int  initPlain(char ***mime_types, int *nrtypes, float **prefs);
  int  openPlain(const W3ADocumentInfo info,  Widget  work_area, long id);
 int writePlain(long id, const char *buf, size_t nbytes);
  int  closePlain(long id);
 void eventPlain(long id, long source, long eventtype, void *params);
  int  infoPlain(long id, W3ADocumentInfo *doc);