2012226 - FOUT mitigation delay cannot be disabled

Status: UNCONFIRMED

(Core :: Graphics: Text, defect)

Description

[M M]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:146.0) Gecko/20100101 Firefox/146.0

Steps to reproduce:

FOUT -> Flash of unstyled text, a symptom of downloadable fonts.

0. Disable custom fonts, downloadable fonts etc:

   browser.display.use_document_fonts 0
   gfx.downloadable_fonts.enabled false

1. Use an outbound firewall to block unwanted requests (font spying)

2. Browse a web page that uses downloadable fonts, such as fonts.googleapis.com. e.g.

   https://fedoramagazine.org/working-with-btrfs-subvolumes/

3. Get stuck for ~30 seconds the first and every time you load a page,
   every time you refresh, every time you click a link to another page.

Actual results:

Since spying though google fonts, and other sites (typekit etc), is endemic to the web, trying to block them creates an unusable browsing situation.

I think this is caused by an intentional delay to avoid FOUT. The delay should not happen when downloadable, custom fonts are disabled.

But instead, despite being disabled, the tab hangs waiting to contact a server that will never respond! Does DNS lookup too! Why? ;-)

Expected results:

Extremely snappy response due to skipping font downloading nonsense.

Comment 1

[M M]

By the way, I tried reducing this setting down to 100, 1, and 0, but it didn't make any difference:

gfx.downloadable_fonts.fallback_delay 1

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Networking: DNS' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.