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diff --git a/src/prompt_toolkit/mouse_events.py b/src/prompt_toolkit/mouse_events.py
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+++ b/src/prompt_toolkit/mouse_events.py
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+"""
+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,
+        )