WM_NCLBUTTONUP
nHittest = (INT) wParam; /* hit-test code */
pts = MAKEPOINTS(lParam); /* mouse-cursor coordinates */
The WM_NCLBUTTONUP message is posted when the user releases the left mouse button while the mouse cursor is within the nonclient area of a window. This message is posted to the window that contains the mouse cursor. If a window has the mouse captured, this message is not posted.
nHittest
Value of wParam. Specifies the hit-test code returned by the DefWindowProc function as a result of processing the WM_NCHITTEST message. For more information, see the description of the WM_NCHITTEST message.
pts
Value of lParam. Specifies a POINTS structure that contains the x- and y-coordinates of the mouse cursor. The coordinates are relative to the upper-left corner of the screen. The POINTS structure has the following form:
typedef struct tagPOINTS { /* pts */
SHORT x;
SHORT y;
} POINTS;
An application should return zero if it processes this message.
An application can use the MAKEPOINTS macro to convert the lParam parameter to a POINTS structure.
If appropriate, WM_SYSCOMMAND messages are sent.
DefWindowProc, WM_NCHITTEST, WM_NCLBUTTONDBLCLK, WM_NCLBUTTONDOWN, WM_SYSCOMMAND