title: How to feed output of ShaderEffect back into the same ShaderEffect in QML/QtQuick2
body: <p><strong>Question</strong></p>
  
  <p>I want to feed the output of a ShaderEffect into itself, effectively generating a feedback loop.</p>
  
  <p>My naive attempts has included simply linking a ShaderEffectSource and a ShaderEffect like so:</p>
  
  <pre><code>    ShaderEffectSource {
          id:buf1;
          sourceItem:  effect;
      }
  
      ShaderEffect {
          id:effect;
          property variant src: buf1;
          //fragment shader then uses src as texture
      }
  </code></pre>
  
  <p>My next naive approach  included introducing a second ShaderEffectSource into the mix like so:</p>
  
  <pre><code>    ShaderEffectSource {
          id:buf1;
          sourceItem:  effect;
      }
  
      ShaderEffectSource {
          id:buf2;
          sourceItem:  buf1;
      }
  
      ShaderEffect {
          id:effect;
          property variant src: buf2;
          //fragment shader then uses src as texture
      }
  </code></pre>
  
  <p>Neither of these approaches work however. It seems to work in one step but never feeds back in the end.</p>
  
  <p>I have a feeling this is possible, but I am fairly new to QML and the quite possibly very logical and simple solution has eluded me. Any hints are welcome!</p>
  
  <p><strong>Answer</strong></p>
  
  <p>Answers with short working copy-pastable snippets are preferred :-)</p>