Added topic query methods.

CMakeLists.txt

@@ -69,6 +69,7 @@ set(SOURCES
   include/qml_ros_plugin/subscriber.h
   include/qml_ros_plugin/tf_transform.h
   include/qml_ros_plugin/tf_transform_listener.h
+  include/qml_ros_plugin/topic_info.h
   include/qml_ros_plugin/time.h
   src/array.cpp
   src/action_client.cpp

docs/pages/Ros-Singleton.rst

@@ -33,15 +33,52 @@ following ``RosInitOptions`` options:
 * | ``AnonymousName``:
   | Anonymize the node name. Adds a random number to the node's name to make it unique.
 * | ``NoRosout``:
-  | Don't broadcast rosconsole output to the /rosout topic. See :ref:`Logging`
+  | Don't broadcast rosconsole output to the /rosout topic. See :doc:`Logging`
 
 .. code-block:: qml
 
   Component.onCompleted: {
     Ros.init("node_name", RosInitOptions.AnonymousName | RosInitOptions.NoRosout)
   }
 
+Query Topics
+------------
+
+You can also use the Ros singleton to query the available topics.
+Currently, three methods are provided:
+
+* | ``QStringList queryTopics( const QString &datatype = QString())``
+  | Queries a list of topics with the given datatype or all topics if no type provided.
+* | ``QList<TopicInfo> queryTopicInfo()``
+  | Retrieves a list of all advertised topics including their datatype. See :cpp:class:`TopicInfo`
+* | ``QString queryTopicType( const QString &name )``
+  | Reterieves the datatype for a given topic.
+
+Example:
+
+.. code-block:: qml
+
+  // Retrieves a list of topics with the type sensor_msgs/Image
+  var topics = Ros.queryTopics("sensor_msgs/Image")
+  // Another slower and less clean method of this would be
+  var cameraTopics = []
+  var topics = Ros.queryTopicInfo()
+  for (var i = 0; i < topics.length; ++i) {
+    if (topics[i].datatype == "sensor_msgs/Image") cameraTopics.push(topics[i].name)
+  }
+  // The type of a specific topic can be retrieved as follows
+  var datatype = Ros.queryTopicType("/topic/that/i/care/about")
+  // Using this we can make an even worse implementation of the same functionality
+  var cameraTopics = []
+  var topics = Ros.queryTopics() // Gets all topics
+  for (var i = 0; i < topics.length; ++i) {
+    if (Ros.queryTopicType(topics[i]) == "sensor_msgs/Image") cameraTopics.push(topics[i])
+  }
+
 API
 ---
+.. doxygenclass:: qml_ros_plugin::TopicInfo
+  :members:
+
 .. doxygenclass:: qml_ros_plugin::RosQmlSingletonWrapper
   :members:

include/qml_ros_plugin/goal_handle.h

@@ -9,8 +9,6 @@
 #include <ros_babel_fish/actionlib/babel_fish_action.h>
 #include <ros_babel_fish/babel_fish.h>
 
-#include <utility>
-
 namespace qml_ros_plugin
 {
 

include/qml_ros_plugin/ros.h

@@ -6,6 +6,7 @@
 
 #include "qml_ros_plugin/console.h"
 #include "qml_ros_plugin/node_handle.h"
+#include "qml_ros_plugin/topic_info.h"
 
 #include <QJSValue>
 #include <QObject>
@@ -95,6 +96,27 @@ Q_OBJECT
    */
   void setThreads( int count );
 
+  /*!
+   * Queries the ROS master for its topics or using the optional datatype parameter for all topics with the given type.
+   * @param datatype The message type to filter topics for, e.g., sensor_msgs/Image. Omit to query for all topics.
+   * @return A list of topics that matches the given datatype or all topics if no datatype provided.
+   */
+  QStringList queryTopics( const QString &datatype = QString()) const;
+
+  /*!
+   * Queries the ROS master for its topics and their type.
+   * @return A list of TopicInfo.
+   */
+  QList<TopicInfo> queryTopicInfo() const;
+
+  /*!
+   * Queries the ROS master for a topic with the given name.
+   * @param name The name of the topic, e.g., /front_camera/image_raw.
+   * @return The type of the topic if found, otherwise an empty string.
+   */
+  QString queryTopicType( const QString &name ) const;
+
+
   Console console() const;
 
 signals:
@@ -154,6 +176,15 @@ Q_OBJECT
   //! @copydoc RosQml::setThreads
   Q_INVOKABLE void setThreads( int count );
 
