MFC 是客户区先绘制还是非客户区先绘制

MFC 是客户区先绘制还是非客户区先绘制，是先响应OnPaint(),还是先响应OnNCPaint()?

这个可以测试下，我这里的结果是先执行OnNCPaint()

先响应OnNCPaint()

WM_NCPAINT message is sent to a window when its frame must be painted.
The DefWindowProc function paints the window frame.
An application can intercept the WM_NCPAINT message and paint its own custom window frame. The clipping region for a window is always rectangular, even if the shape of the frame is altered.

WIN32的消息循环应该是先到DefWindowProc

当然先绘制非客户区了，皮之不存毛将焉附？没有非客户区，客户区如何存在并访问？