Don't crash but warn when the scene builder specifies no layers. (flu…

…tter#14008)
elancom · Nov 25, 2019 · 9f64013 · 9f64013
1 parent c0db9aa
commit 9f64013
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Showing 3 changed files with 84 additions and 0 deletions.
diff --git a/flow/layers/layer_tree.cc b/flow/layers/layer_tree.cc
@@ -27,6 +27,12 @@ void LayerTree::RecordBuildTime(fml::TimePoint start) {
 void LayerTree::Preroll(CompositorContext::ScopedFrame& frame,
                         bool ignore_raster_cache) {
   TRACE_EVENT0("flutter", "LayerTree::Preroll");
+
+  if (!root_layer_) {
+    FML_LOG(ERROR) << "The scene did not specify any layers.";
+    return;
+  }
+
   SkColorSpace* color_space =
       frame.canvas() ? frame.canvas()->imageInfo().colorSpace() : nullptr;
   frame.context().raster_cache().SetCheckboardCacheImages(
@@ -75,6 +81,12 @@ void LayerTree::UpdateScene(SceneUpdateContext& context,
 void LayerTree::Paint(CompositorContext::ScopedFrame& frame,
                       bool ignore_raster_cache) const {
   TRACE_EVENT0("flutter", "LayerTree::Paint");
+
+  if (!root_layer_) {
+    FML_LOG(ERROR) << "The scene did not specify any layers to paint.";
+    return;
+  }
+
   SkISize canvas_size = frame.canvas()->getBaseLayerSize();
   SkNWayCanvas internal_nodes_canvas(canvas_size.width(), canvas_size.height());
   internal_nodes_canvas.addCanvas(frame.canvas());

diff --git a/shell/platform/embedder/fixtures/main.dart b/shell/platform/embedder/fixtures/main.dart
@@ -600,3 +600,23 @@ void platform_view_mutators_with_pixel_ratio() {
   };
   window.scheduleFrame();
 }
+
+@pragma('vm:entry-point')
+void empty_scene() {
+  window.onBeginFrame = (Duration duration) {
+    window.render(SceneBuilder().build());
+    signalNativeTest();
+  };
+  window.scheduleFrame();
+}
+
+@pragma('vm:entry-point')
+void scene_with_no_container() {
+  window.onBeginFrame = (Duration duration) {
+    SceneBuilder builder = SceneBuilder();
+    builder.addPicture(Offset(0.0, 0.0), CreateGradientBox(Size(400.0, 300.0)));
+    window.render(builder.build());
+    signalNativeTest();
+  };
+  window.scheduleFrame();
+}
diff --git a/shell/platform/embedder/tests/embedder_unittests.cc b/shell/platform/embedder/tests/embedder_unittests.cc
@@ -3499,5 +3499,57 @@ TEST_F(EmbedderTest,
   latch.Wait();
 }
 
+TEST_F(EmbedderTest, EmptySceneIsAcceptable) {
+  auto& context = GetEmbedderContext();
+
+  EmbedderConfigBuilder builder(context);
+  builder.SetOpenGLRendererConfig(SkISize::Make(800, 600));
+  builder.SetCompositor();
+  builder.SetDartEntrypoint("empty_scene");
+  fml::AutoResetWaitableEvent latch;
+  context.AddNativeCallback(
+      "SignalNativeTest",
+      CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) { latch.Signal(); }));
+
+  auto engine = builder.LaunchEngine();
+
+  ASSERT_TRUE(engine.is_valid());
+
+  FlutterWindowMetricsEvent event = {};
+  event.struct_size = sizeof(event);
+  event.width = 800;
+  event.height = 600;
+  event.pixel_ratio = 1.0;
+  ASSERT_EQ(FlutterEngineSendWindowMetricsEvent(engine.get(), &event),
+            kSuccess);
+  latch.Wait();
+}
+
+TEST_F(EmbedderTest, SceneWithNoRootContainerIsAcceptable) {
+  auto& context = GetEmbedderContext();
+
+  EmbedderConfigBuilder builder(context);
+  builder.SetOpenGLRendererConfig(SkISize::Make(800, 600));
+  builder.SetCompositor();
+  builder.SetDartEntrypoint("scene_with_no_container");
+  fml::AutoResetWaitableEvent latch;
+  context.AddNativeCallback(
+      "SignalNativeTest",
+      CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) { latch.Signal(); }));
+
+  auto engine = builder.LaunchEngine();
+
+  ASSERT_TRUE(engine.is_valid());
+
+  FlutterWindowMetricsEvent event = {};
+  event.struct_size = sizeof(event);
+  event.width = 800;
+  event.height = 600;
+  event.pixel_ratio = 1.0;
+  ASSERT_EQ(FlutterEngineSendWindowMetricsEvent(engine.get(), &event),
+            kSuccess);
+  latch.Wait();
+}
+
 }  // namespace testing
 }  // namespace flutter