[yay]

Add UiBuilder::no_sizing_pass() so a child can use normal layout inside a sizing parent while retaining its actual ancestry and inherited UI properties. This is useful for clipped contents whose size does not determine their container’s allocation.

Default inheritance remains unchanged. The override does not cancel pass discarding or change visibility, enabled state, or input handling.

Compatibility: the public UiBuilder::sizing_pass field changes from bool to Option<bool> (None inherits). Existing callers that assign the field directly need to use Some(...) or the builder methods.

Example: simplifying a fixed-viewport content UI

The override replaces a separate root and reconstructed ancestor chain with a normal child:

-let mut builder = UiBuilder::new()
+let builder = UiBuilder::new()
     .scope_id(id)
     .max_rect(viewport)
     .layer_id(layer)
     .layout(layout)
-    .style(parent.style().clone())
-    .accessibility_parent(parent.unique_id());
-
-if !parent.is_enabled() {
-    builder = builder.disabled();
-}
-
-let mut content = if parent.is_sizing_pass() {
-    let ancestors: Vec<_> = parent.stack().iter().collect();
-    let mut proxy: Option<Ui> = None;
-    for (index, ancestor) in ancestors.into_iter().rev().enumerate() {
-        let mut ancestor_builder = UiBuilder::new()
-            .ui_stack_info(ancestor.info.clone())
-            .max_rect(ancestor.max_rect)
-            .layer_id(layer);
-        ancestor_builder.classes = ancestor.classes.clone();
-        let ancestor_id = id.with(("sizing-ancestor", index));
-        proxy = Some(if let Some(parent) = &mut proxy {
-            parent.new_child(ancestor_builder.scope_id(ancestor_id))
-        } else {
-            Ui::new(parent.ctx().clone(), ancestor_id, ancestor_builder)
-        });
-    }
-    proxy.unwrap().new_child(builder)
-} else {
-    parent.new_child(builder)
-};
+    .no_sizing_pass();
+
+let mut content = parent.new_child(builder);

The actual parent chain also keeps ui.close() and ui.close_kind() working without copying container metadata.

Tests cover inheritance and override precedence, widget layout, live ancestry and closing, inherited properties, and unchanged discard/input behavior.

Closes #8760.

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[github-actions]

Preview available at https://egui-pr-preview.github.io/pr/8762-codexno-sizing-pass
Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.

View snapshot changes at kitdiff