When setting the icon theme to Adwaita, a mixture of new-style icons, old-style icons, and monochromatic icons is used for applications.

That's because Adwaita doesn't provide icons for third-party applications, so you'll get whatever icon the software developer provides. For monochromatic icons. that is because Adwaita only provides symbolic scalable icons for those.

Solution: Use a real icon theme that supports third-party icons, like Papirus.

My problem is not that Adwaita doesn't a custom icon for Firefox (I actually prefer this) . It's that it doesn't use the correct Nautilus icon in Solus.

The only thing I care about is that the GNOME Application icons are consistent. In my mind, it doesn't make a lot of sense to theme the Firefox/GIMP/Steam icons if they're inconsistent with their in-application logo/branding.

a month later

Actually, this must be a bug. I tested it against upstream vanilla GNOME icons, and for some reason Solus' Adwaita icons are not 3.32 like they should be. GNOME 3.32 released a new set of 2D icons, and while Solus is showing version 3.32, its Adwaita icons are <3.30 (i.e. the old 3D icons). You can just check this against any 3.32 screenshot. Nautilus is an obvious one, but really most of the Solus "3.32" Adwaita icons are not 3.32. This shouldn't be the case. I'm not sure if there was an overwrite, a renaming error, or what. I tried rebuilding the Solus icon cache to see if it was an update issue -- no go. Also extracted Solus Adwaita 3.32 icon theme eopkg, and they are definitely not 3.32.

I would never not use Papirus or Numix Square/Circle because I care about beauty in my UI life, but the fact remains this is definitely a versioning bug of some kind.

    JohannPopper
    Not sure what you're talking about as we are definitely on 3.32.0

    source     :
    - https://download.gnome.org/sources/adwaita-icon-theme/3.32/adwaita-icon-theme-3.32.0.tar.xz

    Build template: https://dev.getsol.us/source/adwaita-icon-theme/browse/master/package.yml

      For example, there was a lot of buzz on GNOME dev blogs about the new and easier to maintain Adwaita icon set that debuted with 3.32 Taipei. It is made entirely with 2D icons instead of the old 3D icons. Here is a screenshot of the 3.32 icons from a GNOME dev blog that was posted upon the 3.32 release. Note the Nautilus/Files icon for reference:

      https://www.gnome.org/news/2019/03/gnome-3-32-released/

      The following is a screenshot from my up-to-date Solus 4 GNOME 3.32 app overview with 'Adwaita (Default)' icons selected in Tweak. As you can see, the Files icon (and the others) are still the old 3D icons for some weird reason:

      Granted this is practically a non-issue for the default Solus UX (and I certainly have no horses in this race), but I want to rule out any chance that it may point to a deeper problem with my updates or the stack. Unsolved mysteries can be dangerous. Perhaps it's as simple as the new Adwaita not recognizing Files and Software due to Solus having 3.26 Files and an entirely different Software app.

        JohannPopper

        The Files (Nautilus) icon comes from Nautilus 3.32's data, not Adwaita Icon Theme. Our Nautilus is intentionally held back to allow the continued use of desktop icons under Budgie.

          Yeah, I've confirmed it by updating nautilus locally, it then uses the right icon with Adwaita, but due to the desktop icons being stripped out we can't update in the repo.

            Justin It uses the right icon with Adwaita because Adwaita doesn't actually ship the icon (weird to me since I'd expect all their first-party apps to have icons in a dedicated theme but hey, I'll let GNOME be GNOME), but rather the icon theming system just fallback on the hicolor and pixmaps, which Nautilus itself ships 🙂