Path: utzoo!attcan!uunet!lll-winken!ames!ucsd!rutgers!bellcore!spectral!sjs
From: sjs@spectral.ctt.bellcore.com (Stan Switzer)
Newsgroups: comp.windows.news
Subject: Re: retained canvases - application writers please read
Message-ID: <13405@bellcore.bellcore.com>
Date: 12 Jan 89 22:44:01 GMT
References: <24631@sgi.SGI.COM> <1154@murtoa.cs.mu.oz.au> <11090@ulysses.homer.nj.att.com> <13402@bellcore.bellcore.com>
Sender: news@bellcore.bellcore.com
Reply-To: sjs@ctt.bellcore.com (Stan Switzer)
Organization: Bellcore
Lines: 24

In article <13402@bellcore.bellcore.com> I write:
> Well, there ARE parentless canvases, but as Chris discovered and as I
> have just confirmed, you can't create them with "newcanvas" or even
> mutate a parented canvas into one.  The only retained, parentless
> canvases that I can find are the result of "readcanvas."

I have looked into this a bit further and it seems that I overlooked
"buildimage" which seems to be able to build a non-parented, retained
canvas of just about any size and depth.

You seem to be able to reparent this canvas and map it (it worked for
me).  Interestingly, though, trying to set the parent back to null
(canvas /Parent null put) both works and doesn't.  It does reset the
parent to null but gives you a "typecheck" error after having done so.
I guess you could use "errored" to get around it if it mattered.

I guess I answered my own question about how I can create a 1 pixel
deep canvas to use with imagemaskcanvas that works regardless of
whether your workstation is color or not.

Now back to the original question.  Is this the exception to the
"retained is only an optimization" rule?

Stan Switzer  sjs@ctt.bellcore.com  "What's this big red button do?"