This function initializes GTK with [func@Gtk.
init], as well as GEGL and babl.
It also sets up various other things so that the plug-in user looks and behaves like the GIMP core. This includes selecting the GTK theme and setting up the help system as chosen in GIMP preferences. Any plug-in that provides a user interface should call this function.
It can safely be called more than once. Calls after the first return quickly with no effect.
| prog_name |
The name of the plug-in which will be passed as argv[0] to `gtk_init()`. It's a convention to use the name of the executable and _not_ the PDB procedure name. |