GLibOptionArgFunc

gboolean
(* GOptionArgFunc) (
  const gchar* option_name,
  const gchar* value,
  gpointer data,
  GError** error
)

The type of function to be passed as callback for G_OPTION_ARG_CALLBACK options.

`option_name`	`const gchar*`
	The name of the option being parsed. This will be either a single dash followed by a single letter (for a short name) or two dashes followed by a long option name.
	The data is owned by the caller of the function.
	The value is a NUL terminated UTF-8 string.
`value`	`const gchar*`
	The value to be parsed.
	The data is owned by the caller of the function.
	The value is a NUL terminated UTF-8 string.
`data`	`gpointer`
	User data added to the `GOptionGroup` containing the option when it was created with `g_option_group_new()`
	The argument can be `NULL`.
	The data is owned by the caller of the function.
`error`	`GError **`
	The return location for a `GError*`, or `NULL`.

Returns:	`gboolean`
	`TRUE` if the option was successfully parsed, `FALSE` if an error occurred, in which case `error` should be set with `g_set_error()`