[tor-bugs] #30832 [Applications/Tor Browser]: Fix tor-browser tbb-tests

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#30832: Fix tor-browser tbb-tests
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 Reporter:  acat                      |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  ReleaseTrainMigration     |  Actual Points:  3
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:  Sponsor58
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Comment (by Thorin):

 Replying to [comment:7 acat]:

 > using a div to measure, instead of a span

 Yeah. ... dcf's unicode glyphs test (which is also used as a base on TZP)
 - https://www.bamsoftware.com/talks/fc15-fontfp/fontfp.html#demo

 From my notes
 // Read the span width, but the div height. Firefox always reports the
 same value for the span's offsetHeight, even if the div around it is
 changing size


 ---

 I don't see a problem with "leaking" the major OS (Win, Mac, Android,
 Linux: we'll never stop that), its the entropy across Linux (and Android
 for now, see below) that worries me. And we should always make it as hard
 as possible for the bastards. The patch is still protecting most/all users
 from alternative measuring - e.g. domrect.

 FWIW: I also see occasional weird measurements, e.g. with textMetrics,
 with various codepoints and/or fonts: still trying to pinpoint exactly
 what it is: but I think it might mainly be to do with right-to-left.

 I'm not sure I see the issue with `Noto Naskh Arabic`: if all users are
 the same, then it's OK. Sure, it's not `19.2`, but it might just be an odd
 outlier (**for everyone**?). If someone is spoofing as English - their
 default font is Times New Roman. And if they're not, then they are already
 different: navigator languages etc - e.g. `TB-fa`. The question is, **is
 everyone the same**?

 #23104 also lacks ~~parity~~ effectiveness in Android (and least on my
 phone): it's doing **something** (toggle RFP) but it sure isn't 19.2
 either. I sent sysrqb an email about it months ago (last December) - it's
 something to with the 19.2 is only returned at certain zoom levels: and on
 my Android phone, the devicePixelRatio is 2.609... and it screws up - so
 it's really a case of this being a symptom of #29563

 ---

 At the end of the day, even once ESR78 is used (or you flip the pref
 early: there's nothing to say you can't do that now), I would still keep
 the patch: because domrect can still measure it

 Keep the test, close this, and re-purpose #29563 to deal with anomalies
 (getting it always 19.2 across the board would neutralize domrect in
 lineheight)?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30832#comment:8>
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