/// <summary> Measure the text using the default font of indicated graphics context. </summary>
        /// <param name="display"> The display pointer, that specifies the connection to the X server. <see cref="IntPtr"/> </param>
        /// <param name="gc"> The crapchics context to use for measuring. <see cref="IntPtr"/> </param>
        /// <param name="text"> The text to measure. <see cref="X11.TChar[]"/> </param>
        /// <returns> The measured size of the indicated text. <see cref="TSize"/> </returns>
        public virtual TSize MeasureTextLine(IntPtr display, IntPtr gc, X11.TChar[] text)
        {
            TSize result = new TSize(5, 5);

            if (display == IntPtr.Zero)
            {
                Console.WriteLine(CLASS_NAME + "::MeasureTextLine () ERROR: Argument null: display");
                return(result);
            }
            if (gc == IntPtr.Zero)
            {
                Console.WriteLine(CLASS_NAME + "::MeasureTextLine () ERROR: Argument null: gc");
                return(result);
            }

            TInt gcID = X11lib.XGContextFromGC(gc);

            if (gcID != 0)
            {
                TInt direction   = 0;
                TInt fontAscent  = 0;
                TInt fontDescent = 0;
                X11lib.XCharStruct xCharStruct = new X11lib.XCharStruct();

                X11lib.XQueryTextExtents(display, gcID, text, (X11.TInt)text.Length, ref direction, ref fontAscent, ref fontDescent, ref xCharStruct);
                result.Width  = (int)xCharStruct.width;
                result.Height = (int)fontAscent + (int)fontDescent;
            }
            else
            {
                Console.WriteLine(CLASS_NAME + "::MeasureTextLine () ERROR: Cannot investigate default font ressource ID of underlaying graphics context.");
            }
            return(result);
        }