Hi Emlio,
Thanks for your patience with these fixes and taking the time to outline
your concerns. Hope things are better now, and as always, if not just say
so. :)
Chris
On Thu, Feb 20, 2020 at 7:39 AM Emilio Cobos Álvarez
wrote:
> A quick status update here:
>
> I landed some heuristics to disable scroll anchoring in pathological
> cases in Firefox a long while ago. This stopped virtually all compat
> issues, though it's obviously not great.
>
> Chris and other Chromium folks have been doing work to fix Chromium
> issues that were causing these interop problems, and improving the
> scroll anchoring spec.
>
> So I'm going to try and peek up those spec changes in Firefox and then
> try to remove those heuristics on Nightly, and see how it goes.
>
> -- Emilio
>
> On 11/7/19 12:07 AM, Chris Harrelson wrote:
> > HI Emilio,
> >
> > I'll follow up on crbug.com/920289 <http://crbug.com/920289>. Let's
> > discuss there.
> >
> > On Tue, Oct 29, 2019 at 3:03 PM Emilio Cobos Álvarez > <mailto:emi...@mozilla.com>> wrote:
> >
> > Hi all,
> >
> >10/18/19 7:19 PM, Chris Harrelson wrote:
> > > Hi,
> > >
> > > Another quick update: Emilio, Navid, Nick, Stefan and I met today
> and
> > > discussed which issues are important to fix and why. We now have
> > a list of
> > > spec issues, and WPT tests to fix that are Chromium bugs, that
> should
> > > substantially improve interop. Nick and Stefan will take on the
> > work to fix
> > > them, with the review and feedback support of Emilio.
> >
> > So, today another scroll-anchoring bug crossed my radar, and this one
> > I'm not sure at all how to fix it, because there's no obvious answer
> > here as far as I can tell.
> >
> > My diagnosis (for one of the pages, the one I could repro and
> > reduce) is
> > in here[1], but basically my current explanation is that the page
> > should
> > be broken per spec, and that when it works it's hitting a bug in both
> > Chromium[2] which we have an equivalent of but are just not hitting
> > because in Firefox changing `overflow` does more/different layout
> work
> > than in Chrome.
> >
> > The test-case may as well work if we change our scroll event or timer
> > scheduling (see there), but that is obviously pretty flaky.
> >
> > I honestly don't have many better ideas for more fancy heursitics
> about
> > how to unbreak that kind of site. From the point of view of the
> > anchoring code, the page is just toggling height somewhere above the
> > anchor, which is the case where scroll anchoring _should_ work,
> usually.
> >
> > I can, of course (and may as a short-term band-aid, not sure yet) add
> > `overflow` to the magic list of properties like `position` that
> > suppress
> > scroll anchoring everywhere in the scroller, but that'd be just
> kicking
> > the can down the road and waiting for the next difference in layout
> > performance optimizations between Blink and Gecko to hit us.
> >
> > I think (about to go on PTO for the next of the week) I'll add
> > telemetry
> > for pages that have scroll event listeners, and see if disabling
> scroll
> > anchoring on a node when there are scroll event listeners attached
> > to it
> > is something reasonable (plus adding an explicit opt-in of course).
> >
> > I'm not terribly hopeful that the percentage of such documents is
> going
> > to be terribly big, to be honest, but providing an opt-in and doing
> > outreach may be a reasonable alternative.
> >
> > Another idea would be to restrict the number of consecutive scrolls
> > made
> > by scroll anchoring to a given number at most. That would made the
> > experience in such broken websites somewhat less annoying, but it'll
> > also show flickering until that happens, which would make the browser
> > still look broken :/.
> >
> > Thoughts / ideas I may not have thought of/be aware of?
> >
> > Thanks,
> >
> >-- Emilio
> >
> > [1]: https://bugzilla.mozilla.org/show_bug.cgi?id=1592094#c15
> > <https://bugzilla.mozilla.org/show_bug.cgi?id=1592094#c15>
> > [2]: https://bugs.chromium.org/p/chromium/issues/detail?id=920289
> > <https://bugs.chromium.org/p/chromium/issues/detail?id=920289>
> >
> > > Thanks all,
> > &
