public void LoadSample(DemoBase demobase)
        {
            this.demobase = demobase;
            //1.
            //note:when we init,
            //no glcanvas/ painter are created
            demobase.Init();
            //-----------------------------------------------
            //2. check if demo will create canvas/painter context
            //or let this GLDemoContext create for it

            hh1 = glControl.Handle; //ensure that contrl handler is created
            glControl.MakeCurrent();

            demobase.BuildCustomDemoGLContext(out this._glsx, out this.canvasPainter);
            //
            if (this._glsx == null)
            {
                //if demo not create canvas and painter
                //the we create for it
                int max = Math.Max(glControl.Width, glControl.Height);
                _glsx            = PixelFarm.Drawing.GLES2.GLES2Platform.CreateGLRenderSurface(max, max, glControl.Width, glControl.Height);
                _glsx.SmoothMode = SmoothMode.Smooth;//set anti-alias
                canvasPainter    = new GLPainter(_glsx);
                //create text printer for opengl
                //----------------------
                //1. win gdi based
                //var printer = new WinGdiFontPrinter(_glsx, glControl.Width, glControl.Height);
                //canvasPainter.TextPrinter = printer;
                //----------------------
                //2. raw vxs
                //var openFontStore = new Typography.TextServices.OpenFontStore();
                //var printer = new PixelFarm.Drawing.Fonts.VxsTextPrinter(canvasPainter,openFontStore);
                //canvasPainter.TextPrinter = printer;
                //----------------------
                //3. agg texture based font texture

                //var printer = new AggTextSpanPrinter(canvasPainter, glControl.Width, 30);
                //canvasPainter.TextPrinter = printer;
                //----------------------
                //4. texture atlas based font texture
                //------------
                //resolve request font
                var printer = new GLBitmapGlyphTextPrinter(canvasPainter, PixelFarm.Drawing.GLES2.GLES2Platform.TextService);
                canvasPainter.TextPrinter = printer;

                //var openFontStore = new Typography.TextServices.OpenFontStore();
                //var printer = new GLBmpGlyphTextPrinter(canvasPainter, openFontStore);
                //canvasPainter.TextPrinter = printer;
            }

            //-----------------------------------------------
            demobase.SetEssentialGLHandlers(
                () => this.glControl.SwapBuffers(),
                () => this.glControl.GetEglDisplay(),
                () => this.glControl.GetEglSurface()
                );
            //-----------------------------------------------
            this.glControl.SetGLPaintHandler((s, e) =>
            {
                demobase.InvokeGLPaint();
            });
            DemoBase.InvokeGLContextReady(demobase, this._glsx, this.canvasPainter);
            DemoBase.InvokePainterReady(demobase, this.canvasPainter);
        }