refactor: Move PBH interpolator to inidivdual Interpolants

This allows each interpolant to specify on its own which PBH
interpolator should be used. Currently only the linear PBH interpolator
is available, but another PBH interpolator will be added for velocity.

This removes some protected data from the IInterpolator interface as well,
which conforms to C++ Core Guideline C.113 ("Avoid protected data").

src/blackmisc/simulation/interpolant.h

@@ -17,9 +17,6 @@ namespace BlackMisc::Simulation
         //! "Real time" representing the interpolated situation
         qint64 getInterpolatedTime() const { return m_interpolatedTime; }
 
-        //! Interpolator for pitch, bank, heading, groundspeed
-        const CInterpolatorPbh &pbh() const { return m_pbh; }
-
         //! Situations available
         int getSituationsAvailable() const { return m_situationsAvailable; }
 
@@ -37,17 +34,16 @@ namespace BlackMisc::Simulation
 
     protected:
         //! Default ctor
-        IInterpolant() {}
+        IInterpolant() = default;
 
         //! Constructor
-        IInterpolant(int situationsAvailable, const CInterpolatorPbh &pbh) : m_situationsAvailable(situationsAvailable), m_pbh(pbh) {}
+        explicit IInterpolant(int situationsAvailable) : m_situationsAvailable(situationsAvailable) {}
 
         //! Constructor
         IInterpolant(qint64 interpolatedTime, int situationsAvailable) : m_interpolatedTime(interpolatedTime), m_situationsAvailable(situationsAvailable) {}
 
         qint64 m_interpolatedTime = -1; //!< "Real time "of interpolated situation
         int m_situationsAvailable = 0; //!< used situations
-        CInterpolatorPbh m_pbh; //!< the used PBH interpolator
         bool m_valid = true; //!< valid?
         bool m_recalculated = false; //!< recalculated interpolant
     };

src/blackmisc/simulation/interpolator.cpp

@@ -245,12 +245,12 @@ namespace BlackMisc::Simulation
         do
         {
             if (!isValidInterpolant) { break; }
-            const CInterpolatorPbh pbh = interpolant.pbh();
 
             // init interpolated situation
             currentSituation = this->initInterpolatedSituation(pbh.getStartSituation(), pbh.getEndSituation());
 
             // Pitch bank heading first, so follow up steps could use those values
+            const auto pbh = interpolant.pbh();
             currentSituation.setHeading(pbh.getHeading());
             currentSituation.setPitch(pbh.getPitch());
             currentSituation.setBank(pbh.getBank());

src/blackmisc/simulation/interpolatorlinear.cpp

@@ -23,12 +23,12 @@ using namespace BlackMisc::Simulation;
 
 namespace BlackMisc::Simulation
 {
-    CInterpolatorLinear::CInterpolant::CInterpolant(const CAircraftSituation &startSituation) : IInterpolant(1, CInterpolatorPbh(0, startSituation, startSituation)),
+    CInterpolatorLinear::CInterpolant::CInterpolant(const CAircraftSituation &startSituation) : IInterpolant(1),
-                                                                                                m_startSituation(startSituation)
+                                                                                                m_startSituation(startSituation), m_pbh(0, startSituation, startSituation)
     {}
 
-    CInterpolatorLinear::CInterpolant::CInterpolant(const CAircraftSituation &startSituation, const CInterpolatorPbh &pbh) : IInterpolant(1, pbh),
+    CInterpolatorLinear::CInterpolant::CInterpolant(const CAircraftSituation &startSituation, const CInterpolatorPbh &pbh) : IInterpolant(1),
-                                                                                                                             m_startSituation(startSituation)
+                                                                                                                             m_startSituation(startSituation), m_pbh(pbh)
     {}
 
     CInterpolatorLinear::CInterpolant::CInterpolant(const CAircraftSituation &startSituation, const CAircraftSituation &endSituation, double timeFraction, qint64 interpolatedTime) : IInterpolant(interpolatedTime, 2),

src/blackmisc/simulation/interpolatorlinear.h

@@ -60,10 +60,13 @@ namespace BlackMisc
                 //! End situation
                 const Aviation::CAircraftSituation &getEndSituation() const { return m_endSituation; }
 
+                CInterpolatorPbh pbh() const { return m_pbh; }
+
             private:
                 Aviation::CAircraftSituation m_startSituation;
                 Aviation::CAircraftSituation m_endSituation;
                 double m_simulationTimeFraction = 0.0; //!< 0..1
+                CInterpolatorPbh m_pbh;
             };
 
             //! Get the interpolant for the given time point

src/blackmisc/simulation/interpolatorspline.h

@@ -77,10 +77,13 @@ namespace BlackMisc::Simulation
             //! \private UNIT tests/ASSERT only
             const PosArray &getPa() const { return m_pa; }
 
+            CInterpolatorPbh pbh() const { return m_pbh; }
+
         private:
             PosArray m_pa; //!< current positions array, latest values last
             PhysicalQuantities::CLengthUnit m_altitudeUnit;
             qint64 m_currentTimeMsSinceEpoc { -1 };
+            CInterpolatorPbh m_pbh; //!< the used PBH interpolator
         };
 
         //! Strategy used by CInterpolator::getInterpolatedSituation