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 WM_NCPAINT

The WM_NCPAINT message is sent to a window when its frame must be painted.

A window receives this message through its WindowProc function.

    LRESULT CALLBACK WindowProc(
      HWND hwnd,       // handle to window
      UINT uMsg,       // WM_NCPAINT
      WPARAM wParam,   // handle to update region (HRGN)
      LPARAM lParam    // not used
    );

Parameters

• wParam Handle to the update region of the window. The update region is clipped to the window frame. When wParam is 1, the entire window frame needs to be updated.
• lParam This parameter is not used.

Return Values

An application returns zero if it processes this message.

Remarks

The DefWindowProc function paints the window frame.

An application can intercept the WM_NCPAINT message and paint its own custom window frame. The clipping region for a window is always rectangular, even if the shape of the frame is altered.

The wParam value can be passed to GetDCEx as in the following example.

    case WM_NCPAINT:
    {
        HDC hdc;
        hdc = GetDCEx(hwnd, (HRGN)wParam, DCX_WINDOW|DCX_INTERSECTRGN);
        // Paint into this DC
        ReleaseDC(hwnd, hdc);
    }

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