Having found WM_NULL definition in the windows.inc file I didn't find any description of the message code in all docs I had. Is it real message code? If it is, what is it used for? The Svin.
i've only used it once, when i was writing a message hooking dll. it can also be used with the SendMessageTimeout function to see if an application has stopped responding. other than that, it's pretty useless.
I hope this is what u want or at least help u WM_NULL The WM_NULL message performs no operation. An application sends the WM_NULL message if it wants to post a message that the recipient window will ignore. A window receives this message through its WindowProc function. LRESULT CALLBACK WindowProc( HWND hwnd, // handle to window UINT uMsg, // WM_NULL WPARAM wParam, // not used LPARAM lParam // not used ); Parameters wParam This parameter is not used. lParam This parameter is not used. Return Values An application returns zero if it processes this message. Remarks For example, if an application has installed a WH_GETMESSAGE hook and wants to prevent a message from being processed, the GetMsgProc callback function can change the message number to WM_NULL so the recipient will ignore it. As another example, an application can check if a window is responding to messages by sending the WM_NULL message with the SendMessageTimeoutfunction.