Allow user to interupt scroll to end

Author: willmcgugan

src/textual/scroll_view.py

@@ -38,6 +38,8 @@ def watch_scroll_x(self, old_value: float, new_value: float) -> None:
             self.refresh()
 
     def watch_scroll_y(self, old_value: float, new_value: float) -> None:
+        if new_value >= self.max_scroll_y:
+            self._user_scroll_interrupt = False
         if self.show_vertical_scrollbar and (old_value) != (new_value):
             self.vertical_scrollbar.position = new_value
             self.refresh()

src/textual/scrollbar.py

@@ -356,6 +356,8 @@ async def _on_mouse_up(self, event: events.MouseUp) -> None:
         event.stop()
 
     def _on_mouse_capture(self, event: events.MouseCapture) -> None:
+        if isinstance(self._parent, Widget):
+            self._parent._user_scroll_interrupt = True
         self.grabbed = event.mouse_position
         self.grabbed_position = self.position
 

src/textual/widget.py

@@ -502,6 +502,8 @@ def __init__(
         """Used to cache :odd pseudoclass state."""
         self._last_scroll_time = monotonic()
         """Time of last scroll."""
+        self._user_scroll_interrupt: bool = False
+        """Has the user interrupted a scroll to end?"""
 
     @property
     def is_mounted(self) -> bool:
@@ -1698,6 +1700,8 @@ def watch_scroll_x(self, old_value: float, new_value: float) -> None:
             self._refresh_scroll()
 
     def watch_scroll_y(self, old_value: float, new_value: float) -> None:
+        if new_value >= self.max_scroll_y:
+            self._user_scroll_interrupt = True
         self.vertical_scrollbar.position = new_value
         if round(old_value) != round(new_value):
             self._refresh_scroll()
@@ -2688,9 +2692,20 @@ def scroll_end(
             y_axis: Allow scrolling on Y axis?
 
         """
+
+        if self._user_scroll_interrupt and not force:
+            # Do not scroll to end if a user action has interrupted scrolling
+            return
+
         if speed is None and duration is None:
             duration = 1.0
 
+        async def scroll_end_on_complete() -> None:
+            """It's possible new content was added before we reached the end."""
+            self.scroll_y = self.max_scroll_y
+            if on_complete is not None:
+                self.call_next(on_complete)
+
         # In most cases we'd call self.scroll_to and let it handle the call
         # to do things after a refresh, but here we need the refresh to
         # happen first so that we can get the new self.max_scroll_y (that
@@ -2707,7 +2722,7 @@ def _lazily_scroll_end() -> None:
                 duration=duration,
                 easing=easing,
                 force=force,
-                on_complete=on_complete,
+                on_complete=scroll_end_on_complete,
                 level=level,
             )
 
@@ -4450,13 +4465,15 @@ def _on_unmount(self) -> None:
     def action_scroll_home(self) -> None:
         if not self._allow_scroll:
             raise SkipAction()
+        self._user_scroll_interrupt = True
         self._clear_anchor()
         self.scroll_home(x_axis=self.scroll_y == 0)
 
     def action_scroll_end(self) -> None:
         if not self._allow_scroll:
             raise SkipAction()
         self._clear_anchor()
+        self._user_scroll_interrupt = False
         self.scroll_end(x_axis=self.scroll_y == self.is_vertical_scroll_end)
 
     def action_scroll_left(self) -> None:
@@ -4474,24 +4491,28 @@ def action_scroll_right(self) -> None:
     def action_scroll_up(self) -> None:
         if not self.allow_vertical_scroll:
             raise SkipAction()
+        self._user_scroll_interrupt = True
         self._clear_anchor()
         self.scroll_up()
 
     def action_scroll_down(self) -> None:
         if not self.allow_vertical_scroll:
             raise SkipAction()
+        self._user_scroll_interrupt = True
         self._clear_anchor()
         self.scroll_down()
 
     def action_page_down(self) -> None:
         if not self.allow_vertical_scroll:
             raise SkipAction()
+        self._user_scroll_interrupt = True
         self._clear_anchor()
         self.scroll_page_down()
 
     def action_page_up(self) -> None:
         if not self.allow_vertical_scroll:
             raise SkipAction()
+        self._user_scroll_interrupt = True
         self._clear_anchor()
         self.scroll_page_up()
 

src/textual/widgets/_log.py

@@ -191,11 +191,7 @@ def write(
             self._prune_max_lines()
 
         auto_scroll = self.auto_scroll if scroll_end is None else scroll_end
-        if (
-            auto_scroll
-            and not self.is_vertical_scrollbar_grabbed
-            and is_vertical_scroll_end
-        ):
+        if auto_scroll:
             self.scroll_end(animate=False, immediate=True, x_axis=False)
         return self
 

src/textual/widgets/_rich_log.py

@@ -279,11 +279,7 @@ def write(
         # the new line(s), and the height will definitely have changed.
         self.virtual_size = Size(self._widest_line_width, len(self.lines))
 
-        if (
-            auto_scroll
-            and not self.is_vertical_scrollbar_grabbed
-            and is_vertical_scroll_end
-        ):
+        if auto_scroll:
             self.scroll_end(animate=animate, immediate=False, x_axis=False)
 
         return self