// Let space provide nobreakspace for the desired level.
partial
xkb_symbols "none" {
  key <SPCE> {
    type[Group1]="ONE_LEVEL",
    symbols[Group1]= [ space ]
  };
};

partial
xkb_symbols "level2" {
  key <SPCE> {
    type[Group1]="TWO_LEVEL",
    symbols[Group1]= [ space, nobreakspace ]
  };
};

partial
xkb_symbols "level3" {
  key <SPCE> {
    type[Group1]="FOUR_LEVEL",
    symbols[Group1]= [ space, space, nobreakspace ]
  };
};

partial
xkb_symbols "level4" {
  key <SPCE> {
    type[Group1]="FOUR_LEVEL",
    symbols[Group1]= [ space, space, space, nobreakspace ]
  };
};
