Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!sun-barr!newstop!sun!kimba!hvr
From: hvr@kimba.Sun.COM (Heather Rose)
Newsgroups: comp.windows.x
Subject: Re: cleaning up from exit
Summary: XView interposition on notify clients
Message-ID: <132811@sun.Eng.Sun.COM>
Date: 11 Mar 90 02:13:28 GMT
References: <9003091424.AA26239@armory>
Sender: news@sun.Eng.Sun.COM
Reply-To: hvr@sun.UUCP (Heather Rose)
Organization: Sun Microsystems, Mountain View
Lines: 39

In article <9003091424.AA26239@armory> jimf%saber@HARVARD.HARVARD.EDU writes:
>|>> XtAddCleanUpProc(routine, client_data)
>|>> XtRemoveCleanUpProc(routine, client_data)
>
>|You might want to make this a more general solution.  Add the notion of
>|interposition to the Xt intrinsics as XView does.
>
>He's right, interposition is a much more general solution.  I suggest,
>however, *NOT* having an interposition call for each of the events
>that you want to interpose on.  The SunView/XView method, which has
>generic event interposers, destroy interposers, and others (five or
>six in all, I can never remember and the manuals are junk) is
>overcomplex.  It would have been better to have a single interposer
>and key off event types (which you have to do ANYWAY) instead of five
>or six of them.

Actually, interposition works on Notify Clients not Events.  Each notify
client has an event mask which specifies when it should be called.  The
interposer on the notify client will only be called when an event for
the interposee matches it's event mask.  Each callback supplied is a 
notify client.

I agree that the API for interposition could be simplified.  It's one
interface leftover from SunView that has not yet been changed for XView.
For example, window_create(), panel_create(), etc... have been collapsed
into xv_create().

FYI:  SunView System Programmer's Guide is pretty good on this subject.
Also, there's a good white paper on the SunView notifier from USENIX
proceedings about 3 or 4 years ago.  Author, Steve Evans.  Most of the
issues still apply.

If the manuals are junk, please let us know what the specific problems 
are so we can do something about it. 

__________________________________________________________________
Heather Rose
Window Systems Group                      internet:  hrose@sun.com
Sun Microsystems, Inc.                        uucp:  ...!sun!hrose