fix for scrollbar issue (#2086)

* fix for scrollbar issue

* pause between mouse messages

Author: willmcgugan

src/textual/pilot.py

@@ -94,7 +94,9 @@ async def click(
             target_widget, offset, button=1, shift=shift, meta=meta, control=control
         )
         app.post_message(MouseDown(**message_arguments))
+        await self.pause()
         app.post_message(MouseUp(**message_arguments))
+        await self.pause()
         app.post_message(Click(**message_arguments))
         await self.pause()
 

src/textual/widget.py

@@ -2436,12 +2436,12 @@ def _scroll_update(self, virtual_size: Size) -> None:
                 height - self.scrollbar_size_horizontal
             )
             if self.vertical_scrollbar._repaint_required:
-                self.call_next(self.vertical_scrollbar.refresh)
+                self.call_later(self.vertical_scrollbar.refresh)
         if self.show_horizontal_scrollbar:
             self.horizontal_scrollbar.window_virtual_size = virtual_size.width
             self.horizontal_scrollbar.window_size = width - self.scrollbar_size_vertical
             if self.horizontal_scrollbar._repaint_required:
-                self.call_next(self.horizontal_scrollbar.refresh)
+                self.call_later(self.horizontal_scrollbar.refresh)
 
         self.scroll_x = self.validate_scroll_x(self.scroll_x)
         self.scroll_y = self.validate_scroll_y(self.scroll_y)