WS_xxx are Window styles. Both clip of area of other window when window overlaps another window.
Clip sibling for example will cause MDI child window to paint itself over another child window (sibling) when overlapped. The same will happen
WS_CLIPCHILDREN will do exactly the same when parent overlaps child window.
综上所述
WS_CLIPCHILDREN,使得父窗体在绘制时留出其上的子窗体的位置不去画它,而那片区域留着子窗体去画。
WS_CLIPSIBLING,必须用于子窗体,使得该子窗体在收到WM_PAINT时同时令其共父的诸多子窗体(MSDN讲必须不在该区域,即不与之重叠)也会被PAINT。
参考连接:
http://www.codeguru.com/forum/archive/index.php/t-391710.html