prevent stuck scrollbar (#2003)

* prevent stuck scrollbar

* update changelog

* remove debug

* remove debug

CHANGELOG.md

@@ -34,7 +34,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Fixed bug that prevented pilot from pressing some keys https://github.com/Textualize/textual/issues/1815
 - DataTable race condition that caused crash https://github.com/Textualize/textual/pull/1962
-- Fixed scrollbar getting "stuck" to cursor when cursor leaves window during drag https://github.com/Textualize/textual/pull/1968
+- Fixed scrollbar getting "stuck" to cursor when cursor leaves window during drag https://github.com/Textualize/textual/pull/1968 https://github.com/Textualize/textual/pull/2003
 - DataTable crash when enter pressed when table is empty https://github.com/Textualize/textual/pull/1973
 
 ## [0.13.0] - 2023-03-02

src/textual/driver.py

@@ -27,8 +27,8 @@ class Driver(ABC):
         self._size = size
         self._loop = asyncio.get_running_loop()
         self._mouse_down_time = _clock.get_time_no_wait()
-        self._dragging = False
-        self._dragging_button = None
+        self._down_buttons: list[int] = []
+        self._last_move_event: events.MouseMove | None = None
 
     @property
     def is_headless(self) -> bool:
@@ -44,29 +44,37 @@ class Driver(ABC):
         """Performs some additional processing of events."""
         if isinstance(event, events.MouseDown):
             self._mouse_down_time = event.time
+            if event.button:
+                self._down_buttons.append(event.button)
+        elif isinstance(event, events.MouseUp):
+            if event.button:
+                self._down_buttons.remove(event.button)
         elif isinstance(event, events.MouseMove):
-            if event.button and not self._dragging:
-                self._dragging = True
-                self._dragging_button = event.button
-            elif self._dragging and self._dragging_button != event.button:
-                # Artificially generate a MouseUp event when we stop "dragging"
-                self.send_event(
-                    MouseUp(
-                        x=event.x,
-                        y=event.y,
-                        delta_x=event.delta_x,
-                        delta_y=event.delta_y,
-                        button=self._dragging_button,
-                        shift=event.shift,
-                        meta=event.meta,
-                        ctrl=event.ctrl,
-                        screen_x=event.screen_x,
-                        screen_y=event.screen_y,
-                        style=event.style,
+            if (
+                self._down_buttons
+                and not event.button
+                and self._last_move_event is not None
+            ):
+                buttons = list(dict.fromkeys(self._down_buttons).keys())
+                self._down_buttons.clear()
+                move_event = self._last_move_event
+                for button in buttons:
+                    self.send_event(
+                        MouseUp(
+                            x=move_event.x,
+                            y=move_event.y,
+                            delta_x=0,
+                            delta_y=0,
+                            button=button,
+                            shift=event.shift,
+                            meta=event.meta,
+                            ctrl=event.ctrl,
+                            screen_x=move_event.screen_x,
+                            screen_y=move_event.screen_y,
+                            style=event.style,
+                        )
                     )
-                )
-                self._dragging = False
-                self._dragging_button = None
+            self._last_move_event = event
 
         self.send_event(event)
 

src/textual/scrollbar.py

@@ -291,6 +291,7 @@ class ScrollBar(Widget):
     def _on_hide(self, event: events.Hide) -> None:
         if self.grabbed:
             self.release_mouse()
+            self.grabbed = None
 
     def _on_enter(self, event: events.Enter) -> None:
         self.mouse_over = True
@@ -299,10 +300,12 @@ class ScrollBar(Widget):
         self.mouse_over = False
 
     def action_scroll_down(self) -> None:
-        self.post_message(ScrollDown() if self.vertical else ScrollRight())
+        if not self.grabbed:
+            self.post_message(ScrollDown() if self.vertical else ScrollRight())
 
     def action_scroll_up(self) -> None:
-        self.post_message(ScrollUp() if self.vertical else ScrollLeft())
+        if not self.grabbed:
+            self.post_message(ScrollUp() if self.vertical else ScrollLeft())
 
     def action_grab(self) -> None:
         self.capture_mouse()
@@ -313,6 +316,7 @@ class ScrollBar(Widget):
     async def _on_mouse_up(self, event: events.MouseUp) -> None:
         if self.grabbed:
             self.release_mouse()
+            self.grabbed = None
         event.stop()
 
     def _on_mouse_capture(self, event: events.MouseCapture) -> None: