Ref T436, underflow detection for FSX

* utility functions
* force gnd flag to avoid underflow

src/blackcore/simulator.h

@@ -233,6 +233,9 @@ namespace BlackCore
         //! \sa ISimulator::callbackReceivedRequestedElevation
         virtual bool requestElevation(const BlackMisc::Geo::ICoordinateGeodetic &reference, const BlackMisc::Aviation::CCallsign &callsign) override;
 
+        //! \copydoc BlackMisc::Simulation::ISimulationEnvironmentProvider::requestElevation
+        bool requestElevation(const BlackMisc::Aviation::CAircraftSituation &situation) { return this->requestElevation(situation, situation.getCallsign()); }
+
         //! A requested elevation has been received
         //! \remark public for testing purposes
         virtual void callbackReceivedRequestedElevation(const BlackMisc::Geo::CElevationPlane &plane, const BlackMisc::Aviation::CCallsign &callsign);

src/blackmisc/aviation/aircraftsituation.cpp

@@ -149,6 +149,21 @@ namespace BlackMisc
             return unknown;
         }
 
+        bool CAircraftSituation::isCorrectedAltitude(CAircraftSituation::AltitudeCorrection correction)
+        {
+            switch (correction)
+            {
+            case Underflow:
+            case DraggedToGround:
+                return true;
+            case NoElevation:
+            case NoCorrection:
+            case AGL:
+            default: break;
+            }
+            return false;
+        }
+
         const QString &CAircraftSituation::gndElevationInfoToString(GndElevationInfo details)
         {
             static const QString noDetails("no details");

src/blackmisc/aviation/aircraftsituation.h

@@ -499,6 +499,9 @@ namespace BlackMisc
             //! Enum to string
             static const QString &altitudeCorrectionToString(AltitudeCorrection correction);
 
+            //! Means corrected altitude?
+            static bool isCorrectedAltitude(AltitudeCorrection correction);
+
             //! Enum to string
             static const QString &gndElevationInfoToString(GndElevationInfo details);
 

src/plugins/simulator/fsxcommon/simulatorfsxcommon.cpp

@@ -1400,6 +1400,7 @@ namespace BlackSimPlugin
             // reset timer
             m_simObjectTimer.start(AddPendingAircraftIntervalMs); // restart
 
+            // remove outdated objects
             const CSimConnectObjects outdatedAdded = m_simConnectObjects.removeOutdatedPendingAdded(CSimConnectObject::AllTypes);
             if (!outdatedAdded.isEmpty())
             {
@@ -1509,7 +1510,14 @@ namespace BlackSimPlugin
             // FSX/P3D adding
             bool adding = false; // will be added flag
             const SIMCONNECT_DATA_REQUEST_ID requestId = probe ? this->obtainRequestIdForSimObjTerrainProbe() : this->obtainRequestIdForSimObjAircraft();
-            const SIMCONNECT_DATA_INITPOSITION initialPosition = CSimulatorFsxCommon::aircraftSituationToFsxPosition(newRemoteAircraft.getSituation(), sendGround);
+
+            // under flow can cause a model not to be added
+            // FSX: underflow and NO(!) gnd flag can cause adding/remove issue
+            // P3D: underflow did not cause such issue
+            CStatusMessage underflowStatus;
+            const CAircraftSituation initialSituation = newRemoteAircraft.getSituation();
+            const SIMCONNECT_DATA_INITPOSITION initialPosition = CSimulatorFsxCommon::aircraftSituationToFsxPosition(initialSituation, sendGround, true, &underflowStatus);
+
             const QString modelString(newRemoteAircraft.getModelString());
             if (this->showDebugLogMessage()) { this->debugLogMessage(Q_FUNC_INFO, QString("CS: '%1' model: '%2' request: %3, init pos: %4").arg(callsign.toQString(), modelString).arg(requestId).arg(fsxPositionToString(initialPosition))); }
 
