public Application (string? application_id, ApplicationFlags flags)
Creates a new Application instance.
Note that commandline arguments are not passed to init. All GTK+ functionality that is available via commandline arguments can also be achieved by setting suitable environment variables such as `G_DEBUG`, so this should not be a big problem. If you absolutely must support GTK+ commandline arguments, you can explicitly call init before creating the application instance.
If non-null, the application ID must be valid. See id_is_valid.
If no application ID is given then some features (most notably application uniqueness) will be disabled.
The application ID.
the application flags
a new Application instance