Bug 193350 – [GTK] Momentum scrolling stops abruptly before websites end

• Status: RESOLVED
• Resolution: FIXED
• Component: WebKitGTK

[Christian Kaindl]

Created attachment 358892 [details]
Version/build details

I am using the Epiphany Technology Preview (see attached screenshot). When I scroll with my trackpad, I have momentum scrolling in Epiphany. When I scroll fast so that the momentum is enough to reach the end of the website, then the scrolling stops abruptly (up to ~50px) before the real end of the website is reached. So it needs a second scroll to really reach the top (which is what I did in the video, that is not lag)
In my testing, the harder/faster the momentum scroll is, the bigger the gap is. This also happens with Epiphany 3.28 (which is what is in my OS repositories right now). I created a screen cast showing the issue, so it is easier to understand: https://www.youtube.com/watch?v=Q-3YBoONEuA

I am using a Purism Librem 13 v2 laptop (I am not sure on the trackpad specifics, any command help for terminal output appreciated).
My operation system is the newsest Solus GNOME edition, currently running GNOME 2.28.


Note: This issue was originally filed on Epiphany's bug tracker: https://gitlab.gnome.org/GNOME/epiphany/issues/615

[Alice Mikhaylenko]

Created attachment 360570 [details]
Patch

[Alice Mikhaylenko]

The problem is that when velocity is immediately set to 0 after overshooting, and any position change is ignored when velocity is already 0.

[EWS Watchlist]

Comment on attachment 360570 [details]
Patch

Attachment 360570 [details] did not pass ios-sim-ews (ios-simulator-wk2):
Output: https://webkit-queues.webkit.org/results/10951388

New failing tests:
imported/w3c/web-platform-tests/webrtc/simplecall.https.html

[EWS Watchlist]

Created attachment 360576 [details]
Archive of layout-test-results from ews125 for ios-simulator-wk2

The attached test failures were seen while running run-webkit-tests on the ios-sim-ews.
Bot: ews125  Port: ios-simulator-wk2  Platform: Mac OS X 10.13.6

[Michael Catanzaro]

Comment on attachment 360570 [details]
Patch

Note this code is copied from gtkkineticscrolling.c in GTK+. Do we want to resync with them? It looks like we've both made a few improvements since this was copied.

[Alice Mikhaylenko]

This particular part isn't copied. GTK has full-fledged overshooting instead: https://gitlab.gnome.org/GNOME/gtk/blob/gtk-3-24/gtk/gtkkineticscrolling.c#L146-218

Also, the last change in gtk-3-24 branch is from 2 years ago, and is already in webkit.

[WebKit Commit Bot]

Comment on attachment 360570 [details]
Patch

Clearing flags on attachment: 360570

Committed r240789: <https://trac.webkit.org/changeset/240789>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.