Better Super Alt+Tab for QMK

keymap.c

// Adds the ALT_TAB keycode to a QMK keymap.

// Based on https://www.reddit.com/r/MechanicalKeyboards/comments/mrnxrj/better_super_alttab/

// Functionality is the following (basically the same thing as a normal Alt + Tab but without having
// to leave Alt pressed):
// - On pressing ALT_TAB, the window switch menu pops up.
// - While the menu is visible, it's possible to cycle through the selection by pressing ALT_TAB
//   again, or Shift + ALT_TAB, or the arrow keys.
// - The selected window can be brought up by pressing Enter, which also closes the menu.
//   Alternatively, pressing Escape closes the menu without selecting anything.

enum custom_keycodes {
  ALT_TAB = SAFE_RANGE,
};

bool is_alt_tab_active = false;

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
  switch (keycode) {
    case ALT_TAB:
      if (record->event.pressed) {
        if (!is_alt_tab_active) {
          is_alt_tab_active = true;
          register_code(KC_LALT);
        }
        register_code(KC_TAB);
      } else {
        unregister_code(KC_TAB);
      }
      return false;

    case KC_ENTER:
      if (record->event.pressed) {
        if (is_alt_tab_active) {
          unregister_code(KC_LALT);
          is_alt_tab_active = false;
          return false;
        }
      }
      return true;

    case KC_ESCAPE:
      if (record->event.pressed) {
        if (is_alt_tab_active) {
          register_code(KC_ESCAPE);
          unregister_code(KC_LALT);
          unregister_code(KC_ESCAPE);
          is_alt_tab_active = false;
          return false;
        }
      }
      return true;

    default:
      return true;
  }
}