fix stuck screen

src/textual/_callback.py

@@ -1,9 +1,17 @@
 from __future__ import annotations
 
+import asyncio
 from functools import lru_cache
-
 from inspect import signature, isawaitable
-from typing import Any, Callable
+from typing import Any, Callable, TYPE_CHECKING
+
+from . import active_app
+
+if TYPE_CHECKING:
+    from .app import App
+
+# Maximum seconds before warning about a slow callback
+INVOKE_TIMEOUT_WARNING = 3
 
 
 @lru_cache(maxsize=2048)
@@ -12,7 +20,7 @@ def count_parameters(func: Callable) -> int:
     return len(signature(func).parameters)
 
 
-async def invoke(callback: Callable, *params: object) -> Any:
+async def _invoke(callback: Callable, *params: object) -> Any:
     """Invoke a callback with an arbitrary number of parameters.
 
     Args:
@@ -27,3 +35,38 @@ async def invoke(callback: Callable, *params: object) -> Any:
     if isawaitable(result):
         result = await result
     return result
+
+
+async def invoke(callback: Callable, *params: object) -> Any:
+    """Invoke a callback with an arbitrary number of parameters.
+
+    Args:
+        callback: The callable to be invoked.
+
+    Returns:
+        The return value of the invoked callable.
+    """
+
+    app: App | None
+    try:
+        app = active_app.get()
+    except LookupError:
+        app = None
+
+    if app is not None and "debug" in app.features:
+        # In debug mode we will warn about callbacks that may be stuck
+        def log_slow() -> None:
+            """Log a message regarding a slow callback."""
+            app.log.warning(
+                f"Callback {callback} is still pending after {INVOKE_TIMEOUT_WARNING} seconds"
+            )
+
+        call_later_handle = asyncio.get_running_loop().call_later(
+            INVOKE_TIMEOUT_WARNING, log_slow
+        )
+        try:
+            return await _invoke(callback, *params)
+        finally:
+            call_later_handle.cancel()
+    else:
+        return await _invoke(callback, *params)

src/textual/app.py

@@ -1191,9 +1191,13 @@ class App(Generic[ReturnType], DOMNode):
         _screen = self.get_screen(screen)
         if not _screen.is_running:
             widgets = self._register(self, _screen)
-            return (_screen, AwaitMount(_screen, widgets))
+            await_mount = AwaitMount(_screen, widgets)
+            self.call_next(await_mount)
+            return (_screen, await_mount)
         else:
-            return (_screen, AwaitMount(_screen, []))
+            await_mount = AwaitMount(_screen, [])
+            self.call_next(await_mount)
+            return (_screen, await_mount)
 
     def _replace_screen(self, screen: Screen) -> Screen:
         """Handle the replaced screen.
@@ -2013,6 +2017,12 @@ class App(Generic[ReturnType], DOMNode):
         await self._close_messages()
 
     async def _on_resize(self, event: events.Resize) -> None:
+        # print(self.screen, self._screen_stack)
+        # print(self.screen.size)
+        # print(self.screen.is_running)
+        # print((self.screen._message_queue))
+        # print(self.screen._active_message)
+        # print(self.screen._task)
         event.stop()
         await self.screen.post_message(event)
 

src/textual/message_pump.py

@@ -64,6 +64,7 @@ class MessagePumpMeta(type):
 class MessagePump(metaclass=MessagePumpMeta):
     def __init__(self, parent: MessagePump | None = None) -> None:
         self._message_queue: Queue[Message | None] = Queue()
+        self._active_nessage: Message | None = None
         self._parent = parent
         self._running: bool = False
         self._closing: bool = False
@@ -75,6 +76,7 @@ class MessagePump(metaclass=MessagePumpMeta):
         self._last_idle: float = time()
         self._max_idle: float | None = None
         self._mounted_event = asyncio.Event()
+        self._next_callbacks: list[CallbackType] = []
 
     @property
     def task(self) -> Task:
@@ -271,10 +273,22 @@ class MessagePump(metaclass=MessagePumpMeta):
 
         Args:
             callback: Callable to call next.
+            *args: Positional arguments to pass to the callable.
+            **kwargs: Keyword arguments to pass to the callable.
         """
         message = events.Callback(self, callback=partial(callback, *args, **kwargs))
         self.post_message_no_wait(message)
 
+    def call_next(self, callback: Callable, *args, **kwargs) -> None:
+        """Schedule a callback to run immediately after processing the current message.
+
+        Args:
+            callback: Callable to run after current event.
+            *args: Positional arguments to pass to the callable.
+            **kwargs: Keyword arguments to pass to the callable.
+        """
+        self._next_callbacks.append(partial(callback, *args, **kwargs))
+
     def _on_invoke_later(self, message: messages.InvokeLater) -> None:
         # Forward InvokeLater message to the Screen
         self.app.screen._invoke_later(message.callback)
@@ -367,35 +381,52 @@ class MessagePump(metaclass=MessagePumpMeta):
                 except MessagePumpClosed:
                     break
 
