)
+"""
+from enum import Enum
+from typing import TYPE_CHECKING, Dict, Optional
+
+from .application.current import get_app
+from .filters import FilterOrBool, is_searching, to_filter
+from .key_binding.vi_state import InputMode
+
+if TYPE_CHECKING:
+    from prompt_toolkit.layout.controls import BufferControl, SearchBufferControl
+    from prompt_toolkit.layout.layout import Layout
+
+__all__ = [
+    "SearchDirection",
+    "start_search",
+    "stop_search",
+]
+
+
+class SearchDirection(Enum):
+    FORWARD = "FORWARD"
+    BACKWARD = "BACKWARD"
+
+
+class SearchState:
+    """
+    A search 'query', associated with a search field (like a SearchToolbar).
+
+    Every searchable `BufferControl` points to a `search_buffer_control`
+    (another `BufferControls`) which represents the search field. The
+    `SearchState` attached to that search field is used for storing the current
+    search query.
+
+    It is possible to have one searchfield for multiple `BufferControls`. In
+    that case, they'll share the same `SearchState`.
+    If there are multiple `BufferControls` that display the same `Buffer`, then
+    they can have a different `SearchState` each (if they have a different
+    search control).
+    """
+
+    __slots__ = ("text", "direction", "ignore_case")
+
+    def __init__(
+        self,
+        text: str = "",
+        direction: SearchDirection = SearchDirection.FORWARD,
+        ignore_case: FilterOrBool = False,
+    ) -> None:
+
+        self.text = text
+        self.direction = direction
+        self.ignore_case = to_filter(ignore_case)
+
+    def __repr__(self) -> str:
+        return "{}({!r}, direction={!r}, ignore_case={!r})".format(
+            self.__class__.__name__,
+            self.text,
+            self.direction,
+            self.ignore_case,
+        )
+
+    def __invert__(self) -> "SearchState":
+        """
+        Create a new SearchState where backwards becomes forwards and the other
+        way around.
+        """
+        if self.direction == SearchDirection.BACKWARD:
+            direction = SearchDirection.FORWARD
+        else:
+            direction = SearchDirection.BACKWARD
+
+        return SearchState(
+            text=self.text, direction=direction, ignore_case=self.ignore_case
+        )
+
+
+def start_search(
+    buffer_control: Optional["BufferControl"] = None,
+    direction: SearchDirection = SearchDirection.FORWARD,
+) -> None:
+    """
+    Start search through the given `buffer_control` using the
+    `search_buffer_control`.
+
+    :param buffer_control: Start search for this `BufferControl`. If not given,
+        search through the current control.
+    """
+    from prompt_toolkit.layout.controls import BufferControl
+
+    assert buffer_control is None or isinstance(buffer_control, BufferControl)
+
+    layout = get_app().layout
+
+    # When no control is given, use the current control if that's a BufferControl.
+    if buffer_control is None:
+        if not isinstance(layout.current_control, BufferControl):
+            return
+        buffer_control = layout.current_control
+
+    # Only if this control is searchable.
+    search_buffer_control = buffer_control.search_buffer_control
+
+    if search_buffer_control:
+        buffer_control.search_state.direction = direction
+
+        # Make sure to focus the search BufferControl
+        layout.focus(search_buffer_control)
+
+        # Remember search link.
+        layout.search_links[search_buffer_control] = buffer_control
+
+        # If we're in Vi mode, make sure to go into insert mode.
+        get_app().vi_state.input_mode = InputMode.INSERT
+
+
+def stop_search(buffer_control: Optional["BufferControl"] = None) -> None:
+    """
+    Stop search through the given `buffer_control`.
+    """
+    layout = get_app().layout
+
+    if buffer_control is None:
+        buffer_control = layout.search_target_buffer_control
+        if buffer_control is None:
+            # (Should not happen, but possible when `stop_search` is called
+            # when we're not searching.)
+            return
+        search_buffer_control = buffer_control.search_buffer_control
+    else:
+        assert buffer_control in layout.search_links.values()
+        search_buffer_control = _get_reverse_search_links(layout)[buffer_control]
+
+    # Focus the original buffer again.
+    layout.focus(buffer_control)
+
+    if search_buffer_control is not None:
+        # Remove the search link.
+        del layout.search_links[search_buffer_control]
+
+        # Reset content of search control.
+        search_buffer_control.buffer.reset()
+
+    # If we're in Vi mode, go back to navigation mode.
+    get_app().vi_state.input_mode = InputMode.NAVIGATION
+
+
+def do_incremental_search(direction: SearchDirection, count: int = 1) -> None:
+    """
+    Apply search, but keep search buffer focused.
+    """
+    assert is_searching()
+
+    layout = get_app().layout
+
+    # Only search if the current control is a `BufferControl`.
+    from prompt_toolkit.layout.controls import BufferControl
+
+    search_control = layout.current_control
+    if not isinstance(search_control, BufferControl):
+        return
+
+    prev_control = layout.search_target_buffer_control
+    if prev_control is None:
+        return
+    search_state = prev_control.search_state
+
+    # Update search_state.
+    direction_changed = search_state.direction != direction
+
+    search_state.text = search_control.buffer.text
+    search_state.direction = direction
+
+    # Apply search to current buffer.
+    if not direction_changed:
+        prev_control.buffer.apply_search(
+            search_state, include_current_position=False, count=count
+        )
+
+
+def accept_search() -> None:
+    """
+    Accept current search query. Focus original `BufferControl` again.
+    """
+    layout = get_app().layout
+
+    search_control = layout.current_control
+    target_buffer_control = layout.search_target_buffer_control
+
+    from prompt_toolkit.layout.controls import BufferControl
+
+    if not isinstance(search_control, BufferControl):
+        return
+    if target_buffer_control is None:
+        return
+
+    search_state = target_buffer_control.search_state
+
+    # Update search state.
+    if search_control.buffer.text:
+        search_state.text = search_control.buffer.text
+
+    # Apply search.
+    target_buffer_control.buffer.apply_search(
+        search_state, include_current_position=True
+    )
+
+    # Add query to history of search line.
+    search_control.buffer.append_to_history()
+
+    # Stop search and focus previous control again.
+    stop_search(target_buffer_control)
+
+
+def _get_reverse_search_links(
+    layout: "Layout",
+) -> Dict["BufferControl", "SearchBufferControl"]:
+    """
+    Return mapping from BufferControl to SearchBufferControl.
+    """
+    return {
+        buffer_control: search_buffer_control
+        for search_buffer_control, buffer_control in layout.search_links.items()
+    }
diff --git a/src/prompt_toolkit/selection.py b/src/prompt_toolkit/selection.py
new file mode 100644
index 0000000..a02aa87
--- /dev/null
+++ b/src/prompt_toolkit/selection.py
@@ -0,0 +1,60 @@
+"""
+Data structures for the selection.
+"""
+from enum import Enum
+
+__all__ = [
+    "SelectionType",
+    "PasteMode",
+    "SelectionState",
+]
+
+
+class SelectionType(Enum):
+    """
+    Type of selection.
+    """
+
+    #: Characters. (Visual in Vi.)
+    CHARACTERS = "CHARACTERS"
+
+    #: Whole lines. (Visual-Line in Vi.)
+    LINES = "LINES"
+
+    #: A block selection. (Visual-Block in Vi.)
+    BLOCK = "BLOCK"
+
+
+class PasteMode(Enum):
+    EMACS = "EMACS"  # Yank like emacs.
+    VI_AFTER = "VI_AFTER"  # When pressing 'p' in Vi.
+    VI_BEFORE = "VI_BEFORE"  # When pressing 'P' in Vi.
+
+
+class SelectionState:
+    """
+    State of the current selection.
+
+    :param original_cursor_position: int
+    :param type: :class:`~.SelectionType`
+    """
+
+    def __init__(
+        self,
+        original_cursor_position: int = 0,
+        type: SelectionType = SelectionType.CHARACTERS,
+    ) -> None:
+
+        self.original_cursor_position = original_cursor_position
+        self.type = type
+        self.shift_mode = False
+
+    def enter_shift_mode(self) -> None:
+        self.shift_mode = True
+
+    def __repr__(self) -> str:
+        return "{}(original_cursor_position={!r}, type={!r})".format(
+            self.__class__.__name__,
+            self.original_cursor_position,
+            self.type,
+        )
diff --git a/src/prompt_toolkit/shortcuts/__init__.py b/src/prompt_toolkit/shortcuts/__init__.py
new file mode 100644
index 0000000..10ad314
--- /dev/null
+++ b/src/prompt_toolkit/shortcuts/__init__.py
@@ -0,0 +1,44 @@
+from .dialogs import (
+    button_dialog,
+    checkboxlist_dialog,
+    input_dialog,
+    message_dialog,
+    progress_dialog,
+    radiolist_dialog,
+    yes_no_dialog,
+)
+from .progress_bar import ProgressBar, ProgressBarCounter
+from .prompt import (
+    CompleteStyle,
+    PromptSession,
+    confirm,
+    create_confirm_session,
+    prompt,
+)
+from .utils import clear, clear_title, print_container, print_formatted_text, set_title
+
+__all__ = [
+    # Dialogs.
+    "input_dialog",
+    "message_dialog",
+    "progress_dialog",
+    "checkboxlist_dialog",
+    "radiolist_dialog",
+    "yes_no_dialog",
+    "button_dialog",
+    # Prompts.
+    "PromptSession",
+    "prompt",
+    "confirm",
+    "create_confirm_session",
+    "CompleteStyle",
+    # Progress bars.
+    "ProgressBar",
+    "ProgressBarCounter",
+    # Utils.
+    "clear",
+    "clear_title",
+    "print_container",
+    "print_formatted_text",
+    "set_title",
+]
diff --git a/src/prompt_toolkit/shortcuts/dialogs.py b/src/prompt_toolkit/shortcuts/dialogs.py
new file mode 100644
index 0000000..eacb05a
--- /dev/null
+++ b/src/prompt_toolkit/shortcuts/dialogs.py
@@ -0,0 +1,327 @@
+import functools
+from typing import Any, Callable, List, Optional, Sequence, Tuple, TypeVar
+
+from prompt_toolkit.application import Application
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.buffer import Buffer
+from prompt_toolkit.completion import Completer
+from prompt_toolkit.eventloop import get_event_loop, run_in_executor_with_context
+from prompt_toolkit.filters import FilterOrBool
+from prompt_toolkit.formatted_text import AnyFormattedText
+from prompt_toolkit.key_binding.bindings.focus import focus_next, focus_previous
+from prompt_toolkit.key_binding.defaults import load_key_bindings
+from prompt_toolkit.key_binding.key_bindings import KeyBindings, merge_key_bindings
+from prompt_toolkit.layout import Layout
+from prompt_toolkit.layout.containers import AnyContainer, HSplit
+from prompt_toolkit.layout.dimension import Dimension as D
+from prompt_toolkit.styles import BaseStyle
+from prompt_toolkit.validation import Validator
+from prompt_toolkit.widgets import (
+    Box,
+    Button,
+    CheckboxList,
+    Dialog,
+    Label,
+    ProgressBar,
+    RadioList,
+    TextArea,
+    ValidationToolbar,
+)
+
+__all__ = [
+    "yes_no_dialog",
+    "button_dialog",
+    "input_dialog",
+    "message_dialog",
+    "radiolist_dialog",
+    "checkboxlist_dialog",
+    "progress_dialog",
+]
+
+
+def yes_no_dialog(
+    title: AnyFormattedText = "",
+    text: AnyFormattedText = "",
+    yes_text: str = "Yes",
+    no_text: str = "No",
+    style: Optional[BaseStyle] = None,
+) -> Application[bool]:
+    """
+    Display a Yes/No dialog.
+    Return a boolean.
+    """
+
+    def yes_handler() -> None:
+        get_app().exit(result=True)
+
+    def no_handler() -> None:
+        get_app().exit(result=False)
+
+    dialog = Dialog(
+        title=title,
+        body=Label(text=text, dont_extend_height=True),
+        buttons=[
+            Button(text=yes_text, handler=yes_handler),
+            Button(text=no_text, handler=no_handler),
+        ],
+        with_background=True,
+    )
+
+    return _create_app(dialog, style)
+
+
+_T = TypeVar("_T")
+
+
+def button_dialog(
+    title: AnyFormattedText = "",
+    text: AnyFormattedText = "",
+    buttons: List[Tuple[str, _T]] = [],
+    style: Optional[BaseStyle] = None,
+) -> Application[_T]:
+    """
+    Display a dialog with button choices (given as a list of tuples).
+    Return the value associated with button.
+    """
+
+    def button_handler(v: _T) -> None:
+        get_app().exit(result=v)
+
+    dialog = Dialog(
+        title=title,
+        body=Label(text=text, dont_extend_height=True),
+        buttons=[
+            Button(text=t, handler=functools.partial(button_handler, v))
+            for t, v in buttons
+        ],
+        with_background=True,
+    )
+
+    return _create_app(dialog, style)
+
+
+def input_dialog(
+    title: AnyFormattedText = "",
+    text: AnyFormattedText = "",
+    ok_text: str = "OK",
+    cancel_text: str = "Cancel",
+    completer: Optional[Completer] = None,
+    validator: Optional[Validator] = None,
+    password: FilterOrBool = False,
+    style: Optional[BaseStyle] = None,
+    default: str = "",
+) -> Application[str]:
+    """
+    Display a text input box.
+    Return the given text, or None when cancelled.
+    """
+
+    def accept(buf: Buffer) -> bool:
+        get_app().layout.focus(ok_button)
+        return True  # Keep text.
+
+    def ok_handler() -> None:
+        get_app().exit(result=textfield.text)
+
+    ok_button = Button(text=ok_text, handler=ok_handler)
+    cancel_button = Button(text=cancel_text, handler=_return_none)
+
+    textfield = TextArea(
+        text=default,
+        multiline=False,
+        password=password,
+        completer=completer,
+        validator=validator,
+        accept_handler=accept,
+    )
+
+    dialog = Dialog(
+        title=title,
+        body=HSplit(
+            [
+                Label(text=text, dont_extend_height=True),
+                textfield,
+                ValidationToolbar(),
+            ],
+            padding=D(preferred=1, max=1),
+        ),
+        buttons=[ok_button, cancel_button],
+        with_background=True,
+    )
+
+    return _create_app(dialog, style)
+
+
+def message_dialog(
+    title: AnyFormattedText = "",
+    text: AnyFormattedText = "",
+    ok_text: str = "Ok",
+    style: Optional[BaseStyle] = None,
+) -> Application[None]:
+    """
+    Display a simple message box and wait until the user presses enter.
+    """
+    dialog = Dialog(
+        title=title,
+        body=Label(text=text, dont_extend_height=True),
+        buttons=[Button(text=ok_text, handler=_return_none)],
+        with_background=True,
+    )
+
+    return _create_app(dialog, style)
+
+
+def radiolist_dialog(
+    title: AnyFormattedText = "",
+    text: AnyFormattedText = "",
+    ok_text: str = "Ok",
+    cancel_text: str = "Cancel",
+    values: Optional[Sequence[Tuple[_T, AnyFormattedText]]] = None,
+    default: Optional[_T] = None,
+    style: Optional[BaseStyle] = None,
+) -> Application[_T]:
+    """
+    Display a simple list of element the user can choose amongst.
+
+    Only one element can be selected at a time using Arrow keys and Enter.
+    The focus can be moved between the list and the Ok/Cancel button with tab.
+    """
+    if values is None:
+        values = []
+
+    def ok_handler() -> None:
+        get_app().exit(result=radio_list.current_value)
+
+    radio_list = RadioList(values=values, default=default)
+
+    dialog = Dialog(
+        title=title,
+        body=HSplit(
+            [Label(text=text, dont_extend_height=True), radio_list],
+            padding=1,
+        ),
+        buttons=[
+            Button(text=ok_text, handler=ok_handler),
+            Button(text=cancel_text, handler=_return_none),
+        ],
+        with_background=True,
+    )
+
+    return _create_app(dialog, style)
+
+
+def checkboxlist_dialog(
+    title: AnyFormattedText = "",
+    text: AnyFormattedText = "",
+    ok_text: str = "Ok",
+    cancel_text: str = "Cancel",
+    values: Optional[Sequence[Tuple[_T, AnyFormattedText]]] = None,
+    default_values: Optional[Sequence[_T]] = None,
+    style: Optional[BaseStyle] = None,
+) -> Application[List[_T]]:
+    """
+    Display a simple list of element the user can choose multiple values amongst.
+
+    Several elements can be selected at a time using Arrow keys and Enter.
+    The focus can be moved between the list and the Ok/Cancel button with tab.
+    """
+    if values is None:
+        values = []
+
+    def ok_handler() -> None:
+        get_app().exit(result=cb_list.current_values)
+
+    cb_list = CheckboxList(values=values, default_values=default_values)
+
+    dialog = Dialog(
+        title=title,
+        body=HSplit(
+            [Label(text=text, dont_extend_height=True), cb_list],
+            padding=1,
+        ),
+        buttons=[
+            Button(text=ok_text, handler=ok_handler),
+            Button(text=cancel_text, handler=_return_none),
+        ],
+        with_background=True,
+    )
+
+    return _create_app(dialog, style)
+
+
+def progress_dialog(
+    title: AnyFormattedText = "",
+    text: AnyFormattedText = "",
+    run_callback: Callable[[Callable[[int], None], Callable[[str], None]], None] = (
+        lambda *a: None
+    ),
+    style: Optional[BaseStyle] = None,
+) -> Application[None]:
+    """
+    :param run_callback: A function that receives as input a `set_percentage`
+        function and it does the work.
+    """
+    loop = get_event_loop()
+    progressbar = ProgressBar()
+    text_area = TextArea(
+        focusable=False,
+        # Prefer this text area as big as possible, to avoid having a window
+        # that keeps resizing when we add text to it.
+        height=D(preferred=10**10),
+    )
+
+    dialog = Dialog(
+        body=HSplit(
+            [
+                Box(Label(text=text)),
+                Box(text_area, padding=D.exact(1)),
+                progressbar,
+            ]
+        ),
+        title=title,
+        with_background=True,
+    )
+    app = _create_app(dialog, style)
+
+    def set_percentage(value: int) -> None:
+        progressbar.percentage = int(value)
+        app.invalidate()
+
+    def log_text(text: str) -> None:
+        loop.call_soon_threadsafe(text_area.buffer.insert_text, text)
+        app.invalidate()
+
+    # Run the callback in the executor. When done, set a return value for the
+    # UI, so that it quits.
+    def start() -> None:
+        try:
+            run_callback(set_percentage, log_text)
+        finally:
+            app.exit()
+
+    def pre_run() -> None:
+        run_in_executor_with_context(start)
+
+    app.pre_run_callables.append(pre_run)
+
+    return app
+
+
+def _create_app(dialog: AnyContainer, style: Optional[BaseStyle]) -> Application[Any]:
+    # Key bindings.
+    bindings = KeyBindings()
+    bindings.add("tab")(focus_next)
+    bindings.add("s-tab")(focus_previous)
+
+    return Application(
+        layout=Layout(dialog),
+        key_bindings=merge_key_bindings([load_key_bindings(), bindings]),
+        mouse_support=True,
+        style=style,
+        full_screen=True,
+    )
+
+
+def _return_none() -> None:
+    "Button handler that returns None."
+    get_app().exit()
diff --git a/src/prompt_toolkit/shortcuts/progress_bar/__init__.py b/src/prompt_toolkit/shortcuts/progress_bar/__init__.py
new file mode 100644
index 0000000..7d0fbb5
--- /dev/null
+++ b/src/prompt_toolkit/shortcuts/progress_bar/__init__.py
@@ -0,0 +1,31 @@
+from .base import ProgressBar, ProgressBarCounter
+from .formatters import (
+    Bar,
+    Formatter,
+    IterationsPerSecond,
+    Label,
+    Percentage,
+    Progress,
+    Rainbow,
+    SpinningWheel,
+    Text,
+    TimeElapsed,
+    TimeLeft,
+)
+
+__all__ = [
+    "ProgressBar",
+    "ProgressBarCounter",
+    # Formatters.
+    "Formatter",
+    "Text",
+    "Label",
+    "Percentage",
+    "Bar",
+    "Progress",
+    "TimeElapsed",
+    "TimeLeft",
+    "IterationsPerSecond",
+    "SpinningWheel",
+    "Rainbow",
+]
diff --git a/src/prompt_toolkit/shortcuts/progress_bar/base.py b/src/prompt_toolkit/shortcuts/progress_bar/base.py
new file mode 100644
index 0000000..d790466
--- /dev/null
+++ b/src/prompt_toolkit/shortcuts/progress_bar/base.py
@@ -0,0 +1,464 @@
+"""
+Progress bar implementation on top of prompt_toolkit.
+
+::
+
+    with ProgressBar(...) as pb:
+        for item in pb(data):
+            ...
+"""
+import datetime
+import functools
+import os
+import signal
+import threading
+import traceback
+from asyncio import new_event_loop, set_event_loop
+from typing import (
+    Callable,
+    Generic,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Sequence,
+    Sized,
+    TextIO,
+    TypeVar,
+    cast,
+)
+
+from prompt_toolkit.application import Application
+from prompt_toolkit.application.current import get_app_session
+from prompt_toolkit.eventloop import get_event_loop
+from prompt_toolkit.filters import Condition, is_done, renderer_height_is_known
+from prompt_toolkit.formatted_text import (
+    AnyFormattedText,
+    StyleAndTextTuples,
+    to_formatted_text,
+)
+from prompt_toolkit.input import Input
+from prompt_toolkit.key_binding import KeyBindings
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.layout import (
+    ConditionalContainer,
+    FormattedTextControl,
+    HSplit,
+    Layout,
+    VSplit,
+    Window,
+)
+from prompt_toolkit.layout.controls import UIContent, UIControl
+from prompt_toolkit.layout.dimension import AnyDimension, D
+from prompt_toolkit.output import ColorDepth, Output
+from prompt_toolkit.styles import BaseStyle
+
+from .formatters import Formatter, create_default_formatters
+
+try:
+    import contextvars
+except ImportError:
+    from prompt_toolkit.eventloop import dummy_contextvars
+
+    contextvars = dummy_contextvars  # type: ignore
+
+
+__all__ = ["ProgressBar"]
+
+E = KeyPressEvent
+
+_SIGWINCH = getattr(signal, "SIGWINCH", None)
+
+
+def create_key_bindings(cancel_callback: Optional[Callable[[], None]]) -> KeyBindings:
+    """
+    Key bindings handled by the progress bar.
+    (The main thread is not supposed to handle any key bindings.)
+    """
+    kb = KeyBindings()
+
+    @kb.add("c-l")
+    def _clear(event: E) -> None:
+        event.app.renderer.clear()
+
+    if cancel_callback is not None:
+
+        @kb.add("c-c")
+        def _interrupt(event: E) -> None:
+            "Kill the 'body' of the progress bar, but only if we run from the main thread."
+            assert cancel_callback is not None
+            cancel_callback()
+
+    return kb
+
+
+_T = TypeVar("_T")
+
+
+class ProgressBar:
+    """
+    Progress bar context manager.
+
+    Usage ::
+
+        with ProgressBar(...) as pb:
+            for item in pb(data):
+                ...
+
+    :param title: Text to be displayed above the progress bars. This can be a
+        callable or formatted text as well.
+    :param formatters: List of :class:`.Formatter` instances.
+    :param bottom_toolbar: Text to be displayed in the bottom toolbar. This
+        can be a callable or formatted text.
+    :param style: :class:`prompt_toolkit.styles.BaseStyle` instance.
+    :param key_bindings: :class:`.KeyBindings` instance.
+    :param cancel_callback: Callback function that's called when control-c is
+        pressed by the user. This can be used for instance to start "proper"
+        cancellation if the wrapped code supports it.
+    :param file: The file object used for rendering, by default `sys.stderr` is used.
+
+    :param color_depth: `prompt_toolkit` `ColorDepth` instance.
+    :param output: :class:`~prompt_toolkit.output.Output` instance.
+    :param input: :class:`~prompt_toolkit.input.Input` instance.
+    """
+
+    def __init__(
+        self,
+        title: AnyFormattedText = None,
+        formatters: Optional[Sequence[Formatter]] = None,
+        bottom_toolbar: AnyFormattedText = None,
+        style: Optional[BaseStyle] = None,
+        key_bindings: Optional[KeyBindings] = None,
+        cancel_callback: Optional[Callable[[], None]] = None,
+        file: Optional[TextIO] = None,
+        color_depth: Optional[ColorDepth] = None,
+        output: Optional[Output] = None,
+        input: Optional[Input] = None,
+    ) -> None:
+
+        self.title = title
+        self.formatters = formatters or create_default_formatters()
+        self.bottom_toolbar = bottom_toolbar
+        self.counters: List[ProgressBarCounter[object]] = []
+        self.style = style
+        self.key_bindings = key_bindings
+        self.cancel_callback = cancel_callback
+
+        # If no `cancel_callback` was given, and we're creating the progress
+        # bar from the main thread. Cancel by sending a `KeyboardInterrupt` to
+        # the main thread.
+        if (
+            self.cancel_callback is None
+            and threading.currentThread() == threading.main_thread()
+        ):
+
+            def keyboard_interrupt_to_main_thread() -> None:
+                os.kill(os.getpid(), signal.SIGINT)
+
+            self.cancel_callback = keyboard_interrupt_to_main_thread
+
+        # Note that we use __stderr__ as default error output, because that
+        # works best with `patch_stdout`.
+        self.color_depth = color_depth
+        self.output = output or get_app_session().output
+        self.input = input or get_app_session().input
+
+        self._thread: Optional[threading.Thread] = None
+
+        self._app_loop = new_event_loop()
+        self._has_sigwinch = False
+        self._app_started = threading.Event()
+
+    def __enter__(self) -> "ProgressBar":
+        # Create UI Application.
+        title_toolbar = ConditionalContainer(
+            Window(
+                FormattedTextControl(lambda: self.title),
+                height=1,
+                style="class:progressbar,title",
+            ),
+            filter=Condition(lambda: self.title is not None),
+        )
+
+        bottom_toolbar = ConditionalContainer(
+            Window(
+                FormattedTextControl(
+                    lambda: self.bottom_toolbar, style="class:bottom-toolbar.text"
+                ),
+                style="class:bottom-toolbar",
+                height=1,
+            ),
+            filter=~is_done
+            & renderer_height_is_known
+            & Condition(lambda: self.bottom_toolbar is not None),
+        )
+
+        def width_for_formatter(formatter: Formatter) -> AnyDimension:
+            # Needs to be passed as callable (partial) to the 'width'
+            # parameter, because we want to call it on every resize.
+            return formatter.get_width(progress_bar=self)
+
+        progress_controls = [
+            Window(
+                content=_ProgressControl(self, f, self.cancel_callback),
+                width=functools.partial(width_for_formatter, f),
+            )
+            for f in self.formatters
+        ]
+
+        self.app: Application[None] = Application(
+            min_redraw_interval=0.05,
+            layout=Layout(
+                HSplit(
+                    [
+                        title_toolbar,
+                        VSplit(
+                            progress_controls,
+                            height=lambda: D(
+                                preferred=len(self.counters), max=len(self.counters)
+                            ),
+                        ),
+                        Window(),
+                        bottom_toolbar,
+                    ]
+                )
+            ),
+            style=self.style,
+            key_bindings=self.key_bindings,
+            refresh_interval=0.3,
+            color_depth=self.color_depth,
+            output=self.output,
+            input=self.input,
+        )
+
+        # Run application in different thread.
+        def run() -> None:
+            set_event_loop(self._app_loop)
+            try:
+                self.app.run(pre_run=self._app_started.set)
+            except BaseException as e:
+                traceback.print_exc()
+                print(e)
+
+        ctx: contextvars.Context = contextvars.copy_context()
+
+        self._thread = threading.Thread(target=ctx.run, args=(run,))
+        self._thread.start()
+
+        return self
+
+    def __exit__(self, *a: object) -> None:
+        # Wait for the app to be started. Make sure we don't quit earlier,
+        # otherwise `self.app.exit` won't terminate the app because
+        # `self.app.future` has not yet been set.
+        self._app_started.wait()
+
+        # Quit UI application.
+        if self.app.is_running:
+            self._app_loop.call_soon_threadsafe(self.app.exit)
+
+        if self._thread is not None:
+            self._thread.join()
+        self._app_loop.close()
+
+    def __call__(
+        self,
+        data: Optional[Iterable[_T]] = None,
+        label: AnyFormattedText = "",
+        remove_when_done: bool = False,
+        total: Optional[int] = None,
+    ) -> "ProgressBarCounter[_T]":
+        """
+        Start a new counter.
+
+        :param label: Title text or description for this progress. (This can be
+            formatted text as well).
+        :param remove_when_done: When `True`, hide this progress bar.
+        :param total: Specify the maximum value if it can't be calculated by
+            calling ``len``.
+        """
+        counter = ProgressBarCounter(
+            self, data, label=label, remove_when_done=remove_when_done, total=total
+        )
+        self.counters.append(counter)
+        return counter
+
+    def invalidate(self) -> None:
+        self.app.invalidate()
+
+
+class _ProgressControl(UIControl):
+    """
+    User control for the progress bar.
+    """
+
+    def __init__(
+        self,
+        progress_bar: ProgressBar,
+        formatter: Formatter,
+        cancel_callback: Optional[Callable[[], None]],
+    ) -> None:
+        self.progress_bar = progress_bar
+        self.formatter = formatter
+        self._key_bindings = create_key_bindings(cancel_callback)
+
+    def create_content(self, width: int, height: int) -> UIContent:
+        items: List[StyleAndTextTuples] = []
+
+        for pr in self.progress_bar.counters:
+            try:
+                text = self.formatter.format(self.progress_bar, pr, width)
+            except BaseException:
+                traceback.print_exc()
+                text = "ERROR"
+
+            items.append(to_formatted_text(text))
+
+        def get_line(i: int) -> StyleAndTextTuples:
+            return items[i]
+
+        return UIContent(get_line=get_line, line_count=len(items), show_cursor=False)
+
+    def is_focusable(self) -> bool:
+        return True  # Make sure that the key bindings work.