+  //! @copydoc RosQml::queryTopics
+  Q_INVOKABLE QStringList queryTopics( const QString &datatype = QString()) const;
+
+  //! @copydoc RosQml::queryTopicInfo
+  Q_INVOKABLE QList<TopicInfo> queryTopicInfo() const;
+
+  //! @copydoc RosQml::queryTopicType
+  Q_INVOKABLE QString queryTopicType( const QString &name ) const;
+
   Console console() const;
 
   /*!

include/qml_ros_plugin/topic_info.h

@@ -0,0 +1,40 @@
+// Copyright (c) 2020 Stefan Fabian. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+#ifndef QML_ROS_PLUGIN_TOPIC_INFO_H
+#define QML_ROS_PLUGIN_TOPIC_INFO_H
+
+#include <QArgument>
+#include <QMetaType>
+#include <QString>
+
+namespace qml_ros_plugin
+{
+
+class TopicInfo
+{
+Q_GADGET
+  // @formatter:off
+  //! The name of the topic, e.g., /front_camera/image_raw
+  Q_PROPERTY( QString name READ name )
+  //! The datatype of the topic, e.g., sensor_msgs/Image
+  Q_PROPERTY( QString datatype READ datatype )
+  // @formatter:on
+public:
+  TopicInfo() = default;
+
+  TopicInfo( QString name, QString datatype ) : name_( std::move( name )), datatype_( std::move( datatype )) { }
+
+  const QString &name() const { return name_; }
+
+  const QString &datatype() const { return datatype_; }
+
+private:
+  QString name_;
+  QString datatype_;
+};
+}
+
+Q_DECLARE_METATYPE( qml_ros_plugin::TopicInfo );
+
+#endif //QML_ROS_PLUGIN_TOPIC_INFO_H

src/qml_ros_plugin.cpp

@@ -49,6 +49,8 @@ Q_OBJECT
                                                       } );
     qmlRegisterUncreatableType<NodeHandle>( "Ros", 1, 0, "NodeHandle",
                                             "Error: Can not create NodeHandle manually in QML." );
+    qmlRegisterUncreatableType<TopicInfo>( "Ros", 1, 0, "TopicInfo",
+                                           "Error: No point in creating TopicInfo in QML and it's not supported." );
     qmlRegisterUncreatableType<Publisher>( "Ros", 1, 0, "Publisher",
                                            "Error: Can not create Publisher manually in QML. Use one of the advertise functions." );
 

src/ros.cpp

@@ -6,6 +6,7 @@
 #include "qml_ros_plugin/publisher.h"
 #include "qml_ros_plugin/subscriber.h"
 
+#include <ros/master.h>
 #include <ros/ros.h>
 
 #include <QCoreApplication>
@@ -73,6 +74,47 @@ void RosQml::setThreads( int count )
   updateSpinner();
 }
 
+QStringList RosQml::queryTopics( const QString &datatype ) const
+{
+  ros::master::V_TopicInfo topic_info;
+  ros::master::getTopics( topic_info );
+  QStringList result;
+  std::string std_datatype = datatype.toStdString();
+  for ( const auto &topic : topic_info )
+  {
+    if ( !std_datatype.empty() && topic.datatype != std_datatype ) continue;
+    result.append( QString::fromStdString( topic.name ));
+  }
+  return result;
+}
+
+QList<TopicInfo> RosQml::queryTopicInfo() const
+{
+  ros::master::V_TopicInfo topic_info;
+  ros::master::getTopics( topic_info );
+  QList<TopicInfo> result;
+  for ( const auto &topic : topic_info )
+  {
+    result.append( { QString::fromStdString( topic.name ), QString::fromStdString( topic.datatype ) } );
+  }
+  return result;
+}
+
+QString RosQml::queryTopicType( const QString &name ) const
+{
+  if ( name.isEmpty()) return {};
+  ros::master::V_TopicInfo topic_info;
+  ros::master::getTopics( topic_info );
+  QList<TopicInfo> result;
+  std::string std_name = name.toStdString();
+  for ( const auto &topic : topic_info )
+  {
+    if ( std_name != topic.name ) continue;
+    return QString::fromStdString( topic.datatype );
+  }
+  return {};
+}
+
 void RosQml::checkInitialized()
 {
   if ( !ros::isInitialized()) return;
@@ -154,6 +196,18 @@ void RosQmlSingletonWrapper::spinOnce() { RosQml::getInstance().spinOnce(); }
 
 void RosQmlSingletonWrapper::setThreads( int count ) { RosQml::getInstance().setThreads( count ); }
 
