Application: force use portals

[danirabbit]

This forces Switchboard to use portals even though it's not in a sandbox. What this means practically is that Switchboard plugs will use the native file chooser instead of the one from Gtk

[davidmhewitt]

Remember that this will potentially stop notifications and deleting files from working for the same reasons as https://github.com/elementary/default-settings/pull/215 and possibly any number of other random issues.

Probably nothing in switchboard sends notifications, but I imagine one of the plugs might need to be able to delete files.

[davidmhewitt]

My bad, it's not deleting files, it's trashing files, which we probably don't do in switchboard.

Either way, this environment variable causes GLib and GTK to use portals for a bunch of stuff which could potentially cause issues with stuff now, or issues with stuff in the future as more portals come along.

So I'm not sure this is a good thing to start adding in a bunch of places and then we'll wonder why random things don't work in a year or two.

[jhaygood86]

One thing that is related and interesting:

GTK's documentation says this:

• When the org.freedesktop.portal.FileChooser portal is available on
• the session bus, it is used to bring up an out-of-process file chooser.
• Depending on the kind of session the application is running in, this may
• or may not be a GTK file chooser.

However, the very first thing the Portal implementation does is check for gdk_should_use_portal, which only returns true if the app is sandboxed OR that environment variable is in place... which is very different behavior from the documentation.

[danirabbit]

I'm gonna merge this into the gtk4 port so we have plenty of time to watch for issues :)