+
+    def get_key_bindings(self) -> KeyBindings:
+        return self._key_bindings
+
+
+_CounterItem = TypeVar("_CounterItem", covariant=True)
+
+
+class ProgressBarCounter(Generic[_CounterItem]):
+    """
+    An individual counter (A progress bar can have multiple counters).
+    """
+
+    def __init__(
+        self,
+        progress_bar: ProgressBar,
+        data: Optional[Iterable[_CounterItem]] = None,
+        label: AnyFormattedText = "",
+        remove_when_done: bool = False,
+        total: Optional[int] = None,
+    ) -> None:
+
+        self.start_time = datetime.datetime.now()
+        self.stop_time: Optional[datetime.datetime] = None
+        self.progress_bar = progress_bar
+        self.data = data
+        self.items_completed = 0
+        self.label = label
+        self.remove_when_done = remove_when_done
+        self._done = False
+        self.total: Optional[int]
+
+        if total is None:
+            try:
+                self.total = len(cast(Sized, data))
+            except TypeError:
+                self.total = None  # We don't know the total length.
+        else:
+            self.total = total
+
+    def __iter__(self) -> Iterator[_CounterItem]:
+        if self.data is not None:
+            try:
+                for item in self.data:
+                    yield item
+                    self.item_completed()
+
+                # Only done if we iterate to the very end.
+                self.done = True
+            finally:
+                # Ensure counter has stopped even if we did not iterate to the
+                # end (e.g. break or exceptions).
+                self.stopped = True
+        else:
+            raise NotImplementedError("No data defined to iterate over.")
+
+    def item_completed(self) -> None:
+        """
+        Start handling the next item.
+
+        (Can be called manually in case we don't have a collection to loop through.)
+        """
+        self.items_completed += 1
+        self.progress_bar.invalidate()
+
+    @property
+    def done(self) -> bool:
+        """Whether a counter has been completed.
+
+        Done counter have been stopped (see stopped) and removed depending on
+        remove_when_done value.
+
+        Contrast this with stopped. A stopped counter may be terminated before
+        100% completion. A done counter has reached its 100% completion.
+        """
+        return self._done
+
+    @done.setter
+    def done(self, value: bool) -> None:
+        self._done = value
+        self.stopped = value
+
+        if value and self.remove_when_done:
+            self.progress_bar.counters.remove(self)
+
+    @property
+    def stopped(self) -> bool:
+        """Whether a counter has been stopped.
+
+        Stopped counters no longer have increasing time_elapsed. This distinction is
+        also used to prevent the Bar formatter with unknown totals from continuing to run.
+
+        A stopped counter (but not done) can be used to signal that a given counter has
+        encountered an error but allows other counters to continue
+        (e.g. download X of Y failed). Given how only done counters are removed
+        (see remove_when_done) this can help aggregate failures from a large number of
+        successes.
+
+        Contrast this with done. A done counter has reached its 100% completion.
+        A stopped counter may be terminated before 100% completion.
+        """
+        return self.stop_time is not None
+
+    @stopped.setter
+    def stopped(self, value: bool) -> None:
+        if value:
+            # This counter has not already been stopped.
+            if not self.stop_time:
+                self.stop_time = datetime.datetime.now()
+        else:
+            # Clearing any previously set stop_time.
+            self.stop_time = None
+
+    @property
+    def percentage(self) -> float:
+        if self.total is None:
+            return 0
+        else:
+            return self.items_completed * 100 / max(self.total, 1)
+
+    @property
+    def time_elapsed(self) -> datetime.timedelta:
+        """
+        Return how much time has been elapsed since the start.
+        """
+        if self.stop_time is None:
+            return datetime.datetime.now() - self.start_time
+        else:
+            return self.stop_time - self.start_time
+
+    @property
+    def time_left(self) -> Optional[datetime.timedelta]:
+        """
+        Timedelta representing the time left.
+        """
+        if self.total is None or not self.percentage:
+            return None
+        elif self.done or self.stopped:
+            return datetime.timedelta(0)
+        else:
+            return self.time_elapsed * (100 - self.percentage) / self.percentage
diff --git a/src/prompt_toolkit/shortcuts/progress_bar/formatters.py b/src/prompt_toolkit/shortcuts/progress_bar/formatters.py
new file mode 100644
index 0000000..1383d7a
--- /dev/null
+++ b/src/prompt_toolkit/shortcuts/progress_bar/formatters.py
@@ -0,0 +1,436 @@
+"""
+Formatter classes for the progress bar.
+Each progress bar consists of a list of these formatters.
+"""
+import datetime
+import time
+from abc import ABCMeta, abstractmethod
+from typing import TYPE_CHECKING, List, Tuple
+
+from prompt_toolkit.formatted_text import (
+    HTML,
+    AnyFormattedText,
+    StyleAndTextTuples,
+    to_formatted_text,
+)
+from prompt_toolkit.formatted_text.utils import fragment_list_width
+from prompt_toolkit.layout.dimension import AnyDimension, D
+from prompt_toolkit.layout.utils import explode_text_fragments
+from prompt_toolkit.utils import get_cwidth
+
+if TYPE_CHECKING:
+    from .base import ProgressBar, ProgressBarCounter
+
+__all__ = [
+    "Formatter",
+    "Text",
+    "Label",
+    "Percentage",
+    "Bar",
+    "Progress",
+    "TimeElapsed",
+    "TimeLeft",
+    "IterationsPerSecond",
+    "SpinningWheel",
+    "Rainbow",
+    "create_default_formatters",
+]
+
+
+class Formatter(metaclass=ABCMeta):
+    """
+    Base class for any formatter.
+    """
+
+    @abstractmethod
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+        pass
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        return D()
+
+
+class Text(Formatter):
+    """
+    Display plain text.
+    """
+
+    def __init__(self, text: AnyFormattedText, style: str = "") -> None:
+        self.text = to_formatted_text(text, style=style)
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+        return self.text
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        return fragment_list_width(self.text)
+
+
+class Label(Formatter):
+    """
+    Display the name of the current task.
+
+    :param width: If a `width` is given, use this width. Scroll the text if it
+        doesn't fit in this width.
+    :param suffix: String suffix to be added after the task name, e.g. ': '.
+        If no task name was given, no suffix will be added.
+    """
+
+    def __init__(self, width: AnyDimension = None, suffix: str = "") -> None:
+        self.width = width
+        self.suffix = suffix
+
+    def _add_suffix(self, label: AnyFormattedText) -> StyleAndTextTuples:
+        label = to_formatted_text(label, style="class:label")
+        return label + [("", self.suffix)]
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        label = self._add_suffix(progress.label)
+        cwidth = fragment_list_width(label)
+
+        if cwidth > width:
+            # It doesn't fit -> scroll task name.
+            label = explode_text_fragments(label)
+            max_scroll = cwidth - width
+            current_scroll = int(time.time() * 3 % max_scroll)
+            label = label[current_scroll:]
+
+        return label
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        if self.width:
+            return self.width
+
+        all_labels = [self._add_suffix(c.label) for c in progress_bar.counters]
+        if all_labels:
+            max_widths = max(fragment_list_width(l) for l in all_labels)
+            return D(preferred=max_widths, max=max_widths)
+        else:
+            return D()
+
+
+class Percentage(Formatter):
+    """
+    Display the progress as a percentage.
+    """
+
+    template = "<percentage>{percentage:>5}%</percentage>"
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        return HTML(self.template).format(percentage=round(progress.percentage, 1))
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        return D.exact(6)
+
+
+class Bar(Formatter):
+    """
+    Display the progress bar itself.
+    """
+
+    template = "<bar>{start}<bar-a>{bar_a}</bar-a><bar-b>{bar_b}</bar-b><bar-c>{bar_c}</bar-c>{end}</bar>"
+
+    def __init__(
+        self,
+        start: str = "[",
+        end: str = "]",
+        sym_a: str = "=",
+        sym_b: str = ">",
+        sym_c: str = " ",
+        unknown: str = "#",
+    ) -> None:
+
+        assert len(sym_a) == 1 and get_cwidth(sym_a) == 1
+        assert len(sym_c) == 1 and get_cwidth(sym_c) == 1
+
+        self.start = start
+        self.end = end
+        self.sym_a = sym_a
+        self.sym_b = sym_b
+        self.sym_c = sym_c
+        self.unknown = unknown
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+        if progress.done or progress.total or progress.stopped:
+            sym_a, sym_b, sym_c = self.sym_a, self.sym_b, self.sym_c
+
+            # Compute pb_a based on done, total, or stopped states.
+            if progress.done:
+                # 100% completed irrelevant of how much was actually marked as completed.
+                percent = 1.0
+            else:
+                # Show percentage completed.
+                percent = progress.percentage / 100
+        else:
+            # Total is unknown and bar is still running.
+            sym_a, sym_b, sym_c = self.sym_c, self.unknown, self.sym_c
+
+            # Compute percent based on the time.
+            percent = time.time() * 20 % 100 / 100
+
+        # Subtract left, sym_b, and right.
+        width -= get_cwidth(self.start + sym_b + self.end)
+
+        # Scale percent by width
+        pb_a = int(percent * width)
+        bar_a = sym_a * pb_a
+        bar_b = sym_b
+        bar_c = sym_c * (width - pb_a)
+
+        return HTML(self.template).format(
+            start=self.start, end=self.end, bar_a=bar_a, bar_b=bar_b, bar_c=bar_c
+        )
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        return D(min=9)
+
+
+class Progress(Formatter):
+    """
+    Display the progress as text.  E.g. "8/20"
+    """
+
+    template = "<current>{current:>3}</current>/<total>{total:>3}</total>"
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        return HTML(self.template).format(
+            current=progress.items_completed, total=progress.total or "?"
+        )
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        all_lengths = [
+            len("{:>3}".format(c.total or "?")) for c in progress_bar.counters
+        ]
+        all_lengths.append(1)
+        return D.exact(max(all_lengths) * 2 + 1)
+
+
+def _format_timedelta(timedelta: datetime.timedelta) -> str:
+    """
+    Return hh:mm:ss, or mm:ss if the amount of hours is zero.
+    """
+    result = f"{timedelta}".split(".")[0]
+    if result.startswith("0:"):
+        result = result[2:]
+    return result
+
+
+class TimeElapsed(Formatter):
+    """
+    Display the elapsed time.
+    """
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        text = _format_timedelta(progress.time_elapsed).rjust(width)
+        return HTML("<time-elapsed>{time_elapsed}</time-elapsed>").format(
+            time_elapsed=text
+        )
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        all_values = [
+            len(_format_timedelta(c.time_elapsed)) for c in progress_bar.counters
+        ]
+        if all_values:
+            return max(all_values)
+        return 0
+
+
+class TimeLeft(Formatter):
+    """
+    Display the time left.
+    """
+
+    template = "<time-left>{time_left}</time-left>"
+    unknown = "?:??:??"
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        time_left = progress.time_left
+        if time_left is not None:
+            formatted_time_left = _format_timedelta(time_left)
+        else:
+            formatted_time_left = self.unknown
+
+        return HTML(self.template).format(time_left=formatted_time_left.rjust(width))
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        all_values = [
+            len(_format_timedelta(c.time_left)) if c.time_left is not None else 7
+            for c in progress_bar.counters
+        ]
+        if all_values:
+            return max(all_values)
+        return 0
+
+
+class IterationsPerSecond(Formatter):
+    """
+    Display the iterations per second.
+    """
+
+    template = (
+        "<iterations-per-second>{iterations_per_second:.2f}</iterations-per-second>"
+    )
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        value = progress.items_completed / progress.time_elapsed.total_seconds()
+        return HTML(self.template.format(iterations_per_second=value))
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        all_values = [
+            len(f"{c.items_completed / c.time_elapsed.total_seconds():.2f}")
+            for c in progress_bar.counters
+        ]
+        if all_values:
+            return max(all_values)
+        return 0
+
+
+class SpinningWheel(Formatter):
+    """
+    Display a spinning wheel.
+    """
+
+    characters = r"/-\|"
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        index = int(time.time() * 3) % len(self.characters)
+        return HTML("<spinning-wheel>{0}</spinning-wheel>").format(
+            self.characters[index]
+        )
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        return D.exact(1)
+
+
+def _hue_to_rgb(hue: float) -> Tuple[int, int, int]:
+    """
+    Take hue between 0 and 1, return (r, g, b).
+    """
+    i = int(hue * 6.0)
+    f = (hue * 6.0) - i
+
+    q = int(255 * (1.0 - f))
+    t = int(255 * (1.0 - (1.0 - f)))
+
+    i %= 6
+
+    return [
+        (255, t, 0),
+        (q, 255, 0),
+        (0, 255, t),
+        (0, q, 255),
+        (t, 0, 255),
+        (255, 0, q),
+    ][i]
+
+
+class Rainbow(Formatter):
+    """
+    For the fun. Add rainbow colors to any of the other formatters.
+    """
+
+    colors = ["#%.2x%.2x%.2x" % _hue_to_rgb(h / 100.0) for h in range(0, 100)]
+
+    def __init__(self, formatter: Formatter) -> None:
+        self.formatter = formatter
+
+    def format(
+        self,
+        progress_bar: "ProgressBar",
+        progress: "ProgressBarCounter[object]",
+        width: int,
+    ) -> AnyFormattedText:
+
+        # Get formatted text from nested formatter, and explode it in
+        # text/style tuples.
+        result = self.formatter.format(progress_bar, progress, width)
+        result = explode_text_fragments(to_formatted_text(result))
+
+        # Insert colors.
+        result2: StyleAndTextTuples = []
+        shift = int(time.time() * 3) % len(self.colors)
+
+        for i, (style, text, *_) in enumerate(result):
+            result2.append(
+                (style + " " + self.colors[(i + shift) % len(self.colors)], text)
+            )
+        return result2
+
+    def get_width(self, progress_bar: "ProgressBar") -> AnyDimension:
+        return self.formatter.get_width(progress_bar)
+
+
+def create_default_formatters() -> List[Formatter]:
+    """
+    Return the list of default formatters.
+    """
+    return [
+        Label(),
+        Text(" "),
+        Percentage(),
+        Text(" "),
+        Bar(),
+        Text(" "),
+        Progress(),
+        Text(" "),
+        Text("eta [", style="class:time-left"),
+        TimeLeft(),
+        Text("]", style="class:time-left"),
+        Text(" "),
+    ]
diff --git a/src/prompt_toolkit/shortcuts/prompt.py b/src/prompt_toolkit/shortcuts/prompt.py
new file mode 100644
index 0000000..4dc1b18
--- /dev/null
+++ b/src/prompt_toolkit/shortcuts/prompt.py
@@ -0,0 +1,1504 @@
+"""
+Line editing functionality.
+---------------------------
+
+This provides a UI for a line input, similar to GNU Readline, libedit and
+linenoise.
+
+Either call the `prompt` function for every line input. Or create an instance
+of the :class:`.PromptSession` class and call the `prompt` method from that
+class. In the second case, we'll have a 'session' that keeps all the state like
+the history in between several calls.
+
+There is a lot of overlap between the arguments taken by the `prompt` function
+and the `PromptSession` (like `completer`, `style`, etcetera). There we have
+the freedom to decide which settings we want for the whole 'session', and which
+we want for an individual `prompt`.
+
+Example::
+
+        # Simple `prompt` call.
+        result = prompt('Say something: ')
+
+        # Using a 'session'.
+        s = PromptSession()
+        result = s.prompt('Say something: ')
+"""
+from contextlib import contextmanager
+from enum import Enum
+from functools import partial
+from typing import (
+    TYPE_CHECKING,
+    Callable,
+    Generic,
+    Iterator,
+    List,
+    Optional,
+    Tuple,
+    TypeVar,
+    Union,
+    cast,
+)
+
+from prompt_toolkit.application import Application
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.auto_suggest import AutoSuggest, DynamicAutoSuggest
+from prompt_toolkit.buffer import Buffer
+from prompt_toolkit.clipboard import Clipboard, DynamicClipboard, InMemoryClipboard
+from prompt_toolkit.completion import Completer, DynamicCompleter, ThreadedCompleter
+from prompt_toolkit.cursor_shapes import (
+    AnyCursorShapeConfig,
+    CursorShapeConfig,
+    DynamicCursorShapeConfig,
+)
+from prompt_toolkit.document import Document
+from prompt_toolkit.enums import DEFAULT_BUFFER, SEARCH_BUFFER, EditingMode
+from prompt_toolkit.eventloop import get_event_loop
+from prompt_toolkit.filters import (
+    Condition,
+    FilterOrBool,
+    has_arg,
+    has_focus,
+    is_done,
+    is_true,
+    renderer_height_is_known,
+    to_filter,
+)
+from prompt_toolkit.formatted_text import (
+    AnyFormattedText,
+    StyleAndTextTuples,
+    fragment_list_to_text,
+    merge_formatted_text,
+    to_formatted_text,
+)
+from prompt_toolkit.history import History, InMemoryHistory
+from prompt_toolkit.input.base import Input
+from prompt_toolkit.key_binding.bindings.auto_suggest import load_auto_suggest_bindings
+from prompt_toolkit.key_binding.bindings.completion import (
+    display_completions_like_readline,
+)
+from prompt_toolkit.key_binding.bindings.open_in_editor import (
+    load_open_in_editor_bindings,
+)
+from prompt_toolkit.key_binding.key_bindings import (
+    ConditionalKeyBindings,
+    DynamicKeyBindings,
+    KeyBindings,
+    KeyBindingsBase,
+    merge_key_bindings,
+)
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.layout import Float, FloatContainer, HSplit, Window
+from prompt_toolkit.layout.containers import ConditionalContainer, WindowAlign
+from prompt_toolkit.layout.controls import (
+    BufferControl,
+    FormattedTextControl,
+    SearchBufferControl,
+)
+from prompt_toolkit.layout.dimension import Dimension
+from prompt_toolkit.layout.layout import Layout
+from prompt_toolkit.layout.menus import CompletionsMenu, MultiColumnCompletionsMenu
+from prompt_toolkit.layout.processors import (
+    AfterInput,
+    AppendAutoSuggestion,
+    ConditionalProcessor,
+    DisplayMultipleCursors,
+    DynamicProcessor,
+    HighlightIncrementalSearchProcessor,
+    HighlightSelectionProcessor,
+    PasswordProcessor,
+    Processor,
+    ReverseSearchProcessor,
+    merge_processors,
+)
+from prompt_toolkit.layout.utils import explode_text_fragments
+from prompt_toolkit.lexers import DynamicLexer, Lexer
+from prompt_toolkit.output import ColorDepth, DummyOutput, Output
+from prompt_toolkit.styles import (
+    BaseStyle,
+    ConditionalStyleTransformation,
+    DynamicStyle,
+    DynamicStyleTransformation,
+    StyleTransformation,
+    SwapLightAndDarkStyleTransformation,
+    merge_style_transformations,
+)
+from prompt_toolkit.utils import (
+    get_cwidth,
+    is_dumb_terminal,
+    suspend_to_background_supported,
+    to_str,
+)
+from prompt_toolkit.validation import DynamicValidator, Validator
+from prompt_toolkit.widgets.toolbars import (
+    SearchToolbar,
+    SystemToolbar,
+    ValidationToolbar,
+)
+
+if TYPE_CHECKING:
+    from prompt_toolkit.formatted_text.base import MagicFormattedText
+
+__all__ = [
+    "PromptSession",
+    "prompt",
+    "confirm",
+    "create_confirm_session",  # Used by '_display_completions_like_readline'.
+    "CompleteStyle",
+]
+
+_StyleAndTextTuplesCallable = Callable[[], StyleAndTextTuples]
+E = KeyPressEvent
+
+
+def _split_multiline_prompt(
+    get_prompt_text: _StyleAndTextTuplesCallable,
+) -> Tuple[
+    Callable[[], bool], _StyleAndTextTuplesCallable, _StyleAndTextTuplesCallable
+]:
+    """
+    Take a `get_prompt_text` function and return three new functions instead.
+    One that tells whether this prompt consists of multiple lines; one that
+    returns the fragments to be shown on the lines above the input; and another
+    one with the fragments to be shown at the first line of the input.
+    """
+
+    def has_before_fragments() -> bool:
+        for fragment, char, *_ in get_prompt_text():
+            if "\n" in char:
+                return True
+        return False
+
+    def before() -> StyleAndTextTuples:
+        result: StyleAndTextTuples = []
+        found_nl = False
+        for fragment, char, *_ in reversed(explode_text_fragments(get_prompt_text())):
+            if found_nl:
+                result.insert(0, (fragment, char))
+            elif char == "\n":
+                found_nl = True
+        return result
+
+    def first_input_line() -> StyleAndTextTuples:
+        result: StyleAndTextTuples = []
+        for fragment, char, *_ in reversed(explode_text_fragments(get_prompt_text())):
+            if char == "\n":
+                break
+            else:
+                result.insert(0, (fragment, char))
+        return result
+
+    return has_before_fragments, before, first_input_line
+
+
+class _RPrompt(Window):
+    """
+    The prompt that is displayed on the right side of the Window.
+    """
+
+    def __init__(self, text: AnyFormattedText) -> None:
+        super().__init__(
+            FormattedTextControl(text=text),
+            align=WindowAlign.RIGHT,
+            style="class:rprompt",
+        )
+
+
+class CompleteStyle(str, Enum):
+    """
+    How to display autocompletions for the prompt.
+    """
+
+    value: str
+
+    COLUMN = "COLUMN"
+    MULTI_COLUMN = "MULTI_COLUMN"
+    READLINE_LIKE = "READLINE_LIKE"
+
+
+# Formatted text for the continuation prompt. It's the same like other
+# formatted text, except that if it's a callable, it takes three arguments.
+PromptContinuationText = Union[
+    str,
+    "MagicFormattedText",
+    StyleAndTextTuples,
+    # (prompt_width, line_number, wrap_count) -> AnyFormattedText.
+    Callable[[int, int, int], AnyFormattedText],
+]
+
+_T = TypeVar("_T")
+
+
+class PromptSession(Generic[_T]):
+    """
+    PromptSession for a prompt application, which can be used as a GNU Readline
+    replacement.
+
+    This is a wrapper around a lot of ``prompt_toolkit`` functionality and can
+    be a replacement for `raw_input`.
+
+    All parameters that expect "formatted text" can take either just plain text
+    (a unicode object), a list of ``(style_str, text)`` tuples or an HTML object.
+
+    Example usage::
+
+        s = PromptSession(message='>')
+        text = s.prompt()
+
+    :param message: Plain text or formatted text to be shown before the prompt.
+        This can also be a callable that returns formatted text.
+    :param multiline: `bool` or :class:`~prompt_toolkit.filters.Filter`.
+        When True, prefer a layout that is more adapted for multiline input.
+        Text after newlines is automatically indented, and search/arg input is
+        shown below the input, instead of replacing the prompt.
+    :param wrap_lines: `bool` or :class:`~prompt_toolkit.filters.Filter`.
+        When True (the default), automatically wrap long lines instead of
+        scrolling horizontally.
+    :param is_password: Show asterisks instead of the actual typed characters.
+    :param editing_mode: ``EditingMode.VI`` or ``EditingMode.EMACS``.
+    :param vi_mode: `bool`, if True, Identical to ``editing_mode=EditingMode.VI``.
+    :param complete_while_typing: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. Enable autocompletion while
+        typing.
+    :param validate_while_typing: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. Enable input validation while
+        typing.
+    :param enable_history_search: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. Enable up-arrow parting
+        string matching.
+    :param search_ignore_case:
+        :class:`~prompt_toolkit.filters.Filter`. Search case insensitive.
+    :param lexer: :class:`~prompt_toolkit.lexers.Lexer` to be used for the
+        syntax highlighting.
+    :param validator: :class:`~prompt_toolkit.validation.Validator` instance
+        for input validation.
+    :param completer: :class:`~prompt_toolkit.completion.Completer` instance
+        for input completion.
+    :param complete_in_thread: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. Run the completer code in a
+        background thread in order to avoid blocking the user interface.
+        For ``CompleteStyle.READLINE_LIKE``, this setting has no effect. There
+        we always run the completions in the main thread.
+    :param reserve_space_for_menu: Space to be reserved for displaying the menu.
+        (0 means that no space needs to be reserved.)
+    :param auto_suggest: :class:`~prompt_toolkit.auto_suggest.AutoSuggest`
+        instance for input suggestions.
+    :param style: :class:`.Style` instance for the color scheme.
+    :param include_default_pygments_style: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. Tell whether the default
+        styling for Pygments lexers has to be included. By default, this is
+        true, but it is recommended to be disabled if another Pygments style is
+        passed as the `style` argument, otherwise, two Pygments styles will be
+        merged.
+    :param style_transformation:
+        :class:`~prompt_toolkit.style.StyleTransformation` instance.
+    :param swap_light_and_dark_colors: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. When enabled, apply
+        :class:`~prompt_toolkit.style.SwapLightAndDarkStyleTransformation`.
+        This is useful for switching between dark and light terminal
+        backgrounds.
+    :param enable_system_prompt: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. Pressing Meta+'!' will show
+        a system prompt.
+    :param enable_suspend: `bool` or :class:`~prompt_toolkit.filters.Filter`.
+        Enable Control-Z style suspension.
+    :param enable_open_in_editor: `bool` or
+        :class:`~prompt_toolkit.filters.Filter`. Pressing 'v' in Vi mode or
+        C-X C-E in emacs mode will open an external editor.
+    :param history: :class:`~prompt_toolkit.history.History` instance.
+    :param clipboard: :class:`~prompt_toolkit.clipboard.Clipboard` instance.
+        (e.g. :class:`~prompt_toolkit.clipboard.InMemoryClipboard`)
+    :param rprompt: Text or formatted text to be displayed on the right side.
+        This can also be a callable that returns (formatted) text.
+    :param bottom_toolbar: Formatted text or callable which is supposed to
+        return formatted text.
+    :param prompt_continuation: Text that needs to be displayed for a multiline
+        prompt continuation. This can either be formatted text or a callable
+        that takes a `prompt_width`, `line_number` and `wrap_count` as input
+        and returns formatted text. When this is `None` (the default), then
+        `prompt_width` spaces will be used.
+    :param complete_style: ``CompleteStyle.COLUMN``,
+        ``CompleteStyle.MULTI_COLUMN`` or ``CompleteStyle.READLINE_LIKE``.
+    :param mouse_support: `bool` or :class:`~prompt_toolkit.filters.Filter`
+        to enable mouse support.
+    :param placeholder: Text to be displayed when no input has been given
+        yet. Unlike the `default` parameter, this won't be returned as part of
+        the output ever. This can be formatted text or a callable that returns
+        formatted text.
+    :param refresh_interval: (number; in seconds) When given, refresh the UI
+        every so many seconds.
+    :param input: `Input` object. (Note that the preferred way to change the
+        input/output is by creating an `AppSession`.)
+    :param output: `Output` object.
+    """
+
+    _fields = (
+        "message",
+        "lexer",
+        "completer",
+        "complete_in_thread",
+        "is_password",
+        "editing_mode",
+        "key_bindings",
+        "is_password",
+        "bottom_toolbar",
+        "style",
+        "style_transformation",
+        "swap_light_and_dark_colors",
+        "color_depth",
+        "cursor",
+        "include_default_pygments_style",
+        "rprompt",
+        "multiline",
+        "prompt_continuation",
+        "wrap_lines",
+        "enable_history_search",
+        "search_ignore_case",
+        "complete_while_typing",
+        "validate_while_typing",
+        "complete_style",
+        "mouse_support",
+        "auto_suggest",
+        "clipboard",
+        "validator",
+        "refresh_interval",
+        "input_processors",
+        "placeholder",
+        "enable_system_prompt",
+        "enable_suspend",
+        "enable_open_in_editor",
+        "reserve_space_for_menu",
+        "tempfile_suffix",
+        "tempfile",
+    )
+
+    def __init__(
+        self,
+        message: AnyFormattedText = "",
+        *,
+        multiline: FilterOrBool = False,
+        wrap_lines: FilterOrBool = True,
+        is_password: FilterOrBool = False,
+        vi_mode: bool = False,
+        editing_mode: EditingMode = EditingMode.EMACS,
+        complete_while_typing: FilterOrBool = True,
+        validate_while_typing: FilterOrBool = True,
+        enable_history_search: FilterOrBool = False,
+        search_ignore_case: FilterOrBool = False,
+        lexer: Optional[Lexer] = None,
+        enable_system_prompt: FilterOrBool = False,
+        enable_suspend: FilterOrBool = False,
+        enable_open_in_editor: FilterOrBool = False,
+        validator: Optional[Validator] = None,
+        completer: Optional[Completer] = None,
+        complete_in_thread: bool = False,
+        reserve_space_for_menu: int = 8,
+        complete_style: CompleteStyle = CompleteStyle.COLUMN,
+        auto_suggest: Optional[AutoSuggest] = None,
+        style: Optional[BaseStyle] = None,
+        style_transformation: Optional[StyleTransformation] = None,
+        swap_light_and_dark_colors: FilterOrBool = False,
+        color_depth: Optional[ColorDepth] = None,
+        cursor: AnyCursorShapeConfig = None,
+        include_default_pygments_style: FilterOrBool = True,
+        history: Optional[History] = None,
+        clipboard: Optional[Clipboard] = None,
+        prompt_continuation: Optional[PromptContinuationText] = None,
+        rprompt: AnyFormattedText = None,
+        bottom_toolbar: AnyFormattedText = None,
+        mouse_support: FilterOrBool = False,
+        input_processors: Optional[List[Processor]] = None,
+        placeholder: Optional[AnyFormattedText] = None,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        erase_when_done: bool = False,
+        tempfile_suffix: Optional[Union[str, Callable[[], str]]] = ".txt",
+        tempfile: Optional[Union[str, Callable[[], str]]] = None,
+        refresh_interval: float = 0,
+        input: Optional[Input] = None,
+        output: Optional[Output] = None,
+    ) -> None:
+
+        history = history or InMemoryHistory()
+        clipboard = clipboard or InMemoryClipboard()
+
+        # Ensure backwards-compatibility, when `vi_mode` is passed.
