int  initPBM(char ***mime_types, int *nrtypes, float **prefs);
  int  openPBM(const W3ADocumentInfo doc,  Widget  win, long id);
 int writePBM(long id, const char *buf, size_t nbytes);
  int  closePBM(long id);
 void eventPBM(long id, long source, long eventtype, void *params);
  int  infoPBM(long id, W3ADocumentInfo *doc);