xmodmap keybindings don't work

Question

I am trying to use Xmodmap to add some german diareses/umlauts to my keyboard, but Xmodmap is not working with them (but is with other remappings).

I am following this guide: German Umlauts on US Keyboard in X (Ubuntu 10.04).

Xmodmap

I have added this to my ~/.Xmodmap:

keysym a = a A adiaeresis Adiaeresis
keysym o = o O odiaeresis Odiaeresis
keysym u = u U udiaeresis Udiaeresis
keysym s = s S ssharp ssharp

xev

However it doesn't work. Here's the output from xev when I press o, hold down AltGr, press o, press x:

KeyPress event, serial 34, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 642618, (108,138), root:(173,190),
    state 0x10, keycode 32 (keysym 0x6f, o), same_screen YES,
    XLookupString gives 1 bytes: (6f) "o"
    XmbLookupString gives 1 bytes: (6f) "o"
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 642644, (108,138), root:(173,190),
    state 0x10, keycode 32 (keysym 0x6f, o), same_screen YES,
    XLookupString gives 1 bytes: (6f) "o"
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 643792, (108,138), root:(173,190),
    state 0x10, keycode 108 (keysym 0xfe03, ISO_Level3_Shift), same_screen YES,
    XKeysymToKeycode returns keycode: 92
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 645365, (108,138), root:(173,190),
    state 0x90, keycode 32 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 645409, (108,138), root:(173,190),
    state 0x90, keycode 32 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 647660, (108,138), root:(173,190),
    state 0x90, keycode 53 (keysym 0xd7, multiply), same_screen YES,
    XLookupString gives 2 bytes: (c3 97) "×"
    XmbLookupString gives 2 bytes: (c3 97) "×"
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 647722, (108,138), root:(173,190),
    state 0x90, keycode 53 (keysym 0xd7, multiply), same_screen YES,
    XLookupString gives 2 bytes: (c3 97) "×"
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x4e00001,
    root 0x8e, subw 0x0, time 650223, (108,138), root:(173,190),
    state 0x90, keycode 108 (keysym 0xfe03, ISO_Level3_Shift), same_screen YES,
    XKeysymToKeycode returns keycode: 92
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

You'll note that pressing AltGr is interpreted as ISO_Level3_Shift, and when that and x is pressed, I get keysym 0xd7, multiply, i.e. ×, which is set as my 3rd level for x. So AltGr works.

$ xmodmap -pke | grep 53
keycode  53 = x X x X multiply approximate

However when I press o I get keysym 0x0, NoSymbol, despite my 3rd level set up:

$ xmodmap -pke | grep 32
keycode  32 = o O odiaeresis Odiaeresis

Same thing happens when I try to use AltGr + (a|u|s).

Xmodmap works for other remappings

Since my PgUp key on my laptop is small, I have remapped the num pad + to by Page Up in my ~/.Xmodmap, and that works fine. So my XModmap file is being (partially) read.

Why does my reassigments to o/a/u not work?

I am using Ubuntu 14.0.1 trusty with Ubuntu Unity.

Answer 1

Preliminary note: it appears that xmodmap has recently changed; old settings won't work.

For your case, look at the number of values for keycode 53 (6 values: x X x X multiply approximate), which works, and for keycode 32 (4 values: o O odiaeresis Odiaeresis), which doesn't work.

ISO_Level3_Shift will select the 5th or 6th value, but they are not set for keycode 32 in your case. Hence the keysym 0x0, NoSymbol result.

What you need is:

keysym a = a A a A adiaeresis Adiaeresis
keysym o = o O o O odiaeresis Odiaeresis
keysym u = u U u U udiaeresis Udiaeresis
keysym s = s S s S ssharp ssharp

But it may better to use XKB directly (example).

Answer 2

To make the right Alt key work as Alt Gr, it needs to be mapped to Mode_switch instead of ISO_Level3_Shift, by adding the line

keycode 108 = Mode_switch

to ~/.Xmodmap:

keycode 108 = Mode_switch
keycode  38 = a A adiaeresis Adiaeresis
keycode  30 = u U udiaeresis Udiaeresis
keycode  32 = o O odiaeresis Odiaeresis
keycode  39 = s S ssharp

If you want the umlauts on the keys they have on the German keyboard, use:

keycode 108 = Mode_switch
keycode 48 = apostrophe quotedbl adiaeresis Adiaeresis
keycode 47 = semicolon colon odiaeresis Odiaeresis
keycode 34 = bracketleft braceleft udiaeresis Udiaeresis
keycode 20 = minus underscore ssharp

(You could combine them, of course.)