+        if vi_mode:
+            editing_mode = EditingMode.VI
+
+        # Store all settings in this class.
+        self._input = input
+        self._output = output
+
+        # Store attributes.
+        # (All except 'editing_mode'.)
+        self.message = message
+        self.lexer = lexer
+        self.completer = completer
+        self.complete_in_thread = complete_in_thread
+        self.is_password = is_password
+        self.key_bindings = key_bindings
+        self.bottom_toolbar = bottom_toolbar
+        self.style = style
+        self.style_transformation = style_transformation
+        self.swap_light_and_dark_colors = swap_light_and_dark_colors
+        self.color_depth = color_depth
+        self.cursor = cursor
+        self.include_default_pygments_style = include_default_pygments_style
+        self.rprompt = rprompt
+        self.multiline = multiline
+        self.prompt_continuation = prompt_continuation
+        self.wrap_lines = wrap_lines
+        self.enable_history_search = enable_history_search
+        self.search_ignore_case = search_ignore_case
+        self.complete_while_typing = complete_while_typing
+        self.validate_while_typing = validate_while_typing
+        self.complete_style = complete_style
+        self.mouse_support = mouse_support
+        self.auto_suggest = auto_suggest
+        self.clipboard = clipboard
+        self.validator = validator
+        self.refresh_interval = refresh_interval
+        self.input_processors = input_processors
+        self.placeholder = placeholder
+        self.enable_system_prompt = enable_system_prompt
+        self.enable_suspend = enable_suspend
+        self.enable_open_in_editor = enable_open_in_editor
+        self.reserve_space_for_menu = reserve_space_for_menu
+        self.tempfile_suffix = tempfile_suffix
+        self.tempfile = tempfile
+
+        # Create buffers, layout and Application.
+        self.history = history
+        self.default_buffer = self._create_default_buffer()
+        self.search_buffer = self._create_search_buffer()
+        self.layout = self._create_layout()
+        self.app = self._create_application(editing_mode, erase_when_done)
+
+    def _dyncond(self, attr_name: str) -> Condition:
+        """
+        Dynamically take this setting from this 'PromptSession' class.
+        `attr_name` represents an attribute name of this class. Its value
+        can either be a boolean or a `Filter`.
+
+        This returns something that can be used as either a `Filter`
+        or `Filter`.
+        """
+
+        @Condition
+        def dynamic() -> bool:
+            value = cast(FilterOrBool, getattr(self, attr_name))
+            return to_filter(value)()
+
+        return dynamic
+
+    def _create_default_buffer(self) -> Buffer:
+        """
+        Create and return the default input buffer.
+        """
+        dyncond = self._dyncond
+
+        # Create buffers list.
+        def accept(buff: Buffer) -> bool:
+            """Accept the content of the default buffer. This is called when
+            the validation succeeds."""
+            cast(Application[str], get_app()).exit(result=buff.document.text)
+            return True  # Keep text, we call 'reset' later on.
+
+        return Buffer(
+            name=DEFAULT_BUFFER,
+            # Make sure that complete_while_typing is disabled when
+            # enable_history_search is enabled. (First convert to Filter,
+            # to avoid doing bitwise operations on bool objects.)
+            complete_while_typing=Condition(
+                lambda: is_true(self.complete_while_typing)
+                and not is_true(self.enable_history_search)
+                and not self.complete_style == CompleteStyle.READLINE_LIKE
+            ),
+            validate_while_typing=dyncond("validate_while_typing"),
+            enable_history_search=dyncond("enable_history_search"),
+            validator=DynamicValidator(lambda: self.validator),
+            completer=DynamicCompleter(
+                lambda: ThreadedCompleter(self.completer)
+                if self.complete_in_thread and self.completer
+                else self.completer
+            ),
+            history=self.history,
+            auto_suggest=DynamicAutoSuggest(lambda: self.auto_suggest),
+            accept_handler=accept,
+            tempfile_suffix=lambda: to_str(self.tempfile_suffix or ""),
+            tempfile=lambda: to_str(self.tempfile or ""),
+        )
+
+    def _create_search_buffer(self) -> Buffer:
+        return Buffer(name=SEARCH_BUFFER)
+
+    def _create_layout(self) -> Layout:
+        """
+        Create `Layout` for this prompt.
+        """
+        dyncond = self._dyncond
+
+        # Create functions that will dynamically split the prompt. (If we have
+        # a multiline prompt.)
+        (
+            has_before_fragments,
+            get_prompt_text_1,
+            get_prompt_text_2,
+        ) = _split_multiline_prompt(self._get_prompt)
+
+        default_buffer = self.default_buffer
+        search_buffer = self.search_buffer
+
+        # Create processors list.
+        @Condition
+        def display_placeholder() -> bool:
+            return self.placeholder is not None and self.default_buffer.text == ""
+
+        all_input_processors = [
+            HighlightIncrementalSearchProcessor(),
+            HighlightSelectionProcessor(),
+            ConditionalProcessor(
+                AppendAutoSuggestion(), has_focus(default_buffer) & ~is_done
+            ),
+            ConditionalProcessor(PasswordProcessor(), dyncond("is_password")),
+            DisplayMultipleCursors(),
+            # Users can insert processors here.
+            DynamicProcessor(lambda: merge_processors(self.input_processors or [])),
+            ConditionalProcessor(
+                AfterInput(lambda: self.placeholder),
+                filter=display_placeholder,
+            ),
+        ]
+
+        # Create bottom toolbars.
+        bottom_toolbar = ConditionalContainer(
+            Window(
+                FormattedTextControl(
+                    lambda: self.bottom_toolbar, style="class:bottom-toolbar.text"
+                ),
+                style="class:bottom-toolbar",
+                dont_extend_height=True,
+                height=Dimension(min=1),
+            ),
+            filter=~is_done
+            & renderer_height_is_known
+            & Condition(lambda: self.bottom_toolbar is not None),
+        )
+
+        search_toolbar = SearchToolbar(
+            search_buffer, ignore_case=dyncond("search_ignore_case")
+        )
+
+        search_buffer_control = SearchBufferControl(
+            buffer=search_buffer,
+            input_processors=[ReverseSearchProcessor()],
+            ignore_case=dyncond("search_ignore_case"),
+        )
+
+        system_toolbar = SystemToolbar(
+            enable_global_bindings=dyncond("enable_system_prompt")
+        )
+
+        def get_search_buffer_control() -> SearchBufferControl:
+            "Return the UIControl to be focused when searching start."
+            if is_true(self.multiline):
+                return search_toolbar.control
+            else:
+                return search_buffer_control
+
+        default_buffer_control = BufferControl(
+            buffer=default_buffer,
+            search_buffer_control=get_search_buffer_control,
+            input_processors=all_input_processors,
+            include_default_input_processors=False,
+            lexer=DynamicLexer(lambda: self.lexer),
+            preview_search=True,
+        )
+
+        default_buffer_window = Window(
+            default_buffer_control,
+            height=self._get_default_buffer_control_height,
+            get_line_prefix=partial(
+                self._get_line_prefix, get_prompt_text_2=get_prompt_text_2
+            ),
+            wrap_lines=dyncond("wrap_lines"),
+        )
+
+        @Condition
+        def multi_column_complete_style() -> bool:
+            return self.complete_style == CompleteStyle.MULTI_COLUMN
+
+        # Build the layout.
+        layout = HSplit(
+            [
+                # The main input, with completion menus floating on top of it.
+                FloatContainer(
+                    HSplit(
+                        [
+                            ConditionalContainer(
+                                Window(
+                                    FormattedTextControl(get_prompt_text_1),
+                                    dont_extend_height=True,
+                                ),
+                                Condition(has_before_fragments),
+                            ),
+                            ConditionalContainer(
+                                default_buffer_window,
+                                Condition(
+                                    lambda: get_app().layout.current_control
+                                    != search_buffer_control
+                                ),
+                            ),
+                            ConditionalContainer(
+                                Window(search_buffer_control),
+                                Condition(
+                                    lambda: get_app().layout.current_control
+                                    == search_buffer_control
+                                ),
+                            ),
+                        ]
+                    ),
+                    [
+                        # Completion menus.
+                        # NOTE: Especially the multi-column menu needs to be
+                        #       transparent, because the shape is not always
+                        #       rectangular due to the meta-text below the menu.
+                        Float(
+                            xcursor=True,
+                            ycursor=True,
+                            transparent=True,
+                            content=CompletionsMenu(
+                                max_height=16,
+                                scroll_offset=1,
+                                extra_filter=has_focus(default_buffer)
+                                & ~multi_column_complete_style,
+                            ),
+                        ),
+                        Float(
+                            xcursor=True,
+                            ycursor=True,
+                            transparent=True,
+                            content=MultiColumnCompletionsMenu(
+                                show_meta=True,
+                                extra_filter=has_focus(default_buffer)
+                                & multi_column_complete_style,
+                            ),
+                        ),
+                        # The right prompt.
+                        Float(
+                            right=0,
+                            bottom=0,
+                            hide_when_covering_content=True,
+                            content=_RPrompt(lambda: self.rprompt),
+                        ),
+                    ],
+                ),
+                ConditionalContainer(ValidationToolbar(), filter=~is_done),
+                ConditionalContainer(
+                    system_toolbar, dyncond("enable_system_prompt") & ~is_done
+                ),
+                # In multiline mode, we use two toolbars for 'arg' and 'search'.
+                ConditionalContainer(
+                    Window(FormattedTextControl(self._get_arg_text), height=1),
+                    dyncond("multiline") & has_arg,
+                ),
+                ConditionalContainer(search_toolbar, dyncond("multiline") & ~is_done),
+                bottom_toolbar,
+            ]
+        )
+
+        return Layout(layout, default_buffer_window)
+
+    def _create_application(
+        self, editing_mode: EditingMode, erase_when_done: bool
+    ) -> Application[_T]:
+        """
+        Create the `Application` object.
+        """
+        dyncond = self._dyncond
+
+        # Default key bindings.
+        auto_suggest_bindings = load_auto_suggest_bindings()
+        open_in_editor_bindings = load_open_in_editor_bindings()
+        prompt_bindings = self._create_prompt_bindings()
+
+        # Create application
+        application: Application[_T] = Application(
+            layout=self.layout,
+            style=DynamicStyle(lambda: self.style),
+            style_transformation=merge_style_transformations(
+                [
+                    DynamicStyleTransformation(lambda: self.style_transformation),
+                    ConditionalStyleTransformation(
+                        SwapLightAndDarkStyleTransformation(),
+                        dyncond("swap_light_and_dark_colors"),
+                    ),
+                ]
+            ),
+            include_default_pygments_style=dyncond("include_default_pygments_style"),
+            clipboard=DynamicClipboard(lambda: self.clipboard),
+            key_bindings=merge_key_bindings(
+                [
+                    merge_key_bindings(
+                        [
+                            auto_suggest_bindings,
+                            ConditionalKeyBindings(
+                                open_in_editor_bindings,
+                                dyncond("enable_open_in_editor")
+                                & has_focus(DEFAULT_BUFFER),
+                            ),
+                            prompt_bindings,
+                        ]
+                    ),
+                    DynamicKeyBindings(lambda: self.key_bindings),
+                ]
+            ),
+            mouse_support=dyncond("mouse_support"),
+            editing_mode=editing_mode,
+            erase_when_done=erase_when_done,
+            reverse_vi_search_direction=True,
+            color_depth=lambda: self.color_depth,
+            cursor=DynamicCursorShapeConfig(lambda: self.cursor),
+            refresh_interval=self.refresh_interval,
+            input=self._input,
+            output=self._output,
+        )
+
+        # During render time, make sure that we focus the right search control
+        # (if we are searching). - This could be useful if people make the
+        # 'multiline' property dynamic.
+        """
+        def on_render(app):
+            multiline = is_true(self.multiline)
+            current_control = app.layout.current_control
+
+            if multiline:
+                if current_control == search_buffer_control:
+                    app.layout.current_control = search_toolbar.control
+                    app.invalidate()
+            else:
+                if current_control == search_toolbar.control:
+                    app.layout.current_control = search_buffer_control
+                    app.invalidate()
+
+        app.on_render += on_render
+        """
+
+        return application
+
+    def _create_prompt_bindings(self) -> KeyBindings:
+        """
+        Create the KeyBindings for a prompt application.
+        """
+        kb = KeyBindings()
+        handle = kb.add
+        default_focused = has_focus(DEFAULT_BUFFER)
+
+        @Condition
+        def do_accept() -> bool:
+            return not is_true(self.multiline) and self.app.layout.has_focus(
+                DEFAULT_BUFFER
+            )
+
+        @handle("enter", filter=do_accept & default_focused)
+        def _accept_input(event: E) -> None:
+            "Accept input when enter has been pressed."
+            self.default_buffer.validate_and_handle()
+
+        @Condition
+        def readline_complete_style() -> bool:
+            return self.complete_style == CompleteStyle.READLINE_LIKE
+
+        @handle("tab", filter=readline_complete_style & default_focused)
+        def _complete_like_readline(event: E) -> None:
+            "Display completions (like Readline)."
+            display_completions_like_readline(event)
+
+        @handle("c-c", filter=default_focused)
+        @handle("<sigint>")
+        def _keyboard_interrupt(event: E) -> None:
+            "Abort when Control-C has been pressed."
+            event.app.exit(exception=KeyboardInterrupt, style="class:aborting")
+
+        @Condition
+        def ctrl_d_condition() -> bool:
+            """Ctrl-D binding is only active when the default buffer is selected
+            and empty."""
+            app = get_app()
+            return (
+                app.current_buffer.name == DEFAULT_BUFFER
+                and not app.current_buffer.text
+            )
+
+        @handle("c-d", filter=ctrl_d_condition & default_focused)
+        def _eof(event: E) -> None:
+            "Exit when Control-D has been pressed."
+            event.app.exit(exception=EOFError, style="class:exiting")
+
+        suspend_supported = Condition(suspend_to_background_supported)
+
+        @Condition
+        def enable_suspend() -> bool:
+            return to_filter(self.enable_suspend)()
+
+        @handle("c-z", filter=suspend_supported & enable_suspend)
+        def _suspend(event: E) -> None:
+            """
+            Suspend process to background.
+            """
+            event.app.suspend_to_background()
+
+        return kb
+
+    def prompt(
+        self,
+        # When any of these arguments are passed, this value is overwritten
+        # in this PromptSession.
+        message: Optional[AnyFormattedText] = None,
+        # `message` should go first, because people call it as
+        # positional argument.
+        *,
+        editing_mode: Optional[EditingMode] = None,
+        refresh_interval: Optional[float] = None,
+        vi_mode: Optional[bool] = None,
+        lexer: Optional[Lexer] = None,
+        completer: Optional[Completer] = None,
+        complete_in_thread: Optional[bool] = None,
+        is_password: Optional[bool] = None,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        bottom_toolbar: Optional[AnyFormattedText] = None,
+        style: Optional[BaseStyle] = None,
+        color_depth: Optional[ColorDepth] = None,
+        cursor: Optional[AnyCursorShapeConfig] = None,
+        include_default_pygments_style: Optional[FilterOrBool] = None,
+        style_transformation: Optional[StyleTransformation] = None,
+        swap_light_and_dark_colors: Optional[FilterOrBool] = None,
+        rprompt: Optional[AnyFormattedText] = None,
+        multiline: Optional[FilterOrBool] = None,
+        prompt_continuation: Optional[PromptContinuationText] = None,
+        wrap_lines: Optional[FilterOrBool] = None,
+        enable_history_search: Optional[FilterOrBool] = None,
+        search_ignore_case: Optional[FilterOrBool] = None,
+        complete_while_typing: Optional[FilterOrBool] = None,
+        validate_while_typing: Optional[FilterOrBool] = None,
+        complete_style: Optional[CompleteStyle] = None,
+        auto_suggest: Optional[AutoSuggest] = None,
+        validator: Optional[Validator] = None,
+        clipboard: Optional[Clipboard] = None,
+        mouse_support: Optional[FilterOrBool] = None,
+        input_processors: Optional[List[Processor]] = None,
+        placeholder: Optional[AnyFormattedText] = None,
+        reserve_space_for_menu: Optional[int] = None,
+        enable_system_prompt: Optional[FilterOrBool] = None,
+        enable_suspend: Optional[FilterOrBool] = None,
+        enable_open_in_editor: Optional[FilterOrBool] = None,
+        tempfile_suffix: Optional[Union[str, Callable[[], str]]] = None,
+        tempfile: Optional[Union[str, Callable[[], str]]] = None,
+        # Following arguments are specific to the current `prompt()` call.
+        default: Union[str, Document] = "",
+        accept_default: bool = False,
+        pre_run: Optional[Callable[[], None]] = None,
+        set_exception_handler: bool = True,
+        handle_sigint: bool = True,
+        in_thread: bool = False,
+    ) -> _T:
+        """
+        Display the prompt.
+
+        The first set of arguments is a subset of the :class:`~.PromptSession`
+        class itself. For these, passing in ``None`` will keep the current
+        values that are active in the session. Passing in a value will set the
+        attribute for the session, which means that it applies to the current,
+        but also to the next prompts.
+
+        Note that in order to erase a ``Completer``, ``Validator`` or
+        ``AutoSuggest``, you can't use ``None``. Instead pass in a
+        ``DummyCompleter``, ``DummyValidator`` or ``DummyAutoSuggest`` instance
+        respectively. For a ``Lexer`` you can pass in an empty ``SimpleLexer``.
+
+        Additional arguments, specific for this prompt:
+
+        :param default: The default input text to be shown. (This can be edited
+            by the user).
+        :param accept_default: When `True`, automatically accept the default
+            value without allowing the user to edit the input.
+        :param pre_run: Callable, called at the start of `Application.run`.
+        :param in_thread: Run the prompt in a background thread; block the
+            current thread. This avoids interference with an event loop in the
+            current thread. Like `Application.run(in_thread=True)`.
+
+        This method will raise ``KeyboardInterrupt`` when control-c has been
+        pressed (for abort) and ``EOFError`` when control-d has been pressed
+        (for exit).
+        """
+        # NOTE: We used to create a backup of the PromptSession attributes and
+        #       restore them after exiting the prompt. This code has been
+        #       removed, because it was confusing and didn't really serve a use
+        #       case. (People were changing `Application.editing_mode`
+        #       dynamically and surprised that it was reset after every call.)
+
+        # NOTE 2: YES, this is a lot of repeation below...
+        #         However, it is a very convenient for a user to accept all
+        #         these parameters in this `prompt` method as well. We could
+        #         use `locals()` and `setattr` to avoid the repetition, but
+        #         then we loose the advantage of mypy and pyflakes to be able
+        #         to verify the code.
+        if message is not None:
+            self.message = message
+        if editing_mode is not None:
+            self.editing_mode = editing_mode
+        if refresh_interval is not None:
+            self.refresh_interval = refresh_interval
+        if vi_mode:
+            self.editing_mode = EditingMode.VI
+        if lexer is not None:
+            self.lexer = lexer
+        if completer is not None:
+            self.completer = completer
+        if complete_in_thread is not None:
+            self.complete_in_thread = complete_in_thread
+        if is_password is not None:
+            self.is_password = is_password
+        if key_bindings is not None:
+            self.key_bindings = key_bindings
+        if bottom_toolbar is not None:
+            self.bottom_toolbar = bottom_toolbar
+        if style is not None:
+            self.style = style
+        if color_depth is not None:
+            self.color_depth = color_depth
+        if cursor is not None:
+            self.cursor = cursor
+        if include_default_pygments_style is not None:
+            self.include_default_pygments_style = include_default_pygments_style
+        if style_transformation is not None:
+            self.style_transformation = style_transformation
+        if swap_light_and_dark_colors is not None:
+            self.swap_light_and_dark_colors = swap_light_and_dark_colors
+        if rprompt is not None:
+            self.rprompt = rprompt
+        if multiline is not None:
+            self.multiline = multiline
+        if prompt_continuation is not None:
+            self.prompt_continuation = prompt_continuation
+        if wrap_lines is not None:
+            self.wrap_lines = wrap_lines
+        if enable_history_search is not None:
+            self.enable_history_search = enable_history_search
+        if search_ignore_case is not None:
+            self.search_ignore_case = search_ignore_case
+        if complete_while_typing is not None:
+            self.complete_while_typing = complete_while_typing
+        if validate_while_typing is not None:
+            self.validate_while_typing = validate_while_typing
+        if complete_style is not None:
+            self.complete_style = complete_style
+        if auto_suggest is not None:
+            self.auto_suggest = auto_suggest
+        if validator is not None:
+            self.validator = validator
+        if clipboard is not None:
+            self.clipboard = clipboard
+        if mouse_support is not None:
+            self.mouse_support = mouse_support
+        if input_processors is not None:
+            self.input_processors = input_processors
+        if placeholder is not None:
+            self.placeholder = placeholder
+        if reserve_space_for_menu is not None:
+            self.reserve_space_for_menu = reserve_space_for_menu
+        if enable_system_prompt is not None:
+            self.enable_system_prompt = enable_system_prompt
+        if enable_suspend is not None:
+            self.enable_suspend = enable_suspend
+        if enable_open_in_editor is not None:
+            self.enable_open_in_editor = enable_open_in_editor
+        if tempfile_suffix is not None:
+            self.tempfile_suffix = tempfile_suffix
+        if tempfile is not None:
+            self.tempfile = tempfile
+
+        self._add_pre_run_callables(pre_run, accept_default)
+        self.default_buffer.reset(
+            default if isinstance(default, Document) else Document(default)
+        )
+        self.app.refresh_interval = self.refresh_interval  # This is not reactive.
+
+        # If we are using the default output, and have a dumb terminal. Use the
+        # dumb prompt.
+        if self._output is None and is_dumb_terminal():
+            with self._dumb_prompt(self.message) as dump_app:
+                return dump_app.run(in_thread=in_thread, handle_sigint=handle_sigint)
+
+        return self.app.run(
+            set_exception_handler=set_exception_handler,
+            in_thread=in_thread,
+            handle_sigint=handle_sigint,
+        )
+
+    @contextmanager
+    def _dumb_prompt(self, message: AnyFormattedText = "") -> Iterator[Application[_T]]:
+        """
+        Create prompt `Application` for prompt function for dumb terminals.
+
+        Dumb terminals have minimum rendering capabilities. We can only print
+        text to the screen. We can't use colors, and we can't do cursor
+        movements. The Emacs inferior shell is an example of a dumb terminal.
+
+        We will show the prompt, and wait for the input. We still handle arrow
+        keys, and all custom key bindings, but we don't really render the
+        cursor movements. Instead we only print the typed character that's
+        right before the cursor.
+        """
+        # Send prompt to output.
+        self.output.write(fragment_list_to_text(to_formatted_text(self.message)))
+        self.output.flush()
+
+        # Key bindings for the dumb prompt: mostly the same as the full prompt.
+        key_bindings: KeyBindingsBase = self._create_prompt_bindings()
+        if self.key_bindings:
+            key_bindings = merge_key_bindings([self.key_bindings, key_bindings])
+
+        # Create and run application.
+        application = cast(
+            Application[_T],
+            Application(
+                input=self.input,
+                output=DummyOutput(),
+                layout=self.layout,
+                key_bindings=key_bindings,
+            ),
+        )
+
+        def on_text_changed(_: object) -> None:
+            self.output.write(self.default_buffer.document.text_before_cursor[-1:])
+            self.output.flush()
+
+        self.default_buffer.on_text_changed += on_text_changed
+
+        try:
+            yield application
+        finally:
+            # Render line ending.
+            self.output.write("\r\n")
+            self.output.flush()
+
+            self.default_buffer.on_text_changed -= on_text_changed
+
+    async def prompt_async(
+        self,
+        # When any of these arguments are passed, this value is overwritten
+        # in this PromptSession.
+        message: Optional[AnyFormattedText] = None,
+        # `message` should go first, because people call it as
+        # positional argument.
+        *,
+        editing_mode: Optional[EditingMode] = None,
+        refresh_interval: Optional[float] = None,
+        vi_mode: Optional[bool] = None,
+        lexer: Optional[Lexer] = None,
+        completer: Optional[Completer] = None,
+        complete_in_thread: Optional[bool] = None,
+        is_password: Optional[bool] = None,
+        key_bindings: Optional[KeyBindingsBase] = None,
+        bottom_toolbar: Optional[AnyFormattedText] = None,
+        style: Optional[BaseStyle] = None,
+        color_depth: Optional[ColorDepth] = None,
+        cursor: Optional[CursorShapeConfig] = None,
+        include_default_pygments_style: Optional[FilterOrBool] = None,
+        style_transformation: Optional[StyleTransformation] = None,
+        swap_light_and_dark_colors: Optional[FilterOrBool] = None,
+        rprompt: Optional[AnyFormattedText] = None,
+        multiline: Optional[FilterOrBool] = None,
+        prompt_continuation: Optional[PromptContinuationText] = None,
+        wrap_lines: Optional[FilterOrBool] = None,
+        enable_history_search: Optional[FilterOrBool] = None,
+        search_ignore_case: Optional[FilterOrBool] = None,
+        complete_while_typing: Optional[FilterOrBool] = None,
+        validate_while_typing: Optional[FilterOrBool] = None,
+        complete_style: Optional[CompleteStyle] = None,
+        auto_suggest: Optional[AutoSuggest] = None,
+        validator: Optional[Validator] = None,
+        clipboard: Optional[Clipboard] = None,
+        mouse_support: Optional[FilterOrBool] = None,
+        input_processors: Optional[List[Processor]] = None,
+        placeholder: Optional[AnyFormattedText] = None,
+        reserve_space_for_menu: Optional[int] = None,
+        enable_system_prompt: Optional[FilterOrBool] = None,
+        enable_suspend: Optional[FilterOrBool] = None,
+        enable_open_in_editor: Optional[FilterOrBool] = None,
+        tempfile_suffix: Optional[Union[str, Callable[[], str]]] = None,
+        tempfile: Optional[Union[str, Callable[[], str]]] = None,
+        # Following arguments are specific to the current `prompt()` call.
+        default: Union[str, Document] = "",
+        accept_default: bool = False,
+        pre_run: Optional[Callable[[], None]] = None,
+        set_exception_handler: bool = True,
+        handle_sigint: bool = True,
+    ) -> _T:
+
+        if message is not None:
+            self.message = message
+        if editing_mode is not None:
+            self.editing_mode = editing_mode
+        if refresh_interval is not None:
+            self.refresh_interval = refresh_interval
+        if vi_mode:
+            self.editing_mode = EditingMode.VI
+        if lexer is not None:
+            self.lexer = lexer
+        if completer is not None:
+            self.completer = completer
+        if complete_in_thread is not None:
+            self.complete_in_thread = complete_in_thread
+        if is_password is not None:
+            self.is_password = is_password
+        if key_bindings is not None:
+            self.key_bindings = key_bindings
+        if bottom_toolbar is not None:
+            self.bottom_toolbar = bottom_toolbar
+        if style is not None:
+            self.style = style
+        if color_depth is not None:
+            self.color_depth = color_depth
+        if cursor is not None:
+            self.cursor = cursor
+        if include_default_pygments_style is not None:
+            self.include_default_pygments_style = include_default_pygments_style
+        if style_transformation is not None:
+            self.style_transformation = style_transformation
+        if swap_light_and_dark_colors is not None:
+            self.swap_light_and_dark_colors = swap_light_and_dark_colors
+        if rprompt is not None:
+            self.rprompt = rprompt
+        if multiline is not None:
+            self.multiline = multiline
+        if prompt_continuation is not None:
+            self.prompt_continuation = prompt_continuation
+        if wrap_lines is not None:
+            self.wrap_lines = wrap_lines
+        if enable_history_search is not None:
+            self.enable_history_search = enable_history_search
+        if search_ignore_case is not None:
+            self.search_ignore_case = search_ignore_case
+        if complete_while_typing is not None:
+            self.complete_while_typing = complete_while_typing
+        if validate_while_typing is not None:
+            self.validate_while_typing = validate_while_typing
+        if complete_style is not None:
+            self.complete_style = complete_style
+        if auto_suggest is not None:
+            self.auto_suggest = auto_suggest
+        if validator is not None:
+            self.validator = validator
+        if clipboard is not None:
+            self.clipboard = clipboard
+        if mouse_support is not None:
+            self.mouse_support = mouse_support
+        if input_processors is not None:
+            self.input_processors = input_processors
+        if placeholder is not None:
+            self.placeholder = placeholder
+        if reserve_space_for_menu is not None:
+            self.reserve_space_for_menu = reserve_space_for_menu
+        if enable_system_prompt is not None:
+            self.enable_system_prompt = enable_system_prompt
+        if enable_suspend is not None:
+            self.enable_suspend = enable_suspend
+        if enable_open_in_editor is not None:
+            self.enable_open_in_editor = enable_open_in_editor
+        if tempfile_suffix is not None:
+            self.tempfile_suffix = tempfile_suffix
+        if tempfile is not None:
+            self.tempfile = tempfile
+
+        self._add_pre_run_callables(pre_run, accept_default)
+        self.default_buffer.reset(
+            default if isinstance(default, Document) else Document(default)
+        )
+        self.app.refresh_interval = self.refresh_interval  # This is not reactive.
+
+        # If we are using the default output, and have a dumb terminal. Use the
+        # dumb prompt.
