ExcludeClipRect区域裁剪问题

cpaintdc dc(this);
crect rt1;
cpen newpen;
newpen.createpen(ps_solid,1,rgb(0,0,0));
cpen *poldpen = dc.selectobject(&newpen);
cbrush* poldbrush = (cbrush*)dc.selectstockobject(null_brush);
getdlgitem(idc_button_query)->getwindowrect(&rt1);
dc.excludecliprect(rt1);
dc.roundrect(rt,cpoint(10,10));
dc.selectobject(poldpen);
dc.selectobject(poldbrush);

绘制时使用excludecliprect裁剪出一块区域，则此区域不会受此次绘制影响，保持绘制前状态；