example RQT plugin in C++ that uses signals/slots

I cannot for the life of me figure out how to use signals and slots to pass information to the GUI widget in an RQT plugin that is written in C++. The ROS Tutorial for creating a C++ RQT plugin doesn't even have any data widgets in the GUI, let alone any code to show how to use signals/slots to pipe data to a data widget: http://wiki.ros.org/rqt/Tutorials/Writing%20a%20C%2B%2B%20Plugin After several hours of trial and error, I was able to figure out a solution for using signals/slots in a Python RQT plugin, but I can't seem to make the stretch to C++. Here is the python example I created starting from the ROS Tutorial for creating a python RQT plugin (https://github.com/lucasw/rqt_mypkg) and then adding some of this code from ROS Answers where a user asked how to use signals/slots in python: http://answers.ros.org/question/224152/pyqt-signals-for-ros-callbacks-in-rqt-plugin/ my_module.py: import os import rospy from qt_gui.plugin import Plugin from python_qt_binding import loadUi from python_qt_binding.QtGui import QWidget from std_msgs.msg import Int32 from PyQt4.QtCore import SIGNAL class MyPlugin(Plugin): def __init__(self, context): super(MyPlugin, self).__init__(context) # Give QObjects reasonable names self.setObjectName('MyPlugin') # Process standalone plugin command-line arguments from argparse import ArgumentParser parser = ArgumentParser() # Add argument(s) to the parser. parser.add_argument("-q", "--quiet", action="store_true", dest="quiet", help="Put plugin in silent mode") args, unknowns = parser.parse_known_args(context.argv()) if not args.quiet: print 'arguments: ', args print 'unknowns: ', unknowns # Create QWidget self._widget = QWidget() # Get path to UI file which is a sibling of this file # in this example the .ui and .py file are in the same folder ui_file = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'MyPlugin.ui') # Extend the widget with all attributes and children from UI file loadUi(ui_file, self._widget) # Give QObjects reasonable names self._widget.setObjectName('MyPluginUi') # Show _widget.windowTitle on left-top of each plugin (when # it's set in _widget). This is useful when you open multiple # plugins at once. Also if you open multiple instances of your # plugin at once, these lines add number to make it easy to # tell from pane to pane. if context.serial_number() > 1: self._widget.setWindowTitle(self._widget.windowTitle() + (' (%d)' % context.serial_number())) # Add widget to the user interface context.add_widget(self._widget) # kurt added these lines self.sub = rospy.Subscriber('my_data', Int32, self.ros_msg_callback, queue_size=1) self.connect(self, SIGNAL("changeUI(PyQt_PyObject)"), self.monitoring_slot) # kurt added this callback def ros_msg_callback(self, data): self.emit(SIGNAL("changeUI(PyQt_PyObject)"), data) pass # kurt added this slot routine def monitoring_slot(self, data): self._widget.data_myData.setText(str(data)) self._widget.data_myData.setStyleSheet("color: black; background-color: red;") pass def shutdown_plugin(self): # TODO unregister all publishers here pass def save_settings(self, plugin_settings, instance_settings): # TODO save intrinsic configuration, usually using: # instance_settings.set_value(k, v) pass def restore_settings(self, plugin_settings, instance_settings): # TODO restore intrinsic configuration, usually using: # v = instance_settings.value(k) pass #def trigger_configuration(self): # Comment in to signal that the plugin has a way to configure # This will enable a setting button (gear icon) in each dock widget title bar # Usually used to open a modal configuration dialog MyPlugin.ui: Form00400300FormLabel:10105030TBD70105030color: rgb(0, 255, 0); background-color: rgb(0, 0, 0);