rustdoc: strange font rendering issue

[ehuss]

On the recently nightlies, I've noticed that all <code> and <pre> text is being rendered with all black text on Firefox (66.0.3) on macOS only. This is particularly difficult to read with the dark theme.

Latest nightly	Previous Versions

I bisected the change to #60146 (first starting with nightly-2019-04-24). cc @Manishearth

Other browsers and OSs don't seem to be affected. I tried with a brand new firefox profile, and I also tested on multiple macs, all with the same results. Turning off "Source Code Pro" in the CSS inspector fixes the color.

This seems very peculiar, so I was wondering if anyone else can reproduce it.

[Manishearth]

A quick fix would be to revert the Source Code Pro update, the Source Serif Pro one is the only important one. I'd like to keep our fonts up to date though.

But it looks like either the font or the OS stack is buggy here, and we should investigate that.

(Works fine on Firefox for Android, have no Macs to test)

[GuillaumeGomez]

That is surprising indeed. I can take a look on mac.

[Manishearth]

Temporary fix: #60382

[ehuss]

This seems to be fixed now (thanks!).

This is a known bug in Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1520157

Is it worth keeping this issue open? The newer versions of Source Code Pro have a few newer glyphs and updates, but I don't know if there are any improvements that are important at this time.

For details, the version used in rustdoc is 1.017 which has 965 glyphs. The latest version of 2.030 has 1585 glyphs. Google fonts serves 1.017. Adobe's typekit serves 2.010, but with a very small subset of glyphs (393).

I would be inclined to just close this for now. The only alternative I can think of is someone could rebuild the fonts from source, removing the colored/svg glyphs to avoid the firefox issue. Or could wait for it to be fixed in Firefox, but I'm not sure what rustdoc's browser compatibility rules are.