[macOS] Remove OpenGL rendering backend

In flutter/buildroot#648 (rolled to the engine in flutter#37380)
the minimum macOS SDK was bumped from 10.13 to 10.14. As of macOS 10.14,
Metal is available for all users. This eliminates the macOS OpenGL
rendering support code.

Note that this only removes the GL-specific code in the embedder. A
followup patch will land refactorings to clean up the remaining code,
for example, cases where a parent interface exists only because we had
both a GL and a Metal implementation. This is being does in two patches
in order to keep review clear and simple and to simplify rebases of any
outstanding patches that also touches this code.

Issue: flutter/flutter#114445

ci/licenses_golden/licenses_flutter

@@ -2588,8 +2588,6 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/Accessibilit
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterAppDelegate.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterBackingStore.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterBackingStore.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/FlutterChannelKeyResponder.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponder.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterChannelKeyResponderUnittests.mm
@@ -2606,16 +2604,8 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterEngin
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterEngineTestUtils.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterEngineTestUtils.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureGL.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureGL.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureMetal.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterExternalTextureMetal.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/FlutterFrameBufferProviderUnittests.mm
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterGLCompositor.mm
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterGLCompositorUnittests.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/FlutterKeyPrimaryResponder.h
@@ -2637,18 +2627,13 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMetal
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterMetalSurfaceManagerTest.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/FlutterOpenGLRendererTest.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMac.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMac.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformNodeDelegateMacTest.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewControllerTest.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterRenderingBackend.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterRenderingBackend.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizableBackingStoreProvider.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizableBackingStoreProvider.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.h
@@ -2676,8 +2661,6 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewE
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterViewProvider.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/KeyCodeMap.g.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/KeyCodeMap_Internal.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/MacOSGLContextSwitch.h
-FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/MacOSGLContextSwitch.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/TestFlutterPlatformView.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/TestFlutterPlatformView.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/module.modulemap

shell/platform/darwin/macos/BUILD.gn

@@ -59,8 +59,6 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterAppDelegate.mm",
     "framework/Source/FlutterBackingStore.h",
     "framework/Source/FlutterBackingStore.mm",
-    "framework/Source/FlutterBackingStoreData.h",
-    "framework/Source/FlutterBackingStoreData.mm",
     "framework/Source/FlutterChannelKeyResponder.h",
     "framework/Source/FlutterChannelKeyResponder.mm",
     "framework/Source/FlutterCompositor.h",
@@ -71,14 +69,8 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterEmbedderKeyResponder.mm",
     "framework/Source/FlutterEngine.mm",
     "framework/Source/FlutterEngine_Internal.h",
-    "framework/Source/FlutterExternalTextureGL.h",
-    "framework/Source/FlutterExternalTextureGL.mm",
     "framework/Source/FlutterExternalTextureMetal.h",
     "framework/Source/FlutterExternalTextureMetal.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/FlutterKeyPrimaryResponder.h",
@@ -96,15 +88,11 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterMetalRenderer.mm",
     "framework/Source/FlutterMouseCursorPlugin.h",
     "framework/Source/FlutterMouseCursorPlugin.mm",
-    "framework/Source/FlutterOpenGLRenderer.h",
-    "framework/Source/FlutterOpenGLRenderer.mm",
     "framework/Source/FlutterPlatformNodeDelegateMac.h",
     "framework/Source/FlutterPlatformNodeDelegateMac.mm",
     "framework/Source/FlutterPlatformViewController.h",
     "framework/Source/FlutterPlatformViewController.mm",
     "framework/Source/FlutterRenderer.h",
-    "framework/Source/FlutterRenderingBackend.h",
-    "framework/Source/FlutterRenderingBackend.mm",
     "framework/Source/FlutterResizableBackingStoreProvider.h",
     "framework/Source/FlutterResizableBackingStoreProvider.mm",
     "framework/Source/FlutterResizeSynchronizer.h",
@@ -125,8 +113,6 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterViewEngineProvider.mm",
     "framework/Source/FlutterViewProvider.h",
     "framework/Source/KeyCodeMap.g.mm",
-    "framework/Source/MacOSGLContextSwitch.h",
-    "framework/Source/MacOSGLContextSwitch.mm",
   ]
 
