[macOS] Add FLETexture and FLETextureRegistrar.

library/macos/FLEExternalTexture.h

@@ -0,0 +1,46 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+#import <FlutterEmbedder/FlutterEmbedder.h>
+
+#import "FLETexture.h"
+
+/**
+ * Used to bridge external FLETexture objects,
+ * so the implementer only needs to return the CVPixelBufferRef object,
+ * which will make the interface consistent with the FlutterTexture.
+ */
+@interface FLEExternalTexture : NSObject
+
+/**
+ *
+ */
+- (nonnull instancetype)initWithExternalTexture:(nonnull id<FLETexture>)external_texture;
+
+/**
+ * Accept texture rendering notifications from the flutter engine.
+ */
+- (BOOL)populateTextureWidth:(size_t)width
+                      height:(size_t)height
+                     texture:(FlutterOpenGLTexture *)texture;
+
+/**
+ *
+ */
+- (int64_t)textureId;
+
+@property(nullable, weak) id<FLETexture> external_texture;
+
+@end

library/macos/FLEExternalTexture.m

@@ -0,0 +1,96 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "FLEExternalTexture.h"
+
+#import <AppKit/NSOpenGL.h>
+#import <CoreVideo/CVOpenGLBuffer.h>
+#import <CoreVideo/CVOpenGLTextureCache.h>
+#import <OpenGL/gl.h>
+
+@implementation FLEExternalTexture {
+  CVOpenGLTextureCacheRef _textureCache;
+  CVPixelBufferRef _pixelBuffer;
+}
+
+@synthesize external_texture;
+
+- (instancetype)initWithExternalTexture:(id<FLETexture>)external_texture {
+  self = [super init];
+
+  if (self) {
+    self.external_texture = external_texture;
+  }
+
+  return self;
+}
+
+static void OnGLTextureRelease(CVPixelBufferRef pixelBuffer) {
+  CVPixelBufferRelease(pixelBuffer);
+}
+
+- (int64_t)textureId {
+  return (NSInteger)(self);
+}
+
+- (BOOL)populateTextureWidth:(size_t)width
+           height:(size_t)height
+          texture:(FlutterOpenGLTexture *)texture {
+
+  if(external_texture == NULL) {
+    return NO;
+  }
+
+  // Copy image buffer from external texture.
+  _pixelBuffer = [external_texture copyPixelBuffer];
+
+  if(_pixelBuffer == NULL) {
+    return NO;
+  }
+
+  // Create the texture cache if necessary.
+  if (_textureCache == NULL) {
+    CGLContextObj context = [NSOpenGLContext currentContext].CGLContextObj;
+    CGLPixelFormatObj format = CGLGetPixelFormat(context);
+    if (CVOpenGLTextureCacheCreate(kCFAllocatorDefault, NULL, context, format, NULL, &_textureCache) != kCVReturnSuccess) {
+      NSLog(@"Could not create texture cache.");
+      CVPixelBufferRelease(_pixelBuffer);
+      return NO;
+    }
+  }
+
+  // Try to clear the cache of OpenGL textures to save memory.
+  CVOpenGLTextureCacheFlush(_textureCache, 0);
+
+  CVOpenGLTextureRef openGLTexture = NULL;
+  if (CVOpenGLTextureCacheCreateTextureFromImage(kCFAllocatorDefault, _textureCache, _pixelBuffer, NULL, &openGLTexture) != kCVReturnSuccess) {
+    CVPixelBufferRelease(_pixelBuffer);
+    return NO;
+  }
+
+  texture->target = CVOpenGLTextureGetTarget(openGLTexture);
+  texture->name = CVOpenGLTextureGetName(openGLTexture);
+  texture->format = GL_RGBA8;
+  texture->destruction_callback = (VoidCallback)&OnGLTextureRelease;
+  texture->user_data = openGLTexture;
+
+  CVPixelBufferRelease(_pixelBuffer);
+  return YES;
+}
+
+- (void)dealloc {
+  CVOpenGLTextureCacheRelease(_textureCache);
+}
+
+@end

library/macos/FLEPluginRegistrar.h

@@ -16,6 +16,7 @@
 
 #import "FLEBinaryMessenger.h"
 #import "FLEMethodChannel.h"
+#import "FLETexture.h"
 
