fix: bind mouse events in web worker

[CarterLi]

Web workers do support addEventListener ( aka. EventTarget ) and requestAnimationFrame, but worker do not have the global object window.

Instead of window, we should use a better option to get the global object. globalThis is the best option indeed, but we can't use it due to its poor compatibility. Browser and worker both support self, and it has very good browser compatibility. Using self can be a better option than using window.

This PR generally enables OffscreenCanvas support of zrender, which may greatly improve the performance of echarts.

Ref: apache/echarts#9232

[yuqianma]

Good catch!
But maybe it's unnecessary to instance a handlerProxy?
I had bypassed the proxy and used the handler directly in a different case.

[CarterLi]

I had bypassed the proxy and used the handler directly in a different case.

I'm not sure I understand what you mean, but do you mean using zrender.handler directly?

I know I can access zrender.handler by using echartsInstance._zr.handler, but I don't know if it's a good idea of accessing the private _zr property. AFAIK triggering mouse events using dispatchEvent is a much easier way to reuse existing code.

[yuqianma]

Got it. It's reasonable in echarts.
I'm using zrender alone. Considering some non-browser environments, I keep dom event things away to make it easier.

[CarterLi]

I have tried bypassing handlerProxy by calling echartsInstance._zr.zrender.trigger directly (zrX, zrY and friends are set before), and got various errors.

I gave up, and reverted back to dispatchEvent on OffscreenCanvas.

[CarterLi]

It has been more than 1 year, any chance to review this?

I have tested that even IE5 ( with IE11 compatible mode though ) supports self

[pissang]

@CarterLi Sorry for missing this PR.

addEventListener in web worker is for receiving messages. It doesn't have the function of listening to mouse events. Ignoring it and still treat it as in the dom environment may lead to other problems in the further.

About mouse event. Perhaps you can reference to the code in ECharts GL.
https://github.com/ecomfe/echarts-gl/blob/master/src/util/EChartsSurface.js#L140

It does a similar thing.

[CarterLi]

Thanks @pissang