/*****************************************************************************/
/**                   Copyright 1991 by Andreas Stolcke                     **/
/**               Copyright 1990 by Solbourne Computer Inc.                 **/
/**                          Longmont, Colorado                             **/
/**                                                                         **/
/**                           All Rights Reserved                           **/
/**                                                                         **/
/**    Permission to use, copy, modify, and distribute this software and    **/
/**    its documentation  for  any  purpose  and  without  fee is hereby    **/
/**    granted, provided that the above copyright notice appear  in  all    **/
/**    copies and that both  that  copyright  notice  and  this  permis-    **/
/**    sion  notice appear in supporting  documentation,  and  that  the    **/
/**    name of Solbourne not be used in advertising                         **/
/**    in publicity pertaining to distribution of the  software  without    **/
/**    specific, written prior permission.                                  **/
/**                                                                         **/
/**    ANDREAS STOLCKE AND SOLBOURNE COMPUTER INC. DISCLAIMS ALL WARRANTIES **/
/**    WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF    **/
/**    MERCHANTABILITY  AND  FITNESS,  IN  NO  EVENT SHALL ANDREAS STOLCKE  **/
/**    OR SOLBOURNE BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL    **/
/**    DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA   **/
/**    OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER    **/
/**    TORTIOUS ACTION, ARISING OUT OF OR IN  CONNECTION  WITH  THE  USE    **/
/**    OR PERFORMANCE OF THIS SOFTWARE.                                     **/
/*****************************************************************************/
/*
 * vroot.h -- Virtual Root Window handling header file
 *
 * This header file redefines the X11 macros RootWindow and DefaultRootWindow,
 * making them look for a virtual root window as provided by certain `virtual'
 * window managers like swm and tvtwm. If none is found, the ordinary root
 * window is returned, thus retaining backward compatibility with standard
 * window managers.
 * The function implementing the virtual root lookup remembers the result of
 * its last invocation to avoid overhead in the case of repeated calls
 * on the same display and screen arguments. 
 * The lookup code itself is taken from Tom LaStrange's ssetroot program.
 *
 * Most simple root window changing X programs can be converted to using
 * virtual roots by just including
 *
 * #include <X11/vroot.h>
 *
 * after all the X11 header files.  It has been tested on such popular
 * X clients as xphoon, xfroot, xloadimage, and xaqua.
 * It also works with the core clients xprop, xwininfo, xwd, and editres
 * (and is necessary to get those clients working under tvtwm).
 * It does NOT work with xsetroot; get the xsetroot replacement included in
 * the tvtwm distribution instead.
 *
 * Andreas Stolcke <stolcke@ICSI.Berkeley.EDU>, 9/7/90
 * - replaced all NULL's with properly cast 0's, 5/6/91
 * - free children list (suggested by Mark Martin <mmm@cetia.fr>), 5/16/91
 * - include X11/Xlib.h and support RootWindowOfScreen, too 9/17/91
 *
 * Jamie Zawinski <jwz@jwz.org>, 28-Apr-1997
 * - use ANSI C
 *
 * Jamie Zawinski <jwz@jwz.org>, 3-Sep-2003
 * - if the environment variable "XSCREENSAVER_WINDOW" is set, use that
 *   as the root window instead of searching for __SWM_VROOT.
 */

#ifndef _VROOT_H_
#define _VROOT_H_
#define _XSCREENSAVER_VROOT_H_

#if !defined(lint) && !defined(SABER)
static const char vroot_rcsid[] =
    "#Id: vroot.h,v 1.5 2003/09/04 01:04:38 jwz Exp #" "\n"
    "#Id: vroot.h,v 1.4 1991/09/30 19:23:16 stolcke Exp stolcke #";
#endif

#include <X11/X.h>
#include <X11/Xatom.h>
#include <X11/Xlib.h>

static Window
#ifdef __STDC__			/* ANSIfication added by jwz, to avoid superfluous warnings. */
VirtualRootWindowOfScreen(Screen * screen)
#else				/* !__STDC__ */
VirtualRootWindowOfScreen(screen)
Screen *screen;
#endif /* !__STDC__ */
{
    static Screen *save_screen = (Screen *) 0;
    static Window root = (Window) 0;

    if (screen != save_screen) {
	Display *dpy = DisplayOfScreen(screen);
	Atom __SWM_VROOT = None;
	int i;
	Window rootReturn, parentReturn, *children;
	unsigned int numChildren;

	/* first check for a hex or decimal window ID in the environment */
	const char *xss_id = getenv("XSCREENSAVER_WINDOW");
	if (xss_id && *xss_id) {
	    unsigned long id = 0;
	    char c;
	    if (1 == sscanf(xss_id, " 0x%lx %c", &id, &c) ||
		1 == sscanf(xss_id, " %lu %c", &id, &c)) {
		root = (Window) id;
		save_screen = screen;
		return root;
	    }
	}

	root = RootWindowOfScreen(screen);

	/* go look for a virtual root */
	__SWM_VROOT = XInternAtom(dpy, "__SWM_VROOT", False);
	if (XQueryTree(dpy, root, &rootReturn, &parentReturn, &children, &numChildren)) {
	    for (i = 0; i < (int)numChildren; i++) {
		Atom actual_type;
		int actual_format;
		unsigned long nitems, bytesafter;
		Window *newRoot = (Window *) 0;

		if (XGetWindowProperty(dpy, children[i],
				       __SWM_VROOT, 0, 1, False, XA_WINDOW,
				       &actual_type, &actual_format,
				       &nitems, &bytesafter,
				       (unsigned char **) &newRoot) == Success && newRoot) {
		    root = *newRoot;
		    break;
		}
	    }
	    if (children)
		XFree((char *) children);
	}

	save_screen = screen;
    }

    return root;
}

#undef RootWindowOfScreen
#define RootWindowOfScreen(s) VirtualRootWindowOfScreen(s)

#undef RootWindow
#define RootWindow(dpy,screen) VirtualRootWindowOfScreen(ScreenOfDisplay(dpy,screen))

#undef DefaultRootWindow
#define DefaultRootWindow(dpy) VirtualRootWindowOfScreen(DefaultScreenOfDisplay(dpy))

#endif /* _VROOT_H_ */
