[Impeller] Delete any remaining GL objects during destruction of the ReactorGLES (flutter/engine#56361)

At shutdown time the ReactorGLES may still be holding handles of GL objects.  These objects should be cleaned up when the reactor is deleted.

This leak can be seen by running DlGoldenTest.ShimmerTest, which takes a series of screenshots.  Each screenshot creates an AiksContext. Without this change, the textures in the AiksContext's ReactorGLES will be leaked after the AiksContext is destroyed.

engine/src/flutter/impeller/renderer/backend/gles/reactor_gles.cc

@@ -13,6 +13,55 @@
 
 namespace impeller {
 
+static std::optional<GLuint> CreateGLHandle(const ProcTableGLES& gl,
+                                            HandleType type) {
+  GLuint handle = GL_NONE;
+  switch (type) {
+    case HandleType::kUnknown:
+      return std::nullopt;
+    case HandleType::kTexture:
+      gl.GenTextures(1u, &handle);
+      return handle;
+    case HandleType::kBuffer:
+      gl.GenBuffers(1u, &handle);
+      return handle;
+    case HandleType::kProgram:
+      return gl.CreateProgram();
+    case HandleType::kRenderBuffer:
+      gl.GenRenderbuffers(1u, &handle);
+      return handle;
+    case HandleType::kFrameBuffer:
+      gl.GenFramebuffers(1u, &handle);
+      return handle;
+  }
+  return std::nullopt;
+}
+
+static bool CollectGLHandle(const ProcTableGLES& gl,
+                            HandleType type,
+                            GLuint handle) {
+  switch (type) {
+    case HandleType::kUnknown:
+      return false;
+    case HandleType::kTexture:
+      gl.DeleteTextures(1u, &handle);
+      return true;
+    case HandleType::kBuffer:
+      gl.DeleteBuffers(1u, &handle);
+      return true;
+    case HandleType::kProgram:
+      gl.DeleteProgram(handle);
+      return true;
+    case HandleType::kRenderBuffer:
+      gl.DeleteRenderbuffers(1u, &handle);
+      return true;
+    case HandleType::kFrameBuffer:
+      gl.DeleteFramebuffers(1u, &handle);
+      return true;
+  }
+  return false;
+}
+
 ReactorGLES::ReactorGLES(std::unique_ptr<ProcTableGLES> gl)
     : proc_table_(std::move(gl)) {
   if (!proc_table_ || !proc_table_->IsValid()) {
@@ -23,7 +72,17 @@ ReactorGLES::ReactorGLES(std::unique_ptr<ProcTableGLES> gl)
   is_valid_ = true;
 }
 
-ReactorGLES::~ReactorGLES() = default;
+ReactorGLES::~ReactorGLES() {
+  if (CanReactOnCurrentThread()) {
+    for (auto& handle : handles_) {
+      if (handle.second.name.has_value()) {
+        CollectGLHandle(*proc_table_, handle.first.type,
+                        handle.second.name.value());
+      }
+    }
+    proc_table_->Flush();
+  }
+}
 
 bool ReactorGLES::IsValid() const {
   return is_valid_;
@@ -99,55 +158,6 @@ bool ReactorGLES::RegisterCleanupCallback(const HandleGLES& handle,
   return false;
 }
 
-static std::optional<GLuint> CreateGLHandle(const ProcTableGLES& gl,
-                                            HandleType type) {
-  GLuint handle = GL_NONE;
-  switch (type) {
-    case HandleType::kUnknown:
-      return std::nullopt;
-    case HandleType::kTexture:
-      gl.GenTextures(1u, &handle);
-      return handle;
-    case HandleType::kBuffer:
-      gl.GenBuffers(1u, &handle);
-      return handle;
-    case HandleType::kProgram:
-      return gl.CreateProgram();
-    case HandleType::kRenderBuffer:
-      gl.GenRenderbuffers(1u, &handle);
-      return handle;
-    case HandleType::kFrameBuffer:
-      gl.GenFramebuffers(1u, &handle);
-      return handle;
-  }
-  return std::nullopt;
-}
-
-static bool CollectGLHandle(const ProcTableGLES& gl,
-                            HandleType type,
-                            GLuint handle) {
-  switch (type) {
-    case HandleType::kUnknown:
-      return false;
-    case HandleType::kTexture:
-      gl.DeleteTextures(1u, &handle);
-      return true;
-    case HandleType::kBuffer:
-      gl.DeleteBuffers(1u, &handle);
-      return true;
-    case HandleType::kProgram:
-      gl.DeleteProgram(handle);
-      return true;
-    case HandleType::kRenderBuffer:
-      gl.DeleteRenderbuffers(1u, &handle);
-      return true;
-    case HandleType::kFrameBuffer:
-      gl.DeleteFramebuffers(1u, &handle);
-      return true;
-  }
-  return false;
-}
-
 HandleGLES ReactorGLES::CreateHandle(HandleType type, GLuint external_handle) {
   if (type == HandleType::kUnknown) {
     return HandleGLES::DeadHandle();

engine/src/flutter/impeller/renderer/backend/gles/test/mock_gles.cc

@@ -160,6 +160,10 @@ void mockDeleteQueriesEXT(GLsizei size, const GLuint* queries) {
   RecordGLCall("glDeleteQueriesEXT");
 }
 
+void mockDeleteTextures(GLsizei size, const GLuint* queries) {
+  RecordGLCall("glDeleteTextures");
+}
+
 static_assert(CheckSameSignature<decltype(mockDeleteQueriesEXT),  //
                                  decltype(glDeleteQueriesEXT)>::value);
 
@@ -198,6 +202,8 @@ const ProcTableGLES::Resolver kMockResolverGLES = [](const char* name) {
     return reinterpret_cast<void*>(&mockEndQueryEXT);
   } else if (strcmp(name, "glDeleteQueriesEXT") == 0) {
     return reinterpret_cast<void*>(&mockDeleteQueriesEXT);
+  } else if (strcmp(name, "glDeleteTextures") == 0) {
+    return reinterpret_cast<void*>(&mockDeleteTextures);
   } else if (strcmp(name, "glGetQueryObjectui64vEXT") == 0) {
     return reinterpret_cast<void*>(mockGetQueryObjectui64vEXT);
   } else if (strcmp(name, "glGetQueryObjectuivEXT") == 0) {

engine/src/flutter/impeller/renderer/backend/gles/test/reactor_unittests.cc

@@ -43,5 +43,22 @@ TEST(ReactorGLES, CanAttachCleanupCallbacksToHandles) {
   EXPECT_EQ(value, 1);
 }
 
+TEST(ReactorGLES, DeletesHandlesDuringShutdown) {
+  auto mock_gles = MockGLES::Init();
+  ProcTableGLES::Resolver resolver = kMockResolverGLES;
+  auto proc_table = std::make_unique<ProcTableGLES>(resolver);
+  auto worker = std::make_shared<TestWorker>();
+  auto reactor = std::make_shared<ReactorGLES>(std::move(proc_table));
+  reactor->AddWorker(worker);
+
+  reactor->CreateHandle(HandleType::kTexture, 123);
+
+  reactor.reset();
+
+  auto calls = mock_gles->GetCapturedCalls();
+  EXPECT_TRUE(std::find(calls.begin(), calls.end(), "glDeleteTextures") !=
+              calls.end());
+}
+
 }  // namespace testing
 }  // namespace impeller