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 WM_NCMBUTTONDOWN

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.

A window receives this message through its WindowProc function.

    LRESULT CALLBACK WindowProc(
      HWND hwnd,       // handle to window
      UINT uMsg,       // WM_NCMBUTTONDOWN
      WPARAM wParam,   // hit-test value
      LPARAM lParam    // cursor position
    );

Parameters

• 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.
• 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

You can also use the GET_X_LPARAM and GET_Y_LPARAM macros to extract the values of the x- and y- coordinates from lParam.

xPos = GET_X_LPARAM(lParam); yPos = GET_Y_LPARAM(lParam);

If it is appropriate to do so, the system sends the WM_SYSCOMMAND message to the window.

Requirements

  Windows NT/2000 or later: Requires Windows NT 3.1 or later.
  Windows 95/98/Me: Requires Windows 95 or later.
  Header: Declared in Winuser.h; include Windows.h.

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Notebook exported on Monday, 7 July 2008, 18:56:50 PM Eastern Daylight Time