title: Disable gesture to pull down form/page sheet modal presentation
body: <p>In iOS 13 modal presentations using the form and page sheet style can be dismissed with a pan down gesture. This is problematic in one of my form sheets because the user draws into this box which interferes with the gesture. It pulls the screen down instead of drawing a vertical line.</p>
  
  <p>How can you disable the vertical swipe to dismiss gesture in a modal view controller presented as a sheet?</p>
  
  <p>Setting <code>isModalInPresentation = true</code> still allows the sheet to be pulled down, it just won't dismiss.</p>