Subtracts prclSrc2 from prclSrc1.

prclSrc1, prclSrc2, and prclDest must be distinct RECTL structures.

Subtracting one rectangle from another does not always result in a rectangular area. When this occurs, this function returns prclSrc1 in prclDest. For this reason, this function provides only an approximation of subtraction. However, the area described by prclDest is always greater than, or equal to, the true result of the subtraction.

GpiCombineRegion can be used to calculate the true result of the subtraction of two rectangular areas. The WinSubtractRect function is much faster.