英文单词解释
clip:夹子、子弹夹、回形针；夹住，修剪
sibling:同胞兄弟或姐妹
overlapped:重叠
这两个Window Stype的特性与异同素来不太清楚，今日作一笔记：
MSDN的解释为：
- WS_CLIPCHILDRENExcludes the area occupied by child windows when you draw within the parent window. Used when you create the parent window.
- WS_CLIPSIBLINGSClips child windows relative to each other; that is, when a particular child window receives a paint message, theWS_CLIPSIBLINGSstyle clips all other overlapped child windows out of the region of the child window to be updated. (IfWS_CLIPSIBLINGSis not given and child windows overlap, when you draw within the client area of a child window, it is possible to draw within the client area of a neighboring child window.) For use with theWS_CHILDstyle only.
此处另有一文的解释为：
JohnCz 06-27-2006, 09:40 PM It is not a property per se.
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。
//下面也是对WS_CLIPSIBLINGS的理解
所有的overlapped窗口和popup窗口，都有WS_CLIPSIBLINGS 属性，
这些窗口不能在它的sibling窗口上绘图
对于child窗口，如果没有这个属性，它能在它的sibling窗口上绘图
+-----------+
|A |
| +--------+-------
| | | B |
| | C | |
+---+-------+ |
| |
+---------------+
如果A, B都是child窗口，
如果A具有WS_CLIPSIBLINGS属性，
那么A重绘时不会重绘C部分
clip是裁减，去除的意思 相当与英文的Exclude
个人理解：WS_CLIPCHILDREN和WS_CLIPSIBLING都是为了减少重画，减少闪动，保证窗口的重叠部分只有一个窗口来实现PAINT。
