Found in

• Nighty 114.0a1

Affected versions

• Nightly 114.0a1

Tested platforms

• Affected platforms: Mac 13 and Ubuntu 20.04
• Unaffected platforms: Windows 11

Preconditions

• in about:config, set the preference "layout.css.font-visibility.private" to 1.

Steps to reproduce

1. Open a private window.
2. Navigate to Wikipedia and look for the following languages: Gothic, Old Italic, Old Turkic, Runic.
3. Observe the Ancient Historic group fonts.

Expected result

• The fonts should pe properly displayed in Private Browsing.

Actual result
During private browsing, the following languages are displaying tofu boxes:

• Gothic, Old Italic on macOS.
• Old Italic, Old Turkic, Runic on Ubuntu 20.04

Regression range
This is not a regression, this preference is set to 3 on all previous versions: ESR, Beta and Release.

Additional notes

• The tofu boxes are also displayed when the preference "layout.css.font-visibility.private" is set to 2.
• The tofu boxes are not displayed in normal browsing or when "layout.css.font-visibility.private" is set to 3.

:obotisan, if you think that's a regression, could you try to find a regression range using for example mozregression?

The issue is still reproducible on Ubuntu 22.04 x64 with Old Italic, Old Turkic, Runic fonts installed on the machine. Tofu boxes are displayed in PBM, but not on normal window, when accessing the test pages from comment 0.

The issue is no longer reproducible on macOS 13.

(In reply to Ciprian Georgiu, Desktop QA from comment #2)

The issue is still reproducible on Ubuntu 22.04 x64 with Old Italic, Old Turkic, Runic fonts installed on the machine. Tofu boxes are displayed in PBM, but not on normal window, when accessing the test pages from comment 0.

What specific fonts are being used in the normal window to display these characters?

(In reply to Jonathan Kew [:jfkthame] from comment #3)

(In reply to Ciprian Georgiu, Desktop QA from comment #2)

The issue is still reproducible on Ubuntu 22.04 x64 with Old Italic, Old Turkic, Runic fonts installed on the machine. Tofu boxes are displayed in PBM, but not on normal window, when accessing the test pages from comment 0.

What specific fonts are being used in the normal window to display these characters?

I've inspected each script (via Devtools - Fonts inspector) and the fonts being used in normal windows are as follows:

• Old Italic - Noto Sans Old Italic
• Old Turkic - Noto Sans Old Turkic
• Runic - Noto Sans Runic

Let me know if we can help with more info!

Tested on On Ubuntu 22.04

• Old Italic & Runic - I see this rendered in FreeMono which I have installed and is listed in the base installed fonts.
• Old Turkic - I do not have Old Turkic installed, and I see Tofu Boxes everywhere regardless of pref value

We can chalk this up to locally installed langpack fonts - so it's working as intended.