+            self._active_message = message
+
             try:
-                await self._dispatch_message(message)
-            except CancelledError:
-                raise
+                try:
+                    await self._dispatch_message(message)
+                except CancelledError:
+                    raise
+                except Exception as error:
+                    self._mounted_event.set()
+                    self.app._handle_exception(error)
+                    break
+                finally:
+
+                    self._message_queue.task_done()
+
+                    current_time = time()
+
+                    # Insert idle events
+                    if self._message_queue.empty() or (
+                        self._max_idle is not None
+                        and current_time - self._last_idle > self._max_idle
+                    ):
+                        self._last_idle = current_time
+                        if not self._closed:
+                            event = events.Idle(self)
+                            for _cls, method in self._get_dispatch_methods(
+                                "on_idle", event
+                            ):
+                                try:
+                                    await invoke(method, event)
+                                except Exception as error:
+                                    self.app._handle_exception(error)
+                                    break
+            finally:
+                self._active_message = None
+
+    async def _flush_next_callbacks(self) -> None:
+        """Invoke pending callbacks in next callbacks queue."""
+        callbacks = self._next_callbacks.copy()
+        self._next_callbacks.clear()
+        for callback in callbacks:
+            try:
+                await invoke(callback)
             except Exception as error:
-                self._mounted_event.set()
                 self.app._handle_exception(error)
                 break
-            finally:
-
-                self._message_queue.task_done()
-                current_time = time()
-
-                # Insert idle events
-                if self._message_queue.empty() or (
-                    self._max_idle is not None
-                    and current_time - self._last_idle > self._max_idle
-                ):
-                    self._last_idle = current_time
-                    if not self._closed:
-                        event = events.Idle(self)
-                        for _cls, method in self._get_dispatch_methods(
-                            "on_idle", event
-                        ):
-                            try:
-                                await invoke(method, event)
-                            except Exception as error:
-                                self.app._handle_exception(error)
-                                break
 
     async def _dispatch_message(self, message: Message) -> None:
         """Dispatch a message received from the message queue.
@@ -412,6 +443,7 @@ class MessagePump(metaclass=MessagePumpMeta):
             await self.on_event(message)
         else:
             await self._on_message(message)
+        await self._flush_next_callbacks()
 
     def _get_dispatch_methods(
         self, method_name: str, message: Message

src/textual/screen.py

@@ -367,19 +367,20 @@ class Screen(Widget):
         # Check for any widgets marked as 'dirty' (needs a repaint)
         event.prevent_default()
 
-        async with self.app._dom_lock:
-            if self.is_current:
-                if self._layout_required:
-                    self._refresh_layout()
-                    self._layout_required = False
-                    self._dirty_widgets.clear()
-                if self._repaint_required:
-                    self._dirty_widgets.clear()
-                    self._dirty_widgets.add(self)
-                    self._repaint_required = False
+        if self.is_current:
+            async with self.app._dom_lock:
+                if self.is_current:
+                    if self._layout_required:
+                        self._refresh_layout()
+                        self._layout_required = False
+                        self._dirty_widgets.clear()
+                    if self._repaint_required:
+                        self._dirty_widgets.clear()
+                        self._dirty_widgets.add(self)
+                        self._repaint_required = False
 
-                if self._dirty_widgets:
-                    self.update_timer.resume()
+                    if self._dirty_widgets:
+                        self.update_timer.resume()
 
         # The Screen is idle - a good opportunity to invoke the scheduled callbacks
         await self._invoke_and_clear_callbacks()
@@ -423,6 +424,7 @@ class Screen(Widget):
 
     def _refresh_layout(self, size: Size | None = None, full: bool = False) -> None:
         """Refresh the layout (can change size and positions of widgets)."""
+        print("Screen._refresh_layout", size, full)
         size = self.outer_size if size is None else size
         if not size:
             return

src/textual/widget.py

@@ -91,6 +91,9 @@ class AwaitMount:
         self._parent = parent
         self._widgets = widgets
 
+    async def __call__(self) -> None:
+        await self
+
     def __await__(self) -> Generator[None, None, None]:
         async def await_mount() -> None:
             if self._widgets:
@@ -606,7 +609,9 @@ class Widget(DOMNode):
             parent, *widgets, before=insert_before, after=insert_after
         )
 
-        return AwaitMount(self, mounted)
+        await_mount = AwaitMount(self, mounted)
+        self.call_next(await_mount)
+        return await_mount
 
     def move_child(
         self,

src/textual/widgets/_footer.py

@@ -55,6 +55,7 @@ class Footer(Widget):
     async def watch_highlight_key(self, value) -> None:
         """If highlight key changes we need to regenerate the text."""
         self._key_text = None
+        self.refresh()
 
     def on_mount(self) -> None:
         watch(self.screen, "focused", self._focus_changed)