player.py

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"""
Player listens to messages from the timeline and publishes them to ROS.
"""

import rospy
import rosgraph_msgs

from python_qt_binding.QtCore import QObject

CLOCK_TOPIC = "/clock"

class Player(QObject):
    """
    This object handles publishing messages as the playhead passes over their position
    """
    def __init__(self, timeline):
        super(Player, self).__init__()
        self.timeline = timeline

        self._publishing = set()
        self._publishers = {}

        self._publish_clock = False
        self._last_clock = rosgraph_msgs.msg.Clock()
        self._resume = False

    def resume(self):
        self._resume = True

    def is_publishing(self, topic):
        return topic in self._publishing

    def start_publishing(self, topic):
        if topic in self._publishing:
            return
        self._publishing.add(topic)
        self.timeline.add_listener(topic, self)

    def stop_publishing(self, topic):
        if topic not in self._publishing:
            return
        self.timeline.remove_listener(topic, self)

        if topic in self._publishers:
            self._publishers[topic].unregister()
            del self._publishers[topic]

        self._publishing.remove(topic)

    def start_clock_publishing(self):
        if CLOCK_TOPIC not in self._publishers:
            # Activate clock publishing only if the publisher was created successful
            self._publish_clock = self.create_publisher(CLOCK_TOPIC, rosgraph_msgs.msg.Clock())

    def stop_clock_publishing(self):
        self._publish_clock = False
        if CLOCK_TOPIC in self._publishers:
            self._publishers[CLOCK_TOPIC].unregister()
            del self._publishers[CLOCK_TOPIC]

    def stop(self):
        for topic in list(self._publishing):
            self.stop_publishing(topic)
        self.stop_clock_publishing()

    def create_publisher(self, topic, msg):
        try:
            try:
                self._publishers[topic] = rospy.Publisher(topic, type(msg), queue_size=100)
            except TypeError:
                self._publishers[topic] = rospy.Publisher(topic, type(msg))
            return True
        except Exception as ex:
            # Any errors, stop listening/publishing to this topic
            rospy.logerr('Error creating publisher on topic %s for type %s. \nError text: %s' % (topic, str(type(msg)), str(ex)))
            if topic != CLOCK_TOPIC:
                self.stop_publishing(topic)
            return False

    def message_viewed(self, bag, msg_data):
        """
        When a message is viewed publish it
        :param bag: the bag the message is in, ''rosbag.bag''
        :param msg_data: tuple of the message data and topic info, ''(str, msg)''
        """
        # Don't publish unless the playhead is moving.
        if self.timeline.play_speed <= 0.0:
            return

        topic, msg, clock = msg_data

        # Create publisher if this is the first message on the topic
        if topic not in self._publishers:
            self.create_publisher(topic, msg)

        if self._publish_clock:
            time_msg = rosgraph_msgs.msg.Clock()
            time_msg.clock = clock
            if self._resume or self._last_clock.clock < time_msg.clock:
                self._resume = False
                self._last_clock = time_msg
                self._publishers[CLOCK_TOPIC].publish(time_msg)
        self._publishers[topic].publish(msg)

    def message_cleared(self):
        pass

    def event(self, event):
        """
        This function will be called to process events posted by post_event
        it will call message_cleared or message_viewed with the relevant data
        """
        bag, msg_data = event.data
        if msg_data:
            self.message_viewed(bag, msg_data)
        else:
            self.message_cleared()
        return True