title: How to Lock RectTransform's fields
body: <p>I'm creating custom layout group and I want to control <code>RectTransform</code> on the child Objects. I want to lock some fields on child's <code>RectTransform</code> like when using canvas or Unity's Horizontal or Vertical group so that it cannot be modified.</p>
  
  <p>I need the same effect. You can see this message on top of child's <code>RectTransform</code> : Some values driven by HorizontalLayoutGroup</p>
  
  <p><a href="https://i.stack.imgur.com/8l8Uf.png" rel="noreferrer"><img src="https://i.stack.imgur.com/8l8Uf.png" alt="enter image description here"></a></p>
  
  <p>I find a halfway :</p>
  
  <p>Adding <code>[ExecuteInEditMode]</code> then:</p>
  
  <pre><code>public void Update()
  {
  #if UNITY_EDITOR
      if (!Application.isPlaying)
      {
          /* Todo =&gt; update child's positions here. */
      }
  #endif
  }
  </code></pre>
  
  <p>Any other idea?</p>