SendNotifyMessageA function (winuser.h)

Sends the specified message to a window or windows. If the window was created by the calling thread, SendNotifyMessage calls the window procedure for the window and does not return until the window procedure has processed the message. If the window was created by a different thread, SendNotifyMessage passes the message to the window procedure and returns immediately; it does not wait for the window procedure to finish processing the message.

Syntax

BOOL SendNotifyMessageA(
  [in] HWND   hWnd,
  [in] UINT   Msg,
  [in] WPARAM wParam,
  [in] LPARAM lParam
);

Parameters

[in] hWnd

Type: HWND

A handle to the window whose window procedure will receive the message. If this parameter is HWND_BROADCAST ((HWND)0xffff), the message is sent to all top-level windows in the system, including disabled or invisible unowned windows, overlapped windows, and pop-up windows; but the message is not sent to child windows.

[in] Msg

Type: UINT

The message to be sent.

For lists of the system-provided messages, see System-Defined Messages.

[in] wParam

Type: WPARAM

Additional message-specific information.

[in] lParam

Type: LPARAM

Additional message-specific information.

Return value

Type: BOOL

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

If you send a message in the range below WM_USER to the asynchronous message functions (PostMessage, SendNotifyMessage, and SendMessageCallback), its message parameters cannot include pointers. Otherwise, the operation will fail. The functions will return before the receiving thread has had a chance to process the message and the sender will free the memory before it is used.

Applications that need to communicate using HWND_BROADCAST should use the RegisterWindowMessage function to obtain a unique message for inter-application communication.

The system only does marshalling for system messages (those in the range 0 to (WM_USER-1)). To send other messages (those >= WM_USER) to another process, you must do custom marshalling.

Requirements

See also

Conceptual

Messages and Message Queues

PostMessage

PostThreadMessage

Reference

RegisterWindowMessage

SendMessage

SendMessageCallback

SendNotifyMessage