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Test Info: Warnings
- This test has a WPT meta file that expects 1 subtest issues.
- This WPT test may be referenced by the following Test IDs:
- /html/canvas/offscreen/manual/draw-element-image/offscreenCanvas-drawElementImage-worker.tentative.html - WPT Dashboard Interop Dashboard
<!DOCTYPE HTML>
<title>OffscreenCanvas.drawElementImage should work in a worker thread</title>
<script src='/resources/testharness.js'></script>
<script src='/resources/testharnessreport.js'></script>
<script src="/html/canvas/resources/wait-for-canvas-paint.js"></script>
<style>
#child {
width: 100px;
height: 100px;
background: green;
}
</style>
<canvas id="canvas" width="200" height="200" layoutsubtree>
<div id="child"></div>
</canvas>
<script>
'use strict';
const workerCode = `
let ctx;
self.onmessage = function(e) {
if (e.data.canvas) {
ctx = e.data.canvas.getContext('2d');
}
if (e.data.elementImage) {
ctx.drawElementImage(e.data.elementImage, 0, 0);
self.postMessage(ctx.getImageData(0, 0, 1, 1).data);
}
};
`;
promise_test(async t => {
await waitForCanvasPaint(canvas);
const blob = new Blob([workerCode], { type: 'application/javascript' });
const worker = new Worker(URL.createObjectURL(blob));
const offscreen = canvas.transferControlToOffscreen();
worker.postMessage({ canvas: offscreen }, [offscreen]);
const green_promise = new Promise(resolve => {
worker.onmessage = t.step_func(msg => {
if (msg.data instanceof Uint8ClampedArray) {
assert_array_equals(msg.data, [0, 128, 0, 255]);
resolve();
} else {
assert_unreached();
}
})
});
let elementImage = canvas.captureElementImage(child);
worker.postMessage({ elementImage: elementImage }, [elementImage]);
return green_promise;
}, 'OffscreenCanvas.drawElementImage should work in a worker thread');
</script>