/// <summary> Provide a bitmap, containing the transparent graphic, that can be used independent from this class. </summary>
        /// <param name="display"> The display pointer, that specifies the connection to the X server. <see cref="System.IntPtr"/> </param>
        /// <param name="window"> The target window to create the pixmap for. <see cref="IntPtr"/> </param>
        /// <param name="backgroundColorPixel"> The background color behind any transparent pixel. <see cref="TPixel"/> </param>
        /// <param name="maskPixmap"> The mask pixmap to distinguish transparent from intransparent pixel. <see cref="IntPtr"/> </param>
        /// <returns> The (server side) pixmap (that must be feed) on success, or IntPtr.Zero otherwise. <see cref="IntPtr"/> </returns>
        public IntPtr CreateIndependentPixmap(IntPtr display, IntPtr window, TPixel backgroundColorPixel, IntPtr maskPixmap)
        {
            if (_graphicXImage == IntPtr.Zero)
            {
                return(IntPtr.Zero);
            }

            IntPtr pixmap = X11lib.XCreatePixmap(display, window, (TUint)_width, (TUint)_height, (TUint)_graphicDepth);

            // Fill pixmap with background color.
            IntPtr bgGc = X11lib.XCreateGC(display, window, (TUlong)0, IntPtr.Zero);

            X11lib.XSetForeground(display, bgGc, backgroundColorPixel);
            X11lib.XFillRectangle(display, pixmap, bgGc, (TInt)0, (TInt)0, (TUint)_width, (TUint)_height);
            X11lib.XFreeGC(display, bgGc);
            bgGc = IntPtr.Zero;

            // Overlay the image.
            IntPtr pixmapGc = X11lib.XCreateGC(display, window, (TUlong)0, IntPtr.Zero);

            if (pixmapGc != IntPtr.Zero)
            {
                if (maskPixmap != IntPtr.Zero)
                {
                    // Prepare the clipping graphics context.
                    IntPtr graphicGc = X11lib.XCreateGC(display, window, (TUlong)0, IntPtr.Zero);
                    if (graphicGc != IntPtr.Zero)
                    {
                        X11lib.XSetClipMask(display, graphicGc, maskPixmap);
                        X11lib.XSetClipOrigin(display, graphicGc, (TInt)0, (TInt)0);

                        // Draw graphic using the clipping graphics context.
                        X11lib.XPutImage(display, pixmap, graphicGc, _graphicXImage, (TInt)0, (TInt)0,
                                         (TInt)0, (TInt)0, (TUint)_width, (TUint)_height);

                        // Restore previous behaviour and clean up.
                        X11lib.XSetClipMask(display, graphicGc, IntPtr.Zero);
                        X11lib.XSetClipOrigin(display, graphicGc, (TInt)0, (TInt)0);
                        // Console.WriteLine (CLASS_NAME + "::Draw () Delete clipping image GC.");
                        X11lib.XFreeGC(display, graphicGc);
                        graphicGc = IntPtr.Zero;
                    }
                    else
                    {
                        Console.WriteLine(CLASS_NAME + "::Draw () ERROR: Can not create graphics context for transparency application.");
                    }
                }
                else
                {
                    X11lib.XPutImage(display, pixmap, pixmapGc, _graphicXImage, (TInt)0, (TInt)0, (TInt)0, (TInt)0, (TUint)_width, (TUint)_height);
                    // Console.WriteLine (CLASS_NAME + "::CreateIndependentGraphicPixmap () Delete graphic image GC.");
                    X11lib.XFreeGC(display, pixmapGc);
                    pixmapGc = IntPtr.Zero;
                }
            }
            else
            {
                Console.WriteLine(CLASS_NAME + "::CreateIndependentGraphicPixmap () ERROR: Can not create graphics context for graphic pixmap.");
            }
            return(pixmap);
        }