RTCEAGLVideoView: Fix GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT error.

talk/app/webrtc/objc/RTCEAGLVideoView.m

 /*
  * libjingle
  * Copyright 2014 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 74 matching lines @@
 - (void)invalidate {
   [_displayLink invalidate];
 }
 
 - (void)displayLinkDidFire:(CADisplayLink*)displayLink {
   _timerHandler();
 }
 
 @end
 
+// RTCEAGLVideoView wraps a GLKView which is setup with
+// enableSetNeedsDisplay = NO for the purpose of gaining control of
+// exactly when to call -[GLKView display]. This need for extra
+// control is required to avoid triggering method calls on GLKView
+// that results in attempting to bind the underlying render buffer
+// when the drawable size would be empty which would result in the
+// error GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT. -[GLKView display] is
+// the method that will trigger the binding of the render
+// buffer. Because the standard behaviour of -[UIView setNeedsDisplay]
+// is disabled for the reasons above, the RTCEAGLVideoView maintains
+// its own |isDirty| flag.
+
 @interface RTCEAGLVideoView () <GLKViewDelegate>
 // |i420Frame| is set when we receive a frame from a worker thread and is read
 // from the display link callback so atomicity is required.
 @property(atomic, strong) RTCI420Frame* i420Frame;
 @property(nonatomic, readonly) GLKView* glkView;
 @property(nonatomic, readonly) RTCOpenGLVideoRenderer* glRenderer;
 @end
 
 @implementation RTCEAGLVideoView {
   RTCDisplayLinkTimer* _timer;
   GLKView* _glkView;
   RTCOpenGLVideoRenderer* _glRenderer;
+  // This flag should only be set and read on the main thread (e.g. by
+  // setNeedsDisplay)
+  BOOL _isDirty;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame {
   if (self = [super initWithFrame:frame]) {
     [self configure];
   }
   return self;
 }
 
 - (instancetype)initWithCoder:(NSCoder *)aDecoder {
@@ skipping 13 matching lines @@
 
   // GLKView manages a framebuffer for us.
   _glkView = [[GLKView alloc] initWithFrame:CGRectZero
                                     context:glContext];
   _glkView.drawableColorFormat = GLKViewDrawableColorFormatRGBA8888;
   _glkView.drawableDepthFormat = GLKViewDrawableDepthFormatNone;
   _glkView.drawableStencilFormat = GLKViewDrawableStencilFormatNone;
   _glkView.drawableMultisample = GLKViewDrawableMultisampleNone;
   _glkView.delegate = self;
   _glkView.layer.masksToBounds = YES;
+  _glkView.enableSetNeedsDisplay = NO;
   [self addSubview:_glkView];
 
   // Listen to application state in order to clean up OpenGL before app goes
   // away.
   NSNotificationCenter* notificationCenter =
     [NSNotificationCenter defaultCenter];
   [notificationCenter addObserver:self
                          selector:@selector(willResignActive)
                              name:UIApplicationWillResignActiveNotification
                            object:nil];
   [notificationCenter addObserver:self
                          selector:@selector(didBecomeActive)
                              name:UIApplicationDidBecomeActiveNotification
                            object:nil];
 
   // Frames are received on a separate thread, so we poll for current frame
   // using a refresh rate proportional to screen refresh frequency. This
   // occurs on the main thread.
   __weak RTCEAGLVideoView* weakSelf = self;
   _timer = [[RTCDisplayLinkTimer alloc] initWithTimerHandler:^{
       RTCEAGLVideoView* strongSelf = weakSelf;
-      // Don't render if frame hasn't changed.
-      if (strongSelf.glRenderer.lastDrawnFrame == strongSelf.i420Frame) {
-        return;
-      }
-      // This tells the GLKView that it's dirty, which will then call the
-      // GLKViewDelegate method implemented below.
-      [strongSelf.glkView setNeedsDisplay];
+      [strongSelf displayLinkTimerDidFire];
     }];
   [self setupGL];
 }
 
 - (void)dealloc {
   [[NSNotificationCenter defaultCenter] removeObserver:self];
   UIApplicationState appState =
       [UIApplication sharedApplication].applicationState;
   if (appState == UIApplicationStateActive) {
     [self teardownGL];
   }
   [_timer invalidate];
 }
 
 #pragma mark - UIView
 
+- (void)setNeedsDisplay {
+  [super setNeedsDisplay];
+  _isDirty = YES;
+}
+
+- (void)setNeedsDisplayInRect:(CGRect)rect {
+  [super setNeedsDisplayInRect:rect];
+  _isDirty = YES;
+}
+
 - (void)layoutSubviews {
   [super layoutSubviews];
   _glkView.frame = self.bounds;
 }
 
 #pragma mark - GLKViewDelegate
 
 // This method is called when the GLKView's content is dirty and needs to be
 // redrawn. This occurs on main thread.
 - (void)glkView:(GLKView*)view drawInRect:(CGRect)rect {
@@ skipping 12 matching lines @@
     [strongSelf.delegate videoView:strongSelf didChangeVideoSize:size];
   });
 }
 
 - (void)renderFrame:(RTCI420Frame*)frame {
   self.i420Frame = frame;
 }
 
 #pragma mark - Private
 
+- (void)displayLinkTimerDidFire {
+  // Don't render unless video frame have changed or the view content
+  // has explicitly been marked dirty.
+  if (!_isDirty && _glRenderer.lastDrawnFrame == self.i420Frame) {
+    return;
+  }
+
+  // Always reset isDirty at this point, even if -[GLKView display]
+  // won't be called in the case the drawable size is empty.
+  _isDirty = NO;
+
+  // Only call -[GLKView display] if the drawable size is
+  // non-empty. Calling display will make the GLKView setup its
+  // render buffer if necessary, but that will fail with error
+  // GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT if size is empty.
+  if (self.bounds.size.width > 0 && self.bounds.size.height > 0) {
+    [_glkView display];
+  }
+}
+
 - (void)setupGL {
   self.i420Frame = nil;
   [_glRenderer setupGL];
   _timer.isPaused = NO;
 }
 
 - (void)teardownGL {
   self.i420Frame = nil;
   _timer.isPaused = YES;
   [_glkView deleteDrawable];
   [_glRenderer teardownGL];
 }
 
 - (void)didBecomeActive {
   [self setupGL];
 }
 
 - (void)willResignActive {
   [self teardownGL];
 }
 
 @end