1230078 - Scrolling resets to initial position after scrolling for a bit (Android APZ)

Status: RESOLVED DUPLICATE of bug 1243547

(Firefox for Android Graveyard :: Toolbar, defect)

Description

[Gian-Carlo Pascutto [:gcp]]

Nexus 7 2013, Android 5.1.1, todays Nightly. All of the below are regressions in this Nightly.

I tested on this URL: http://www.pianoworld.com/forum/ubbthreads.php/topics/1215363/15.html

Issue observed:

After initiating scrolling, the page regularly snaps back to the original position, undoing all the scrolling that has been done.

STR: Just try to scroll and pan around on the linked page for a while.

Comment 1

[James Willcox (:snorp) ([e-mail]) (he/him)]

I'm having trouble reproducing this one. Do you get it more while the page is still loading or when it's complete?

Comment 2

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

Yeah I'm not seeing this either.

Comment 3

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

(If you see this on any other sites please provide URLs.)

Comment 4

[Gian-Carlo Pascutto [:gcp]]

I have trouble reproducing it with todays Nightly. 

Went back to yesterdays and got it again after scrolling back and forth a bit. Basically the scrolling motion has stopped, but you're suddenly (without transition) yanked to another point in the page.

I'll report back if I see it with a new Nightly again. This was obnoxiously bad when I complained about it yesterday, now I'm having a much harder time triggering it, so I'll see if I can narrow it down.

Comment 5

[Gian-Carlo Pascutto [:gcp]]

Reproduced on Nexus 9, Android 6.0.

https://youtu.be/Eg_17cszmJU

Happens at 16 seconds and 29 seconds.

Comment 6

[Gian-Carlo Pascutto [:gcp]]

Also happens on: https://en.wikipedia.org/wiki/House_of_Merode

Comment 7

[Gian-Carlo Pascutto [:gcp]]

This is a clip from the above Wikipedia page:

https://www.youtube.com/watch?v=MDgLyqyTMgI

Comment 8

[Gian-Carlo Pascutto [:gcp]]

I have a theory. Could this be the inverse of bug 1203349?

When we fling up and the URLbar gets hidden, the fling stop immediately (this is an annoying bug), but the hiding of the URLbar causes things to move around a bit in the wrong direction giving the impression that the scroll resets.

I think that's consistent with watching the videos in slow motion. What do you guys think?

Comment 9

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

It's certainly possible, and so far the most likely explanation IMO. We dispatch a resize event to content when the URL bar shows/hides, and that might trigger stuff in either layout or in the content that causes the scroll position to reset.

Comment 10

[Jan Henning [:JanH]]

I don't think that this is really URL-specific - it's just any page that requires scrolling.
Also, my impression is that this seems to happen if you lift the finger after the URL bar has started sliding in/out and before it has completed its movement.

Comment 11

[Gian-Carlo Pascutto [:gcp]]

(In reply to Jan Henning (:JanH) from comment #10)
> I don't think that this is really URL-specific - it's just any page that
> requires scrolling.

Yes, absolutely. The correlation to some pages was only because it requires a specific motion to trigger, and the content spacing on those pages made that specific scroll motion more likely.

Comment 12

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

Actually let me undo that. I'm not sure if this issue is the same as the one I intend to fix, so let me file a new bug and fix that one. Then we can come back to this and see what's left here.

Comment 13

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

Once bug 1243547 is landed I'd like to see if that helps the scenarios here at all. The scenario in comment 10 sounds very related but it's not clear to me it's exactly the same thing.

Comment 14

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

gcp, can you check in the latest nightly to see if the issue you originally filed this for is still happening?