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From: gjw@SPURR.WR.USGS.GOV (Gregory J. Woodhouse)
Newsgroups: comp.windows.x
Subject: What am I doing wrong?
Message-ID: <9011201930.AA01212@spurr.wr.usgs.gov>
Date: 20 Nov 90 19:30:51 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 52


Hi, I've got another (presumably) naive question for you.  I use the following
routine to read the window ID of the main window of another process from a
property.  My purpose in doing so is so that I can use XSendEvent.  The
problem is that XInternAtom returns None, even though the slave process
should have created the property already.  Here's the code:

/*============================================================================*
 *                               fetch_win                                    *
 *============================================================================*/

 Bool fetch_win(display, sl_winp)
 Display *display;
 Window *sl_winp;	/* RETURN */

 {	/* fetch slave window ID from display manager */
	int status;
	Window rootwindow;
	Atom slwin_atom;

	/* These pointers are used for return values from XGetWindowProperty */
	int *actual_format;
	Atom *actual_type;
	unsigned long *nitems;
	unsigned long *bytes_after;
	unsigned char **data;

	rootwindow = RootWindow(display, DefaultScreen(display));
	slwin_atom = XInternAtom(display, PROP_NAME, True);
	/* only if exists -- this end reads the property */

	if (slwin_atom == (Atom) None) {
		perror("master: XInternAtom");
		return(False);
	} else  
		status = XGetWindowProperty(display, rootwindow, slwin_atom, 0L,
				1L, False, XA_WINDOW, actual_type, actual_format,
				nitems, bytes_after, data);

	if (*actual_format != 32 || *actual_type != XA_WINDOW || *nitems != 1L) {
		perror("master: property format");
		return(False);
	}
	if (status != Success) {
		(void) fprintf(stderr, "%s: XGetWindowProperty failed", progname);
		return(False);
	}

	/* All went well. */
	sl_winp = (Window *) data[0];
	return(True);
}