1780552 - Scrollbar styling through userChrome.css

Status: UNCONFIRMED

(Core :: CSS Parsing and Computation, enhancement)

Description

[Frank Steiner]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0

Steps to reproduce:

Hi,
I'm not sure if this should be considered a bug or a feature request. After the scrollbar change in FF 100 I'd like to restyle the scrollbars in more detail (e.g. thumb borders etc.) as it was possible with gtk.css via themes before.
However, anything like
thumb { border: 1px solid red;}
doesn't have any effect, while it works fine when I select a thumb in the devtools and add this rule for the element.

So, I wonder if this is intentionally blocked somewhere or it's just because scrollbars are inside a #shadow-root element. If the latter is the reason, could scrollbars be styled via author sheets or with the component registrar?

cu,
Frank