 /**
  * The protocol for an object managing registration for a plugin. It provides access to application
@@ -31,6 +32,11 @@
  */
 @property(nonnull, readonly) id<FLEBinaryMessenger> messenger;
 
+/**
+ * Returns a `FLETextureRegistry` for registering textures provided by the plugin.
+ */
+@property(nonnull, readonly) id<FLETextureRegistrar> textures;
+
 /**
  * The view displaying Flutter content.
  *

library/macos/FLETexture.h

@@ -0,0 +1,52 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import <Foundation/Foundation.h>
+#import <CoreVideo/CVPixelBuffer.h>
+
+/**
+ * Implement a texture object for the FLE plugin side.
+ */
+@protocol FLETexture<NSObject>
+
+/**
+ * When the texture on the platform side is ready,
+ * the flutter engine will copy the texture buffer
+ * using copyPixelBuffer.
+ */
+- (nullable CVPixelBufferRef)copyPixelBuffer;
+
+@end
+
+/**
+ * The protocol for an object managing registration for texture.
+ */
+@protocol FLETextureRegistrar<NSObject>
+
+/**
+ * Register a |texture| object and return a textureId.
+ */
+- (int64_t)registerTexture:(nonnull id<FLETexture>)texture;
+
+/**
+ * Mark a texture buffer is ready.
+ */
+- (void)textureFrameAvailable:(int64_t)textureId;
+
+/**
+ * Unregister an existing Texture object.
+ */
+- (void)unregisterTexture:(int64_t)textureId;
+
+@end

library/macos/FLEViewController.h

@@ -20,6 +20,7 @@
 #import "FLEPlugin.h"
 #import "FLEPluginRegistrar.h"
 #import "FLEReshapeListener.h"
+#import "FLETexture.h"
 
 /**
  * Controls embedder plugins and communication with the underlying Flutter engine, managing a view
@@ -29,7 +30,7 @@
  * Flutter engine in non-interactive mode, or with a drawable Flutter canvas.
  */
 @interface FLEViewController
-    : NSViewController <FLEBinaryMessenger, FLEPluginRegistrar, FLEReshapeListener>
+    : NSViewController <FLEBinaryMessenger, FLEPluginRegistrar, FLEReshapeListener, FLETextureRegistrar>
 
 /**
  * The view this controller manages when launched in interactive mode (headless set to false). Must

library/macos/FLEViewController.mm

@@ -22,6 +22,7 @@
 #import "FLEReshapeListener.h"
 #import "FLETextInputPlugin.h"
 #import "FLEView.h"
+#import "FLEExternalTexture.h"
 
 static NSString *const kXcodeExtraArgumentOne = @"-NSDocumentRevisionsDebugMode";
 static NSString *const kXcodeExtraArgumentTwo = @"YES";
@@ -95,6 +96,10 @@ - (void)dispatchMouseEvent:(nonnull NSEvent *)event phase:(FlutterPointerPhase)p
  */
 - (void)dispatchKeyEvent:(NSEvent *)event ofType:(NSString *)type;
 
+-(BOOL) populateTextureWithIdentifier:(int64_t)texture_identifier
+                                width:(size_t)width
+                               height:(size_t)height
+                              texture:(FlutterOpenGLTexture *)texture;
 @end
 
 #pragma mark - Static methods provided to engine configuration
@@ -144,6 +149,14 @@ static bool OnMakeResourceCurrent(FLEViewController *controller) {
   return true;
 }
 
