combine updates, cache arrangements

src/textual/_node_list.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 from typing import Iterator, overload, TYPE_CHECKING
-from weakref import ref
 
 import rich.repr
 
@@ -19,7 +18,10 @@ class NodeList:
     """
 
     def __init__(self) -> None:
+        # The nodes in the list
         self._nodes: list[DOMNode] = []
+        # Increments when list is updated (used for caching)
+        self._updates = 0
 
     def __bool__(self) -> bool:
         return bool(self._nodes)
@@ -39,9 +41,11 @@ class NodeList:
     def _append(self, widget: DOMNode) -> None:
         if widget not in self._nodes:
             self._nodes.append(widget)
+            self._updates += 1
 
     def _clear(self) -> None:
         del self._nodes[:]
+        self._updates += 1
 
     def __iter__(self) -> Iterator[DOMNode]:
         return iter(self._nodes)

src/textual/message_pump.py

@@ -274,7 +274,11 @@ class MessagePump:
                         for _cls, method in self._get_dispatch_methods(
                             "on_idle", event
                         ):
-                            await invoke(method, event)
+                            try:
+                                await invoke(method, event)
+                            except Exception as error:
+                                self.app.on_exception(error)
+                                break
 
         log("CLOSED", self)
 

src/textual/screen.py

@@ -13,6 +13,7 @@ from .geometry import Offset, Region, Size
 from ._compositor import Compositor, MapGeometry
 from .reactive import Reactive
 from .renderables.blank import Blank
+from ._timer import Timer
 from .widget import Widget
 
 if sys.version_info >= (3, 8):
@@ -41,11 +42,21 @@ class Screen(Widget):
         super().__init__(name=name, id=id)
         self._compositor = Compositor()
         self._dirty_widgets: set[Widget] = set()
+        self._update_timer: Timer | None = None
 
     @property
     def is_transparent(self) -> bool:
         return False
 
+    @property
+    def update_timer(self) -> Timer:
+        """Timer used to perform updates."""
+        if self._update_timer is None:
+            self._update_timer = self.set_interval(
+                UPDATE_PERIOD, self._on_update, name="screen_update", pause=True
+            )
+        return self._update_timer
+
     def watch_dark(self, dark: bool) -> None:
         pass
 
@@ -100,20 +111,24 @@ class Screen(Widget):
 
     def on_idle(self, event: events.Idle) -> None:
         # Check for any widgets marked as 'dirty' (needs a repaint)
-        if self._dirty_widgets:
-            self._update_timer.resume()
+        event.prevent_default()
+
         if self._layout_required:
             self._refresh_layout()
             self._layout_required = False
+            self._dirty_widgets.clear()
+        elif self._dirty_widgets:
+            self.update_timer.resume()
 
     def _on_update(self) -> None:
         """Called by the _update_timer."""
         # Render widgets together
+
         if self._dirty_widgets:
             self._compositor.update_widgets(self._dirty_widgets)
             self.app._display(self._compositor.render())
             self._dirty_widgets.clear()
-        self._update_timer.pause()
+        self.update_timer.pause()
 
     def _refresh_layout(self, size: Size | None = None, full: bool = False) -> None:
         """Refresh the layout (can change size and positions of widgets)."""
@@ -122,7 +137,7 @@ class Screen(Widget):
             return
 
         self._compositor.update_widgets(self._dirty_widgets)
-        self._update_timer.pause()
+        self.update_timer.pause()
         try:
             hidden, shown, resized = self._compositor.reflow(self, size)
 
@@ -153,7 +168,6 @@ class Screen(Widget):
         except Exception as error:
             self.app.on_exception(error)
             return
-
         display_update = self._compositor.render(full=full)
         if display_update is not None:
             self.app._display(display_update)
@@ -171,9 +185,8 @@ class Screen(Widget):
         self.check_idle()
 
     def on_mount(self, event: events.Mount) -> None:
-        self._update_timer = self.set_interval(
-            UPDATE_PERIOD, self._on_update, name="screen_update", pause=True
-        )
+        pass
+        # self._refresh_layout()
 
     def _screen_resized(self, size: Size):
         """Called by App when the screen is resized."""

src/textual/widget.py

@@ -104,7 +104,7 @@ class Widget(DOMNode):
         self._content_height_cache: tuple[object, int] = (None, 0)
 
         self._arrangement: ArrangeResult | None = None
-        self._arrangement_size: Size = Size()
+        self._arrangement_cache_key: tuple[int, Size] = (-1, Size())
 
         super().__init__(name=name, id=id, classes=classes)
         self.add_children(*children)
@@ -122,10 +122,14 @@ class Widget(DOMNode):
     show_horizontal_scrollbar = Reactive(False, layout=True)
 
     def _arrange(self, size: Size) -> ArrangeResult:
-        if self._arrangement is not None and size == self._arrangement_size:
+        arrange_cache_key = (self.children._updates, size)
+        if (
+            self._arrangement is not None
+            and arrange_cache_key == self._arrangement_cache_key
+        ):
             return self._arrangement
         self._arrangement = self.layout.arrange(self, size)
-        self._arrangement_size = size
+        self._arrangement_cache_key = (self.children._updates, size)
         return self._arrangement
 
     def watch_show_horizontal_scrollbar(self, value: bool) -> None:
@@ -855,10 +859,6 @@ class Widget(DOMNode):
         lines = self._render_cache.lines[start:end]
         return lines
 
-    def check_layout(self) -> bool:
-        """Check if a layout has been requested."""
-        return self._layout_required
-
     def get_style_at(self, x: int, y: int) -> Style:
         offset_x, offset_y = self.screen.get_offset(self)
         return self.screen.get_style_at(x + offset_x, y + offset_y)
@@ -917,12 +917,12 @@ class Widget(DOMNode):
             event (events.Idle): Idle event.
         """
 
-        if self.check_layout():
+        if self._layout_required:
             self._layout_required = False
             self.screen.post_message_no_wait(messages.Layout(self))
         elif self._repaint_required:
             self.emit_no_wait(messages.Update(self, self))
-        self._repaint_required = False
+            self._repaint_required = False
 
     def focus(self) -> None:
         """Give input focus to this widget."""