Reduce the size of Overlay FlutterImageView in HC mode

shell/platform/android/external_view_embedder/external_view_embedder.cc

@@ -126,7 +126,7 @@ void AndroidExternalViewEmbedder::SubmitFrame(
 
     slice->end_recording();
 
-    SkRect joined_rect = SkRect::MakeEmpty();
+    SkRect full_joined_rect = SkRect::MakeEmpty();
 
     // Determinate if Flutter UI intersects with any of the previous
     // platform views stacked by z position.
@@ -137,6 +137,8 @@ void AndroidExternalViewEmbedder::SubmitFrame(
     for (ssize_t j = i; j >= 0; j--) {
       int64_t current_view_id = composition_order_[j];
       SkRect current_view_rect = GetViewRect(current_view_id);
+      // The rect above the `current_view_rect`
+      SkRect partial_joined_rect = SkRect::MakeEmpty();
       // Each rect corresponds to a native view that renders Flutter UI.
       std::list<SkRect> intersection_rects =
           slice->searchNonOverlappingDrawnRects(current_view_rect);
@@ -146,21 +148,26 @@ void AndroidExternalViewEmbedder::SubmitFrame(
       // In this case, the rects are merged into a single one that is the union
       // of all the rects.
       for (const SkRect& rect : intersection_rects) {
-        joined_rect.join(rect);
+        partial_joined_rect.join(rect);
       }
+      // Get the intersection rect with the `current_view_rect`,
+      partial_joined_rect.intersect(current_view_rect);
+      // Join the `partial_joined_rect` into `full_joined_rect` to get the rect
+      // above the current `slice`
+      full_joined_rect.join(partial_joined_rect);
     }
-    if (!joined_rect.isEmpty()) {
+    if (!full_joined_rect.isEmpty()) {
       // Subpixels in the platform may not align with the canvas subpixels.
       //
       // To workaround it, round the floating point bounds and make the rect
       // slightly larger.
       //
       // For example, {0.3, 0.5, 3.1, 4.7} becomes {0, 0, 4, 5}.
-      joined_rect.set(joined_rect.roundOut());
-      overlay_layers.insert({view_id, joined_rect});
+      full_joined_rect.set(full_joined_rect.roundOut());
+      overlay_layers.insert({view_id, full_joined_rect});
       // Clip the background canvas, so it doesn't contain any of the pixels
       // drawn on the overlay layer.
-      background_canvas->clipRect(joined_rect, SkClipOp::kDifference);
+      background_canvas->clipRect(full_joined_rect, SkClipOp::kDifference);
     }
     if (background_builder) {
       slice->render_into(background_builder);

shell/platform/android/external_view_embedder/external_view_embedder_unittests.cc

@@ -425,7 +425,7 @@ TEST(AndroidExternalViewEmbedder, SubmitFrame) {
                                0, 150, 150, 300, 300, 300, 300, stack1));
     // The JNI call to display the overlay surface.
     EXPECT_CALL(*jni_mock,
-                FlutterViewDisplayOverlaySurface(0, 50, 50, 200, 200));
+                FlutterViewDisplayOverlaySurface(0, 150, 150, 100, 100));
 
     auto did_submit_frame = false;
     auto surface_frame = std::make_unique<SurfaceFrame>(
@@ -491,7 +491,7 @@ TEST(AndroidExternalViewEmbedder, SubmitFrame) {
                                0, 150, 150, 300, 300, 300, 300, stack1));
     // The JNI call to display the overlay surface.
     EXPECT_CALL(*jni_mock,
-                FlutterViewDisplayOverlaySurface(0, 50, 50, 200, 200));
+                FlutterViewDisplayOverlaySurface(0, 150, 150, 100, 100));
 
     auto did_submit_frame = false;
     auto surface_frame = std::make_unique<SurfaceFrame>(
@@ -516,6 +516,108 @@ TEST(AndroidExternalViewEmbedder, SubmitFrame) {
   }
 }
 
