Core Animation layout behavior during live window resize

FROM : Ben Kazez
DATE : Wed Feb 06 21:12:35 2008

Hi,

I have a layer-backed view that resizes to fit the available space in 
the window. During live window resizes, I'd like the layers to resize 
with no animation.

1. I get a crash when I begin a transaction and use 
kCATransactionDisableActions within the layout manager's -
layoutSublayersOfLayer method.

2. Disabling actions within a transaction from viewWillStartLiveResize/
viewDidEndLiveResize seems to disable the animation, but I can't be 
sure, because the view content isn't updated properly: The background 
color of the root layer is not redrawn, and the layers do not 
reposition themselves.

3. To fix #2, I tried setAutoresizesSubviews:YES and laying out the 
root layer (-layoutIfNeeded or -setNeedsLayout) from -
resizeSubviewsWithOldSize, but this had no effect.

4. As a proof of concept, I tried unsetting the root layer from the 
view (setLayer:nil) and setting wantsLayer:NO, and then drawing a 
plain black background in -drawRect during live resizes. (My thinking 
was that eventually I'd render the root layer contents to an image and 
scale the image to provide a low-resolution preview during live window 
resizes.) However, this caused crazy drawing artifacts and window 
flickering.

I'm surely missing something obvious. What's the recommended way of 
doing this?

Ben