How to add a CALayer to an NSView on Mac OS X

Question

I\'m trying to learn how to use and implement CALayer in a Mac Objective-C application, but I can\'t seem to probably do the most basic thing - add a new layer and

Answer 1

First of all, you don't want to add a layer in the drawRect: method of a view, this gets called automatically by the system and you'd probably end up with a lot more layers than you actually want. initWithFrame: or initWithCoder: (for views that are in a nib file) are better places to initialize your layer hierarchy.

Furthermore, NSViews don't have a root layer by default (this is quite different from UIView on iOS). There are basically two kinds of NSViews that use a layer: layer-backed views and layer-hosting views. If you want to interact with the layer directly (add sublayers etc.), you need to create a layer-hosting view.

To do that, create a CALayer and call the view's setLayer: method. Afterwards, call setWantsLayer:. The order is important, if you'd call setWantsLayer: first, you'd actually create a layer-backed view.