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Re: CALayer + flickering redraw.
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Re: CALayer + flickering redraw.


  • Subject: Re: CALayer + flickering redraw.
  • From: John Clayton <email@hidden>
  • Date: Mon, 28 Apr 2008 22:51:23 +0200

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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References: 
 >CALayer + flickering redraw. (From: John Clayton <email@hidden>)

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