Returns the smallest rectangle that contains the two source rectangles.
- iOS 2.0+
- macOS 10.0+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
- Core Graphics
Another rectangle to be combined with this rectangle.
The smallest rectangle that completely contains both of the source rectangles.
Both rectangles are standardized prior to calculating the union. If either of the rectangles is a null rectangle, a copy of the other rectangle is returned (resulting in a null rectangle if both rectangles are null). Otherwise a rectangle that completely contains the source rectangles is returned.