After my earlier posts, I kept digging at the issue and came up with
my own solution. I would however, appreciate feedback on the
validity of my fix.
The problem is this... when the window is resized we'll receive the
frame change notification. In Performer, the code updates the
glContext for the new location and dimensions. However, Performer
omits an important task... it should immediately render a frame to
the context, otherwise there might be garbage there for a short
amount of time before the next display link is called. So to do
this, I added a direct call to "renderAtTime:" just passing nil for
the time:
- (void) updateRenderView:(NSNotification*)notification
{
bool running = CVDisplayLinkIsRunning(_displayLink);
NSRect frame = [renderView frame];
CGLContextObj cgl_ctx = [_glContext CGLContextObj]; //By using
CGLMacro.h there's no need to set the current OpenGL context
//We have to stop rendering to prevent the Core Video Display Link
thread from accessing the OpenGL context at the same time
if(running)
CVDisplayLinkStop(_displayLink);
//Notify the OpenGL context its rendering view has changed
[_glContext update];
//Update the OpenGL viewport
glViewport(0, 0, frame.size.width, frame.size.height);
//We can safely restart rendering now
if(running)
CVDisplayLinkStart(_displayLink);
}
The above is not complete because "renderAtTime:" doesn't know how to
handle a nil value for the time. I'm not sure what the best solution
is, so I decided to simply ignore the incoming time value entirely.
In renderAtTime:, here is what I changed:
#if RESIZE_FLICKER_FIX
videoTime = [NSDate timeIntervalSinceReferenceDate];
#else
if(time->flags & kCVTimeStampVideoTimeValid)
videoTime = (NSTimeInterval)time->videoTime / (NSTimeInterval)time-
>videoTimeScale;
else
videoTime = 0; //Not sure what the best thing to do is
#endif
You'll also need to apply the same patch in to "copyImageForTime:" in
CompositionSource.m. With these patches, you can run Performer and
it will resize perfectly!
Now, my only question is... is this the best solution? While it
generally seems to work, I'm now ignoring the timestamp requested by
the displayLink. I sure which I knew how QCView handled this
internally. Can someone recomment a better solution?
thanks,
Chris
On Jul 11, 2007, at 1:28 PM, Chris Silverberg wrote:
As a quick followup to my previous message, take a look at Apple's
"Performer" sample code. If you run that application and start
resizing the window, you'll start to see lots of visible flicker in
the composition. This is exactly the problem that I have (not
surprising since my code is based on Performer.) So does someone
know how to fix Performer so that it doesn't have this flicker?
thanks!
Chris
On Jul 11, 2007, at 1:09 PM, Chris Silverberg wrote:
My view is working well, with one issue. When I resize my window
(and thus my view), I either see excessive flicker or rendering
artifacts. This suggests to me that I'm not handling resize
events properly. Unfortunately, there's not a lot of sample code
out there that uses QCRenderer... Apple's samples that do either
don't handle resizing at all or have the same resize issues that I
have.
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