1269068 - [APZ] Perma-checkerboarding when page-scrolling with wheel during loading

Status: VERIFIED FIXED

(Core :: Panning and Zooming, defect)

Description

[arni2033]

>>>   My Info:   Win7_64, Nightly 49, 32bit, ID 20160429030215
STR:
0. Set mouse option "when I rotate mouse wheel" in your OS to "scroll by 1 page"
1. Open https://hi-tech.mail.ru/news/rissian-brest-300-nuclear-reactor/
2. Press PageDown to scroll the page down, then press Ctrl+Shift+R to reload
3. The same instant you see scrollbar moving, rotate mouse wheel down once

AR:  When web page finishes loading, it's still partially white (I can provide another screencast).
ER:  Web page should be displayed in a normal way.

Note:  I encountered this issue many times, and now I finally decided to file it.

This is regression from bug 1247677. Regression range (seems strange, thus NI):
> https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=9bce2f3c14e8920051de0c6f71a1e6a728949cba&tochange=558b65cbe70daed21cf648650cf29658a5b13855

Comment 1

[arni2033]

Attachment: screencast 1 - [APZ] Part of the page stays partially white.webm

Comment 2

[Kartikaya Gupta (email:[e-mail])]

I can reproduce this. I'm not entirely sure why the regression range points to bug 1247677, but it seems plausible since it added support for some mousewheel page-scrolling prefs. I can look into this bug.

Comment 3

[Kartikaya Gupta (email:[e-mail])]

Attachment: MozReview Request: Bug 1269068 - Zero out the axis velocity once the wheel scroll animation is terminating. r?botond

Review commit: https://reviewboard.mozilla.org/r/50053/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/50053/

Comment 4

[Botond Ballo [:botond]]

Comment on attachment 8747891 [details]
MozReview Request: Bug 1269068 - Zero out the axis velocity once the wheel scroll animation is terminating. r?botond

https://reviewboard.mozilla.org/r/50053/#review46819

Comment 5

[Botond Ballo [:botond]]

It might be nice to have the connection between not zeroing out the velocity, and perma-checkerboarding, explained in a comment on this bug.

Comment 6

[Kartikaya Gupta (email:[e-mail])]

What I was seeing is that the velocity gets left at non-zero, and the velocity bias code in displayport prediction was shifting the displayport away from what the user was seeing. I presume it happens with line-scrolling as well, but page scrolling makes it more noticeable because of the higher velocities involved. Zeroing out the velocity at the end of the animation makes sure the displayport shifts back to center, and makes sense given that the animation is over.

Comment 7

[Kartikaya Gupta (email:[e-mail])]

https://hg.mozilla.org/integration/mozilla-inbound/rev/909af7c19ebb

Comment 8

[Botond Ballo [:botond]]

(In reply to Kartikaya Gupta (email:[e-mail]) from comment #6)

Thanks!

Comment 9

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/909af7c19ebb

Comment 10

[arni2033]

Fixed on:   Win7_64, Nightly 49, 32bit, ID 20160504043118

Comment 11

[Kartikaya Gupta (email:[e-mail])]

Comment on attachment 8747891 [details]
MozReview Request: Bug 1269068 - Zero out the axis velocity once the wheel scroll animation is terminating. r?botond

Approval Request Comment
[Feature/regressing bug #]: bug 1247677
[User impact if declined]: in some cases the user can end up with checkerboarding on the screen which doesn't go away until the user scrolls or does something to trigger a repaint
[Describe test coverage new/current, TreeHerder]: tested locally
[Risks and why]: very low risk, small patch
[String/UUID change made/needed]: none

Comment 12

[Liz Henry (:lizzard) (relman/hg->git project)]

Comment on attachment 8747891 [details]
MozReview Request: Bug 1269068 - Zero out the axis velocity once the wheel scroll animation is terminating. r?botond

More APZ polish for aurora, verified on nightly already.

Comment 13

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/releases/mozilla-aurora/rev/0b5925bf7d52