+TEST(AndroidExternalViewEmbedder, OverlayCoverTwoPlatformViews) {
+  // In this test we will simulate two Android views appearing on the screen
+  // with a rect intersecting both of them
+
+  auto jni_mock = std::make_shared<JNIMock>();
+  auto android_context =
+      std::make_shared<AndroidContext>(AndroidRenderingAPI::kSoftware);
+
+  auto window = fml::MakeRefCounted<AndroidNativeWindow>(nullptr);
+  auto gr_context = GrDirectContext::MakeMock(nullptr);
+  auto frame_size = SkISize::Make(1000, 1000);
+  SurfaceFrame::FramebufferInfo framebuffer_info;
+  auto surface_factory = std::make_shared<TestAndroidSurfaceFactory>(
+      [&android_context, gr_context, window, frame_size, framebuffer_info]() {
+        auto surface_frame_1 = std::make_unique<SurfaceFrame>(
+            SkSurface::MakeNull(1000, 1000), framebuffer_info,
+            [](const SurfaceFrame& surface_frame, SkCanvas* canvas) {
+              return true;
+            },
+            /*frame_size=*/SkISize::Make(800, 600));
+
+        auto surface_mock = std::make_unique<SurfaceMock>();
+        EXPECT_CALL(*surface_mock, AcquireFrame(frame_size))
+            .Times(1 /* frames */)
+            .WillOnce(Return(ByMove(std::move(surface_frame_1))));
+
+        auto android_surface_mock =
+            std::make_unique<AndroidSurfaceMock>(android_context);
+        EXPECT_CALL(*android_surface_mock, IsValid()).WillOnce(Return(true));
+
+        EXPECT_CALL(*android_surface_mock, CreateGPUSurface(gr_context.get()))
+            .WillOnce(Return(ByMove(std::move(surface_mock))));
+
+        EXPECT_CALL(*android_surface_mock, SetNativeWindow(window));
+        return android_surface_mock;
+      });
+  auto embedder = std::make_unique<AndroidExternalViewEmbedder>(
+      *android_context, jni_mock, surface_factory, GetTaskRunnersForFixture());
+
+  auto raster_thread_merger = GetThreadMergerFromPlatformThread();
+
+  EXPECT_CALL(*jni_mock, FlutterViewBeginFrame());
+  embedder->BeginFrame(frame_size, nullptr, 1.5, raster_thread_merger);
+
+  {
+    // Add first Android view.
+    SkMatrix matrix = SkMatrix::Translate(100, 100);
+    MutatorsStack stack;
+    embedder->PrerollCompositeEmbeddedView(
+        0, std::make_unique<EmbeddedViewParams>(matrix, SkSize::Make(100, 100),
+                                                stack));
+    // The JNI call to display the Android view.
+    EXPECT_CALL(*jni_mock, FlutterViewOnDisplayPlatformView(
+                               0, 100, 100, 100, 100, 150, 150, stack));
+  }
+
+  {
+    // Add second Android view.
+    SkMatrix matrix = SkMatrix::Translate(300, 100);
+    MutatorsStack stack;
+    embedder->PrerollCompositeEmbeddedView(
+        1, std::make_unique<EmbeddedViewParams>(matrix, SkSize::Make(100, 100),
+                                                stack));
+    // The JNI call to display the Android view.
+    EXPECT_CALL(*jni_mock, FlutterViewOnDisplayPlatformView(
+                               1, 300, 100, 100, 100, 150, 150, stack));
+  }
+  auto rect_paint = SkPaint();
+  rect_paint.setColor(SkColors::kCyan);
+  rect_paint.setStyle(SkPaint::Style::kFill_Style);
+
+  // This simulates Flutter UI that intersects with the two Android views.
+  // Since we will compute the intersection for each android view in turn, and
+  // finally merge The final size of the overlay will be smaller than the
+  // width and height of the rect.
+  embedder->CompositeEmbeddedView(1).canvas->drawRect(
+      SkRect::MakeXYWH(150, 50, 200, 200), rect_paint);
+
+  EXPECT_CALL(*jni_mock, FlutterViewCreateOverlaySurface())
+      .WillRepeatedly([&]() {
+        return std::make_unique<PlatformViewAndroidJNI::OverlayMetadata>(
+            1, window);
+      });
+
+  // The JNI call to display the overlay surface.
+  EXPECT_CALL(*jni_mock,
+              FlutterViewDisplayOverlaySurface(1, 150, 100, 200, 100))
+      .Times(1);
+
+  auto surface_frame = std::make_unique<SurfaceFrame>(
+      SkSurface::MakeNull(1000, 1000), framebuffer_info,
+      [](const SurfaceFrame& surface_frame, SkCanvas* canvas) mutable {
+        return true;
+      },
+      /*frame_size=*/SkISize::Make(800, 600));
+
+  embedder->SubmitFrame(gr_context.get(), std::move(surface_frame));
+
+  EXPECT_CALL(*jni_mock, FlutterViewEndFrame());
+  embedder->EndFrame(/*should_resubmit_frame=*/false, raster_thread_merger);
+}
+
 TEST(AndroidExternalViewEmbedder, SubmitFrameOverlayComposition) {
   auto jni_mock = std::make_shared<JNIMock>();
   auto android_context =
@@ -776,7 +878,7 @@ TEST(AndroidExternalViewEmbedder, DestroyOverlayLayersOnSizeChange) {
     EXPECT_CALL(*jni_mock, FlutterViewOnDisplayPlatformView(0, 0, 0, 200, 200,
                                                             300, 300, stack1));
     EXPECT_CALL(*jni_mock,
-                FlutterViewDisplayOverlaySurface(0, 50, 50, 200, 200));
+                FlutterViewDisplayOverlaySurface(0, 50, 50, 150, 150));
 
     SurfaceFrame::FramebufferInfo framebuffer_info;
     auto surface_frame = std::make_unique<SurfaceFrame>(
@@ -865,7 +967,7 @@ TEST(AndroidExternalViewEmbedder, DoesNotDestroyOverlayLayersOnSizeChange) {
     EXPECT_CALL(*jni_mock, FlutterViewOnDisplayPlatformView(0, 0, 0, 200, 200,
                                                             300, 300, stack1));
     EXPECT_CALL(*jni_mock,
-                FlutterViewDisplayOverlaySurface(0, 50, 50, 200, 200));
+                FlutterViewDisplayOverlaySurface(0, 50, 50, 150, 150));
 
     auto surface_frame = std::make_unique<SurfaceFrame>(
         SkSurface::MakeNull(1000, 1000), framebuffer_info,