Path: utzoo!attcan!uunet!zephyr.ens.tek.com!uw-beaver!rice!cs.utexas.edu!tut.cis.ohio-state.edu!snorkelwacker!bloom-beacon!LARRY.MCRCIM.MCGILL.EDU!mouse
From: mouse@LARRY.MCRCIM.MCGILL.EDU
Newsgroups: comp.windows.x
Subject: Re: ghostscript2.0 (was Re: fix to font cacheing in ralpage postscript viewer)
Message-ID: <9009201038.AA05265@Larry.McRCIM.McGill.EDU>
Date: 20 Sep 90 10:38:20 GMT
Sender: root@athena.mit.edu (Wizard A. Root)
Organization: The Internet
Lines: 32

> One thing that gs2.0 X previewer does do it paint to both a pixmap
> and the display.  That's kind of redundant,

Not entirely; it makes handling Expose events much simpler.

> but prompts the question [...]:

> How does one making ones own backing pixmap that works like
> backingstore?

It's not really difficult, but it's a bit tedious.  Just create the
pixmap, and then to draw something do

	- draw it to the pixmap
	- set the window's background to be the pixmap
	- draw it to the window

The order is necessary to avoid races with exposures, and the constant
resetting of the window's background is necessary because the server is
allowed to make a copy of the pixmap when you set the background.  (If
the server is copying the pixmap, this is also likely to be slow.)

I would like to see a something that could be passed in place of the
current backing-store hint that says "I want backing-store, and give me
an error if you can't commit to doing it" instead of the current
scheme, which allows the server to decommit backing-store at any time
for any reason.

					der Mouse

			old: mcgill-vision!mouse
			new: mouse@larry.mcrcim.mcgill.edu