\slide{class-filechooser}{The {\em file_chooser} class}{
  class file_chooser : public toplevel {
  file_chooser() : toplevel( gensym() ) { init(); }
  int operator()();
  char* get() { return e->get(); }
  protected:
  button* b; button *c; 
OK and cancel buttons
entry* e; listbox* l; int install(char* s, action& a, char* opts); void init(); void list(); }
}