CALayer Live Resize Poor Performance

Question

I have a UI where the content of an NSCollectionViewItem's View is drawn programmatically through CALayers. I am using a CAConstraintLayoutManager to keep the layot of the sublayers consistent when resizing, but I am getting very poor performance when doing so. It seems that resizing the window, which causes the resize of two CATextLayers so that they fit the root layer's width, and the repositioning of one CATextLayer so that it stays right-aligned, is causing the application to spend most of its time executing the CGSScanConvolveAndIntegrateRGB function (I have used the Time Profiler instrument).

The most "expensive" layer (the one that causes the most stuttering even if it's the only one displayed) is a wrapped multiline CATextLayer. I have absolutely no idea how to get better performance (I have tried not using a CAConstraintLayoutManager and going with layer alignments but I'm getting the same thing). Has anyone had this problem? Is there a way around it?

PS: I have subclassed the layout manager and disabled all the animations during the execution of - (void)layoutSublayersOfLayer:(CALayer *)layer by setting YES to kCATransactionDisableActions in the CATransaction but it doesn't seems to help.

Edit: I have disabled Font Smoothing for the Text Layers and performance has increased a little bit (very little), but it spends an awful amount of time in _ZL9view_drawP7_CAViewdPK11CVTimeStampb (which is something that gets called by a thread of the ATI Radeon driver, I suppose).

It turns out that I was resizing ALL the views and not only the ones that were visible inside the ScrollView's visible rect. I am implementing a way to resize only the visible views because, as far as I can tell, there is no built in way to do that and it's not the default behavior. Go figure. — Gian Marco Toso, Nov 29 '11 at 15:56

Gian Marco Toso · Accepted Answer · 2011-11-29T16:58:48.390

I solved it. Kind of. It still seems like a dirty hack to me, but I couldn't find out how to make setNeedsDisplayInRect work so I ended up doing it like this:

In the NSWindow delegate:

-(void)windowWillStartLiveResize:(NSNotification *)notification { [[NSNotificationCenter defaultCenter] postNotificationName:@"beginResize" object:nil]; }

-(void)windowDidEndLiveResize:(NSNotification *)notification { [[NSNotificationCenter defaultCenter] postNotificationName:@"endResize" object:nil];
}
In my Custom View those two notifications call, respectively, the -(void)beginResize and -(void)endResize selectors. The first one sets a BOOL inLiveResize variable to YES, while the second one sets it to NO and calls setFrameSize again with the new frame size.

I overrode (overridden? Not native english speaker, sorry) the -(void)setFrameSize:(NSSize)newSize method like this:

-(void)setFrameSize:(NSSize)newSize 
{        
    if (inLiveResize) {
        NSRect scrollFrame = [[[self superview] enclosingScrollView] documentVisibleRect];

        BOOL condition1 = (self.frame.origin.y > (scrollFrame.origin.y - self.frame.size.height));
        BOOL condition2 = (self.frame.origin.y < (scrollFrame.origin.y + scrollFrame.size.height + self.frame.size.height));

        if (condition1 && condition2)
            [super setFrameSize:newSize];
    }
    else {
        [super setFrameSize:newSize]; }}

That's it. This way, only the visible views resize live with the window, while the others get redrawn at the end of the operation. It works, but I don't like how 'dirty' it is, I'm sure there is a more elegant, built-in(ish) way to do this by using the setNeedsDisplayInRect method. I will research more.

CALayer Live Resize Poor Performance

1 Answers1