ignored = FN VALIDRECT(rect)
February, 2002 (Release 6)
Before Carbon became a part of the Mac toolbox, we were able to use a toolbox procedure called VALIDRECT to mark a portion of the current window as an area that did not need to be refreshed during the next update. This call will not work in OS X (or in the Carbon version of OS 9). Our substitute,
FN VALIDRECT, will work in versions 7 through X without additional coding required on your part.