+static bool OnAcquireExternalTexture(FLEViewController *controller,
+                                     int64_t texture_identifier,
+                                     size_t width,
+                                     size_t height,
+                                     FlutterOpenGLTexture *texture) {
+  return [controller populateTextureWithIdentifier:texture_identifier width:width height:height texture:texture];
+}
+
 #pragma mark Static methods provided for headless engine configuration
 
 static bool HeadlessOnMakeCurrent(FLEViewController *controller) { return false; }
@@ -173,6 +186,9 @@ @implementation FLEViewController {
   // A message channel for passing key events to the Flutter engine. This should be replaced with
   // an embedding API; see Issue #47.
   FLEBasicMessageChannel *_keyEventChannel;
+
+  // A mapping of external textures.
+  NSMutableDictionary<NSNumber *, FLEExternalTexture *> *_textures;
 }
 
 @dynamic view;
@@ -183,6 +199,7 @@ @implementation FLEViewController {
 static void CommonInit(FLEViewController *controller) {
   controller->_messageHandlers = [[NSMutableDictionary alloc] init];
   controller->_additionalKeyResponders = [[NSMutableOrderedSet alloc] init];
+  controller->_textures = [[NSMutableDictionary alloc] init];
 }
 
 - (instancetype)initWithCoder:(NSCoder *)coder {
@@ -327,7 +344,8 @@ + (FlutterRendererConfig)createRenderConfigHeadless:(BOOL)headless {
         .open_gl.clear_current = (BoolCallback)OnClearCurrent,
         .open_gl.present = (BoolCallback)OnPresent,
         .open_gl.fbo_callback = (UIntCallback)OnFBO,
-        .open_gl.make_resource_current = (BoolCallback)OnMakeResourceCurrent};
+        .open_gl.make_resource_current = (BoolCallback)OnMakeResourceCurrent,
+        .open_gl.gl_external_texture_frame_callback = (TextureFrameCallback)OnAcquireExternalTexture};
     return config;
   }
 }
@@ -342,6 +360,30 @@ - (void)makeResourceContextCurrent {
   [_resourceContext makeCurrentContext];
 }
 
+- (BOOL)populateTextureWithIdentifier:(int64_t)textureId
+                                width:(size_t)width
+                               height:(size_t) height
+                              texture:(FlutterOpenGLTexture *)texture {
+  return [_textures[@(textureId)] populateTextureWidth:width height:height texture:texture];
+}
+
+- (int64_t)registerTexture:(id<FLETexture>)texture {
+  FLEExternalTexture *fleTexture = [[FLEExternalTexture alloc] initWithExternalTexture:texture];
+  int64_t textureId = [fleTexture textureId];
+  FlutterEngineRegisterExternalTexture(_engine, textureId);
+  _textures[@(textureId)] = fleTexture;
+  return textureId;
+}
+
+- (void)textureFrameAvailable:(int64_t)textureId {
+  FlutterEngineMarkExternalTextureFrameAvailable(_engine, textureId);
+}
+
+- (void)unregisterTexture:(int64_t)textureId {
+  FlutterEngineUnregisterExternalTexture(_engine, textureId);
+  [_textures removeObjectForKey:@(textureId)];
+}
+
 - (void)handlePlatformMessage:(const FlutterPlatformMessage *)message {
   NSData *messageData = [NSData dataWithBytesNoCopy:(void *)message->message
                                              length:message->message_size
@@ -440,6 +482,10 @@ - (void)setMessageHandlerOnChannel:(nonnull NSString *)channel
   return self;
 }
 
+- (id<FLETextureRegistrar>)textures {
+    return self;
+}
+
 - (void)addMethodCallDelegate:(nonnull id<FLEPlugin>)delegate
                       channel:(nonnull FLEMethodChannel *)channel {
   [channel setMethodCallHandler:^(FLEMethodCall *call, FLEMethodResult result) {

library/macos/FlutterEmbedderMac.h

@@ -26,5 +26,6 @@
 #import "FLEPlugin.h"
 #import "FLEPluginRegistrar.h"
 #import "FLEReshapeListener.h"
+#import "FLETexture.h"
 #import "FLEView.h"
 #import "FLEViewController.h"