class file_handler : public handler {
    public:
      file_handler( canvas* x ) : c(x) {}
  
      int operator()() {
  	char* key = _event->arg(1);
      	if (!strcmp("Open", key)) launch("OPEN");
      	else if (!strcmp("Save", key)) launch("SAVE");
      	else if (!strcmp("OPEN", key)) open();
      	else if (!strcmp("SAVE", key)) save();
      	return OK;
      }
  
    protected:
      canvas* c;
      file_chooser* f;
      
      void launch(char* args) {       // launch new filechooser
      	f = new file_chooser();
      	f->handler(this, args);
      }
  
      void open() { tk->source( f->get() ); f->destroy(); }
      void save() { c->postscript( f->get() ); f->destroy(); }
    };