const screen_width = 10;
int current_text_pos = 0;

char screen_buffer[screen_width];

void clear_screen()
{
  for(int i = 0; i < screen_width; i++) screen_buffer[i] = ' ';
}

void fill_screen_buffer(String text)
{
  int buffer_pos = 0;

  if (current_text_pos + screen_width >= text.length)
  {
      for(int i = current_text_pos; i <= text.length; i++)
      {
        screen_buffer[buffer_pos] = text[i];
        buffer_pos++;
      }

      buffer_pos++; // space

      for(int i = 0; i < (current_text_pos + screen_width + text.length) - text.length - 1; i++)
      {
        screen_buffer[buffer_pos] = text[i];
        buffer_pos++;
      }
  } else {
    for(int i = current_text_pos; i < screen_width + current_text_pos; i++)
    {
      screen_buffer[buffer_pos] = text[i];
      buffer_pos++;
    }
  }
}