How to enable Shift Lock? (Sticky shift key)

keyboard-layoutx11xkbxmodmap

I want to map one of my keys the shift lock key. In my understanding, the shift lock key is a kind of a 'sticky' shift key: it remains pressed, shifting all keys of the layout until pressed again.

It is similar to the Caps Lock key, except that it affects all keys, including the ones in the numeric row.

I am trying to use setxkbmap -option ... to handle this.

I found these promising rules in in /usr/local/share/X11/xkb/rules/base.lst:

  caps:internal        Caps Lock uses internal capitalization; Shift "pauses" Caps Lock
  caps:internal_nocancel Caps Lock uses internal capitalization; Shift doesn't affect Caps Lock
  caps:shift           Caps Lock acts as Shift with locking; Shift "pauses" Caps Lock
  caps:shift_nocancel  Caps Lock acts as Shift with locking; Shift doesn't affect Caps Lock
  caps:capslock        Caps Lock toggles normal capitalization of alphabetic characters
  caps:shiftlock       Caps Lock toggles ShiftLock (affects all keys)
  shift:breaks_caps    Shift cancels Caps Lock
  shift:both_capslock  Both Shift keys together toggle Caps Lock
  shift:both_capslock_cancel Both Shift keys together activate Caps Lock, one Shift key deactivates
  shift:both_shiftlock Both Shift keys together toggle ShiftLock

So,

setxkbmap -option shift:both_shiftlock

And I try pressing Shift (and releasing it), and typing other characters. No effect. All characters lowercase. If I hold down Shift and type other keys, it acts as you'd normally expect.

I tried caps:shift, shift:both_shiftlock and caps:shiftlock but none of them have any effect as far as I can tell. What's wrong?

Best Answer

I found a way to turn Caps Lock into Shift Lock, thanks to a Super User answer:

xmodmap -e "keycode 66 = Shift_Lock"

The following turns my left Ctrl key into shift lock:

xmodmap -e "keycode 37 = Shift_Lock"

To make the left Shift key lock, use

xmodmap -e "keycode 50 = Shift_Lock"

Right Shift key, use

xmodmap -e "keycode 62 = Shift_Lock"

When Shift Lock is active, your keyboard's Caps Lock and Scroll Lock LEDs should both be lit.

Related Solutions

How to re-enable the caps lock key

The following commands should work:

xmodmap -e 'keycode 0x42 = Caps_Lock'

setxkbmap -option

The commands above work just fine to restore the default behaviour, which I hardly ever need, luckily.

I normally remap the capslock to Control (luckily VI/VIM supports CTRL-C instead of ESC) with the following command:

setxkbmap -option ctrl:nocaps -layout gb

Xmodmap problems and inconsistencies with more than 4 alternative symbols per key

I'd better answer my own question for future reference.

After a bit of in-depth research, I found out that xmodmap is actually deprecated and is roughly patched over the xkb keyboard model. The xkb model doesn't use a linear array of alternatives, but splits layouts into groups, with each group having a couple of characters in different shift levels. The xmodmap definitions fill the entries in a very funny order: group 1, level 1,2, group 2, level 1,2, group 1, levels 3.... The groups are meant to be like "layouts" and aren't usually accessed with modifiers but with toggling. The exception is the Mode_switch character that I used, but it only accesses group 2.

That would all be fine, except keys have types. Every key is defined by the layout to be TWO_LEVEL, FOUR_LEVEL, FOUR_LEVEL_ALPHANUMERIC and so on, and each level can have different notion of which modifiers map to which levels. The behaviour I assumed (8 levels, all combinations) was actually LOCAL_EIGHT_LEVEL that wasn't used at all by the layout. So in the case of keycode 51, the default was actually TWO_LEVEL, and xmodmap filled 3 groups with the 6 keys instead of adding 6 levels to 1st group. The 3rd group wasn't reached by the Mode_switch modifier. Using another key resulted in different behaviour because pre-defined type was different.

As with the repetitions in the printout by xmodmap, I'm not sure exactly what happens (I printed the xkb definitions and all was fine), but I'm not surprised that errors occur when you map from a variable-length multidimensional array to a single list of symcodes. The output doesn't reflect the actual state anyway.

In conclusion, xmodmap is evil. Don't ever use it. Its behaviour is erratic and ill-defined at best. It doesn't do what it says it does. Make your own xkb maps. Reuse most of the layout by include-ing and add modifications that you need.

In my case, the solution is to derive the second group from greek layout and substitute math symbols in strategic places, plus some modification in the first group.

Most cheap keyboards are very limited when it comes to pressing 3 keys at a time. That resulted in erratic and hardware-dependent failures for some keys. I'll experiment around with different modifier keys (the most useless key in the world - the menu key, or similarly useless right win-key), and possibly buy a better keyboard. Combination of both problems (broken-by-design hardware + evil deceptive software) created a confusing random-looking situation that at first prevented me to see them as separate problems.

Reading material:

Best Answer

Related Solutions

How to re-enable the caps lock key

Xmodmap problems and inconsistencies with more than 4 alternative symbols per key

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