call later

CHANGELOG.md

@@ -10,6 +10,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 - Watchers are now called immediately when setting the attribute if they are synchronous. https://github.com/Textualize/textual/pull/1145
+- Widget.call_later has been renamed to Widget.call_after_refresh.
+
+### Added
+
+- Added Widget.call_later which invokes a callback on idle.
 
 ## [0.4.0] - 2022-11-08
 

docs/examples/guide/input/binding01.py

@@ -23,7 +23,7 @@ class BindingApp(App):
         bar = Bar(color)
         bar.styles.background = Color.parse(color).with_alpha(0.5)
         self.mount(bar)
-        self.call_later(self.screen.scroll_end, animate=False)
+        self.call_after_refresh(self.screen.scroll_end, animate=False)
 
 
 if __name__ == "__main__":

src/textual/app.py

@@ -1606,19 +1606,28 @@ class App(Generic[ReturnType], DOMNode):
             screen (Screen): Screen instance
             renderable (RenderableType): A Rich renderable.
         """
-        if screen is not self.screen or renderable is None:
-            return
-        if self._running and not self._closed and not self.is_headless:
-            console = self.console
-            self._begin_update()
-            try:
+
+        try:
+            if screen is not self.screen or renderable is None:
+                return
+
+            if self._running and not self._closed and not self.is_headless:
+                console = self.console
+                self._begin_update()
                 try:
-                    console.print(renderable)
-                except Exception as error:
-                    self._handle_exception(error)
-            finally:
-                self._end_update()
-            console.file.flush()
+                    try:
+                        print(renderable)
+                        console.print(renderable)
+                    except Exception as error:
+                        self._handle_exception(error)
+                finally:
+                    self._end_update()
+                console.file.flush()
+        finally:
+            self.post_display_hook()
+
+    def post_display_hook(self) -> None:
+        """Called immediately after a display is done. Used in tests."""
 
     def get_widget_at(self, x: int, y: int) -> tuple[Widget, Region]:
         """Get the widget under the given coordinates.

src/textual/cli/previews/colors.py

@@ -71,7 +71,7 @@ class ColorsApp(App):
         yield Footer()
 
     def on_mount(self) -> None:
-        self.call_later(self.update_view)
+        self.call_after_refresh(self.update_view)
 
     def update_view(self) -> None:
         content = self.query_one("Content", Content)

src/textual/message_pump.py

@@ -251,7 +251,7 @@ class MessagePump(metaclass=MessagePumpMeta):
         self._timers.add(timer)
         return timer
 
-    def call_later(self, callback: Callable, *args, **kwargs) -> None:
+    def call_after_refresh(self, callback: Callable, *args, **kwargs) -> None:
         """Schedule a callback to run after all messages are processed and the screen
         has been refreshed. Positional and keyword arguments are passed to the callable.
 
@@ -263,6 +263,16 @@ class MessagePump(metaclass=MessagePumpMeta):
         message = messages.InvokeLater(self, partial(callback, *args, **kwargs))
         self.post_message_no_wait(message)
 
+    def call_later(self, callback: Callable, *args, **kwargs) -> None:
+        """Schedule a callback to run after all messages are processed in this object.
+        Positional and keywords arguments are passed to the callable.
+
+        Args:
+            callback (Callable): Callable to call next.
+        """
+        message = events.Callback(self, callback=partial(callback, *args, **kwargs))
+        self.post_message_no_wait(message)
+
     def _on_invoke_later(self, message: messages.InvokeLater) -> None:
         # Forward InvokeLater message to the Screen
         self.app.screen._invoke_later(message.callback)

src/textual/screen.py

@@ -333,11 +333,11 @@ class Screen(Widget):
             self._compositor.update_widgets(self._dirty_widgets)
             self.app._display(self, self._compositor.render())
             self._dirty_widgets.clear()
-
-        self.update_timer.pause()
         if self._callbacks:
             self.post_message_no_wait(events.InvokeCallbacks(self))
 
+        self.update_timer.pause()
+
     async def _on_invoke_callbacks(self, event: events.InvokeCallbacks) -> None:
         """Handle PostScreenUpdate events, which are sent after the screen is updated"""
         await self._invoke_and_clear_callbacks()
@@ -346,6 +346,8 @@ class Screen(Widget):
         """If there are scheduled callbacks to run, call them and clear
         the callback queue."""
         if self._callbacks:
+            display_update = self._compositor.render(full=True)
+            self.app._display(self, display_update)
             callbacks = self._callbacks[:]
             self._callbacks.clear()
             for callback in callbacks:
@@ -402,8 +404,7 @@ class Screen(Widget):
             self.app._handle_exception(error)
             return
         display_update = self._compositor.render(full=full)
-        if display_update is not None:
-            self.app._display(self, display_update)
+        self.app._display(self, display_update)
 
     async def _on_update(self, message: messages.Update) -> None:
         message.stop()

src/textual/widget.py

@@ -1576,7 +1576,7 @@ class Widget(DOMNode):
         """
         parent = self.parent
         if isinstance(parent, Widget):
-            self.call_later(
+            self.call_after_refresh(
                 parent.scroll_to_widget,
                 self,
                 animate=animate,
@@ -1989,7 +1989,7 @@ class Widget(DOMNode):
             except NoScreen:
                 pass
 
-        self.app.call_later(set_focus, self)
+        self.app.call_after_refresh(set_focus, self)
 
     def reset_focus(self) -> None:
         """Reset the focus (move it to the next available widget)."""

src/textual/widgets/_directory_tree.py

@@ -92,7 +92,7 @@ class DirectoryTree(TreeControl[DirEntry]):
         self.render_tree_label.cache_clear()
 
     def on_mount(self) -> None:
-        self.call_later(self.load_directory, self.root)
+        self.call_after_refresh(self.load_directory, self.root)
 
     async def load_directory(self, node: TreeNode[DirEntry]):
         path = node.data.path

tests/test_call_later.py

@@ -0,0 +1,41 @@
+import asyncio
+from textual.app import App
+
+
+class CallLaterApp(App[None]):
+    def __init__(self) -> None:
+        self.display_count = 0
+        super().__init__()
+
+    def post_display_hook(self) -> None:
+        self.display_count += 1
+
+
+async def test_call_later() -> None:
+    """Check that call later makes a call."""
+    app = CallLaterApp()
+    called_event = asyncio.Event()
+
+    async with app.run_test():
+        app.call_later(called_event.set)
+        await asyncio.wait_for(called_event.wait(), 1)
+
+
+async def test_call_after_refresh() -> None:
+    """Check that call later makes a call after a refresh."""
+    app = CallLaterApp()
+
+    display_count = -1
+
+    called_event = asyncio.Event()
+
+    def callback() -> None:
+        nonlocal display_count
+        called_event.set()
+        display_count = app.display_count
+
+    async with app.run_test():
+        app.call_after_refresh(callback)
+        await asyncio.wait_for(called_event.wait(), 1)
+        app_display_count = app.display_count
+        assert app_display_count > display_count