Text flickers in Firefox on changing attributes when Open Sans is part of the font stack

[designakt]

IODIDE revision 5d17a16

What I Did

What I Expected

no flicker (see Chrome in image above)

What Happened

flicker on change of attributes - also if changed through code, not just when changed in the inspector - which results in a flicker on load if changes are made to the page.

(if applicable) notebook that reproduces bug

https://iodide.telemetry.mozilla.org/notebooks/373/

[wlach]

@designakt I actually suspect this might be a bug in Firefox itself. What version of MacOS X and Firefox are you using? I can't actually reproduce on Mojave/Nightly here.

We should probably try to find a way to reproduce this in a more "normal" environment (e.g. a simple html page)

[designakt]

I suspected that too, and tried replicating in codepen, but couldn't.
I am using Firefox Nightly on Windows 10, and can replicate on Firefox release on Windows 10 as well as Nightly on macOS Catalina.