fix missing new widgets

CHANGELOG.md

@@ -15,6 +15,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Tree will no longer scroll the X axis when moving the cursor https://github.com/Textualize/textual/pull/5047
 
+### Fixed
+
+- Fixed widgets occasionally not getting Resize events https://github.com/Textualize/textual/pull/5048
+
 ## [0.80.1] - 2024-09-24
 
 ### Fixed

src/textual/_compositor.py

@@ -309,6 +309,9 @@ def __init__(self) -> None:
  # Mapping of line numbers on to lists of widget and regions
  self._layers_visible: list[list[tuple[Widget, Region, Region]]] | None = None
 
+ # New widgets added between updates
+ self._new_widgets: set[Widget] = set()
+
  def clear(self) -> None:
  """Remove all references to widgets (used when the screen closes)."""
  self._full_map.clear()
@@ -387,7 +390,9 @@ def reflow(self, parent: Widget, size: Size) -> ReflowResult:
  new_widgets = map.keys()
 
  # Newly visible widgets
- shown_widgets = new_widgets - old_widgets
+ shown_widgets = (new_widgets - old_widgets) | self._new_widgets
+ self._new_widgets.clear()
+
  # Newly hidden widgets
  hidden_widgets = self.widgets - widgets
 
@@ -419,7 +424,6 @@ def reflow(self, parent: Widget, size: Size) -> ReflowResult:
  for widget, (region, *_) in changes
  if (widget in common_widgets and old_map[widget].region[2:] != region[2:])
  }
-
  return ReflowResult(
  hidden=hidden_widgets,
  shown=shown_widgets,
@@ -483,6 +487,8 @@ def full_map(self) -> CompositorMap:
  if self._full_map_invalidated:
  self._full_map_invalidated = False
  map, _widgets = self._arrange_root(self.root, self.size, visible_only=False)
+ # Update any widgets which became visible in the interim
+ self._new_widgets.update(map.keys() - self._full_map.keys())
  self._full_map = map
  self._visible_widgets = None
  self._visible_map = None

tests/snapshot_tests/test_snapshots.py

@@ -9,7 +9,7 @@
 from textual import events
 from textual.app import App, ComposeResult
 from textual.binding import Binding
-from textual.containers import Vertical
+from textual.containers import Vertical, VerticalScroll
 from textual.pilot import Pilot
 from textual.screen import Screen
 from textual.widgets import (
@@ -24,8 +24,7 @@
  OptionList,
  SelectionList,
 )
-from textual.widgets import Switch
-from textual.widgets import Label
+from textual.widgets import ProgressBar, Label, Switch
 from textual.widgets.text_area import BUILTIN_LANGUAGES, Selection, TextAreaTheme
 
 # These paths should be relative to THIS directory.
@@ -1992,3 +1991,31 @@ def on_mount(self) -> None:
 
  app = DisabledApp()
  assert snap_compare(app)
+
+
+def test_missing_new_widgets(snap_compare):
+ """Regression test for https://github.com/Textualize/textual/issues/5024"""
+
+ class MRE(App):
+ BINDINGS = [("z", "toggle_console", "Console")]
+ CSS = """
+ RichLog { border-top: dashed blue; height: 6; }
+ .hidden { display: none; }
+ """
+
+ def compose(self):
+ yield VerticalScroll()
+ yield ProgressBar(
+ classes="hidden"
+ ) # removing or displaying this widget prevents the bug
+ yield Footer() # clicking "Console" in the footer prevents the bug
+ yield RichLog(classes="hidden")
+
+ def on_ready(self) -> None:
+ self.query_one(RichLog).write("\n".join(f"line #{i}" for i in range(5)))
+
+ def action_toggle_console(self) -> None:
+ self.query_one(RichLog).toggle_class("hidden")
+
+ app = MRE()
+ assert snap_compare(app, press=["space", "space", "z"])