RTCEAGLVideoView: Fix GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT error.

talk/app/webrtc/objc/RTCEAGLVideoView.m

Index: talk/app/webrtc/objc/RTCEAGLVideoView.m
diff --git a/talk/app/webrtc/objc/RTCEAGLVideoView.m b/talk/app/webrtc/objc/RTCEAGLVideoView.m
index 61040ba1025c2f23eed07f916df93d36b2955d76..d19462c9d97576b841df86cd6f1872fc738de2ba 100644
--- a/talk/app/webrtc/objc/RTCEAGLVideoView.m
+++ b/talk/app/webrtc/objc/RTCEAGLVideoView.m
@@ -92,6 +92,18 @@
 
 @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.
@@ -104,6 +116,9 @@
   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 {
@@ -137,6 +152,7 @@
   _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
@@ -158,13 +174,7 @@
   __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];
 }
@@ -181,6 +191,16 @@
 
 #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;
@@ -213,6 +233,26 @@
 
 #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];