If I use a

<canvas id="myCanvas" width="200" height="100" style="border:1px solid #000000;"></canvas>

element in an iframe without sandboxing, it works fine and shows a box. But if I sandbox the iframe, the canvas disappears. I am trying to access the canvas and change it from the parent window so I can manipulate the canvas with a safe javascript interpreter without allowing javascript to run in the iframe. How do I make this possible?