css/css-paint-api/hidpi/device-pixel-ratio.https.html

<!DOCTYPE html>
<html class="reftest-wait">
<link rel="help" href="https://drafts.css-houdini.org/css-paint-api/">
<link rel="match" href="device-pixel-ratio-ref.html">
<style>
html, body { margin: 0; padding: 0; }
.container {
  width: 150px;
  height: 150px;
}

#canvas-geometry {
  background-image: paint(geometry);
}
</style>
<script src="/common/reftest-wait.js"></script>
<script src="/common/worklet-reftest.js"></script>
<body>
<p>This test ensures that the PaintWorkletGlobalScope.devicePixelRatio returns
the correct value, which should be identical as window.devicePixelRatio. To
manually test, open both this file and "device-pixel-ratio-ref.html" with a
browser, and you should see two idential green rectangles.</p>
<div id="canvas-geometry" class="container"></div>

<script id="code" type="text/worklet">
registerPaint('geometry', class {
    paint(ctx, geom) {
        ctx.fillStyle = 'green';
        var draw_width = Math.floor(geom.width / devicePixelRatio);
        var draw_height = Math.floor(geom.height / devicePixelRatio);
        ctx.fillRect(0, 0, draw_width, draw_height);
    }
});
</script>

<script>
    importWorkletAndTerminateTestAfterAsyncPaint(CSS.paintWorklet, document.getElementById('code').textContent);
</script>
</body>
</html>