[macOS] Revert breaking change to FlutterEngine public API (#22592)

Author: iskakaushik

ci/licenses_golden/licenses_flutter

@@ -1054,8 +1054,6 @@ 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/FlutterMouseCursorPlugin.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.mm
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterSurfaceManager.h

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

@@ -39,7 +39,7 @@ FLUTTER_EXPORT
 /**
  * Registers a `FlutterTexture` for usage in Flutter and returns an id that can be used to reference
  * that texture when calling into Flutter with channels. Textures must be registered on the
- * platform thread. On success returns the pointer to the registered texture, else returns 0.
+ * platform thread.
  */
 - (int64_t)registerTexture:(NSObject<FlutterTexture>*)texture;
 /**

shell/platform/darwin/macos/BUILD.gn

@@ -54,8 +54,6 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterExternalTextureGL.mm",
     "framework/Source/FlutterMouseCursorPlugin.h",
     "framework/Source/FlutterMouseCursorPlugin.mm",
-    "framework/Source/FlutterOpenGLRenderer.h",
-    "framework/Source/FlutterOpenGLRenderer.mm",
     "framework/Source/FlutterResizeSynchronizer.h",
     "framework/Source/FlutterResizeSynchronizer.mm",
     "framework/Source/FlutterSurfaceManager.h",

shell/platform/darwin/macos/framework/Headers/FlutterEngine.h

@@ -21,7 +21,7 @@
  * Coordinates a single instance of execution of a Flutter engine.
  */
 FLUTTER_EXPORT
-@interface FlutterEngine : NSObject <FlutterPluginRegistry>
+@interface FlutterEngine : NSObject <FlutterTextureRegistry, FlutterPluginRegistry>
 
 /**
  * Initializes an engine with the given viewController.

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

@@ -10,7 +10,6 @@
 
 #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/FlutterOpenGLRenderer.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
 #import "flutter/shell/platform/embedder/embedder.h"
 
@@ -38,11 +37,42 @@ @interface FlutterEngine () <FlutterBinaryMessenger>
  */
 - (void)sendUserLocales;
 
+/**
+ * Called by the engine to make the context the engine should draw into current.
+ */
+- (bool)engineCallbackOnMakeCurrent;
+
+/**
+ * Called by the engine to clear the context the engine should draw into.
+ */
+- (bool)engineCallbackOnClearCurrent;
+
+/**
+ * Called by the engine when the context's buffers should be swapped.
+ */
+- (bool)engineCallbackOnPresent;
+
+/**
+ * Called by the engine when framebuffer object ID is requested.
+ */
+- (uint32_t)engineCallbackOnFBO:(const FlutterFrameInfo*)info;
+
+/**
+ * Makes the resource context the current context.
+ */
+- (bool)engineCallbackOnMakeResourceCurrent;
+
 /**
  * Handles a platform message from the engine.
  */
 - (void)engineCallbackOnPlatformMessage:(const FlutterPlatformMessage*)message;
 
+/**
+ * Forwards texture copy request to the corresponding texture via |textureID|.
+ */
+- (BOOL)populateTextureWithIdentifier:(int64_t)textureID
+                        openGLTexture:(FlutterOpenGLTexture*)openGLTexture;
+
 /**
  * Requests that the task be posted back the to the Flutter engine at the target time. The target
  * time is in the clock used by the Flutter engine.
@@ -89,7 +119,7 @@ - (instancetype)initWithPlugin:(NSString*)pluginKey flutterEngine:(FlutterEngine
 }
 
 - (id<FlutterTextureRegistry>)textures {
-  return _flutterEngine.openGLRenderer;
+  return _flutterEngine;
 }
 
 - (NSView*)view {
@@ -108,10 +138,38 @@ - (void)addMethodCallDelegate:(nonnull id<FlutterPlugin>)delegate
 // Callbacks provided to the engine. See the called methods for documentation.
 #pragma mark - Static methods provided to engine configuration
 
