[tor-bugs] #20941 [Applications/Tor Browser]: Tor browser will resize it self after the dock is enabled and the browser is dragged to a new location

[Tor Bug Tracker & Wiki]

#20941: Tor browser will resize it self after the dock is enabled and the browser
is dragged to a new location
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 Reporter:  Dbryrtfbcbhgf                        |          Owner:
                                                 |  arthuredelstein
     Type:  defect                               |         Status:
                                                 |  assigned
 Priority:  High                                 |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Major                                |     Resolution:
 Keywords:  tbb-fingerprinting-resolution,       |  Actual Points:
  TorBrowserTeam201612                           |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by arthuredelstein):

 I think this behavior is a result of our #14429 patch (which is only
 active in the alpha). When you disable dock autohiding, macOS apparently
 attempts to resize the window so that it no longer overlaps with the dock.
 Then the 14429 patch responds by resizing again to ensure that the content
 window has rounded dimensions (a multiple of 200 x 100).

 I think this behavior is essentially decreasing the fingerprintability, as
 intended. However, it would be good to check. Dbryrtfbcbhgf, if you could
 run this test again, could you please browse to
 https://jsfiddle.net/rv37t3dz/ and check that the window dimensions are
 correctly rounded after the resizing event?

 An additional wrinkle is that the horizontal size seems to be shrinking. I
 think this is probably the result of macOS shrinking the width by a small
 amount (maybe 1 pixel) and then 14429 responded by shrinking to the next
 lower rounded dimension. We could consider allowing a "rounding up" from
 99 pixels to 100 for situations like this.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20941#comment:5>
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