OpenGrok

// These partial variants assign ISO_Level3_Shift to various XKB keycodes
// so that the third shift level can be reached.

// The default behaviour:
// the right Alt key (AltGr) chooses the third symbol engraved on a key.
default  partial modifier_keys
xkb_symbols "ralt_switch" {
  key <RALT> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// Ensure a mapping to a real modifier for LevelThree.
partial modifier_keys
xkb_symbols "modifier_mapping" {
  replace key <LVL3> {
    type[Group1] = "ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  modifier_map Mod5 { <LVL3> };
};

// The right Alt key never chooses the third level.
// This option attempts to undo the effect of a layout's inclusion of
// 'ralt_switch'.  You may want to also select another level3 option
// to map the level3 shift to some other key.
partial modifier_keys
xkb_symbols "ralt_alt" {
  key <RALT> {
    type[Group1]="TWO_LEVEL",
    type[Group2]="TWO_LEVEL",
    type[Group3]="TWO_LEVEL",
    type[Group4]="TWO_LEVEL",
    symbols[Group1] = [ Alt_R, Meta_R ],
    symbols[Group2] = [ Alt_R, Meta_R ],
    symbols[Group3] = [ Alt_R, Meta_R ],
    symbols[Group4] = [ Alt_R, Meta_R ]
  };
  modifier_map Mod1 { <RALT> };
};

// The right Alt key (while pressed) chooses the third shift level,
// and Compose is mapped to its second level.
partial modifier_keys
xkb_symbols "ralt_switch_multikey" {
  key <RALT> {
    type[Group1]="TWO_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, Multi_key ]
  };
  include "level3(modifier_mapping)"
};

// A special case of the right-Alt switch -- for use with grp:alts_toggle.
hidden partial modifier_keys
xkb_symbols "ralt_switch_for_alts_toggle" {
  virtual_modifiers LAlt, AltGr;
  key <LALT> {
    type[Group1]="PC_RALT_LEVEL2",
    symbols[Group1] = [ Alt_L, ISO_Prev_Group, ISO_Prev_Group ],
    virtualMods= LAlt
  };
  key <RALT> {
    type[Group1]="PC_ALT_LEVEL2",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Next_Group ],
    virtualMods= AltGr
  };
  include "level3(modifier_mapping)"
};

// Either Alt key (while pressed) chooses the third shift level.
// (To be used mostly to imitate Mac OS functionality.)
partial modifier_keys
xkb_symbols "alt_switch" {
  include "level3(lalt_switch)"
  include "level3(ralt_switch)"
};

// The left Alt key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "lalt_switch" {
  key <LALT> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The right Ctrl key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "switch" {
  key <RCTL> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Menu key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "menu_switch" {
  key <MENU> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// Either Win key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "win_switch" {
  include "level3(lwin_switch)"
  include "level3(rwin_switch)"
};

// The left Win key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "lwin_switch" {
  key <LWIN> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The right Win key (while pressed) chooses the third shift level.
// (When using this map, you should set your keyboard as pc101 or pc102
// instead of pc104 or pc105.)
partial modifier_keys
xkb_symbols "rwin_switch" {
  key <RWIN> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Enter key on the kepypad (while pressed) chooses the third shift level.
// (This is especially useful for Mac laptops which miss the right Alt key.)
partial modifier_keys
xkb_symbols "enter_switch" {
  key <KPEN> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The CapsLock key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "caps_switch" {
  key <CAPS> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Backslash key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "bksl_switch" {
  key <BKSL> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The Less/Greater key (while pressed) chooses the third shift level.
partial modifier_keys
xkb_symbols "lsgt_switch" {
  key <LSGT> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift ]
  };
  include "level3(modifier_mapping)"
};

// The CapsLock key (while pressed) chooses the third shift level,
// and latches when pressed together with another third-level chooser.
partial modifier_keys
xkb_symbols "caps_switch_latch" {
  key <CAPS> {
    type[Group1]="THREE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Level3_Shift, ISO_Level3_Latch ]
  };
  include "level3(modifier_mapping)"
};

// The Backslash key (while pressed) chooses the third shift level,
// and latches when pressed together with another third-level chooser.
partial modifier_keys
xkb_symbols "bksl_switch_latch" {
  key <BKSL> {
    type[Group1]="THREE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Level3_Shift, ISO_Level3_Latch ]
  };
  include "level3(modifier_mapping)"
};

// The Less/Greater key (while pressed) chooses the third shift level,
// and latches when pressed together with another third-level chooser.
partial modifier_keys
xkb_symbols "lsgt_switch_latch" {
  key <LSGT> {
    type[Group1]="THREE_LEVEL",
    symbols[Group1] = [ ISO_Level3_Shift, ISO_Level3_Shift, ISO_Level3_Latch ]
  };
  include "level3(modifier_mapping)"
};