Regularly request remote aircraft data from X-Plane

This includes
* ground elevation
* model offset (to be implemented)

ref T259

src/xswiftbus/traffic.cpp

@@ -380,6 +380,22 @@ namespace XSwiftBus
         }
     }
 
+    void CTraffic::requestRemoteAircraftData()
+    {
+        if (m_planesByCallsign.empty()) { return; }
+        const QList<Plane *> planes = m_planesByCallsign.values();
+        for (const Plane *plane : planes)
+        {
+            double lat = plane->position.lat;
+            double lon = plane->position.lon;
+            double elevation = plane->position.elevation;
+            double groundElevation = plane->terrainProbe.getElevation(lat, lon, elevation);
+            if (std::isnan(groundElevation)) { groundElevation = 0.0; }
+            constexpr double fudgeFactor = 3.0; //! \fixme Value should be different for each plane, derived from the CSL model geometry
+            emit remoteAircraftData(plane->callsign, lat, lon, groundElevation, fudgeFactor);
+        }
+    }
+
     //! memcmp function which ignores the header ("size" member) and compares only the payload (the rest of the struct)
     template <typename T>
     int memcmpPayload(T *dst, T *src)

src/xswiftbus/traffic.h

@@ -70,6 +70,9 @@ namespace XSwiftBus
         //! Signal emitted for each simulator rendering frame
         void simFrame();
 
+        //! Remote aircraft data
+        void remoteAircraftData(const QString &callsign, double latitude, double longitude, double elevation, double modelVerticalOffset);
+
     public slots:
         //! Initialize the multiplayer planes rendering and return true if successful
         bool initialize();
@@ -124,6 +127,9 @@ namespace XSwiftBus
         //! Set interpolation mode for a traffic aircraft
         void setInterpolatorMode(const QString &callsign, bool spline);
 
+        //! Request traffic plane data. A signal remoteAircraftData will be emitted for each known plane
+        void requestRemoteAircraftData();
+
     private:
         bool m_initialized = false;
         bool m_enabled = false;