Re: Core Animation Flickering

FROM : Colin Cornaby
DATE : Sun Apr 27 08:45:33 2008

Just an update on this issue...

Everything looked fine in the console when I enabled that debug 
switch. However, I've sidestepped the issue and created an alternate 
implementation that does not flicker. Drawing manually in a CALayer 
had other challenges, such as not doing synchronized drawing with the 
window resize.

I originally encountered this flickering issue a while ago. I 
originally sidestepped it by doing my drawing in an NSView, and then 
adding that as a subview to the parent layer. I was informed by 
someone when I asked about CoreAnimation deadlocks that adding a 
NSView to a layer might affect working the layer tree that view is a 
member of. I'm not sure if that was what was causing the issue, but I 
removed the NSView from the parent layer anyway just to be safe, and 
went back to looking at a fully CA solution to what I needed to draw.

I will get the test case working if I have time and post it to the 
list. I'm trying to get something prepped for ADA so I'm on a tight 
schedule here...

On Apr 25, 2008, at 8:52 AM, John Harper wrote:

>
> On Apr 25, 2008, at 1:20 AM, Colin Cornaby wrote:
>

>> I have a CALayer subclass, set to redraw on bounds change, with the 
>> following draw code (I don't expect it to be meaningful, but I'm 
>> pasting it here for the sake of completeness.)
>> …
>> It's parent view is set up to change the layers frame to always 
>> fill the contents of the entire view on 
>> resizeWithOldSuperviewSize:.  This works great, except for a really 
>> annoying flicker that occurs once every few seconds while the view 
>> is resizing. Every layer in the view flickers in and out (stuff 
>> like background colors doesn't flicker).
>>
>> Did I miss some drawing cleanup or something else obvious here?

>
> One thing to check for is that the bounds of one of your layers 
> isn't being set to empty temporarily. Running your program with the 
> CA_PRINT_TREE environment variable set to "1" is a good way to debug 
> that, you can scan the logs for anything that looks suspicious. If 
> you don't see anything, file a radar with a test case and we will 
> look into it…
>
>     John
>
>