GNU Readline: how to clear the input line?

Question

I use GNU Readline in the \"select\" fashion, by registering a callback function like so:

rl_callback_handler_install(\"\", on_readline_input);

Answer 1

I tried to separate server output and user input with ncurses windows. Server output is simulated with a thread. The program run until You enter a line beginning with 'q'.

#include  
#include  
#include  

WINDOW *top, *bottom;

int win_update( WINDOW *win, void *data ){
  wprintw(win,"%s", (char*)data ); wrefresh(win);
  return 0;
}

void *top_thread( void *data ){
  char buff[1024];
  int i=0;
  while(1){
    snprintf(buff, 1024, "SERVER OUTPUT: %i\n", i++ );
    use_window( top, win_update, (void*)buff );
    sleep(1);
  }
  return NULL;
}

int main(){
  initscr();
  int maxy, maxx;
  getmaxyx( stdscr, maxy, maxx );

  top = newwin(maxy-1,maxx,0,0);
  wsetscrreg(top,0,maxy-1); idlok(top,1); scrollok(top,1);
  pthread_t top_tid;
  pthread_create(&top_tid, NULL, top_thread, NULL);

  bottom = newwin(1,maxx,maxy-1,0);
  char buff[1024], input[maxx];
  do{
    werase(bottom); wmove(bottom,0,0);
    wprintw(bottom,"input> " ); wrefresh(bottom);
    wgetnstr(bottom,input,sizeof(input));
    snprintf(buff, 1024, "user input: '%s'\n", input );
    use_window( top, win_update, (void*)buff );
  }while( input[0] != 'q' );

  endwin();
}