How to use HTML5 and transferControlToProxy?
Question
I work on an JS application which use canvas to manipulate a picture (ie and convert to png/base64 with .toBlob() and .toDataURL() .
I would use .transferControlToProxy() to let a worker do the job and get a smooth GUI.
But it seems to be unsupported... as they said on Mozilla devs
Some of you have other information ? Maybe a workaround ?
1 answers
solution1
1 2015-09-08 07:10:30
Whatwg.org has a javascript sample of using canvas.transferControlToProxy() at https://developers.whatwg.org/the-canvas-element.html#dom-canvas-transfercontroltoproxy , but it does not seem to work in any browser, even not in bleeding edge versions (Chrome Canary or Opera Next).
Even turning "Enable experimental canvas features" at chrome://flags has no effect in Chrome Canary.
Test live: http://jsbin.com/bocoti/5/edit?html,output
It says: "TypeError: canvas.transferControlToProxy is not a function".
This would be a very fine addition. Think of drawing everything on canvas in a worker and make a blob/arraybuffer/dataurl of canvas and transfer this to main thread using Transferable objects. Nowadays if you want to draw something on canvas using canvas functions (fill(), drawImage() etc.), you have to do it in main thread...
<!DOCTYPE html><html><head><meta charset="utf-8" /></head><body>
<div id="log"></div>
<canvas style="border:1px solid red"></canvas>
<script id="worker1" type="javascript/worker">
self.onmessage = function(e) {
var context = new CanvasRenderingContext2D();
e.data.setContext(context); // event.data is the CanvasProxy object
setInterval(function () {
context.clearRect(0, 0, context.width, context.height);
context.fillText(new Date(), 0, 100);
context.commit();
}, 1000);
}
</script>
<script>
var blob = new Blob([document.querySelector('#worker1').textContent]);
var worker = new Worker(window.URL.createObjectURL(blob));
worker.onmessage = function(e) {
//document.querySelector("#log").innerHTML = "Received: " + e.data;
}
var canvas = document.getElementsByTagName('canvas')[0];
try { var proxy = canvas.transferControlToProxy();
worker.postMessage(proxy, [proxy]);}
catch(e) { document.querySelector("#log").innerHTML = e; }
</script>
<br>
From: <a href="https://developers.whatwg.org/the-canvas-element.html#the-canvas-element">https://developers.whatwg.org/the-canvas-element.html#the-canvas-element</a>
</body></html>
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