[Impeller] Ensure that SnapshotControllerImpeller has a rendering context before creating the snapshot

shell/common/snapshot_controller_impeller.cc

@@ -18,6 +18,7 @@
 namespace flutter {
 
 namespace {
+
 sk_sp<DlImage> DoMakeRasterSnapshot(
     const sk_sp<DisplayList>& display_list,
     SkISize size,
@@ -53,6 +54,27 @@ sk_sp<DlImage> DoMakeRasterSnapshot(
       DlImage::OwningContext::kRaster);
 }
 
+sk_sp<DlImage> DoMakeRasterSnapshot(
+    const sk_sp<DisplayList>& display_list,
+    SkISize size,
+    const SnapshotController::Delegate& delegate) {
+  // Ensure that the current thread has a rendering context.  This must be done
+  // before calling GetAiksContext because constructing the AiksContext may
+  // invoke graphics APIs.
+  std::unique_ptr<Surface> pbuffer_surface;
+  if (delegate.GetSurface()) {
+    delegate.GetSurface()->MakeRenderContextCurrent();
+  } else if (delegate.GetSnapshotSurfaceProducer()) {
+    pbuffer_surface =
+        delegate.GetSnapshotSurfaceProducer()->CreateSnapshotSurface();
+    if (pbuffer_surface) {
+      pbuffer_surface->MakeRenderContextCurrent();
+    }
+  }
+
+  return DoMakeRasterSnapshot(display_list, size, delegate.GetAiksContext());
+}
+
 sk_sp<DlImage> DoMakeRasterSnapshot(
     sk_sp<DisplayList> display_list,
     SkISize picture_size,
@@ -112,16 +134,14 @@ void SnapshotControllerImpeller::MakeRasterSnapshot(
             }
 #endif
             callback(DoMakeRasterSnapshot(display_list, picture_size,
-                                          GetDelegate().GetAiksContext()));
+                                          GetDelegate()));
           }));
 }
 
 sk_sp<DlImage> SnapshotControllerImpeller::MakeRasterSnapshotSync(
     sk_sp<DisplayList> display_list,
     SkISize picture_size) {
-  return DoMakeRasterSnapshot(display_list, picture_size,
-                              GetDelegate().GetIsGpuDisabledSyncSwitch(),
-                              GetDelegate().GetAiksContext());
+  return DoMakeRasterSnapshot(display_list, picture_size, GetDelegate());
 }
 
 void SnapshotControllerImpeller::CacheRuntimeStage(

shell/platform/android/android_surface_gl_impeller.cc

@@ -81,7 +81,24 @@ bool AndroidSurfaceGLImpeller::SetNativeWindow(
 
 // |AndroidSurface|
 std::unique_ptr<Surface> AndroidSurfaceGLImpeller::CreateSnapshotSurface() {
-  FML_UNREACHABLE();
+  if (!onscreen_surface_ || !onscreen_surface_->IsValid()) {
+    onscreen_surface_ = android_context_->CreateOffscreenSurface();
+    if (!onscreen_surface_) {
+      FML_DLOG(ERROR) << "Could not create offscreen surface for snapshot.";
+      return nullptr;
+    }
+  }
+  // Make the snapshot surface current because constucting a
+  // GPUSurfaceGLImpeller and its AiksContext may invoke graphics APIs.
+  if (!android_context_->OnscreenContextMakeCurrent(onscreen_surface_.get())) {
+    FML_DLOG(ERROR) << "Could not make snapshot surface current.";
+    return nullptr;
+  }
+  return std::make_unique<GPUSurfaceGLImpeller>(
+      this,                                    // delegate
+      android_context_->GetImpellerContext(),  // context
+      true                                     // render to surface
+  );
 }
 
 // |AndroidSurface|

shell/platform/embedder/fixtures/main.dart

@@ -1595,3 +1595,20 @@ void render_impeller_text_test() {
   };
   PlatformDispatcher.instance.scheduleFrame();
 }
+
+@pragma('vm:entry-point')
+// ignore: non_constant_identifier_names
+Future<void> render_impeller_image_snapshot_test() async {
+  final PictureRecorder recorder = PictureRecorder();
+  final Canvas canvas = Canvas(recorder);
+  const Color color = Color.fromARGB(255, 0, 0, 123);
+  canvas.drawPaint(Paint()..color = color);
+  final Picture picture = recorder.endRecording();
+
+  final Image image = await picture.toImage(100, 100);
+  final ByteData? imageData = await image.toByteData();
+  final int pixel = imageData!.getInt32(0);
+
+  final bool result = (pixel & 0xFF) == color.alpha && ((pixel >> 8) & 0xFF) == color.blue;
+  notifyBoolValue(result);
+}

shell/platform/embedder/tests/embedder_gl_unittests.cc

@@ -4814,6 +4814,33 @@ TEST_F(EmbedderTest, CanRenderWithImpellerOpenGL) {
   ASSERT_FALSE(present_called);
 }
 
+TEST_F(EmbedderTest, ImpellerOpenGLImageSnapshot) {
+  auto& context = GetEmbedderContext<EmbedderTestContextGL>();
+
+  bool result = false;
+  fml::AutoResetWaitableEvent latch;
+  context.AddNativeCallback("NotifyBoolValue",
+                            CREATE_NATIVE_ENTRY([&](Dart_NativeArguments args) {
+                              result = tonic::DartConverter<bool>::FromDart(
+                                  Dart_GetNativeArgument(args, 0));
+                              latch.Signal();
+                            }));
+
+  EmbedderConfigBuilder builder(context);
+  builder.AddCommandLineArgument("--enable-impeller");
+  builder.SetDartEntrypoint("render_impeller_image_snapshot_test");
+  builder.SetSurface(SkISize::Make(800, 600));
+  builder.SetCompositor();
+  builder.SetRenderTargetType(
+      EmbedderTestBackingStoreProducer::RenderTargetType::kOpenGLFramebuffer);
+
+  auto engine = builder.LaunchEngine();
+  ASSERT_TRUE(engine.is_valid());
+  latch.Wait();
+
+  ASSERT_TRUE(result);
+}
+
 TEST_F(EmbedderTest, CompositorMustBeAbleToRenderToOpenGLSurface) {
   auto& context = GetEmbedderContext<EmbedderTestContextGL>();