Under the Sway Wayland compositor, we could set set xkb_layout and xkb_options for keyboards in order to do weird key mapping related things. Many people use caps:ctrl_modifier and caps:escape in xkb_options (see xkeyboard-config(7) for other options) to make Caps Lock function as an extra Ctrl or Esc key. If all you want to do is do a relatively common modification like that, chances are that xkb_variant and xkb_options already has what you want, and you should just set that. But if what you...
