Calculates the union of two rectangles.
- macOS 10.0+
- Mac Catalyst 13.0+
Returns the smallest rectangle that completely encloses both
b. If one of the rectangles has 0 (or negative) width or height, a copy of the other rectangle is returned; but if both have 0 (or negative) width or height, the returned rectangle has its origin at (0.0, 0.0) and has 0 width and height.