Call mark* methods before attaching child (#25239)

packages/flutter/lib/src/rendering/object.dart

@@ -1138,10 +1138,10 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(_debugCanPerformMutations);
     assert(child != null);
     setupParentData(child);
-    super.adoptChild(child);
     markNeedsLayout();
     markNeedsCompositingBitsUpdate();
     markNeedsSemanticsUpdate();
+    super.adoptChild(child);
   }
 
   /// Called by subclasses when they decide a render object is no longer a child.
@@ -1830,6 +1830,9 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   bool _needsCompositingBitsUpdate = false; // set to true when a child is added
   /// Mark the compositing state for this render object as dirty.
   ///
+  /// This is called to indicate that the value for [needsCompositing] needs to
+  /// be recomputed during the next [flushCompositingBits] engine phase.
+  ///
   /// When the subtree is mutated, we need to recompute our
   /// [needsCompositing] bit, and some of our ancestors need to do the
   /// same (in case ours changed in a way that will change theirs). To
@@ -1867,6 +1870,9 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   bool _needsCompositing; // initialised in the constructor
   /// Whether we or one of our descendants has a compositing layer.
   ///
+  /// If this node needs compositing as indicated by this bit, then all ancestor
+  /// nodes will also need compositing.
+  ///
   /// Only legal to call after [PipelineOwner.flushLayout] and
   /// [PipelineOwner.flushCompositingBits] have been called.
   bool get needsCompositing {

packages/flutter/test/rendering/repaint_boundary_test.dart

@@ -34,4 +34,21 @@ void main() {
     c.opacity = 0.7;
     pumpFrame(phase: EnginePhase.flushSemantics);
   });
+
+  test('Repaint boundary can get new parent after markNeedsCompositingBitsUpdate', () {
+    // Regression test for https://github.com/flutter/flutter/issues/24029.
+
+    final RenderRepaintBoundary repaintBoundary = RenderRepaintBoundary();
+    layout(repaintBoundary, phase: EnginePhase.flushSemantics);
+
+    repaintBoundary.markNeedsCompositingBitsUpdate();
+
+    renderer.renderView.child = null;
+    final RenderPadding padding = RenderPadding(
+      padding: const EdgeInsets.all(50),
+    );
+    renderer.renderView.child = padding;
+    padding.child = repaintBoundary;
+    pumpFrame(phase: EnginePhase.flushSemantics);
+  });
 }