getContext
Gets the struct@GLib.MainContext with which the source is associated.
You can call this on a source that has been destroyed, provided that the struct@GLib.MainContext it was attached to still exists (in which case it will return that struct@GLib.MainContext). In particular, you can always call this function on the source returned from func@GLib.main_current_source. But calling this function on a source whose struct@GLib.MainContext has been destroyed is an error.
Return
the #GMainContext with which the source is associated, or null if the context has not yet been added to a source.