fix layout update

src/textual/app.py

@@ -365,6 +365,10 @@ async def on_event(self, event: events.Event) -> None:
         else:
             await super().on_event(event)
 
+    async def on_idle(self, event: events.Idle) -> None:
+        if self.view.check_layout():
+            await self.view.refresh_layout()
+
     async def action(
         self,
         action: str,

src/textual/layout.py

@@ -94,11 +94,15 @@ def reset_update(self) -> None:
 
     def reset(self) -> None:
         self._cuts = None
+        if self._require_update:
+            self.renders.clear()
+            self._layout_map.clear()
 
     def reflow(self, width: int, height: int) -> ReflowResult:
         self.reset()
 
         map = self.generate_map(width, height)
+        self._require_update = False
 
         # Filter out widgets that are off screen or zero area
         screen_region = Region(0, 0, width, height)

src/textual/view.py

@@ -66,6 +66,9 @@ def render(self) -> RenderableType:
     def get_offset(self, widget: Widget) -> Point:
         return self.layout.get_offset(widget)
 
+    def check_layout(self) -> bool:
+        return super().check_layout() or self.layout.check_update()
+
     async def message_update(self, message: UpdateMessage) -> None:
         widget = message.widget
         assert isinstance(widget, Widget)
@@ -142,7 +145,7 @@ async def watch_background(value: str) -> None:
     async def on_idle(self, event: events.Idle) -> None:
         if self.layout.check_update():
             self.layout.reset_update()
-            self.require_layout()
+            await self.refresh_layout()
 
     async def _on_mouse_move(self, event: events.MouseMove) -> None:
         try: