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From: smarks@eng.sun.COM (Stuart Marks)
Newsgroups: comp.windows.x
Subject: Re: Help, I can't get input focus under olwm
Message-ID: <9012180213.AA13153@trantor.Eng.Sun.COM>
Date: 18 Dec 90 02:13:41 GMT
References: <1990Dec13.221949.583@agate.berkeley.edu>
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 59


dc@caveat.berkeley.edu (Dave Cottingham) writes:

    Subject:  Help, I can't get input focus under olwm

    I have run into a peculiar problem using my favorite X application,
    XCONQ, on my shiny new Sparcstation.  I can't direct the input focus
    to XCONQ's window.

This is the canonical problem where the client program has failed to set
the "hints" on its window to tell the window manager that it is eligible to
receive the input focus.  There's a document called the ICCCM (Inter-Client
Communication Conventions Manual) that is an X Consortium standard.  (It's
available on the X11R4 tape or via FTP from expo.  It's also been reprinted
in O'Reilly Volume 0 and in Scheifler/Gettys 2nd ed.)  Among other things,
this document explains that conforming programs must set certain properties
on their top-level windows in order to inform the window manager about the
program's resource requirements.  One of these resources is the input
focus.

You've indicated that xconq is written entirely in Xlib.  For Xlib
programs, here's a way to set the proper hints to get the focus:

    #include <X11/Xutil.h>
    XWMHints wmhints;

    /* ... */

    wmhints.flags = InputHint;
    wmhints.input = True;
    XSetWMHints(dpy, win, &wmhints);
    /* ... */
    XMapWindow(dpy, win);


... where "win" is a top-level window.  You must do this for every
top-level window, i.e. every non-override-redirect window that is a child
of the root window.

    Could someone tell me how a window manager decides if a window should
    be allowed to take input focus? (yes, I'm that clueless)

First, the window manager reads the hints the client has set on the
window.  These hints determine the way the focus is actually set to the
window (e.g. the WM sets the focus to the window, or the WM asks the
client to take the focus).  This stuff is explained in the ICCCM.

Now, the user interface for moving the focus around is part of window
manager policy.  Olwm, for instance, gives you a choice of two focus
policies:  "click-to-type" mode, where you must click in a window or its
header to transfer the focus there, or "follow-mouse", where moving the
pointer into a window transfers the focus there.  Other window managers may
have other user interfaces for moving the focus from window to window.

s'marks

Stuart W. Marks			ARPA: smarks@eng.sun.com
Windows & Graphics Software	UUCP: sun!smarks
Sun Microsystems, Inc.