The WM_MOUSEACTIVATE message is sent when the cursor is in an inactive window and the user presses a mouse button. The parent window receives this message only if the child window passes it to the DefWindowProc function.

A window receives this message through its WindowProc function.

Syntax

WM_MOUSEACTIVATE

    WPARAM wParam
    LPARAM lParam;
    

Parameters

wParam

Handle to the top-level parent window of the window being activated.

lParam

The low-order word specifies the hit-test value returned by the DefWindowProc function as a result of processing the WM_NCHITTEST message. For a list of hit-test values, see WM_NCHITTEST.

The high-order word specifies the identifier of the mouse message generated when the user pressed a mouse button. The mouse message is either discarded or posted to the window, depending on the return value.

Return Value

The return value specifies whether the window should be activated and whether the identifier of the mouse message should be discarded. It must be one of the following values.

MA_ACTIVATE	Activates the window, and does not discard the mouse message.
MA_ACTIVATEANDEAT	Activates the window, and discards the mouse message.
MA_NOACTIVATE	Does not activate the window, and does not discard the mouse message.
MA_NOACTIVATEANDEAT	Does not activate the window, but discards the mouse message.

Remarks

The DefWindowProc function passes the message to a child window's parent window before any processing occurs. The parent window determines whether to activate the child window. If it activates the child window, the parent window should return MA_NOACTIVATE or MA_NOACTIVATEANDEAT to prevent the system from processing the message further.

Notification Requirements

Minimum DLL Version	None
Header	Declared in Winuser.h, include Windows.h
Minimum operating systems	Windows 95, Windows NT 3.1

See Also

Mouse Input Overview, DefWindowProc, HIWORD, LOWORD, WM_NCHITTEST