SectRect

SectRect Get the intersection of two rectangles; check for overlap

#include <Quickdraw.h> Quickdraw

Boolean SectRect(rect1, rect2, resultRect );

Rect *rect1 ; addresses of two Rect ...

Rect *rect2 ; ... structures to intersect

Rect * resultRect ; receives intersection rectangle

returns Do the rectangles have any pixels in common?

SectRect checks to see if two rectangles share any points in common and

obtains the coordinates of the intersecting rectangle

rect1 and . . .

rect2 are addresses of two 8-byte Rect structures. They should use the

same coordinate system.

resultRect is the address of a third Rect structure. Upon return, it will contain

the coordinates of the intersection of rect1 and rect2 . If rect1 and

rect2 share no common points, this returns as the empty rectangle

(0,0)(0,0).

Returns: a Boolean value indicating whether or not rect1 and rect2 share

any common points. It is one of:

FALSE No overlap

TRUE Some overlap; resultRect is non-empty.

Notes: The figures below illustrate:

In the figure on the left, the intersection of rectangles A and B is shown in

black, labeled as rectangle C. The call to SectRect will return TRUE, and

resultRect will contain the coordinates of rectangle C.

The figure on the right illustrates an important concept: a shared border

or a single shared point are not considered as part of the mathematical

intersection of two rectangles. Rectangles D and E are right next to each

other and share a common border. However, their "overlap" area is a

single mathematical line, enclosing no bits of the bitMap. The call to

SectRect would return FALSE, and resultRect would be set to

(0,0)(0,0).

It is OK to specify resultRect as the same rectangle as either of rect1 or

rect2 . For instance, the following line would find the intersection of

rectangles A and B, and store its coordinates into rectangle A, overwriting

the original value.

SectRect( &rA, &rB, &rA );

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