Sergio Costas authored Mar 28, 2020 and Rastersoft committed May 19, 2020

When a program (like Nautilus) modifies the metadata in a file
(like metadata::custom-icon) there is no way of detecting that
change from other programs: neither inotify generates an event
in the file or the directory holding it, nor is possible to use
it in the files at, or the folder itself,
~/.local/share/gvfs-metadata, because writting in them is delayed
for nearly a minute.

Unfortunately, there are cases where it is needed to be able
to detect that. An example (and the reason for this patch) is
when Nautilus (or another file manager) modifies the custom
icon in a file from the desktop, and the desktop is managed
by a different program (in this case, Desktop Icons NG), because
the later can't detect the change made by the former and, thus,
the file will keep the old icon until the whole desktop is
refreshed.

To fix this, this patch proposes to add a signal to the
org.gtk.vfs.Metadata DBus interface, which will be triggered
whenever a key is modified. To avoid saturating the system in
case of modifying a lot of keys, it is triggered up to once
per second.