   sources += _flutter_framework_headers
@@ -190,14 +176,11 @@ executable("flutter_desktop_darwin_unittests") {
     "framework/Source/FlutterEngineTest.mm",
     "framework/Source/FlutterEngineTestUtils.h",
     "framework/Source/FlutterEngineTestUtils.mm",
-    "framework/Source/FlutterFrameBufferProviderUnittests.mm",
-    "framework/Source/FlutterGLCompositorUnittests.mm",
     "framework/Source/FlutterKeyboardManagerUnittests.mm",
     "framework/Source/FlutterMenuPluginTest.mm",
     "framework/Source/FlutterMetalCompositorUnittests.mm",
     "framework/Source/FlutterMetalRendererTest.mm",
     "framework/Source/FlutterMetalSurfaceManagerTest.mm",
-    "framework/Source/FlutterOpenGLRendererTest.mm",
     "framework/Source/FlutterPlatformNodeDelegateMacTest.mm",
     "framework/Source/FlutterPlatformViewControllerTest.mm",
     "framework/Source/FlutterTextInputPluginTest.mm",

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

@@ -13,23 +13,6 @@
 
 @end
 
-/**
- * Wraps an OpenGL frame buffer.
- */
-@interface FlutterOpenGLRenderBackingStore : FlutterRenderBackingStore
-
-/**
- * Frame buffer ID referenced by this backing store instance.
- */
-@property(nonatomic, readonly) uint32_t frameBufferID;
-
-/**
- * Initializes a backing store with the specified frame buffer id.
- */
-- (nonnull instancetype)initWithFrameBufferID:(uint32_t)fboID;
-
-@end
-
 /**
  * Wraps a Metal texture.
  */

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

@@ -7,18 +7,6 @@
 @implementation FlutterRenderBackingStore
 @end
 
-@implementation FlutterOpenGLRenderBackingStore
-
-- (instancetype)initWithFrameBufferID:(uint32_t)fboID {
-  self = [super init];
-  if (self) {
-    _frameBufferID = fboID;
-  }
-  return self;
-}
-
-@end
-
 @implementation FlutterMetalRenderBackingStore
 
 - (instancetype)initWithTexture:(id<MTLTexture>)texture {

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

@@ -10,15 +10,11 @@
 #include <vector>
 
 #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/FlutterGLCompositor.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMenuPlugin.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMetalCompositor.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMetalRenderer.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h"
-#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterOpenGLRenderer.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.h"
-#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterRenderingBackend.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewEngineProvider.h"
 #include "flutter/shell/platform/embedder/embedder.h"
@@ -251,11 +247,7 @@ - (instancetype)initWithName:(NSString*)labelPrefix
   _embedderAPI.struct_size = sizeof(FlutterEngineProcTable);
   FlutterEngineGetProcAddresses(&_embedderAPI);
 
-  if ([FlutterRenderingBackend renderUsingMetal]) {
-    _renderer = [[FlutterMetalRenderer alloc] initWithFlutterEngine:self];
-  } else {
-    _renderer = [[FlutterOpenGLRenderer alloc] initWithFlutterEngine:self];
-  }
+  _renderer = [[FlutterMetalRenderer alloc] initWithFlutterEngine:self];
 
   NSNotificationCenter* notificationCenter = [NSNotificationCenter defaultCenter];
   [notificationCenter addObserver:self
@@ -436,16 +428,9 @@ - (FlutterCompositor*)createFlutterCompositor {
 
   __weak FlutterEngine* weakSelf = self;
 
-  if ([FlutterRenderingBackend renderUsingMetal]) {
-    FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(_renderer);
-    _macOSCompositor = std::make_unique<flutter::FlutterMetalCompositor>(
-        _viewProvider, _platformViewController, metalRenderer.device);
-  } else {
-    FlutterOpenGLRenderer* openGLRenderer = reinterpret_cast<FlutterOpenGLRenderer*>(_renderer);
-    [openGLRenderer.openGLContext makeCurrentContext];
-    _macOSCompositor =
-        std::make_unique<flutter::FlutterGLCompositor>(_viewProvider, openGLRenderer.openGLContext);
-  }
+  FlutterMetalRenderer* metalRenderer = reinterpret_cast<FlutterMetalRenderer*>(_renderer);
+  _macOSCompositor = std::make_unique<flutter::FlutterMetalCompositor>(
+      _viewProvider, _platformViewController, metalRenderer.device);
   _macOSCompositor->SetPresentCallback([weakSelf](bool has_flutter_content) {
     if (has_flutter_content) {
       return [weakSelf.renderer present] == YES;

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

@@ -23,8 +23,7 @@
 
 @interface FlutterEngine (Test)
 /**
- * The FlutterCompositor object currently in use by the FlutterEngine. This is
- * either a FlutterOpenGLCompositor or a FlutterMetalCompositor.
+ * The FlutterCompositor object currently in use by the FlutterEngine.
  *
  * May be nil if the compositor has not been initialized yet.
  */