Add `onUnregistered` callback in 'Texture' and 'FlutterTexture' (#12695)

Texture unregistration is finished on the GPU thread. The FlutterTexture implementation might not know when it is finished which leads to a race condition. Adding this callback so the FlutterTexture is aware of end of the unregistration process.

ci/licenses_golden/licenses_flutter

@@ -82,6 +82,7 @@ FILE: ../../../flutter/flow/skia_gpu_object.cc
 FILE: ../../../flutter/flow/skia_gpu_object.h
 FILE: ../../../flutter/flow/texture.cc
 FILE: ../../../flutter/flow/texture.h
+FILE: ../../../flutter/flow/texture_unittests.cc
 FILE: ../../../flutter/flow/view_holder.cc
 FILE: ../../../flutter/flow/view_holder.h
 FILE: ../../../flutter/flutter_frontend_server/bin/starter.dart

flow/BUILD.gn

@@ -114,6 +114,7 @@ executable("flow_unittests") {
     "matrix_decomposition_unittests.cc",
     "mutators_stack_unittests.cc",
     "raster_cache_unittests.cc",
+    "texture_unittests.cc",
   ]
 
   deps = [

flow/texture.cc

@@ -15,6 +15,7 @@ void TextureRegistry::RegisterTexture(std::shared_ptr<Texture> texture) {
 }
 
 void TextureRegistry::UnregisterTexture(int64_t id) {
+  mapping_[id]->OnTextureUnregistered();
   mapping_.erase(id);
 }
 

flow/texture.h

@@ -36,6 +36,9 @@ class Texture {
   // Called on GPU thread.
   virtual void MarkNewFrameAvailable() = 0;
 
+  // Called on GPU thread.
+  virtual void OnTextureUnregistered() = 0;
+
   int64_t Id() { return id_; }
 
  private:

flow/texture_unittests.cc

+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/flow/texture.h"
+#include "gtest/gtest.h"
+
+namespace flutter {
+namespace testing {
+
+class MockTexture : public Texture {
+ public:
+  MockTexture(int64_t textureId) : Texture(textureId) {}
+
+  ~MockTexture() override = default;
+
+  // Called from GPU thread.
+  void Paint(SkCanvas& canvas,
+             const SkRect& bounds,
+             bool freeze,
+             GrContext* context) override {}
+
+  void OnGrContextCreated() override {}
+
+  void OnGrContextDestroyed() override {}
+
+  void MarkNewFrameAvailable() override {}
+
+  void OnTextureUnregistered() override { unregistered_ = true; }
+
+  bool unregistered() { return unregistered_; }
+
+ private:
+  bool unregistered_ = false;
+};
+
+TEST(TextureRegistry, UnregisterTextureCallbackTriggered) {
+  TextureRegistry textureRegistry;
+  std::shared_ptr<MockTexture> mockTexture = std::make_shared<MockTexture>(0);
+  textureRegistry.RegisterTexture(mockTexture);
+  textureRegistry.UnregisterTexture(0);
+  ASSERT_TRUE(mockTexture->unregistered());
+}
+
+}  // namespace testing
+}  // namespace flutter

shell/common/shell_unittests.cc

@@ -799,5 +799,79 @@ TEST_F(ShellTest, CanCreateImagefromDecompressedBytes) {
   latch.Wait();
 }
 
