Customize Keyboard Mappings with Wayland – How to Guide

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I use Linux on a Macbook with a UK/GB keyboard and I customize the keymap to solve some problems Apple's weird keyboard layout causes. I use xmodmap to do this. I'd like to try Wayland, but xmodmap doesn't work in that. How can I achieve a similar result in Wayland? The .Xmodmap file I use contains the following:

keycode  12 = 3 numbersign 3 sterling sterling sterling threesuperior sterling
clear Control
clear Mod4
add Control = Control_L Super_R
add Mod4 = Super_L
keysym Caps_Lock = NoSymbol Caps_Lock

Line 1: On UK keyboards Shift–3 is £, so # usually has its own key near Return. But on the Mac # is obtained with Altgr–3. As a programmer I use # far more than £ so this line swaps them over. Selecting US layout also achieves this, but doing that in Linux also swaps some other commonly used keys, whereas in OS X those other keys are unaffected by US/UK.

Lines 2-5: Make the right Cmd key act as Right-Ctrl, because this keyboard has no physical right Ctrl key.

Line 6: Makes CapsLock only work if you press it with Shift. Not Mac-specific, this should be a standard option for all OSs and keyboards.

Best Answer

Unfortunately modifying the system XKB database in /usr/share/X11/xkb is the only way; from your other question it looks like you've gotten that part working.

The limitation is mostly due to the immaturity of Wayland and a design oversight in XKB.

Tools like setxkbmap and xkbcomp provide an -I option to add a user-defined database to search (eg ~/.xkb or ~/.config/xkb, with files and subdirectories laid out like the system database). These tools interact with the X server, so they might be useful configuring the Xwayland compatibility layer for running X applications under Wayland. But they do not at present speak the Wayland protocols.
Wayland protocols are still maturing. Currently it seems the input-method and text-input protocols are most relevant, and both are unstable. Neither mention anything about altering a defined keymap; these details are left to the compositor.
GNOME and KDE both provide keyboard-handling settings daemons that should handle system XKB options, including changing on the fly. To the best of my knowledge, there's no way to tell either about user customizations. As far as I know, Weston and other compositors rely on config files or environment variables to set XKB options at startup, and provide no way to change them other than exiting and restarting.
Even in XKB itself, this is not fully supported. Your custom symbols file can include other system symbols files. But at present there's no include functionality for XKB rules files, so even if you had a tool that would talk to the Wayland compositor and would look up your personal customizations, you'd have to manually include all the rules you want to use (ie copy rules/evdev* from the system XKB and modify it). libxkbcommon has an open issue on this topic and a related bug.

Related Solutions

OpenSuse custom keyboard shortcuts not working

You do not have to disable Compiz completely. I had the same issue, but it affected specifically the "Run Application Dialog" and "Open Main Menu". The problem is that Compiz Fusion takes control over some keyboard shotcuts to keep compatibility. This can be configured through the Compiz plugin "Gnome Compatibility" and other areas of the Compiz Panel.

Modifying Keyboard Layout in Wayland

As I've stated in my question, there is already xkb which already has alot options for modifying the keyboard. It wasn't an option for me because the only option to modify the printscr key, replaced it with Win_R. Gunnar Hjalmarsson on this thread suggested to me that I modify xkb's modifications so that the printscr/win_r would do printscr/menu instead. We worked out a solution together and I'm going to retransmit it here:

In terminal, enter:

sudo su
nano /usr/share/X11/xkb/symbols/altwin

At the bottom of the file you will find:

// Win is mapped to the PrtSc key (and the usual Win key).
partial modifier_keys
xkb_symbols "prtsc_rwin" {
    replace key <PRSC> { [ Super_R, Super_R ] };
    modifier_map Mod4 { <PRSC>, <RWIN> };
};

Delete this section and replace it with this:

// Menu is mapped to the PrtSc key (and the usual Win key).
xkb_symbols "prtsc_rwin" {
     replace key <PRSC> { [ Menu, Menu ] };
     modifier_map Mod4 { <PRSC>, <MENU> };
};

To delete in nano, use backspace key (highlighting and deleting doesn't work). To paste, use shift-ctrl-v. To exit and save, press ctrl-x, select yes to overwrite and press enter.

Reboot. In Gnome/Ubuntu Go to gnome-tweak-tools In tweak tools go to Keyboard & Mouse section, press the Additional Layout Options button and expand Alt/Win key behavior. Selecting the option on the very bottom: Win is mapped to printscr (remember that we've modified just this behavior to swap print and Menu instead of print and Win). (I'm sure there is a way of turning on the modded xkb option in KDE but I don't use it, so I can't give you the exact procedure).