Create FlutterGLCompositor to render only one layer

ci/licenses_golden/licenses_flutter

@@ -1047,6 +1047,8 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FlutterPlug
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FlutterViewController.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Info.plist
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterAppDelegate.mm
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterBackingStoreData.h
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterBackingStoreData.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterDartProject.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterDartProject_Internal.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm
@@ -1056,6 +1058,8 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterExter
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureGL.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterFrameBufferProvider.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterFrameBufferProvider.mm
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterIOSurfaceHolder.h
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterIOSurfaceHolder.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.h

shell/platform/darwin/macos/BUILD.gn

@@ -46,6 +46,8 @@ source_set("flutter_framework_source") {
 
   sources = [
     "framework/Source/FlutterAppDelegate.mm",
+    "framework/Source/FlutterBackingStoreData.h",
+    "framework/Source/FlutterBackingStoreData.mm",
     "framework/Source/FlutterDartProject.mm",
     "framework/Source/FlutterDartProject_Internal.h",
     "framework/Source/FlutterEngine.mm",
@@ -54,6 +56,10 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterExternalTextureGL.mm",
     "framework/Source/FlutterFrameBufferProvider.h",
     "framework/Source/FlutterFrameBufferProvider.mm",
+    "framework/Source/FlutterGLCompositor.h",
+    "framework/Source/FlutterGLCompositor.mm",
+    "framework/Source/FlutterIOSurfaceHolder.h",
+    "framework/Source/FlutterIOSurfaceHolder.mm",
     "framework/Source/FlutterMouseCursorPlugin.h",
     "framework/Source/FlutterMouseCursorPlugin.mm",
     "framework/Source/FlutterResizeSynchronizer.h",
@@ -75,9 +81,12 @@ source_set("flutter_framework_source") {
   sources += _flutter_framework_headers
 
   deps = [
+    "//flutter/flow:flow",
+    "//flutter/fml",
     "//flutter/shell/platform/common/cpp:common_cpp_switches",
     "//flutter/shell/platform/darwin/common:framework_shared",
     "//flutter/shell/platform/embedder:embedder_as_internal_library",
+    "//third_party/skia",
   ]
 
   public_configs = [ "//flutter:config" ]
@@ -117,7 +126,10 @@ executable("flutter_desktop_darwin_unittests") {
 
   sources = [
     "framework/Source/FlutterEngineTest.mm",
+    "framework/Source/FlutterGLCompositorUnittests.mm",
     "framework/Source/FlutterViewControllerTest.mm",
+    "framework/Source/FlutterViewControllerTestUtils.h",
+    "framework/Source/FlutterViewControllerTestUtils.mm",
   ]
 
   cflags_objcc = [ "-fobjc-arc" ]

shell/platform/darwin/macos/framework/Source/FlutterBackingStoreData.h

@@ -0,0 +1,17 @@
+// 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.
+
+#import <Cocoa/Cocoa.h>
+
+/**
+ * FlutterBackingStoreData holds data to be stored in the
+ * BackingStore's user_data.
+ */
+@interface FlutterBackingStoreData : NSObject
+
+- (nullable instancetype)initWithIsRootView:(bool)isRootView;
+
+- (bool)isRootView;
+
+@end

shell/platform/darwin/macos/framework/Source/FlutterBackingStoreData.mm

@@ -0,0 +1,27 @@
+// 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.
+
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterBackingStoreData.h"
+
+#include <OpenGL/gl.h>
+
+@interface FlutterBackingStoreData () {
+  bool _isRootView;
+}
+@end
+
+@implementation FlutterBackingStoreData
+
+- (nullable instancetype)initWithIsRootView:(bool)isRootView {
+  if (self = [super init]) {
+    _isRootView = isRootView;
+  }
+  return self;
+}
+
+- (bool)isRootView {
+  return _isRootView;
+}
+
+@end

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -10,7 +10,7 @@
 
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterDartProject_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureGL.h"
-#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.h"
 #import "flutter/shell/platform/embedder/embedder.h"
 
 /**
@@ -197,6 +197,13 @@ @implementation FlutterEngine {
 
   // Pointer to the Dart AOT snapshot and instruction data.
   _FlutterEngineAOTData* _aotData;
+
+  // _macOSGLCompositor is created when the engine is created and
+  // it's destruction is handled by ARC when the engine is destroyed.
+  std::unique_ptr<flutter::FlutterGLCompositor> _macOSGLCompositor;
+
+  // FlutterCompositor is copied and used in embedder.cc.
+  FlutterCompositor _compositor;
 }
 
 - (instancetype)initWithName:(NSString*)labelPrefix project:(FlutterDartProject*)project {
@@ -306,6 +313,8 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
     flutterArguments.aot_data = _aotData;
   }
 
