Path: utzoo!attcan!uunet!husc6!bloom-beacon!EXPO.LCS.MIT.EDU!jim
From: jim@EXPO.LCS.MIT.EDU (Jim Fulton)
Newsgroups: comp.windows.x
Subject: Re: what's wrong with this program? (X11)
Message-ID: <8807221850.AA26376@EXPO.LCS.MIT.EDU>
Date: 22 Jul 88 18:50:29 GMT
References: <12080@duke.cs.duke.edu>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: X Consortium, MIT Laboratory for Computer Science
Lines: 29


> [describes mapping window and drawing without waiting for an expose event]

You *must* select for ExposureMask on the window and then wait for an Expose 
event before drawing.  This is to allow the window manager to grab the 
Map request, ask the user to size and place the window (if appropriate),
and then do the real map.  For example,

        pw = XCreateSimpleWindow(dpy, rootw, 0, 0,
                width / 4, height / 4,
                BORDER, white_pixel, black_pixel);
	XSelectInput (dpy, pw, ExposureMask);
	XMapWindow (dpy, pw);

	...

        /* wait for exposure */
        while (1) {
            XEvent event;

            XWindowEvent (dpy, pw, ExposureMask, &event);
            if (event.type == Expose) break;
        }

If you want to specify events later, then you can call XSelectInput again.


Jim Fulton
MIT X Consortium