1344339 - [Regression] Scrollbar jumps when I drag it with mouse sometimes

Status: NEW

(Core :: Layout, defect, P3)

Description

[684sigma]

I have a problem with Firefox Beta 52. It doesn't happen in Firefox 51 (checked twice)
Sometimes jumps when I drag it with mouse.
It happens unpredictably, however, I noticed one specific scenario when it happens

1. Open about:preferences#advanced
2. Slowly drag scrollbar in "Offline web content and user data" section from top to bottom and back to the top

Result: scrollbar jumps below mouse pointer a bit to the top and bottom during the drag gesture
Expected: scrollbar doesn't jump

Here're some sites that add "offline web content and user data" instances:

http://html5demos.com/offlineapp
http://appcache-demo.s3-website-us-east-1.amazonaws.com/with-network/
http://www.spritecow.com/
http://everytimezone.com/
http://web.telegram.org/
http://lagged.com/play/501/ (you need to wait until the ad finishes)

Comment 1

[684sigma]

This is not specific to preferences, it also happens in profile manager, more visible if there are 7-10 profiles in the list.
I'm adding "Need more information", because component is not "Preferences". I don't know whether wrong component is better than "Untriaged"

Comment 2

[Loic]

Cant repro it.

Comment 3

[684sigma]

Attachment: bug 1344339 very detailed, by reporter.webm

(In reply to Loic from comment #2)
> Cant repro it.

What versions did you test, Firefox Release 51 and "Nightly (currently 54)" again, like in bug 1344342, Comment 3? Testing the bug on irrelevant versions without asking user anything doesn't look useful to me, this is my personal opinion (Just in case, my email is up there, send me any questions regarding bugs I uploaded)

Could you please send a video, recorded on the reported version? For example, recording of scrolling with the same speed as shown in attached video. Without that you can't distinguish 3 possibilities: (1) the bug was fixed, (2) you didn't do exactly what I reported, (3) the bug is specific to my machine.
By the way, if (3) is the case, then the bug is still valid, right? Then what do I do, report it again for somebody else to test it? Can you provide me with some logging to prove that it really happens?

Comment 4

[684sigma]

Also please answer to my comment bug 1344339, Comment 1. The bug also happens in profile manager, which is not "Preferences", so component is wrong. Or should I upload a new bug for the same jumping of scrollbar in profile manager? In fact, in bug 1344339, Comment 1 I only asked you about component, so if you weren't trying to reproduce it, please ignore bug 1344339, Comment 3.

Comment 5

[ovidiu boca[:Ovidiu]]

Hi 684sigma, 

Can you please type in the URL bar about:config and in the search "field apz.drag.enabled"(without commas) and please see the value, is that on false or true? I tested on Nightly 55.0a1 (2017-03-09) and I can reproduce it if the apz.drag.enabled pref is set to true. If I change it on false the issue is no longer reproducible. 
Please change the value (double click on it) and retest this issue. You can use Nightly, here is a link for download it:  https://nightly.mozilla.org/

Thanks

Comment 6

[684sigma]

(In reply to ovidiu boca[:Ovidiu] from comment #5)
> Hi 684sigma, 
> 
> Can you please type in the URL bar about:config and in the search "field
> apz.drag.enabled"(without commas) and please see the value, is that on false
> or true? I tested on Nightly 55.0a1 (2017-03-09) and I can reproduce it if
> the apz.drag.enabled pref is set to true. If I change it on false the issue
> is no longer reproducible. 
> Please change the value (double click on it) and retest this issue. You can
> use Nightly, here is a link for download it:  https://nightly.mozilla.org/
> 
> Thanks

I have "apz.drag.enabled" is set to "false". If I change it to "true", I see the same bug.
I doubt I have enough time to test this on Nightly, because I'was going to spend time to reporting remaining bugs. Set "needinfo" again if you think it's OK to keep it for several weeks.

Comment 7

[YF (Yang)]

I see the issue in Fx52.0 with "apz.drag.enabled" to false/true, on Win10.


Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=8f43d635de8d40cfc8f5aea938271b8cf26e2621&tochange=b30c5aed91fb9281d04b65a0ce55ecc0db1073fd

b30c5aed91fb	Kearwood Gilbert — Bug 1328053 - Correct thumb position when shift-click scrolling r=mats

Comment 8

[:kip (Kearwood Gilbert)]

I have reproduced on Win10 also.  I was additionally able to over-scroll the dialogue box.  FWIW, my display is UHD with 200% scaling.  I was able to over-scroll about a 100% additional amount.

I suspect that the "jumping" effect is specific to scroll bar thumbs that snap to each line in a selection box.  The regressing patch may have allowed the browser positioning of the thumb to take precedence over the OS-level snapping behavior except on these snap points.

If help is needed, I can dig in a bit deeper after I land Bug 1344216, expected in about a week.

Comment 9

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

Too late for a fix for 53, fix-optional for 54, minor carryover regression.

Comment 10

[MarjaE]

I have coordination issues, so I use scrolling software rather than the scrollbar, but I have encountered similar painful jumping. Mozilla's support site is affected:

https://support.mozilla.org/en-US/?fpa=1

Once the top section disappears, it jumps all the way to the middle of the "Firefox" and "Firefox for Android" boxes.

Comment 11

[Astley Chen (inactive)]

(In reply to :kip (Kearwood Gilbert) from comment #8)
> If help is needed, I can dig in a bit deeper after I land Bug 1344216,
> expected in about a week.

kip, not sure whether it's still reproducible on win10. Would you be able to keep looking into it?

Comment 12

[:kip (Kearwood Gilbert)]

(In reply to Astley Chen [:astley] from comment #11)
> (In reply to :kip (Kearwood Gilbert) from comment #8)
> > If help is needed, I can dig in a bit deeper after I land Bug 1344216,
> > expected in about a week.
> 
> kip, not sure whether it's still reproducible on win10. Would you be able to
> keep looking into it?

I am pretty swamped with the imminent release of WebVR in release FF55 and may take a while to look into this one.  I would be glad to assist, but suggest someone else continue in order to resolve it sooner.