Creates a new `GtkApplication` instance.
When using `GtkApplication`, it is not necessary to call [[email protected]] manually. It is called as soon as the application gets registered as the primary instance.
Concretely, [[email protected]] is called in the default handler for the `GApplication:GtkApplication:startup` signal.
Therefore, `GtkApplication` subclasses should always chain up in their `GApplication:GtkApplication:startup` handler before
using any GTK API.
Note that commandline arguments are not passed to [[email protected]].
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.
| application_id |
The application ID |
| flags |
the application flags |
|
a new `GtkApplication` instance |