SubPt
SubPt Subtract coordinates of one point from an other void SubPt(srcPt, destPt ); Point srcPt ; first coordinate pair Point *destPt ; receives difference of destPt - srcPt SubPt subtracts the coordinates of one Point from an other, storing the result into the second.
srcPt is a 4-byte Point structure. Its low word is the horizontal coordinate and its high word is the vertical coordinate.
destPt is the address of a 4-byte Point structure. Upon return, it will contain the differences: (destPt.h-srcPt.h) and (destPt.v-destPt.v).
Notes: The SubPt operation separates the horizontal coordinate from the vertical coordinates before calculating the difference. It is functionally equivalent
to:
Perhaps more useful is DeltaPoint, which returns the difference as the return value of the function.