Bug 215709

Created attachment 406956 [details]
Rubberbanding scrolling Safari 14 vs Safari 13

Safari Technology Preview
Release 112 (Safari 14.0, WebKit 15610.1.25.5.1)
OS: macOS 10.15.6
Device: MacBook Air 11 (2012)

I noticed that Rubberbanding is lagging in Release 112.

Steps to reproduce:

1.) Go to e.g. https://webkit.org/reporting-bugs/ and shrink the window so that you have vertical Scrollbars to scroll the page.
2.) Now scroll/swipe up and down quickly on the trackpad with rubberbanding effects on top and bottom of the page
3.) Compare step 1+2 with Safari Version 13.1.2

Actual result: In Release 112 it seems that the rubberbanding effect lags a bit or that the trackpad does not receive immediately respond to scroll after the rubberbanding effect.

Expected result: Nice and quick scrolling respond after the rubberbanding effect like in Safari Version 13.1.2


Another step to reproduce:

1.) Go to https://www.gmx.net
2.) Scroll to the top of the page to receive the rubberbanding effect.
3.) Do step 1+2 with Safari Version 13.1.2

Actual result: Rubberbanding is not smooth and lag a little bit.

Expected result: Smooth rubberbanding like in Safari Version 13.1.2.


Please find attached a screencast of both steps to reproduce (Safari 14 left and Safari 13 right). Maybe it is not so much noticeable in the screencast. But it is noticeable when doing it "live" on the device.

Thanks for checking!
Mehmet