title: Fabric.js fillRule - evenodd (subtract shapes)
body: <p>I am trying to do hole in the polygon using fillRule = 'evenodd' in fabric.js</p>
  
  <p>globalCompositeOperation won't work for me, because I need to see shape in the polygon hole
  <a href="https://i.stack.imgur.com/fDhur.png" rel="nofollow noreferrer">like this</a></p>
  
  <p>Here is my code: <a href="http://jsfiddle.net/y6RDB/189/" rel="nofollow noreferrer">fiddle</a></p>
  
  <p>There are 2 examples:</p>
  
  <ul>
  <li>Fabric.js 2 polygons (doesn't work)</li>
  <li>native html5 canvas 2 polygons (works)</li>
  </ul>
  
  <p>When I set fillRule: 'evenodd' for fabric.js polygon, it is going to the fabric function and it's setting context fill to 'eveneodd'</p>
  
  <pre><code>_renderFill: function(ctx) {
     ...
        if (this.fillRule === 'evenodd') {
          ctx.fill('evenodd');
        }
        ...
        ctx.restore();
      },
  </code></pre>
  
  <p>But still it doesn't work.
  Please, give my some idea how to use 'enevodd' if fabric.js</p>