How do I restore (or change) the default folder icon for special folders?

Question

I removed Documents Pictures and Downloads from my home directory, and I linked them to directories on different disks. And now Documents and Pictures have lost their nice categorized icon of a camera and, well, documents.

Interestingly, Downloads did not.

$ gio info ~/Documents | grep symbolic-icon
  standard::symbolic-icon: folder-symbolic, folder
$ gio info ~/Pictures | grep symbolic-icon
  standard::symbolic-icon: folder-symbolic, folder
$ gio info ~/Downloads | grep symbolic-icon
  standard::symbolic-icon: folder-download-symbolic, folder-symbolic, folder-download, folder

You can find those keywords in one of the many themes installed on the computer, because these are named according to a spec. This means they don't need a path, because chaning your theme will automatically change the icon too, in the new theme style, but in the designated category (e.g. Downloads). It will look for any of the listed names in the chosen theme.

$ ls -1 /usr/share/icons/Mint-Y/places/symbolic | grep folder
  folder-documents-symbolic.svg
  folder-download-symbolic.svg
  folder-music-symbolic.svg
  folder-pictures-symbolic.svg
  folder-publicshare-symbolic.svg
  folder-remote-symbolic.svg
  folder-saved-search-symbolic.svg
  folder-symbolic.svg
  folder-templates-symbolic.svg
  folder-videos-symbolic.svg

However, I am not allowed to set this.

$ gio set ~/Documents standard::symbolic-icon folder-documents-symbolic
  gio: Setting attribute standard::symbolic-icon not supported
$ gio set ~/Pictures standard::symbolic-icon folder-pictures-symbolic
  gio: Setting attribute standard::symbolic-icon not supported

Turns out, you can only set metadata::custom-icon, But it does not support global icon names. You need to specify an exact path, meaning you need to fix all your icons when you change your theme!

I don't know how it works technically, why the symbolic-icon metadata has disappeared. But even though I cannot set it with GIO, It is defined somewhere, for certain folders.

Where is this defined? If I cannot do it as user, I should be able to do it as root. I will recompile things if I have to. I want my flipping folder icons back!

Using Ubuntu 18.04/Linux Mint 19 w/ Cinnamon > Nemo

Answer 1

I finally figured it out. This metadata is not stored with the directories, but in a single file. You can edit this file and even set directories outside of your home, in case you have directories deferred to different partitions.

~/.config/user-dirs.dirs

You won't see the changes until you log out and in again, but you can verify the value of standard::icon using gvfs-info <dirname>,

-update-

You can also use the xdg-user-dirs-update command to update this file:

xdg-user-dirs-update --set DOWNLOAD ~/D0wnloadz`