+static bool OnMakeCurrent(FlutterEngine* engine) {
+  return [engine engineCallbackOnMakeCurrent];
+}
+
+static bool OnClearCurrent(FlutterEngine* engine) {
+  return [engine engineCallbackOnClearCurrent];
+}
+
+static bool OnPresent(FlutterEngine* engine) {
+  return [engine engineCallbackOnPresent];
+}
+
+static uint32_t OnFBO(FlutterEngine* engine, const FlutterFrameInfo* info) {
+  return [engine engineCallbackOnFBO:info];
+}
+
+static bool OnMakeResourceCurrent(FlutterEngine* engine) {
+  return [engine engineCallbackOnMakeResourceCurrent];
+}
+
 static void OnPlatformMessage(const FlutterPlatformMessage* message, FlutterEngine* engine) {
   [engine engineCallbackOnPlatformMessage:message];
 }
 
+static bool OnAcquireExternalTexture(FlutterEngine* engine,
+                                     int64_t texture_identifier,
+                                     size_t width,
+                                     size_t height,
+                                     FlutterOpenGLTexture* open_gl_texture) {
+  return [engine populateTextureWithIdentifier:texture_identifier openGLTexture:open_gl_texture];
+}
+
 #pragma mark -
 
 @implementation FlutterEngine {
@@ -121,12 +179,22 @@ @implementation FlutterEngine {
   // The project being run by this engine.
   FlutterDartProject* _project;
 
+  // The context provided to the Flutter engine for resource loading.
+  NSOpenGLContext* _resourceContext;
+
+  // The context that is owned by the currently displayed FlutterView. This is stashed in the engine
+  // so that the view doesn't need to be accessed from a background thread.
+  NSOpenGLContext* _mainOpenGLContext;
+
   // A mapping of channel names to the registered handlers for those channels.
   NSMutableDictionary<NSString*, FlutterBinaryMessageHandler>* _messageHandlers;
 
   // Whether the engine can continue running after the view controller is removed.
   BOOL _allowHeadlessExecution;
 
+  // A mapping of textureID to internal FlutterExternalTextureGL adapter.
+  NSMutableDictionary<NSNumber*, FlutterExternalTextureGL*>* _textures;
+
   // Pointer to the Dart AOT snapshot and instruction data.
   _FlutterEngineAOTData* _aotData;
 }
@@ -143,10 +211,10 @@ - (instancetype)initWithName:(NSString*)labelPrefix
 
   _project = project ?: [[FlutterDartProject alloc] init];
   _messageHandlers = [[NSMutableDictionary alloc] init];
+  _textures = [[NSMutableDictionary alloc] init];
   _allowHeadlessExecution = allowHeadlessExecution;
   _embedderAPI.struct_size = sizeof(FlutterEngineProcTable);
   FlutterEngineGetProcAddresses(&_embedderAPI);
-  _openGLRenderer = [[FlutterOpenGLRenderer alloc] initWithFlutterEngine:_engine];
 
   NSNotificationCenter* notificationCenter = [NSNotificationCenter defaultCenter];
   [notificationCenter addObserver:self
@@ -174,8 +242,17 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
     return NO;
   }
 
-  [_openGLRenderer attachToFlutterView:_viewController.flutterView];
-  const FlutterRendererConfig rendererConfig = [_openGLRenderer createRendererConfig];
+  const FlutterRendererConfig rendererConfig = {
+      .type = kOpenGL,
+      .open_gl.struct_size = sizeof(FlutterOpenGLRendererConfig),
+      .open_gl.make_current = (BoolCallback)OnMakeCurrent,
+      .open_gl.clear_current = (BoolCallback)OnClearCurrent,
+      .open_gl.present = (BoolCallback)OnPresent,
+      .open_gl.fbo_with_frame_info_callback = (UIntFrameInfoCallback)OnFBO,
+      .open_gl.fbo_reset_after_present = true,
+      .open_gl.make_resource_current = (BoolCallback)OnMakeResourceCurrent,
+      .open_gl.gl_external_texture_frame_callback = (TextureFrameCallback)OnAcquireExternalTexture,
+  };
 
   // TODO(stuartmorgan): Move internal channel registration from FlutterViewController to here.
 