+        if self._output is None and is_dumb_terminal():
+            with self._dumb_prompt(self.message) as dump_app:
+                return await dump_app.run_async(handle_sigint=handle_sigint)
+
+        return await self.app.run_async(
+            set_exception_handler=set_exception_handler, handle_sigint=handle_sigint
+        )
+
+    def _add_pre_run_callables(
+        self, pre_run: Optional[Callable[[], None]], accept_default: bool
+    ) -> None:
+        def pre_run2() -> None:
+            if pre_run:
+                pre_run()
+
+            if accept_default:
+                # Validate and handle input. We use `call_from_executor` in
+                # order to run it "soon" (during the next iteration of the
+                # event loop), instead of right now. Otherwise, it won't
+                # display the default value.
+                get_event_loop().call_soon(self.default_buffer.validate_and_handle)
+
+        self.app.pre_run_callables.append(pre_run2)
+
+    @property
+    def editing_mode(self) -> EditingMode:
+        return self.app.editing_mode
+
+    @editing_mode.setter
+    def editing_mode(self, value: EditingMode) -> None:
+        self.app.editing_mode = value
+
+    def _get_default_buffer_control_height(self) -> Dimension:
+        # If there is an autocompletion menu to be shown, make sure that our
+        # layout has at least a minimal height in order to display it.
+        if (
+            self.completer is not None
+            and self.complete_style != CompleteStyle.READLINE_LIKE
+        ):
+            space = self.reserve_space_for_menu
+        else:
+            space = 0
+
+        if space and not get_app().is_done:
+            buff = self.default_buffer
+
+            # Reserve the space, either when there are completions, or when
+            # `complete_while_typing` is true and we expect completions very
+            # soon.
+            if buff.complete_while_typing() or buff.complete_state is not None:
+                return Dimension(min=space)
+
+        return Dimension()
+
+    def _get_prompt(self) -> StyleAndTextTuples:
+        return to_formatted_text(self.message, style="class:prompt")
+
+    def _get_continuation(
+        self, width: int, line_number: int, wrap_count: int
+    ) -> StyleAndTextTuples:
+        """
+        Insert the prompt continuation.
+
+        :param width: The width that was used for the prompt. (more or less can
+            be used.)
+        :param line_number:
+        :param wrap_count: Amount of times that the line has been wrapped.
+        """
+        prompt_continuation = self.prompt_continuation
+
+        if callable(prompt_continuation):
+            continuation: AnyFormattedText = prompt_continuation(
+                width, line_number, wrap_count
+            )
+        else:
+            continuation = prompt_continuation
+
+        # When the continuation prompt is not given, choose the same width as
+        # the actual prompt.
+        if continuation is None and is_true(self.multiline):
+            continuation = " " * width
+
+        return to_formatted_text(continuation, style="class:prompt-continuation")
+
+    def _get_line_prefix(
+        self,
+        line_number: int,
+        wrap_count: int,
+        get_prompt_text_2: _StyleAndTextTuplesCallable,
+    ) -> StyleAndTextTuples:
+        """
+        Return whatever needs to be inserted before every line.
+        (the prompt, or a line continuation.)
+        """
+        # First line: display the "arg" or the prompt.
+        if line_number == 0 and wrap_count == 0:
+            if not is_true(self.multiline) and get_app().key_processor.arg is not None:
+                return self._inline_arg()
+            else:
+                return get_prompt_text_2()
+
+        # For the next lines, display the appropriate continuation.
+        prompt_width = get_cwidth(fragment_list_to_text(get_prompt_text_2()))
+        return self._get_continuation(prompt_width, line_number, wrap_count)
+
+    def _get_arg_text(self) -> StyleAndTextTuples:
+        "'arg' toolbar, for in multiline mode."
+        arg = self.app.key_processor.arg
+        if arg is None:
+            # Should not happen because of the `has_arg` filter in the layout.
+            return []
+
+        if arg == "-":
+            arg = "-1"
+
+        return [("class:arg-toolbar", "Repeat: "), ("class:arg-toolbar.text", arg)]
+
+    def _inline_arg(self) -> StyleAndTextTuples:
+        "'arg' prefix, for in single line mode."
+        app = get_app()
+        if app.key_processor.arg is None:
+            return []
+        else:
+            arg = app.key_processor.arg
+
+            return [
+                ("class:prompt.arg", "(arg: "),
+                ("class:prompt.arg.text", str(arg)),
+                ("class:prompt.arg", ") "),
+            ]
+
+    # Expose the Input and Output objects as attributes, mainly for
+    # backward-compatibility.
+
+    @property
+    def input(self) -> Input:
+        return self.app.input
+
+    @property
+    def output(self) -> Output:
+        return self.app.output
+
+
+def prompt(
+    message: Optional[AnyFormattedText] = None,
+    *,
+    history: Optional[History] = None,
+    editing_mode: Optional[EditingMode] = None,
+    refresh_interval: Optional[float] = None,
+    vi_mode: Optional[bool] = None,
+    lexer: Optional[Lexer] = None,
+    completer: Optional[Completer] = None,
+    complete_in_thread: Optional[bool] = None,
+    is_password: Optional[bool] = None,
+    key_bindings: Optional[KeyBindingsBase] = None,
+    bottom_toolbar: Optional[AnyFormattedText] = None,
+    style: Optional[BaseStyle] = None,
+    color_depth: Optional[ColorDepth] = None,
+    cursor: AnyCursorShapeConfig = None,
+    include_default_pygments_style: Optional[FilterOrBool] = None,
+    style_transformation: Optional[StyleTransformation] = None,
+    swap_light_and_dark_colors: Optional[FilterOrBool] = None,
+    rprompt: Optional[AnyFormattedText] = None,
+    multiline: Optional[FilterOrBool] = None,
+    prompt_continuation: Optional[PromptContinuationText] = None,
+    wrap_lines: Optional[FilterOrBool] = None,
+    enable_history_search: Optional[FilterOrBool] = None,
+    search_ignore_case: Optional[FilterOrBool] = None,
+    complete_while_typing: Optional[FilterOrBool] = None,
+    validate_while_typing: Optional[FilterOrBool] = None,
+    complete_style: Optional[CompleteStyle] = None,
+    auto_suggest: Optional[AutoSuggest] = None,
+    validator: Optional[Validator] = None,
+    clipboard: Optional[Clipboard] = None,
+    mouse_support: Optional[FilterOrBool] = None,
+    input_processors: Optional[List[Processor]] = None,
+    placeholder: Optional[AnyFormattedText] = None,
+    reserve_space_for_menu: Optional[int] = None,
+    enable_system_prompt: Optional[FilterOrBool] = None,
+    enable_suspend: Optional[FilterOrBool] = None,
+    enable_open_in_editor: Optional[FilterOrBool] = None,
+    tempfile_suffix: Optional[Union[str, Callable[[], str]]] = None,
+    tempfile: Optional[Union[str, Callable[[], str]]] = None,
+    # Following arguments are specific to the current `prompt()` call.
+    default: str = "",
+    accept_default: bool = False,
+    pre_run: Optional[Callable[[], None]] = None,
+) -> str:
+    """
+    The global `prompt` function. This will create a new `PromptSession`
+    instance for every call.
+    """
+    # The history is the only attribute that has to be passed to the
+    # `PromptSession`, it can't be passed into the `prompt()` method.
+    session: PromptSession[str] = PromptSession(history=history)
+
+    return session.prompt(
+        message,
+        editing_mode=editing_mode,
+        refresh_interval=refresh_interval,
+        vi_mode=vi_mode,
+        lexer=lexer,
+        completer=completer,
+        complete_in_thread=complete_in_thread,
+        is_password=is_password,
+        key_bindings=key_bindings,
+        bottom_toolbar=bottom_toolbar,
+        style=style,
+        color_depth=color_depth,
+        cursor=cursor,
+        include_default_pygments_style=include_default_pygments_style,
+        style_transformation=style_transformation,
+        swap_light_and_dark_colors=swap_light_and_dark_colors,
+        rprompt=rprompt,
+        multiline=multiline,
+        prompt_continuation=prompt_continuation,
+        wrap_lines=wrap_lines,
+        enable_history_search=enable_history_search,
+        search_ignore_case=search_ignore_case,
+        complete_while_typing=complete_while_typing,
+        validate_while_typing=validate_while_typing,
+        complete_style=complete_style,
+        auto_suggest=auto_suggest,
+        validator=validator,
+        clipboard=clipboard,
+        mouse_support=mouse_support,
+        input_processors=input_processors,
+        placeholder=placeholder,
+        reserve_space_for_menu=reserve_space_for_menu,
+        enable_system_prompt=enable_system_prompt,
+        enable_suspend=enable_suspend,
+        enable_open_in_editor=enable_open_in_editor,
+        tempfile_suffix=tempfile_suffix,
+        tempfile=tempfile,
+        default=default,
+        accept_default=accept_default,
+        pre_run=pre_run,
+    )
+
+
+prompt.__doc__ = PromptSession.prompt.__doc__
+
+
+def create_confirm_session(
+    message: str, suffix: str = " (y/n) "
+) -> PromptSession[bool]:
+    """
+    Create a `PromptSession` object for the 'confirm' function.
+    """
+    bindings = KeyBindings()
+
+    @bindings.add("y")
+    @bindings.add("Y")
+    def yes(event: E) -> None:
+        session.default_buffer.text = "y"
+        event.app.exit(result=True)
+
+    @bindings.add("n")
+    @bindings.add("N")
+    def no(event: E) -> None:
+        session.default_buffer.text = "n"
+        event.app.exit(result=False)
+
+    @bindings.add(Keys.Any)
+    def _(event: E) -> None:
+        "Disallow inserting other text."
+        pass
+
+    complete_message = merge_formatted_text([message, suffix])
+    session: PromptSession[bool] = PromptSession(
+        complete_message, key_bindings=bindings
+    )
+    return session
+
+
+def confirm(message: str = "Confirm?", suffix: str = " (y/n) ") -> bool:
+    """
+    Display a confirmation prompt that returns True/False.
+    """
+    session = create_confirm_session(message, suffix)
+    return session.prompt()
diff --git a/src/prompt_toolkit/shortcuts/utils.py b/src/prompt_toolkit/shortcuts/utils.py
new file mode 100644
index 0000000..a628f4b
--- /dev/null
+++ b/src/prompt_toolkit/shortcuts/utils.py
@@ -0,0 +1,238 @@
+from asyncio.events import AbstractEventLoop
+from typing import TYPE_CHECKING, Any, Optional, TextIO
+
+from prompt_toolkit.application import Application
+from prompt_toolkit.application.current import get_app_or_none, get_app_session
+from prompt_toolkit.application.run_in_terminal import run_in_terminal
+from prompt_toolkit.eventloop import get_event_loop
+from prompt_toolkit.formatted_text import (
+    FormattedText,
+    StyleAndTextTuples,
+    to_formatted_text,
+)
+from prompt_toolkit.input import DummyInput
+from prompt_toolkit.layout import Layout
+from prompt_toolkit.output import ColorDepth, Output
+from prompt_toolkit.output.defaults import create_output
+from prompt_toolkit.renderer import (
+    print_formatted_text as renderer_print_formatted_text,
+)
+from prompt_toolkit.styles import (
+    BaseStyle,
+    StyleTransformation,
+    default_pygments_style,
+    default_ui_style,
+    merge_styles,
+)
+
+if TYPE_CHECKING:
+    from prompt_toolkit.layout.containers import AnyContainer
+
+__all__ = [
+    "print_formatted_text",
+    "print_container",
+    "clear",
+    "set_title",
+    "clear_title",
+]
+
+
+def print_formatted_text(
+    *values: Any,
+    sep: str = " ",
+    end: str = "\n",
+    file: Optional[TextIO] = None,
+    flush: bool = False,
+    style: Optional[BaseStyle] = None,
+    output: Optional[Output] = None,
+    color_depth: Optional[ColorDepth] = None,
+    style_transformation: Optional[StyleTransformation] = None,
+    include_default_pygments_style: bool = True,
+) -> None:
+    """
+    ::
+
+        print_formatted_text(*values, sep=' ', end='\\n', file=None, flush=False, style=None, output=None)
+
+    Print text to stdout. This is supposed to be compatible with Python's print
+    function, but supports printing of formatted text. You can pass a
+    :class:`~prompt_toolkit.formatted_text.FormattedText`,
+    :class:`~prompt_toolkit.formatted_text.HTML` or
+    :class:`~prompt_toolkit.formatted_text.ANSI` object to print formatted
+    text.
+
+    * Print HTML as follows::
+
+        print_formatted_text(HTML('<i>Some italic text</i> <ansired>This is red!</ansired>'))
+
+        style = Style.from_dict({
+            'hello': '#ff0066',
+            'world': '#884444 italic',
+        })
+        print_formatted_text(HTML('<hello>Hello</hello> <world>world</world>!'), style=style)
+
+    * Print a list of (style_str, text) tuples in the given style to the
+      output.  E.g.::
+
+        style = Style.from_dict({
+            'hello': '#ff0066',
+            'world': '#884444 italic',
+        })
+        fragments = FormattedText([
+            ('class:hello', 'Hello'),
+            ('class:world', 'World'),
+        ])
+        print_formatted_text(fragments, style=style)
+
+    If you want to print a list of Pygments tokens, wrap it in
+    :class:`~prompt_toolkit.formatted_text.PygmentsTokens` to do the
+    conversion.
+
+    If a prompt_toolkit `Application` is currently running, this will always
+    print above the application or prompt (similar to `patch_stdout`). So,
+    `print_formatted_text` will erase the current application, print the text,
+    and render the application again.
+
+    :param values: Any kind of printable object, or formatted string.
+    :param sep: String inserted between values, default a space.
+    :param end: String appended after the last value, default a newline.
+    :param style: :class:`.Style` instance for the color scheme.
+    :param include_default_pygments_style: `bool`. Include the default Pygments
+        style when set to `True` (the default).
+    """
+    assert not (output and file)
+
+    # Create Output object.
+    if output is None:
+        if file:
+            output = create_output(stdout=file)
+        else:
+            output = get_app_session().output
+
+    assert isinstance(output, Output)
+
+    # Get color depth.
+    color_depth = color_depth or output.get_default_color_depth()
+
+    # Merges values.
+    def to_text(val: Any) -> StyleAndTextTuples:
+        # Normal lists which are not instances of `FormattedText` are
+        # considered plain text.
+        if isinstance(val, list) and not isinstance(val, FormattedText):
+            return to_formatted_text(f"{val}")
+        return to_formatted_text(val, auto_convert=True)
+
+    fragments = []
+    for i, value in enumerate(values):
+        fragments.extend(to_text(value))
+
+        if sep and i != len(values) - 1:
+            fragments.extend(to_text(sep))
+
+    fragments.extend(to_text(end))
+
+    # Print output.
+    def render() -> None:
+        assert isinstance(output, Output)
+
+        renderer_print_formatted_text(
+            output,
+            fragments,
+            _create_merged_style(
+                style, include_default_pygments_style=include_default_pygments_style
+            ),
+            color_depth=color_depth,
+            style_transformation=style_transformation,
+        )
+
+        # Flush the output stream.
+        if flush:
+            output.flush()
+
+    # If an application is running, print above the app. This does not require
+    # `patch_stdout`.
+    loop: Optional[AbstractEventLoop] = None
+
+    app = get_app_or_none()
+    if app is not None:
+        loop = app.loop
+
+    if loop is not None:
+        loop.call_soon_threadsafe(lambda: run_in_terminal(render))
+    else:
+        render()
+
+
+def print_container(
+    container: "AnyContainer",
+    file: Optional[TextIO] = None,
+    style: Optional[BaseStyle] = None,
+    include_default_pygments_style: bool = True,
+) -> None:
+    """
+    Print any layout to the output in a non-interactive way.
+
+    Example usage::
+
+        from prompt_toolkit.widgets import Frame, TextArea
+        print_container(
+            Frame(TextArea(text='Hello world!')))
+    """
+    if file:
+        output = create_output(stdout=file)
+    else:
+        output = get_app_session().output
+
+    app: Application[None] = Application(
+        layout=Layout(container=container),
+        output=output,
+        # `DummyInput` will cause the application to terminate immediately.
+        input=DummyInput(),
+        style=_create_merged_style(
+            style, include_default_pygments_style=include_default_pygments_style
+        ),
+    )
+    try:
+        app.run(in_thread=True)
+    except EOFError:
+        pass
+
+
+def _create_merged_style(
+    style: Optional[BaseStyle], include_default_pygments_style: bool
+) -> BaseStyle:
+    """
+    Merge user defined style with built-in style.
+    """
+    styles = [default_ui_style()]
+    if include_default_pygments_style:
+        styles.append(default_pygments_style())
+    if style:
+        styles.append(style)
+
+    return merge_styles(styles)
+
+
+def clear() -> None:
+    """
+    Clear the screen.
+    """
+    output = get_app_session().output
+    output.erase_screen()
+    output.cursor_goto(0, 0)
+    output.flush()
+
+
+def set_title(text: str) -> None:
+    """
+    Set the terminal title.
+    """
+    output = get_app_session().output
+    output.set_title(text)
+
+
+def clear_title() -> None:
+    """
+    Erase the current title.
+    """
+    set_title("")
diff --git a/src/prompt_toolkit/styles/__init__.py b/src/prompt_toolkit/styles/__init__.py
new file mode 100644
index 0000000..c270ae0
--- /dev/null
+++ b/src/prompt_toolkit/styles/__init__.py
@@ -0,0 +1,64 @@
+"""
+Styling for prompt_toolkit applications.
+"""
+from .base import (
+    ANSI_COLOR_NAMES,
+    DEFAULT_ATTRS,
+    Attrs,
+    BaseStyle,
+    DummyStyle,
+    DynamicStyle,
+)
+from .defaults import default_pygments_style, default_ui_style
+from .named_colors import NAMED_COLORS
+from .pygments import (
+    pygments_token_to_classname,
+    style_from_pygments_cls,
+    style_from_pygments_dict,
+)
+from .style import Priority, Style, merge_styles, parse_color
+from .style_transformation import (
+    AdjustBrightnessStyleTransformation,
+    ConditionalStyleTransformation,
+    DummyStyleTransformation,
+    DynamicStyleTransformation,
+    ReverseStyleTransformation,
+    SetDefaultColorStyleTransformation,
+    StyleTransformation,
+    SwapLightAndDarkStyleTransformation,
+    merge_style_transformations,
+)
+
+__all__ = [
+    # Base.
+    "Attrs",
+    "DEFAULT_ATTRS",
+    "ANSI_COLOR_NAMES",
+    "BaseStyle",
+    "DummyStyle",
+    "DynamicStyle",
+    # Defaults.
+    "default_ui_style",
+    "default_pygments_style",
+    # Style.
+    "Style",
+    "Priority",
+    "merge_styles",
+    "parse_color",
+    # Style transformation.
+    "StyleTransformation",
+    "SwapLightAndDarkStyleTransformation",
+    "ReverseStyleTransformation",
+    "SetDefaultColorStyleTransformation",
+    "AdjustBrightnessStyleTransformation",
+    "DummyStyleTransformation",
+    "ConditionalStyleTransformation",
+    "DynamicStyleTransformation",
+    "merge_style_transformations",
+    # Pygments.
+    "style_from_pygments_cls",
+    "style_from_pygments_dict",
+    "pygments_token_to_classname",
+    # Named colors.
+    "NAMED_COLORS",
+]
diff --git a/src/prompt_toolkit/styles/base.py b/src/prompt_toolkit/styles/base.py
new file mode 100644
index 0000000..aa77b9a
--- /dev/null
+++ b/src/prompt_toolkit/styles/base.py
@@ -0,0 +1,181 @@
+"""
+The base classes for the styling.
+"""
+from abc import ABCMeta, abstractmethod, abstractproperty
+from typing import Callable, Dict, Hashable, List, NamedTuple, Optional, Tuple
+
+__all__ = [
+    "Attrs",
+    "DEFAULT_ATTRS",
+    "ANSI_COLOR_NAMES",
+    "ANSI_COLOR_NAMES_ALIASES",
+    "BaseStyle",
+    "DummyStyle",
+    "DynamicStyle",
+]
+
+
+#: Style attributes.
+class Attrs(NamedTuple):
+    color: Optional[str]
+    bgcolor: Optional[str]
+    bold: Optional[bool]
+    underline: Optional[bool]
+    strike: Optional[bool]
+    italic: Optional[bool]
+    blink: Optional[bool]
+    reverse: Optional[bool]
+    hidden: Optional[bool]
+
+
+"""
+:param color: Hexadecimal string. E.g. '000000' or Ansi color name: e.g. 'ansiblue'
+:param bgcolor: Hexadecimal string. E.g. 'ffffff' or Ansi color name: e.g. 'ansired'
+:param bold: Boolean
+:param underline: Boolean
+:param strike: Boolean
+:param italic: Boolean
+:param blink: Boolean
+:param reverse: Boolean
+:param hidden: Boolean
+"""
+
+#: The default `Attrs`.
+DEFAULT_ATTRS = Attrs(
+    color="",
+    bgcolor="",
+    bold=False,
+    underline=False,
+    strike=False,
+    italic=False,
+    blink=False,
+    reverse=False,
+    hidden=False,
+)
+
+
+#: ``Attrs.bgcolor/fgcolor`` can be in either 'ffffff' format, or can be any of
+#: the following in case we want to take colors from the 8/16 color palette.
+#: Usually, in that case, the terminal application allows to configure the RGB
+#: values for these names.
+#: ISO 6429 colors
+ANSI_COLOR_NAMES = [
+    "ansidefault",
+    # Low intensity, dark.  (One or two components 0x80, the other 0x00.)
+    "ansiblack",
+    "ansired",
+    "ansigreen",
+    "ansiyellow",
+    "ansiblue",
+    "ansimagenta",
+    "ansicyan",
+    "ansigray",
+    # High intensity, bright. (One or two components 0xff, the other 0x00. Not supported everywhere.)
+    "ansibrightblack",
+    "ansibrightred",
+    "ansibrightgreen",
+    "ansibrightyellow",
+    "ansibrightblue",
+    "ansibrightmagenta",
+    "ansibrightcyan",
+    "ansiwhite",
+]
+
+
+# People don't use the same ANSI color names everywhere. In prompt_toolkit 1.0
+# we used some unconventional names (which were contributed like that to
+# Pygments). This is fixed now, but we still support the old names.
+
+# The table below maps the old aliases to the current names.
+ANSI_COLOR_NAMES_ALIASES: Dict[str, str] = {
+    "ansidarkgray": "ansibrightblack",
+    "ansiteal": "ansicyan",
+    "ansiturquoise": "ansibrightcyan",
+    "ansibrown": "ansiyellow",
+    "ansipurple": "ansimagenta",
+    "ansifuchsia": "ansibrightmagenta",
+    "ansilightgray": "ansigray",
+    "ansidarkred": "ansired",
+    "ansidarkgreen": "ansigreen",
+    "ansidarkblue": "ansiblue",
+}
+assert set(ANSI_COLOR_NAMES_ALIASES.values()).issubset(set(ANSI_COLOR_NAMES))
+assert not (set(ANSI_COLOR_NAMES_ALIASES.keys()) & set(ANSI_COLOR_NAMES))
+
+
+class BaseStyle(metaclass=ABCMeta):
+    """
+    Abstract base class for prompt_toolkit styles.
+    """
+
+    @abstractmethod
+    def get_attrs_for_style_str(
+        self, style_str: str, default: Attrs = DEFAULT_ATTRS
+    ) -> Attrs:
+        """
+        Return :class:`.Attrs` for the given style string.
+
+        :param style_str: The style string. This can contain inline styling as
+            well as classnames (e.g. "class:title").
+        :param default: `Attrs` to be used if no styling was defined.
+        """
+
+    @abstractproperty
+    def style_rules(self) -> List[Tuple[str, str]]:
+        """
+        The list of style rules, used to create this style.
+        (Required for `DynamicStyle` and `_MergedStyle` to work.)
+        """
+        return []
+
+    @abstractmethod
+    def invalidation_hash(self) -> Hashable:
+        """
+        Invalidation hash for the style. When this changes over time, the
+        renderer knows that something in the style changed, and that everything
+        has to be redrawn.
+        """
+
+
+class DummyStyle(BaseStyle):
+    """
+    A style that doesn't style anything.
+    """
+
+    def get_attrs_for_style_str(
+        self, style_str: str, default: Attrs = DEFAULT_ATTRS
+    ) -> Attrs:
+        return default
+
+    def invalidation_hash(self) -> Hashable:
+        return 1  # Always the same value.
+
+    @property
+    def style_rules(self) -> List[Tuple[str, str]]:
+        return []
+
+
+class DynamicStyle(BaseStyle):
+    """
+    Style class that can dynamically returns an other Style.
+
+    :param get_style: Callable that returns a :class:`.Style` instance.
+    """
+
+    def __init__(self, get_style: Callable[[], Optional[BaseStyle]]):
+        self.get_style = get_style
+        self._dummy = DummyStyle()
+
+    def get_attrs_for_style_str(
+        self, style_str: str, default: Attrs = DEFAULT_ATTRS
+    ) -> Attrs:
+        style = self.get_style() or self._dummy
+
+        return style.get_attrs_for_style_str(style_str, default)
+
+    def invalidation_hash(self) -> Hashable:
+        return (self.get_style() or self._dummy).invalidation_hash()
+
+    @property
+    def style_rules(self) -> List[Tuple[str, str]]:
+        return (self.get_style() or self._dummy).style_rules
diff --git a/src/prompt_toolkit/styles/defaults.py b/src/prompt_toolkit/styles/defaults.py
new file mode 100644
index 0000000..4ac5545
--- /dev/null
+++ b/src/prompt_toolkit/styles/defaults.py
@@ -0,0 +1,231 @@
+"""
+The default styling.
+"""
+from prompt_toolkit.cache import memoized
+
+from .base import ANSI_COLOR_NAMES, BaseStyle
+from .named_colors import NAMED_COLORS
+from .style import Style, merge_styles
+
+__all__ = [
+    "default_ui_style",
+    "default_pygments_style",
+]
+
+#: Default styling. Mapping from classnames to their style definition.
+PROMPT_TOOLKIT_STYLE = [
+    # Highlighting of search matches in document.
+    ("search", "bg:ansibrightyellow ansiblack"),
+    ("search.current", ""),
+    # Incremental search.
+    ("incsearch", ""),
+    ("incsearch.current", "reverse"),
+    # Highlighting of select text in document.
+    ("selected", "reverse"),
+    ("cursor-column", "bg:#dddddd"),
+    ("cursor-line", "underline"),
+    ("color-column", "bg:#ccaacc"),
+    # Highlighting of matching brackets.
+    ("matching-bracket", ""),
+    ("matching-bracket.other", "#000000 bg:#aacccc"),
+    ("matching-bracket.cursor", "#ff8888 bg:#880000"),
+    # Styling of other cursors, in case of block editing.
+    ("multiple-cursors", "#000000 bg:#ccccaa"),
+    # Line numbers.
+    ("line-number", "#888888"),
+    ("line-number.current", "bold"),
+    ("tilde", "#8888ff"),
+    # Default prompt.
+    ("prompt", ""),
+    ("prompt.arg", "noinherit"),
+    ("prompt.arg.text", ""),
+    ("prompt.search", "noinherit"),
+    ("prompt.search.text", ""),
+    # Search toolbar.
+    ("search-toolbar", "bold"),
+    ("search-toolbar.text", "nobold"),
+    # System toolbar
+    ("system-toolbar", "bold"),
+    ("system-toolbar.text", "nobold"),
+    # "arg" toolbar.
+    ("arg-toolbar", "bold"),
+    ("arg-toolbar.text", "nobold"),
+    # Validation toolbar.
+    ("validation-toolbar", "bg:#550000 #ffffff"),
+    ("window-too-small", "bg:#550000 #ffffff"),
+    # Completions toolbar.
+    ("completion-toolbar", "bg:#bbbbbb #000000"),
+    ("completion-toolbar.arrow", "bg:#bbbbbb #000000 bold"),
+    ("completion-toolbar.completion", "bg:#bbbbbb #000000"),
+    ("completion-toolbar.completion.current", "bg:#444444 #ffffff"),
+    # Completions menu.
+    ("completion-menu", "bg:#bbbbbb #000000"),
+    ("completion-menu.completion", ""),
+    ("completion-menu.completion.current", "bg:#888888 #ffffff"),
+    ("completion-menu.meta.completion", "bg:#999999 #000000"),
+    ("completion-menu.meta.completion.current", "bg:#aaaaaa #000000"),
+    ("completion-menu.multi-column-meta", "bg:#aaaaaa #000000"),
+    # Fuzzy matches in completion menu (for FuzzyCompleter).
+    ("completion-menu.completion fuzzymatch.outside", "fg:#444444"),
+    ("completion-menu.completion fuzzymatch.inside", "bold"),
+    ("completion-menu.completion fuzzymatch.inside.character", "underline"),
+    ("completion-menu.completion.current fuzzymatch.outside", "fg:default"),
+    ("completion-menu.completion.current fuzzymatch.inside", "nobold"),
+    # Styling of readline-like completions.
+    ("readline-like-completions", ""),
+    ("readline-like-completions.completion", ""),
+    ("readline-like-completions.completion fuzzymatch.outside", "#888888"),
+    ("readline-like-completions.completion fuzzymatch.inside", ""),
+    ("readline-like-completions.completion fuzzymatch.inside.character", "underline"),
+    # Scrollbars.
+    ("scrollbar.background", "bg:#aaaaaa"),
+    ("scrollbar.button", "bg:#444444"),
+    ("scrollbar.arrow", "noinherit bold"),
+    # Start/end of scrollbars. Adding 'underline' here provides a nice little
+    # detail to the progress bar, but it doesn't look good on all terminals.
+    # ('scrollbar.start',                          'underline #ffffff'),
+    # ('scrollbar.end',                            'underline #000000'),
+    # Auto suggestion text.
+    ("auto-suggestion", "#666666"),
+    # Trailing whitespace and tabs.
