Detranslate a rectangle (subtract offset)
PhRect_t *PhDeTranslateRect( PhRect_t *rect, PhPoint_t const *delta );
This convenience function subtracts delta->x from rect->ul.x and rect->lr.x, and subtracts delta->y from rect->ul.y and rect->lr.y. You'll find this function handy for translating events, extents, or canvases so they become relative to various points.
A pointer to the rect argument.
PhPoint_t, PhRect_t, PhTranslateRect()
“Geometry data types” in the Working with Code chapter of the Photon Programmer's Guide