keyboard space for pause/resume when playing ros2 bag

[liuxw7]

modify code for player.cpp in rosbag2_transport

modify function:

void Player::play_messages_until_queue_empty(const PlayOptions & options)
{
  // 第一次加载执行线异步线程函数
  if (is_storage_completely_loaded()) {
    return;
  }
  ReplayableMessage message;

  float rate = 1.0;
  // Use rate if in valid range
  if (options.rate > 0.0) {
    rate = options.rate;
  }
  // 开始不暂停:paused = false;
  std::chrono::system_clock::time_point pause_true_time;
  std::chrono::system_clock::time_point pause_false_time;
  std::chrono::nanoseconds sum_delta_time(0);
  while (rclcpp::ok() && message_queue_.size_approx()) {
    int c = scan_keyboard();
    if (c == ' ') {
      paused_.store(!paused_.load());
      if (paused_.load() == true) {
        pause_true_time = std::chrono::system_clock::now();
      } else {
        pause_false_time = std::chrono::system_clock::now();
        std::chrono::nanoseconds delta =  std::chrono::duration_cast<std::chrono::nanoseconds>(pause_false_time - pause_true_time);
        sum_delta_time += delta;
      }
    }
    
    if (paused_.load() == true) {
      if (rclcpp::ok()) {
        auto publisher_iter = publishers_.find(message.message->topic_name);
        if (publisher_iter != publishers_.end()) {
          publisher_iter->second->publish(message.message->serialized_data);
        }
      }
      std::this_thread::sleep_for(std::chrono::milliseconds(static_cast<long>((1.0 / rate) * 1000)));
    } else { // 未暂停
        if (message_queue_.try_dequeue(message)) { // 有数据可用
          std::this_thread::sleep_until(start_time_ + sum_delta_time +          
              std::chrono::duration_cast<std::chrono::nanoseconds>(1.0 / rate * message.time_since_start));
            auto publisher_iter = publishers_.find(message.message->topic_name);
        if (publisher_iter != publishers_.end()) {
          publisher_iter->second->publish(message.message->serialized_data);
        }
      }
    }
  }
}

add new function

int Player::scan_keyboard(void)
{
  struct termios oldt, newt;
  int ch;
  int oldf;

  tcgetattr(STDIN_FILENO, &oldt);
  newt = oldt;
  newt.c_lflag &= ~(ICANON | ECHO);
  newt.c_cc[VTIME] = 0;
  newt.c_cc[VMIN] = 1;
  tcsetattr(STDIN_FILENO, TCSANOW, &newt);
  oldf = fcntl(STDIN_FILENO, F_GETFL, 0);
  fcntl(STDIN_FILENO, F_SETFL, oldf | O_NONBLOCK);
  
  ch = getchar();
  
  tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
  fcntl(STDIN_FILENO, F_SETFL, oldf);

  if(ch != EOF)
  {
    return ch;
  } 
  return 0;
}

in ros2 foxy, I has tested it in location. I hope it usefully for someone.

[emersonknapp]

Closing as duplicate of #55

Note: we will be using https://github.com/ros-tooling/keyboard_handler package to manage keyboard handling, to avoid putting any of that OS-specific code in rosbag2 Player.

#847 is already in progress to implement this feature - it is awaiting a full release of keyboard_handler