Xcompmgr

Xcompmgr is a simple compositor capable of rendering drop shadows and, with the use of the transset utility, primitive window transparency. Designed solely as a proof-of-concept, Xcompmgr is a lightweight alternative to Compiz and similar composite managers.

Because it does not replace any existing window manager, it is an ideal solution for users of lightweight window managers, seeking a more elegant desktop.

Installation

Before installing Xcompmgr, make sure you have installed and correctly configured Xorg. To make sure the Composite extension is enabled for the X Server, run:

$ xdpyinfo | grep Composite

Composite

If there is no output, add the Composite option to the Extensions section of xorg.conf:

/etc/X11/xorg.conf

Section "Extensions"
        Option  "Composite" "true"
EndSection

Xcompmgr can be installed with the package xcompmgr. For transparency also install the transset-df^AUR. See Xterm#Automatic transparency for an example.

Configuration

To load xcompmgr, simply run:

$ xcompmgr -c

To have it load at session start, add the following to xprofile:

xcompmgr -c &

Instead of -c you can experiment with the other switches to modify the drop-shadows or even enable fading. Below is a common example:

xcompmgr -c -C -t-5 -l-5 -r4.2 -o.55 &

For a full list of options, run:

$ xcompmgr --help

Window transparency

Although its practical use is limited, due to its slow performance, the transset-df utility can be used to set the transparency of individual windows.

To set the transparency of a program window, make sure the desired program is already running, then execute:

$ transset-df opacity

where opacity is a number between 0 and 1, 0 being transparent and 1 being opaque.

Once execution, the mouse cursor will transform to a cross-hair. Click a window and its transparency will change to the value specified. For example, transset-df 0.25 will set the target window to 25% opacity (75% transparency).

Tips and tricks

Start/Stop Xcompmgr on demand

This script allows easy (re)starting and stopping of the compositing manager.

~/.bin/comp

#!/bin/bash
#
# Start a composition manager.
# (xcompmgr in this case)

comphelp() {
    echo "Composition Manager:"
    echo "   (re)start: COMP"
    echo "   stop:      COMP -s"
    echo "   query:     COMP -q"
    echo "              returns 0 if composition manager is running, else 1"
    exit
}

checkcomp() {
    pgrep xcompmgr &>/dev/null
}

stopcomp() {
    checkcomp && killall xcompmgr
}

startcomp() {
    stopcomp
    # Example settings only. Replace with your own.
    xcompmgr -CcfF -I-.015 -O-.03 -D6 -t-1 -l-3 -r4.2 -o.5 &
    exit
}

case "$1" in
    "")   startcomp ;;
    "-q") checkcomp ;;
    "-s") stopcomp; exit ;;
    *)    comphelp ;;
esac

For ease of use, you can bind this script to a hot-key using, for example, Xbindkeys. This allows for fast restart or temporary composition removal if needed without interrupting other work.

Toggle Xcompmgr

Assign the following script to any hot-key:

#!/bin/bash

if pgrep xcompmgr &>/dev/null; then
    echo "Turning xcompmgr OFF"
    pkill xcompmgr &
else
    echo "Turning xcompmgr ON"
    xcompmgr -c -C -t-5 -l-5 -r4.2 -o.55 &
fi

exit 0

Troubleshooting

Background turns light gray briefly after logging in (e.g. in Openbox)

This is fixed by installing hsetroot and setting the background color by executing hsetroot -solid "#000000" (just type the code of the color you want instead of #000000) before xcompmgr. Alternatively, if xcompmgr is called prior to exec in ~/.xinitrc, you can change xcompmgr & to (sleep 1 && xcompmgr) & which will fork a subshell and allow xcompmgr to execute after your window manager has already started.

BadPicture request in awesome

If you get the following error in awesome:

 error 163: BadPicture request 149 minor 8 serial 34943
 error 163: BadPicture request 149 minor 8 serial 34988
 error 163: BadPicture request 149 minor 8 serial 35033

just install feh and restart awesome.

Screen not updating in awesome after resolution change

When using an external monitor, you may encounter problems when automatically changing display resolutions: a part of the screen becomes "stuck" and no longer updates itself. This problem occurs because of the initial resolution change (happening before Xcompmgr starts) as well as awesome setting the background via feh.

To fix it, you need to install hsetroot and put the following line in .xinitrc, just before xcompmgr:

hsetroot -solid "#000066"

(you can replace #000066 with your color of choice).