Screencast: Left=last good, right=first bad. bad = There is a flickering line on the left side of a growing image. (The image was already jiggling before.) mozregression --good 2018-06-01 --bad 2018-10-22 --pref gfx.webrender.all:true -a https://www.postbank.de/privatkunden/girokonten.html > 12:34.36 INFO: Last good revision: 10b2b242b9bdf9daa261c66f269f622d51cb6a12 > 12:34.36 INFO: First bad revision: f5063652dacb667a451348c37c983cf962eaf324 > 12:34.36 INFO: Pushlog: > https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=10b2b242b9bdf9daa261c66f269f622d51cb6a12&tochange=f5063652dacb667a451348c37c983cf962eaf324 > f5063652dacb Jeff Muizelaar — Bug 1490640. Mark intermittent tests as random. > 969f3b484bbb Jeff Muizelaar — Bug 1490640. Update webrender to 70edb5f8a75ea1e1440ba7984cc42df9eb05ae69 Regression range: https://github.com/servo/webrender/compare/02f14d0f333ef125d1abff7b1146039a0ba75f43...70edb5f8a75ea1e1440ba7984cc42df9eb05ae69
This doesn't just happen when it loads. After it finishes, I can find zoom levels where it contains a bad line on either the left and/or the right side.
This is a reduced test case distilled from the original page where the problem was first observed.
The transform: translate3d(0px, 0px, 0px) seems to make us create an extra stacking context. This splits off the translate (since the content starts a few pixels down from the top edge and over from the left edge) and the scaling for the background image. However the clips are slightly different and we end up rendering an extra row/column of green pixels as a result. I was thinking this was because of the image snapping issue in bug 1453747 but I think the clip in question was not generated/related to the image itself (since it lives between the translate and scaling stacking contexts, and is applied to the latter in its clip/scroll info), so something else may have gone wrong.
Attachment #9030754 - Attachment description: Bug 1501195 - Part 1. Add a reftest demostrating the image snapping problem. → Bug 1501195 - Fix snapping issues caused by translation only transforms.
Pushed by firstname.lastname@example.org: https://hg.mozilla.org/integration/mozilla-inbound/rev/524a6613a2ce Fix snapping issues caused by translation only transforms. r=jrmuizel
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