The WM_NCMBUTTONDOWN message is posted when the user presses the middle 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_NCMBUTTONDOWN
nHittest = (INT) wParam; // hit-test value
pts = MAKEPOINTS(lParam); // position of cursor
Parameters
nHittest
Value of wParam. 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.
pts
Value of lParam. Specifies a POINTS structure that contains the x- and y-coordinates of the cursor. The coordinates are relative to the upper-left corner of the screen.
Return Values
If an application processes this message, it should return zero.
Remarks
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.
See Also
DefWindowProc, MAKEPOINTS, POINTS, WM_NCHITTEST, WM_NCMBUTTONDBLCLK, WM_NCMBUTTONUP, WM_SYSCOMMAND