Constant WIDTH_MAX_PERMILLE 

pub const WIDTH_MAX_PERMILLE: u32 = u32::MAX; // 4_294_967_295u32

The storage’s own end, over four million strips: a drag cannot reach it, even resting at the display’s edge while the strip scrolls under it, so there is no widest window anyone can feel. (Ten strips used to be the limit, which an edge drag that scrolls the strip reaches in seconds.)