1272408 - Sometimes the content is moved up/down when scrolling from beginning to the end of the page

Status: RESOLVED DUPLICATE of bug 1012752

(Core :: Panning and Zooming, defect)

Description

[Petruta Horea [:phorea], Desktop QA]

[Affected versions]:
- Nightly 49.0a1 2016-05-12
- Aurora 48.0a2 2016-05-12

[Affected platforms]:
- Win 10 64-bit
- Ubuntu 14.04 64-bit
- Mac OS X 10.9.5

[Steps to reproduce]:
1. Open https://en.wikipedia.org/wiki/Facebook
2. Navigate to the bottom of the page using "End" or "Ctrl/Cmd + Down" keys
3. Navigate to the top of the page "Home" or "Ctrl/Cmd + Up" keys
4. Repeat the above steps several times

[Expected result]:
- The scrolling is smooth, the content is properly displayed

[Actual result]:
- When reaching the top/end of the page, some lines are jumping up/down. I could only reproduced this intermittently.

[Regression range]:
- Seems to be regressed by bug 1253860

DEBUG : Found commit message:
Bug 1253860 - Don't update the scrollbar unless we're actually painting. r=mstange

Comment 1

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

(In reply to Petruta Rasa [QA] [:petruta] from comment #0)
> [Actual result]:
> - When reaching the top/end of the page, some lines are jumping up/down. I
> could only reproduced this intermittently.

It's not clear to me what exactly you mean. I tried reproducing and saw that in some cases text looked like it was getting shifted by a pixel vertically - is that what you mean? I'll try to grab a video.

Comment 2

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

Attachment: Video

The shift I'm talking about happens after I scroll back up to the top of the page, in this video.

Comment 3

[Petruta Horea [:phorea], Desktop QA]

That's what I'm seeing too. It reproduces on the bottom of the page too.

I also saw it while scrolling top - bottom - top on https://facebook.com.

Comment 4

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

Markus, is this some sort of subpixel alignment issue?

Comment 5

[Markus Stange [:mstange]]

Yeah, the one that Jeff keeps bugging me about (and he's right to do so).

Comment 6

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

Fixed in bug 1267885.