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Is there any way to bind a command to a key combination like AltGr-f?

The reason I ask is the following: I use the “US international” keyboard layout (on Linux), which remaps the right Alt key to AltGr (aka Level3 shift), so that I can type certain accented characters I need. But this keyboard layout also has the nice side-effect of making some new (and very convenient) key combinations available; for instance, AltGr-t inserts þ, which I never use, so I can rebind it to something else. The problem is that AltGr-f inserts an f, and not some useless symbol, so I can't bind that key to a command (similar issue with the characters g, h, b). I know I could use xmodmap to assign some random symbol to AltGr-f, but is there a pure Emacs way to do that?

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    I suspect that's not possible since Emacs just receives keysyms. So, since AltGr is no modifier (it enables the third level map), Emacs just gets the generated keysyms like þ which you can inspect with F1 k þ.
    – wasamasa
    Commented Nov 11, 2014 at 22:15
  • Actually, X provides both the keysym and the keycode to the client, but I don't know if Emacs can bind a command to a keycode. It's certainly possible to remap AltGr-f to a different keysym at the xkb level.
    – jch
    Commented Nov 11, 2014 at 23:15
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    Shouldn't you add a tag for the platform you're on? AltGr obviously doesn't apply to OS X, and the way the OS affects the way AltGr is generated/intercepted/caught might be different on Linux, Windows and other operating systems.
    – Erik Kaplun
    Commented Nov 12, 2014 at 0:48
  • @wasamasa That sounds right, but on the other hand there is the key-translation-map and similar stuff that seem to work at a lower level and might know about AltGr.
    – Augusto
    Commented Nov 29, 2014 at 19:36
  • Not an answer but hopefully some approximation -- use the compose key. That is after doing (something like) $ setxkbmap -option compose:menu the menu key will now behave like a compose key After that use something like pointless-xcompose as a starting point to set up your own compose sequences.
    – Rusi
    Commented Jan 17, 2015 at 15:10

2 Answers 2

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Yes and no.

No. AltGr isn't a modifier known to Emacs.

Yes. Emacs knows more modifiers than Control, Meta and Shift: Hyper and Super.

What you have to do is tell our OS or window system that the key/scan code generated by pressing the key labelled [AltGr] is "Super". I haven't done that in a while, but inspecting my own xkb (for X11) configuration this would probably look like this:

key <RALT> { [ Super_L ] };
key <SUPR> { [ NoSymbol, Super_L ] };
modifier_map Mod4 { <SUPR> };

Unfortunately you cannot just drop that into a file and toggle a switch somewhere and it just works. Xkb is a monstrosity and you will have to learn how to tame it. Unfortunately no decent user documentation exists.

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This is an old question and I use the CLI Emacs over X, but this might still be helpful for someone. I don't know of a pure Emacs way but I know what I did to fix this.

I prefer UK layout, but keystrokes like M-x are difficult. loadkeys loads keymaps on the fly.

Messing around, I found the linux-with-two-alt-keys.inc file. For a UK layout with both two Alt keys:

$ loadkeys /usr/share/kbd/keymaps/i386/qwerty/uk.map.gz /usr/share/kbd/keymaps/i386/include/linux-with-two-alt-keys.inc

I could have stopped and chucked that in .bash_profile, but I am petty.

I tried editing /etc/rc.conf which alters the bootup keymap, but I was couldn't get both keymaps recognised.

(Note, I am on Void Linux; the file changes between distros. /etc/vconsole.conf on Fedora, /etc/rc.local on Ubuntu, I believe)

So I gave up and made my own keymap. Less scary than it sounds. I copied and decompressed uk.map.gz, adding:

keycode 100 = Alt

Before compressing, saving as /usr/share/kbd/keymaps/i386/qwerty/custom.map.gz, and editing rc.conf:

KEYMAP=custom

Both Alt and AltGr now both work as Alt in CLI Emacs.

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