updateTrainPositions() when stopping train, go all the way to stop position.

It can happen that stopping point lays between current position and
next tick position. Trains previously stoppet at their current position,
so just before stop point.
How much before depends on tick granularity and train speed, the bigger
the tick step, the bigger the gap to stop point.

Now instead when stop is requested, the exact amount left to travel is
returned and a second custom tick routine is executed.

Author: gfgit

shared/src/traintastic/simulator/simulator.cpp

@@ -941,43 +941,60 @@ void Simulator::updateTrainPositions()
       trainState.speedOrDirectionChanged = false;
     }
 
-    auto updateHelper = [this](Simulator::Train::VehicleItem& item, float speed, bool reverse) -> bool
+    auto updateHelper = [this](Simulator::Train::VehicleItem& item, float speed,
+                               bool reverse, float &outRemaining) -> bool
     {
       if(reverse)
         speed = -speed;
 
       if(item.reversed == reverse)
-        return updateVehiclePosition(item.vehicle->state.front, speed) &&
-            updateVehiclePosition(item.vehicle->state.rear, speed);
+        return updateVehiclePosition(item.vehicle->state.front, speed, outRemaining) &&
+            updateVehiclePosition(item.vehicle->state.rear, speed, outRemaining);
       else
-        return updateVehiclePosition(item.vehicle->state.rear, speed) &&
-            updateVehiclePosition(item.vehicle->state.front, speed);
+        return updateVehiclePosition(item.vehicle->state.rear, speed, outRemaining) &&
+            updateVehiclePosition(item.vehicle->state.front, speed, outRemaining);
     };
 
     const float speed = m_stateData.powerOn ? trainState.speed : 0.0f;
 
-    if(!trainState.reverse)
+    float outRemaining = 0.0f;
+
+    do
     {
-      for(auto& vehicleItem : train->vehicles)
+      float tickPosDelta = speed;
+      if(outRemaining > 0.0f && speed != 0.0f)
+      {
+        // This is second round, travel just remaining distance to stop
+        if(speed > 0.0f)
+          tickPosDelta = outRemaining;
+        else
+          tickPosDelta = outRemaining;
+      }
+
+      if(!trainState.reverse)
       {
-        if(!updateHelper(vehicleItem, speed, trainState.reverse))
+        for(auto& vehicleItem : train->vehicles)
         {
-          setTrainSpeed(train, 0.0f);
-          break;
+          if(!updateHelper(vehicleItem, tickPosDelta, trainState.reverse, outRemaining))
+          {
+            setTrainSpeed(train, 0.0f);
+            break;
+          }
         }
       }
-    }
-    else // reverse
-    {
-      for(auto& vehicleItem : train->vehicles | std::views::reverse)
+      else // reverse
       {
-        if(!updateHelper(vehicleItem, speed, trainState.reverse))
+        for(auto& vehicleItem : train->vehicles | std::views::reverse)
         {
-          setTrainSpeed(train, 0.0f);
-          break;
+          if(!updateHelper(vehicleItem, tickPosDelta, trainState.reverse, outRemaining))
+          {
+            setTrainSpeed(train, 0.0f);
+            break;
+          }
         }
       }
     }
+    while(outRemaining > 0.0f && speed != 0.0f);
   }
 }
 
@@ -1004,8 +1021,10 @@ inline bool isTurnoutUnknownState(const Simulator::TrackSegment& segment,
   return false;
 }
 
-bool Simulator::updateVehiclePosition(VehicleState::Face& face, const float speed)
+bool Simulator::updateVehiclePosition(VehicleState::Face& face, const float speed, float &outRemaining)
 {
+  outRemaining = 0.0f;
+
   float distance = face.distance + (face.segmentDirectionInverted ? -speed : speed);
 
   // Move to next segment when reaching the end:
@@ -1015,18 +1034,26 @@ bool Simulator::updateVehiclePosition(VehicleState::Face& face, const float spee
     const auto& segment = staticData.trackSegments[face.segmentIndex];
     const auto segmentLength = getSegmentLength(segment, m_stateData);
 
-    if(distance >= segmentLength)
+    // If train is right on the end of segment (distance == segmentLenght) do not update
+    // unlsess we are effectively moving. Because if speed is 0, segmentDirectionInverted is
+    // not calculated correctly and because in case of 2 segment touching by their side 1,
+    // it will infinitely jump vehicle face from one to another.
+    if(distance > segmentLength || (distance == segmentLength && speed != 0))
     {
       const auto nextSegmentIndex = getNextSegmentIndex(segment, true, m_stateData);
       if(nextSegmentIndex == invalidIndex)
       {
+        outRemaining = segmentLength - face.distance - 0.0001;
         return false; // no next segment
       }
 
       auto& nextSegment = staticData.trackSegments[nextSegmentIndex];
 
       if(isTurnoutUnknownState(nextSegment, m_stateData))
+      {
+        outRemaining = segmentLength - face.distance - 0.0001;
         return false;
+      }
 
       if(segment.sensor.index != invalidIndex)
       {
@@ -1058,13 +1085,17 @@ bool Simulator::updateVehiclePosition(VehicleState::Face& face, const float spee
       const auto nextSegmentIndex = getNextSegmentIndex(segment, false, m_stateData);
       if(nextSegmentIndex == invalidIndex)
       {
+        outRemaining = face.distance;
         return false; // no next segment
       }
 
       auto& nextSegment = staticData.trackSegments[nextSegmentIndex];
 
       if(isTurnoutUnknownState(nextSegment, m_stateData))
+      {
+        outRemaining = face.distance;
         return false;
+      }
 
       if(segment.sensor.index != invalidIndex)
       {

shared/src/traintastic/simulator/simulator.hpp

@@ -340,7 +340,7 @@ class Simulator : public std::enable_shared_from_this<Simulator>
   void handShake();
 
   void updateTrainPositions();
-  bool updateVehiclePosition(VehicleState::Face& face, const float speed);
+  bool updateVehiclePosition(VehicleState::Face& face, const float speed, float &outRemaining);
   void updateSensors();
 
   bool isStraight(const TrackSegment& segment);