playing with two CGRect

Question

I have two rectangle R1 and R2

---------------------------------
|R1                             |
|                               |
|     ------------------        |
|     |                |        |
|     |  R2            |        |
|     |                |        |
---------------------------------

R1 represents the biggest one, and R2 the smallest one. I would like to send the area that we have if we subtract R2 to R1 to my method that takes a rect as input. Is that even possible? Any measure to dodge that

Answer 1

Find area

-(CGSize)areaOfRect:(CGRect)outerRect minusRect:(CGRect)innerRect
{
    return (outerRect.size.width - innerRect.size.width) * (outerRect.size.height - innerRect.size.height);
}

Find rects (Assuming these two rects are working from the same bounds)

typedef void(^RectCompletion)(CGRect topRect,CGRect leftRect,CGRect rightRect,CGRect bottomRect);


-(void)rectsForRect:(CGRect)outerRect minusRect:(CGRect)innerRect withCompletion:(RectCompletion)completion
{
    // First sanity..
    // You'll need to build up a list of prerequisite checks

    if (innerRect.origin.x < outerRect.origin.x)
        outerRect.origin.x = innerRect.origin.x;

    if (innerRect.origin.y < outerRect.origin.y)
        outerRect.origin.y = innerRect.origin.y;

    if (innerRect.origin.x + innerRect.size.width > outerRect.origin.x + outerRect.size.width)
        NSLog(@"Trim to edge");

    if (innerRect.origin.x > outerRect.origin.x + outerRect.size.width || innerRect.origin.y > outerRect.origin.y + outerRect.size.width)
        NSLog(@"Trim to edge");

    // etc...


    // Assuming the rect is always in bounds below should give you the 4 rects surrounding the inner rect.. 

    // With overlap..

    CGRect topRect = CGRectMake(outerRect.origin.x, outerRect.origin.y, outerRect.size.width, innerRect.origin.y);
    CGRect leftRect = CGRectMake(outerRect.origin.x, outerRect.origin.y, innerRect.origin.x, outerRect.size.height);
    CGRect rightRect = CGRectMake(innerRect.origin.x + innerRect.size.width, outerRect.origin.y, outerRect.size.width - (innerRect.origin.x + innerRect.size.width), outerRect.size.height);
    CGRect bottomRect = CGRectMake(outerRect.origin.x, outerRect.size.height - (innerRect.origin.y + innerRect.size.height), outerRect.size.width, outerRect.size.height - (innerRect.origin.y + innerRect.size.height));


    // No overlap

    CGRect topRect = CGRectMake(outerRect.origin.x, outerRect.origin.y, outerRect.size.width, innerRect.origin.y);
    CGRect leftRect = CGRectMake(outerRect.origin.x, innerRect.origin.y, innerRect.origin.x, innerRect.size.height);
    CGRect rightRect = CGRectMake(innerRect.origin.x + innerRect.size.width, innerRect.origin.y, outerRect.size.width - (innerRect.origin.x + innerRect.size.width), innerRect.size.height);
    CGRect bottomRect = CGRectMake(outerRect.origin.x, outerRect.size.height - (innerRect.origin.y + innerRect.size.height), outerRect.size.width, outerRect.size.height - (innerRect.origin.y + innerRect.size.height));

    completion(topRect,leftRect,rightRect,bottomRect);
}