title: Adjusting width / horizontalAlignment with SwiftUI
body: <p>I have the following layout achieved in <code>SwiftUI</code>:</p>
  
  <pre><code>VStack {
    TextField(...)
    TextField(...)
    Button(...)
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Imb1y.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Imb1y.png" alt="enter image description here"></a></p>
  
  <p>I tried making my VStack to be 50% of the superview, so I added the following modifier:</p>
  
  <pre><code>VStack { ... }
    .relativeWidth(0.5)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/9rrj4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9rrj4.png" alt="enter image description here"></a></p>
  
  <p>Not quite 50% of the superview, but I'm more interested in achieve horizontal centering. Anyone know how to achieve that in SwiftUI?</p>
  
  <p>There's a <code>alignmentGuide(_:computeValue:)</code> modifier that's available, but I'm struggling to give the correct inputs to satisfy the compiler.</p>