PostMessage

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This function places a message in the message queue associated with the thread that created the specified window and then returns without waiting for the thread to process the message. Messages in a message queue are retrieved by calls to the GetMessage or PeekMessage function.

Syntax

BOOL PostMessage(
  HWND hWnd, 
  UINT Msg, 
  WPARAM wParam, 
  LPARAM lParam 
); 

Parameters

• hWnd
  [in] Handle to the window whose window procedure is to receive the message. Two values have special meanings.

  Value	Description
  HWND_BROADCAST	The message is posted to all top-level windows in the system, including disabled or invisible unowned windows, overlapped windows, and pop-up windows. The message is not posted to child windows.
  NULL	The function behaves like a call to PostThreadMessage with the dwThreadId parameter set to the identifier of the current thread.

• Msg
  [in] Specifies the message to be posted.

• wParam
  [in] Specifies additional message-specific information.

• lParam
  [in] Specifies additional message-specific information.

Return Value

Nonzero indicates success. Zero indicates failure. To get extended error information, call GetLastError.

Remarks

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

If you send a message in the range below WM_USER to the asynchronous message functions (PostMessage and SendNotifyMessage), 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.

Windows Embedded CE does not support all the messages the Windows-based desktop platforms support.

Requirements

See Also

Reference

Message Queue Functions
GetMessage
PeekMessage
PostThreadMessage
RegisterWindowMessage
SendDlgItemMessage
SendMessage