title: How to position widget according to other widget's preferred size?
body: <p>In my app, widgets need to be placed relative to each other. One widget's position is determined by other widgets' preferred widths and heights.</p>
  <p>How am I to access one widget's preferred dimensions while building the other widgets?</p>
  <p>Example:</p>
  <p><a href="https://i.stack.imgur.com/zNOaR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zNOaR.png" alt="screenshot" /></a></p>
  <p>In this example</p>
  <ul>
  <li>&quot;2&quot; widget's top is aligned to &quot;1&quot; widgets height.</li>
  <li>&quot;2&quot; widget's left is aligned to &quot;1&quot; widget's width.</li>
  <li>&quot;3&quot; widget's top is aligned to sum of &quot;1&quot; widget and &quot;2&quot; widgets' height.</li>
  </ul>