Calculates the union of two rectangles.
The union of rectangles src1 and src2 is the smallest rectangle which
includes both src1 and src2 within it.
It is allowed for dest to be the same as either src1 or src2.
Note that this function does not ignore 'empty' rectangles (ie. with
zero width or height).
Calculates the union of two rectangles. The union of rectangles src1 and src2 is the smallest rectangle which includes both src1 and src2 within it. It is allowed for dest to be the same as either src1 or src2.
Note that this function does not ignore 'empty' rectangles (ie. with zero width or height).