Re: CALayer + flickering redraw.

FROM : John Clayton
DATE : Mon Apr 28 22:51:23 2008

More info,

This migh be ovious, but:

I have found out that if I don't modify any of the layers while 
dragging a window about - then things stay very stable and look good. 
Probably no great surprise.  But as soon as I change the colour of a 
line for example, flickering occurs like mad.

I first thought maybe I was being silly and changing the colour many 
times per second, thus causing the flickering myself - but logging 
suggests that isn't the case.

Ideas / suggestions welcome...

--
John

On 28/04/2008, at 3:28 PM, John Clayton wrote:

> Hi
>
> I've created a borderless NSWindow that is used to draw a grid (via 
> CALayer instances - each line is a CALayer instance).  The window is 
> shown at the Screen Saver window level, thus overlapping 
> everything.  In my tests there are 3 or 4 lines in either direction, 
> i.e. we're not talking about thousands of layers here.
>
> When my grid window is being shown - and I move other applications 
> around underneath it, I see flickering of the grid image lines.  To 
> me it looks like the shadow of a window (created via the window 
> manager of course) is overwriting my grid lines briefly, but they do 
> get re-drawn again.
>
> To view this behaviour, check this link - I've created a movie to 
> show this.  Of note is:
> - the yellow line that appears is one of the layers
> - it fades in/out
> - it appears to be chopped in half, watch the differences between 
> the left hand portion of the line and the right hand, the redraw is 
> horizontally very uneven.
>
> link:
>     http://gallery.mac.com/john_clayton/100132
>
> Each line is one layer CALayer instance, with a border width of 1 
> and a filters property set to use a bloom.
>
> Has anyone seen this kind of behaviour before?  I'd appreciate any 
> tips that might lead to a solution I can share.
>
> Thanks
>
> --
> John Clayton
> http://www.coderage-software.com/
>
>
>
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