Setting GWeatherInfo:location to null helpfully doesn't mean
"no location", but "NYC". This obviously isn't what we want
to show users, so track the location validity separately and
consider it when updating the label shown to users.
https://bugzilla.gnome.org/show_bug.cgi?id=780252
If GeoClue is not responding for some reason, the callback of
Geoclue.Simple.new would not get called, meaning that _gclueFailed
remains false. This is preventing the fallback to the most recently
used location in gnome-weather, because it requires _gclueFailed to be
true (or auto-location to be disabled). So neither code path sets a
location and the libgweather default (New York City) is being used
instead.
https://bugzilla.gnome.org/show_bug.cgi?id=779898
Weather conditions - at least as far as online services are
concerned - don't usually change in a couple of minutes.
So when updating shortly after a previous update, assume
the current conditions are still valid and trigger an
update without showing a loading indication. This should
help a bit with not getting stuck permanently in loading
state when on a shitty network.
https://bugzilla.gnome.org/show_bug.cgi?id=754031
In preparation of integrating GNOME Weather, add a helper class that
retrieves weather information according to Weather's configuration
if the application is installed.
https://bugzilla.gnome.org/show_bug.cgi?id=754031
