Detecting GVfs metadata support through C API

[Reuben Green <reubengreen73 gmail com>]

Hello,

I am currently implementing a feature in a file browser to allow users 
to store viewing settings for each directory (e.g. sort order for 
displaying files). I am using GFile attributes to store this metadata, 
using methods like g_file_set_attributes_async to store key-value pairs. 
As I understand it, being able to write such metadata relies on the GVfs 
metadata service being available.

I would like to detect when support for GVfs metadata is available using 
the C API. By "GVfs metadata support is available" I mean essentially 
"functions like g_file_set_attributes_async can successfully save 
metadata so that it will be available in future". My current method for 
doing this is to query DBus to see if the service name 
org.gtk.vfs.Metadata is available, and this method seems to function OK. 
However, I would like to know if there is a better way of doing this 
check (by "better" I mean roughly "more robust and accurate"), and in 
particular if it can be done without a DBus query.

One method I have considered is looking at the list of running processes 
for the name "gvfsd-metadata", but that seems a bit kludgy to me, and 
perhaps unreliable (though I am not too sure about this).

I have asked a question about this on Stack Overflow which gives some 
more details, see 
https://stackoverflow.com/questions/62715510/testing-for-gvfs-metadata-support-in-c

I would be very grateful for any help with this.

Many thanks,

Reuben Green