set both to NULL to signal refusal (ie already downloading) */
typedef void (*VikDataSourceGetCmdStringFunc) ( gpointer user_data, gchar **babelargs_or_shellcmd, gchar **inputfile_or_inputtype );
typedef void (*VikDataSourceGetCmdStringFuncWithInput) ( gpointer user_data, gchar **babelargs_or_shellcmd, gchar **inputfile_or_inputtype, const gchar *input_file_name );
typedef void (*VikDataSourceGetCmdStringFuncWithInputInput) ( gpointer user_data, gchar **babelargs_or_shellcmd, gchar **inputfile_or_inputtype, const gchar *input_file_name, const gchar *input_track_file_name );
set both to NULL to signal refusal (ie already downloading) */
typedef void (*VikDataSourceGetCmdStringFunc) ( gpointer user_data, gchar **babelargs_or_shellcmd, gchar **inputfile_or_inputtype );
typedef void (*VikDataSourceGetCmdStringFuncWithInput) ( gpointer user_data, gchar **babelargs_or_shellcmd, gchar **inputfile_or_inputtype, const gchar *input_file_name );
typedef void (*VikDataSourceGetCmdStringFuncWithInputInput) ( gpointer user_data, gchar **babelargs_or_shellcmd, gchar **inputfile_or_inputtype, const gchar *input_file_name, const gchar *input_track_file_name );