Folder/Sidebar Icons on Linux

[elsiehupp]

Expected behaviour

• Any folder named "Nextcloud" in the top level of a user's home directory should have a distinctive icon.
• When this folder is placed in the Nautilus/Nemo sidebar, it should have a distinctive icon there, too (this is ostensibly a feature on macOS, but it hasn't worked recently for me).

Actual behaviour

In both the main view and the sidebar, the folder named "Nextcloud" has the same icon as any other folder.

Client configuration

Client version: 3.1.3
Operating system: Ubuntu 20.10
OS language: English (United States)

Qt version used by client package (Linux only, see also Settings dialog): ??? (it doesn't say)

Client package (Linux only): Flathub

Installation path of client: Fluthub

Potential Fix

I was looking into how folder icons work on Linux, and the norm appears to be assigning them with gio. I checked the icons of several folders and got the following output:

$ gio info ~/Nextcloud | grep icon
  standard::icon: inode-directory, folder, inode-directory-symbolic, folder-symbolic
  standard::symbolic-icon: inode-directory-symbolic, folder-symbolic, inode-directory, folder
$ gio info ~/Documents | grep icon
  standard::icon: folder-documents, folder, folder-documents-symbolic, folder-symbolic
  standard::symbolic-icon: folder-documents-symbolic, folder-symbolic, folder-documents, folder

Basically, ~/Nextcloud could be assigned the following values:

standard::icon: folder-nextcloud, folder, folder-nextcloud-symbolic, folder-symbolic
standard::symbolic-icon: folder-nextcloud-symbolic, folder-symbolic, folder-nextcloud, folder

And then the icon theme could do the rest. My recommendation would be to submit Nextcloud folder icons to as many themes as possible, though it would make sense for folder-nextcloud-symbolic to ship with Nextcloud Desktop because it isn't themed. (This would just be the Nextcloud logo, not a folder with the Nextcloud logo like the large version.)

I did a quick Nextcloudification of the default Ubuntu folder icon, and this is what I got:

Doing a blue icon with the Nextcloud logo seems preferable to doing a default-colored icon with a Nextcloud-icon badge because that way it doesn't have to be recolored for variations on the icon theme. Also it's just a bit less cluttered. FWIW there should probably be a small-size version of the icon, as well, based on the corresponding small-size folder icon from a given icon theme.

This approach—letting the Linux theming engine know that it should look for a special icon—also seems relatively easy to theme for OEM providers, given that you could just use values like folder-${APPLICATION_EXECUTABLE} and folder-${APPLICATION_EXECUTABLE}-symbolic.