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From: weikart@prl.dec.com (Chris Weikart)
Newsgroups: comp.windows.x.motif
Subject: Re: Blocking actions in Motif and X
Keywords: Motif, X, Blocking
Message-ID: <1990Jul12.105610.10481@prl.dec.com>
Date: 12 Jul 90 10:56:10 GMT
References: <858@airgun.wg.waii.com>
Sender: news@prl.dec.com (USENET News System)
Reply-To: weikart@prl.dec.com (Chris Weikart)
Organization: Digital Equipment Corporation - Paris Research Laboratory
Lines: 77

In article <858@airgun.wg.waii.com> lampshir@airgun.wg.waii.com (gregory
b. lampshir) writes:

> ... What I would like to do is use the following code segment
>
> Boolean answer;
> ...
> answer = DoNotReturnWithoutAnswer("Do you want to continue?");
> ...
>
> to return an answer.  However, in the event driven environment, even
> with the widget's dialog type set to application modal, the func
> 'DoNotReturnWithoutAnswer' returns before the user can respond.  The
> yes/no widget, however, is left displayed waiting for the user in an
> event driven manner.

There've already been some suggestions posted about libraries you can pick up,
but having run into the same problem myself I thought I'd post my solution.

First of all, use an XmMessageDialog, which has Ok, Cancel and Help callbacks.
Create the dialog, and change Ok/Cancel to Yes/No, and unmanage Help,
if that's what you want.

Call DialogLoop(your_dialog_widget) to launch the thing modally. Your yes and
no callbacks should each set a global (or some user_data) to indicate the
answer, then call DialogStop(your_dialog_widget) to allow DialogLoop to exit.

So your DoNotReturnWithoutAnswer can look like this:

Boolean DoNotReturnWithoutAnswer (message)
char *message;
{
    /* create dialog_widget, customize, etc. if not already */

    /* install message as text */

    DialogLoop(dialog_widget); /* won't return until DialogStop called */

    return (value_set_from_callback);
}

Here's the source for DialogLoop and DialogStop:

/*
 * CMW (Thu Jun 14 17:24:21 1990)...
 * To be really general purpose and safe, DialogLoop and DialogStop
 * should accept a pointer to a context that holds the (now global)
 * DialogLoopControl boolean, as well as an indication that allows
 * the dialog to be either modal or modeless...
 */

Static Bool DialogLoopControl;		/* global for now... */

Void DialogLoop (Dialog)
Widget Dialog;
{
    XtManageChild(Dialog);
    XtAddGrab(Dialog,TRUE,FALSE); /* hard-wired for now... */

    for (DialogLoopControl = True;  DialogLoopControl;  )
    {
	XEvent event;
	XtNextEvent(&event);
	XtDispatchEvent(&event);
    }
}

Void DialogStop (Dialog)
Widget Dialog;
{
    DialogLoopControl = False;
    XtRemoveGrab(Dialog);	/* hard-wired for now... */
    XtUnmanageChild(Dialog);
}

Have fun,
Chris