fix for events not sent on scroll

src/textual/_compositor.py

@@ -320,7 +320,7 @@ class Compositor:
         old_map = self.map
         map, widgets = self._arrange_root(parent, size, visible_only=True)
 
-        exposed_widgets = widgets - self.widgets
+        exposed_widgets = map.keys() - old_map.keys()
         # Replace map and widgets
         self.map = map
         self.widgets = widgets
@@ -394,6 +394,7 @@ class Compositor:
 
         map: CompositorMap = {}
         widgets: set[Widget] = set()
+        add_new_widget = widgets.add
         layer_order: int = 0
 
         def add_widget(
@@ -419,7 +420,7 @@ class Compositor:
                 visible = visibility == "visible"
 
             if visible:
-                widgets.add(widget)
+                add_new_widget(widget)
             styles_offset = widget.styles.offset
             layout_offset = (
                 styles_offset.resolve(region.size, clip.size)

src/textual/screen.py

@@ -9,6 +9,7 @@ from rich.style import Style
 from . import errors, events, messages
 from ._callback import invoke
 from ._compositor import Compositor, MapGeometry
+from ._profile import timer
 from ._types import CallbackType
 from .css.match import match
 from .css.parse import parse_selectors
@@ -434,18 +435,26 @@ class Screen(Widget):
                 exposed_widgets = self._compositor.reflow_visible(self, size)
                 if exposed_widgets:
                     layers = self._compositor.layers
-                    for widget, (
-                        region,
-                        _order,
-                        _clip,
-                        virtual_size,
-                        container_size,
-                        _,
-                    ) in layers:
-                        widget._size_updated(region.size, virtual_size, container_size)
-                        widget.post_message_no_wait(
-                            ResizeEvent(self, region.size, virtual_size, container_size)
-                        )
+                    with timer("size events"):
+                        for widget, (
+                            region,
+                            _order,
+                            _clip,
+                            virtual_size,
+                            container_size,
+                            _,
+                        ) in layers:
+                            if widget in exposed_widgets:
+                                widget._size_updated(
+                                    region.size,
+                                    virtual_size,
+                                    container_size,
+                                )
+                                widget.post_message_no_wait(
+                                    ResizeEvent(
+                                        self, region.size, virtual_size, container_size
+                                    )
+                                )
             else:
                 hidden, shown, resized = self._compositor.reflow(self, size)
                 Hide = events.Hide

src/textual/widget.py

@@ -2142,6 +2142,7 @@ class Widget(DOMNode):
             size: Screen size.
             virtual_size: Virtual (scrollable) size.
             container_size: Container size (size of parent).
+            refresh: Also refresh.
         """
         if (
             self._size != size
@@ -2149,11 +2150,13 @@ class Widget(DOMNode):
             or self._container_size != container_size
         ):
             self._size = size
-            self.virtual_size = virtual_size
+            if self.virtual_size:
+                self.virtual_size = virtual_size
+            else:
+                self._reactive_virtual_size = virtual_size
             self._container_size = container_size
             if self.is_scrollable:
                 self._scroll_update(virtual_size)
-            self.refresh()
 
     def _scroll_update(self, virtual_size: Size) -> None:
         """Update scrollbars visibility and dimensions.
@@ -2291,8 +2294,7 @@ class Widget(DOMNode):
             repaint: Repaint the widget (will call render() again). Defaults to True.
             layout: Also layout widgets in the view. Defaults to False.
         """
-
-        if layout:
+        if layout and not self._layout_required:
             self._layout_required = True
             for ancestor in self.ancestors:
                 if not isinstance(ancestor, Widget):

src/textual/widgets/_placeholder.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from itertools import cycle
 
+from rich.console import RenderableType
 from typing_extensions import Literal
 
 from .. import events
@@ -61,10 +62,10 @@ class Placeholder(Widget):
         overflow: hidden;
         color: $text;
     }
-
     Placeholder.-text {
         padding: 1;
     }
+
     """
 
     # Consecutive placeholders get assigned consecutive colors.
@@ -73,7 +74,7 @@ class Placeholder(Widget):
 
     variant: Reactive[PlaceholderVariant] = reactive("default")
 
-    _renderables: dict[PlaceholderVariant, RenderResult]
+    _renderables: dict[PlaceholderVariant, str]
 
     @classmethod
     def reset_color_cycle(cls) -> None:
@@ -119,7 +120,7 @@ class Placeholder(Widget):
         while next(self._variants_cycle) != self.variant:
             pass
 
-    def render(self) -> RenderResult:
+    def render(self) -> RenderableType:
         return self._renderables[self.variant]
 
     def cycle_variant(self) -> None:
@@ -147,6 +148,6 @@ class Placeholder(Widget):
 
     def on_resize(self, event: events.Resize) -> None:
         """Update the placeholder "size" variant with the new placeholder size."""
-        self._renderables["size"] = self._SIZE_RENDER_TEMPLATE.format(*self.size)
+        self._renderables["size"] = self._SIZE_RENDER_TEMPLATE.format(*event.size)
         if self.variant == "size":
-            self.refresh(layout=True)
+            self.refresh(layout=False)