Expose current dark/light mode over gsettings

[danirabbit]

Problem

Currently to get/set the current color scheme we have to create a whole DBusProxy and talk to accounts service and it's all very messy and ugly.

Proposal

It would be nice to have the current dark/light/nopreference exposed over gsettings so that we can get/set this without having to do a whole bunch of extra work

Prior Art (Optional)

See: https://github.com/elementary/quick-settings/blob/833718813cd3d346aecc99de635122a5896de115/src/PopoverWidget.vala#L36

[lenemter]

I think it would be better if you could do this using Granite rather than gsettings.

[danirabbit]

@lenemter I don't think granite is really an appropriate place since it's an application library and this is only useful for desktop components

[Marukesu]

i think something akin to a libaccounts-pantheon is better, a gsetting will only be a extra place to keep things in sync and then we would need to deal with issues like the users's home/config directory being locked, or not readable/modifiable, etc...

[danirabbit]

I don't think any library is a solution to this problem. There are only two places that these are set-able: system settings and the panel.

Right now most of the related settings are exposed over gsettings but the dark/light setting itself is over dbus so there's a mix of gsettings and dbus required just to set light mode or dark mode.

It could be that it would be better to remove the existing gsettings and do everything over dbus, but right now there is a mix of both and it's messy