Enhance the FGMetarEnvironmentCtrl class to also do on the fly weather

updates based on the "closest" airport with metar data available.  Note that
the web based query is in the main loop and causes brief sim pauses.  Update
rate (once per minute) needs to be tweaked with, but is a good value for
testing.

src/Environment/environment_ctrl.cxx

@@ -319,17 +319,14 @@ FGInterpolateEnvironmentCtrl::bucket::operator< (const bucket &b) const
 
 FGMetarEnvironmentCtrl::FGMetarEnvironmentCtrl ()
     : env( new FGInterpolateEnvironmentCtrl ),
-      _icao( strdup( fgGetString("/sim/presets/airport-id") ) )
+      _icao( fgGetString("/sim/presets/airport-id") ),
+      update_interval_sec( 60.0 ),
+      elapsed( 60.0 )
 {
 }
 
 FGMetarEnvironmentCtrl::~FGMetarEnvironmentCtrl ()
 {
-    if (_icao) {
-      free(_icao);
-      _icao = NULL;
-    }
-
    delete env;
    env = NULL;
 }
@@ -357,14 +354,8 @@ static void set_dewpoint_at_altitude( float dewpoint_degc, float altitude_ft ) {
 
 
 void
-FGMetarEnvironmentCtrl::init ()
+FGMetarEnvironmentCtrl::update_env_config ()
 {
-    if (_icao != NULL) {
-        free(_icao);
-        _icao = NULL;
-    }
-
-    fetch_data(_icao);
     fgSetupWind( fgGetDouble("/environment/metar/base-wind-range-from"),
                  fgGetDouble("/environment/metar/base-wind-range-to"),
                  fgGetDouble("/environment/metar/base-wind-speed-kt"),
@@ -378,33 +369,43 @@ FGMetarEnvironmentCtrl::init ()
                               station_elevation_ft );
     fgDefaultWeatherValue( "pressure-sea-level-inhg",
                            fgGetDouble("/environment/metar/pressure-inhg") );
+}
 
+void
+FGMetarEnvironmentCtrl::init ()
+{
+    const SGPropertyNode *longitude
+        = fgGetNode( "/position/longitude-deg", true );
+    const SGPropertyNode *latitude
+        = fgGetNode( "/position/latitude-deg", true );
+
+    bool found_metar = false;
+    while ( !found_metar ) {
+        FGAirport a = globals->get_airports()
+            ->search( longitude->getDoubleValue(),
+                      latitude->getDoubleValue(),
+                      true );
+        if ( fetch_data( a.id ) ) {
+            cout << "closest station w/ metar = " << a.id << endl;
+            _icao = a.id;
+            elapsed = 0.0;
+            update_env_config();
             env->init();
+            found_metar = true;
+        } else {
+            // mark as no metar so it doesn't show up in subsequent
+            // searches.
+            cout << "no metar at metar = " << a.id << endl;
+            globals->get_airports()->no_metar( a.id );
+        }
+    }
 }
 
 void
 FGMetarEnvironmentCtrl::reinit ()
 {
 #if 0
-    if (_icao != NULL) {
-        free(_icao);
-        _icao = NULL;
-    }
-
-    fetch_data(_icao);
-    fgSetupWind( fgGetDouble("/environment/metar/base-wind-range-from"),
-                 fgGetDouble("/environment/metar/base-wind-range-to"),
-                 fgGetDouble("/environment/metar/base-wind-speed-kt"),
-                 fgGetDouble("/environment/metar/gust-wind-speed-kt") );
-
-    fgDefaultWeatherValue( "visibility-m",
-                           fgGetDouble("/environment/metar/min-visibility-m") );
-    set_temp_at_altitude( fgGetDouble("/environment/metar/temperature-degc"),
-                          station_elevation_ft );
-    set_dewpoint_at_altitude( fgGetDouble("/environment/metar/dewpoint-degc"),
-                              station_elevation_ft );
-    fgDefaultWeatherValue( "pressure-sea-level-inhg",
-                           fgGetDouble("/environment/metar/pressure-inhg") );
+    update_env_config();
 #endif
 
     env->reinit();
@@ -413,6 +414,29 @@ FGMetarEnvironmentCtrl::reinit ()
 void
 FGMetarEnvironmentCtrl::update(double delta_time_sec)
 {
+    const SGPropertyNode *longitude
+        = fgGetNode( "/position/longitude-deg", true );
+    const SGPropertyNode *latitude
+        = fgGetNode( "/position/latitude-deg", true );
+    elapsed += delta_time_sec;
+    if ( elapsed > update_interval_sec ) {
+        FGAirport a = globals->get_airports()
+            ->search( longitude->getDoubleValue(),
+                      latitude->getDoubleValue(),
+                      true );
+        if ( fetch_data( a.id ) ) {
+            cout << "closest station w/ metar = " << a.id << endl;
+           _icao = a.id;
+            elapsed = 0.0;
+            update_env_config();
+            env->init();
+        } else {
+            // mark as no metar so it doesn't show up in subsequent
+            // searches.
+            cout << "no metar at metar = " << a.id << endl;
+            globals->get_airports()->no_metar( a.id );
+        }
+    }
     env->update(delta_time_sec);
 }
 
@@ -422,21 +446,18 @@ FGMetarEnvironmentCtrl::setEnvironment (FGEnvironment * environment)
     env->setEnvironment(environment);
 }
 
-void
-FGMetarEnvironmentCtrl::fetch_data (const char *icao)
+bool
+FGMetarEnvironmentCtrl::fetch_data (const string &icao)
 {
     char s[128];
     double d, dt;
     int i;
 
-    if ((icao == NULL) && (_icao == NULL)) {
-        _icao = strdup( fgGetString("/sim/presets/airport-id") );
+    if ((icao == "") && (_icao == "")) {
+        _icao = fgGetString("/sim/presets/airport-id");
 
-    } else if (icao != NULL) {
-        if (_icao != NULL)
-            free(_icao);
-
-        _icao = strdup(icao);
+    } else if (icao != "") {
+        _icao = icao;
     }
 
     // fetch station elevation if exists
@@ -446,11 +467,11 @@ FGMetarEnvironmentCtrl::fetch_data (const char *icao)
     // fetch current metar data
     SGMetar *m;
     try {
-        m = new SGMetar(_icao);
+        m = new SGMetar( _icao.c_str() );
     } catch (const sg_io_exception& e) {
         SG_LOG( SG_GENERAL, SG_WARN, "Error fetching live weather data: "
                                       << e.getFormattedMessage().c_str() );
-        return;
+        return false;
     }
 
     d = m->getMinVisibility().getVisibility_m();
@@ -557,6 +578,8 @@ FGMetarEnvironmentCtrl::fetch_data (const char *icao)
     }
 
     delete m;
+
+    return true;
 }
 
 

src/Environment/environment_ctrl.hxx

@@ -153,9 +153,12 @@ public:
 private:
     FGInterpolateEnvironmentCtrl *env;
 
-    char *_icao;
+    string _icao;
     float station_elevation_ft;
-    void fetch_data (const char *icao);
+    float update_interval_sec;
+    float elapsed;
+    bool fetch_data (const string &icao);
+    void update_env_config();
 };
 
 #endif // _ENVIRONMENT_CTRL_HXX