How to change icons and tray icons in Gnome?

Question

Even though I like using Gnome, this issues drives me crazy and even makes me consider switching to KDE.

I think the tray icons are quite useful for some application, and for others they are even essential. Since they are always visible, some of them are pretty distracting or at least annoying.

So I need a way to make them less distracting. I'm using the Papirus theme, which already takes care of blending in some the tray icons. But I'd like to make all of them flat white icons.

Reading the ArchWiki (I'm using Manjaro Gnome), forum posts and stackoverflow answers didn't get me to a solution.

Apparently, it should be possible to change the icons by putting icon files in the ~/.local/share/icons/. Doing this in the home directory, so the won't reverse when updating the appication or theme. Therefore I created my versions of the icons and put them in

~/.local/share/icons/Papirus/16x16/apps/
~/.local/share/icons/Papirus/16x16/panel/

I did the same for 24x24, ... , 256x256.

I also tried running gtk-update-icon-cache -f -t ~/.local/share/icons/Papirus or refreshing Gnome (with Alt+F2 and r), or switch the theme in Gnome Tweaks.

In many cases this didn't change anything, in others at least the icon in dash bar. But never the tray system icons.

When I search in the /usr/share/icons/ folder for application names, there are *.png, *.svg, *.xpm, *.xpm.svg etc. files, in folders named panel or apps. And then for some applications there are even icons in /usr/share/pixmaps.

What is the proper way to change use custom icons?

More specific:

• Which files/resolutions are for the tray icons?
• What is the order they are loaded?
• How to refresh to see the changes?

PS: I tried changing the tray icons for e.g. Veracrypt and Liferea on Manjaro Gnome

Update

• There are already flat white icons for Veracrypt in the Papirus theme (/usr/share/icons/Papirus/24x24/panel), that also seem to be ignored.
• And there is another Veracrypt icon in /usr/share/app-info/icons/archlinux-arch-community/64x64

Answer 1

There are a few things you need to understand.

1. Gnome doesn't support system tray since 3.26. It's their decision and we should accept it.
2. Some people don't agree with this and they started creating extensions for Gnome. I guess Manjaro ships some of these extensions as default.
3. When we are talking about tray icons themselves, this is quite a complicated subject. Some applications comply with standards and use icons from your icon theme e.g., /usr/share/icons/, ~/.local/share/icons. But there are applications (mainly electron-based), which use their specific icons in their specific directories and sometimes even icons hard-coded in binaries.
4. There is a community project called Hardcode-Tray, whose main goal is to find these ugly hard-coded icons and replace them with icons from your icon theme. But
5. Hardcode-Tray works only with applications specified in their so-called database. I'm afraid there is currently no fix available¹ for the rest of them.

I hope this helps you understand what is going on here.

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^{1. When an application is not present in the Hardoce-Tray database, it doesn't necessarily mean, it can't be fixed. The project is community-based and you can open a new GitHub issue and discuss the specific application with developers.}