[Bug] Canvas alternate content is not displayed

Firefox 108.0.2 Disable JavaScript 2.3.1 Linux ... 6.1.2-arch1-1 #1 SMP PREEMPT_DYNAMIC Sat, 31 Dec 2022 17:40:35 +0000 x86_64 GNU/Linux

When I disable JS through this extension the alternative content is not shown in place of canvas elements. But when I disable JS globally through about:config javascript.enabled option alternative content appears.

According to this doc for canvas element:

Alternative content You should provide alternate content inside the

Example page:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Test canvas alternative content</title>
    <style>
      canvas {
        border: 1px solid black;
      }
    </style>
  </head>
  <body>
    <canvas width="300" height="300">
      Your browser does not support JavaScript!
    </canvas>
    <script>
      const canvas = document.querySelector("canvas");
      const ctx = canvas.getContext("2d");
      ctx.fillStyle = "green";
      ctx.fillRect(10, 10, 100, 100);
    </script>
  </body>
</html>

Run:

python -m http.server --bind 127.0.0.1 5000

When JS is enabled you should see a green rectangle. When JS in disabled through this extension I see empty canvas. When JS is disabled through about:config I see caption "Your browser does not support JavaScript!" as in Chromium when JS is disabled in chrome://settings/content/javascript

dpacassi / disable-javascript

[Bug] Canvas alternate content is not displayed #111