[City-busz]

This is the standard location defined by freedesktop.org Icon Theme Specification.

Also, use that icon on the indicator to fix missing icon.

[dmytrotsuran]

Confirming this fixes a real bug on Ubuntu GNOME (Wayland) with Guake 3.10.1 from the Ubuntu package, using the ubuntu-appindicators extension and libayatana-appindicator3-1 0.5.94. The tray shows a generic "…" placeholder instead of the Guake icon.

The indicator asks for a themed icon name that no icon theme provides:

$ gdbus call --session -d <guake bus name> -o /org/ayatana/NotificationItem/guake_indicator \
    -m org.freedesktop.DBus.Properties.Get org.kde.StatusNotifierItem IconName
(<'guake-tray'>,)
$ ... IconThemePath
(<''>,)

guake-tray.svg/.png are only installed in /usr/share/guake/pixmaps/, which isn't on the icon theme search path, so the lookup fails.

This looks like a regression from a3ae752 (#2200). That commit replaced set_icon(img), which passed a full path, with set_icon_full("guake-tray", ...), which passes only a name. Before that, the old import appindicator nearly always failed on Python 3, so Guake fell back to Gtk.StatusIcon.set_from_file() and the icon worked. The same problem was fixed in 2015 by #591 (see #433).

A local workaround confirms the diagnosis. Copying the icon into the user hicolor theme and restarting Guake brings the icon back:

cp /usr/share/guake/pixmaps/guake-tray.svg ~/.local/share/icons/hicolor/scalable/apps/
gtk-update-icon-cache -f -t ~/.local/share/icons/hicolor

I haven't tested this PR's branch, but it does the same thing: it installs a named icon into hicolor and points the indicator at it.

One optional idea: calling self.tray_icon.set_icon_theme_path(IMAGE_DIR) (or the equivalent pixmaps dir) as well would keep the icon working for distro packages that don't use the Makefile install target.

Probably related: #2326, #2245.