When using GtkApplication, it is not necessary to call [func@Gtk.init]
manually. It is called as soon as the application gets registered as
the primary instance.
Concretely, [func@Gtk.init] is called in the default handler for the
GApplication::startup signal. Therefore, GtkApplication subclasses should
always chain up in their GApplication::startup handler before using any GTK
API.
Note that commandline arguments are not passed to [func@Gtk.init].
If application_id is not %NULL, then it must be valid. See
g_application_id_is_valid().
If no application ID is given then some features (most notably application
uniqueness) will be disabled.
Creates a new GtkApplication instance.
When using GtkApplication, it is not necessary to call [func@Gtk.init] manually. It is called as soon as the application gets registered as the primary instance.
Concretely, [func@Gtk.init] is called in the default handler for the GApplication::startup signal. Therefore, GtkApplication subclasses should always chain up in their GApplication::startup handler before using any GTK API.
Note that commandline arguments are not passed to [func@Gtk.init].
If application_id is not %NULL, then it must be valid. See g_application_id_is_valid().
If no application ID is given then some features (most notably application uniqueness) will be disabled.