To make Spacebar act as Ctrl under appropriate circumstances, GitHub page of xcape currently instructs as follows:

# Map an unused modifier's keysym to the spacebar's keycode and make it a
# control modifier. It needs to be an existing key so that emacs won't
# spazz out when you press it. Hyper_L is a good candidate.
xmodmap -e "keycode 65 = $spare_modifier"
xmodmap -e "remove mod4 = $spare_modifier" # hyper_l is mod4 by default
xmodmap -e "add Control = $spare_modifier"

# Map space to an unused keycode (to keep it around for xcape to
# use).
xmodmap -e "keycode any = space"

# Finally use xcape to cause the space bar to generate a space when tapped.
xcape -e "$spare_modifier=space"

How to achieve this with xkb rather than xmodmap?

1 Answer 1


With Hyper_R in place of Hyper_L, it goes like this:

contents of ~/.config/xkb/keycodes/my-keycodes:

xkb_keycodes "xcape-special" {
    <HYPR> =  65;
    <SPCE> = 207;

Note: 207 is the default keycode for (virtual) Hyper_R key in the keycode table loaded on my machine.

contents of ~/.config/xkb/symbols/my-symbols:

xkb_symbols "xcape-special" {
    key <HYPR>  { [ Hyper_R ] };
    modifier_map Control { <HYPR> };

excerpt from ~/.xinitrc:


setxkbmap -layout "us+$XKB_SYMBOL_FILE(xcape-special)" \
    -keycodes "evdev+$XKB_KEYCODE_FILE(xcape-special)" \
    -option "" -print \
    | xkbcomp -I"$XKB_DIR" - "${DISPLAY%%.*}" >/dev/null 2>&1

xcape -e "Hyper_R=space"

This is not the only way to configure xkb. Configuration could probably be loaded from a single file with a single xkbcomp call. Subdirs of ~/.config/xkb/ merely follow the structure of /usr/share/X11/xkb/. The ... -print | xkbcomp ... part is somewhat convoluted but flexible. At the moment I'm unable to try a simpler setup.

  • Could you explain what is going on here? Is it really necessary to change the keycodes? Can't it be done in the symbol file? If this is the only way I'm inclined to stick with xmodmap.
    – Toothrot
    Commented Dec 22, 2018 at 13:16
  • @Toothrot I don't know if it's possible to do with symbol file alone. Never looked back since then.
    – akater
    Commented Jan 6, 2019 at 18:29

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .