Automatic merge of T1.6-rc3-30-gdf7bf1a26 and 12 pull requests

- Pull request #1104 at c039a26: Handle simple adhesion within the axle module
- Pull request #1057 at 1c2bcb4: Switchable brake system
- Pull request #1086 at e10390b: Add Settings Exporter tool (copy settings to INI, etc)
- Pull request #1091 at 4484282: Automatic speed control
- Pull request #1110 at 387388e: Fix Activity Runner persists after loading exception
- Pull request #1115 at 270f22f: Do not activate ETS switch if no suitable cars are attached
- Pull request #1121 at 91d2d26: Manually Override Articulation
- Pull request #1123 at dc286f5: Handle null control active locomotive
- Pull request #1125 at 7a4f055: Lift #1096 into 1.6 release
- Pull request #1082 at 5845a1a: Allow variable water level in glass gauge
- Pull request #1081 at 689494b: Brake cuts power unification
- Pull request #1124 at fab5457: Built-in PBL2 brake controller

Author: openrails-bot

Source/Documentation/Manual/features-rollingstock.rst

@@ -2124,8 +2124,15 @@ or::
       ORTSEngineBrakeController ( "YourBrakes.cs" )
   )
 
-The .cs extension is optional. "MSTS" loads the default MSTS-compatible 
-implementation, so do `not` use this name for your own script.
+The .cs extension is optional. Alternatively, there are several built-in
+brake controllers:
+- "MSTS": default implementation for a notched brake controller. Each notch
+  behaves as defined in the :ref:`Train Brake Controller Positions <physics-brake-controller>` section.
+- "PBL2": a brake controller widely used in Europe. It has a stable Hold position which keeps brake
+  pipe pressure, and two unstable positions that apply or release the brakes when pressed. The controller
+  also generates the electrical Release and Apply signals required for the UIC EP brake.
+
+Do `not` use these names for your own script.
 
 .. _features-scripting-cb:
 

Source/Orts.Simulation/Common/Scripting/BrakeController.cs

@@ -197,7 +197,7 @@ public float IntermediateValue
         public List<MSTSNotch> Notches() => Host.Notches;
 
         /// <summary>
-        /// Fraction of train brake demanded by cruise control
+        /// Fraction of train brake demanded by cruise control. Returns -1 if CC is inactive
         /// </summary>
         public float CruiseControlBrakeDemand() => Host.CruiseControlBrakeDemand;
 

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/Controllers/BrakeController.cs

@@ -180,9 +180,9 @@ public float CruiseControlBrakeDemand
         { 
             get
             {
-                if (Locomotive.CruiseControl == null) return 0;
-                if (this == Locomotive.EngineBrakeController) return Locomotive.CruiseControl.EngineBrakePercent / 100;
-                else return Locomotive.CruiseControl.TrainBrakePercent / 100;
+                if (Locomotive.CruiseControl == null) return -1;
+                if (this == Locomotive.EngineBrakeController) return Locomotive.CruiseControl.EngineBrakePercent / 100 ?? -1;
+                else return Locomotive.CruiseControl.TrainBrakePercent / 100 ?? -1;
             }
         }
         InterpolatorDiesel2D DynamicBrakeBlendingTable;

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/CruiseControl.cs

@@ -117,8 +117,8 @@ public float SetSpeedKpHOrMpH
         public float MaxDecelerationMpSS = 2;
         public float? ThrottlePercent { get; private set;}
         public float? DynamicBrakePercent { get; private set;}
-        public float TrainBrakePercent { get; private set; }
-        public float EngineBrakePercent { get; private set; }
+        public float? TrainBrakePercent { get; private set; }
+        public float? EngineBrakePercent { get; private set; }
         protected float trainLength = 0;
         public int TrainLengthMeters = 0;
         OdoMeter RestrictedRegionOdometer;
@@ -588,8 +588,8 @@ public void Update(float elapsedClockSeconds)
                 CCThrottleOrDynBrakePercent = 0;
                 ThrottlePercent = null;
                 DynamicBrakePercent = null;
-                TrainBrakePercent = 0;
-                EngineBrakePercent = 0;
+                TrainBrakePercent = null;
+                EngineBrakePercent = null;
                 return;
             }
             if (firstIteration) // if this is executed the first time, let's check all other than player engines in the consist, and record them for further throttle manipulation
@@ -643,8 +643,8 @@ public void Update(float elapsedClockSeconds)
                 CCThrottleOrDynBrakePercent = 0;
                 ThrottlePercent = null;
                 DynamicBrakePercent = null;
-                TrainBrakePercent = 0;
-                EngineBrakePercent = 0;
+                TrainBrakePercent = null;
+                EngineBrakePercent = null;
             }
             else if (SpeedRegMode == SpeedRegulatorMode.Auto)
             {
@@ -755,14 +755,14 @@ public void Update(float elapsedClockSeconds)
                     if (CCThrottleOrDynBrakePercent > 0 && !tractionAllowed) CCThrottleOrDynBrakePercent = 0;
                     if (AbsWheelSpeedMpS == 0 && CCThrottleOrDynBrakePercent < 0) CCThrottleOrDynBrakePercent = 0;
                     CCThrottleOrDynBrakePercent = MathHelper.Clamp(CCThrottleOrDynBrakePercent, -100, 100);
-                    TrainBrakePercent = MathHelper.Clamp(TrainBrakePercent, 0, 100);
+                    TrainBrakePercent = MathHelper.Clamp(TrainBrakePercent.Value, 0, 100);
 
                     if (TrainBrakePercent > 0) CCIsUsingTrainBrake = true;
                 }
                 else
                 {
                         CCThrottleOrDynBrakePercent = 0;
-                    TrainBrakePercent = 0;
+                    TrainBrakePercent = null;
                     ThrottlePID.Active = false;
                     DynamicBrakePID.Active = false;
                     TrainBrakePID.Active = false;
@@ -772,7 +772,8 @@ public void Update(float elapsedClockSeconds)
                 if (DynamicBrakePriority) DynamicBrakePercent = null;
                 else if (CCThrottleOrDynBrakePercent < 0) DynamicBrakePercent = -CCThrottleOrDynBrakePercent;
                 else DynamicBrakePercent = -1;
-                if (SpeedSelMode == SpeedSelectorMode.Parking && !EngineBrakePriority)
+                if (EngineBrakePriority) EngineBrakePercent = null;
+                else if (SpeedSelMode == SpeedSelectorMode.Parking)
                 {
                     if (Locomotive.AbsWheelSpeedMpS <= ParkingBrakeEngageSpeedMpS)
                         EngineBrakePercent = ParkingBrakePercent;
@@ -1380,14 +1381,16 @@ void UpdateTrainBrakePercent(float elapsedClockSeconds, float demandedAccelerati
 
             float target = TrainBrakePID.Percent;
 
+            if (TrainBrakePercent == null) TrainBrakePercent = 0;
+
             if (target > TrainBrakePercent && target >= TrainBrakeMinPercentValue)
             {
                 if (TrainBrakePercent < TrainBrakeMinPercentValue) TrainBrakePercent = TrainBrakeMinPercentValue;
-                TrainBrakePercent = Math.Min(target, TrainBrakePercent + 100 / TrainBrakeFullRangeIncreaseTimeSeconds * elapsedClockSeconds);
+                TrainBrakePercent = Math.Min(target, TrainBrakePercent.Value + 100 / TrainBrakeFullRangeIncreaseTimeSeconds * elapsedClockSeconds);
             }
             else if (target < TrainBrakePercent)
             {
-                TrainBrakePercent = Math.Max(target, TrainBrakePercent - 100 / TrainBrakeFullRangeDecreaseTimeSeconds * elapsedClockSeconds);
+                TrainBrakePercent = Math.Max(target, TrainBrakePercent.Value - 100 / TrainBrakeFullRangeDecreaseTimeSeconds * elapsedClockSeconds);
                 if (TrainBrakePercent <= TrainBrakeMinPercentValue)
                 {
                     if (target == 0) TrainBrakePercent = 0;