Animating a CALayer's mask size change

Question

I have a UIView subclass which uses a CAShapeLayer mask on its CALayer. The mask uses a distinct shape, with three rounded corners and a cut out rectangle in the remaining corner.

When I resize my UIView using a standard animation block, the UIView itself and its CALayer resize just fine. The mask, however, is applied instantly, which leads to some drawing issues.

I've tried animating the mask's resizing using a CABasicAnimation but didn't have any luck getting the resizing animated.

Can I somehow achieve an animated resizing effect on the mask? Do I need to get rid of the mask, or will I have to change something about the way I currently draw the mask (using - (void)drawInContext:(CGContextRef)ctx).

Cheers, Alex

Answer 1

The mask property of CALayer is not animatable which explains your lack of luck in that direction.

Does the drawing of your mask depend on the frame/bounds of the mask? (Can you provide some code?) Does the mask have needsDisplayOnBoundsChange property set?

Cheers, Corin

Answer 2

The mask parameter doesn't animate, but you can animate the layer which is set as the mask...

If you animate the CAShapeLayer's Path property, that should animate the mask. I can verify that this works from my own projects. Not sure about using a non-vector mask though. Have you tried animating the contents property of the mask?

Thanks, Jon