Making keyboard settings survives USB connections

As a developer and a vim user, I rely heavily on a good typing experience. I am constantly trying to improve it whether it is in becoming a better touch typist or using a better keyboard. About this, as stated before, I like to use the not so good French ISO-AZERTY-FR layout. As much as I like to stick with the default, some keys are purely not compatible with vim. I’m talking here about the key: ^ which is used in vim to get back to the first character of the line.

First of all, what is a dead key ? When you press one of these keys, nothing appears on the screen. The character appears only when you press a second key. Usually that second key outputs a character slightly modified by this dead key. On the French keyboard, its purpose is to type these characters: ê, î for ^..

The French keyboard have a few other dead keys such as ¨ or ` (the one triggered by AltGr-*). But these are not as important in vim as ` can also be triggered by AltGr-7 which is not a dead key.

Back to vim, in normal mode, you want to go back to the beginning of the line, then you have whether to hit twice ^ or hit ^ followed by space. That’s one key more than necessary so totally unacceptable. Let’s see how we can work around this.

XWindow has a keyboard variant to turn off dead keys which can be easily activated with this command:

$ setxkbmap -layout fr,fr -variant nodeadkeys, -option caps:escape,grp:ctrls_toggle

It sets two layouts for the current keyboard, one without and one with dead keys. One can switch between the two layouts by hitting the two control keys simultaneously. So having this setup by default is only a matter of having this command called when XWindow starts. It can be put in the .xsession or .xinitrc file for example.

So far so good, that works pretty well as long as you don’t need to plug a keyboard. Indeed as soon as you to it XWindow affects the default layout to this new keyboard and the magic command needs to be called again. Unfortunately this situation happens quite often when you use a laptop and carry it around to work with others or attend meetings for example.

The usually recommended way to solve this issue is to change the default keyboard options in the XWindow configuration file such as xorg.conf. But then that option will be applied to every single user of the computer which doesn’t make much sense in my opinion. Keyboard preferences is indeed a very personal matter and it should be possible to tweak it on a user level.

As easy it is to tweak the keyboard layouts at XWindow startup, there is no builtin way to do it when keyboards are plugged or unplugged. This is where the software inputplug comes in handy. That little tool listens to XInput events and triggers arbitrary scripts on any change.

For example, calling inputplug like this:

$ inputplug -c ~/bin/

will trigger the script ~/bin/ on any XInput event. That script could be something like:

#!/usr/bin/env bash

echo >&2 "$@"
event=$1 id=$2 type=$3

case "$event $type" in
'XIDeviceEnabled XISlaveKeyboard')
    setxkbmap $id -layout fr,fr -variant nodeadkeys, -option caps:escape,grp:ctrls_toggle

Here inputplug gives us three arguments:

  • the name of the event
  • its identifier
  • its type

Using these, we can filter out the event we’re interested in, in our case, a new keyboard event and react accordingly by setting up that new keyboard as we like.

With this little trick, we can carry on viming on our new keyboard, not being annoyed by these deadly dead keys !

Read more about inputplug on its github page.

August 29, 2022