1556685 - layer-pixel alignment causes undesired scroll position via some kind of CSSOM-View APIs such as scrollTop

Status: NEW

(Core :: Layout: Scrolling and Overflow, defect, P3)

Description

[Hiroyuki Ikezoe (:hiro)]

See bug 1554024 comment 7 for example, and bug 1554022 comment 5 is also an interesting case.

I will attach a mochitest to replicate this issue tomorrow.

Comment 1

[Hiroyuki Ikezoe (:hiro)]

Hmm, the mochitest I wrote doesn't fail as expected. So, I provide a way to see the issue, that is;

./mach wpt --setpref "layout.css.devPixelsPerPx=1.61" testing/web-platform/tests/css/cssom-view/scroll-behavior-smooth.html

You might need to change the devPixelsPerPx value on your environment.

Comment 2

[Hiroyuki Ikezoe (:hiro)]

CCing Karl since I am bit worried that this bug causes webcompat issues on GeckoView applications. If 1-pixel (or maybe worse?) differences appear on GeckoView but not on Fennec, it's this bug.