[comp.windows.x] watch out for "negative" values in width or height to XDrawArc

tomt@maui.coral.COM (Tom Tulinsky) (08/01/90)

I accidently passed a negative number into an unsigned that eventually
was passed to XDrawArc as the Height parameter.  The negative was
interpreted as a large positive (65527) and so no error message was
given, but my program slowed to a crawl (XDrawArc took about 15 sec.
of solid cpu processing to return; it also generated a massive amount
of paging).  I had to step through the drawing to find it.

This happened when I was zooming out some graphics, making them
smaller while subtracting some constants from them. Eventually the
scaled sizes were smaller than the constant and the result went
negative. Watch out...

I wouldn't be surprised if similar things happened to
XDraw/FillRectangle.


 Coral
     * **	Tom Tulinsky                508 460-6010
  *  **		Coral Network Corporation   fax 508 481-6258
*  ** 		734 Forest St               net: tomt@coral.com
 ***		   Marlboro, MA 01752		
  **		   U S A
*********	
NETWORKS