I took the icon directly from Adwaita repository as of today's version:
https://gitlab.gnome.org/GNOME/adwaita-icon-theme/-/blob/master/Adwaita/scalable/status/software-update-available-symbolic.svg
By being installed on our local GIMP-only hicolor, this gets picked up
after any custom theme software-update-available version. I didn't
install it inside the Symbolic or Color theme because anyway Adwaita
seems only to provide a single vector version. There is a color version,
yet as PNG icons and installed in the legacy/ section. I don't think it
makes sense to use an icon considered as legacy by its author and
without vector version. So I just install the symbolic version and all
themes can fallback to it (be them symbolic icon themes or not).
This icon comes from the Adwaita repository and is therefore licensed
under the terms of either the GNU LGPL v3 or Creative Commons
Attribution-Share Alike 3.0 United States License. See:
https://gitlab.gnome.org/GNOME/adwaita-icon-theme/-/blob/master/COPYING
These icons are not available in any of our themes (Symbolic or Color).
Also they don't seem to be available in many icon themes either actually
and I'm not sure GIMP properly fallbacks to system icon theme when an
icon is missing in the selected theme anyway (I think to remember this
used to work, but it doesn't look like it works anymore).
Anyway I just copied the 2 symbolic switch on|off icons available in the
GTK+ repository at gtk/icons/scalable/status/. These are supposed to be
used by GtkSwitch but somehow they aren't. So for the time being, let's
bundle them directly with GIMP (until we figure something better out).
I put them in hicolor because this is the generic/default theme which is
always used as last resort and is common to any theme. It means any
specific theme will be able to override these icons, but if missing,
hicolor will be able to provide a fallback.
Jehan
