Re: Reordering CALayer sublayers without raping my performance?
Re: Reordering CALayer sublayers without raping my performance?
- Subject: Re: Reordering CALayer sublayers without raping my performance?
- From: Jonathan del Strother <email@hidden>
- Date: Mon, 19 Nov 2007 09:09:28 +0000
On 16 Nov 2007, at 19:08, David Duncan wrote:
On Nov 16, 2007, at 10:54 AM, Jonathan del Strother wrote:
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."
Well, it is performing a sort when you set zPosition :). So it can
be more expensive than just reordering the sublayers array,
certainly so if you only have a 2D presentation.
Would you run that past me again? Changing the zPosition re-sorts the
sibling layers? In which case, is there any point in re-sorting the
child array to specify render order?
I'll test it out later, but I assume that CA is using a depth buffer
to make sure that higher zPositioned objects appear in front of
others, in which case the only time you need to worry about the order
of the child array ought to be if you're dealing with transparent
elements.
Is there any way of re-sorting the child element array that doesn't
incur a huge performance & memory hit?
Jonathan del Strother
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