When programming my app, I get to the point where I have to update two rectangles on the screen. So I call [self setNeedsDisplayInRect:rect1] and then [self setNeedsDisplayInRect:rect2]. When my drawRect method is called, the rectangle parameter is the smallest rectangle which contains both rect1 and rect2.

I can handle this with no problem, but when the two rectangles are far apart, then I am updating a lot of real estate with no gain. In this case, I would just like to repaint my two small rectangles.

So my question is how can I prevent the underlying system from coalescing my two calls into one?