Re: Reordering CALayer sublayers without raping my performance?

FROM : Jonathan del Strother
DATE : Fri Nov 16 19:54:29 2007

On 16 Nov 2007, at 18:48, David Duncan wrote:

> On Nov 16, 2007, at 10:41 AM, Jonathan del Strother wrote:
>

>> I have a root CALayer with around 250 child layers.  Only 50 or so 
>> are visible at a time, the rest have their opacity set to 0 (which 
>> I've found to be far more performant that continuously removing and 
>> adding child layers).
>>
>> Every 0.2 seconds, I want to move one of these child layers to be 
>> drawn on the top of everything else.  I'm doing this by altering 
>> the order of the root layer's sub layers.  I haven't been able to 
>> find an acceptable way of doing this.  Everything I've tried will 
>> continuously increase my virtual memory usage to ~3.5GB, before 
>> dropping back to 1.1GB every 10 seconds or so.  While that drop 
>> happens, my application performance drops massively, displaying a 
>> frame a second at best, on a Mac Pro with 3GB RAM.

>
>
> Use the zPosition property. All layers with a larger zPosition will 
> be placed in front of those with a smaller one. The default value is 
> 0.


Hmm, you're right.

Am I misreading this, or does the "Layer Geometry and Transforms" page 
tell me something completely different :
"The zPosition is intended to be used to set the visual position of 
the layer relative to its sibling layers. It should not be used to 
specify the order of layer siblings, instead reorder the layer in the 
sublayer array."