Error at instanceof SVGElement in WebLayer3D

[blairmacintyre]

While trying to run the demo at https://argonjs.github.io/three-web-layer/ on servo for mac, I got a bunch of these errors:

ERROR 2019-03-10T19:42:56Z: script::dom::bindings::error: Error at https://argonjs.github.io/three-web-layer/app.c61986b1.js:5:4695 invalid 'instanceof' operand d(...).SVGElement

@asajeffrey suggested I post an issue.

[jdm]

This is caused by us not implementing the SVGElement DOM interface (since we have no SVG support), so any code using instanceof SVGElement fails.

[blairmacintyre]

Right, thanks. I think this is something deep in the HTML2Canvas package (turns out its in a ResizeObserver polyfill, will keep investigating), which is checking if there's SVG Elements so it can handle them (even if there aren't SVG elements).

Not sure what to do about this.

[blairmacintyre]

Ok, for fun, we added

window.SVGElement = class {}
window.SVGSVGElement = class {}

to the app, which stopped these crashes, but now html2canvas is throwing errors because canvas2d.fillText isn't implemented.

Related to issue #11681

[jdm]

@blairmacintyre That link no longer exists; is there a better one to use?

[blairmacintyre]

https://www.aelatgt.org/three-web-layer/# Moved to more appropriate org

[blairmacintyre]

@jdm wondered if this has an update. FWIW, the current version of servo (downloaded just now from nightly builds on the mac) gives both the SVGElement error and
canvas::canvas_data] Unimplemented canvas2d.fillText. Values received: 1 MS (1-150), 6, 4, None. errors

[jdm]

No update yet - there's a student just starting to work on some basic SVG support which may help eventually.

[blairmacintyre]

Is the fillText related? We could remove SVGs from this example I think ...

[jdm]

As far as I know, fillText just causes a warning to appear in the terminal but shouldn't interrupt JS execution.