File: device-pixel-ratio-ref.html

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<!DOCTYPE html>
<html>
<style>
html, body { margin: 0; padding: 0; }
canvas {width: 150px; height: 150px; }
</style>
<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>
<canvas id ="canvas" width="100" height="100"></canvas>
<script>
var canvas = document.getElementById('canvas');
canvas.width = 150 * window.devicePixelRatio;
canvas.height = 150 * window.devicePixelRatio;
var context = canvas.getContext("2d");
context.fillStyle = 'green';
var draw_width = Math.floor(canvas.width / window.devicePixelRatio);
var draw_height = Math.floor(canvas.height / window.devicePixelRatio);
context.fillRect(0, 0, draw_width, draw_height);
</script>
</body>
</html>