+  flutterArguments.compositor = [self createFlutterCompositor];
+
   FlutterEngineResult result = _embedderAPI.Initialize(
       FLUTTER_ENGINE_VERSION, &rendererConfig, &flutterArguments, (__bridge void*)(self), &_engine);
   if (result != kSuccess) {
@@ -360,6 +369,45 @@ - (void)setViewController:(FlutterViewController*)controller {
   }
 }
 
+- (FlutterCompositor*)createFlutterCompositor {
+  [_mainOpenGLContext makeCurrentContext];
+
+  _macOSGLCompositor = std::make_unique<flutter::FlutterGLCompositor>(_viewController);
+
+  _compositor = {};
+  _compositor.struct_size = sizeof(FlutterCompositor);
+  _compositor.user_data = _macOSGLCompositor.get();
+
+  _compositor.create_backing_store_callback = [](const FlutterBackingStoreConfig* config,  //
+                                                 FlutterBackingStore* backing_store_out,   //
+                                                 void* user_data                           //
+                                              ) {
+    return reinterpret_cast<flutter::FlutterGLCompositor*>(user_data)->CreateBackingStore(
+        config, backing_store_out);
+  };
+
+  _compositor.collect_backing_store_callback = [](const FlutterBackingStore* backing_store,  //
+                                                  void* user_data                            //
+                                               ) {
+    return reinterpret_cast<flutter::FlutterGLCompositor*>(user_data)->CollectBackingStore(
+        backing_store);
+  };
+
+  _compositor.present_layers_callback = [](const FlutterLayer** layers,  //
+                                           size_t layers_count,          //
+                                           void* user_data               //
+                                        ) {
+    return reinterpret_cast<flutter::FlutterGLCompositor*>(user_data)->Present(layers,
+                                                                               layers_count);
+  };
+
+  __weak FlutterEngine* weak_self = self;
+  _macOSGLCompositor->SetPresentCallback(
+      [weak_self]() { return [weak_self engineCallbackOnPresent]; });
+
+  return &_compositor;
+}
+
 - (id<FlutterBinaryMessenger>)binaryMessenger {
   // TODO(stuartmorgan): Switch to FlutterBinaryMessengerRelay to avoid plugins
   // keeping the engine alive.

shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.h

@@ -0,0 +1,56 @@
+// 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 <vector>
+
+#include "flutter/fml/macros.h"
+#include "flutter/shell/platform/darwin/macos/framework/Source/FlutterSurfaceManager.h"
+#include "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
+#include "flutter/shell/platform/embedder/embedder.h"
+#include "third_party/skia/include/gpu/GrDirectContext.h"
+
+namespace flutter {
+
+// FlutterGLCompositor creates and manages the backing stores used for
+// rendering Flutter content and presents Flutter content and Platform views.
+// Platform views are not yet supported.
+// FlutterGLCompositor is created and destroyed by FlutterEngine.
+class FlutterGLCompositor {
+ public:
+  FlutterGLCompositor(FlutterViewController* view_controller);
+
+  // Creates a BackingStore and saves updates the backing_store_out
+  // data with the new BackingStore data.
+  // If the view requesting the backing store is the root view,
+  // we do not create a new backing store but rather return the
+  // backing store associated with the root view's FlutterSurfaceManager.
+  //
+  // Any additional state allocated for the backing store and
+  // saved as user_data in the backing store must be collected
+  // in the backing_store's desctruction_callback field which will
+  // be called when the embedder collects the backing store.
+  bool CreateBackingStore(const FlutterBackingStoreConfig* config,
+                          FlutterBackingStore* backing_store_out);
+
+  // Releases the memory for any state used by the backing store.
+  bool CollectBackingStore(const FlutterBackingStore* backing_store);
+
+  // Presents the FlutterLayers by updating FlutterView(s) using the
+  // layer content.
+  bool Present(const FlutterLayer** layers, size_t layers_count);
+
+  using PresentCallback = std::function<bool()>;
+
+  // PresentCallback is called at the end of the Present function.
+  void SetPresentCallback(const PresentCallback& present_callback);
+
+ private:
+  FlutterViewController* view_controller_;
+  PresentCallback present_callback_;
+  NSOpenGLContext* open_gl_context_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(FlutterGLCompositor);
+};
+
+}  // namespace flutter

shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.mm

@@ -0,0 +1,88 @@
+// 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.
+
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterBackingStoreData.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterFrameBufferProvider.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterIOSurfaceHolder.h"
+
+#import <OpenGL/gl.h>
+#import "flutter/fml/logging.h"
+#import "flutter/fml/platform/darwin/cf_utils.h"
+#import "third_party/skia/include/core/SkCanvas.h"
+#import "third_party/skia/include/core/SkSurface.h"
+#import "third_party/skia/include/gpu/gl/GrGLAssembleInterface.h"
+#import "third_party/skia/include/utils/mac/SkCGUtils.h"
+
+#include <unistd.h>
+
+namespace flutter {
+
+FlutterGLCompositor::FlutterGLCompositor(FlutterViewController* view_controller)
+    : view_controller_(view_controller),
+      open_gl_context_(view_controller.flutterView.openGLContext) {}
+
+bool FlutterGLCompositor::CreateBackingStore(const FlutterBackingStoreConfig* config,
+                                             FlutterBackingStore* backing_store_out) {
+  CGSize size = CGSizeMake(config->size.width, config->size.height);
+  FlutterBackingStoreData* data =
+      [[FlutterBackingStoreData alloc] initWithIsRootView:config->is_root_view];
+
+  backing_store_out->type = kFlutterBackingStoreTypeOpenGL;
+  backing_store_out->is_cacheable = true;
+  backing_store_out->open_gl.type = kFlutterOpenGLTargetTypeFramebuffer;
+  backing_store_out->open_gl.framebuffer.target = GL_RGBA8;
+
+  if (config->is_root_view) {
+    // The root view uses FlutterSurfaceManager and is not cacheable since
+    // the fbo id changes on every present.
+    backing_store_out->is_cacheable = false;
+    auto fbo = [view_controller_.flutterView frameBufferIDForSize:size];
+    backing_store_out->open_gl.framebuffer.name = fbo;
+  } else {
+    FML_CHECK(false) << "Compositor only supports creating a backing store for the root view";
+  }
+
+  backing_store_out->open_gl.framebuffer.user_data = (__bridge_retained void*)data;
+  backing_store_out->open_gl.framebuffer.destruction_callback = [](void* user_data) {
+    if (user_data != nullptr) {
+      CFRelease(user_data);
+    }
+  };
+
+  return true;
+}
+
+bool FlutterGLCompositor::CollectBackingStore(const FlutterBackingStore* backing_store) {
+  return true;
+}
+
+bool FlutterGLCompositor::Present(const FlutterLayer** layers, size_t layers_count) {
+  for (size_t i = 0; i < layers_count; ++i) {
+    const auto* layer = layers[i];
+    FlutterBackingStore* backing_store = const_cast<FlutterBackingStore*>(layer->backing_store);
+    switch (layer->type) {
+      case kFlutterLayerContentTypeBackingStore: {
+        FlutterBackingStoreData* data =
+            (__bridge FlutterBackingStoreData*)(backing_store->open_gl.framebuffer.user_data);
+        if (![data isRootView]) {
+          FML_CHECK(false) << "Compositor only supports presenting the root view.";
+        }
+        break;
+      }
+      case kFlutterLayerContentTypePlatformView:
+        // Add functionality in follow up PR.
+        FML_CHECK(false) << "Presenting PlatformViews not yet supported";
+        break;
+    };
+  }
+  return present_callback_();
+}
+
+void FlutterGLCompositor::SetPresentCallback(
+    const FlutterGLCompositor::PresentCallback& present_callback) {
+  present_callback_ = present_callback;
+}
+
+}  // namespace flutter

shell/platform/darwin/macos/framework/Source/FlutterGLCompositorUnittests.mm

@@ -0,0 +1,29 @@
+// 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.
+
+#import <Foundation/Foundation.h>
+
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewControllerTestUtils.h"
+#import "flutter/testing/testing.h"
+
+namespace flutter::testing {
+
+TEST(FlutterGLCompositorTest, TestPresent) {
+  id mockViewController = CreateMockViewController(nil);
+
+  std::unique_ptr<flutter::FlutterGLCompositor> macos_compositor =
+      std::make_unique<FlutterGLCompositor>(mockViewController);
+
+  bool flag = false;
+  macos_compositor->SetPresentCallback([f = &flag]() {
+    *f = true;
+    return true;
+  });
+
+  ASSERT_TRUE(macos_compositor->Present(nil, 0));
+  ASSERT_TRUE(flag);
+}
+
+}  // flutter::testing

shell/platform/darwin/macos/framework/Source/FlutterIOSurfaceHolder.h

@@ -0,0 +1,29 @@
+// 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.
+
+#import <Cocoa/Cocoa.h>
+
+/**
+ * FlutterIOSurfaceHolder maintains an IOSurface
+ * and provides an interface to bind the IOSurface to a texture.
+ */
+@interface FlutterIOSurfaceHolder : NSObject
+
+/**
+ * Bind the IOSurface to the provided texture and fbo.
+ */
+- (void)bindSurfaceToTexture:(GLuint)texture fbo:(GLuint)fbo size:(CGSize)size;
+
+/**
+ * Releases the current IOSurface if one exists
+ * and creates a new IOSurface with the specified size.
+ */
+- (void)recreateIOSurfaceWithSize:(CGSize)size;
+
+/**
+ * Returns a reference to the underlying IOSurface.
+ */
+- (const IOSurfaceRef&)ioSurface;
+
+@end