Fix UiKitView which wrongly unconditionally repaints (#111790)

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

@@ -320,10 +320,13 @@ class RenderUiKitView extends RenderBox {
   /// must have been created by calling [PlatformViewsService.initUiKitView].
   UiKitViewController get viewController => _viewController;
   UiKitViewController _viewController;
-  set viewController(UiKitViewController viewController) {
+  set viewController(UiKitViewController value) {
-    assert(viewController != null);
+    assert(value != null);
-    final bool needsSemanticsUpdate = _viewController.id != viewController.id;
+    if (_viewController == value) {
-    _viewController = viewController;
+      return;
+    }
+    final bool needsSemanticsUpdate = _viewController.id != value.id;
+    _viewController = value;
     markNeedsPaint();
     if (needsSemanticsUpdate) {
       markNeedsSemanticsUpdate();

packages/flutter/test/rendering/platform_view_test.dart

@@ -260,6 +260,42 @@ void main() {
       expect(renderBox.debugLayer, isNull);
     });
   });
+
+  test('markNeedsPaint does not get called when setting the same viewController', () {
+    FakeAsync().run((FakeAsync async) {
+      final Completer<void> viewCreation = Completer<void>();
+      const MethodChannel channel = MethodChannel('flutter/platform_views');
+      binding.defaultBinaryMessenger.setMockMethodCallHandler(channel, (MethodCall methodCall) async {
+        assert(methodCall.method == 'create', 'Unexpected method call');
+        await viewCreation.future;
+        return /*textureId=*/ 0;
+      });
+
+      bool futureCallbackRan = false;
+
+      PlatformViewsService.initUiKitView(id: 0, viewType: 'webview', layoutDirection: TextDirection.ltr).then((UiKitViewController viewController) {
+        final RenderUiKitView renderBox = RenderUiKitView(
+          viewController: viewController,
+          hitTestBehavior: PlatformViewHitTestBehavior.opaque,
+          gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>{},
+        );
+
+        layout(renderBox);
+        pumpFrame(phase: EnginePhase.paint);
+        expect(renderBox.debugNeedsPaint, isFalse);
+
+        renderBox.viewController = viewController;
+
+        expect(renderBox.debugNeedsPaint, isFalse);
+
+        futureCallbackRan = true;
+      });
+
+      viewCreation.complete();
+      async.flushMicrotasks();
+      expect(futureCallbackRan, true);
+    });
+  });
 }
 
 ui.PointerData _pointerData(