STR: 1- Open up a messaging thread long enough to scroll (may need to span more than a day, not sure) 2- Scroll up and down Expected: The view scrolls normally. Actual: The fixed-position date bar at the top jitters about during scrolling This is almost certainly fallout from multi-layer apzc, so I'm going to block that, but adding regressionwindow-wanted just in case.
Created attachment 8485748 [details] Layers dump I'm able to reproduce this on a flame running latest master. I used |make reference workload-medium| and opened up one of the SMS threads that gets populated. It looks like the fixed-position layer isn't getting aligned in AsyncCompositionManager and so it only moves on repaints. Layers dump attached.
This is probably happening because the layer with isStickyPosition set on it is the same layer that has the scrollable metrics. So yeah, almost certainly a regression from multi-layer-apz, but we should be able to fix it in AsyncCompositionManager, I think.
Created attachment 8485775 [details] [diff] [review] Patch This fixes it. If I don't take out the clip rect bit then the date row partially disappears while scrolling. I don't understand why the clip rect is shifted at all, it seems to me like if we're not adjusting the clip rect for async scroll then we shouldn't be adjusting it for fixed layers either.
Comment on attachment 8485775 [details] [diff] [review] Patch Actually after thinking about it some more I think the patch might be wrong. I'll see if I can write some tests to exercise this.
Created attachment 8486363 [details] [diff] [review] Patch v2 Ok, this patch I think is correct. Try push with just the sticky-pos test showing that it fails: https://tbpl.mozilla.org/?tree=Try&rev=5461ecde83f8 Try push with the full patch showing that it passes: https://tbpl.mozilla.org/?tree=Try&rev=35895c90f1e0 The fixed-pos test would have failed on the previous version (I verified that locally, but didn't do a try run) of the patch but passes with this version.
Comment on attachment 8486363 [details] [diff] [review] Patch v2 Not that my opinion matters too much on this now, but this looks good to me :)
Comment on attachment 8486363 [details] [diff] [review] Patch v2 Approval Request Comment [Feature/regressing bug #]: bug 967844 [User impact if declined]: some pieces of content that are position:fixed or position:sticky jitter while scrolling [Describe test coverage new/current, TBPL]: added reftests, manual testing [Risks and why]: low risk, code is pretty well understood. only affects platforms with async scrolling (b2g and fennec) [String/UUID change made/needed]: none
This issue has been verified successfully on Flame2.1&2.2. Reproducing rate: 0/5 See attachment: Verify_Flame_FTE.png Flame2.1 build version: Gaia-Rev dbaf3e31c9ba9c3436e074381744f2971e15c7bf Gecko-Rev https://hg.mozilla.org/releases/mozilla-b2g34_v2_1/rev/ebce587d2194 Build-ID 20141203001205 Version 34.0 Flame2.2 build version: Gaia-Rev 725685831f5336cf007e36d9a812aad689604695 Gecko-Rev https://hg.mozilla.org/mozilla-central/rev/2c9781c3e9b5 Build-ID 20141203040207 Version 37.0a1