SendMessage

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This function sends the specified message to a window or windows. SendMessagecalls the window procedure for the specified window and does not return until the window procedure has processed the message. The PostMessagefunction, in contrast, posts a message to a thread's message queue and returns immediately.

LRESULT
SendMessage(
HWND
hWnd
,
UINT
Msg
,
WPARAM
wParam
,
LPARAM
lParam
);

Parameters

hWnd

[in] Handle to the window whose window procedure will receive the message. If this parameter is HWND_BROADCAST, 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.

Msg

[in] Specifies the message to be sent.

wParam

[in] Specifies additional message-specific information.

lParam

[in] Specifies additional message-specific information.

Return Values

The return value specifies the result of the message processing and depends on the message sent.

Remarks

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

If the specified window was created by the calling thread, the window procedure is called immediately as a subroutine. If the specified window was created by a different thread, the system switches to that thread and calls the appropriate window procedure. Messages sent between threads are processed only when the receiving thread executes message retrieval code. The sending thread is blocked until the receiving thread processes the message.

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

Requirements

Runs on	Versions	Defined in	Include	Link to
Windows CE OS	1.0 and later	Winuser.h		Msgque.lib

Note This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.