Path: utzoo!utgpu!watserv1!watmath!iuvax!ux1.cso.uiuc.edu!sp29.csrd.uiuc.edu!hammer
From: hammer@sp29.csrd.uiuc.edu (David Hammerslag)
Newsgroups: comp.windows.x
Subject: Re: Synchronous vs Asynchrounous
Message-ID: <1990Feb1.213625.12870@ux1.cso.uiuc.edu>
Date: 1 Feb 90 21:36:25 GMT
References: <1990Feb1.200702.25274@agate.berkeley.edu>
Sender: news@ux1.cso.uiuc.edu (News)
Reply-To: hammer@uicsrd.csrd.uiuc.edu
Organization: University of Illinois Center for Supercomputing Research and Development
Lines: 52

In article <1990Feb1.200702.25274@agate.berkeley.edu>,
spanki@color.ced.berkeley.edu (Frank Goodman) writes:
> 
> I read the article about synchronous vs asynchronous, and I have a few
> question. I have a popup shell with a label as a child, and I want to
> use it for messages to the user. I pop it up in a callback, with a message
> like "Loading image, please be patient". However, since it is being poped up
> in a callback, and I then go off into a long process of loading an image, my
> label widget is never getting the text displayed. I believe, this is because
> the expose event is sitting in the Q while I load my image, and not getting
> processed while the popup is mapped. I call XFlush right after XtPopup,
> but that doesn't do it. How can I ge the text to display? I'm going to want
> to use this sort of message system throughout the program, I imagine, I will
> need to reset the string (via XtSetValues), as well as move the popup
> around. These messages are context specific, and therefore the moving, and
> labeling routines will be called from callback routines. How can I get my
> text to show?
> 

I faced a similar problem.  Here is what I did.  (Caveat:  it ain't pretty,
but is seems to work). If anybody is willing to share a more reasonable 
solution, I would like to see it.

notes:
	This is all under Motif.
	standby is an externally defined label
   
XfWorking()
{
    register XEvent event;
    XtAppContext app = _XtDefaultAppContext();
    Widget bboard;
    Window win;

    bboard = XtParent(standby);
    XtManageChild(bboard);  /* this pops up the shell */

    win = XtWindow(bboard);
    do /* be XtMainLoop until the bboard gets an expose event */
    {
	XtAppNextEvent(app, &event);
	XtDispatchEvent(&event);
    } while ((event.xany.window != win) ||
	     (event.type != Expose));

    XFlush(XtDisplay(standby));
}

-------------------------------------------------------------------------------
David Hammerslag            | "Woe to those who are wise in their own
hammer@uicsrd.csrd.uiuc.edu |  eyes and clever in their own sight." Isaiah 5:21
-------------------------------------------------------------------------------