Issue #17 Fix aircraft labels setting not being updated in xswiftbus

Also related tidying up.

src/xswiftbus/drawable.h

@@ -34,6 +34,7 @@ namespace XSwiftBus
         //! Register the draw callback.
         void show()
         {
+            if (m_visible) { return; }
             m_visible = true;
             XPLMRegisterDrawCallback(callback, m_phase, m_before, static_cast<void*>(this));
         }
@@ -41,6 +42,7 @@ namespace XSwiftBus
         //! Unregister the draw callback.
         void hide()
         {
+            if (!m_visible) { return; }
             m_visible = false;
             XPLMUnregisterDrawCallback(callback, m_phase, m_before, static_cast<void*>(this));
         }

src/xswiftbus/settings.h

@@ -36,10 +36,12 @@ namespace XSwiftBus
     public:
         //! Get settings
         //! \threadsafe
+        //! \fixme Does this really need to be threadsafe?
         CSettings getSettings() const;
 
         //! Set settings
         //! \threadsafe
+        //! \fixme Does this really need to be threadsafe?
         void setSettings(const CSettings &settings);
 
         //! Get settings from xswiftbus.conf (needed during plugin initialization)

src/xswiftbus/traffic.cpp

@@ -605,24 +605,6 @@ namespace XSwiftBus
                     setDefaultIcao(defaultIcao);
                 });
             }
-            else if (message.getMethodName() == "setDrawingLabels")
-            {
-                maybeSendEmptyDBusReply(wantsReply, sender, serial);
-                bool drawing = true;
-                message.beginArgumentRead();
-                message.getArgument(drawing);
-                queueDBusCall([ = ]()
-                {
-                    setDrawingLabels(drawing);
-                });
-            }
-            else if (message.getMethodName() == "isDrawingLabels")
-            {
-                queueDBusCall([ = ]()
-                {
-                    sendDBusReply(sender, serial, isDrawingLabels());
-                });
-            }
             else if (message.getMethodName() == "setMaxPlanes")
             {
                 maybeSendEmptyDBusReply(wantsReply, sender, serial);
@@ -844,6 +826,7 @@ namespace XSwiftBus
     {
         invokeQueuedDBusCalls();
         doPlaneUpdates();
+        setDrawingLabels(getSettings().isDrawingLabels());
         emitSimFrame();
         m_countFrame++;
         return 1;
@@ -876,7 +859,6 @@ namespace XSwiftBus
     void CTraffic::interpolatePosition(Plane *plane)
     {
         std::memcpy(&plane->positions[3], &plane->positions[2], sizeof(plane->positions[2]));
-        return;
 
         const auto now = std::chrono::steady_clock::now();
         const auto t1 = plane->positionTimes[2] - plane->positionTimes[0];