title: How to fill a path with gradient
body: <p>I have a graph view that draws a path to some points like this:
  <img src="https://i.stack.imgur.com/Tryrl.png" alt="enter image description here"></p>
  
  <p>now I want to fill the inner area of graph with a gradient color
  how can I achieve this ?</p>
  
  <p>Thanks</p>
  
  <p><strong>Edit:</strong>
  @Lumis
  I added another closed path and set the shader and it was like this:
  <img src="https://i.stack.imgur.com/ors50.png" alt="enter image description here"></p>
  
  <p>but there is a gradient color in the outer area of the graph, how can I avoid this ?</p>