Check scrollability by actually scrolling elements

[femnad]

Addresses #825

When findScrollable yields no results, check if we can return the current scrollingElement instead, ignoring doneScrolling check this time. This fixes the behaviour when it's not possible to scroll up from the bottom of a page.

[ghost]

I have tested this commit on the following web pages:

1. https://en.wikipedia.org/wiki/Main_Page
2. https://music.youtube.com
3. https://github.com/enkore/j4-dmenu-desktop

It works on Wikipedia but, unfortunately, it does not work for the others.

Tested on Firefox 82.0b8.

[femnad]

Yeah, you're right, embarrassingly I've only tested on Hacker News. However, the behavior on those sites you've mentioned is similarly broken on master. So I propose changing the scrolling logic somewhat which has the downside of reintroducing #267 but fixes the scrolling on other sites. This could be applied as a temporary measure to fix the existing scrolling bug until there is another implementation which can address #267 without causing problems in other sites.

[femnad]

New proposal; when seeking scrollable elements, evaluate style checks first and then actually scroll (down and back up) the element to see if it can be scrolled. Credit for that approach goes to Vimium.

Tested on:

• Hacker News
• Gmail
• Youtube Music
• Github repo pages
• Wikipedia main page

[ghost]

I can confirm it's working great on all those previously affected web pages with the latest commit. Excellent work @femnad!

[ueokande]

great!

[aminroosta]

Just saw this in the release notes.
Guys, you rock! Thank you so much for keeping this the best vim plugin for firefox.

[apiraino]

thanks @femnad for fixing this up :)