1432433 - screen tearing when scrolling with webrender

Status: RESOLVED INVALID

(Core :: Graphics: WebRender, defect, P2)

Description

[lilydjwg]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
Build ID: 20180122220231

Steps to reproduce:

Enable WebRender by setting gfx.webrender.all to true.
Find a long page and scroll up and down.

Arch Linux
Mesa DRI Intel(R) HD Graphics 620 (Kaby Lake GT2) 
Mesa 17.3.2

I don't see this with WebRender disabled.


Actual results:

While scrolling, there is a tearing line on the upper left part, shape from left to right: horizontal, then slope down some distance, then horizontal again. The sloping part is most visible.

It's a bit like there is a piece glass causing refraction.

Comment 1

[Darkspirit]

Thank you! Could you try to make a screencast of it, please? Did you already saw it in the past or is this new?

Comment 2

[lilydjwg]

Attachment: screencast

I'm attaching a screencast. I notice it today, but I have enabled WebRender only a few days ago, so it may happen for me all the time, or just today. I'll try mozregression when I have time.

Comment 3

[lilydjwg]

BTW, its shape is different now (only a longer sloping line, no horizontal parts any more), but this is a different machine (and maybe it's different for different webpages?).

Comment 4

[Milan Sreckovic [:milan] (needinfo for best results)]

And this doesn't happen without WebRender?

Comment 5

[lilydjwg]

(In reply to Milan Sreckovic [:milan] from comment #4)
> And this doesn't happen without WebRender?

I stare while scrolling for some time, and at least I can't see this clearly without WebRender: it may happen very slightly, or not happen at all.

I've tried mozregression, at least 2018-01-13 is affected.

Comment 6

[lilydjwg]

I've seen this in a YouTube video without scrolling, for only about three seconds, regardless fullscreen or not. It doesn't happen without WebRender.

The video is at: https://youtu.be/9yZ_6SZtwmg?t=7m51s.

Comment 7

[lilydjwg]

Well, the same happens to mpv for me too....

Comment 8

[Darkspirit]

(In reply to lilydjwg from comment #7)
> Well, the same happens to mpv for me too....

Your Linux screencast is fine, so it's rather something between your graphics card and your screen.
Viewing movies with mpv or VLC was a pain for me in the past because I had not enabled vsync.

Maybe this helps you:
KDE: https://forum.manjaro.org/uploads/default/original/2X/3/3f0640ced95dac62be30b1e0cdaa3cf93e612a45.png (vsync)
https://askubuntu.com/questions/77740/how-can-turn-on-vsync-in-gnome-shell
https://wiki.archlinux.org/index.php/intel_graphics

https://github.com/mpv-player/mpv/wiki/FAQ#X11Intel
> Intel tears out of the box. Intel users on Linux are going to have a pretty bad time.

At the moment it looks like not being a Firefox bug.