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" )