+QStringList RosQmlSingletonWrapper::queryTopics( const QString &datatype ) const
+{
+  return RosQml::getInstance().queryTopics( datatype );
+}
+
+QList<TopicInfo> RosQmlSingletonWrapper::queryTopicInfo() const { return RosQml::getInstance().queryTopicInfo(); }
+
+QString RosQmlSingletonWrapper::queryTopicType( const QString &name ) const
+{
+  return RosQml::getInstance().queryTopicType( name );
+}
+
 Console RosQmlSingletonWrapper::console() const { return RosQml::getInstance().console(); }
 
 QJSValue RosQmlSingletonWrapper::debug()

test/communication.cpp

@@ -195,6 +195,62 @@ TEST( Communication, subscriber )
     FAIL() << "Shouldn't have received the message that was published while the subscriber wasn't running.";
 }
 
+TEST( Communication, queryTopics )
+{
+  ros::NodeHandle nh;
+  ros::Publisher pub1 = nh.advertise<geometry_msgs::Pose>( "/query_topics/pose1", 10 );
+  ros::Publisher pub2 = nh.advertise<geometry_msgs::Vector3>( "/query_topics/vector3", 10 );
+  ros::Publisher pub3 = nh.advertise<geometry_msgs::Point>( "/query_topics/point1", 10 );
+  ros::Publisher pub4 = nh.advertise<geometry_msgs::Point>( "/query_topics/point2", 10 );
+  ros::Publisher pub5 = nh.advertise<geometry_msgs::Pose>( "/query_topics/pose2", 10 );
+  ros::Publisher pub6 = nh.advertise<geometry_msgs::Pose>( "/query_topics/pose3", 10 );
+  RosQmlSingletonWrapper wrapper;
+  waitFor( []() { return false; } ); // Wait some time
+  QStringList topics = wrapper.queryTopics();
+  std::string debug_topics;
+  for ( const QString &topic : topics ) debug_topics += '\n' + topic.toStdString();
+  for ( const QString &topic : QStringList{ "/query_topics/pose1", "/query_topics/vector3", "/query_topics/point1",
+                                            "/query_topics/point2", "/query_topics/pose2", "/query_topics/pose3" } )
+  {
+    EXPECT_TRUE( topics.contains( topic ))
+            << topic.toStdString() << " is not in topics." << std::endl << "Declared topics:" << debug_topics;
+  }
+  topics = wrapper.queryTopics( "geometry_msgs/Point" );
+  for ( const QString &topic : QStringList{ "/query_topics/point1", "/query_topics/point2" } )
+  {
+    EXPECT_TRUE( topics.contains( topic )) << topic.toStdString() << " is not in topics of type Point";
+  }
+  topics = wrapper.queryTopics( "geometry_msgs/Pose" );
+  for ( const QString &topic : QStringList{ "/query_topics/pose1", "/query_topics/pose2", "/query_topics/pose3" } )
+  {
+    EXPECT_TRUE( topics.contains( topic )) << topic.toStdString() << " is not in topics of type Pose";
+  }
+  QList<TopicInfo> topic_info = wrapper.queryTopicInfo();
+  for ( const QPair<QString, QString> &pair : QList<QPair<QString, QString>>{{ "/query_topics/pose1",    "geometry_msgs/Pose" },
+                                                                             { "/query_topics/vector3", "geometry_msgs/Vector3" },
+                                                                             { "/query_topics/point1",  "geometry_msgs/Point" },
+                                                                             { "/query_topics/point2",  "geometry_msgs/Point" },
+                                                                             { "/query_topics/pose2",   "geometry_msgs/Pose" },
+                                                                             { "/query_topics/pose3",   "geometry_msgs/Pose" }} )
+  {
+    bool found = false;
+    debug_topics = "";
+    for ( const TopicInfo &info : topic_info )
+    {
+      debug_topics += '\n' + info.name().toStdString();
+      if ( info.name() != pair.first ) continue;
+      EXPECT_EQ( info.datatype(), pair.second );
+      found = true;
+    }
+    EXPECT_TRUE( found ) << "Did not find " << pair.first.toStdString() << " in topic types." << std::endl << "Topics:" << debug_topics;
+  }
+
+  EXPECT_EQ( wrapper.queryTopicType( "/query_topics/point1" ), "geometry_msgs/Point" );
+  EXPECT_EQ( wrapper.queryTopicType( "/query_topics/pose2" ), "geometry_msgs/Pose" );
+  EXPECT_TRUE( wrapper.queryTopicType( "/query_topics/pose20" ).isEmpty())
+          << wrapper.queryTopicType( "/query_topics/pose20" ).toStdString();
+}
+
 TEST( Communication, serviceCall )
 {
   qml_ros_plugin::Service service;