Using Xnest to play with window managers

_{This post was originaly posted some 9 or 10 years ago}

Often times we want to test different things without messing up our existing X11 sessions. Such tests are the window manager ones. You want to tweak your manager to your liking but you don’t want to restart your current session. Xnest is the tool that you need to know. Xnest allows one to connect to existing xservers and emulating a client connection. In laments terms you can run a window manager inside a window.

Configuring xinit

Just like you would normally do, we have to make our xinit to act to our likings. Setting up backgrounds, choosing window managers etc. However since you might already have a local .xinitrc file we will create a new one. Here is how our looks like

------~/.xinitrc.nest-------
#!/bin/sh
# $Xorg: xinitrc.cpp,v 1.3 2000/08/17 19:54:30 cpqbld Exp $
# $OpenBSD: xinitrc.cpp,v 1.13 2006/01/21 22:12:13 matthieu Exp $
userresources=$HOME/.Xresources
usermodmap=$HOME/.Xmodmap
sysresources=/usr/X11R6/lib/X11/xinit/.Xresources
sysmodmap=/usr/X11R6/lib/X11/xinit/.Xmodmap
MCOOKIE=deadbeef

display=$(ls /tmp/.X*-lock|wc -l|awk '{print $1}')
DISPLAY=:$display.0
xauth add $(hostname)/unix${DISPLAY} . $MCOOKIE
xauth add localhost/unix${DISPLAY} . $MCOOKIE

export DISPLAY
xsetroot -cursor_name left_ptr
feh -F -Z --bg-scale  ~/.fvwm/echothrust.jpg
xterm -ls -name XTBIG &
# merge in defaults and keymaps

if [ -f $sysresources ]; then
    /usr/X11R6/bin/xrdb -merge $sysresources
fi

if [ -f $sysmodmap ]; then
    /usr/X11R6/bin/xmodmap $sysmodmap
fi

if [ -f $userresources ]; then
    /usr/X11R6/bin/xrdb -merge $userresources
fi

if [ -f $usermodmap ]; then
    /usr/X11R6/bin/xmodmap $usermodmap
fi

for fontpath in `grep FontPath /etc/X11/xorg.conf |awk '{print $2}'|sed -e 's/"//g'`;
do
	xset +fp ${fontpath}
done
	xset fp rehash
feh -F -Z --bg-scale  ~/.fvwm/echothrust.jpg
exec fvwm  -display $DISPLAY
xauth remove $(hostname)/unix${DISPLAY} localhost/unix${DISPLAY}

------~/.xinitrc.nest-------

Tune this to your liking.

Starting Xnest

Now to nasty part is to start the nested X. Change this to the desired display.

xinit .xinitrc.nest -- /usr/X11R6/bin/Xnest -full -dept 24 :2