# File gtkglext/sample/font.rb, line 39
def realize(w)
    glcontext = w.gl_context
    gldrawable = w.gl_drawable

    light_diffuse  = [1.0, 0.0, 0.0, 1.0]
    light_position = [1.0, 1.0, 1.0, 0.0]

    #*** OpenGL BEGIN ***
    gldrawable.gl_begin(glcontext) do
        # Generate font display lists.
        $font_list_base = GL.GenLists(128)

        font_desc = Pango::FontDescription.new FONT_STRING

        font = Gdk::GL.use_pango_font(font_desc, 0, 128, $font_list_base)
        if !font
            puts "*** Can't load font '#{FONT_STRING}'\n"
            exit 1
        end

        font_metrics = font.metrics
        $font_height = font_metrics.ascent + font_metrics.descent
        $font_height = Pango.pixels($font_height)

        GL.ClearColor(1.0, 1.0, 1.0, 1.0)
        GL.ClearDepth(1.0)

        GL.Viewport(0, 0, w.allocation.width, w.allocation.height)

        GL.MatrixMode(GL::PROJECTION)
        GL.LoadIdentity
        GL.Ortho(0.0, w.allocation.width,
                 0.0, w.allocation.height,
                 -1.0, 1.0);

        GL.MatrixMode(GL::MODELVIEW)
        GL.LoadIdentity
    end
end