title: SwiftUI: Error in dragging logic or is this a bug?
body: <p>SwiftUI is in beta, so maybe this is a bug, but I've seen something like this working in others YouTube videos so perhaps it's not, the test is pretty simple. I'm creating a circle I can drag around on horizontally.</p>
  
  <pre class="lang-swift prettyprint-override"><code>import SwiftUI
  
  struct ContentView : View {
      @State private var location = CGPoint.zero
      var body: some View {
          return Circle()
              .fill(Color.blue)
              .frame(width: 300, height: 300)
              .gesture(
                  DragGesture(minimumDistance: 10)
                      .onChanged { value in
                          print("value.location")
                          print(value.location)
                          self.location = CGPoint(
                              x: value.location.x,
                              y: 0)
                  }
          )
              .offset(x: self.location.x, y: self.location.y)
      }
  }
  
  #if DEBUG
  struct ContentView_Previews : PreviewProvider {
      static var previews: some View {
          ContentView()
      }
  }
  #endif
  </code></pre>
  
  <p>This results in the behavior:</p>
  
  <p><a href="https://i.stack.imgur.com/jBfIu.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jBfIu.gif" alt="iphone capture"></a></p>
  
  <p>As far as I can tell, the <code>value.location</code> value in the <code>DragGesture</code> <code>onChanged</code> callback shouldn't be fluctuating between numbers like this. Looking at the logs the numbers are all over the place. Am I missing something?</p>