1567977 - Scrolling sometimes reacts late on touch input on Android

Status: NEW

(Core :: Panning and Zooming, defect, P3)

Description

[Chris Peterson [:cpeterson]]

Steps to reproduce

1. Open https://github.com/mozilla-mobile/fenix/issues
2. Switch to desktop version
3. Scroll up and down the page at intervals of a few seconds

Expected behavior

Scrolling happens immediately like in Fennec 68

Actual behavior

Page scrolls with noticeable delay, as shown in this video capture:
https://www.youtube.com/watch?v=Pf5xt_fGQHE

This bug was originally reported in the Fenix issue tracker:
https://github.com/mozilla-mobile/fenix/issues/3546

Comment 1

[Chris Peterson [:cpeterson]]

This looks like an APZ or gfx issue on Android.

Comment 2

[Botond Ballo [:botond]]

I'm not able to reproduce this in Fenix 1.1.0.

Comment 3

[wasseranomalie]

Hi, I'm the original reporter of this bug. I've just downloaded the latest Nightly of Firefox Preview and on my phone this issue still exists. Here are my specs:

Phone: Nexus 5X
Android: 8.1
Firefox Preview: Nightly 190726 06:03 (Build #12070610)

If I can help you with further data, I'll happily provide them.

Comment 4

[Botond Ballo [:botond]]

I tried Nightly as well, still can't repro.

I'm testing on a Moto G5 running Android 7.0. I wonder if the issue is specific to the device or Android version.

Comment 5

[Botond Ballo [:botond]]

Chris, are you able to reproduce this with any device that's available to you?

Comment 6

[Botond Ballo [:botond]]

Marking as P3 to get this off the triage radar, but this basically isn't actionable until we can reproduce it.

Comment 7

[Chris Peterson [:cpeterson]]

(In reply to Botond Ballo [:botond] from comment #5)

Chris, are you able to reproduce this with any device that's available to you?

Sorry for the late response. I am not able to reproduce an obvious scrolling problem with the STR from comment 0 (on my Moto G5 running Android 8.1). The original Fenix bug reporter was using a Nexus 5X running Android 8.1. I'll ask them on GitHub if they can still reproduce the problem.

Comment 8

[Chris Peterson [:cpeterson]]

The original Fenix bug reporter says he can still reproduce the scrolling problem in Fenix (GV 69 Beta) and R-B (GV 70 Nightly). I can't reproduce on my Moto G5, though I can't really see the scrolling problem in the original YouTube screen capture.

The only step to take is to request the desktop version of the website. It seems to become more frequent when zooming out completely to see the whole page width.
Another site I found was the desktop-version of YouTube (and if not done automatically zoomed out completely). There this scrolling problem appears on every try on my device, so maybe you have more luck there to reproduce this issue.

https://github.com/mozilla-mobile/fenix/issues/3546#issuecomment-525416143

Comment 9

[Chris Peterson [:cpeterson]]

The original Fenix bug reporter says he can still reproduce the laggy scroll start in Fenix but not Fennec:

On Firefox for Android 68 this issue only happens very rarely and when it happens the delay is very short. Scrolling is far worse on Firefox Preview with a delay of up to one second after touching the display (vs. maybe <0.2 seconds on Firefox for Android 68).
I've made another video showing this issue: https://youtu.be/UcqER9irdOo (the delay does not become shorter after all thumbnails have been loaded)
You can also see at the end of the video that after scrolling has started, there is no delay when changing direction anymore so there is just a huge delay when you want to start scrolling.

Comment 10

[Botond Ballo [:botond]]

My suggestion for a way forward here is to:

• Work with the original bug reporter to collect a performance profile while reproducing the delay.
• See if we can diagnose the cause of the delay based on the performance profile.

It would be great to have some help from the performance team with the above tasks. Adding the [qf] whiteboard tag to get the bug into their triage queue.