unable to rebind right alt key with xmodmap

[noahlt]

I am trying to rebind my right Alt key as a Hyper key, so that I can make own keybindings that won't get in the way of my apps/WM. Unfortunately, I cannot seem to rebind this key.

After freshly logging in, if I run xev and press my right Alt key, I get this:

KeyPress event, serial 37, synthetic NO, window 0x2200001,
    root 0x13c, subw 0x0, time 50532932, (-1,160), root:(584,211),
    state 0x2000, 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

KeyRelease event, serial 37, synthetic NO, window 0x2200001,
    root 0x13c, subw 0x0, time 50533064, (-1,160), root:(584,211),
    state 0x2080, keycode 108 (keysym 0xfe03, ISO_Level3_Shift), same_screen YES,
    XKeysymToKeycode returns keycode: 92
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

But if I run xmodmap to try to rebind the key, it doesn't work:

$ xmodmap -e 'keycode 108 = x'

Pressing my right Alt key doesn't produce the 'x' character. Pressing my right Alt key inside of xev produces the following:

KeyPress event, serial 50, synthetic NO, window 0x4c00001,
    root 0x13c, subw 0x0, time 51429231, (178,59), root:(184,453),
    state 0x2000, keycode 108 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 50, synthetic NO, window 0x4c00001,
    root 0x13c, subw 0x0, time 51429452, (178,59), root:(184,453),
    state 0x2000, keycode 108 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

I can use xev to find the keycode for my Tab key and rebind it to 'x':

$ xmodmap -e 'keycode 23 = x'

and then pressing my Tab key results in the 'x' character, but it doesn't work for my right Alt key.

I've Googled and read the man pages, and I still don't know why I can't rebind my right Alt key. Any ideas?

Thanks in advance!

[Brandon Williams]

The process you used works just fine for me to remap my right Alt key. I notice that your right Alt key produces a different symbol than mine without the mapping. Yours produces ISO_Level3_Shift and mine produces Alt_R. This could be significant, but I'm not sure how. Sorry I can't be more helpful.

[humbug01]

Your Right-Alt key is set to select the third level key rather than as Alt_R as Brandon noticed. Mine was too and I just changed it in "System > Keyboard > Layouts tab > Options > Key to choose third level" to a different key and now it is Alt_R. Maybe this is the problem?

Best,

Steve

[noahlt]

Thanks humbug01! Thanks to Brandon, too, for pointing out that my Alt key wasn't producing Alt_R.

I went to Keyboard Preferences > Layouts > Layout Options and changed "Key to choose 3rd level" to "Right Alt key never chooses 3rd level". After I restarted my X session, xev shows that my right Alt key produces Alt_R instead of ISO_Level3_Shift, which allowed me to add Alt_R as a Mod3 modifier key using xmodmap.