[buug] selecting window managers from xdm: the solution

[Ian Zimmerman]

I asked: how can one select a window manager du jour when logging in
through xdm? (and not wdm or gdm or kdm)

The easy answer: modify /usr/X11R6/lib/X11/xdm/Xresources (which on my
Debian system is really /etc/X11/xdm/Xresources) like this

*** Xresources~ Thu Nov 15 22:55:05 2001
--- Xresources  Thu Nov 15 22:54:40 2001
***************
*** 10,15 ****
--- 10,17 ----
  xlogin*login.translations: #override \
        Ctrl<Key>R: abort-display()\n\
        <Key>F1: set-session-argument(failsafe) finish-field()\n\
+       <Key>F2: set-session-argument(wmaker) finish-field()\n\
+       <Key>F3: set-session-argument(sawfish) finish-field()\n\
        <Key>Delete: delete-character()\n\
        <Key>Left: move-backward-character()\n\
        <Key>Right: move-forward-character()\n\

Then, when you hit F2 or F3 in the xdm greeter, you'll be dropped in a
WindowMaker or sawfish session respectively.

Unfortunately, this didn't quite satisfy me, as your ~/.xsession
script is completely ignored this way; the system will just start the
window manager directly, bypassing the ~/.xsession script.  I have
some setup code there that I depend on:

#! /bin/bash

case $DISPLAY in
:0)
        if [ -f $HOME/.Xmodmap ]; then
                /usr/bin/X11/xmodmap $HOME/.Xmodmap
	fi ;;
esac

. /etc/profile
. $HOME/.bashrc

exec wmaker

So, the requirement was to pass the session argument from the greeter
down to ~/.xsession.  Like so often in Unix, the solution is at once
baroque and elegant:

Add an executable script linked to both /usr/local/bin/xsession-wmaker
and /usr/local/bin/xsession-sawfish, containing

#! /bin/sh
# a hack to enable flexible window manager flipping in xdm

oldpath=$PATH
PATH=/bin:/usr/bin

style=`basename $0 | sed -e 's/^xsession-//'`
echo $style > $HOME/.xsession_style
PATH=$oldpath
exec $HOME/.xsession

Modify Xresources as follows:

*** Xresources~ Thu Nov 15 22:55:05 2001
--- Xresources  Thu Nov 15 22:54:40 2001
***************
*** 10,17 ****
  xlogin*login.translations: #override \
        Ctrl<Key>R: abort-display()\n\
        <Key>F1: set-session-argument(failsafe) finish-field()\n\
!       <Key>F2: set-session-argument(wmaker) finish-field()\n\
!       <Key>F3: set-session-argument(sawfish) finish-field()\n\
        <Key>Delete: delete-character()\n\
        <Key>Left: move-backward-character()\n\
        <Key>Right: move-forward-character()\n\
--- 10,17 ----
  xlogin*login.translations: #override \
        Ctrl<Key>R: abort-display()\n\
        <Key>F1: set-session-argument(failsafe) finish-field()\n\
!       <Key>F2: set-session-argument(xsession-wmaker) finish-field()\n\
!       <Key>F3: set-session-argument(xsession-sawfish) finish-field()\n\
        <Key>Delete: delete-character()\n\
        <Key>Left: move-backward-character()\n\
        <Key>Right: move-forward-character()\n\

And modify ~/.xsession as follows:

*** .xsession~  Thu Nov 15 23:09:48 2001
--- .xsession   Thu Nov 15 23:09:27 2001
***************
*** 10,13 ****
  . /etc/profile
  . $HOME/.bashrc
  
! exec wmaker
--- 10,17 ----
  . /etc/profile
  . $HOME/.bashrc
  
! if [ ! -f $HOME/.xsession_style ]; then
!     echo wmaker > $HOME/.xsession_style
! fi
! 
! exec `cat $HOME/.xsession_style`

Voila.  It even remembers your last choice, using it as a default
until you hit the other function key :)

BTW, if it wasn't clear (I guess it wasn't :), I am looking for a job,
too.  (Sysadmin/webmaster/programer).

-- 
Ian Zimmerman, Oakland, California, U.S.A.
Hypocrisy, arrogance and manipulation: sure-fire ways to earn hatred.
GPG pub key: 433BA087 9C0F 194F 203A 63F7 B1B8 6E5A 8CA3 27DB 433B A087