title: Change context properties from QML code
body: <p>Main goal: have a context property that is set by a item defined into a QML file (say <code>file_1.qml</code>), and which will be accessed at runtime by other item defined in a different QML file (say <code>file_2.qml</code>).</p>
  
  <p>Question: Is it possible to set a new context property in <code>file_1.qml</code> and then read this property in <code>file_2.qml</code>?</p>
  
  <p>(edit)</p>
  
  <p>For example, I would need to use a value from file_2.qml in file_1.qml:</p>
  
  <p>file_1.qml:</p>
  
  <pre><code>(...)
  UiController.but_generate__onClicked(
     getContextProperty("sbx_money_quantity_value"),
     cal_daysoff.visibleMonth)
  (...)
  </code></pre>
  
  <p>file_2.qml:</p>
  
  <pre><code>(...)
  SpinBox {
          id: sbx_money_quantity
          objectName: "sbx_money_quantity"
          Layout.fillWidth: true
          minimumValue: 0
          maximumValue: 100000
          value: 20000
  
  
          onChanged: setContextProperty("sbx_money_quantity_value",value)
      }
  (...)
  </code></pre>
  
  <p>Thanks!</p>