title: Getting a single screenshot of browser using getDisplayMedia without prompting user
body: <p>I am building an online app and on click of a button I want to be able to screenshot what the user sees in their browser(my app).  I've looked at lots of js libraries such as html2canvas, CCapture as dom-to-image but my page will have a mixture of html, svg, canvas and webgl content and none of the solutions I have found seem to capture it perfectly.</p>
  
  <p>I then came across the <a href="https://developer.mozilla.org/en-US/docs/Web/API/Screen_Capture_API/Using_Screen_Capture" rel="noreferrer">Screen Capture API</a> and getDisplayMedia.</p>
  
  <p>All examples I can find always ask which tab/application/screen you want to share then have a live stream of your chosen page.</p>
  
  <p>Ideally I don't want the user to do anything other than click the capture button and it to capture a single image (data url) of the page that the user initiated the function on.  I can then use that dataurl elsewhere.</p>
  
  <p>Any advise would be greatly appreciated</p>