[macOS] Merge FlutterSurfaceManager and impls

Previously, FlutterSurfaceManager was a protocol with two concrete
implementations: FlutterGLSurfaceManager and FlutterMetalSurfaceManager.
Most of the implementation was in a shared superclass,
FlutterIOSurfaceManager, which called into the OpenGL or Metal-specific
subclass when backend-specific operations (such as allocating textures)
was required. It did so via a delegate pattern, wherein the subclasses
both implemented the FlutterIOSurfaceManagerDelegate protocol that
exposed the backend-specific functionality.

Now that only the Metal implementation remains, the delegate code can be
inlined into the calling functions, and the class hierarchy can be
squashed into a single concrete implementation class,
FlutterSurfaceManager, similar to how it was originally implemented in
flutter#21525 before we had two backends.

Issue: flutter/flutter#108304
Issue: flutter/flutter#114445

ci/licenses_golden/licenses_flutter

@@ -2641,6 +2641,7 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResiz
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterSurfaceManager.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterSurfaceManager.mm
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterSurfaceManagerTest.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTextInputPlugin.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTextInputPlugin.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTextInputPluginTest.mm

shell/platform/darwin/macos/BUILD.gn

@@ -178,9 +178,9 @@ executable("flutter_desktop_darwin_unittests") {
     "framework/Source/FlutterKeyboardManagerUnittests.mm",
     "framework/Source/FlutterMenuPluginTest.mm",
     "framework/Source/FlutterMetalRendererTest.mm",
-    "framework/Source/FlutterMetalSurfaceManagerTest.mm",
     "framework/Source/FlutterPlatformNodeDelegateMacTest.mm",
     "framework/Source/FlutterPlatformViewControllerTest.mm",
+    "framework/Source/FlutterSurfaceManagerTest.mm",
     "framework/Source/FlutterTextInputPluginTest.mm",
     "framework/Source/FlutterTextInputSemanticsObjectTest.mm",
     "framework/Source/FlutterViewControllerTest.mm",

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

@@ -11,7 +11,7 @@
 @implementation FlutterMetalResizableBackingStoreProvider {
   id<MTLDevice> _device;
   id<MTLCommandQueue> _commandQueue;
-  id<FlutterSurfaceManager> _surfaceManager;
+  FlutterSurfaceManager* _surfaceManager;
 }
 
 - (instancetype)initWithDevice:(id<MTLDevice>)device
@@ -21,9 +21,9 @@ - (instancetype)initWithDevice:(id<MTLDevice>)device
   if (self) {
     _device = device;
     _commandQueue = commandQueue;
-    _surfaceManager = [[FlutterMetalSurfaceManager alloc] initWithDevice:device
-                                                            commandQueue:commandQueue
-                                                                   layer:layer];
+    _surfaceManager = [[FlutterSurfaceManager alloc] initWithDevice:device
+                                                       commandQueue:commandQueue
+                                                              layer:layer];
   }
   return self;
 }

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

@@ -9,88 +9,36 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterIOSurfaceHolder.h"
 