@@ -1519,6 +1527,11 @@ namespace BlackSimPlugin
                                SimConnect_AICreateSimulatedObject(m_hSimConnect, modelStringBa.constData(), initialPosition, requestId) :
                                SimConnect_AICreateNonATCAircraft(m_hSimConnect, modelStringBa.constData(), csBa.constData(), initialPosition, requestId);
 
+            if (!underflowStatus.isEmpty())
+            {
+                CStatusMessage(this).warning("Underflow detecion for '%1', details '%2'") << callsign.asString() << underflowStatus.getMessage();
+            }
+
             if (isFailure(hr))
             {
                 const CStatusMessage msg = CStatusMessage(this).error("SimConnect, can not create AI traffic: '%1' '%2'") << callsign.toQString() << modelString;
@@ -2013,13 +2026,18 @@ namespace BlackSimPlugin
             });
         }
 
-        SIMCONNECT_DATA_INITPOSITION CSimulatorFsxCommon::aircraftSituationToFsxPosition(const CAircraftSituation &situation, bool sendGnd)
+        SIMCONNECT_DATA_INITPOSITION CSimulatorFsxCommon::aircraftSituationToFsxPosition(const CAircraftSituation &situation, bool sendGnd, bool forceUnderflowDetection, CStatusMessage *details)
         {
             Q_ASSERT_X(!situation.isGeodeticHeightNull(), Q_FUNC_INFO, "Missing height (altitude)");
             Q_ASSERT_X(!situation.isPositionNull(), Q_FUNC_INFO,  "Missing position");
 
             // lat/Lng, NO PBH
+            CAircraftSituation::AltitudeCorrection altCorrection = CAircraftSituation::UnknownCorrection;
             SIMCONNECT_DATA_INITPOSITION position = CSimulatorFsxCommon::coordinateToFsxPosition(situation);
+            if (forceUnderflowDetection)
+            {
+                position.Altitude = situation.getCorrectedAltitude(true, &altCorrection).value(CLengthUnit::ft());
+            }
 
             // MSFS has inverted pitch and bank angles
             position.Pitch    = -situation.getPitch().value(CAngleUnit::deg());
@@ -2042,12 +2060,30 @@ namespace BlackSimPlugin
                 position.Airspeed = static_cast<DWORD>(qRound(gsKts));
             }
 
-            if (sendGnd && situation.isOnGroundInfoAvailable())
+            // send GND flag also when underflow detection is available
+            if ((sendGnd || forceUnderflowDetection) && situation.isOnGroundInfoAvailable())
             {
                 const bool onGround = (situation.getOnGround() == CAircraftSituation::OnGround);
                 position.OnGround = onGround ? 1U : 0U;
             }
 
+            // if we have no GND flag yet (gnd flag prevents underflow)
+            if (forceUnderflowDetection && position.OnGround == 0 && !CAircraftSituation::isCorrectedAltitude(altCorrection))
+            {
+                // logical resolution failed so far, likely we have no CG or elevantion
+                // primitive guessing
+                do
+                {
+                    if (position.Airspeed < 2)
+                    {
+                        position.OnGround = 1U;
+                        if (details) { *details = CStatusMessage(getLogCategories()).warning("Force GND flag for underflow protection"); }
+                        break;
+                    }
+                }
+                while (false);
+            }
+
             // crosscheck
             if (CBuildConfig::isLocalDeveloperDebugBuild())
             {

src/plugins/simulator/fsxcommon/simulatorfsxcommon.h

@@ -294,7 +294,9 @@ namespace BlackSimPlugin
 
             //! Format conversion
             //! \note must be valid situation
-            static SIMCONNECT_DATA_INITPOSITION aircraftSituationToFsxPosition(const BlackMisc::Aviation::CAircraftSituation &situation, bool sendGnd = true);
+            static SIMCONNECT_DATA_INITPOSITION aircraftSituationToFsxPosition(
+                const BlackMisc::Aviation::CAircraftSituation &situation, bool sendGnd = true,
+                bool forceUnderflowDetection = false, BlackMisc::CStatusMessage *details = nullptr);
 
             //! Format conversion
             //! \note must be valid situation