[snap] cursor theme isn't respected

Possibly relevant code in chromium: ui/base/cursor/cursor_loader_x11.cc

See also bug #1833611.

Broken on KDE by default.

The KDE theme isn't supported because gtk-common-themes doesn't include the default KDE cursor theme. This MR fixes that: https://gitlab.gnome.org/Community/Ubuntu/gtk-common-themes/merge_requests/17

Fixed for me (Kubuntu 19.10 default mouse theme) as is https://bugs.launchpad.net/bugs/1833611 ("[snap] mouse pointer on Ubuntu flavours is retro-looking when hovering over links").

Confirm, this and #1833611 are both fixed for me (Kubuntu 19.10, Breeze)

Status changed to 'Confirmed' because the bug affects multiple users.

Fix committed in xubuntu-default-settings:
- https://github.com/Xubuntu/xubuntu-default-settings/commit/7ea4e59df2394140b28cf92b2651d327a800f00f
- https://github.com/Xubuntu/xubuntu-default-settings/commit/f2ee8c4526862248edba19dc8a1aca9dfa10059b

Basically, we were referencing a theme that no longer exists, "Human", so the theme was falling back on Default. There is no default theme in gtk-common-themes, so the fallback X11 theme was used instead.

Probably related: bug #1892085.

This bug was fixed in the package xubuntu-default-settings - 21.04.0

---------------
xubuntu-default-settings (21.04.0) hirsute; urgency=medium

  * etc/xdg/xdg-xubuntu/xfce4/xfconf/xfce-perchannel-xml/xsettings.xml:
    - Set Gtk/CursorThemeName to DMZ-White (LP: #1838008)
  * etc/xdg/xdg-xubuntu/menus/xfce-applications.menu:
    - Hide confusing xfce4-terminal-settings.desktop
  * usr/share/xubuntu/applications/xfce4-terminal.desktop:
    - Dropped, enable showing in the menu (LP: #1851387)
  * etc/xdg/xdg-xubuntu/xfce4/panel/default.xml:
    - Migrate statusnotifier to systray and remove from panel (LP: #1907871)
    - Remove separator between clock and tray, add padding
    - Enable pulseaudio plugin window focus support
  * etc/xdg/xdg-xubuntu/xfce4/helpers.rc:
    - Change FileManager key to lowercase thunar to fix defaults
  * debian/live/whiskermenu-1.rc,
    etc/xdg/xdg-xubuntu/menus/xfce-applications.menu,
    etc/xdg/xdg-xubuntu/xfce4/whiskermenu/defaults.rc,
    usr/share/xubuntu/applications/defaults.list:
    - Replace exo-* with xfce4-* commands
  * etc/xdg/xdg-xubuntu/xfce4/xfconf/xfce-perchannel-xml/xfce4-desktop.xml:
    - Hide default icons: File System and Removable Devices
    - Exclude applications menu on desktop right click
  * etc/xdg/xdg-xubuntu/xfce4/xfconf/xfce-perchannel-xml/thunar.xml:
    - Switch default location selector to path bar
    - Enabled opening folders in new tab on middle click
    - Disabled changing window icon for special folders
  * etc/xdg/xdg-xubuntu/xfce4/xfconf/xfce-perchannel-xml/xfce4-keyboard-shortcuts.xml:
    - Apply upstream keyboard bindings:
      - Ctrl+Alt+Delete: xfce4-session-logout
      - Ctrl+Shift+Escape: xfce4-taskmanager
      - Super+R: xfrun4
      - Super+E, Ctrl+Alt+F: exo-open --launch FileManager

 -- Sean Davis <email address hidden> Sat, 12 Dec 2020 14:26:01 -0500

The themes listed in the description are now included in gtk-common-themes which should resolve the issue

you:~$ cp /var/lib/snapd/snaps/gtk-common-themes_1535.snap ~/
you:~$unsquashfs gtk-common-themes_1535.snap
you:~$ cp -rf xxx squashfs-root/share/icons/default/
you:~$ mksquashfs squashfs-root/ gtk-common-themes_1535.snap.n -all-root -comp lzo
you:~$ sudo mv gtk-common-themes_1535.snap.n /var/lib/snapd/snaps/gtk-common-themes_1535.snap

So you're unpacking gtk-common-themes, adding something (xxx ?) to the icon theme, and repacking it. Can you explain why you're doing that?

The correct way would be to submit a PR against https://github.com/ubuntu/gtk-common-themes, which would address the problem you're encountering for everyone, and would ensure your modifications aren't discarded the next time the snap is updated.