 /**
- * Manages the render surfaces and their corresponding backing stores.
- */
-@protocol FlutterSurfaceManager
-
-/**
- * Updates the backing store size of the managed IOSurfaces to `size`. If the surfaces are already
- * of the same size, this is a no-op.
- */
-- (void)ensureSurfaceSize:(CGSize)size;
-
-/**
- * Swaps the front and the back buffer.
- */
-- (void)swapBuffers;
-
-/**
- * Returns the backing store for the back buffer.
- */
-- (nonnull FlutterRenderBackingStore*)renderBuffer;
-
-@end
-
-/**
- * Methods for managing the IOSurfaces held by FlutterIOSurfaceManager.
- */
-@protocol FlutterIOSurfaceManagerDelegate
-
-/**
- * Tells the delegate that the front and back IOSurfaces are swapped.
- */
-- (void)onSwapBuffers;
-
-/**
- * Tells the delegate that the IOSurfaces have been resized. `bufferIndex` is to indicate the front
- * vs back buffer. `size` is the new size of the IOSurface.
- */
-- (void)onUpdateSurface:(nonnull FlutterIOSurfaceHolder*)surface
-            bufferIndex:(size_t)index
-                   size:(CGSize)size;
-
-/**
- * Tells the delegate that IOSurface with given index has been released. Delegate should free
- * all resources associated with the surface
- */
-- (void)onSurfaceReleased:(size_t)index;
-
-@end
-
-/**
- * Manages IOSurfaces for the FlutterEngine to render to.
+ * Manages render surfaces and corresponding backing stores used by the engine.
  *
- * The backing store when rendering with on Metal its a Metal texture. There are two IOSurfaces
+ * The backing store when rendering with on Metal is a Metal texture. There are two IOSurfaces
  * created during initialization, FlutterSurfaceManager manages the lifecycle of these.
  */
-@interface FlutterIOSurfaceManager : NSObject <FlutterSurfaceManager>
-
-/**
- * The object that acts as the delegate for the FlutterIOSurfaceManager. See:
- * FlutterIOSurfaceManagerDelegate.
- */
-@property(nullable, nonatomic, weak) id<FlutterIOSurfaceManagerDelegate> delegate;
+@interface FlutterSurfaceManager : NSObject
 
 /**
- * Initializes and returns an IOSurface manager that renders to a child layer (referred to as the
+ * Initializes and returns a surface manager that renders to a child layer (referred to as the
  * content layer) of the containing layer and applies the transform to the contents of the content
  * layer.
  */
-- (nullable instancetype)initWithLayer:(nonnull CALayer*)containingLayer
-                      contentTransform:(CATransform3D)transform;
+- (nullable instancetype)initWithDevice:(nonnull id<MTLDevice>)device
+                           commandQueue:(nonnull id<MTLCommandQueue>)commandQueue
+                                  layer:(nonnull CALayer*)containingLayer;
 
-@end
+/**
+ * Updates the backing store size of the managed IOSurfaces the specified size. If the surfaces are
+ * already of this size, this is a no-op.
+ */
+- (void)ensureSurfaceSize:(CGSize)size;
 
 /**
- * FlutterSurfaceManager implementation where the IOSurfaces managed are backed by a Metal textures.
+ * Swaps the front and the back buffer.
  */
-@interface FlutterMetalSurfaceManager : FlutterIOSurfaceManager <FlutterIOSurfaceManagerDelegate>
+- (void)swapBuffers;
 
 /**
- * Creates two IOSurfaces backed by Metal textures.
+ * Returns the backing store for the back buffer.
  */
-- (nullable instancetype)initWithDevice:(nonnull id<MTLDevice>)device
-                           commandQueue:(nonnull id<MTLCommandQueue>)commandQueue
-                                  layer:(nonnull CALayer*)containingLayer;
+- (nonnull FlutterRenderBackingStore*)renderBuffer;
 
 @end

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

@@ -19,26 +19,49 @@
 // BackBuffer will be released after kIdleDelay if there is no activity.
 static const double kIdleDelay = 1.0;
 
-@implementation FlutterIOSurfaceManager {
+@interface FlutterSurfaceManager ()
+
+/**
+ * Cancels any previously-scheduled onIdle requests.
+ */
+- (void)cancelIdle;
+
+/**
+ * Creates a backing textures for the specified surface with the specified size.
+ */
+- (id<MTLTexture>)createTextureForSurface:(FlutterIOSurfaceHolder*)surface size:(CGSize)size;
+
+@end
+
+@implementation FlutterSurfaceManager {
   CALayer* _containingLayer;  // provided (parent layer)
   CALayer* _contentLayer;
   CATransform3D _contentTransform;
 
   CGSize _surfaceSize;
   FlutterIOSurfaceHolder* _ioSurfaces[kFlutterSurfaceManagerBufferCount];
   BOOL _frameInProgress;
+
+  id<MTLDevice> _device;
+  id<MTLCommandQueue> _commandQueue;
+  id<MTLTexture> _textures[kFlutterSurfaceManagerBufferCount];
 }
 
