[tor-bugs] #19276 [Applications/Tor Browser]: Scrolling is slow and CPU intensive

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#19276: Scrolling is slow and CPU intensive
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 Reporter:  cypherpunks                          |          Owner:  tbb-
     Type:  defect                               |  team
 Priority:  Medium                               |         Status:
Component:  Applications/Tor Browser             |  needs_information
 Severity:  Normal                               |      Milestone:
 Keywords:  tbb-6.0-issues, tbb-usability, tbb-  |        Version:
  performance                                    |     Resolution:
Parent ID:                                       |  Actual Points:
 Reviewer:                                       |         Points:
                                                 |        Sponsor:
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Comment (by yawning):

 Replying to [comment:4 cypherpunks]:
 > Turns out issue is solved by setting `gfx.xrender.enabled` to `false`.
 Because I'm unfamiliar with the Firefox code base, i don't know what the
 preference does, what its impact is, and whether it's worth setting in TB.
 Hopefully someone else can figure this out.

 The behavior will end up being system/driver specific, since XRender
 performance depends on the driver.  That said, upstream changed the
 pref(s) fairly recently,
 https://bugzilla.mozilla.org/show_bug.cgi?id=1180942 and
 https://hg.mozilla.org/mozilla-central/rev/432ef38dab95), and has written
 off performance related regressions on systems where XRender compositing
 outperforms Cairo
 (https://bugzilla.mozilla.org/show_bug.cgi?id=1241832#c6).

 So in the mean time, the question is, do we care about systems that have
 drivers/hardware that supports XRender, but doesn't have hardware OpenGL?
 Or do we care about systems that do have hardware accelerated OpenGL more?
 The latter should be the majority...

 As a side note, the windows upstream bug is
 https://bugzilla.mozilla.org/show_bug.cgi?id=894128 (And it's totally
 orthogonal to the Linux rendering backend selection).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19276#comment:8>
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