Add metal view, shaders and renderer.

webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.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/RTCMTLVideoView.h"
+
+#import <Metal/Metal.h>
+#import <MetalKit/MetalKit.h>
+
+#import "WebRTC/RTCLogging.h"
+#import "WebRTC/RTCVideoFrame.h"
+
+#import "RTCMTLNV12Renderer.h"
+
+@interface RTCMTLVideoView () <MTKViewDelegate>
+@property(nonatomic, strong) id<RTCMTLRenderer> renderer;
+@property(nonatomic, strong) MTKView *metalView;
+@property(atomic, strong) RTCVideoFrame *videoFrame;
+@end
+
+@implementation RTCMTLVideoView {
+  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 {
+#if defined(__OBJC__) && COREVIDEO_SUPPORTS_METAL
+  return YES;
+#elif
+  return NO;
+#endif
+}
+
+- (void)configure {
+  if ([RTCMTLVideoView isMetalAvailable]) {
+    _metalView = [[MTKView alloc] initWithFrame:self.bounds];
+    [self addSubview:_metalView];
+    _metalView.delegate = self;
+    _metalView.contentMode = UIViewContentModeScaleAspectFit;
+    _metalView.translatesAutoresizingMaskIntoConstraints = NO;
+    UILayoutGuide *margins = self.layoutMarginsGuide;
+    [_metalView.topAnchor constraintEqualToAnchor:margins.topAnchor].active = YES;
+    [_metalView.bottomAnchor constraintEqualToAnchor:margins.bottomAnchor].active = YES;
+    [_metalView.leftAnchor constraintEqualToAnchor:margins.leftAnchor].active = YES;
+    [_metalView.rightAnchor constraintEqualToAnchor:margins.rightAnchor].active = YES;
+
+    _renderer = [[RTCMTLNV12Renderer alloc] init];
+    if (![(RTCMTLNV12Renderer *)_renderer addRenderingDestination:_metalView]) {
+      _renderer = nil;
+    };
+  } else {
+    RTCLogError("Metal configuration falied.");
+  }
+}
+#pragma mark - MTKViewDelegate methods
+
+- (void)drawInMTKView:(nonnull MTKView *)view {
+  NSAssert(view == self.metalView, @"Receiving draw callbacks from foreign instance.");
+  [_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) {
+    RTCLogInfo(@"Incoming frame is nil. Exiting render callback.");
+    return;
+  }
+  self.videoFrame = frame;
+}
+
+@end