Automatic tower positioning

New "auto-position" switch to always use closest tower for tower-view.
Exposes new "/sim/airport/closest-airport-id" property.
Display closest airport on groundradar by default.

src/Environment/environment_mgr.cxx

@@ -42,6 +42,7 @@
 #include "precipitation_mgr.hxx"
 #include "ridge_lift.hxx"
 #include "terrainsampler.hxx"
+#include "Airports/simple.hxx"
 
 class SGSky;
 extern SGSky *thesky;
@@ -49,8 +50,11 @@ extern SGSky *thesky;
 FGEnvironmentMgr::FGEnvironmentMgr () :
   _environment(new FGEnvironment()),
   fgClouds(new FGClouds()),
+  _cloudLayersDirty(true),
   _altitudeNode(fgGetNode("/position/altitude-ft", true)),
-  _cloudLayersDirty(true)
+  _longitude_n(fgGetNode( "/position/longitude-deg", true )),
+  _latitude_n( fgGetNode( "/position/latitude-deg", true )),
+  _positionTimeToLive(0.0)
 {
   set_subsystem("controller", Environment::LayerInterpolateController::createInstance( fgGetNode("/environment/config", true ) ));
   set_subsystem("realwx", Environment::RealWxController::createInstance( fgGetNode("/environment/realwx", true ) ), 1.0 );
@@ -203,6 +207,33 @@ FGEnvironmentMgr::update (double dt)
     _cloudLayersDirty = false;
     fgClouds->set_update_event( fgClouds->get_update_event()+1 );
   }
+
+  _positionTimeToLive -= dt;
+  if( _positionTimeToLive <= 0.0 )
+  {
+      // update closest airport information
+      _positionTimeToLive = 30.0;
+
+      SG_LOG(SG_ALL, SG_INFO, "FGEnvironmentMgr::update: updating closest airport");
+
+      SGGeod pos = SGGeod::fromDeg(_longitude_n->getDoubleValue(),
+                                   _latitude_n->getDoubleValue());
+
+      FGAirport * nearestAirport = FGAirport::findClosest(pos, 100.0);
+      if( nearestAirport == NULL )
+      {
+          SG_LOG(SG_ALL,SG_WARN,"FGEnvironmentMgr::update: No airport within 100NM range");
+      }
+      else
+      {
+          const string currentId = fgGetString("/sim/airport/closest-airport-id", ""); 
+          if (currentId != nearestAirport->ident())
+          {
+              fgSetString("/sim/airport/closest-airport-id",
+                      nearestAirport->ident().c_str());
+          }
+      }
+  }
 }
 
 FGEnvironment

src/Environment/environment_mgr.hxx

@@ -94,8 +94,11 @@ private:
 
   FGEnvironment * _environment;	// always the same, for now
   FGClouds *fgClouds;
-  SGPropertyNode_ptr _altitudeNode;
   bool _cloudLayersDirty;
+  SGPropertyNode_ptr _altitudeNode;
+  SGPropertyNode_ptr _longitude_n;
+  SGPropertyNode_ptr _latitude_n;
+  double _positionTimeToLive;
   simgear::TiedPropertyList _tiedProperties;
 };
 

src/Instrumentation/groundradar.cxx

@@ -47,7 +47,7 @@
 #include "groundradar.hxx"
 
 static const char* airport_source_node_name = "airport-id-source";
-static const char* default_airport_node_name = "/sim/tower/airport-id";
+static const char* default_airport_node_name = "/sim/airport/closest-airport-id";
 static const char* texture_node_name = "texture-name";
 static const char* default_texture_name = "Aircraft/Instruments/Textures/od_groundradar.rgb";
 static const char* range_source_node_name = "range-source";

src/Main/fg_init.cxx

@@ -793,14 +793,44 @@ static bool fgSetTowerPosFromAirportID( const string& id) {
 
 struct FGTowerLocationListener : SGPropertyChangeListener {
     void valueChanged(SGPropertyNode* node) {
-        const string id(node->getStringValue());
+        string id(node->getStringValue());
+        if (fgGetBool("/sim/tower/auto-position",true))
+        {
+            // enforce using closest airport when auto-positioning is enabled 
+            const char* closest_airport = fgGetString("/sim/airport/closest-airport-id", "");
+            if (closest_airport && (id != closest_airport))
+            {
+                id = closest_airport;
+                node->setStringValue(id);
+            }
+        }
         fgSetTowerPosFromAirportID(id);
     }
 };
 
+struct FGClosestTowerLocationListener : SGPropertyChangeListener
+{
+    void valueChanged(SGPropertyNode* )
+    {
+        // closest airport has changed
+        if (fgGetBool("/sim/tower/auto-position",true))
+        {
+            // update tower position
+            const char* id = fgGetString("/sim/airport/closest-airport-id", "");
+            if (id && *id!=0)
+                fgSetString("/sim/tower/airport-id", id);
+        }
+    }
+};
+
 void fgInitTowerLocationListener() {
     fgGetNode("/sim/tower/airport-id",  true)
         ->addChangeListener( new FGTowerLocationListener(), true );
+    FGClosestTowerLocationListener* ntcl = new FGClosestTowerLocationListener();
+    fgGetNode("/sim/airport/closest-airport-id", true)
+        ->addChangeListener(ntcl , true );
+    fgGetNode("/sim/tower/auto-position", true)
+           ->addChangeListener(ntcl, true );
 }
 
 static void fgApplyStartOffset(const SGGeod& aStartPos, double aHeading, double aTargetHeading = HUGE_VAL)
@@ -1163,6 +1193,7 @@ bool fgInitPosition() {
         // An airport + parking position is requested
         if ( fgSetPosFromAirportIDandParkpos( apt, parkpos ) ) {
             // set tower position
+            fgSetString("/sim/airport/closest-airport-id",  apt.c_str());
             fgSetString("/sim/tower/airport-id",  apt.c_str());
             set_pos = true;
         }
@@ -1173,6 +1204,7 @@ bool fgInitPosition() {
         if ( fgSetPosFromAirportIDandRwy( apt, rwy_no, rwy_req ) ) {
             // set tower position (a little off the heading for single
             // runway airports)
+            fgSetString("/sim/airport/closest-airport-id",  apt.c_str());
             fgSetString("/sim/tower/airport-id",  apt.c_str());
             set_pos = true;
         }
@@ -1183,6 +1215,7 @@ bool fgInitPosition() {
         if ( fgSetPosFromAirportIDandHdg( apt, hdg ) ) {
             // set tower position (a little off the heading for single
             // runway airports)
+            fgSetString("/sim/airport/closest-airport-id",  apt.c_str());
             fgSetString("/sim/tower/airport-id",  apt.c_str());
             set_pos = true;
         }