When I test Bug 1666587, I found a bug when HWA is disabled.

Steps to reproduce:

1. Disable HWA
   about:preferences > uncheck "Use recommended performance settings" > uncheck "Use hardware acceleration when available"
   and Restart
2. Open https://louisabraham.github.io/world-of-abraham/client/

Actual results:
Nothing is showing up.

Expected results:
The game should be displayed.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=f9ad61f28238ae653a5e36bd73016f70a4b30fbc&tochange=fb95cf4f316a571a38efd4ff0d4aedba5c9f0089

I confirmed the problem on my Win10 PC with the following error log.

JavaScript warning: https://louisabraham.github.io/world-of-abraham/client/pixi/pixi.js, line 3998: Failed to create WebGL context: failIfMajorPerformanceCaveat: Compositor is not hardware-accelerated.
JavaScript warning: https://louisabraham.github.io/world-of-abraham/client/pixi/pixi.js, line 3999: Failed to create WebGL context: failIfMajorPerformanceCaveat: Compositor is not hardware-accelerated.
JavaScript error: https://louisabraham.github.io/world-of-abraham/client/pixi/pixi.js, line 21976: Error: WebGL unsupported in this browser, use "pixi.js-legacy" for fallback canvas2d support.

The severity field is not set for this bug.
:jgilbert, could you have a look please?

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Hmm, that regression window is suspect, but based on the code and behavior it sounds like this is working as intended on our side.

It sounds like pixi.js is demanding failIfMajorPerformanceCaveat: true. The right thing for us to do is say "sorry but we can't give you WebGL without any major performance caveat", since software rendering is a major performance caveat.
pixi.js SHOULD ultimately fall back to failIfMajorPerformanceCaveat: false/undefined.

For users who want to override this signal, in about:config we have "webgl.disable-fail-if-major-performance-caveat".
Maaaaybe this should be part of the options page, so users can uncheck "Use hardware acceleration when available", and also potentially uncheck something like "Allow websites to know if Firefox anticipates poor WebGL performance".