Compose key on GNU/Linux (how to type smart quotes)

For the longest time I wanted to be able to write “smart quotes” from my GNU/Linux machines¹. I managed to set this up on Fedora quite easily from Gnome’s settings (or the Tweak tool?) by setting the Compose key. The problem is that I rarely use Fedora, and most of my computing is done on machines that use dwm and GNU Guix System, so I need a solution that is Desktop-Environment–agnostic.

This works if you’re using an X server. I don’t use any Wayland WMs so I don’t know what the solution is for that.

To be able to write characters that are not on our keyboards we could use the “Compose key”. To use it, we need to tell the computer what it is. We’ll use xmodmap for that, which will require a key name. That can be obtained with xev.

Fire up an xev window instance from your terminal and press the key you want to use as the future Compose key. The output should look like this:

KeyRelease event, serial 32, synthetic NO, window 0x1c00001,
    root 0x3b7, subw 0x0, time 43382046, (1046,262), root:(1059,306),
    state 0x0, keycode 135 (keysym 0xff20, Menu), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

You need to extract the name of the key, in my case “Menu” (from this bit keycode 135 (keysym 0xff20, Menu)). After this, you can set your Compose key:

xmodmap -e "keysym Menu = Multi_key"

You’ll probably have a list of the available key combinations that use the Compose key in /usr/share/X11/locale/en_US.UTF-8/Compose (replace en_US.UTF-8 with your locale). If you’re using Guix, this path will look like this: $GUIX_PROFILE/share/X11/locale/en_US.UTF-8/Compose.

You can also define new sequences in the ~/.XCompose file, like the ones in the default configuration.

Important! Do not forget to use include "%L" at the top of your ~/.XCompose file, to make the default combinations available.

Now you’ll probably be able to type smart quotes using Compose + < (or Compose + >) and then ".