Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!gatech!bloom-beacon!LARRY.MCRCIM.MCGILL.EDU!mouse
From: mouse@LARRY.MCRCIM.MCGILL.EDU
Newsgroups: comp.windows.x
Subject: Re:  Emulating pixmap with window
Message-ID: <9011290544.AA06573@Larry.McRCIM.McGill.EDU>
Date: 29 Nov 90 05:44:09 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 34

> Is it possible to emulate the functionality of a pixmap with an
> unmapped window?

Yes - if you can somehow make certain the server will maintain
backing-store for it.  Unfortunately, X does not guarantee this (though
some servers might, it is not required).

> If so, could someone point me in the direction of some sample code?
> I ask this since I am forced to use the DECwindows server running on
> a DEC VS3100 with GPX chip set which is apparently limited to pixmaps
> no higher/wider than the screen; windows created under this
> configuration do not seem to have this limitation.

Yeesh.  I'm sure that's perfectly legal, but it still seems broken to
me.  (Sort of like providing only three different cursor shapes, with
no capability for any other: legal but definitely not good.)

I'd just call it a broken server, submit a bug report to the vendor,
and write it off as a useful X machine until/unless a fix is
forthcoming.  (Assuming that there isn't some reasonable excuse, like a
tiny memory limit, responsible for the failure.  For example, if I can
create a large number of pixmaps as big as the screen, but not even one
that's only slightly bigger, I'd call it broken.)

What error do you get when you try to create a big pixmap?  (If it's
anything but BadAlloc, I think it probably is a protocol violation.
The only errors that are listed for the CreatePixmap request are
IDChoice (which indicates an Xlib bug or perhaps memory corruption),
Drawable, Value, and Alloc.)

					der Mouse

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