MASK_DOUBLE_CLICK
if ((sp->_mouse_mask2 & MASK_DOUBLE_CLICK(b))
next->bstate |= MASK_DOUBLE_CLICK(b);
&& (ep->bstate & MASK_DOUBLE_CLICK(b))
SP_PARM->_mouse_mask2 |= MASK_DOUBLE_CLICK(b);
if (SP_PARM->_mouse_mask2 & MASK_DOUBLE_CLICK(b))