Bug 191637 – Scrolling is choppy on exocomics.com in Safari but not in Chrome

• Component: Scrolling
• Status: NEW

[Zev Eisenberg]

Created attachment 354820 [details]
video demonstrating the issue in Safari

On pages on exocomics.com, such as https://www.exocomics.com/540, page scrolling is quite choppy on my MacBook Pro 15-inch 2018 running Safari 12.0.1 (14606.2.104.1.1) on macOS 10.14.1 (18B75). It's also choppy on Safari Technology Preview Release 69 (Safari 12.1, WebKit 14607.1.12). But scrolling is buttery smooth on Chrome Version 70.0.3538.102 (Official Build) (64-bit).

Please let me know if I should file a radar instead.

[Zev Eisenberg]

Created attachment 354822 [details]
sample of the Safari Web Content process reproducing the bug

Adding attached sample of Safari Web Content during bug reproduction

[Simon Fraser (smfr)]

The page has background-attachment:fixed: on both body and html, and different background images on each, so we fall out of our optimized scrolling code path.

[Zev Eisenberg]

Just re-tested in Safari 12.1.1 (14607.2.6.1.1) on macOS 10.14.5 (18F203), and scrolling is smooth now. The web page appears not to have changed, so it looks like this is fixed in Safari now. Going to leave open because I’m not sure what to do, but feel free to mark as resolved if appropriate.