The WM_NCLBUTTONUP message is posted when the user releases the left mouse button while the cursor is within the nonclient area of a 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_NCLBUTTONUP
nHittest = (INT) wParam; // hit-test value
pts = MAKEPOINTS(lParam); // mouse-cursor coordinates
If an application processes this message, it should return zero.
The DefWindowProc function tests the given point to find out the location of the cursor and performs the appropriate action. If appropriate, DefWindowProc sends the WM_SYSCOMMAND message to the window.
An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.
If it is appropriate to do so, the system sends the WM_SYSCOMMAND message to the window.
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_NCLBUTTONDBLCLK, WM_NCLBUTTONDOWN, WM_SYSCOMMAND