1996226 - Allow use system fonts for advanced usage

Status: UNCONFIRMED

(GeckoView :: PDF Viewer, enhancement)

Description

[Celeste Liu [:Coelacanthus]]

Steps to reproduce:

There are so many issues related to fallback to metric incompatible font and have overlapped render result, so Calixte Denizet (:calixte) disabled useSystemFonts option of GeckoView entirely. But for some advanced Android users, we unlocked our bootloader so we can modify the system to add fonts we like. In this situation, we can ensure we have a metric-compatible font available, but Firefox Android disallows us from using it.
I propose adding a new option pdfjs.useSystemFonts in about:config, which maps to pdfjs.useSystemFonts option, just like other pdfjs.* prefs in about:config. Since about:config is only available in Firefox Android Dev or Nightly version, it can be treated feature for advanced users, and can't be accessed by normal users. So advanced users can gain the best experiences, normal users get correct behavior, and no need to worry about misconfiguration.

Actual results:

There is no such option in about:config to control the pdf.js useSystemFonts option.

Expected results:

There is an option in about:config to control the pdf.js useSystemFonts option.