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From: klee@gilroy.pa.dec.com (Ken Lee)
Newsgroups: comp.windows.x
Subject: Re: do-it-yourself popups in Xlib
Keywords: how
Message-ID: <1519@bacchus.dec.com>
Date: 21 Jun 89 17:47:55 GMT
References: <4748@alvin.mcnc.org>
Sender: news@decwrl.dec.com
Distribution: na
Lines: 44

In article <4748@alvin.mcnc.org>, pickel@mcnc.org (Lisa C. Pickel) writes:
> I want to draw objects inside my popups and then, when I kill the popup, 
> have the whole mess disappear.  It does not.  I've tried:
> 
> 1) Save-under.  We don't have it.  That's out.
> 
> 2) Saving the underlying pixmap before mapping the popup (with 
>    IncludeInferiors set).  However, I still get garbage in the pixmap 
>    where other popups beneath the popup in question lie.  (Yes, 
>    everybody has the same depth).

Although I hate to admit it, I did this with an X11R1 server (no
save-under or backing store):

1.  grab the server to make sure the lower windows don't get modified
when your popup is up
2.  calculate your window position and size, then copy the pixmap
(include inferiors) that would be beneath it
3.  map your popup window override-redirect so the window manager
doesn't put it somewhere else
4.  send the underlying windows a client message containing the
geometry of the popup (so they can ignore the exposure when you unmap
the popup) - you do need a private inter-client protocol to manage this
5.  eventually unmap your popup
6.  copy the pixmap back into position
7.  ungrab the server

If you have multiple overlapping popups, this still works as long as
they're unmapped in the reverse of the order in which they were
mapped.  Fortunately, this was true of my case, a popup-menu
heirarachy.  Note that step 4 is error-prone.  If you're not really
careful (or lucky) you may ignore valid exposure events.

Is all this worth the effort?  In most cases, definately not.  But, if
your machine is really slow AND your graphics will take a looong time
to reproduce after an exposure AND you can't hack your server to add
backing store or save under AND the server grab doesn't screw up your
other clients, then maybe you have to do it.

Ken Lee

DEC Western Software Laboratory, Palo Alto, Calif.
Internet: klee@decwrl.dec.com
Uucp: uunet!decwrl!klee