1401526 - Page content jumps vertically during vertical flings in which the URL bar disappears

Status: VERIFIED FIXED

(Firefox for Android Graveyard :: Toolbar, defect, P3)

Description

[Mark]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_5) AppleWebKit/603.2.4 (KHTML, like Gecko) Version/10.1.1 Safari/603.2.4

Steps to reproduce:

Firefox for Android 57.0a1 2017-09-19

If Firefox is set to auto-hide the URL bar (turning Settings -> General -> Full-screen browsing ON), then flinging the content of any non-trival page upward while the URL bar is still visible causes the content to jump upwards as the URL bar scrolls out of view. 

The reverse is sometimes true, flinging content gently downwards sometimes causes a jump as the URL bar scrolls back into view.

The effect is easiest to see with slow flings of a few cm per second. It must be a fling, i.e. the finger must have left the screen before the URL bar starts to disappear. I think the effect is there for all flings during which the URL bar disappears during the “finger off” portion of the fling. But the effect is easiest to see on a “slow fling”.

I think the content jumps up by exactly the height of the URL bar, but I am not sure. I think the effect is also present on Firefox Android 56. I think the effect is more pronounced on Firefox Android 57 because the URL bar is taller than on Firefox Android 56. 

I see the same effect on two phones (Sony Xperia X Compact running Android 7.1.1 and BQ Aquaris X5 running Android 6.0).

Steps to replicate:-

* ensure URL bar is set to auto-hide by turning Settings -> General -> Full-screen browsing ON. 
* navigate to any non-trivial page, www.gsmarena.com is a good example
* wait for page loading to complete
* ensure URL bar is visible
* fling the page GENTLY upwards, move finger about 1 cm, really just a sliding tap, and remove finger from screen BEFORE the URL bar disappears. After the finger is removed, page should drift upwards on the fling inertia and push the URL bar out of the way. 
* content jumps upwards by circa 1 cm as the URL bar gets pushed up out of the way.
* reverse the effect by doing a similar “slow fling” downwards, sometimes content jumps down as the URL bar re-appears

I think the effect is present on any fling during which the URL bar disappears, but it is easiest to see with a “slow fling”. The finger really just needs to do a “sliding tap” on the screen to get the slow fling going.


Actual results:

Page jumps by around 1 cm as the URL bar disappears


Expected results:

Page should pan smoothly as the URL bar disappears

Comment 1

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

Randall, can you look into this?

Comment 2

[Randall Barker [:rbarker]]

Looks like the content is no longer getting scrolled down when the composition bounds are resized to fill the screen before the toolbar is animated off the screen.

Comment 3

[Mark]

Is this related to bug 1390145? Sounds like the same problem but IIRC the jumping I describe has been around for a few releases & still persists in current Nightly. I've tried toggling apz.frame_delay.enabled and it made no difference that I could see. I'll attach a video. Cheers now.

Comment 4

[Mark]

Attachment: Scroll jank during toolbar hide.mp4

Comment 5

[Mark]

If you fixed this I think you would make some of us very happy. I think these commenters might be seeing this bug.


https://arstechnica.com/gadgets/2018/01/firefoxs-continued-quantum-transformation-more-multithreading-tracking-protection/?comments=1

"For a while now (I'm on the nightly though) Firefox on mobile has been extremely fast. The issue with it is that there's a stutter when scrolling which seems to be unrelated to actual site load speed or memory usage, and it makes the browser feel slow and choppy even though it isn't. "

...

"Ah, yeah, that explains what I've been seeing - and this is on an OG Pixel, so it's unlikely to be an issue with the phone's OEM skin"

;)

Comment 6

[Chris Peterson [:cpeterson]]

Is this a Fennec front-end issue (not adjust the scroll position to account for the new view size) or a GeckoView core issue?

Comment 7

[Mark]

For fun I built a version of Klar/Focus with GeckoView and it did not show this jumping problem. But I am no expert.

Comment 8

[Botond Ballo [:botond]]

(In reply to Mark from comment #7)
> For fun I built a version of Klar/Focus with GeckoView and it did not show
> this jumping problem. But I am no expert.

Does it still have a URL bar that appears/disappears as you scroll?

Comment 9

[Randall Barker [:rbarker]]

The hitch is caused by the dynamic toolbar. Focus with GeckoView isn't using the dynamic toolbar.

Comment 10

[Mark]

All I can say is the FocusGeckoView toolbar slides in and out of view nicely. The page content doesn't seem to jank when it does so. It also doesn't seem to have bug 1400557 (progress bar not always attached to toolbar) or bug 1411244 (overscroll highlights visible over toolbar).

FocusGeckoView UI feels much more polished to me and much more like a native Android app. It's really nice. Firefox Android OTOH seems to have a lot of loose ends around the scrolling and toolbar. I think it's important to get this right, I think you've got just a short period of time to impress new users, FF has to be as slick as Chrome / Samsung / Brave / Opera etc. IMHO ATM it's not.

Comment 11

[Mark]

Possibly fixed by resolution of bug 1448439 (change to Chromesque fling physics).

Comment 12

[Chris Peterson [:cpeterson]]

Resolving as fixed by bug 1448439 according to Mark's testing. Thanks!

Comment 13

[Sorina Florean [:sflorean]]

I can confirm that this is fixed on build 61.0b5 with Nexus 5(Android 6.0.1).