Calculates the intersection of two rectangles. It is allowed for
dest to be the same as either src1 or src2. If the rectangles
do not intersect, dest’s width and height is set to 0 and its x
and y values are undefined. If you are only interested in whether
the rectangles intersect, but not in the intersecting area itself,
pass %NULL for dest.
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).
Defines the position and size of a rectangle. It is identical to #cairo_rectangle_int_t.