Masking a CALayer with another CALayer

Question

I\'m trying to make a donut shape with CALayers. One CALayer will be a large circle, the other one will be a smaller circle positioned in its center, masking it.

The la

Answer 1

Indeed, as @David indicates the current (iOS 5.1) CALayer masks can't be reversed, which poses a problem if you want to use them to make a transparent hole a simple circular CALayer.

What you can do to get a donut is make a circular CALayer's backgroundColor transparent, but give it a borderColor and a wide borderWidth. Here's the dunkin' code:

    CALayer *theDonut = [CALayer layer];
    theDonut.bounds = CGRectMake(0,0, radius, radius);
    theDonut.cornerRadius = radius/2;
    theDonut.backgroundColor = [UIColor clearColor].CGColor;

    theDonut.borderWidth = radius/5;
    theDonut.borderColor = [UIColor orangeColor].CGColor;

    [self.layer addSublayer:theDonut];