Path: utzoo!attcan!uunet!husc6!bloom-beacon!GROUCH.JPL.NASA.GOV!PJS
From: PJS@GROUCH.JPL.NASA.GOV (Peter Scott)
Newsgroups: comp.windows.x
Subject: Clipping in X
Message-ID: <890831101108.000024A5092@grouch.JPL.NASA.GOV>
Date: 31 Aug 89 18:11:08 GMT
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 11

Question about the clipping algorithm used in X, prompted by some recent
postings:  say I draw a line from (x1, y1) to (x2,y2) within a window.
Then a portion of the window is obscured, cutting off the portion of
the line from (x1,y1) to (x,y).  Then the window is exposed again, and
I set that rectangle that needs to be repainted as a clipping region
and redraw my line from (x1,y1) to (x2,y2).  Will the same pixels be
turned on in the segment (x1,y1)->(x,y) as before?  Or does X use (say)
the Cohen-Sutherland clipping algorithm, which might result in a slightly
different line if the original did not pass *exactly* through (x,y)?

Peter Scott (pjs@grouch.jpl.nasa.gov)