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

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#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 Thorin):

 Replying to [comment:8 cypherpunks]:
 > In this case the last site has never seen your original size

 It doesn't matter which measurements it sees (at 100% or 133%), because
 math can be used to calculate the other, as long as zoom is known

 current
 - site A at 100%: 1000x700
 - zoom A to 133%: `752x526` <-- weird, but hey you zoomed
 - site B (same tab at 150%)
 - site B uses math and calculates 100% = 752 x 1.33 by 526 x 1.33 =
 1000x700

 proposed
 - site A at 100%: 1000x700
 - zoom A to 133%: 752x526 -> 700x500
 - site B (same tab at 133%)
 - site B uses math and calculates 100% = 700 x 1.33 by 500 x 1.33 =
 `933x665` <-- weird because you tried to solve a problem that does not
 exist

 You can't "standardize" both ends unless you can completely spoof zoom,
 which is problematic and probably undo-able. And there are so many other
 ways to get measurements, e.g elements, and monitor them, e.g. observer
 APIs. DPI complicates this as well.

 PS: I used 133% as an example so we got back crazy non-uniform numbers:
 some zoom levels are multipliers that can or do still round things

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32253#comment:9>
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