+class MockTexture : public Texture {
+ public:
+  MockTexture(int64_t textureId,
+              std::shared_ptr<fml::AutoResetWaitableEvent> latch)
+      : Texture(textureId), latch_(latch) {}
+
+  ~MockTexture() override = default;
+
+  // Called from GPU thread.
+  void Paint(SkCanvas& canvas,
+             const SkRect& bounds,
+             bool freeze,
+             GrContext* context) override {}
+
+  void OnGrContextCreated() override {}
+
+  void OnGrContextDestroyed() override {}
+
+  void MarkNewFrameAvailable() override {
+    frames_available_++;
+    latch_->Signal();
+  }
+
+  void OnTextureUnregistered() override {
+    unregistered_ = true;
+    latch_->Signal();
+  }
+
+  bool unregistered() { return unregistered_; }
+  int frames_available() { return frames_available_; }
+
+ private:
+  bool unregistered_ = false;
+  int frames_available_ = 0;
+  std::shared_ptr<fml::AutoResetWaitableEvent> latch_;
+};
+
+TEST_F(ShellTest, TextureFrameMarkedAvailableAndUnregister) {
+  Settings settings = CreateSettingsForFixture();
+  auto configuration = RunConfiguration::InferFromSettings(settings);
+  auto task_runner = CreateNewThread();
+  TaskRunners task_runners("test", task_runner, task_runner, task_runner,
+                           task_runner);
+  std::unique_ptr<Shell> shell =
+      CreateShell(std::move(settings), std::move(task_runners));
+
+  ASSERT_TRUE(ValidateShell(shell.get()));
+  PlatformViewNotifyCreated(shell.get());
+
+  RunEngine(shell.get(), std::move(configuration));
+
+  std::shared_ptr<fml::AutoResetWaitableEvent> latch =
+      std::make_shared<fml::AutoResetWaitableEvent>();
+
+  std::shared_ptr<MockTexture> mockTexture =
+      std::make_shared<MockTexture>(0, latch);
+
+  fml::TaskRunner::RunNowOrPostTask(
+      shell->GetTaskRunners().GetGPUTaskRunner(), [&]() {
+        shell->GetPlatformView()->RegisterTexture(mockTexture);
+        shell->GetPlatformView()->MarkTextureFrameAvailable(0);
+      });
+  latch->Wait();
+
+  EXPECT_EQ(mockTexture->frames_available(), 1);
+
+  fml::TaskRunner::RunNowOrPostTask(
+      shell->GetTaskRunners().GetGPUTaskRunner(),
+      [&]() { shell->GetPlatformView()->UnregisterTexture(0); });
+  latch->Wait();
+
+  EXPECT_EQ(mockTexture->unregistered(), true);
+}
+
 }  // namespace testing
 }  // namespace flutter

shell/platform/android/android_external_texture_gl.cc

@@ -135,4 +135,6 @@ void AndroidExternalTextureGL::Detach() {
   }
 }
 
+void AndroidExternalTextureGL::OnTextureUnregistered() {}
+
 }  // namespace flutter

shell/platform/android/android_external_texture_gl.h

@@ -30,6 +30,8 @@ class AndroidExternalTextureGL : public flutter::Texture {
 
   void MarkNewFrameAvailable() override;
 
+  void OnTextureUnregistered() override;
+
  private:
   void Attach(jint textureName);
 

shell/platform/darwin/ios/framework/Headers/FlutterTexture.h

@@ -15,6 +15,14 @@ NS_ASSUME_NONNULL_BEGIN
 FLUTTER_EXPORT
 @protocol FlutterTexture <NSObject>
 - (CVPixelBufferRef _Nullable)copyPixelBuffer;
+
+/**
+ * Called when the texture is unregistered.
+ *
+ * Called on the GPU thread.
+ */
+@optional
+- (void)onTextureUnregistered:(NSObject<FlutterTexture>*)texture;
 @end
 
 FLUTTER_EXPORT

shell/platform/darwin/ios/ios_external_texture_gl.h

@@ -27,6 +27,8 @@ class IOSExternalTextureGL : public flutter::Texture {
 
   void MarkNewFrameAvailable() override;
 
+  void OnTextureUnregistered() override;
+
  private:
   void CreateTextureFromPixelBuffer();
 

shell/platform/darwin/ios/ios_external_texture_gl.mm

@@ -105,4 +105,10 @@ void IOSExternalTextureGL::MarkNewFrameAvailable() {
   new_frame_ready_ = true;
 }
 
+void IOSExternalTextureGL::OnTextureUnregistered() {
+  if ([external_texture_ respondsToSelector:@selector(onTextureUnregistered:)]) {
+    [external_texture_ onTextureUnregistered:external_texture_];
+  }
+}
+
 }  // namespace flutter

shell/platform/embedder/embedder_external_texture_gl.cc

@@ -44,4 +44,7 @@ void EmbedderExternalTextureGL::OnGrContextDestroyed() {}
 // |flutter::Texture|
 void EmbedderExternalTextureGL::MarkNewFrameAvailable() {}
 
+// |flutter::Texture|
+void EmbedderExternalTextureGL::OnTextureUnregistered() {}
+
 }  // namespace flutter

shell/platform/embedder/embedder_external_texture_gl.h

@@ -41,6 +41,9 @@ class EmbedderExternalTextureGL : public flutter::Texture {
   // |flutter::Texture|
   void MarkNewFrameAvailable() override;
 
+  // |flutter::Texture|
+  void OnTextureUnregistered() override;
+
   FML_DISALLOW_COPY_AND_ASSIGN(EmbedderExternalTextureGL);
 };