title: Offscreen divs doesn't work with html2canvas
body: <p>I'm using html2canvas to capture some divs. All works fine if the div is onscreen at the time of capture. But if I happen to scroll down the page and the div is off screen at that time, then it doesn't capture the div. The canvas output is generally blank for off-screen captured divs. How can I fix this? How can I capture a div even if the div is on-screen or off-screen?</p>
  
  <pre><code>  var elem = document.getElementById('myElem');
       document.querySelector("button").addEventListener("click", function() {
          html2canvas(document.querySelector("#content"), {
             canvas: elem,
             width: 200,
             height: 250,
             useCORS: true
         }).then(function(canvas) {
             console.log('Drew on the existing canvas');
         });
     });
  </code></pre>