evangelos@ Thanks for the issue.

As per the original comment, assigning the issue to chaopeng@, as this issue was caused by the above given CL.
chaopeng@ : Request you to check and help in further triaging.

Adding 'ReleaseBlock-Stable' as this is a recent regression. Please feel free to remove if it is not applicable.

Thanks..

Please check if your touchpad driver is libinput or synaptics. libinput should be smooth enough for touchpad. synaptics is out of date driver.

Also please let me know your laptop model.

libinput is expecting to send smooth delta to application. We also tested it is true on Thinkpad X1 and XPS 15. So we disable the smooth scroll animation on libinput otherwise it will feel jumpy on model have good driver. If your model is no smooth maybe you should report to libinput.

>  In addition, that bounding box usually suffers from a low resolution, causing jumpy movement during two-finger scrolling. libinput does not provide two-finger scrolling on those touchpads.
https://wayland.freedesktop.org/libinput/doc/latest/scrolling.html 

I normally use the synaptics driver but it also happens with libinput. Laptop is a HP 250 G3 (several years old at this point).

I've asked the person who originally noticed this to maybe chime in here. [1]

[1] https://www.reddit.com/r/archlinux/comments/91zli6/chromium_2fingerscrolling_broken_after_upgrade/

Reporter, could you provide more details here. Could you attach a video from what you see with libinput driver? I assume you don't have any other extensions or anything that could interfere with the process. Right? Do you see the same jankiness anywhere in any other app with that? Do you happen to have access to other devices? Do you see the same behavior there or is it only reproducible on HP 8570w SynPS/2?

We don't have this very same laptop model here. Can someone from QA does a test if they have access to this?

I remove the releaseblock at this point since the issue doesn't seem to be at that level.

(I have an HP 250 G3; geekzero...@ has an HP 8570w. The following screen recording is from my HP 250 G3.)

Attached is an event capture of slowly scrolling down and up. You might be able to use 'libinput replay' with it to simulate my touchpad's behavior.

I'm also including a screencast replaying the above event log, first on Chromium 67 and then on Chromium 68. You can clearly see that Chromium 68 behaves as if the #smooth-scrolling flag has been disabled.

It might not be an issue with the availability (or not) of high precision input from libinput, but perhaps that the smooth scrolling animation is not being applied (also called "scroll interpolation" in another issue).

I did a build of Chromium 68.0.3440.75 with [1] reverted and the scrolling animation worked again.

[1] https://chromium-review.googlesource.com/988748

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OK lets try to add back the scroll animation on Linux.

As per comment #6, tested this issue on Ubuntu 17.10 HP Elitebook on the reported version 68.0.3440.75 and the latest Dev 69.0.3497.12 and unable to reproduce the issue.
Able to scroll a page using two fingers on the touchpad and no issues were observed.
Attached are the System details and chrome://gpu details.

Removing 'Needs-Bisect' label as this issue is not reproducible at TE end. Please feel free to add it back if any information is required.

Thanks..

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I've been suffering from this exact issue since upgrading to Chrome 68, just like the original poster, and it never occured to me that it may be a touchpad issue.


After finding this bug report I tested with an external mouse and sure enough it's smooth with the mousewheel, but when scrolling with the touchpad it judders as if smooth scrolling is disabled. 

I was using synaptics, but I tested with libinput with no improvement on both Ubuntu 16.04 LTS and Gentoo stable. Enabling the 'smooth scrolling' flag offers no improvement.

Worked fine up until Chrome 68. 
 

Hardware: Thinkpad T410
Tested OS's: Gentoo Stable (libinput/synaptics) and Ubuntu 16.04 LTS (synaptics)