The SendMessageTimeout function sends the specified message to a window or windows. The function calls the window procedure for the specified window and, if the specified window belongs to a different thread, does not return until the window procedure has processed the message or the specified time-out period has elapsed. If the window receiving the message belongs to the same queue as the current thread, the window procedure is called directly — the time-out value is ignored.
LRESULT SendMessageTimeout(
HWND hWnd, // handle of destination window
UINT Msg, // message to send
WPARAM wParam, // first message parameter
LPARAM lParam, // second message parameter
UINT fuFlags, // how to send the message
UINT uTimeout, // time-out duration
LPDWORD lpdwResult // return value for synchronous call
);
Value | Meaning |
---|---|
SMTO_ABORTIFHUNG | Returns without waiting for the time-out period to elapse if the receiving process appears to be in a "hung" state. |
SMTO_BLOCK | Prevents the calling thread from processing any other requests until the function returns. |
SMTO_NORMAL | The calling thread is not prevented from processing other requests while waiting for the function to return. |
SMTO_NOTIMEOUTIFNOTHUNG | Windows NT 5.0 and later: Does not return when the time-out period elapses if the receiving thread is not hung. |
If the function succeeds, the return value is nonzero.
If the function fails or time out, the return value is zero. To get extended error information, call GetLastError. If GetLastError returns zero, then the function timed out. SendMessageTimeout does not provide information about individual windows timing out if HWND_BROADCAST is used.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winuser.h.
Import Library: Use user32.lib.
Unicode: Implemented as Unicode and ANSI versions on Windows NT.
Messages and Message Queues Overview, Message and Message Queue Functions, InSendMessage, PostMessage, SendDlgItemMessage, SendMessage, SendMessageCallback, SendNotifyMessage