@@ -274,6 +351,15 @@ - (void)loadAOTData:(NSString*)assetsDir {
   }
 }
 
+- (void)setViewController:(FlutterViewController*)controller {
+  _viewController = controller;
+  _mainOpenGLContext = controller.flutterView.openGLContext;
+  if (!controller && !_allowHeadlessExecution) {
+    [self shutDownEngine];
+    _resourceContext = nil;
+  }
+}
+
 - (id<FlutterBinaryMessenger>)binaryMessenger {
   // TODO(stuartmorgan): Switch to FlutterBinaryMessengerRelay to avoid plugins
   // keeping the engine alive.
@@ -286,6 +372,17 @@ - (BOOL)running {
   return _engine != nullptr;
 }
 
+- (NSOpenGLContext*)resourceContext {
+  if (!_resourceContext) {
+    NSOpenGLPixelFormatAttribute attributes[] = {
+        NSOpenGLPFAColorSize, 24, NSOpenGLPFAAlphaSize, 8, 0,
+    };
+    NSOpenGLPixelFormat* pixelFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attributes];
+    _resourceContext = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:nil];
+  }
+  return _resourceContext;
+}
+
 - (void)updateDisplayConfig {
   if (!_engine) {
     return;
@@ -364,6 +461,37 @@ - (void)sendUserLocales {
   _embedderAPI.UpdateLocales(_engine, flutterLocaleList.data(), flutterLocaleList.size());
 }
 
+- (bool)engineCallbackOnMakeCurrent {
+  if (!_mainOpenGLContext) {
+    return false;
+  }
+  [_mainOpenGLContext makeCurrentContext];
+  return true;
+}
+
+- (uint32_t)engineCallbackOnFBO:(const FlutterFrameInfo*)info {
+  CGSize size = CGSizeMake(info->size.width, info->size.height);
+  return [_viewController.flutterView frameBufferIDForSize:size];
+}
+
+- (bool)engineCallbackOnClearCurrent {
+  [NSOpenGLContext clearCurrentContext];
+  return true;
+}
+
+- (bool)engineCallbackOnPresent {
+  if (!_mainOpenGLContext) {
+    return false;
+  }
+  [self.viewController.flutterView present];
+  return true;
+}
+
+- (bool)engineCallbackOnMakeResourceCurrent {
+  [self.resourceContext makeCurrentContext];
+  return true;
+}
+
 - (void)engineCallbackOnPlatformMessage:(const FlutterPlatformMessage*)message {
   NSData* messageData = [NSData dataWithBytesNoCopy:(void*)message->message
                                              length:message->message_size
@@ -490,6 +618,31 @@ - (void)cleanupConnection:(FlutterBinaryMessengerConnection)connection {
   return [[FlutterEngineRegistrar alloc] initWithPlugin:pluginName flutterEngine:self];
 }
 
+#pragma mark - FlutterTextureRegistrar
+
+- (BOOL)populateTextureWithIdentifier:(int64_t)textureID
+                        openGLTexture:(FlutterOpenGLTexture*)openGLTexture {
+  return [_textures[@(textureID)] populateTexture:openGLTexture];
+}
+
+- (int64_t)registerTexture:(id<FlutterTexture>)texture {
+  FlutterExternalTextureGL* FlutterTexture =
+      [[FlutterExternalTextureGL alloc] initWithFlutterTexture:texture];
+  int64_t textureID = [FlutterTexture textureID];
+  _embedderAPI.RegisterExternalTexture(_engine, textureID);
+  _textures[@(textureID)] = FlutterTexture;
+  return textureID;
+}
+
+- (void)textureFrameAvailable:(int64_t)textureID {
+  _embedderAPI.MarkExternalTextureFrameAvailable(_engine, textureID);
+}
+
+- (void)unregisterTexture:(int64_t)textureID {
+  _embedderAPI.UnregisterExternalTexture(_engine, textureID);
+  [_textures removeObjectForKey:@(textureID)];
+}
+
 #pragma mark - Task runner integration
 
 - (void)postMainThreadTask:(FlutterTask)task targetTimeInNanoseconds:(uint64_t)targetTime {

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

@@ -6,7 +6,6 @@
 
 #import <Cocoa/Cocoa.h>
 
-#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 
 @interface FlutterEngine ()
@@ -17,10 +16,10 @@
 @property(nonatomic, readonly) BOOL running;
 
 /**
- * Provides the renderer config needed to initialize the engine and also handles external texture
- * management.
+ * The resource context used by the engine for texture uploads. FlutterViews associated with this
+ * engine should be created to share with this context.
  */
-@property(nonatomic, readonly, nonnull) FlutterOpenGLRenderer* openGLRenderer;
+@property(nonatomic, readonly, nullable) NSOpenGLContext* resourceContext;
 
 /**
  * Function pointers for interacting with the embedder.h API.