function graph_canvas() {

  /*$chart['points'][] = array(0, 0);*/
  $chart['points'][] = array(40, 90);
  $chart['points'][] = array(80, 90);
  $chart['points'][] = array(120, 180);
  $chart['points'][] = array(160, 300);
 
  $config['fillcolor'] = '#0077f2';
  $config['txtcolor'] = 'black';
  $config['labelcolor'] = 'black';
  $config['height'] = 400;
  $config['width'] = 700;
  $config['xtics_height'] = 10;
  $config['ytics_height'] = 10;
  $config['ytics_stepsize'] = 50;

  $config['labels'] = array(
    'inside' => TRUE,
  );

  $config['theme'] = array(
    'fill' => '#0000ff',
    'fill_0' => '#0000ff',
    'fill_1' => '#3333ff',
    'fill_2' => '#6666ff',
    'fill_3' => '#9999ff',
    'fill_4' => '#ccccff',
    'fill_5' => '#eeeeff',
  );

  /*return module_invoke('drawing_graph', 'histogram', $chart, $config);*/
  return module_invoke('drawing_graph', 'piechart', $chart, $config);
}