+    ("trailing-whitespace", "#999999"),
+    ("tab", "#999999"),
+    # When Control-C/D has been pressed. Grayed.
+    ("aborting", "#888888 bg:default noreverse noitalic nounderline noblink"),
+    ("exiting", "#888888 bg:default noreverse noitalic nounderline noblink"),
+    # Entering a Vi digraph.
+    ("digraph", "#4444ff"),
+    # Control characters, like ^C, ^X.
+    ("control-character", "ansiblue"),
+    # Non-breaking space.
+    ("nbsp", "underline ansiyellow"),
+    # Default styling of HTML elements.
+    ("i", "italic"),
+    ("u", "underline"),
+    ("s", "strike"),
+    ("b", "bold"),
+    ("em", "italic"),
+    ("strong", "bold"),
+    ("del", "strike"),
+    ("hidden", "hidden"),
+    # It should be possible to use the style names in HTML.
+    # <reverse>...</reverse>  or <noreverse>...</noreverse>.
+    ("italic", "italic"),
+    ("underline", "underline"),
+    ("strike", "strike"),
+    ("bold", "bold"),
+    ("reverse", "reverse"),
+    ("noitalic", "noitalic"),
+    ("nounderline", "nounderline"),
+    ("nostrike", "nostrike"),
+    ("nobold", "nobold"),
+    ("noreverse", "noreverse"),
+    # Prompt bottom toolbar
+    ("bottom-toolbar", "reverse"),
+]
+
+
+# Style that will turn for instance the class 'red' into 'red'.
+COLORS_STYLE = [(name, "fg:" + name) for name in ANSI_COLOR_NAMES] + [
+    (name.lower(), "fg:" + name) for name in NAMED_COLORS
+]
+
+
+WIDGETS_STYLE = [
+    # Dialog windows.
+    ("dialog", "bg:#4444ff"),
+    ("dialog.body", "bg:#ffffff #000000"),
+    ("dialog.body text-area", "bg:#cccccc"),
+    ("dialog.body text-area last-line", "underline"),
+    ("dialog frame.label", "#ff0000 bold"),
+    # Scrollbars in dialogs.
+    ("dialog.body scrollbar.background", ""),
+    ("dialog.body scrollbar.button", "bg:#000000"),
+    ("dialog.body scrollbar.arrow", ""),
+    ("dialog.body scrollbar.start", "nounderline"),
+    ("dialog.body scrollbar.end", "nounderline"),
+    # Buttons.
+    ("button", ""),
+    ("button.arrow", "bold"),
+    ("button.focused", "bg:#aa0000 #ffffff"),
+    # Menu bars.
+    ("menu-bar", "bg:#aaaaaa #000000"),
+    ("menu-bar.selected-item", "bg:#ffffff #000000"),
+    ("menu", "bg:#888888 #ffffff"),
+    ("menu.border", "#aaaaaa"),
+    ("menu.border shadow", "#444444"),
+    # Shadows.
+    ("dialog shadow", "bg:#000088"),
+    ("dialog.body shadow", "bg:#aaaaaa"),
+    ("progress-bar", "bg:#000088"),
+    ("progress-bar.used", "bg:#ff0000"),
+]
+
+
+# The default Pygments style, include this by default in case a Pygments lexer
+# is used.
+PYGMENTS_DEFAULT_STYLE = {
+    "pygments.whitespace": "#bbbbbb",
+    "pygments.comment": "italic #408080",
+    "pygments.comment.preproc": "noitalic #bc7a00",
+    "pygments.keyword": "bold #008000",
+    "pygments.keyword.pseudo": "nobold",
+    "pygments.keyword.type": "nobold #b00040",
+    "pygments.operator": "#666666",
+    "pygments.operator.word": "bold #aa22ff",
+    "pygments.name.builtin": "#008000",
+    "pygments.name.function": "#0000ff",
+    "pygments.name.class": "bold #0000ff",
+    "pygments.name.namespace": "bold #0000ff",
+    "pygments.name.exception": "bold #d2413a",
+    "pygments.name.variable": "#19177c",
+    "pygments.name.constant": "#880000",
+    "pygments.name.label": "#a0a000",
+    "pygments.name.entity": "bold #999999",
+    "pygments.name.attribute": "#7d9029",
+    "pygments.name.tag": "bold #008000",
+    "pygments.name.decorator": "#aa22ff",
+    # Note: In Pygments, Token.String is an alias for Token.Literal.String,
+    #       and Token.Number as an alias for Token.Literal.Number.
+    "pygments.literal.string": "#ba2121",
+    "pygments.literal.string.doc": "italic",
+    "pygments.literal.string.interpol": "bold #bb6688",
+    "pygments.literal.string.escape": "bold #bb6622",
+    "pygments.literal.string.regex": "#bb6688",
+    "pygments.literal.string.symbol": "#19177c",
+    "pygments.literal.string.other": "#008000",
+    "pygments.literal.number": "#666666",
+    "pygments.generic.heading": "bold #000080",
+    "pygments.generic.subheading": "bold #800080",
+    "pygments.generic.deleted": "#a00000",
+    "pygments.generic.inserted": "#00a000",
+    "pygments.generic.error": "#ff0000",
+    "pygments.generic.emph": "italic",
+    "pygments.generic.strong": "bold",
+    "pygments.generic.prompt": "bold #000080",
+    "pygments.generic.output": "#888",
+    "pygments.generic.traceback": "#04d",
+    "pygments.error": "border:#ff0000",
+}
+
+
+@memoized()
+def default_ui_style() -> BaseStyle:
+    """
+    Create a default `Style` object.
+    """
+    return merge_styles(
+        [
+            Style(PROMPT_TOOLKIT_STYLE),
+            Style(COLORS_STYLE),
+            Style(WIDGETS_STYLE),
+        ]
+    )
+
+
+@memoized()
+def default_pygments_style() -> Style:
+    """
+    Create a `Style` object that contains the default Pygments style.
+    """
+    return Style.from_dict(PYGMENTS_DEFAULT_STYLE)
diff --git a/src/prompt_toolkit/styles/named_colors.py b/src/prompt_toolkit/styles/named_colors.py
new file mode 100644
index 0000000..37bd6de
--- /dev/null
+++ b/src/prompt_toolkit/styles/named_colors.py
@@ -0,0 +1,161 @@
+"""
+All modern web browsers support these 140 color names.
+Taken from: https://www.w3schools.com/colors/colors_names.asp
+"""
+from typing import Dict
+
+__all__ = [
+    "NAMED_COLORS",
+]
+
+
+NAMED_COLORS: Dict[str, str] = {
+    "AliceBlue": "#f0f8ff",
+    "AntiqueWhite": "#faebd7",
+    "Aqua": "#00ffff",
+    "Aquamarine": "#7fffd4",
+    "Azure": "#f0ffff",
+    "Beige": "#f5f5dc",
+    "Bisque": "#ffe4c4",
+    "Black": "#000000",
+    "BlanchedAlmond": "#ffebcd",
+    "Blue": "#0000ff",
+    "BlueViolet": "#8a2be2",
+    "Brown": "#a52a2a",
+    "BurlyWood": "#deb887",
+    "CadetBlue": "#5f9ea0",
+    "Chartreuse": "#7fff00",
+    "Chocolate": "#d2691e",
+    "Coral": "#ff7f50",
+    "CornflowerBlue": "#6495ed",
+    "Cornsilk": "#fff8dc",
+    "Crimson": "#dc143c",
+    "Cyan": "#00ffff",
+    "DarkBlue": "#00008b",
+    "DarkCyan": "#008b8b",
+    "DarkGoldenRod": "#b8860b",
+    "DarkGray": "#a9a9a9",
+    "DarkGreen": "#006400",
+    "DarkGrey": "#a9a9a9",
+    "DarkKhaki": "#bdb76b",
+    "DarkMagenta": "#8b008b",
+    "DarkOliveGreen": "#556b2f",
+    "DarkOrange": "#ff8c00",
+    "DarkOrchid": "#9932cc",
+    "DarkRed": "#8b0000",
+    "DarkSalmon": "#e9967a",
+    "DarkSeaGreen": "#8fbc8f",
+    "DarkSlateBlue": "#483d8b",
+    "DarkSlateGray": "#2f4f4f",
+    "DarkSlateGrey": "#2f4f4f",
+    "DarkTurquoise": "#00ced1",
+    "DarkViolet": "#9400d3",
+    "DeepPink": "#ff1493",
+    "DeepSkyBlue": "#00bfff",
+    "DimGray": "#696969",
+    "DimGrey": "#696969",
+    "DodgerBlue": "#1e90ff",
+    "FireBrick": "#b22222",
+    "FloralWhite": "#fffaf0",
+    "ForestGreen": "#228b22",
+    "Fuchsia": "#ff00ff",
+    "Gainsboro": "#dcdcdc",
+    "GhostWhite": "#f8f8ff",
+    "Gold": "#ffd700",
+    "GoldenRod": "#daa520",
+    "Gray": "#808080",
+    "Green": "#008000",
+    "GreenYellow": "#adff2f",
+    "Grey": "#808080",
+    "HoneyDew": "#f0fff0",
+    "HotPink": "#ff69b4",
+    "IndianRed": "#cd5c5c",
+    "Indigo": "#4b0082",
+    "Ivory": "#fffff0",
+    "Khaki": "#f0e68c",
+    "Lavender": "#e6e6fa",
+    "LavenderBlush": "#fff0f5",
+    "LawnGreen": "#7cfc00",
+    "LemonChiffon": "#fffacd",
+    "LightBlue": "#add8e6",
+    "LightCoral": "#f08080",
+    "LightCyan": "#e0ffff",
+    "LightGoldenRodYellow": "#fafad2",
+    "LightGray": "#d3d3d3",
+    "LightGreen": "#90ee90",
+    "LightGrey": "#d3d3d3",
+    "LightPink": "#ffb6c1",
+    "LightSalmon": "#ffa07a",
+    "LightSeaGreen": "#20b2aa",
+    "LightSkyBlue": "#87cefa",
+    "LightSlateGray": "#778899",
+    "LightSlateGrey": "#778899",
+    "LightSteelBlue": "#b0c4de",
+    "LightYellow": "#ffffe0",
+    "Lime": "#00ff00",
+    "LimeGreen": "#32cd32",
+    "Linen": "#faf0e6",
+    "Magenta": "#ff00ff",
+    "Maroon": "#800000",
+    "MediumAquaMarine": "#66cdaa",
+    "MediumBlue": "#0000cd",
+    "MediumOrchid": "#ba55d3",
+    "MediumPurple": "#9370db",
+    "MediumSeaGreen": "#3cb371",
+    "MediumSlateBlue": "#7b68ee",
+    "MediumSpringGreen": "#00fa9a",
+    "MediumTurquoise": "#48d1cc",
+    "MediumVioletRed": "#c71585",
+    "MidnightBlue": "#191970",
+    "MintCream": "#f5fffa",
+    "MistyRose": "#ffe4e1",
+    "Moccasin": "#ffe4b5",
+    "NavajoWhite": "#ffdead",
+    "Navy": "#000080",
+    "OldLace": "#fdf5e6",
+    "Olive": "#808000",
+    "OliveDrab": "#6b8e23",
+    "Orange": "#ffa500",
+    "OrangeRed": "#ff4500",
+    "Orchid": "#da70d6",
+    "PaleGoldenRod": "#eee8aa",
+    "PaleGreen": "#98fb98",
+    "PaleTurquoise": "#afeeee",
+    "PaleVioletRed": "#db7093",
+    "PapayaWhip": "#ffefd5",
+    "PeachPuff": "#ffdab9",
+    "Peru": "#cd853f",
+    "Pink": "#ffc0cb",
+    "Plum": "#dda0dd",
+    "PowderBlue": "#b0e0e6",
+    "Purple": "#800080",
+    "RebeccaPurple": "#663399",
+    "Red": "#ff0000",
+    "RosyBrown": "#bc8f8f",
+    "RoyalBlue": "#4169e1",
+    "SaddleBrown": "#8b4513",
+    "Salmon": "#fa8072",
+    "SandyBrown": "#f4a460",
+    "SeaGreen": "#2e8b57",
+    "SeaShell": "#fff5ee",
+    "Sienna": "#a0522d",
+    "Silver": "#c0c0c0",
+    "SkyBlue": "#87ceeb",
+    "SlateBlue": "#6a5acd",
+    "SlateGray": "#708090",
+    "SlateGrey": "#708090",
+    "Snow": "#fffafa",
+    "SpringGreen": "#00ff7f",
+    "SteelBlue": "#4682b4",
+    "Tan": "#d2b48c",
+    "Teal": "#008080",
+    "Thistle": "#d8bfd8",
+    "Tomato": "#ff6347",
+    "Turquoise": "#40e0d0",
+    "Violet": "#ee82ee",
+    "Wheat": "#f5deb3",
+    "White": "#ffffff",
+    "WhiteSmoke": "#f5f5f5",
+    "Yellow": "#ffff00",
+    "YellowGreen": "#9acd32",
+}
diff --git a/src/prompt_toolkit/styles/pygments.py b/src/prompt_toolkit/styles/pygments.py
new file mode 100644
index 0000000..382e5e3
--- /dev/null
+++ b/src/prompt_toolkit/styles/pygments.py
@@ -0,0 +1,67 @@
+"""
+Adaptor for building prompt_toolkit styles, starting from a Pygments style.
+
+Usage::
+
+    from pygments.styles.tango import TangoStyle
+    style = style_from_pygments_cls(pygments_style_cls=TangoStyle)
+"""
+from typing import TYPE_CHECKING, Dict, Type
+
+from .style import Style
+
+if TYPE_CHECKING:
+    from pygments.style import Style as PygmentsStyle
+    from pygments.token import Token
+
+
+__all__ = [
+    "style_from_pygments_cls",
+    "style_from_pygments_dict",
+    "pygments_token_to_classname",
+]
+
+
+def style_from_pygments_cls(pygments_style_cls: Type["PygmentsStyle"]) -> Style:
+    """
+    Shortcut to create a :class:`.Style` instance from a Pygments style class
+    and a style dictionary.
+
+    Example::
+
+        from prompt_toolkit.styles.from_pygments import style_from_pygments_cls
+        from pygments.styles import get_style_by_name
+        style = style_from_pygments_cls(get_style_by_name('monokai'))
+
+    :param pygments_style_cls: Pygments style class to start from.
+    """
+    # Import inline.
+    from pygments.style import Style as PygmentsStyle
+
+    assert issubclass(pygments_style_cls, PygmentsStyle)
+
+    return style_from_pygments_dict(pygments_style_cls.styles)
+
+
+def style_from_pygments_dict(pygments_dict: Dict["Token", str]) -> Style:
+    """
+    Create a :class:`.Style` instance from a Pygments style dictionary.
+    (One that maps Token objects to style strings.)
+    """
+    pygments_style = []
+
+    for token, style in pygments_dict.items():
+        pygments_style.append((pygments_token_to_classname(token), style))
+
+    return Style(pygments_style)
+
+
+def pygments_token_to_classname(token: "Token") -> str:
+    """
+    Turn e.g. `Token.Name.Exception` into `'pygments.name.exception'`.
+
+    (Our Pygments lexer will also turn the tokens that pygments produces in a
+    prompt_toolkit list of fragments that match these styling rules.)
+    """
+    parts = ("pygments",) + token
+    return ".".join(parts).lower()
diff --git a/src/prompt_toolkit/styles/style.py b/src/prompt_toolkit/styles/style.py
new file mode 100644
index 0000000..6e4bd1f
--- /dev/null
+++ b/src/prompt_toolkit/styles/style.py
@@ -0,0 +1,399 @@
+"""
+Tool for creating styles from a dictionary.
+"""
+import itertools
+import re
+import sys
+from enum import Enum
+from typing import Dict, Hashable, List, Set, Tuple, TypeVar
+
+from prompt_toolkit.cache import SimpleCache
+
+from .base import (
+    ANSI_COLOR_NAMES,
+    ANSI_COLOR_NAMES_ALIASES,
+    DEFAULT_ATTRS,
+    Attrs,
+    BaseStyle,
+)
+from .named_colors import NAMED_COLORS
+
+__all__ = [
+    "Style",
+    "parse_color",
+    "Priority",
+    "merge_styles",
+]
+
+_named_colors_lowercase = {k.lower(): v.lstrip("#") for k, v in NAMED_COLORS.items()}
+
+
+def parse_color(text: str) -> str:
+    """
+    Parse/validate color format.
+
+    Like in Pygments, but also support the ANSI color names.
+    (These will map to the colors of the 16 color palette.)
+    """
+    # ANSI color names.
+    if text in ANSI_COLOR_NAMES:
+        return text
+    if text in ANSI_COLOR_NAMES_ALIASES:
+        return ANSI_COLOR_NAMES_ALIASES[text]
+
+    # 140 named colors.
+    try:
+        # Replace by 'hex' value.
+        return _named_colors_lowercase[text.lower()]
+    except KeyError:
+        pass
+
+    # Hex codes.
+    if text[0:1] == "#":
+        col = text[1:]
+
+        # Keep this for backwards-compatibility (Pygments does it).
+        # I don't like the '#' prefix for named colors.
+        if col in ANSI_COLOR_NAMES:
+            return col
+        elif col in ANSI_COLOR_NAMES_ALIASES:
+            return ANSI_COLOR_NAMES_ALIASES[col]
+
+        # 6 digit hex color.
+        elif len(col) == 6:
+            return col
+
+        # 3 digit hex color.
+        elif len(col) == 3:
+            return col[0] * 2 + col[1] * 2 + col[2] * 2
+
+    # Default.
+    elif text in ("", "default"):
+        return text
+
+    raise ValueError("Wrong color format %r" % text)
+
+
+# Attributes, when they are not filled in by a style. None means that we take
+# the value from the parent.
+_EMPTY_ATTRS = Attrs(
+    color=None,
+    bgcolor=None,
+    bold=None,
+    underline=None,
+    strike=None,
+    italic=None,
+    blink=None,
+    reverse=None,
+    hidden=None,
+)
+
+
+def _expand_classname(classname: str) -> List[str]:
+    """
+    Split a single class name at the `.` operator, and build a list of classes.
+
+    E.g. 'a.b.c' becomes ['a', 'a.b', 'a.b.c']
+    """
+    result = []
+    parts = classname.split(".")
+
+    for i in range(1, len(parts) + 1):
+        result.append(".".join(parts[:i]).lower())
+
+    return result
+
+
+def _parse_style_str(style_str: str) -> Attrs:
+    """
+    Take a style string, e.g.  'bg:red #88ff00 class:title'
+    and return a `Attrs` instance.
+    """
+    # Start from default Attrs.
+    if "noinherit" in style_str:
+        attrs = DEFAULT_ATTRS
+    else:
+        attrs = _EMPTY_ATTRS
+
+    # Now update with the given attributes.
+    for part in style_str.split():
+        if part == "noinherit":
+            pass
+        elif part == "bold":
+            attrs = attrs._replace(bold=True)
+        elif part == "nobold":
+            attrs = attrs._replace(bold=False)
+        elif part == "italic":
+            attrs = attrs._replace(italic=True)
+        elif part == "noitalic":
+            attrs = attrs._replace(italic=False)
+        elif part == "underline":
+            attrs = attrs._replace(underline=True)
+        elif part == "nounderline":
+            attrs = attrs._replace(underline=False)
+        elif part == "strike":
+            attrs = attrs._replace(strike=True)
+        elif part == "nostrike":
+            attrs = attrs._replace(strike=False)
+
+        # prompt_toolkit extensions. Not in Pygments.
+        elif part == "blink":
+            attrs = attrs._replace(blink=True)
+        elif part == "noblink":
+            attrs = attrs._replace(blink=False)
+        elif part == "reverse":
+            attrs = attrs._replace(reverse=True)
+        elif part == "noreverse":
+            attrs = attrs._replace(reverse=False)
+        elif part == "hidden":
+            attrs = attrs._replace(hidden=True)
+        elif part == "nohidden":
+            attrs = attrs._replace(hidden=False)
+
+        # Pygments properties that we ignore.
+        elif part in ("roman", "sans", "mono"):
+            pass
+        elif part.startswith("border:"):
+            pass
+
+        # Ignore pieces in between square brackets. This is internal stuff.
+        # Like '[transparent]' or '[set-cursor-position]'.
+        elif part.startswith("[") and part.endswith("]"):
+            pass
+
+        # Colors.
+        elif part.startswith("bg:"):
+            attrs = attrs._replace(bgcolor=parse_color(part[3:]))
+        elif part.startswith("fg:"):  # The 'fg:' prefix is optional.
+            attrs = attrs._replace(color=parse_color(part[3:]))
+        else:
+            attrs = attrs._replace(color=parse_color(part))
+
+    return attrs
+
+
+CLASS_NAMES_RE = re.compile(r"^[a-z0-9.\s_-]*$")  # This one can't contain a comma!
+
+
+class Priority(Enum):
+    """
+    The priority of the rules, when a style is created from a dictionary.
+
+    In a `Style`, rules that are defined later will always override previous
+    defined rules, however in a dictionary, the key order was arbitrary before
+    Python 3.6. This means that the style could change at random between rules.
+
+    We have two options:
+
+    - `DICT_KEY_ORDER`: This means, iterate through the dictionary, and take
+       the key/value pairs in order as they come. This is a good option if you
+       have Python >3.6. Rules at the end will override rules at the beginning.
+    - `MOST_PRECISE`: keys that are defined with most precision will get higher
+      priority. (More precise means: more elements.)
+    """
+
+    DICT_KEY_ORDER = "KEY_ORDER"
+    MOST_PRECISE = "MOST_PRECISE"
+
+
+# We don't support Python versions older than 3.6 anymore, so we can always
+# depend on dictionary ordering. This is the default.
+default_priority = Priority.DICT_KEY_ORDER
+
+
+class Style(BaseStyle):
+    """
+    Create a ``Style`` instance from a list of style rules.
+
+    The `style_rules` is supposed to be a list of ('classnames', 'style') tuples.
+    The classnames are a whitespace separated string of class names and the
+    style string is just like a Pygments style definition, but with a few
+    additions: it supports 'reverse' and 'blink'.
+
+    Later rules always override previous rules.
+
+    Usage::
+
+        Style([
+            ('title', '#ff0000 bold underline'),
+            ('something-else', 'reverse'),
+            ('class1 class2', 'reverse'),
+        ])
+
+    The ``from_dict`` classmethod is similar, but takes a dictionary as input.
+    """
+
+    def __init__(self, style_rules: List[Tuple[str, str]]) -> None:
+        class_names_and_attrs = []
+
+        # Loop through the rules in the order they were defined.
+        # Rules that are defined later get priority.
+        for class_names, style_str in style_rules:
+            assert CLASS_NAMES_RE.match(class_names), repr(class_names)
+
+            # The order of the class names doesn't matter.
+            # (But the order of rules does matter.)
+            class_names_set = frozenset(class_names.lower().split())
+            attrs = _parse_style_str(style_str)
+
+            class_names_and_attrs.append((class_names_set, attrs))
+
+        self._style_rules = style_rules
+        self.class_names_and_attrs = class_names_and_attrs
+
+    @property
+    def style_rules(self) -> List[Tuple[str, str]]:
+        return self._style_rules
+
+    @classmethod
+    def from_dict(
+        cls, style_dict: Dict[str, str], priority: Priority = default_priority
+    ) -> "Style":
+        """
+        :param style_dict: Style dictionary.
+        :param priority: `Priority` value.
+        """
+        if priority == Priority.MOST_PRECISE:
+
+            def key(item: Tuple[str, str]) -> int:
+                # Split on '.' and whitespace. Count elements.
+                return sum(len(i.split(".")) for i in item[0].split())
+
+            return cls(sorted(style_dict.items(), key=key))
+        else:
+            return cls(list(style_dict.items()))
+
+    def get_attrs_for_style_str(
+        self, style_str: str, default: Attrs = DEFAULT_ATTRS
+    ) -> Attrs:
+        """
+        Get `Attrs` for the given style string.
+        """
+        list_of_attrs = [default]
+        class_names: Set[str] = set()
+
+        # Apply default styling.
+        for names, attr in self.class_names_and_attrs:
+            if not names:
+                list_of_attrs.append(attr)
+
+        # Go from left to right through the style string. Things on the right
+        # take precedence.
+        for part in style_str.split():
+            # This part represents a class.
+            # Do lookup of this class name in the style definition, as well
+            # as all class combinations that we have so far.
+            if part.startswith("class:"):
+                # Expand all class names (comma separated list).
+                new_class_names = []
+                for p in part[6:].lower().split(","):
+                    new_class_names.extend(_expand_classname(p))
+
+                for new_name in new_class_names:
+                    # Build a set of all possible class combinations to be applied.
+                    combos = set()
+                    combos.add(frozenset([new_name]))
+
+                    for count in range(1, len(class_names) + 1):
+                        for c2 in itertools.combinations(class_names, count):
+                            combos.add(frozenset(c2 + (new_name,)))
+
+                    # Apply the styles that match these class names.
+                    for names, attr in self.class_names_and_attrs:
+                        if names in combos:
+                            list_of_attrs.append(attr)
+
+                    class_names.add(new_name)
+
+            # Process inline style.
+            else:
+                inline_attrs = _parse_style_str(part)
+                list_of_attrs.append(inline_attrs)
+
+        return _merge_attrs(list_of_attrs)
+
+    def invalidation_hash(self) -> Hashable:
+        return id(self.class_names_and_attrs)
+
+
+_T = TypeVar("_T")
+
+
+def _merge_attrs(list_of_attrs: List[Attrs]) -> Attrs:
+    """
+    Take a list of :class:`.Attrs` instances and merge them into one.
+    Every `Attr` in the list can override the styling of the previous one. So,
+    the last one has highest priority.
+    """
+
+    def _or(*values: _T) -> _T:
+        "Take first not-None value, starting at the end."
+        for v in values[::-1]:
+            if v is not None:
+                return v
+        raise ValueError  # Should not happen, there's always one non-null value.
+
+    return Attrs(
+        color=_or("", *[a.color for a in list_of_attrs]),
+        bgcolor=_or("", *[a.bgcolor for a in list_of_attrs]),
+        bold=_or(False, *[a.bold for a in list_of_attrs]),
+        underline=_or(False, *[a.underline for a in list_of_attrs]),
+        strike=_or(False, *[a.strike for a in list_of_attrs]),
+        italic=_or(False, *[a.italic for a in list_of_attrs]),
+        blink=_or(False, *[a.blink for a in list_of_attrs]),
+        reverse=_or(False, *[a.reverse for a in list_of_attrs]),
+        hidden=_or(False, *[a.hidden for a in list_of_attrs]),
+    )
+
+
+def merge_styles(styles: List[BaseStyle]) -> "_MergedStyle":
+    """
+    Merge multiple `Style` objects.
+    """
+    styles = [s for s in styles if s is not None]
+    return _MergedStyle(styles)
+
+
+class _MergedStyle(BaseStyle):
+    """
+    Merge multiple `Style` objects into one.
+    This is supposed to ensure consistency: if any of the given styles changes,
+    then this style will be updated.
+    """
+
+    # NOTE: previously, we used an algorithm where we did not generate the
+    #       combined style. Instead this was a proxy that called one style
+    #       after the other, passing the outcome of the previous style as the
+    #       default for the next one. This did not work, because that way, the
+    #       priorities like described in the `Style` class don't work.
+    #       'class:aborted' was for instance never displayed in gray, because
+    #       the next style specified a default color for any text. (The
+    #       explicit styling of class:aborted should have taken priority,
+    #       because it was more precise.)
+    def __init__(self, styles: List[BaseStyle]) -> None:
+        self.styles = styles
+        self._style: SimpleCache[Hashable, Style] = SimpleCache(maxsize=1)
+
+    @property
+    def _merged_style(self) -> Style:
+        "The `Style` object that has the other styles merged together."
+
+        def get() -> Style:
+            return Style(self.style_rules)
+
+        return self._style.get(self.invalidation_hash(), get)
+
+    @property
+    def style_rules(self) -> List[Tuple[str, str]]:
+        style_rules = []
+        for s in self.styles:
+            style_rules.extend(s.style_rules)
+        return style_rules
+
+    def get_attrs_for_style_str(
+        self, style_str: str, default: Attrs = DEFAULT_ATTRS
+    ) -> Attrs:
+        return self._merged_style.get_attrs_for_style_str(style_str, default)
+
+    def invalidation_hash(self) -> Hashable:
+        return tuple(s.invalidation_hash() for s in self.styles)
diff --git a/src/prompt_toolkit/styles/style_transformation.py b/src/prompt_toolkit/styles/style_transformation.py
new file mode 100644
index 0000000..91308f9
--- /dev/null
+++ b/src/prompt_toolkit/styles/style_transformation.py
@@ -0,0 +1,375 @@
+"""
+Collection of style transformations.
+
+Think of it as a kind of color post processing after the rendering is done.
+This could be used for instance to change the contrast/saturation; swap light
+and dark colors or even change certain colors for other colors.
+
+When the UI is rendered, these transformations can be applied right after the
+style strings are turned into `Attrs` objects that represent the actual
+formatting.
+"""
+from abc import ABCMeta, abstractmethod
+from colorsys import hls_to_rgb, rgb_to_hls
+from typing import Callable, Hashable, Optional, Sequence, Tuple, Union
+
+from prompt_toolkit.cache import memoized
+from prompt_toolkit.filters import FilterOrBool, to_filter
+from prompt_toolkit.utils import AnyFloat, to_float, to_str
+
+from .base import ANSI_COLOR_NAMES, Attrs
+from .style import parse_color
+
+__all__ = [
+    "StyleTransformation",
+    "SwapLightAndDarkStyleTransformation",
+    "ReverseStyleTransformation",
+    "SetDefaultColorStyleTransformation",
+    "AdjustBrightnessStyleTransformation",
+    "DummyStyleTransformation",
+    "ConditionalStyleTransformation",
+    "DynamicStyleTransformation",
+    "merge_style_transformations",
+]
+
+
+class StyleTransformation(metaclass=ABCMeta):
+    """
+    Base class for any style transformation.
