1. Go to http://www.theverge.com/ 2. As soon as the page is visible try and move the horizontal section of the stories posted on the site. It doesn't register the horizontal scroll movement until a certain point of loading but on Chrome it immediately registers as soon as the page appears. When the site(The Verge) has completely finished loading the performance is smooth Also In techcruch.com the horizontal scroll of elements on the site is janky and not smooth. Particularly terrible on m.facebook.com where horizontal scrolling elements appear as 'sponsored' content or suggested friends. Device: Moto G 2nd Gen Lollipop 5.0.2 FF 45 2015-12-01

(In reply to bull500 from comment #0) > 1. Go to http://www.theverge.com/ > 2. As soon as the page is visible try and move the horizontal section of the > stories posted on the site. > It doesn't register the horizontal scroll movement until a certain point of > loading but on Chrome it immediately registers as soon as the page appears. > > When the site(The Verge) has completely finished loading the performance is > smooth I believe this is because we haven't layerized the content in the horizontal div initially, and it takes a while for that to happen. During load there's a lot painting happening so layerization might get held up. I'm not sure what we can do about this, but it would be nice to find a solution. > Also In techcruch.com the horizontal scroll of elements on the site is janky > and not smooth. This is because they are implementing scrolling using touch listeners. > Particularly terrible on m.facebook.com where horizontal scrolling elements > appear as 'sponsored' content or suggested friends. Ditto. These last two are evangelism issues and I'm not going to track them in this bug. If you would like to see them fixed please file separate bugs for them as the webcompat team will have to reach out to the site owners.

Kartikaya, what do you suggest theverge should modify to be less janky? It seems to be an optimization issue of Firefox, and I'm always a bit reluctant to contact a site when the issue is on our side, except if something is really a question of different code paths in JS for example.

I don't think theverge should modify anything; that is entirely on us. It's techcrunch and Facebook that are doing scrolling via JS rather than letting the browser handle it.

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