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From: scott@graft.Berkeley.EDU (Scott Silvey)
Newsgroups: comp.windows.x
Subject: Re: Proper modal dialogs using Xt -- can it be done?
Message-ID: <26259@pasteur.Berkeley.EDU>
Date: 17 Jul 90 00:51:10 GMT
References: <1990Jul16.190239.7687@maytag.waterloo.edu>
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giguere@csg.UWaterloo.CA (Eric Giguere) writes:
|> This question was originally posted in the Motif newsgroup but no one's been
|> able to answer it for me so:
|> 
|> I want to create and display a modal dialog created as a widget under Motif.
|> That is, after I add callback routines, manage & display the widget, I want
|> my main program to wait (without busy-waiting!) until the widget is 
|> destroyed and not accept input into its main window while the dialog widget
|> is being displayed.  All the dialog examples I've seen so far that use the
|> Xt or Motif widget sets use modeless dialogs.
|> 
|> So, can I do this portably using X or do I have to resort to using system
|> calls such as the Unix signalling facility?
|> 
|> --
|> Eric Giguere                                       giguere@csg.UWaterloo.CA

You need to go through an event processing loop while the dialog is up.

This was far from obvious for me too, perhaps R5 could have a "convenience" 
  routine to pop up a modal dialog.

Here is the basic code needed:
------------------------------

Boolean ok=FALSE;

ok_button_cback(button, dialog_shell)
Widget button, dialog_shell
{
	extern Boolean ok;

	/* Do useful things here. */
	ok = TRUE;
	XtPopdown(dialog_shell);
}

prompt()
{
	extern Boolean ok;
	extern Widget toplevel;
	XEvent event;
	Widget dialog_shell, ok_button;

	dialog_shell = XtCreatePopupShell("Modal Dialog", transientShellWidgetClass,
	                                   toplevel, NULL, 0);
	ok_button = XtCreateManagedWidget("OK", commandWidgetClass,
dialog_shell, NULL, 0);
	XtAddCallback(ok_button, XtNcallback, ok_button_cback, dialog_shell);

	XtPopup(dialog_shell, XtGrabExclusive);

	while (!ok) {
		XtAppNextEvent(XtWidgetToApplicationContext(toplevel), &event);
		XtDispatchEvent(&event);
	}
	ok = FALSE;
}

-----------------------------

Note that this is for R4 Athena widgets.  You'll have to tailor the
details for 
  your case (probably R3 Motif?).  Also, I just typed this in from memory, so
  I'm not guaranteeing that I didn't forget something here, but the basic idea
  is demonstrated.  I also don't know if perhaps there are other/better ways to
  approach this problem either, I just know it works for me.

Hope this helps.

Scott