perf: optimize render layout invalidation#85
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The optimization commit 2450c6d ('Optimize render layout invalidation') introduced relayout boundaries that skip cascading markNeedsLayout up to the parent when the parent doesn't use the child's size. RenderLayoutBuilder was passing 'parentUsesSize: !constraints.isTight' to its child, which evaluated to false under tight constraints and broke the propagation chain. When the chat toolbar's LayoutBuilder's container child marked itself dirty (e.g. from inner streaming widgets), the dirty mark never reached LayoutBuilder or its parent, so the toolbar's _layoutCallback never re-ran and children rendered with stale state. Fix: always pass 'parentUsesSize: true' because RenderLayoutBuilder ALWAYS derives its size from its child (size = constraints.constrain(child.size) at the bottom of performLayout). The previous code was a lie that the optimization was happily exploiting. Adds 17 tests in layout_invalidation_optimization_test.dart covering: - Relayout boundaries (parentUsesSize=false/true propagation) - RenderText.text setter optimization (same-footprint skip, size-changing relayout, _layoutResult updates, style-only) - markNeedsLayout propagation semantics - RenderLayoutBuilder child chain (incl. direct regression test that catches the bug — fails under old code, passes after fix) - Streaming widget repaint path (style-only, same-width, size-changing, multi-update cascade) All 1428 nocterm tests pass.
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Summary
RenderLayoutBuilderchild dirty marks always cascade when its child can affect layout.Tests
dart analyzedart test test/framework/layout_invalidation_optimization_test.dart test/framework/relayout_boundary_test.dart test/framework/render_object_invalidation_optimization_test.dart test/framework/render_pipeline_test.dart