Using both alt flags on one key

Does anyone know of a case where it’s useful to send both left and right alt keycodes simultaneously? I’m curious because it looks like QMK and Kaleidoscope both use five flag bits for adding modifiers to keyboard keycodes, but while Kaleidoscope has four left mods and one for right alt, QMK uses four bits to encode the different modifiers and the fifth bit to indicate if the modifiers will be treated as right mods instead of left mods. This seems pretty much equivalent in almost all cases, unless there’s something that uses a combination of the two alt keys (i.e. Alt + AltGr + X). I’m just curious, and wondering if there is anything that would make use of that combination.

IIRC, a small handful of games make the distinction.

Also, it would be worthwhile to check with the Plover community because steno might make use of a distinction between those keys.

A distinction between the two alt keys is a prerequisite for what I’m getting at (and certainly exists in many cases, even system-wide), but the core of my question is, “Can anyone think of a reason to have a keymap entry that uses both alt modifier flags (on the same key)?”

Plover is another good suggestion; I hadn’t thought of that. However, since the whole point of a stenograph is to use few keys and rapid chording, I doubt very much that it makes sense to have dedicated special keys with modifier combos.

Ah, okay.

In that case, yes I can think of a valid use for a Alt+AltGr+x combo.


  1. The Alt layer can be thought of as a second Shift layer.
  2. The AltGr layer is typically used for glyphs which are not used in the native language of the user.
  3. A Tolkien lore historian whose native language is English, but who needs to type Tengwar and Cirth.

In the above case, Tengwar goes on the AltGr layer, the AltGr+Shift layer is used for the less common Tengwar glyphs, and Cirth goes on the AltGr+Alt layer.

From a far more practical standpoint, I have used Ukelele to do the same thing for my laptop (English on the base and Shift layers, Greek on the AltGr and AltGr+Shift layers, culminating in esoteric Unicode mathematical glyphs on the AltGr+Alt layer).


Thanks for the reply; that’s a bit of a custom configuration corner case, but still a possible reason to prefer the Kaleidoscope system to QMK’s mod flags.

As a followup question, do you see it as useful to be able to have an in-firmware layer where all (or nearly all) the keys have the Alt + AltGr modifier flags applied (so you could toggle a layer on and not need to hold modifier keys)? Or have you already done so (I’m not sure from reading your message)?

My above example was from before I discovered Kaleidoscope and QMK, so my usage of “layer” in said above example is Ukelele’s concept of a layer (have to hold down modifier key(s) to access that layer).

Using modifier keys to toggle a layer on/off would be far more user friendly.

I know that the portable keyboard layout mod of autohotkey by default uses left and right alt to toggle between layouts, but that was mostly to avoid common shortcuts etc.

So not really, no. In fact my example would be a reason to avoid using both alt flags on one key if anything.

Maybe some odd layering for alt character codes using the numberpad? One alt gives you the regular alt character codes, both alts gives you access to your own custom ordering of character codes? You’d at least know that it probably wouldn’t cause any interference the way that it could with other modifiers (unless you have PKL), and even with monster hands like mine it’s very tricky to do on a normal layout keyboard (although holding both alts with the left hand does work but looks and feels as stupid as fuck), but it could be useful for ergonomic keyboards, and could be a case where single key double alt would be useful.

(on reading, it’s a pretty similar case to what @cal was saying)

Thanks for the answer. I feel like I should point out that I wasn’t so much interested in what could be done, theoretically, with both alt keycodes on the same key. After all, both QMK and Kaleidoscope have ways to configure a key with both alt codes on one key. The tradeoff that exists is that Kaleidoscope can have both alts and a printable keycodes on one key (QMK can’t), but QMK can have any of the other three right-side mods (but no left mods) and a printable keycode on one key (Kaleidoscope can’t).

I was trying to decide which system I preferred in my experimental Kaleidoscope fork. So my real question, when I get right down to it, should have been, “Which of these two alternatives is less limiting, in general?” I’ve basically settled on using Kaleidoscope’s mod flags as slightly superior, but it’s still not obviously better.