Re: CALayer - delegate not being called?

FROM : Scott Anguish
DATE : Wed Nov 28 19:43:03 2007

Well, it isn't quite the same.. not drawing, but compositing.

The border is a style attribute (and is an animatable property).  All 
animatable properties are applied by the render-tree when the layer is 
displayed in the UI.  So they get composited when you change the 
values via the implied animation (unless of course that has been 
disabled for the transaction in which case they still will update and 
draw, but without interpolating the values from the current value to 
the new value).

You can imagine that if the content was redrawn (by the delegate) 
every time a value changed and animated (so potentially hundreds of 
times for a single animation) that you'd lose most of the advantages 
of Core Animation.

Regardless, animatable properties are not aren't cached and are 
separate from the content caching process.

You don't have to, and should not, call setNeedsDisplay for any layers 
that do not have a delegate that provides the content. This will 
create a content cache and cause more memory to be used for the cached 
content.  For larger empty layers that are used only to contain other 
layers it is unnecessary.

I'll spend some time clarifying this in the Core Animation Programming 
Guide in both the Providing Layer Content and Layer Style Properties 
chapters.


On Nov 28, 2007, at 5:21 AM, John Clayton wrote:

> Hi Scott,
>
> But Neil is saying that the border of the layer is visible, thus the 
> layer must be drawing itself at some point already, right?