MOUSE_PARAM_BTN_OFF
if (m->b > MOUSE_PARAM_UTF8_MAX - MOUSE_PARAM_BTN_OFF ||
len += input_key_split2(m->b + MOUSE_PARAM_BTN_OFF, &buf[len]);
if (m->b + MOUSE_PARAM_BTN_OFF > MOUSE_PARAM_MAX)
buf[len++] = m->b + MOUSE_PARAM_BTN_OFF;
if (b < MOUSE_PARAM_BTN_OFF ||
b -= MOUSE_PARAM_BTN_OFF;