IOS : UIScrollView and OpenGL

Question

So I have a OpenGL(glView) view that is rendering a menu which I aim to scroll. I was trying to avoid reinventing the UIScrollView and so I have place a scrollview on top of the glView.

The issue is that scrolling the scrollview pauses the rendering

A similar issue was discussed here Animation in OpenGL ES view freezes when UIScrollView is dragged on iPhone

Problem is I have no idea what [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; refers to

I have made a new CADisplayLink and tried to do the above with no luck

I have tried calling the render method in the scrollViewDidScroll

I have tried calling [self.view setNeedsDisplay];

I also found a referring to calling the timerLoop?

Can anyone help me out please

Answer 1

So, I have found a solution :)

create a CADisplayLink *_displayLink; property (you need import QuartzCore)

Have your scrollview on top.

    #pragma mark - scrollView Delegate

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //code for moving the object here    
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    [self startDisplayLinkIfNeeded];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    if (!decelerate) {
        [self stopDisplayLink];
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self stopDisplayLink];
}

#pragma mark Display Link

- (void)startDisplayLinkIfNeeded
{
    if (!_displayLink) {
        // do not change the method it calls as its part of the GLKView
        _displayLink = [CADisplayLink displayLinkWithTarget:self.view selector:@selector(display)];
        [_displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:UITrackingRunLoopMode];
    }
}

- (void)stopDisplayLink
{
    [_displayLink invalidate];
    _displayLink = nil;
}