-- (instancetype)initWithLayer:(CALayer*)containingLayer contentTransform:(CATransform3D)transform {
+- (nullable instancetype)initWithDevice:(nonnull id<MTLDevice>)device
+                           commandQueue:(nonnull id<MTLCommandQueue>)commandQueue
+                                  layer:(nonnull CALayer*)containingLayer {
   self = [super init];
   if (self) {
     _containingLayer = containingLayer;
-    _contentTransform = transform;
+    _contentTransform = CATransform3DIdentity;
     _contentLayer = [[CALayer alloc] init];
     [_containingLayer addSublayer:_contentLayer];
 
     _ioSurfaces[0] = [[FlutterIOSurfaceHolder alloc] init];
     _ioSurfaces[1] = [[FlutterIOSurfaceHolder alloc] init];
+
+    _device = device;
+    _commandQueue = commandQueue;
   }
   return self;
 }
@@ -51,7 +74,7 @@ - (void)ensureSurfaceSize:(CGSize)size {
   for (int i = 0; i < kFlutterSurfaceManagerBufferCount; ++i) {
     if (_ioSurfaces[i] != nil) {
       [_ioSurfaces[i] recreateIOSurfaceWithSize:size];
-      [_delegate onUpdateSurface:_ioSurfaces[i] bufferIndex:i size:size];
+      _textures[i] = [self createTextureForSurface:_ioSurfaces[i] size:size];
     }
   }
 }
@@ -71,7 +94,8 @@ - (void)swapBuffers {
 
   std::swap(_ioSurfaces[kFlutterSurfaceManagerBackBuffer],
             _ioSurfaces[kFlutterSurfaceManagerFrontBuffer]);
-  [_delegate onSwapBuffers];
+  std::swap(_textures[kFlutterSurfaceManagerBackBuffer],
+            _textures[kFlutterSurfaceManagerFrontBuffer]);
 
   // performSelector:withObject:afterDelay needs to be performed on RunLoop thread
   [self performSelectorOnMainThread:@selector(reschedule) withObject:nil waitUntilDone:NO];
@@ -92,7 +116,7 @@ - (void)onIdle {
       // Release the back buffer and notify delegate. The buffer will be restored
       // on demand in ensureBackBuffer
       _ioSurfaces[kFlutterSurfaceManagerBackBuffer] = nil;
-      [self.delegate onSurfaceReleased:kFlutterSurfaceManagerBackBuffer];
+      _textures[kFlutterSurfaceManagerBackBuffer] = nil;
     }
   }
 }
@@ -104,9 +128,9 @@ - (void)ensureBackBuffer {
       // Restore previously released backbuffer
       _ioSurfaces[kFlutterSurfaceManagerBackBuffer] = [[FlutterIOSurfaceHolder alloc] init];
       [_ioSurfaces[kFlutterSurfaceManagerBackBuffer] recreateIOSurfaceWithSize:_surfaceSize];
-      [_delegate onUpdateSurface:_ioSurfaces[kFlutterSurfaceManagerBackBuffer]
-                     bufferIndex:kFlutterSurfaceManagerBackBuffer
-                            size:_surfaceSize];
+      _textures[kFlutterSurfaceManagerBackBuffer] =
+          [self createTextureForSurface:_ioSurfaces[kFlutterSurfaceManagerBackBuffer]
+                                   size:_surfaceSize];
     }
   };
   [self performSelectorOnMainThread:@selector(cancelIdle) withObject:nil waitUntilDone:NO];
@@ -117,47 +141,12 @@ - (void)cancelIdle {
 }
 
 - (nonnull FlutterRenderBackingStore*)renderBuffer {
-  @throw([NSException exceptionWithName:@"Sub-classes FlutterIOSurfaceManager of"
-                                         " must override renderBuffer."
-                                 reason:nil
-                               userInfo:nil]);
-}
-
-@end
-
-@implementation FlutterMetalSurfaceManager {
-  id<MTLDevice> _device;
-  id<MTLCommandQueue> _commandQueue;
-
-  id<MTLTexture> _textures[kFlutterSurfaceManagerBufferCount];
-}
-
-- (nullable instancetype)initWithDevice:(nonnull id<MTLDevice>)device
-                           commandQueue:(nonnull id<MTLCommandQueue>)commandQueue
-                                  layer:(nonnull CALayer*)containingLayer {
-  self = [super initWithLayer:containingLayer contentTransform:CATransform3DIdentity];
-  if (self) {
-    super.delegate = self;
-    _device = device;
-    _commandQueue = commandQueue;
-  }
-  return self;
-}
-
-- (FlutterRenderBackingStore*)renderBuffer {
   [self ensureBackBuffer];
   id<MTLTexture> texture = _textures[kFlutterSurfaceManagerBackBuffer];
   return [[FlutterMetalRenderBackingStore alloc] initWithTexture:texture];
 }
 
