The compose key feels mandatory for anyone who wants to type their native langauge on an US-english layout. The combination[0] is "Compose--." though: –

[0]: https://en.wikipedia.org/wiki/Compose_key#Common_compose_com...

“Compose--.” produces an en dash, not an em dash. An em dash is produced by “Compose---”.

Source:

  grep -e DASH /usr/share/X11/locale/*/Compose

As it should be. I wish this convention were present across more software, “-“ “- -“ and “- - -“ should be the UI norm for entering proper dashes in text input controls.

Most software handles this fine if you configure your compositor to use a compose key.

Whoops, yep that's the one

[As an English typer] Where is this compose key on my keyboard?

(This is a vaguely Socratic answer to the question of why the compose key is not more often used.)

It’s not mapped to any key by default. A common choice is the right alt key.

I wrote a short guide about it last year: https://whynothugo.nl/journal/2024/07/12/typing-non-english-...

My personal preference is the capslock key. I'm not using it for anything anyway

In Vim it's Ctrl+K. ;)

As per the wiki article someone else listed — the compose key was available on keyboards back in the 1980s (notably it was invented only 5 years after the Space Cadet keyboard was invented!).

Some DOS applications did have support for it. The reason it wasn't included is baffling, and it's especially baffling to me that other operating systems never adopted it, simply because

    compose a '

is VASTLY more user friendly to type than:

    alt-+
    1F600

which I have met some windows users who memorize that combo for things like the copyright symbol (which is simply:)

    compose o c