[g-a-devel]visual bell

[Bill Haneman <bill haneman sun com>]

Hi:

I attach a small C program that implements a 'visual bell' feature.

The program runs standalone and listens for XBell events and XkbBell
events, and flashes the screen when they occur.

It may make sense to integrate this into Metacity, but there are
technical reasons why that is difficult at the moment.  In the meantime
the attached program may prove useful.

best regards,

Bill


/*
 * AT-SPI - Assistive Technology Service Provider Interface
 * (Gnome Accessibility Project; http://developer.gnome.org/projects/gap)
 *
 * Copyright 2001, 2002 Sun Microsystems Inc.,
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <X11/XKBlib.h>

static	Display *display;
static  Window flash_window = None;

static void
visual_bell_notify (XkbAnyEvent *xkb_ev)
{
	Window root;
	int width, height;
	root = RootWindow (display, DefaultScreen (display));
	width = DisplayWidth (display, DefaultScreen (display));
	height = DisplayHeight (display, DefaultScreen (display));
	if (flash_window == None)
	{
		flash_window = XCreateSimpleWindow (display, root,
						    0, 0, width, height,
						    0, 0L, 0L);
		XSelectInput (display, flash_window, ExposureMask);
		XMapWindow (display, flash_window);
	}
	else
	{
		/* just draw something in the window */
		GC gc = XCreateGC (display, flash_window, 0, NULL);
		XSetForeground (display, gc,
				WhitePixel (display, DefaultScreen (display)));
		XFillRectangle (display, flash_window, gc,
				0, 0, width, height);
		XSetForeground (display, gc,
				BlackPixel (display, DefaultScreen (display)));
		XFillRectangle (display, flash_window, gc,
				0, 0, width, height);
	}
	XFlush (display);
}

int main (int argc, char **argv)
{
	XEvent xev;
	int ir, xkb_base_event_type, reason_return;
	char *display_name = getenv ("DISPLAY");

	if (!display_name) display_name = ":0.0";
	
	display = XkbOpenDisplay (display_name,
				  &xkb_base_event_type,
				  &ir, NULL, NULL, &reason_return);
	if (!display)
	{
		fprintf (stderr, "Could not connect to display! (%d)\n",
			 reason_return);
		exit (-1);
	}
	
	XkbSelectEvents (display,
			 XkbUseCoreKbd,
			 XkbBellNotifyMask,
			 XkbBellNotifyMask);

	/* comment this out to prevent bell on startup */
	XkbBell (display, None, 100, None);

	while (1)
	{
		XNextEvent (display, &xev);
		if (xev.type == Expose)
		{
			XExposeEvent *exev = (XExposeEvent *) &xev;
			if (exev->window == flash_window)
			{
				XDestroyWindow (display, flash_window);
				flash_window = None;
                                /* discard pending bells */
				XSync (display, True); 
				XFlush (display);
			}
		}
		else if (xev.type == xkb_base_event_type)
		{
			XkbAnyEvent *xkb_ev = (XkbAnyEvent *) &xev;
			
			switch (xkb_ev->xkb_type)
			{
			case XkbBellNotify:
				/* flash something */
				visual_bell_notify (xkb_ev);
				break;
			default:
			}
		}
	}
}