title: why I see the background of the div under the canvas
body: <p>I'm trying to scroll a canvas inside a div. The problem that when I try to scroll I see a red line part of the red background of the div below instead I would expect to see everything entirely black.</p>
  
  <p>HTML:</p>
  
  <pre><code>   &lt;div id="Div1" style=" float: left; width: 150px; height: 200px; background: red; overflow:scroll; "&gt;
      &lt;canvas id="myCanvas1" width="200px" height="500px" style="border:0px solid #ff0000;"&gt;asdf asd as asfqwe asd asdfasdf asd as asfqwe asd asdfasdf asd as asfqwe asd asdf&lt;/canvas&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>JAVASCRIPT:</p>
  
  <pre><code> var c = document.getElementById("myCanvas1");
      var ctx = c.getContext("2d");
      ctx.fillRect(0, 0, 200, 500);
      ctx.fillStyle = "#00ff00";  //&lt;======= here
      ctx.font = '35px serif';
      ctx.fillText('Hello world', 0, 40);
  </code></pre>
  
  <p>CSS:</p>
  
  <pre><code>canvas { border: 0px solid black; }
  </code></pre>
  
  <p>This is a minimal example:
  <a href="https://jsfiddle.net/alessio211734/vL4whdc0/17/" rel="nofollow noreferrer">https://jsfiddle.net/alessio211734/vL4whdc0/17/</a></p>