Re: exposing CANVAS or something like it to Web Workers

[Boris Zbarsky]

On 5/14/12 8:03 PM, Gregg Tavares (勤) wrote:
var canvasSurface = new CanvasSurface();
var ctx = canvasSurface.getContext("2d");
var pic = new Picture;
pic.src = "http://someplace.com/someimage.jpg";;
pic.onload = function() {
    ctx.drawImage(pic, 0, );
}
Let's assume you can instantiate these things in either the page or a
worker. Nether can be transfered.

Would that work? What problems would that have?

Two things that come to mind immediately:

1)  Various canvas 2d context methods depend on the styles of the canvas 
to define how they actually behave.  Clearly this would need some sort 
of changes for Workers anyway; the question is what those changes would 
need to be.

2)  How (or maybe whether) this should work with pic.src = 
"http://someplace.com/someimage.svg"; is an interesting question.

3)  This leaves open the question of how to get data from the worker 
back to the main thread to paint there.

#1 is an issue with any proposal that puts a 2d context in a worker.

#2 is only an issue if we do the image loads in workers somehow; if we 
wanted to just rasterize the SVG and pass the resulting data to the 
worker there would be no problem, obviously.

For #3, being able to transfer a canvas context from the page to a 
worker but leave it painting to the canvas may still be desirable...

-Boris