-- (void)onSwapBuffers {
-  std::swap(_textures[kFlutterSurfaceManagerBackBuffer],
-            _textures[kFlutterSurfaceManagerFrontBuffer]);
-}
-
-- (void)onUpdateSurface:(FlutterIOSurfaceHolder*)surface
-            bufferIndex:(size_t)index
-                   size:(CGSize)size {
+- (id<MTLTexture>)createTextureForSurface:(FlutterIOSurfaceHolder*)surface size:(CGSize)size {
   MTLTextureDescriptor* textureDescriptor =
       [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:MTLPixelFormatBGRA8Unorm
                                                          width:size.width
@@ -166,13 +155,7 @@ - (void)onUpdateSurface:(FlutterIOSurfaceHolder*)surface
   textureDescriptor.usage =
       MTLTextureUsageShaderRead | MTLTextureUsageRenderTarget | MTLTextureUsageShaderWrite;
   // plane = 0 for BGRA.
-  _textures[index] = [_device newTextureWithDescriptor:textureDescriptor
-                                             iosurface:[surface ioSurface]
-                                                 plane:0];
-}
-
-- (void)onSurfaceReleased:(size_t)index {
-  _textures[index] = nil;
+  return [_device newTextureWithDescriptor:textureDescriptor iosurface:[surface ioSurface] plane:0];
 }
 
 @end

shell/platform/darwin/macos/framework/Source/FlutterMetalSurfaceManagerTest.mm → shell/platform/darwin/macos/framework/Source/FlutterSurfaceManagerTest.mm

@@ -29,18 +29,18 @@ - (instancetype)init {
 
 namespace flutter::testing {
 
-static FlutterMetalSurfaceManager* CreateSurfaceManager() {
+static FlutterSurfaceManager* CreateSurfaceManager() {
   id<MTLDevice> device = MTLCreateSystemDefaultDevice();
   id<MTLCommandQueue> commandQueue = [device newCommandQueue];
   TestMetalView* metalView = [[TestMetalView alloc] init];
   CALayer* layer = reinterpret_cast<CALayer*>(metalView.layer);
-  return [[FlutterMetalSurfaceManager alloc] initWithDevice:device
-                                               commandQueue:commandQueue
-                                                      layer:layer];
+  return [[FlutterSurfaceManager alloc] initWithDevice:device
+                                          commandQueue:commandQueue
+                                                 layer:layer];
 }
 
-TEST(FlutterMetalSurfaceManager, EnsureSizeUpdatesSize) {
-  FlutterMetalSurfaceManager* surfaceManager = CreateSurfaceManager();
+TEST(FlutterSurfaceManager, EnsureSizeUpdatesSize) {
+  FlutterSurfaceManager* surfaceManager = CreateSurfaceManager();
   CGSize size = CGSizeMake(100, 50);
   [surfaceManager ensureSurfaceSize:size];
   id<MTLTexture> texture =
@@ -49,8 +49,8 @@ - (instancetype)init {
   ASSERT_TRUE(CGSizeEqualToSize(size, textureSize));
 }
 
-TEST(FlutterMetalSurfaceManager, EnsureSizeUpdatesSizeForBackBuffer) {
-  FlutterMetalSurfaceManager* surfaceManager = CreateSurfaceManager();
+TEST(FlutterSurfaceManager, EnsureSizeUpdatesSizeForBackBuffer) {
+  FlutterSurfaceManager* surfaceManager = CreateSurfaceManager();
   CGSize size = CGSizeMake(100, 50);
   [surfaceManager ensureSurfaceSize:size];
   [surfaceManager renderBuffer];  // make sure we have back buffer