HISTO_MIN_SIZE
sel->r.width = clamp_t(unsigned int, sel->r.width, HISTO_MIN_SIZE,
sel->r.height = clamp_t(unsigned int, sel->r.height, HISTO_MIN_SIZE,
histo->entity.min_width = HISTO_MIN_SIZE;
histo->entity.min_height = HISTO_MIN_SIZE;