<!DOCTYPE HTML> <html> <title>Mask layer on canvas layer needs to update even if canvas wasn't dirtied</title> </style> <canvas id="canvas" height="100" width="200" style="border-radius: 40px;"></canvas> <script> var canvas = document.getElementById("canvas"); var cx = canvas.getContext("2d"); cx.fillStyle="lime"; cx.fillRect(0, 0, 200, 100); </script>