[tor-bugs] #10095 [TorBrowserButton]: Setting screen resolution to a multiple of 200 x 100 is not working reliably with patch in #8478

[Tor Bug Tracker & Wiki]

#10095: Setting screen resolution to a multiple of 200 x 100 is not working
reliably with patch in #8478
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     Reporter:  gk                |      Owner:  mikeperry
         Type:  defect            |     Status:  new
     Priority:  critical          |  Milestone:
    Component:  TorBrowserButton  |    Version:
   Resolution:                    |   Keywords:  tbb-fingerprinting
Actual Points:                    |  Parent ID:
       Points:                    |
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Comment (by cypherpunks):

 I've converted the bits/denominators into absolute numbers and updated the
 table and attachment above. It's pretty bad:

 '''Only 45% of requests were correctly rounded''' to 100 px. This of
 course hurts even the people for which rounding ''does'' work by shrinking
 the anonymity set.

 Looks like at the time the first window is resized, not all extensions'
 toolbar buttons have necessarily been drawn yet, varying from system to
 system. For example, 9 px missing height (24% of requests) happens like
 this I think:

 1. TB starts up and ''for some users'' (including me) HTTPS Everywhere
 presumably hasn't fully drawn its button yet.

 2. TB Button gets the new window notification, does the relative resize,
 and all is good until ...

 3. ... HTTPSE fully draws its button. With "Use Small Icons" disabled (=
 the default), the HTTPSE button + padding + margin + border is 9 px larger
 vertically than the other toolbar buttons. With "Use Small Icons" enabled,
 the the HTTPSE button is 1 px larger vertically.

 4. So either 9 or 1 px is stolen vertically from the innerHeight, and e.g.
 1000x600 becomes 1000x591 or 1000x599.

 5. If you open a new window manually or through New Identity, HTTPSE is
 now fully initialized or something and TB Button will do a good ''stable''
 resize.

 Maybe just close the damned first window immediately and open a new one?
 And could someone ask upstream if there's some kind of "all extensions
 have initialized" notification?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/10095#comment:8>
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