qmk-firmware/docs/feature_space_cadet.md

Space Cadet: The Future, Built In

Steve Losh described the Space Cadet Shift quite well. Essentially, when you tap Left Shift on its own, you get an opening parenthesis; tap Right Shift on its own and you get the closing one. When held, the Shift keys function as normal. Yes, it's as cool as it sounds, and now even cooler supporting Control and Alt as well!

Usage

Firstly, in your keymap, do one of the following:

• Replace the Left Shift key with KC_LSPO (Left Shift, Parenthesis Open), and Right Shift with KC_RSPC (Right Shift, Parenthesis Close).
• Replace the Left Control key with KC_LCPO (Left Control, Parenthesis Open), and Right Control with KC_RCPC (Right Control, Parenthesis Close).
• Replace the Left Alt key with KC_LAPO (Left Alt, Parenthesis Open), and Right Alt with KC_RAPC (Right Alt, Parenthesis Close).
• Replace any Shift key in your keymap with KC_SFTENT (Right Shift, Enter).

Keycodes

Keycode	Description
KC_LSPO	Left Shift when held, ( when tapped
KC_RSPC	Right Shift when held, ) when tapped
KC_LCPO	Left Control when held, ( when tapped
KC_RCPC	Right Control when held, ) when tapped
KC_LAPO	Left Alt when held, ( when tapped
KC_RAPC	Right Alt when held, ) when tapped
KC_SFTENT	Right Shift when held, Enter when tapped

Caveats

Space Cadet's functionality can conflict with the default Command functionality when both Shift keys are held at the same time. See the Command feature for info on how to change it, or make sure that Command is disabled in your rules.mk with:

COMMAND_ENABLE = no

Configuration

By default Space Cadet assumes a US ANSI layout, but if your layout uses different keys for parentheses, you can redefine them in your config.h. In addition, you can redefine the modifier to send on tap, or even send no modifier at all. The new configuration defines bundle all options up into a single define of 3 key codes in this order: the Modifier when held or when used with other keys, the Tap Modifer sent when tapped (no modifier if KC_TRNS), finally the Keycode sent when tapped. Now keep in mind, mods from other keys will still apply to the Keycode if say KC_RSFT is held while tapping KC_LSPO key with KC_TRNS as the Tap Modifer.

Define	Default	Description
LSPO_KEYS	KC_LSFT, LSPO_MOD, LSPO_KEY	Send KC_LSFT when held, the mod and key defined by LSPO_MOD and LSPO_KEY.
RSPC_KEYS	KC_RSFT, RSPC_MOD, RSPC_KEY	Send KC_RSFT when held, the mod and key defined by RSPC_MOD and RSPC_KEY.
LCPO_KEYS	KC_LCTL, KC_LSFT, KC_9	Send KC_LCTL when held, the mod KC_LSFT with the key KC_9 when tapped.
RCPC_KEYS	KC_RCTL, KC_RSFT, KC_0	Send KC_RCTL when held, the mod KC_RSFT with the key KC_0 when tapped.
LAPO_KEYS	KC_LALT, KC_LSFT, KC_9	Send KC_LALT when held, the mod KC_LSFT with the key KC_9 when tapped.
RAPC_KEYS	KC_RALT, KC_RSFT, KC_0	Send KC_RALT when held, the mod KC_RSFT with the key KC_0 when tapped.
SFTENT_KEYS	KC_RSFT, KC_TRNS, SFTENT_KEY	Send KC_RSFT when held, no mod with the key SFTENT_KEY when tapped.
SPACE_CADET_MODIFIER_CARRYOVER	Not defined	Store current modifiers before the hold mod is pressed and use them with the tap mod and keycode. Useful for when you frequently release a modifier before triggering Space Cadet.

Obsolete Configuration

These defines are used in the above defines internally to support backwards compatibility, so you may continue to use them, however the above defines open up a larger range of flexibility than before. As an example, say you want to not send any modifier when you tap just KC_LSPO, with the old defines you had an all or nothing choice of using the DISABLE_SPACE_CADET_MODIFIER define. Now you can define that key as: #define LSPO_KEYS KC_LSFT, KC_TRNS, KC_9. This tells the system to set Left Shift if held or used with other keys, then on tap send no modifier (transparent) with the KC_9.

Define	Default	Description
LSPO_KEY	KC_9	The keycode to send when Left Shift is tapped
RSPC_KEY	KC_0	The keycode to send when Right Shift is tapped
LSPO_MOD	KC_LSFT	The modifier to apply to LSPO_KEY
RSPC_MOD	KC_RSFT	The modifier to apply to RSPC_KEY
SFTENT_KEY	KC_ENT	The keycode to send when the Shift key is tapped
DISABLE_SPACE_CADET_MODIFIER	Not defined	If defined, prevent the Space Cadet from applying a modifier