Screen processes mouse move events after forwarding them to the child widget.

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fixed a crash when a `SelectionList` had a prompt wider than itself https://github.com/Textualize/textual/issues/2900
 - Fixed a bug where `Click` events were bubbling up from `Switch` widgets https://github.com/Textualize/textual/issues/2366
 - Fixed a crash when using empty CSS variables https://github.com/Textualize/textual/issues/1849
+- `MouseMove` events bubble up from widgets. `App` and `Screen` receive `MouseMove` events even if there's no Widget under the cursor. https://github.com/Textualize/textual/issues/2905
 
 ## [0.30.0] - 2023-07-17
 

docs/events/mouse_move.md

@@ -2,7 +2,7 @@
 
 The `MouseMove` event is sent to a widget when the mouse pointer is moved over a widget.
 
-- [ ] Bubbles
+- [x] Bubbles
 - [x] Verbose
 
 ## Attributes

src/textual/events.py

@@ -435,10 +435,10 @@ class MouseEvent(InputEvent, bubble=True):
 
 
 @rich.repr.auto
-class MouseMove(MouseEvent, bubble=False, verbose=True):
+class MouseMove(MouseEvent, bubble=True, verbose=True):
     """Sent when the mouse cursor moves.
 
-    - [ ] Bubbles
+    - [X] Bubbles
     - [X] Verbose
     """
 

src/textual/screen.py

@@ -818,22 +818,13 @@ class Screen(Generic[ScreenResultType], Widget):
 
         else:
             self.app._set_mouse_over(widget)
-            mouse_event = events.MouseMove(
-                event.x - region.x,
-                event.y - region.y,
-                event.delta_x,
-                event.delta_y,
-                event.button,
-                event.shift,
-                event.meta,
-                event.ctrl,
-                screen_x=event.screen_x,
-                screen_y=event.screen_y,
-                style=event.style,
-            )
             widget.hover_style = event.style
-            mouse_event._set_forwarded()
-            widget._forward_event(mouse_event)
+            if widget is self:
+                self.post_message(event)
+            else:
+                mouse_event = self._translate_mouse_move_event(event, region)
+                mouse_event._set_forwarded()
+                widget._forward_event(mouse_event)
 
             if not self.app._disable_tooltips:
                 try:
@@ -856,6 +847,28 @@ class Screen(Generic[ScreenResultType], Widget):
                     else:
                         tooltip.display = False
 
+    @staticmethod
+    def _translate_mouse_move_event(
+        event: events.MouseMove, region: Region
+    ) -> events.MouseMove:
+        """
+        Returns a mouse move event whose relative coordinates are translated to
+        the origin of the specified region.
+        """
+        return events.MouseMove(
+            event.x - region.x,
+            event.y - region.y,
+            event.delta_x,
+            event.delta_y,
+            event.button,
+            event.shift,
+            event.meta,
+            event.ctrl,
+            screen_x=event.screen_x,
+            screen_y=event.screen_y,
+            style=event.style,
+        )
+
     def _forward_event(self, event: events.Event) -> None:
         if event.is_forwarded:
             return

tests/test_screens.py

@@ -4,7 +4,9 @@ import threading
 
 import pytest
 
-from textual.app import App, ScreenStackError
+from textual.app import App, ScreenStackError, ComposeResult
+from textual.events import MouseMove
+from textual.geometry import Offset
 from textual.screen import Screen
 from textual.widgets import Button, Input, Label
 
@@ -350,3 +352,59 @@ async def test_switch_screen_updates_results_callback_stack():
         app.switch_screen("b")
         assert len(app.screen._result_callbacks) == 1
         assert app.screen._result_callbacks[-1].callback is None
+
+
+async def test_screen_receives_mouse_move_events():
+    class MouseMoveRecordingScreen(Screen):
+        mouse_events = []
+
+        def on_mouse_move(self, event: MouseMove) -> None:
+            MouseMoveRecordingScreen.mouse_events.append(event)
+
+    class SimpleApp(App[None]):
+        SCREENS = {"a": MouseMoveRecordingScreen()}
+
+        def on_mount(self):
+            self.push_screen("a")
+
+    mouse_offset = Offset(1, 1)
+
+    async with SimpleApp().run_test() as pilot:
+        await pilot.hover(None, mouse_offset)
+
+    assert len(MouseMoveRecordingScreen.mouse_events) == 1
+    mouse_event = MouseMoveRecordingScreen.mouse_events[0]
+    assert mouse_event.x, mouse_event.y == mouse_offset
+
+
+async def test_mouse_move_event_bubbles_to_screen_from_widget():
+    class MouseMoveRecordingScreen(Screen):
+        mouse_events = []
+
+        DEFAULT_CSS = """
+        Label {
+            offset: 10 10;
+        }
+        """
+
+        def compose(self) -> ComposeResult:
+            yield Label("Any label")
+
+        def on_mouse_move(self, event: MouseMove) -> None:
+            MouseMoveRecordingScreen.mouse_events.append(event)
+
+    class SimpleApp(App[None]):
+        SCREENS = {"a": MouseMoveRecordingScreen()}
+
+        def on_mount(self):
+            self.push_screen("a")
+
+    label_offset = Offset(10, 10)
+    mouse_offset = Offset(1, 1)
+
+    async with SimpleApp().run_test() as pilot:
+        await pilot.hover(Label, mouse_offset)
+
+    assert len(MouseMoveRecordingScreen.mouse_events) == 1
+    mouse_event = MouseMoveRecordingScreen.mouse_events[0]
+    assert mouse_event.x, mouse_event.y == (label_offset.x + mouse_offset.x, label_offset.y + mouse_offset.y)