1736757 - pinch zoomed on slack images and text jump around while scrolling

Status: RESOLVED DUPLICATE of bug 1735008

(Core :: Graphics: WebRender, defect)

Description

[Timothy Nikkel (:tnikkel)]

Attachment: Screen Recording 2021-10-19 at 10.14.35 PM.mov

Pinch zoom in on slack. Scroll around. The images and text jump around in a very un-appealing manner.

Comment 1

[Botond Ballo [:botond]]

One theory for what might be causing this is that perhaps WebRender is snapping scroll offset to integer coordinates pre-zoom, while Gecko code snaps them to integers post-zoom.

Comment 2

[Timothy Nikkel (:tnikkel)]

Attachment: jp.html

This is a testcase that reproduces lines of test jiggling up and down.

STR: pinch zoom in all the way. Scroll down enough so that we have to update the layout scrolloffset (scroll 10 screens worth). Then slowly scroll down. For me at least one line of text will jiggle for each screenful of test I scroll.

Comment 3

[Timothy Nikkel (:tnikkel)]

(In reply to Timothy Nikkel (:tnikkel) from comment #2)

Created attachment 9260944 [details]
jp.html

This is a testcase that reproduces lines of test jiggling up and down.

STR: pinch zoom in all the way. Scroll down enough so that we have to update the layout scrolloffset (scroll 10 screens worth). Then slowly scroll down. For me at least one line of text will jiggle for each screenful of test I scroll.

Using nightly 2021-01-01 (so I could try without webrender), I verified that I can see the issue with webrender, but with webrender disabled I do not see the issue.

Comment 4

[Hiroyuki Ikezoe (:hiro)]

I unexpectedly found the exact dup bug, bug 1735008. Marking this as a dup of that bug.