+    """
+
+    @abstractmethod
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        """
+        Take an `Attrs` object and return a new `Attrs` object.
+
+        Remember that the color formats can be either "ansi..." or a 6 digit
+        lowercase hexadecimal color (without '#' prefix).
+        """
+
+    def invalidation_hash(self) -> Hashable:
+        """
+        When this changes, the cache should be invalidated.
+        """
+        return f"{self.__class__.__name__}-{id(self)}"
+
+
+class SwapLightAndDarkStyleTransformation(StyleTransformation):
+    """
+    Turn dark colors into light colors and the other way around.
+
+    This is meant to make color schemes that work on a dark background usable
+    on a light background (and the other way around).
+
+    Notice that this doesn't swap foreground and background like "reverse"
+    does. It turns light green into dark green and the other way around.
+    Foreground and background colors are considered individually.
+
+    Also notice that when <reverse> is used somewhere and no colors are given
+    in particular (like what is the default for the bottom toolbar), then this
+    doesn't change anything. This is what makes sense, because when the
+    'default' color is chosen, it's what works best for the terminal, and
+    reverse works good with that.
+    """
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        """
+        Return the `Attrs` used when opposite luminosity should be used.
+        """
+        # Reverse colors.
+        attrs = attrs._replace(color=get_opposite_color(attrs.color))
+        attrs = attrs._replace(bgcolor=get_opposite_color(attrs.bgcolor))
+
+        return attrs
+
+
+class ReverseStyleTransformation(StyleTransformation):
+    """
+    Swap the 'reverse' attribute.
+
+    (This is still experimental.)
+    """
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        return attrs._replace(reverse=not attrs.reverse)
+
+
+class SetDefaultColorStyleTransformation(StyleTransformation):
+    """
+    Set default foreground/background color for output that doesn't specify
+    anything. This is useful for overriding the terminal default colors.
+
+    :param fg: Color string or callable that returns a color string for the
+        foreground.
+    :param bg: Like `fg`, but for the background.
+    """
+
+    def __init__(
+        self, fg: Union[str, Callable[[], str]], bg: Union[str, Callable[[], str]]
+    ) -> None:
+
+        self.fg = fg
+        self.bg = bg
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        if attrs.bgcolor in ("", "default"):
+            attrs = attrs._replace(bgcolor=parse_color(to_str(self.bg)))
+
+        if attrs.color in ("", "default"):
+            attrs = attrs._replace(color=parse_color(to_str(self.fg)))
+
+        return attrs
+
+    def invalidation_hash(self) -> Hashable:
+        return (
+            "set-default-color",
+            to_str(self.fg),
+            to_str(self.bg),
+        )
+
+
+class AdjustBrightnessStyleTransformation(StyleTransformation):
+    """
+    Adjust the brightness to improve the rendering on either dark or light
+    backgrounds.
+
+    For dark backgrounds, it's best to increase `min_brightness`. For light
+    backgrounds it's best to decrease `max_brightness`. Usually, only one
+    setting is adjusted.
+
+    This will only change the brightness for text that has a foreground color
+    defined, but no background color. It works best for 256 or true color
+    output.
+
+    .. note:: Notice that there is no universal way to detect whether the
+              application is running in a light or dark terminal. As a
+              developer of an command line application, you'll have to make
+              this configurable for the user.
+
+    :param min_brightness: Float between 0.0 and 1.0 or a callable that returns
+        a float.
+    :param max_brightness: Float between 0.0 and 1.0 or a callable that returns
+        a float.
+    """
+
+    def __init__(
+        self, min_brightness: AnyFloat = 0.0, max_brightness: AnyFloat = 1.0
+    ) -> None:
+
+        self.min_brightness = min_brightness
+        self.max_brightness = max_brightness
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        min_brightness = to_float(self.min_brightness)
+        max_brightness = to_float(self.max_brightness)
+        assert 0 <= min_brightness <= 1
+        assert 0 <= max_brightness <= 1
+
+        # Don't do anything if the whole brightness range is acceptable.
+        # This also avoids turning ansi colors into RGB sequences.
+        if min_brightness == 0.0 and max_brightness == 1.0:
+            return attrs
+
+        # If a foreground color is given without a background color.
+        no_background = not attrs.bgcolor or attrs.bgcolor == "default"
+        has_fgcolor = attrs.color and attrs.color != "ansidefault"
+
+        if has_fgcolor and no_background:
+            # Calculate new RGB values.
+            r, g, b = self._color_to_rgb(attrs.color or "")
+            hue, brightness, saturation = rgb_to_hls(r, g, b)
+            brightness = self._interpolate_brightness(
+                brightness, min_brightness, max_brightness
+            )
+            r, g, b = hls_to_rgb(hue, brightness, saturation)
+            new_color = f"{int(r * 255):02x}{int(g * 255):02x}{int(b * 255):02x}"
+
+            attrs = attrs._replace(color=new_color)
+
+        return attrs
+
+    def _color_to_rgb(self, color: str) -> Tuple[float, float, float]:
+        """
+        Parse `style.Attrs` color into RGB tuple.
+        """
+        # Do RGB lookup for ANSI colors.
+        try:
+            from prompt_toolkit.output.vt100 import ANSI_COLORS_TO_RGB
+
+            r, g, b = ANSI_COLORS_TO_RGB[color]
+            return r / 255.0, g / 255.0, b / 255.0
+        except KeyError:
+            pass
+
+        # Parse RRGGBB format.
+        return (
+            int(color[0:2], 16) / 255.0,
+            int(color[2:4], 16) / 255.0,
+            int(color[4:6], 16) / 255.0,
+        )
+
+        # NOTE: we don't have to support named colors here. They are already
+        #       transformed into RGB values in `style.parse_color`.
+
+    def _interpolate_brightness(
+        self, value: float, min_brightness: float, max_brightness: float
+    ) -> float:
+        """
+        Map the brightness to the (min_brightness..max_brightness) range.
+        """
+        return min_brightness + (max_brightness - min_brightness) * value
+
+    def invalidation_hash(self) -> Hashable:
+        return (
+            "adjust-brightness",
+            to_float(self.min_brightness),
+            to_float(self.max_brightness),
+        )
+
+
+class DummyStyleTransformation(StyleTransformation):
+    """
+    Don't transform anything at all.
+    """
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        return attrs
+
+    def invalidation_hash(self) -> Hashable:
+        # Always return the same hash for these dummy instances.
+        return "dummy-style-transformation"
+
+
+class DynamicStyleTransformation(StyleTransformation):
+    """
+    StyleTransformation class that can dynamically returns any
+    `StyleTransformation`.
+
+    :param get_style_transformation: Callable that returns a
+        :class:`.StyleTransformation` instance.
+    """
+
+    def __init__(
+        self, get_style_transformation: Callable[[], Optional[StyleTransformation]]
+    ) -> None:
+
+        self.get_style_transformation = get_style_transformation
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        style_transformation = (
+            self.get_style_transformation() or DummyStyleTransformation()
+        )
+        return style_transformation.transform_attrs(attrs)
+
+    def invalidation_hash(self) -> Hashable:
+        style_transformation = (
+            self.get_style_transformation() or DummyStyleTransformation()
+        )
+        return style_transformation.invalidation_hash()
+
+
+class ConditionalStyleTransformation(StyleTransformation):
+    """
+    Apply the style transformation depending on a condition.
+    """
+
+    def __init__(
+        self, style_transformation: StyleTransformation, filter: FilterOrBool
+    ) -> None:
+
+        self.style_transformation = style_transformation
+        self.filter = to_filter(filter)
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        if self.filter():
+            return self.style_transformation.transform_attrs(attrs)
+        return attrs
+
+    def invalidation_hash(self) -> Hashable:
+        return (self.filter(), self.style_transformation.invalidation_hash())
+
+
+class _MergedStyleTransformation(StyleTransformation):
+    def __init__(self, style_transformations: Sequence[StyleTransformation]) -> None:
+        self.style_transformations = style_transformations
+
+    def transform_attrs(self, attrs: Attrs) -> Attrs:
+        for transformation in self.style_transformations:
+            attrs = transformation.transform_attrs(attrs)
+        return attrs
+
+    def invalidation_hash(self) -> Hashable:
+        return tuple(t.invalidation_hash() for t in self.style_transformations)
+
+
+def merge_style_transformations(
+    style_transformations: Sequence[StyleTransformation],
+) -> StyleTransformation:
+    """
+    Merge multiple transformations together.
+    """
+    return _MergedStyleTransformation(style_transformations)
+
+
+# Dictionary that maps ANSI color names to their opposite. This is useful for
+# turning color schemes that are optimized for a black background usable for a
+# white background.
+OPPOSITE_ANSI_COLOR_NAMES = {
+    "ansidefault": "ansidefault",
+    "ansiblack": "ansiwhite",
+    "ansired": "ansibrightred",
+    "ansigreen": "ansibrightgreen",
+    "ansiyellow": "ansibrightyellow",
+    "ansiblue": "ansibrightblue",
+    "ansimagenta": "ansibrightmagenta",
+    "ansicyan": "ansibrightcyan",
+    "ansigray": "ansibrightblack",
+    "ansiwhite": "ansiblack",
+    "ansibrightred": "ansired",
+    "ansibrightgreen": "ansigreen",
+    "ansibrightyellow": "ansiyellow",
+    "ansibrightblue": "ansiblue",
+    "ansibrightmagenta": "ansimagenta",
+    "ansibrightcyan": "ansicyan",
+    "ansibrightblack": "ansigray",
+}
+assert set(OPPOSITE_ANSI_COLOR_NAMES.keys()) == set(ANSI_COLOR_NAMES)
+assert set(OPPOSITE_ANSI_COLOR_NAMES.values()) == set(ANSI_COLOR_NAMES)
+
+
+@memoized()
+def get_opposite_color(colorname: Optional[str]) -> Optional[str]:
+    """
+    Take a color name in either 'ansi...' format or 6 digit RGB, return the
+    color of opposite luminosity (same hue/saturation).
+
+    This is used for turning color schemes that work on a light background
+    usable on a dark background.
+    """
+    if colorname is None:  # Because color/bgcolor can be None in `Attrs`.
+        return None
+
+    # Special values.
+    if colorname in ("", "default"):
+        return colorname
+
+    # Try ANSI color names.
+    try:
+        return OPPOSITE_ANSI_COLOR_NAMES[colorname]
+    except KeyError:
+        # Try 6 digit RGB colors.
+        r = int(colorname[:2], 16) / 255.0
+        g = int(colorname[2:4], 16) / 255.0
+        b = int(colorname[4:6], 16) / 255.0
+
+        h, l, s = rgb_to_hls(r, g, b)
+
+        l = 1 - l
+
+        r, g, b = hls_to_rgb(h, l, s)
+
+        r = int(r * 255)
+        g = int(g * 255)
+        b = int(b * 255)
+
+        return f"{r:02x}{g:02x}{b:02x}"
diff --git a/src/prompt_toolkit/token.py b/src/prompt_toolkit/token.py
new file mode 100644
index 0000000..76fd9c4
--- /dev/null
+++ b/src/prompt_toolkit/token.py
@@ -0,0 +1,8 @@
+"""
+"""
+
+__all__ = [
+    "ZeroWidthEscape",
+]
+
+ZeroWidthEscape = "[ZeroWidthEscape]"
diff --git a/src/prompt_toolkit/utils.py b/src/prompt_toolkit/utils.py
new file mode 100644
index 0000000..4ceded3
--- /dev/null
+++ b/src/prompt_toolkit/utils.py
@@ -0,0 +1,328 @@
+import os
+import signal
+import sys
+import threading
+from collections import deque
+from typing import (
+    Callable,
+    ContextManager,
+    Deque,
+    Dict,
+    Generator,
+    Generic,
+    List,
+    Optional,
+    TypeVar,
+    Union,
+)
+
+from wcwidth import wcwidth
+
+__all__ = [
+    "Event",
+    "DummyContext",
+    "get_cwidth",
+    "suspend_to_background_supported",
+    "is_conemu_ansi",
+    "is_windows",
+    "in_main_thread",
+    "get_bell_environment_variable",
+    "get_term_environment_variable",
+    "take_using_weights",
+    "to_str",
+    "to_int",
+    "AnyFloat",
+    "to_float",
+    "is_dumb_terminal",
+]
+
+# Used to ensure sphinx autodoc does not try to import platform-specific
+# stuff when documenting win32.py modules.
+SPHINX_AUTODOC_RUNNING = "sphinx.ext.autodoc" in sys.modules
+
+_Sender = TypeVar("_Sender", covariant=True)
+
+
+class Event(Generic[_Sender]):
+    """
+    Simple event to which event handlers can be attached. For instance::
+
+        class Cls:
+            def __init__(self):
+                # Define event. The first parameter is the sender.
+                self.event = Event(self)
+
+        obj = Cls()
+
+        def handler(sender):
+            pass
+
+        # Add event handler by using the += operator.
+        obj.event += handler
+
+        # Fire event.
+        obj.event()
+    """
+
+    def __init__(
+        self, sender: _Sender, handler: Optional[Callable[[_Sender], None]] = None
+    ) -> None:
+        self.sender = sender
+        self._handlers: List[Callable[[_Sender], None]] = []
+
+        if handler is not None:
+            self += handler
+
+    def __call__(self) -> None:
+        "Fire event."
+        for handler in self._handlers:
+            handler(self.sender)
+
+    def fire(self) -> None:
+        "Alias for just calling the event."
+        self()
+
+    def add_handler(self, handler: Callable[[_Sender], None]) -> None:
+        """
+        Add another handler to this callback.
+        (Handler should be a callable that takes exactly one parameter: the
+        sender object.)
+        """
+        # Add to list of event handlers.
+        self._handlers.append(handler)
+
+    def remove_handler(self, handler: Callable[[_Sender], None]) -> None:
+        """
+        Remove a handler from this callback.
+        """
+        if handler in self._handlers:
+            self._handlers.remove(handler)
+
+    def __iadd__(self, handler: Callable[[_Sender], None]) -> "Event[_Sender]":
+        """
+        `event += handler` notation for adding a handler.
+        """
+        self.add_handler(handler)
+        return self
+
+    def __isub__(self, handler: Callable[[_Sender], None]) -> "Event[_Sender]":
+        """
+        `event -= handler` notation for removing a handler.
+        """
+        self.remove_handler(handler)
+        return self
+
+
+class DummyContext(ContextManager[None]):
+    """
+    (contextlib.nested is not available on Py3)
+    """
+
+    def __enter__(self) -> None:
+        pass
+
+    def __exit__(self, *a: object) -> None:
+        pass
+
+
+class _CharSizesCache(Dict[str, int]):
+    """
+    Cache for wcwidth sizes.
+    """
+
+    LONG_STRING_MIN_LEN = 64  # Minimum string length for considering it long.
+    MAX_LONG_STRINGS = 16  # Maximum number of long strings to remember.
+
+    def __init__(self) -> None:
+        super().__init__()
+        # Keep track of the "long" strings in this cache.
+        self._long_strings: Deque[str] = deque()
+
+    def __missing__(self, string: str) -> int:
+        # Note: We use the `max(0, ...` because some non printable control
+        #       characters, like e.g. Ctrl-underscore get a -1 wcwidth value.
+        #       It can be possible that these characters end up in the input
+        #       text.
+        result: int
+        if len(string) == 1:
+            result = max(0, wcwidth(string))
+        else:
+            result = sum(self[c] for c in string)
+
+        # Store in cache.
+        self[string] = result
+
+        # Rotate long strings.
+        # (It's hard to tell what we can consider short...)
+        if len(string) > self.LONG_STRING_MIN_LEN:
+            long_strings = self._long_strings
+            long_strings.append(string)
+
+            if len(long_strings) > self.MAX_LONG_STRINGS:
+                key_to_remove = long_strings.popleft()
+                if key_to_remove in self:
+                    del self[key_to_remove]
+
+        return result
+
+
+_CHAR_SIZES_CACHE = _CharSizesCache()
+
+
+def get_cwidth(string: str) -> int:
+    """
+    Return width of a string. Wrapper around ``wcwidth``.
+    """
+    return _CHAR_SIZES_CACHE[string]
+
+
+def suspend_to_background_supported() -> bool:
+    """
+    Returns `True` when the Python implementation supports
+    suspend-to-background. This is typically `False' on Windows systems.
+    """
+    return hasattr(signal, "SIGTSTP")
+
+
+def is_windows() -> bool:
+    """
+    True when we are using Windows.
+    """
+    return sys.platform == "win32"  # Not 'darwin' or 'linux2'
+
+
+def is_windows_vt100_supported() -> bool:
+    """
+    True when we are using Windows, but VT100 escape sequences are supported.
+    """
+    if sys.platform == "win32":
+        # Import needs to be inline. Windows libraries are not always available.
+        from prompt_toolkit.output.windows10 import is_win_vt100_enabled
+
+        return is_win_vt100_enabled()
+
+    return False
+
+
+def is_conemu_ansi() -> bool:
+    """
+    True when the ConEmu Windows console is used.
+    """
+    return sys.platform == "win32" and os.environ.get("ConEmuANSI", "OFF") == "ON"
+
+
+def in_main_thread() -> bool:
+    """
+    True when the current thread is the main thread.
+    """
+    return threading.current_thread().__class__.__name__ == "_MainThread"
+
+
+def get_bell_environment_variable() -> bool:
+    """
+    True if env variable is set to true (true, TRUE, TrUe, 1).
+    """
+    value = os.environ.get("PROMPT_TOOLKIT_BELL", "true")
+    return value.lower() in ("1", "true")
+
+
+def get_term_environment_variable() -> str:
+    "Return the $TERM environment variable."
+    return os.environ.get("TERM", "")
+
+
+_T = TypeVar("_T")
+
+
+def take_using_weights(
+    items: List[_T], weights: List[int]
+) -> Generator[_T, None, None]:
+    """
+    Generator that keeps yielding items from the items list, in proportion to
+    their weight. For instance::
+
+        # Getting the first 70 items from this generator should have yielded 10
+        # times A, 20 times B and 40 times C, all distributed equally..
+        take_using_weights(['A', 'B', 'C'], [5, 10, 20])
+
+    :param items: List of items to take from.
+    :param weights: Integers representing the weight. (Numbers have to be
+                    integers, not floats.)
+    """
+    assert len(items) == len(weights)
+    assert len(items) > 0
+
+    # Remove items with zero-weight.
+    items2 = []
+    weights2 = []
+    for item, w in zip(items, weights):
+        if w > 0:
+            items2.append(item)
+            weights2.append(w)
+
+    items = items2
+    weights = weights2
+
+    # Make sure that we have some items left.
+    if not items:
+        raise ValueError("Did't got any items with a positive weight.")
+
+    #
+    already_taken = [0 for i in items]
+    item_count = len(items)
+    max_weight = max(weights)
+
+    i = 0
+    while True:
+        # Each iteration of this loop, we fill up until by (total_weight/max_weight).
+        adding = True
+        while adding:
+            adding = False
+
+            for item_i, item, weight in zip(range(item_count), items, weights):
+                if already_taken[item_i] < i * weight / float(max_weight):
+                    yield item
+                    already_taken[item_i] += 1
+                    adding = True
+
+        i += 1
+
+
+def to_str(value: Union[Callable[[], str], str]) -> str:
+    "Turn callable or string into string."
+    if callable(value):
+        return to_str(value())
+    else:
+        return str(value)
+
+
+def to_int(value: Union[Callable[[], int], int]) -> int:
+    "Turn callable or int into int."
+    if callable(value):
+        return to_int(value())
+    else:
+        return int(value)
+
+
+AnyFloat = Union[Callable[[], float], float]
+
+
+def to_float(value: AnyFloat) -> float:
+    "Turn callable or float into float."
+    if callable(value):
+        return to_float(value())
+    else:
+        return float(value)
+
+
+def is_dumb_terminal(term: Optional[str] = None) -> bool:
+    """
+    True if this terminal type is considered "dumb".
+
+    If so, we should fall back to the simplest possible form of line editing,
+    without cursor positioning and color support.
+    """
+    if term is None:
+        return is_dumb_terminal(os.environ.get("TERM", ""))
+
+    return term.lower() in ["dumb", "unknown"]
diff --git a/src/prompt_toolkit/validation.py b/src/prompt_toolkit/validation.py
new file mode 100644
index 0000000..8bdffff
--- /dev/null
+++ b/src/prompt_toolkit/validation.py
@@ -0,0 +1,194 @@
+"""
+Input validation for a `Buffer`.
+(Validators will be called before accepting input.)
+"""
+from abc import ABCMeta, abstractmethod
+from typing import Callable, Optional
+
+from prompt_toolkit.eventloop import run_in_executor_with_context
+
+from .document import Document
+from .filters import FilterOrBool, to_filter
+
+__all__ = [
+    "ConditionalValidator",
+    "ValidationError",
+    "Validator",
+    "ThreadedValidator",
+    "DummyValidator",
+    "DynamicValidator",
+]
+
+
+class ValidationError(Exception):
+    """
+    Error raised by :meth:`.Validator.validate`.
+
+    :param cursor_position: The cursor position where the error occurred.
+    :param message: Text.
+    """
+
+    def __init__(self, cursor_position: int = 0, message: str = "") -> None:
+        super().__init__(message)
+        self.cursor_position = cursor_position
+        self.message = message
+
+    def __repr__(self) -> str:
+        return "{}(cursor_position={!r}, message={!r})".format(
+            self.__class__.__name__,
+            self.cursor_position,
+            self.message,
+        )
+
+
+class Validator(metaclass=ABCMeta):
+    """
+    Abstract base class for an input validator.
+
+    A validator is typically created in one of the following two ways:
+
+    - Either by overriding this class and implementing the `validate` method.
+    - Or by passing a callable to `Validator.from_callable`.
+
+    If the validation takes some time and needs to happen in a background
+    thread, this can be wrapped in a :class:`.ThreadedValidator`.
+    """
+
+    @abstractmethod
+    def validate(self, document: Document) -> None:
+        """
+        Validate the input.
+        If invalid, this should raise a :class:`.ValidationError`.
+
+        :param document: :class:`~prompt_toolkit.document.Document` instance.
+        """
+        pass
+
+    async def validate_async(self, document: Document) -> None:
+        """
+        Return a `Future` which is set when the validation is ready.
+        This function can be overloaded in order to provide an asynchronous
+        implementation.
+        """
+        try:
+            self.validate(document)
+        except ValidationError:
+            raise
+
+    @classmethod
+    def from_callable(
+        cls,
+        validate_func: Callable[[str], bool],
+        error_message: str = "Invalid input",
+        move_cursor_to_end: bool = False,
+    ) -> "Validator":
+        """
+        Create a validator from a simple validate callable. E.g.:
+
+        .. code:: python
+
+            def is_valid(text):
+                return text in ['hello', 'world']
+            Validator.from_callable(is_valid, error_message='Invalid input')
+
+        :param validate_func: Callable that takes the input string, and returns
+            `True` if the input is valid input.
+        :param error_message: Message to be displayed if the input is invalid.
+        :param move_cursor_to_end: Move the cursor to the end of the input, if
+            the input is invalid.
+        """
+        return _ValidatorFromCallable(validate_func, error_message, move_cursor_to_end)
+
+
+class _ValidatorFromCallable(Validator):
+    """
+    Validate input from a simple callable.
+    """
+
+    def __init__(
+        self, func: Callable[[str], bool], error_message: str, move_cursor_to_end: bool
+    ) -> None:
+
+        self.func = func
+        self.error_message = error_message
+        self.move_cursor_to_end = move_cursor_to_end
+
+    def __repr__(self) -> str:
+        return f"Validator.from_callable({self.func!r})"
+
+    def validate(self, document: Document) -> None:
+        if not self.func(document.text):
+            if self.move_cursor_to_end:
+                index = len(document.text)
+            else:
+                index = 0
+
+            raise ValidationError(cursor_position=index, message=self.error_message)
+
+
+class ThreadedValidator(Validator):
+    """
+    Wrapper that runs input validation in a thread.
+    (Use this to prevent the user interface from becoming unresponsive if the
+    input validation takes too much time.)
+    """
+
+    def __init__(self, validator: Validator) -> None:
+        self.validator = validator
+
+    def validate(self, document: Document) -> None:
+        self.validator.validate(document)
+
+    async def validate_async(self, document: Document) -> None:
+        """
+        Run the `validate` function in a thread.
+        """
+
+        def run_validation_thread() -> None:
+            return self.validate(document)
+
+        await run_in_executor_with_context(run_validation_thread)
+
+
+class DummyValidator(Validator):
+    """
+    Validator class that accepts any input.
+    """
+
+    def validate(self, document: Document) -> None:
+        pass  # Don't raise any exception.
+
+
+class ConditionalValidator(Validator):
+    """
+    Validator that can be switched on/off according to
+    a filter. (This wraps around another validator.)
+    """
+
+    def __init__(self, validator: Validator, filter: FilterOrBool) -> None:
+        self.validator = validator
+        self.filter = to_filter(filter)
+
+    def validate(self, document: Document) -> None:
+        # Call the validator only if the filter is active.
+        if self.filter():
+            self.validator.validate(document)
+
+
+class DynamicValidator(Validator):
+    """
+    Validator class that can dynamically returns any Validator.
+
+    :param get_validator: Callable that returns a :class:`.Validator` instance.
+    """
+
+    def __init__(self, get_validator: Callable[[], Optional[Validator]]) -> None:
+        self.get_validator = get_validator
+
+    def validate(self, document: Document) -> None:
+        validator = self.get_validator() or DummyValidator()
+        validator.validate(document)
+
+    async def validate_async(self, document: Document) -> None:
+        validator = self.get_validator() or DummyValidator()
+        await validator.validate_async(document)
diff --git a/src/prompt_toolkit/widgets/__init__.py b/src/prompt_toolkit/widgets/__init__.py
new file mode 100644
index 0000000..552d355
--- /dev/null
+++ b/src/prompt_toolkit/widgets/__init__.py
@@ -0,0 +1,60 @@
+"""
+Collection of reusable components for building full screen applications.
+These are higher level abstractions on top of the `prompt_toolkit.layout`
+module.
+
+Most of these widgets implement the ``__pt_container__`` method, which makes it
+possible to embed these in the layout like any other container.
+"""
+from .base import (
+    Box,
+    Button,
+    Checkbox,
+    CheckboxList,
+    Frame,
+    HorizontalLine,
+    Label,
+    ProgressBar,
+    RadioList,
+    Shadow,
+    TextArea,
+    VerticalLine,
+)
+from .dialogs import Dialog
+from .menus import MenuContainer, MenuItem
+from .toolbars import (
+    ArgToolbar,
+    CompletionsToolbar,
+    FormattedTextToolbar,
+    SearchToolbar,
+    SystemToolbar,
+    ValidationToolbar,
+)
+
+__all__ = [
+    # Base.
+    "TextArea",
+    "Label",
+    "Button",
+    "Frame",
+    "Shadow",
+    "Box",
+    "VerticalLine",
+    "HorizontalLine",
+    "CheckboxList",
+    "RadioList",
+    "Checkbox",
+    "ProgressBar",
+    # Toolbars.
+    "ArgToolbar",
+    "CompletionsToolbar",
+    "FormattedTextToolbar",
+    "SearchToolbar",
+    "SystemToolbar",
+    "ValidationToolbar",
+    # Dialogs.
+    "Dialog",
+    # Menus.
+    "MenuContainer",
+    "MenuItem",
+]
diff --git a/src/prompt_toolkit/widgets/base.py b/src/prompt_toolkit/widgets/base.py
new file mode 100644
index 0000000..38cbba0
--- /dev/null
+++ b/src/prompt_toolkit/widgets/base.py
@@ -0,0 +1,984 @@
+"""
+Collection of reusable components for building full screen applications.
+
+All of these widgets implement the ``__pt_container__`` method, which makes
+them usable in any situation where we are expecting a `prompt_toolkit`
+container object.
+
+.. warning::
+
+    At this point, the API for these widgets is considered unstable, and can
+    potentially change between minor releases (we try not too, but no
+    guarantees are made yet). The public API in
+    `prompt_toolkit.shortcuts.dialogs` on the other hand is considered stable.
+"""
+from functools import partial
+from typing import Callable, Generic, List, Optional, Sequence, Tuple, TypeVar, Union
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.auto_suggest import AutoSuggest, DynamicAutoSuggest
+from prompt_toolkit.buffer import Buffer, BufferAcceptHandler
+from prompt_toolkit.completion import Completer, DynamicCompleter
+from prompt_toolkit.document import Document
+from prompt_toolkit.filters import (
+    Condition,
+    FilterOrBool,
+    has_focus,
+    is_done,
+    is_true,
+    to_filter,
+)
+from prompt_toolkit.formatted_text import (
+    AnyFormattedText,
+    StyleAndTextTuples,
+    Template,
+    to_formatted_text,
+)
+from prompt_toolkit.formatted_text.utils import fragment_list_to_text
+from prompt_toolkit.history import History
+from prompt_toolkit.key_binding.key_bindings import KeyBindings
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.layout.containers import (
+    AnyContainer,
+    ConditionalContainer,
+    Container,
+    DynamicContainer,
+    Float,
+    FloatContainer,
+    HSplit,
+    VSplit,
+    Window,
+    WindowAlign,
+)
+from prompt_toolkit.layout.controls import (
+    BufferControl,
+    FormattedTextControl,
+    GetLinePrefixCallable,
+)
+from prompt_toolkit.layout.dimension import AnyDimension
+from prompt_toolkit.layout.dimension import Dimension as D
+from prompt_toolkit.layout.dimension import to_dimension
+from prompt_toolkit.layout.margins import (
+    ConditionalMargin,
+    NumberedMargin,
+    ScrollbarMargin,
+)
+from prompt_toolkit.layout.processors import (
+    AppendAutoSuggestion,
+    BeforeInput,
+    ConditionalProcessor,
+    PasswordProcessor,
+    Processor,
+)
+from prompt_toolkit.lexers import DynamicLexer, Lexer
+from prompt_toolkit.mouse_events import MouseEvent, MouseEventType
+from prompt_toolkit.utils import get_cwidth
+from prompt_toolkit.validation import DynamicValidator, Validator
+
+from .toolbars import SearchToolbar
+
+__all__ = [
+    "TextArea",
+    "Label",
+    "Button",
+    "Frame",
+    "Shadow",
+    "Box",
+    "VerticalLine",
+    "HorizontalLine",
+    "RadioList",
+    "CheckboxList",
+    "Checkbox",  # backward compatibility
+    "ProgressBar",
+]
+
+E = KeyPressEvent
+
+
+class Border:
+    "Box drawing characters. (Thin)"
+    HORIZONTAL = "\u2500"
+    VERTICAL = "\u2502"
+    TOP_LEFT = "\u250c"
+    TOP_RIGHT = "\u2510"
+    BOTTOM_LEFT = "\u2514"
+    BOTTOM_RIGHT = "\u2518"
+
+
+class TextArea:
+    """
+    A simple input field.
