Constant WIDTH_MIN_PERMILLE 

pub const WIDTH_MIN_PERMILLE: u16 = 1; // 1u16

Bounds of what a width can store, not of what a person may choose: a group may be a sliver of a share up to several strips wide, the strip scrolls. Windows’ own minimum and maximum sizes are the client’s to state (xdg_toplevel hints are honoured when it is configured); the only limit of ours is WIDTH_FLOOR_PX.