The WM_NCMOUSEMOVE message is posted to a window when the cursor is moved within the nonclient area of the window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
WM_NCMOUSEMOVE
nHittest = (INT) wParam; // hit-test value
pts = MAKEPOINTS(lParam); // position of cursor
If an application processes this message, it should return zero.
If it is appropriate to do so, the system sends the WM_SYSCOMMAND message to the window.
An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winuser.h.
Mouse Input Overview, Mouse Input Messages, DefWindowProc, MAKEPOINTS, POINTS, WM_NCHITTEST, WM_SYSCOMMAND