Ctrl remap question

Help
1

how key remap options works, and where can i find actual docs on it?

I remap CapsLock to be an aditional Ctrl key. On some machines it works fine, others have problems on things like firefox:

On firefox, if i type “kde” in the address bar and press ctrl+enter, i get “h__ps://www.kde.com” (lame, i know)… but if i press capsLock+enter, it just register the return key and tries to load “h__ps://kde” alone

when i run xev on those machines, i see that capsLock register as Caps Lock indeed! but it does behave as L_Ctrl on most programs (only kde and maybe vnc clients i see it as caps lock). What is responsible for translating that to Ctrl if X sees it as caps lock?!?! i’m actually more confused on why it works :slight_smile:

Investigating this, the bad machines have
Settings > Input devices > keyboard > Advanced > Caps Lock Behavior > Make Caps Lock and aditional Ctrl

while the “good” machines have
Settings > Input devices > keyboard > Advanced > Ctrl Position > Caps Lock as Ctrl

I tried following the links on the help for the advanced tab, but it only sends me to XKeyboardConfig

PS: h__ps used instead of https because lame new user restrict number of urls.

2

If you look at /usr/share/X11/xkb/symbols/capslock, ctrl_modifier does:

// This changes the <CAPS> key to become a Control modifier,
// but it will still produce the Caps_Lock keysym.
hidden partial modifier_keys
xkb_symbols "ctrl_modifier" {
    replace key <CAPS> {
        type[Group1] = "ONE_LEVEL",
        symbols[Group1] = [ Caps_Lock ],
        actions[Group1] = [ SetMods(modifiers=Control) ]
    };
    modifier_map Control { <CAPS> };
};

while looking at /usr/share/X11/xkb/symbols/ctrl, nocaps does:

// Eliminate CapsLock, making it another Ctrl.
partial modifier_keys
xkb_symbols "nocaps" {
    replace key <CAPS> { [ Control_L, Control_L ] };
    modifier_map  Control { <CAPS>, <LCTL> };
};

So, ctrl:nocaps makes CapsLock into an additional Ctrl key, including both activating the Control modifier when it’s pressed, and sending the Control_L keysym in both level 1 and level 2 (when Shift is pressed), while caps:ctrl_modifier just makes CapsLock activate the Control modifier when it’s pressed, while still sending the Caps_Lock keysym.

In the latter case, programs which look at modifiers when a key is pressed will work as you expect, while programs that just look at keysyms, and keep their own internal modifier state will not.

1 Like
3

oh that’s a very important distinction. i might send a patch later this month with some better text to these options.

thanks for all the details

4

So I went ahead and opened an issue and MR in xkeyboard-config to improve the description of caps:ctrl_modifier. See:

1 Like
5

Thank you so much for raising this and the developers for fixing the issue.

If anyone else is left wondering, in the GUI one of the options is under “Caps Lock Behavior” and the other under “Ctrl Position”. This is in the original post, but I had missed it when skimming.