WM_MOUSEACTIVATE message

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.

#define WM_MOUSEACTIVATE                0x0021

wParam

A 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.

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.

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.

Reference

DefWindowProc

HIWORD

LOWORD

WM_NCHITTEST

Conceptual

Mouse Input