title: Moving qml Item out of left side of window
body: <p>I want to move a qml Item out of the left side of the app window.
  While this task works perfectly for the right side of the window by defining a state like this</p>
  
  <pre><code>states: State {
      name: "hidden"
      when: is_hidden == true
  
      AnchorChanges {
          target: right_item_to_move
          anchors.right: undefined
      }
  
      PropertyChanges {
          target: right_item_to_move
          x: main_window.width
      }
  }
  </code></pre>
  
  <p>and defining the appropriate Transition, I can't get it to work on the left side of the main window because negative x coordinates are not allowed.
  I.e. this does not work:</p>
  
  <pre><code>states: State {
      name: "hidden"
      when: is_hidden == true
  
      AnchorChanges {
          target: left_item_to_move
          anchors.left: undefined
      }
  
      PropertyChanges {
          target: left_item_to_move
          x: -left_item_to_move.width
      }
  }
  </code></pre>
  
  <p>How can I achieve this task? I'm using Qt 5.8 and QtQuick 2.0.</p>