Checks if the two given rectangles are equal.
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.