Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!rice!sun-spots-request
From: quasar@ctt.bellcore.com (Laurence R. Brothers)
Newsgroups: comp.sys.sun
Subject: drawing to the root window (hack hack)
Keywords: Windows
Message-ID: <14728@bellcore.bellcore.com>
Date: 31 Mar 89 11:32:10 GMT
Sender: usenet@rice.edu
Organization: Computer Technology Transfer, Bellcore
Lines: 27
Approved: Sun-Spots@rice.edu
Original-Date: 14 Mar 89 22:51:46 GMT
X-Sun-Spots-Digest: Volume 7, Issue 219, message 11 of 16

I've written a few hacks to draw stuff on the root window (I'm on a
Sun-4/260, OS 4.0, by the way). I open /dev/win0 and then pw_open the fd I
get. I now want to retain the pixwin I'm drawing to so as to automatically
handle damage. I presume the original root pixwin is retained, since it
does in fact handle damage.  I've fiddled with the pw_prretained pixrect
field of the root pixwin without success. I've tried a number of different
tacks, already, so I'd appreciate it if any suggestions anyone makes are
tested first...

As a digression, I should mention that there is approximately a 25%
failure chance for a program whose first two executable lines are:

  root_fd = open("/dev/win0");
  root_pixwin = pw_open(root_fd);

If it doesn't work, either root_fd is set to -1, (error "file already
exists") or pw_open fails to work and returns NULL. Somehow, the success
of a program is dependent on the structure of the rest of the source code
-- i.e., a given source file will either always work, or always not work.
Changing the file may randomly change this state -- any ideas? Giving open
its second argument seems to have no effect on this behavior.

Incidentally, using dbx on one of these programs causes it automatically
to fail to open /dev/win0, returning -1, so it is kind of hard to debug....

	    Laurence R. Brothers (quasar@ctt.bellcore.com)
Bellcore -- Computer Technology Transfer -- Knowledge-Based Systems Development