[tor-bugs] #32253 [Applications/Tor Browser]: Zooming and letterboxing

[Tor Bug Tracker & Wiki]

#32253: Zooming and letterboxing
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 Reporter:  cypherpunks                    |          Owner:  tbb-team
     Type:  defect                         |         Status:  new
 Priority:  Medium                         |      Milestone:
Component:  Applications/Tor Browser       |        Version:
 Severity:  Normal                         |     Resolution:
 Keywords:  tbb-fingerprinting-resolution  |  Actual Points:
Parent ID:                                 |         Points:
 Reviewer:                                 |        Sponsor:
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Comment (by cypherpunks):

 Replying to [comment:7 Thorin]:
 > What have you achieved by tying zoom to letterboxing? Have I missed
 something?
 I had something like this in mind:

  - user A: 1000x700 + 150% zoom -> 667x467 + letterboxing -> 600x400
  - user B: 1000x600 + 150% zoom -> 667x400 + letterboxing -> 600x400

 If I understand correctly your point is that the page will first see the
 original size, then see the decreased size, so you're not hiding anything.
 If we assume the site continuously tracks and snitches your window size
 across your whole visit then it really is quite pointless.

 However, even if we're dealing with that kind of site, it's not
 necessarily the case that it learns about your original window size:

  1. open about:tor or visit whatever site
  2. zoom in
  3. go to some other site in the same tab

 In this case the last site has never seen your original size. However
 without letterboxing it can make some assumptions, like in the example
 above. For one thing it can immediately tell you're using zoom and do not
 have a small screen (and vice-versa if you have a small screen).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32253#comment:8>
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