Move the scrollbar check/post into the widget base class

src/textual/screen.py

@@ -762,26 +762,6 @@ def _refresh_layout(
         self._update_timer.pause()
         ResizeEvent = events.Resize
 
-        def _message_visibility(
-            widget: Widget, event: events.Show | events.Hide
-        ) -> None:
-            """Send a Show or Hide event to the given widget.
-
-            Args:
-                widget: The widget to send the event to.
-                event: The event to be sent.
-
-            Note:
-                This function ensures that any scrollbars attached to the
-                widget also get the messages; these are needed to help
-                update the grabbed status.
-            """
-            widget.post_message(event)
-            if widget.show_vertical_scrollbar:
-                widget.vertical_scrollbar.post_message(event)
-            if widget.show_horizontal_scrollbar:
-                widget.horizontal_scrollbar.post_message(event)
-
         try:
             if scroll:
                 exposed_widgets = self._compositor.reflow_visible(self, size)
@@ -812,7 +792,7 @@ def _message_visibility(
                 Show = events.Show
 
                 for widget in hidden:
-                    _message_visibility(widget, Hide())
+                    widget.post_message(Hide())
 
                 # We want to send a resize event to widgets that were just added or change since last layout
                 send_resize = shown | resized
@@ -834,7 +814,7 @@ def _message_visibility(
                         )
 
                 for widget in shown:
-                    _message_visibility(widget, Show())
+                    widget.post_message(Show())
 
         except Exception as error:
             self.app._handle_exception(error)

src/textual/widget.py

@@ -3706,7 +3706,17 @@ def _on_scroll_right(self, event: ScrollRight) -> None:
             self.scroll_page_right()
             event.stop()
 
+    def _on_show(self, event: events.Show) -> None:
+        if self.show_horizontal_scrollbar:
+            self.horizontal_scrollbar.post_message(event)
+        if self.show_vertical_scrollbar:
+            self.vertical_scrollbar.post_message(event)
+
     def _on_hide(self, event: events.Hide) -> None:
+        if self.show_horizontal_scrollbar:
+            self.horizontal_scrollbar.post_message(event)
+        if self.show_vertical_scrollbar:
+            self.vertical_scrollbar.post_message(event)
         if self.has_focus:
             self.blur()