+
+    This is a higher level abstraction on top of several other classes with
+    sane defaults.
+
+    This widget does have the most common options, but it does not intend to
+    cover every single use case. For more configurations options, you can
+    always build a text area manually, using a
+    :class:`~prompt_toolkit.buffer.Buffer`,
+    :class:`~prompt_toolkit.layout.BufferControl` and
+    :class:`~prompt_toolkit.layout.Window`.
+
+    Buffer attributes:
+
+    :param text: The initial text.
+    :param multiline: If True, allow multiline input.
+    :param completer: :class:`~prompt_toolkit.completion.Completer` instance
+        for auto completion.
+    :param complete_while_typing: Boolean.
+    :param accept_handler: Called when `Enter` is pressed (This should be a
+        callable that takes a buffer as input).
+    :param history: :class:`~prompt_toolkit.history.History` instance.
+    :param auto_suggest: :class:`~prompt_toolkit.auto_suggest.AutoSuggest`
+        instance for input suggestions.
+
+    BufferControl attributes:
+
+    :param password: When `True`, display using asterisks.
+    :param focusable: When `True`, allow this widget to receive the focus.
+    :param focus_on_click: When `True`, focus after mouse click.
+    :param input_processors: `None` or a list of
+        :class:`~prompt_toolkit.layout.Processor` objects.
+    :param validator: `None` or a :class:`~prompt_toolkit.validation.Validator`
+        object.
+
+    Window attributes:
+
+    :param lexer: :class:`~prompt_toolkit.lexers.Lexer` instance for syntax
+        highlighting.
+    :param wrap_lines: When `True`, don't scroll horizontally, but wrap lines.
+    :param width: Window width. (:class:`~prompt_toolkit.layout.Dimension` object.)
+    :param height: Window height. (:class:`~prompt_toolkit.layout.Dimension` object.)
+    :param scrollbar: When `True`, display a scroll bar.
+    :param style: A style string.
+    :param dont_extend_width: When `True`, don't take up more width then the
+                              preferred width reported by the control.
+    :param dont_extend_height: When `True`, don't take up more width then the
+                               preferred height reported by the control.
+    :param get_line_prefix: None or a callable that returns formatted text to
+        be inserted before a line. It takes a line number (int) and a
+        wrap_count and returns formatted text. This can be used for
+        implementation of line continuations, things like Vim "breakindent" and
+        so on.
+
+    Other attributes:
+
+    :param search_field: An optional `SearchToolbar` object.
+    """
+
+    def __init__(
+        self,
+        text: str = "",
+        multiline: FilterOrBool = True,
+        password: FilterOrBool = False,
+        lexer: Optional[Lexer] = None,
+        auto_suggest: Optional[AutoSuggest] = None,
+        completer: Optional[Completer] = None,
+        complete_while_typing: FilterOrBool = True,
+        validator: Optional[Validator] = None,
+        accept_handler: Optional[BufferAcceptHandler] = None,
+        history: Optional[History] = None,
+        focusable: FilterOrBool = True,
+        focus_on_click: FilterOrBool = False,
+        wrap_lines: FilterOrBool = True,
+        read_only: FilterOrBool = False,
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        dont_extend_height: FilterOrBool = False,
+        dont_extend_width: FilterOrBool = False,
+        line_numbers: bool = False,
+        get_line_prefix: Optional[GetLinePrefixCallable] = None,
+        scrollbar: bool = False,
+        style: str = "",
+        search_field: Optional[SearchToolbar] = None,
+        preview_search: FilterOrBool = True,
+        prompt: AnyFormattedText = "",
+        input_processors: Optional[List[Processor]] = None,
+        name: str = "",
+    ) -> None:
+
+        if search_field is None:
+            search_control = None
+        elif isinstance(search_field, SearchToolbar):
+            search_control = search_field.control
+
+        if input_processors is None:
+            input_processors = []
+
+        # Writeable attributes.
+        self.completer = completer
+        self.complete_while_typing = complete_while_typing
+        self.lexer = lexer
+        self.auto_suggest = auto_suggest
+        self.read_only = read_only
+        self.wrap_lines = wrap_lines
+        self.validator = validator
+
+        self.buffer = Buffer(
+            document=Document(text, 0),
+            multiline=multiline,
+            read_only=Condition(lambda: is_true(self.read_only)),
+            completer=DynamicCompleter(lambda: self.completer),
+            complete_while_typing=Condition(
+                lambda: is_true(self.complete_while_typing)
+            ),
+            validator=DynamicValidator(lambda: self.validator),
+            auto_suggest=DynamicAutoSuggest(lambda: self.auto_suggest),
+            accept_handler=accept_handler,
+            history=history,
+            name=name,
+        )
+
+        self.control = BufferControl(
+            buffer=self.buffer,
+            lexer=DynamicLexer(lambda: self.lexer),
+            input_processors=[
+                ConditionalProcessor(
+                    AppendAutoSuggestion(), has_focus(self.buffer) & ~is_done
+                ),
+                ConditionalProcessor(
+                    processor=PasswordProcessor(), filter=to_filter(password)
+                ),
+                BeforeInput(prompt, style="class:text-area.prompt"),
+            ]
+            + input_processors,
+            search_buffer_control=search_control,
+            preview_search=preview_search,
+            focusable=focusable,
+            focus_on_click=focus_on_click,
+        )
+
+        if multiline:
+            if scrollbar:
+                right_margins = [ScrollbarMargin(display_arrows=True)]
+            else:
+                right_margins = []
+            if line_numbers:
+                left_margins = [NumberedMargin()]
+            else:
+                left_margins = []
+        else:
+            height = D.exact(1)
+            left_margins = []
+            right_margins = []
+
+        style = "class:text-area " + style
+
+        # If no height was given, guarantee height of at least 1.
+        if height is None:
+            height = D(min=1)
+
+        self.window = Window(
+            height=height,
+            width=width,
+            dont_extend_height=dont_extend_height,
+            dont_extend_width=dont_extend_width,
+            content=self.control,
+            style=style,
+            wrap_lines=Condition(lambda: is_true(self.wrap_lines)),
+            left_margins=left_margins,
+            right_margins=right_margins,
+            get_line_prefix=get_line_prefix,
+        )
+
+    @property
+    def text(self) -> str:
+        """
+        The `Buffer` text.
+        """
+        return self.buffer.text
+
+    @text.setter
+    def text(self, value: str) -> None:
+        self.document = Document(value, 0)
+
+    @property
+    def document(self) -> Document:
+        """
+        The `Buffer` document (text + cursor position).
+        """
+        return self.buffer.document
+
+    @document.setter
+    def document(self, value: Document) -> None:
+        self.buffer.set_document(value, bypass_readonly=True)
+
+    @property
+    def accept_handler(self) -> Optional[BufferAcceptHandler]:
+        """
+        The accept handler. Called when the user accepts the input.
+        """
+        return self.buffer.accept_handler
+
+    @accept_handler.setter
+    def accept_handler(self, value: BufferAcceptHandler) -> None:
+        self.buffer.accept_handler = value
+
+    def __pt_container__(self) -> Container:
+        return self.window
+
+
+class Label:
+    """
+    Widget that displays the given text. It is not editable or focusable.
+
+    :param text: Text to display. Can be multiline. All value types accepted by
+        :class:`prompt_toolkit.layout.FormattedTextControl` are allowed,
+        including a callable.
+    :param style: A style string.
+    :param width: When given, use this width, rather than calculating it from
+        the text size.
+    :param dont_extend_width: When `True`, don't take up more width than
+                              preferred, i.e. the length of the longest line of
+                              the text, or value of `width` parameter, if
+                              given. `True` by default
+    :param dont_extend_height: When `True`, don't take up more width than the
+                               preferred height, i.e. the number of lines of
+                               the text. `False` by default.
+    """
+
+    def __init__(
+        self,
+        text: AnyFormattedText,
+        style: str = "",
+        width: AnyDimension = None,
+        dont_extend_height: bool = True,
+        dont_extend_width: bool = False,
+        align: Union[WindowAlign, Callable[[], WindowAlign]] = WindowAlign.LEFT,
+        # There is no cursor navigation in a label, so it makes sense to always
+        # wrap lines by default.
+        wrap_lines: FilterOrBool = True,
+    ) -> None:
+
+        self.text = text
+
+        def get_width() -> AnyDimension:
+            if width is None:
+                text_fragments = to_formatted_text(self.text)
+                text = fragment_list_to_text(text_fragments)
+                if text:
+                    longest_line = max(get_cwidth(line) for line in text.splitlines())
+                else:
+                    return D(preferred=0)
+                return D(preferred=longest_line)
+            else:
+                return width
+
+        self.formatted_text_control = FormattedTextControl(text=lambda: self.text)
+
+        self.window = Window(
+            content=self.formatted_text_control,
+            width=get_width,
+            height=D(min=1),
+            style="class:label " + style,
+            dont_extend_height=dont_extend_height,
+            dont_extend_width=dont_extend_width,
+            align=align,
+            wrap_lines=wrap_lines,
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.window
+
+
+class Button:
+    """
+    Clickable button.
+
+    :param text: The caption for the button.
+    :param handler: `None` or callable. Called when the button is clicked. No
+        parameters are passed to this callable. Use for instance Python's
+        `functools.partial` to pass parameters to this callable if needed.
+    :param width: Width of the button.
+    """
+
+    def __init__(
+        self,
+        text: str,
+        handler: Optional[Callable[[], None]] = None,
+        width: int = 12,
+        left_symbol: str = "<",
+        right_symbol: str = ">",
+    ) -> None:
+
+        self.text = text
+        self.left_symbol = left_symbol
+        self.right_symbol = right_symbol
+        self.handler = handler
+        self.width = width
+        self.control = FormattedTextControl(
+            self._get_text_fragments,
+            key_bindings=self._get_key_bindings(),
+            focusable=True,
+        )
+
+        def get_style() -> str:
+            if get_app().layout.has_focus(self):
+                return "class:button.focused"
+            else:
+                return "class:button"
+
+        # Note: `dont_extend_width` is False, because we want to allow buttons
+        #       to take more space if the parent container provides more space.
+        #       Otherwise, we will also truncate the text.
+        #       Probably we need a better way here to adjust to width of the
+        #       button to the text.
+
+        self.window = Window(
+            self.control,
+            align=WindowAlign.CENTER,
+            height=1,
+            width=width,
+            style=get_style,
+            dont_extend_width=False,
+            dont_extend_height=True,
+        )
+
+    def _get_text_fragments(self) -> StyleAndTextTuples:
+        width = self.width - (
+            get_cwidth(self.left_symbol) + get_cwidth(self.right_symbol)
+        )
+        text = (f"{{:^{width}}}").format(self.text)
+
+        def handler(mouse_event: MouseEvent) -> None:
+            if (
+                self.handler is not None
+                and mouse_event.event_type == MouseEventType.MOUSE_UP
+            ):
+                self.handler()
+
+        return [
+            ("class:button.arrow", self.left_symbol, handler),
+            ("[SetCursorPosition]", ""),
+            ("class:button.text", text, handler),
+            ("class:button.arrow", self.right_symbol, handler),
+        ]
+
+    def _get_key_bindings(self) -> KeyBindings:
+        "Key bindings for the Button."
+        kb = KeyBindings()
+
+        @kb.add(" ")
+        @kb.add("enter")
+        def _(event: E) -> None:
+            if self.handler is not None:
+                self.handler()
+
+        return kb
+
+    def __pt_container__(self) -> Container:
+        return self.window
+
+
+class Frame:
+    """
+    Draw a border around any container, optionally with a title text.
+
+    Changing the title and body of the frame is possible at runtime by
+    assigning to the `body` and `title` attributes of this class.
+
+    :param body: Another container object.
+    :param title: Text to be displayed in the top of the frame (can be formatted text).
+    :param style: Style string to be applied to this widget.
+    """
+
+    def __init__(
+        self,
+        body: AnyContainer,
+        title: AnyFormattedText = "",
+        style: str = "",
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        key_bindings: Optional[KeyBindings] = None,
+        modal: bool = False,
+    ) -> None:
+
+        self.title = title
+        self.body = body
+
+        fill = partial(Window, style="class:frame.border")
+        style = "class:frame " + style
+
+        top_row_with_title = VSplit(
+            [
+                fill(width=1, height=1, char=Border.TOP_LEFT),
+                fill(char=Border.HORIZONTAL),
+                fill(width=1, height=1, char="|"),
+                # Notice: we use `Template` here, because `self.title` can be an
+                # `HTML` object for instance.
+                Label(
+                    lambda: Template(" {} ").format(self.title),
+                    style="class:frame.label",
+                    dont_extend_width=True,
+                ),
+                fill(width=1, height=1, char="|"),
+                fill(char=Border.HORIZONTAL),
+                fill(width=1, height=1, char=Border.TOP_RIGHT),
+            ],
+            height=1,
+        )
+
+        top_row_without_title = VSplit(
+            [
+                fill(width=1, height=1, char=Border.TOP_LEFT),
+                fill(char=Border.HORIZONTAL),
+                fill(width=1, height=1, char=Border.TOP_RIGHT),
+            ],
+            height=1,
+        )
+
+        @Condition
+        def has_title() -> bool:
+            return bool(self.title)
+
+        self.container = HSplit(
+            [
+                ConditionalContainer(content=top_row_with_title, filter=has_title),
+                ConditionalContainer(content=top_row_without_title, filter=~has_title),
+                VSplit(
+                    [
+                        fill(width=1, char=Border.VERTICAL),
+                        DynamicContainer(lambda: self.body),
+                        fill(width=1, char=Border.VERTICAL),
+                        # Padding is required to make sure that if the content is
+                        # too small, the right frame border is still aligned.
+                    ],
+                    padding=0,
+                ),
+                VSplit(
+                    [
+                        fill(width=1, height=1, char=Border.BOTTOM_LEFT),
+                        fill(char=Border.HORIZONTAL),
+                        fill(width=1, height=1, char=Border.BOTTOM_RIGHT),
+                    ],
+                    # specifying height here will increase the rendering speed.
+                    height=1,
+                ),
+            ],
+            width=width,
+            height=height,
+            style=style,
+            key_bindings=key_bindings,
+            modal=modal,
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+class Shadow:
+    """
+    Draw a shadow underneath/behind this container.
+    (This applies `class:shadow` the the cells under the shadow. The Style
+    should define the colors for the shadow.)
+
+    :param body: Another container object.
+    """
+
+    def __init__(self, body: AnyContainer) -> None:
+        self.container = FloatContainer(
+            content=body,
+            floats=[
+                Float(
+                    bottom=-1,
+                    height=1,
+                    left=1,
+                    right=-1,
+                    transparent=True,
+                    content=Window(style="class:shadow"),
+                ),
+                Float(
+                    bottom=-1,
+                    top=1,
+                    width=1,
+                    right=-1,
+                    transparent=True,
+                    content=Window(style="class:shadow"),
+                ),
+            ],
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+class Box:
+    """
+    Add padding around a container.
+
+    This also makes sure that the parent can provide more space than required by
+    the child. This is very useful when wrapping a small element with a fixed
+    size into a ``VSplit`` or ``HSplit`` object. The ``HSplit`` and ``VSplit``
+    try to make sure to adapt respectively the width and height, possibly
+    shrinking other elements. Wrapping something in a ``Box`` makes it flexible.
+
+    :param body: Another container object.
+    :param padding: The margin to be used around the body. This can be
+        overridden by `padding_left`, padding_right`, `padding_top` and
+        `padding_bottom`.
+    :param style: A style string.
+    :param char: Character to be used for filling the space around the body.
+        (This is supposed to be a character with a terminal width of 1.)
+    """
+
+    def __init__(
+        self,
+        body: AnyContainer,
+        padding: AnyDimension = None,
+        padding_left: AnyDimension = None,
+        padding_right: AnyDimension = None,
+        padding_top: AnyDimension = None,
+        padding_bottom: AnyDimension = None,
+        width: AnyDimension = None,
+        height: AnyDimension = None,
+        style: str = "",
+        char: Union[None, str, Callable[[], str]] = None,
+        modal: bool = False,
+        key_bindings: Optional[KeyBindings] = None,
+    ) -> None:
+
+        if padding is None:
+            padding = D(preferred=0)
+
+        def get(value: AnyDimension) -> D:
+            if value is None:
+                value = padding
+            return to_dimension(value)
+
+        self.padding_left = get(padding_left)
+        self.padding_right = get(padding_right)
+        self.padding_top = get(padding_top)
+        self.padding_bottom = get(padding_bottom)
+        self.body = body
+
+        self.container = HSplit(
+            [
+                Window(height=self.padding_top, char=char),
+                VSplit(
+                    [
+                        Window(width=self.padding_left, char=char),
+                        body,
+                        Window(width=self.padding_right, char=char),
+                    ]
+                ),
+                Window(height=self.padding_bottom, char=char),
+            ],
+            width=width,
+            height=height,
+            style=style,
+            modal=modal,
+            key_bindings=None,
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+_T = TypeVar("_T")
+
+
+class _DialogList(Generic[_T]):
+    """
+    Common code for `RadioList` and `CheckboxList`.
+    """
+
+    open_character: str = ""
+    close_character: str = ""
+    container_style: str = ""
+    default_style: str = ""
+    selected_style: str = ""
+    checked_style: str = ""
+    multiple_selection: bool = False
+    show_scrollbar: bool = True
+
+    def __init__(
+        self,
+        values: Sequence[Tuple[_T, AnyFormattedText]],
+        default_values: Optional[Sequence[_T]] = None,
+    ) -> None:
+        assert len(values) > 0
+        default_values = default_values or []
+
+        self.values = values
+        # current_values will be used in multiple_selection,
+        # current_value will be used otherwise.
+        keys: List[_T] = [value for (value, _) in values]
+        self.current_values: List[_T] = [
+            value for value in default_values if value in keys
+        ]
+        self.current_value: _T = (
+            default_values[0]
+            if len(default_values) and default_values[0] in keys
+            else values[0][0]
+        )
+
+        # Cursor index: take first selected item or first item otherwise.
+        if len(self.current_values) > 0:
+            self._selected_index = keys.index(self.current_values[0])
+        else:
+            self._selected_index = 0
+
+        # Key bindings.
+        kb = KeyBindings()
+
+        @kb.add("up")
+        def _up(event: E) -> None:
+            self._selected_index = max(0, self._selected_index - 1)
+
+        @kb.add("down")
+        def _down(event: E) -> None:
+            self._selected_index = min(len(self.values) - 1, self._selected_index + 1)
+
+        @kb.add("pageup")
+        def _pageup(event: E) -> None:
+            w = event.app.layout.current_window
+            if w.render_info:
+                self._selected_index = max(
+                    0, self._selected_index - len(w.render_info.displayed_lines)
+                )
+
+        @kb.add("pagedown")
+        def _pagedown(event: E) -> None:
+            w = event.app.layout.current_window
+            if w.render_info:
+                self._selected_index = min(
+                    len(self.values) - 1,
+                    self._selected_index + len(w.render_info.displayed_lines),
+                )
+
+        @kb.add("enter")
+        @kb.add(" ")
+        def _click(event: E) -> None:
+            self._handle_enter()
+
+        @kb.add(Keys.Any)
+        def _find(event: E) -> None:
+            # We first check values after the selected value, then all values.
+            values = list(self.values)
+            for value in values[self._selected_index + 1 :] + values:
+                text = fragment_list_to_text(to_formatted_text(value[1])).lower()
+
+                if text.startswith(event.data.lower()):
+                    self._selected_index = self.values.index(value)
+                    return
+
+        # Control and window.
+        self.control = FormattedTextControl(
+            self._get_text_fragments, key_bindings=kb, focusable=True
+        )
+
+        self.window = Window(
+            content=self.control,
+            style=self.container_style,
+            right_margins=[
+                ConditionalMargin(
+                    margin=ScrollbarMargin(display_arrows=True),
+                    filter=Condition(lambda: self.show_scrollbar),
+                ),
+            ],
+            dont_extend_height=True,
+        )
+
+    def _handle_enter(self) -> None:
+        if self.multiple_selection:
+            val = self.values[self._selected_index][0]
+            if val in self.current_values:
+                self.current_values.remove(val)
+            else:
+                self.current_values.append(val)
+        else:
+            self.current_value = self.values[self._selected_index][0]
+
+    def _get_text_fragments(self) -> StyleAndTextTuples:
+        def mouse_handler(mouse_event: MouseEvent) -> None:
+            """
+            Set `_selected_index` and `current_value` according to the y
+            position of the mouse click event.
+            """
+            if mouse_event.event_type == MouseEventType.MOUSE_UP:
+                self._selected_index = mouse_event.position.y
+                self._handle_enter()
+
+        result: StyleAndTextTuples = []
+        for i, value in enumerate(self.values):
+            if self.multiple_selection:
+                checked = value[0] in self.current_values
+            else:
+                checked = value[0] == self.current_value
+            selected = i == self._selected_index
+
+            style = ""
+            if checked:
+                style += " " + self.checked_style
+            if selected:
+                style += " " + self.selected_style
+
+            result.append((style, self.open_character))
+
+            if selected:
+                result.append(("[SetCursorPosition]", ""))
+
+            if checked:
+                result.append((style, "*"))
+            else:
+                result.append((style, " "))
+
+            result.append((style, self.close_character))
+            result.append((self.default_style, " "))
+            result.extend(to_formatted_text(value[1], style=self.default_style))
+            result.append(("", "\n"))
+
+        # Add mouse handler to all fragments.
+        for i in range(len(result)):
+            result[i] = (result[i][0], result[i][1], mouse_handler)
+
+        result.pop()  # Remove last newline.
+        return result
+
+    def __pt_container__(self) -> Container:
+        return self.window
+
+
+class RadioList(_DialogList[_T]):
+    """
+    List of radio buttons. Only one can be checked at the same time.
+
+    :param values: List of (value, label) tuples.
+    """
+
+    open_character = "("
+    close_character = ")"
+    container_style = "class:radio-list"
+    default_style = "class:radio"
+    selected_style = "class:radio-selected"
+    checked_style = "class:radio-checked"
+    multiple_selection = False
+
+    def __init__(
+        self,
+        values: Sequence[Tuple[_T, AnyFormattedText]],
+        default: Optional[_T] = None,
+    ) -> None:
+        if default is None:
+            default_values = None
+        else:
+            default_values = [default]
+
+        super().__init__(values, default_values=default_values)
+
+
+class CheckboxList(_DialogList[_T]):
+    """
+    List of checkbox buttons. Several can be checked at the same time.
+
+    :param values: List of (value, label) tuples.
+    """
+
+    open_character = "["
+    close_character = "]"
+    container_style = "class:checkbox-list"
+    default_style = "class:checkbox"
+    selected_style = "class:checkbox-selected"
+    checked_style = "class:checkbox-checked"
+    multiple_selection = True
+
+
+class Checkbox(CheckboxList[str]):
+    """Backward compatibility util: creates a 1-sized CheckboxList
+
+    :param text: the text
+    """
+
+    show_scrollbar = False
+
+    def __init__(self, text: AnyFormattedText = "", checked: bool = False) -> None:
+        values = [("value", text)]
+        super().__init__(values=values)
+        self.checked = checked
+
+    @property
+    def checked(self) -> bool:
+        return "value" in self.current_values
+
+    @checked.setter
+    def checked(self, value: bool) -> None:
+        if value:
+            self.current_values = ["value"]
+        else:
+            self.current_values = []
+
+
+class VerticalLine:
+    """
+    A simple vertical line with a width of 1.
+    """
+
+    def __init__(self) -> None:
+        self.window = Window(
+            char=Border.VERTICAL, style="class:line,vertical-line", width=1
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.window
+
+
+class HorizontalLine:
+    """
+    A simple horizontal line with a height of 1.
+    """
+
+    def __init__(self) -> None:
+        self.window = Window(
+            char=Border.HORIZONTAL, style="class:line,horizontal-line", height=1
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.window
+
+
+class ProgressBar:
+    def __init__(self) -> None:
+        self._percentage = 60
+
+        self.label = Label("60%")
+        self.container = FloatContainer(
+            content=Window(height=1),
+            floats=[
+                # We first draw the label, then the actual progress bar.  Right
+                # now, this is the only way to have the colors of the progress
+                # bar appear on top of the label. The problem is that our label
+                # can't be part of any `Window` below.
+                Float(content=self.label, top=0, bottom=0),
+                Float(
+                    left=0,
+                    top=0,
+                    right=0,
+                    bottom=0,
+                    content=VSplit(
+                        [
+                            Window(
+                                style="class:progress-bar.used",
+                                width=lambda: D(weight=int(self._percentage)),
+                            ),
+                            Window(
+                                style="class:progress-bar",
+                                width=lambda: D(weight=int(100 - self._percentage)),
+                            ),
+                        ]
+                    ),
+                ),
+            ],
+        )
+
+    @property
+    def percentage(self) -> int:
+        return self._percentage
+
+    @percentage.setter
+    def percentage(self, value: int) -> None:
+        self._percentage = value
+        self.label.text = f"{value}%"
+
+    def __pt_container__(self) -> Container:
+        return self.container
diff --git a/src/prompt_toolkit/widgets/dialogs.py b/src/prompt_toolkit/widgets/dialogs.py
new file mode 100644
index 0000000..920582b
--- /dev/null
+++ b/src/prompt_toolkit/widgets/dialogs.py
@@ -0,0 +1,106 @@
+"""
+Collection of reusable components for building full screen applications.
+"""
+from typing import Optional, Sequence, Union
+
+from prompt_toolkit.filters import has_completions, has_focus
+from prompt_toolkit.formatted_text import AnyFormattedText
+from prompt_toolkit.key_binding.bindings.focus import focus_next, focus_previous
+from prompt_toolkit.key_binding.key_bindings import KeyBindings
+from prompt_toolkit.layout.containers import (
+    AnyContainer,
+    DynamicContainer,
+    HSplit,
+    VSplit,
+)
+from prompt_toolkit.layout.dimension import AnyDimension
+from prompt_toolkit.layout.dimension import Dimension as D
+
+from .base import Box, Button, Frame, Shadow
+
+__all__ = [
+    "Dialog",
+]
+
+
+class Dialog:
+    """
+    Simple dialog window. This is the base for input dialogs, message dialogs
+    and confirmation dialogs.
+
+    Changing the title and body of the dialog is possible at runtime by
+    assigning to the `body` and `title` attributes of this class.
+
+    :param body: Child container object.
+    :param title: Text to be displayed in the heading of the dialog.
+    :param buttons: A list of `Button` widgets, displayed at the bottom.
+    """
+
+    def __init__(
+        self,
+        body: AnyContainer,
+        title: AnyFormattedText = "",
+        buttons: Optional[Sequence[Button]] = None,
+        modal: bool = True,
+        width: AnyDimension = None,
+        with_background: bool = False,
+    ) -> None:
+
+        self.body = body
+        self.title = title
+
+        buttons = buttons or []
+
+        # When a button is selected, handle left/right key bindings.
+        buttons_kb = KeyBindings()
+        if len(buttons) > 1:
+            first_selected = has_focus(buttons[0])
+            last_selected = has_focus(buttons[-1])
+
+            buttons_kb.add("left", filter=~first_selected)(focus_previous)
+            buttons_kb.add("right", filter=~last_selected)(focus_next)
+
+        frame_body: AnyContainer
+        if buttons:
+            frame_body = HSplit(
+                [
+                    # Add optional padding around the body.
+                    Box(
+                        body=DynamicContainer(lambda: self.body),
+                        padding=D(preferred=1, max=1),
+                        padding_bottom=0,
+                    ),
+                    # The buttons.
+                    Box(
+                        body=VSplit(buttons, padding=1, key_bindings=buttons_kb),
+                        height=D(min=1, max=3, preferred=3),
+                    ),
+                ]
+            )
+        else:
+            frame_body = body
+
+        # Key bindings for whole dialog.
