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WM_NCLBUTTONUP Overview Group

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

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.

Default Action

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.

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.