MacOS: Add metal renderer and view.

webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLNSVideoView.m

+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import "WebRTC/RTCMTLNSVideoView.h"
+
+#import <Metal/Metal.h>
+#import <MetalKit/MetalKit.h>
+
+#import "WebRTC/RTCVideoFrame.h"
+
+#import "RTCMTLI420Renderer.h"
+
+@interface RTCMTLNSVideoView () <MTKViewDelegate>
+@property(nonatomic) id<RTCMTLRenderer> renderer;
+@property(nonatomic, strong) MTKView *metalView;
+@property(atomic, strong) RTCVideoFrame *videoFrame;
+@end
+
+@implementation RTCMTLNSVideoView {
+  id<RTCMTLRenderer> _renderer;
+}
+
+@synthesize renderer = _renderer;
+@synthesize metalView = _metalView;
+@synthesize videoFrame = _videoFrame;
+
+- (instancetype)initWithFrame:(CGRect)frameRect {
+  self = [super initWithFrame:frameRect];
+  if (self) {
+    [self configure];
+  }
+  return self;
+}
+
+- (instancetype)initWithCoder:(NSCoder *)aCoder {
+  self = [super initWithCoder:aCoder];
+  if (self) {
+    [self configure];
+  }
+  return self;
+}
+
+#pragma mark - Private
+
++ (BOOL)isMetalAvailable {
+  return YES;
+}
+
+- (void)configure {
+  if ([[self class] isMetalAvailable]) {
+    _metalView = [[MTKView alloc] initWithFrame:self.bounds];
+    [self addSubview:_metalView];
+    _metalView.translatesAutoresizingMaskIntoConstraints = NO;
+    _metalView.framebufferOnly = YES;
+    _metalView.delegate = self;
+
+    _renderer = [[RTCMTLI420Renderer alloc] init];
+    if (![(RTCMTLI420Renderer *)_renderer addRenderingDestination:_metalView]) {
+      _renderer = nil;
+    };
+  }
+}
+
+- (void)updateConstraints {
+  NSDictionary *views = NSDictionaryOfVariableBindings(_metalView);
+
+  NSArray *constraintsHorizontal =
+      [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[_metalView]-0-|"
+                                              options:0
+                                              metrics:nil
+                                                views:views];
+  [self addConstraints:constraintsHorizontal];
+
+  NSArray *constraintsVertical =
+      [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[_metalView]-0-|"
+                                              options:0
+                                              metrics:nil
+                                                views:views];
+  [self addConstraints:constraintsVertical];
+  [super updateConstraints];
+}
+
+#pragma mark - MTKViewDelegate methods
+- (void)drawInMTKView:(nonnull MTKView *)view {
+  if (view == self.metalView) {
+    [_renderer drawFrame:self.videoFrame];
+  }
+}
+
+- (void)mtkView:(MTKView *)view drawableSizeWillChange:(CGSize)size {
+}
+
+#pragma mark - RTCVideoRenderer
+
+- (void)setSize:(CGSize)size {
+  _metalView.drawableSize = size;
+  [_metalView draw];
+}
+
+- (void)renderFrame:(nullable RTCVideoFrame *)frame {
+  if (frame == nil) {
+    return;
+  }
+  self.videoFrame = [frame newI420VideoFrame];

[magjed_webrtc, 2017/03/28 11:20:29]

We should look at frame.nativeHandle instead and decide what renderer to use
(NV12 vs I420).

[daniela-webrtc, 2017/03/28 14:58:05]

Is it ok to fix this in upcoming CL when I do  the extraction in super class.
NV12Renderer will cause some compiling problems at its current state

[magjed_webrtc, 2017/03/30 08:29:28]

Yes, that's fine.

+}
+
+@end