Search code examples
iosswiftobjective-cuikitshadow

Why NSShadow's and CALayer's shadowOffset expressed via CGSize type and not CGPoint type

I wonder if there is historical reasoning (or any reasoning at all) behind making shadowOffset of NSShadow and CALayer expressed via CGSize type and NOT CGPoint type?

I believe that by its meaning, the "shadow offset" is a vector, pointing to an origin of shadow in relation to layer.frame.origin (or layer.bounds.origin). So it seems more convenient for it to be CGPoint instead of CGSize.

Thanks in advance!

Solution

  • A point is a location in a coordinate space. A size describes distances in the x&y dimensions.

    If you used a CGPoint for shadowOffset, it would need to be a point relative to some other point. What point? The center of the shadow path? The origin? In terms of the bounds, or the frame?

    An offset is an amount in 2 dimensions. A point is a location. It makes perfect sense to me to use a CGSize for shadowOffset, and it would not make sense to use a point.