OnCmdMsg() VS PostMessage()

In the place you plan to post message:

a. If you are sure the WM_Command can be handled by view/document, you can directly call View::OnCmdMsg() or Doc::OnCmdMsg() to post the message;

b. If you don't know where in the command routing way will handle the command, you have to use ::PostMessage or CWnd::PostMessage() which is inside calling ::PostMessage(). See below source code:

(c:"Program Files"Microsoft Visual Studio 9.0"VC"atlmfc"include"afxwin2.inl)

_AFXWIN_INLINE BOOL CWnd::PostMessage(UINT message, WPARAM wParam, LPARAM lParam)

{ ASSERT(::IsWindow(m_hWnd)); return ::PostMessage(m_hWnd, message, wParam, lParam); }

PostMessage 和SendMessage的區別主要在於是否等待其他程式訊息處理。PostMessage只是把訊息放入隊列，不管其他程式是否處理都返回，然後繼續執 行；而SendMessage必須等待其他程式處理訊息後才返回，繼續執行。這兩個函數的傳回值也不同，PostMessage的傳回值表示 PostMessage函數執行是否正確，而SendMessage的傳回值表示其他程式處理訊息後的傳回值。