They all do this, this is the big problem in why we're stuck with crappy text areas and content editable. The JavaScript keyboard API was designed for Americans. It does not know about combining accent keys, IMEs, etc.

There is also this inconsistency that's irritating. I'm typing on a qwertz keyboard and in Primrose, z is z (instead of y). But all 'special' characters are qwerty layout.

Great result for a weekend still :)

(it also hijacks ctrl+f/ctrl+c/… anywhere on the website and just inserts the letter instead of calling the browser function)

All this makes me wonder whether this is the right approach and whether this couldn't be done with a lot less hassle with CSS formatting.

Well, the problem with CSS formatting is that it doesn't composite well with 3D scenes in WebGL contexts. That's the ultimate goal here, to have 3D objects in a VR application with code editor surfaces (for which I have another project running as well).

My code already uses a rudimentary code page system, just because it's impossible to go from DOM keyCodes to the correct text for even US keyboards, so in the long run this should be easily fixable.