Debian Testing, KDE, Macbook Pro

This problem occurs only rarely and - I assume - only with autoscrolling.
Screencast: Jump to 20s.

pretty messed up but probably something we can ignore until linux is higher priority or more people run into it

Qualified WebRender on 67 affected.

https://www.reddit.com/r/firefox/comments/bs8894/issue_browsing_reddit_with_webrender/

Could this somehow be a duplicate of bug 1528180?

Do you still see this in 69?

20190705161030, GTX1060, driver 430.86

And only with WebRender?

Yes, it seems so. I was not able to reproduce it with Basic or Direct3D 11 (Advanced Layers).
Also, it only happens at certain places and is reproducible when scrolling back to the same position.

mozregression --good 2019-01-09 --bad 2019-01-11 --pref gfx.webrender.all:true -a https://www.reddit.com/r/firefox/
19:46.42 INFO: Last good revision: fbe6548db11ded24b5221180719ce66e785dc3c6
19:46.42 INFO: First bad revision: ad851d4345c08f7e0e5d5578652004194a6e667f
19:46.42 INFO: Pushlog:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=fbe6548db11ded24b5221180719ce66e785dc3c6&tochange=ad851d4345c08f7e0e5d5578652004194a6e667f

Same as last "good" (scrolling sometimes takes a jump):
mozregression --launch 2019-07-07 --pref gfx.webrender.all:true layout.css.scroll-anchoring.enabled:false -a https://www.reddit.com/r/firefox/

Same as first bad:
mozregression --launch 2019-07-07 --pref gfx.webrender.all:true -a https://www.reddit.com/r/firefox/

(In reply to Jan Andre Ikenmeyer [:darkspirit] from comment #11)

Created attachment 9076413 [details]
2019-07-08 03-23-14.mp4

The scroll jump as seen on the left side of the screencast is also reproducible with

• today's Nightly and gfx.webrender.force-disabled;true layout.css.scroll-anchoring.enabled;false
• mozregression --launch 2017-03-15 --pref browser.startup.homepage:'https://www.reddit.com/r/firefox/'

Conclusion: Scroll anchoring made an existing non-WR bug look worse with WebRender, but apparently fixed it for non-WR.

Bug 1528180 should probably fix it. If somebody can confirm once it's on nightly it'd be great.

It happens the same to me. In reddit too. I made a video: https://youtu.be/dwffYcQPiQI

It happens since I updated to FF68. config:support says I'm using webrender on windows 10.

Still broken, I think.

Build ID: 20190713095401
https://hg.mozilla.org/mozilla-central/rev/3e793ca066f227fcc3c25e31925d3729ca8593f8

Ah, I see, I think that's a different snapping issue, presumably across tiles. My patch should fix problems where the whole scrolling element jitters, but that screencast is different.

Thanks for checking anyhow! :)

So comment 14 and comment 15 look different. Comment 14 shows shaking the whole body, that may have been fixed by bug 1528180. Comment 15 however only shakes in some very specific spots.

Perhaps it makes sense to just a file a new bug for comment 15 so that the different things are clearer here.

Win10/GTX1060
Either there are multiple bugs on Reddit now, or this bug has changed. It looks related to bug 1565473 comment 3.

Focus on "Can't download Adblock Plus" at the top and on "Can I open Chrome only sites?" at the bottom

Picture caching is tortured. Wait until the end.
You see "Posted by u/blablabla 11 hours ago" is jumping.

This may be fixed by https://bugzilla.mozilla.org/show_bug.cgi?id=1566712.

(In reply to felpaman from comment #14)

It happens the same to me. In reddit too. I made a video: https://youtu.be/dwffYcQPiQI

It happens since I updated to FF68. config:support says I'm using webrender on windows 10.

It keeps happening on 68.0.1

Nical - could you help debug this? Seems like it isn't fixed yet

Win10 1903, GTX1060, Nightly 20190722093634 (rev db8f3ee41bdf525db2d0e5816d26ee654ab6ec7e)

It seems bug 1566712 has fixed broken text and shaking posts.
Left over is a shaking sidebar at 150% zoom: Most often only "ADVERTISEMENT" is shaking a certain scroll positions. This is a rare footage of STR with some more shaking text (sidebar footer).

I think that this is an old layout bug which hasn't been figured out yet. See bug 1418256 and bug 1419409 for example. Under certain conditions it appears that layout is constantly invalidating and oscillating. It isn't specific to WebRender.

Still reproducible with gfx.webrender.picture-caching;false.
As you can see, Devtools indicates everything - not just the sidebar - is jittering.

With Direct3D 11 (Advanced Layers) the remaining bug is not visible on first sight, but reproducible with DevTools!

Happy to take a patch for 70 or beyond.
Since we are getting close to the end of the 69 beta cycle and this is set to P3, I'm marking it fix-optional for 69 and 70 to remove it from weekly triage.

166 net votes on reddit around this bug - https://www.reddit.com/r/firefox/comments/cx7sfb/reddit_has_jumping_pixels/ - this is starting to gather attention (makes sense, given the traffic on reddit).

Just an FYI.

If the regression range here is accurate (scroll anchoring), perhaps Reddit readers would find it useful if the workaround of setting layout.css.scroll-anchoring.enabled=false was mentioned in the thread?

Not happening anymore since v69.

Showing up again now? https://www.reddit.com/r/firefox/comments/ecea1l/jitter_and_shaking_web_elements_on_redditcom/

:darkspirit — Are you able to reproduce this in more recent versions?

https://www.reddit.com/r/firefox/comments/ecea1l/jitter_and_shaking_web_elements_on_redditcom/fbb1unh/ says this happens in Chrome, too, FWIW...

A few more notes:
(1) This comment says it happens in Edge as well (not surprising given the other comment about Chrome from comment 35)

(2) Several comments indicate that multiple users (including the original poster) can't reproduce after disabling WebRender, e.g. this one

(3) Also, no updates on that thread for the past ~year (after that "disable WebRender" workaround was discovered).

So: this should be reclassified as WebRender (but also, perhaps not really a Firefox bug, given that it reportedly repro's in Chrome/Edge?)

The severity field for this bug is relatively low, S3. However, the bug has 5 See Also bugs.
:gw, could you consider increasing the bug severity?

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