Using `setxkbmap`
After using Ubuntu for a number of years, I was quite accustomed to customizing
my desktop experience using the GUI tools provided by GNOME. In the past year, I
have been using awesome, a tiling window manager. Some things can still be
configured using the gnome-control-center application, but I have also been
experimenting more with using the underlying technologies that GNOME uses behind
the scenes.
Today, I wanted to change my keyboard settings so I can type moderately fancy
letters like éàîöŭ. There are two common ways to approach this, and which you
choose probably depends on the frequency you need such characters. First, you
can use a compose key, so that you type a combination like Compose ' e to
get é. Second, you can use dead keys, where typing one of the prefixes
like ' enters a state where you can type another letter like any of aiueo to
get áíúéó respectively or you can type ' again to get that actual single
quote character. Since I don’t foresee needing to type that much using these
characters, I went with a compose key. Additionally, I will also describe how to
enable dead keys for a US keyboard.
From what I’ve learned, the easiest way to accommodate this is to use the
existing Debian keyboard config files. You can read about the semantics in the
keyboard(5) manpage. The system wide file is /etc/default/keyboard, but it
appears ~/.keyboard should also work. This file is a list of variables that
looked like this by default for me:
# KEYBOARD CONFIGURATION FILE
# Consult the keyboard(5) manual page.
XKBMODEL="pc105"
XKBLAYOUT="us"
XKBVARIANT=""
XKBOPTIONS=""
BACKSPACE="guess"
For enabling dead keys, it appears as simple as setting XKBVARIANT="intl". For
choosing a compose key, we would like to modify XKBOPTIONS. There are a lot
options to choose from, but the ones relevant to us are the following:
$ grep "compose:" /usr/share/X11/xkb/rules/xorg.lst
compose:ralt Right Alt
compose:lwin Left Win
compose:lwin-altgr 3rd level of Left Win
compose:rwin Right Win
compose:rwin-altgr 3rd level of Right Win
compose:menu Menu
compose:menu-altgr 3rd level of Menu
compose:lctrl Left Ctrl
compose:lctrl-altgr 3rd level of Left Ctrl
compose:rctrl Right Ctrl
compose:rctrl-altgr 3rd level of Right Ctrl
compose:caps Caps Lock
compose:caps-altgr 3rd level of Caps Lock
compose:102 <Less/Greater>
compose:102-altgr 3rd level of <Less/Greater>
compose:paus Pause
compose:prsc PrtSc
compose:sclk Scroll Lock
I chose to use Right Alt. In addition, I prefer to change the semantics of the
capslock key, and there are several options for that. Ultimately, I set
XKBOPTIONS="compose:ralt,caps:ctrl_modifier" in ~/.keyboard.
Going Further
I decide while I was playing with keyboard configurations, I would attempt to
fix a minor inconvenience I’ve experienced. I primarily use a wireless keyboard
to type on my laptop. The wireless and internal keyboards have slightly
different layouts. The internal keyboard has the super key to the left of the
spacebar whereas the wireless keyboard has the alt key in that position. Thus,
I’d like to switch these keys around on only one device. This cannot be
achieved using the ~/.keyboard file as far as I can tell.
setxkbmap is a utility that can set the same parameters as the variables
accepted by the ~/.keyboard file. More importantly, setxkbmap can configure a
specific X device using the -device flag. We can invoke setxkbmap inside the
~/.xinitrc script that will be executed by any X session.
First, we use xinput to print the available input devices:
$ xinput
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ bcm5974 id=11 [slave pointer (2)]
⎜ ↳ Logitech M570 id=12 [slave pointer (2)]
⎜ ↳ Logitech K400 Plus id=13 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ Power Button id=6 [slave keyboard (3)]
↳ Video Bus id=7 [slave keyboard (3)]
↳ Power Button id=8 [slave keyboard (3)]
↳ Sleep Button id=9 [slave keyboard (3)]
↳ Apple Inc. Apple Internal Keyboard / Trackpad id=10 [slave keyboard (3)]
↳ Logitech K400 Plus id=14 [slave keyboard (3)]
We want to select two of the slave keyboards. There’s probably a better way to
extract the device id, but I used grep and sed like so:
kb1=$(xinput | grep -E "Logitech K400 Plus.+keyboard" | sed -E "s/^.*id=([0-9]+).*$/\1/")
kb2=$(xinput | grep -E "Apple Inc.+keyboard" | sed -E "s/^.*id=([0-9]+).*$/\1/")
I prefer having super, which I use more often, close to the space bar, so I want
to swap them on the wireless keyboard. In addition to the other values from the
XKBOPTIONS variable from our ~/.keyboard, I can use the
altwin:swap_lalt_lwin option to achieve the desired behavior.
There are two remaining details. Whereas the ~/.keyboard file accepts a
comma-separated list of options, we must pass each option as a separate flag to
setxkbmap. Additionally, it seems we must first clear all the options using
-option "" before we can set device-specific options. Otherwise both devices
end up with the union of their options it seems.
Thus finally, my ~/.xinitrc script looks like so:
kb1=$(xinput | grep -E "Logitech K400 Plus.+keyboard" | sed -E "s/^.*id=([0-9]+).*$/\1/")
kb2=$(xinput | grep -E "Apple Inc.+keyboard" | sed -E "s/^.*id=([0-9]+).*$/\1/")
setxkbmap -device $kb1 -layout us -option "" -option compose:ralt \
-option caps:ctrl_modifier \
-option altwin:swap_lalt_lwin
setxkbmap -device $kb2 -layout us -option "" -option compose:ralt \
-option caps:ctrl_modifier
Making Things Work
With the ~/.xinitrc script in place, you can either execute it manually or log
in again. It should now be possible to use the compose key in every application.
Well, everything except Emacs it seems. This issue seems to date back ten
years1, rediscovered on the emacs-devel list five years ago2 and allegedly
fixed3 around version 24.4. However, when I press the compose key in Emacs
25.2.2 graphical window (not in a terminal), the compose key does not work and
instead I get a message that <Multi_key> is undefined.
The simplest solution is to create the following wrapper script somewhere early in your $PATH like ~/.local/bin/emacs:
#!/bin/bash
env -u XMODIFIERS /usr/bin/emacs $@