+        kb = KeyBindings()
+        kb.add("tab", filter=~has_completions)(focus_next)
+        kb.add("s-tab", filter=~has_completions)(focus_previous)
+
+        frame = Shadow(
+            body=Frame(
+                title=lambda: self.title,
+                body=frame_body,
+                style="class:dialog.body",
+                width=(None if with_background is None else width),
+                key_bindings=kb,
+                modal=modal,
+            )
+        )
+
+        self.container: Union[Box, Shadow]
+        if with_background:
+            self.container = Box(body=frame, style="class:dialog", width=width)
+        else:
+            self.container = frame
+
+    def __pt_container__(self) -> AnyContainer:
+        return self.container
diff --git a/src/prompt_toolkit/widgets/menus.py b/src/prompt_toolkit/widgets/menus.py
new file mode 100644
index 0000000..6827ebe
--- /dev/null
+++ b/src/prompt_toolkit/widgets/menus.py
@@ -0,0 +1,374 @@
+from typing import Callable, Iterable, List, Optional, Sequence, Union
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.filters import Condition
+from prompt_toolkit.formatted_text.base import OneStyleAndTextTuple, StyleAndTextTuples
+from prompt_toolkit.key_binding.key_bindings import KeyBindings, KeyBindingsBase
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.layout.containers import (
+    AnyContainer,
+    ConditionalContainer,
+    Container,
+    Float,
+    FloatContainer,
+    HSplit,
+    Window,
+)
+from prompt_toolkit.layout.controls import FormattedTextControl
+from prompt_toolkit.mouse_events import MouseEvent, MouseEventType
+from prompt_toolkit.utils import get_cwidth
+from prompt_toolkit.widgets import Shadow
+
+from .base import Border
+
+__all__ = [
+    "MenuContainer",
+    "MenuItem",
+]
+
+E = KeyPressEvent
+
+
+class MenuContainer:
+    """
+    :param floats: List of extra Float objects to display.
+    :param menu_items: List of `MenuItem` objects.
+    """
+
+    def __init__(
+        self,
+        body: AnyContainer,
+        menu_items: List["MenuItem"],
+        floats: Optional[List[Float]] = None,
+        key_bindings: Optional[KeyBindingsBase] = None,
+    ) -> None:
+
+        self.body = body
+        self.menu_items = menu_items
+        self.selected_menu = [0]
+
+        # Key bindings.
+        kb = KeyBindings()
+
+        @Condition
+        def in_main_menu() -> bool:
+            return len(self.selected_menu) == 1
+
+        @Condition
+        def in_sub_menu() -> bool:
+            return len(self.selected_menu) > 1
+
+        # Navigation through the main menu.
+
+        @kb.add("left", filter=in_main_menu)
+        def _left(event: E) -> None:
+            self.selected_menu[0] = max(0, self.selected_menu[0] - 1)
+
+        @kb.add("right", filter=in_main_menu)
+        def _right(event: E) -> None:
+            self.selected_menu[0] = min(
+                len(self.menu_items) - 1, self.selected_menu[0] + 1
+            )
+
+        @kb.add("down", filter=in_main_menu)
+        def _down(event: E) -> None:
+            self.selected_menu.append(0)
+
+        @kb.add("c-c", filter=in_main_menu)
+        @kb.add("c-g", filter=in_main_menu)
+        def _cancel(event: E) -> None:
+            "Leave menu."
+            event.app.layout.focus_last()
+
+        # Sub menu navigation.
+
+        @kb.add("left", filter=in_sub_menu)
+        @kb.add("c-g", filter=in_sub_menu)
+        @kb.add("c-c", filter=in_sub_menu)
+        def _back(event: E) -> None:
+            "Go back to parent menu."
+            if len(self.selected_menu) > 1:
+                self.selected_menu.pop()
+
+        @kb.add("right", filter=in_sub_menu)
+        def _submenu(event: E) -> None:
+            "go into sub menu."
+            if self._get_menu(len(self.selected_menu) - 1).children:
+                self.selected_menu.append(0)
+
+            # If This item does not have a sub menu. Go up in the parent menu.
+            elif (
+                len(self.selected_menu) == 2
+                and self.selected_menu[0] < len(self.menu_items) - 1
+            ):
+                self.selected_menu = [
+                    min(len(self.menu_items) - 1, self.selected_menu[0] + 1)
+                ]
+                if self.menu_items[self.selected_menu[0]].children:
+                    self.selected_menu.append(0)
+
+        @kb.add("up", filter=in_sub_menu)
+        def _up_in_submenu(event: E) -> None:
+            "Select previous (enabled) menu item or return to main menu."
+            # Look for previous enabled items in this sub menu.
+            menu = self._get_menu(len(self.selected_menu) - 2)
+            index = self.selected_menu[-1]
+
+            previous_indexes = [
+                i
+                for i, item in enumerate(menu.children)
+                if i < index and not item.disabled
+            ]
+
+            if previous_indexes:
+                self.selected_menu[-1] = previous_indexes[-1]
+            elif len(self.selected_menu) == 2:
+                # Return to main menu.
+                self.selected_menu.pop()
+
+        @kb.add("down", filter=in_sub_menu)
+        def _down_in_submenu(event: E) -> None:
+            "Select next (enabled) menu item."
+            menu = self._get_menu(len(self.selected_menu) - 2)
+            index = self.selected_menu[-1]
+
+            next_indexes = [
+                i
+                for i, item in enumerate(menu.children)
+                if i > index and not item.disabled
+            ]
+
+            if next_indexes:
+                self.selected_menu[-1] = next_indexes[0]
+
+        @kb.add("enter")
+        def _click(event: E) -> None:
+            "Click the selected menu item."
+            item = self._get_menu(len(self.selected_menu) - 1)
+            if item.handler:
+                event.app.layout.focus_last()
+                item.handler()
+
+        # Controls.
+        self.control = FormattedTextControl(
+            self._get_menu_fragments, key_bindings=kb, focusable=True, show_cursor=False
+        )
+
+        self.window = Window(height=1, content=self.control, style="class:menu-bar")
+
+        submenu = self._submenu(0)
+        submenu2 = self._submenu(1)
+        submenu3 = self._submenu(2)
+
+        @Condition
+        def has_focus() -> bool:
+            return get_app().layout.current_window == self.window
+
+        self.container = FloatContainer(
+            content=HSplit(
+                [
+                    # The titlebar.
+                    self.window,
+                    # The 'body', like defined above.
+                    body,
+                ]
+            ),
+            floats=[
+                Float(
+                    xcursor=True,
+                    ycursor=True,
+                    content=ConditionalContainer(
+                        content=Shadow(body=submenu), filter=has_focus
+                    ),
+                ),
+                Float(
+                    attach_to_window=submenu,
+                    xcursor=True,
+                    ycursor=True,
+                    allow_cover_cursor=True,
+                    content=ConditionalContainer(
+                        content=Shadow(body=submenu2),
+                        filter=has_focus
+                        & Condition(lambda: len(self.selected_menu) >= 1),
+                    ),
+                ),
+                Float(
+                    attach_to_window=submenu2,
+                    xcursor=True,
+                    ycursor=True,
+                    allow_cover_cursor=True,
+                    content=ConditionalContainer(
+                        content=Shadow(body=submenu3),
+                        filter=has_focus
+                        & Condition(lambda: len(self.selected_menu) >= 2),
+                    ),
+                ),
+                # --
+            ]
+            + (floats or []),
+            key_bindings=key_bindings,
+        )
+
+    def _get_menu(self, level: int) -> "MenuItem":
+        menu = self.menu_items[self.selected_menu[0]]
+
+        for i, index in enumerate(self.selected_menu[1:]):
+            if i < level:
+                try:
+                    menu = menu.children[index]
+                except IndexError:
+                    return MenuItem("debug")
+
+        return menu
+
+    def _get_menu_fragments(self) -> StyleAndTextTuples:
+        focused = get_app().layout.has_focus(self.window)
+
+        # This is called during the rendering. When we discover that this
+        # widget doesn't have the focus anymore. Reset menu state.
+        if not focused:
+            self.selected_menu = [0]
+
+        # Generate text fragments for the main menu.
+        def one_item(i: int, item: MenuItem) -> Iterable[OneStyleAndTextTuple]:
+            def mouse_handler(mouse_event: MouseEvent) -> None:
+                hover = mouse_event.event_type == MouseEventType.MOUSE_MOVE
+                if (
+                    mouse_event.event_type == MouseEventType.MOUSE_DOWN
+                    or hover
+                    and focused
+                ):
+                    # Toggle focus.
+                    app = get_app()
+                    if not hover:
+                        if app.layout.has_focus(self.window):
+                            if self.selected_menu == [i]:
+                                app.layout.focus_last()
+                        else:
+                            app.layout.focus(self.window)
+                    self.selected_menu = [i]
+
+            yield ("class:menu-bar", " ", mouse_handler)
+            if i == self.selected_menu[0] and focused:
+                yield ("[SetMenuPosition]", "", mouse_handler)
+                style = "class:menu-bar.selected-item"
+            else:
+                style = "class:menu-bar"
+            yield style, item.text, mouse_handler
+
+        result: StyleAndTextTuples = []
+        for i, item in enumerate(self.menu_items):
+            result.extend(one_item(i, item))
+
+        return result
+
+    def _submenu(self, level: int = 0) -> Window:
+        def get_text_fragments() -> StyleAndTextTuples:
+            result: StyleAndTextTuples = []
+            if level < len(self.selected_menu):
+                menu = self._get_menu(level)
+                if menu.children:
+                    result.append(("class:menu", Border.TOP_LEFT))
+                    result.append(("class:menu", Border.HORIZONTAL * (menu.width + 4)))
+                    result.append(("class:menu", Border.TOP_RIGHT))
+                    result.append(("", "\n"))
+                    try:
+                        selected_item = self.selected_menu[level + 1]
+                    except IndexError:
+                        selected_item = -1
+
+                    def one_item(
+                        i: int, item: MenuItem
+                    ) -> Iterable[OneStyleAndTextTuple]:
+                        def mouse_handler(mouse_event: MouseEvent) -> None:
+                            if item.disabled:
+                                # The arrow keys can't interact with menu items that are disabled.
+                                # The mouse shouldn't be able to either.
+                                return
+                            hover = mouse_event.event_type == MouseEventType.MOUSE_MOVE
+                            if (
+                                mouse_event.event_type == MouseEventType.MOUSE_UP
+                                or hover
+                            ):
+                                app = get_app()
+                                if not hover and item.handler:
+                                    app.layout.focus_last()
+                                    item.handler()
+                                else:
+                                    self.selected_menu = self.selected_menu[
+                                        : level + 1
+                                    ] + [i]
+
+                        if i == selected_item:
+                            yield ("[SetCursorPosition]", "")
+                            style = "class:menu-bar.selected-item"
+                        else:
+                            style = ""
+
+                        yield ("class:menu", Border.VERTICAL)
+                        if item.text == "-":
+                            yield (
+                                style + "class:menu-border",
+                                f"{Border.HORIZONTAL * (menu.width + 3)}",
+                                mouse_handler,
+                            )
+                        else:
+                            yield (
+                                style,
+                                f" {item.text}".ljust(menu.width + 3),
+                                mouse_handler,
+                            )
+
+                        if item.children:
+                            yield (style, ">", mouse_handler)
+                        else:
+                            yield (style, " ", mouse_handler)
+
+                        if i == selected_item:
+                            yield ("[SetMenuPosition]", "")
+                        yield ("class:menu", Border.VERTICAL)
+
+                        yield ("", "\n")
+
+                    for i, item in enumerate(menu.children):
+                        result.extend(one_item(i, item))
+
+                    result.append(("class:menu", Border.BOTTOM_LEFT))
+                    result.append(("class:menu", Border.HORIZONTAL * (menu.width + 4)))
+                    result.append(("class:menu", Border.BOTTOM_RIGHT))
+            return result
+
+        return Window(FormattedTextControl(get_text_fragments), style="class:menu")
+
+    @property
+    def floats(self) -> Optional[List[Float]]:
+        return self.container.floats
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+class MenuItem:
+    def __init__(
+        self,
+        text: str = "",
+        handler: Optional[Callable[[], None]] = None,
+        children: Optional[List["MenuItem"]] = None,
+        shortcut: Optional[Sequence[Union[Keys, str]]] = None,
+        disabled: bool = False,
+    ) -> None:
+
+        self.text = text
+        self.handler = handler
+        self.children = children or []
+        self.shortcut = shortcut
+        self.disabled = disabled
+        self.selected_item = 0
+
+    @property
+    def width(self) -> int:
+        if self.children:
+            return max(get_cwidth(c.text) for c in self.children)
+        else:
+            return 0
diff --git a/src/prompt_toolkit/widgets/toolbars.py b/src/prompt_toolkit/widgets/toolbars.py
new file mode 100644
index 0000000..402ecaa
--- /dev/null
+++ b/src/prompt_toolkit/widgets/toolbars.py
@@ -0,0 +1,374 @@
+from typing import Any, Optional
+
+from prompt_toolkit.application.current import get_app
+from prompt_toolkit.buffer import Buffer
+from prompt_toolkit.enums import SYSTEM_BUFFER
+from prompt_toolkit.filters import (
+    Condition,
+    FilterOrBool,
+    emacs_mode,
+    has_arg,
+    has_completions,
+    has_focus,
+    has_validation_error,
+    to_filter,
+    vi_mode,
+    vi_navigation_mode,
+)
+from prompt_toolkit.formatted_text import (
+    AnyFormattedText,
+    StyleAndTextTuples,
+    fragment_list_len,
+    to_formatted_text,
+)
+from prompt_toolkit.key_binding.key_bindings import (
+    ConditionalKeyBindings,
+    KeyBindings,
+    KeyBindingsBase,
+    merge_key_bindings,
+)
+from prompt_toolkit.key_binding.key_processor import KeyPressEvent
+from prompt_toolkit.key_binding.vi_state import InputMode
+from prompt_toolkit.keys import Keys
+from prompt_toolkit.layout.containers import ConditionalContainer, Container, Window
+from prompt_toolkit.layout.controls import (
+    BufferControl,
+    FormattedTextControl,
+    SearchBufferControl,
+    UIContent,
+    UIControl,
+)
+from prompt_toolkit.layout.dimension import Dimension
+from prompt_toolkit.layout.processors import BeforeInput
+from prompt_toolkit.lexers import SimpleLexer
+from prompt_toolkit.search import SearchDirection
+
+__all__ = [
+    "ArgToolbar",
+    "CompletionsToolbar",
+    "FormattedTextToolbar",
+    "SearchToolbar",
+    "SystemToolbar",
+    "ValidationToolbar",
+]
+
+E = KeyPressEvent
+
+
+class FormattedTextToolbar(Window):
+    def __init__(self, text: AnyFormattedText, style: str = "", **kw: Any) -> None:
+        # Note: The style needs to be applied to the toolbar as a whole, not
+        #       just the `FormattedTextControl`.
+        super().__init__(
+            FormattedTextControl(text, **kw),
+            style=style,
+            dont_extend_height=True,
+            height=Dimension(min=1),
+        )
+
+
+class SystemToolbar:
+    """
+    Toolbar for a system prompt.
+
+    :param prompt: Prompt to be displayed to the user.
+    """
+
+    def __init__(
+        self,
+        prompt: AnyFormattedText = "Shell command: ",
+        enable_global_bindings: FilterOrBool = True,
+    ) -> None:
+
+        self.prompt = prompt
+        self.enable_global_bindings = to_filter(enable_global_bindings)
+
+        self.system_buffer = Buffer(name=SYSTEM_BUFFER)
+
+        self._bindings = self._build_key_bindings()
+
+        self.buffer_control = BufferControl(
+            buffer=self.system_buffer,
+            lexer=SimpleLexer(style="class:system-toolbar.text"),
+            input_processors=[
+                BeforeInput(lambda: self.prompt, style="class:system-toolbar")
+            ],
+            key_bindings=self._bindings,
+        )
+
+        self.window = Window(
+            self.buffer_control, height=1, style="class:system-toolbar"
+        )
+
+        self.container = ConditionalContainer(
+            content=self.window, filter=has_focus(self.system_buffer)
+        )
+
+    def _get_display_before_text(self) -> StyleAndTextTuples:
+        return [
+            ("class:system-toolbar", "Shell command: "),
+            ("class:system-toolbar.text", self.system_buffer.text),
+            ("", "\n"),
+        ]
+
+    def _build_key_bindings(self) -> KeyBindingsBase:
+        focused = has_focus(self.system_buffer)
+
+        # Emacs
+        emacs_bindings = KeyBindings()
+        handle = emacs_bindings.add
+
+        @handle("escape", filter=focused)
+        @handle("c-g", filter=focused)
+        @handle("c-c", filter=focused)
+        def _cancel(event: E) -> None:
+            "Hide system prompt."
+            self.system_buffer.reset()
+            event.app.layout.focus_last()
+
+        @handle("enter", filter=focused)
+        async def _accept(event: E) -> None:
+            "Run system command."
+            await event.app.run_system_command(
+                self.system_buffer.text,
+                display_before_text=self._get_display_before_text(),
+            )
+            self.system_buffer.reset(append_to_history=True)
+            event.app.layout.focus_last()
+
+        # Vi.
+        vi_bindings = KeyBindings()
+        handle = vi_bindings.add
+
+        @handle("escape", filter=focused)
+        @handle("c-c", filter=focused)
+        def _cancel_vi(event: E) -> None:
+            "Hide system prompt."
+            event.app.vi_state.input_mode = InputMode.NAVIGATION
+            self.system_buffer.reset()
+            event.app.layout.focus_last()
+
+        @handle("enter", filter=focused)
+        async def _accept_vi(event: E) -> None:
+            "Run system command."
+            event.app.vi_state.input_mode = InputMode.NAVIGATION
+            await event.app.run_system_command(
+                self.system_buffer.text,
+                display_before_text=self._get_display_before_text(),
+            )
+            self.system_buffer.reset(append_to_history=True)
+            event.app.layout.focus_last()
+
+        # Global bindings. (Listen to these bindings, even when this widget is
+        # not focussed.)
+        global_bindings = KeyBindings()
+        handle = global_bindings.add
+
+        @handle(Keys.Escape, "!", filter=~focused & emacs_mode, is_global=True)
+        def _focus_me(event: E) -> None:
+            "M-'!' will focus this user control."
+            event.app.layout.focus(self.window)
+
+        @handle("!", filter=~focused & vi_mode & vi_navigation_mode, is_global=True)
+        def _focus_me_vi(event: E) -> None:
+            "Focus."
+            event.app.vi_state.input_mode = InputMode.INSERT
+            event.app.layout.focus(self.window)
+
+        return merge_key_bindings(
+            [
+                ConditionalKeyBindings(emacs_bindings, emacs_mode),
+                ConditionalKeyBindings(vi_bindings, vi_mode),
+                ConditionalKeyBindings(global_bindings, self.enable_global_bindings),
+            ]
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+class ArgToolbar:
+    def __init__(self) -> None:
+        def get_formatted_text() -> StyleAndTextTuples:
+            arg = get_app().key_processor.arg or ""
+            if arg == "-":
+                arg = "-1"
+
+            return [
+                ("class:arg-toolbar", "Repeat: "),
+                ("class:arg-toolbar.text", arg),
+            ]
+
+        self.window = Window(FormattedTextControl(get_formatted_text), height=1)
+
+        self.container = ConditionalContainer(content=self.window, filter=has_arg)
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+class SearchToolbar:
+    """
+    :param vi_mode: Display '/' and '?' instead of I-search.
+    :param ignore_case: Search case insensitive.
+    """
+
+    def __init__(
+        self,
+        search_buffer: Optional[Buffer] = None,
+        vi_mode: bool = False,
+        text_if_not_searching: AnyFormattedText = "",
+        forward_search_prompt: AnyFormattedText = "I-search: ",
+        backward_search_prompt: AnyFormattedText = "I-search backward: ",
+        ignore_case: FilterOrBool = False,
+    ) -> None:
+
+        if search_buffer is None:
+            search_buffer = Buffer()
+
+        @Condition
+        def is_searching() -> bool:
+            return self.control in get_app().layout.search_links
+
+        def get_before_input() -> AnyFormattedText:
+            if not is_searching():
+                return text_if_not_searching
+            elif (
+                self.control.searcher_search_state.direction == SearchDirection.BACKWARD
+            ):
+                return "?" if vi_mode else backward_search_prompt
+            else:
+                return "/" if vi_mode else forward_search_prompt
+
+        self.search_buffer = search_buffer
+
+        self.control = SearchBufferControl(
+            buffer=search_buffer,
+            input_processors=[
+                BeforeInput(get_before_input, style="class:search-toolbar.prompt")
+            ],
+            lexer=SimpleLexer(style="class:search-toolbar.text"),
+            ignore_case=ignore_case,
+        )
+
+        self.container = ConditionalContainer(
+            content=Window(self.control, height=1, style="class:search-toolbar"),
+            filter=is_searching,
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+class _CompletionsToolbarControl(UIControl):
+    def create_content(self, width: int, height: int) -> UIContent:
+        all_fragments: StyleAndTextTuples = []
+
+        complete_state = get_app().current_buffer.complete_state
+        if complete_state:
+            completions = complete_state.completions
+            index = complete_state.complete_index  # Can be None!
+
+            # Width of the completions without the left/right arrows in the margins.
+            content_width = width - 6
+
+            # Booleans indicating whether we stripped from the left/right
+            cut_left = False
+            cut_right = False
+
+            # Create Menu content.
+            fragments: StyleAndTextTuples = []
+
+            for i, c in enumerate(completions):
+                # When there is no more place for the next completion
+                if fragment_list_len(fragments) + len(c.display_text) >= content_width:
+                    # If the current one was not yet displayed, page to the next sequence.
+                    if i <= (index or 0):
+                        fragments = []
+                        cut_left = True
+                    # If the current one is visible, stop here.
+                    else:
+                        cut_right = True
+                        break
+
+                fragments.extend(
+                    to_formatted_text(
+                        c.display_text,
+                        style=(
+                            "class:completion-toolbar.completion.current"
+                            if i == index
+                            else "class:completion-toolbar.completion"
+                        ),
+                    )
+                )
+                fragments.append(("", " "))
+
+            # Extend/strip until the content width.
+            fragments.append(("", " " * (content_width - fragment_list_len(fragments))))
+            fragments = fragments[:content_width]
+
+            # Return fragments
+            all_fragments.append(("", " "))
+            all_fragments.append(
+                ("class:completion-toolbar.arrow", "<" if cut_left else " ")
+            )
+            all_fragments.append(("", " "))
+
+            all_fragments.extend(fragments)
+
+            all_fragments.append(("", " "))
+            all_fragments.append(
+                ("class:completion-toolbar.arrow", ">" if cut_right else " ")
+            )
+            all_fragments.append(("", " "))
+
+        def get_line(i: int) -> StyleAndTextTuples:
+            return all_fragments
+
+        return UIContent(get_line=get_line, line_count=1)
+
+
+class CompletionsToolbar:
+    def __init__(self) -> None:
+        self.container = ConditionalContainer(
+            content=Window(
+                _CompletionsToolbarControl(), height=1, style="class:completion-toolbar"
+            ),
+            filter=has_completions,
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.container
+
+
+class ValidationToolbar:
+    def __init__(self, show_position: bool = False) -> None:
+        def get_formatted_text() -> StyleAndTextTuples:
+            buff = get_app().current_buffer
+
+            if buff.validation_error:
+                row, column = buff.document.translate_index_to_position(
+                    buff.validation_error.cursor_position
+                )
+
+                if show_position:
+                    text = "{} (line={} column={})".format(
+                        buff.validation_error.message,
+                        row + 1,
+                        column + 1,
+                    )
+                else:
+                    text = buff.validation_error.message
+
+                return [("class:validation-toolbar", text)]
+            else:
+                return []
+
+        self.control = FormattedTextControl(get_formatted_text)
+
+        self.container = ConditionalContainer(
+            content=Window(self.control, height=1), filter=has_validation_error
+        )
+
+    def __pt_container__(self) -> Container:
+        return self.container
diff --git a/src/prompt_toolkit/win32_types.py b/src/prompt_toolkit/win32_types.py
new file mode 100644
index 0000000..4ae2e39
--- /dev/null
+++ b/src/prompt_toolkit/win32_types.py
@@ -0,0 +1,227 @@
+from ctypes import Structure, Union, c_char, c_long, c_short, c_ulong
+from ctypes.wintypes import BOOL, DWORD, LPVOID, WCHAR, WORD
+from typing import TYPE_CHECKING
+
+# Input/Output standard device numbers. Note that these are not handle objects.
+# It's the `windll.kernel32.GetStdHandle` system call that turns them into a
+# real handle object.
+STD_INPUT_HANDLE = c_ulong(-10)
+STD_OUTPUT_HANDLE = c_ulong(-11)
+STD_ERROR_HANDLE = c_ulong(-12)
+
+
+class COORD(Structure):
+    """
+    Struct in wincon.h
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms682119(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        X: int
+        Y: int
+
+    _fields_ = [
+        ("X", c_short),  # Short
+        ("Y", c_short),  # Short
+    ]
+
+    def __repr__(self) -> str:
+        return "{}(X={!r}, Y={!r}, type_x={!r}, type_y={!r})".format(
+            self.__class__.__name__,
+            self.X,
+            self.Y,
+            type(self.X),
+            type(self.Y),
+        )
+
+
+class UNICODE_OR_ASCII(Union):
+    if TYPE_CHECKING:
+        AsciiChar: bytes
+        UnicodeChar: str
+
+    _fields_ = [
+        ("AsciiChar", c_char),
+        ("UnicodeChar", WCHAR),
+    ]
+
+
+class KEY_EVENT_RECORD(Structure):
+    """
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms684166(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        KeyDown: int
+        RepeatCount: int
+        VirtualKeyCode: int
+        VirtualScanCode: int
+        uChar: UNICODE_OR_ASCII
+        ControlKeyState: int
+
+    _fields_ = [
+        ("KeyDown", c_long),  # bool
+        ("RepeatCount", c_short),  # word
+        ("VirtualKeyCode", c_short),  # word
+        ("VirtualScanCode", c_short),  # word
+        ("uChar", UNICODE_OR_ASCII),  # Unicode or ASCII.
+        ("ControlKeyState", c_long),  # double word
+    ]
+
+
+class MOUSE_EVENT_RECORD(Structure):
+    """
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms684239(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        MousePosition: COORD
+        ButtonState: int
+        ControlKeyState: int
+        EventFlags: int
+
+    _fields_ = [
+        ("MousePosition", COORD),
+        ("ButtonState", c_long),  # dword
+        ("ControlKeyState", c_long),  # dword
+        ("EventFlags", c_long),  # dword
+    ]
+
+
+class WINDOW_BUFFER_SIZE_RECORD(Structure):
+    """
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms687093(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        Size: COORD
+
+    _fields_ = [("Size", COORD)]
+
+
+class MENU_EVENT_RECORD(Structure):
+    """
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms684213(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        CommandId: int
+
+    _fields_ = [("CommandId", c_long)]  # uint
+
+
+class FOCUS_EVENT_RECORD(Structure):
+    """
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms683149(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        SetFocus: int
+
+    _fields_ = [("SetFocus", c_long)]  # bool
+
+
+class EVENT_RECORD(Union):
+    if TYPE_CHECKING:
+        KeyEvent: KEY_EVENT_RECORD
+        MouseEvent: MOUSE_EVENT_RECORD
+        WindowBufferSizeEvent: WINDOW_BUFFER_SIZE_RECORD
+        MenuEvent: MENU_EVENT_RECORD
+        FocusEvent: FOCUS_EVENT_RECORD
+
+    _fields_ = [
+        ("KeyEvent", KEY_EVENT_RECORD),
+        ("MouseEvent", MOUSE_EVENT_RECORD),
+        ("WindowBufferSizeEvent", WINDOW_BUFFER_SIZE_RECORD),
+        ("MenuEvent", MENU_EVENT_RECORD),
+        ("FocusEvent", FOCUS_EVENT_RECORD),
+    ]
+
+
+class INPUT_RECORD(Structure):
+    """
+    http://msdn.microsoft.com/en-us/library/windows/desktop/ms683499(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        EventType: int
+        Event: EVENT_RECORD
+
+    _fields_ = [("EventType", c_short), ("Event", EVENT_RECORD)]  # word  # Union.
+
+
+EventTypes = {
+    1: "KeyEvent",
+    2: "MouseEvent",
+    4: "WindowBufferSizeEvent",
+    8: "MenuEvent",
+    16: "FocusEvent",
+}
+
+
+class SMALL_RECT(Structure):
+    """struct in wincon.h."""
+
+    if TYPE_CHECKING:
+        Left: int
+        Top: int
+        Right: int
+        Bottom: int
+
+    _fields_ = [
+        ("Left", c_short),
+        ("Top", c_short),
+        ("Right", c_short),
+        ("Bottom", c_short),
+    ]
+
+
+class CONSOLE_SCREEN_BUFFER_INFO(Structure):
+    """struct in wincon.h."""
+
+    if TYPE_CHECKING:
+        dwSize: COORD
+        dwCursorPosition: COORD
+        wAttributes: int
+        srWindow: SMALL_RECT
+        dwMaximumWindowSize: COORD
+
+    _fields_ = [
+        ("dwSize", COORD),
+        ("dwCursorPosition", COORD),
+        ("wAttributes", WORD),
+        ("srWindow", SMALL_RECT),
+        ("dwMaximumWindowSize", COORD),
+    ]
+
+    def __repr__(self) -> str:
+        return "CONSOLE_SCREEN_BUFFER_INFO({!r},{!r},{!r},{!r},{!r},{!r},{!r},{!r},{!r},{!r},{!r})".format(
+            self.dwSize.Y,
+            self.dwSize.X,
+            self.dwCursorPosition.Y,
+            self.dwCursorPosition.X,
+            self.wAttributes,
+            self.srWindow.Top,
+            self.srWindow.Left,
+            self.srWindow.Bottom,
+            self.srWindow.Right,
+            self.dwMaximumWindowSize.Y,
+            self.dwMaximumWindowSize.X,
+        )
+
+
+class SECURITY_ATTRIBUTES(Structure):
+    """
+    http://msdn.microsoft.com/en-us/library/windows/desktop/aa379560(v=vs.85).aspx
+    """
+
+    if TYPE_CHECKING:
+        nLength: int
+        lpSecurityDescriptor: int
+        bInheritHandle: int  # BOOL comes back as 'int'.
+
+    _fields_ = [
+        ("nLength", DWORD),
+        ("lpSecurityDescriptor", LPVOID),
+        ("bInheritHandle", BOOL),
+    ]