- union-rect rect1 rect2 #!optional result-rectprocedure
If result-rect is omitted or #f, a new managed sdl2:rect will be returned. If result-rect is an sdl2:rect, it will be modified and returned. It is safe for result-rect to be the same object as rect1 or rect2, in which case rect1 or rect2 will be modified and returned. It is safe (but useless) for rect1 and rect2 to be the same object.