Bugfix: characteristics could not be overwritten in kart.xml files.

First part of #2560.

src/karts/abstract_characteristic.hpp

@@ -227,6 +227,7 @@ public:
 public:
     AbstractCharacteristic();
     virtual ~AbstractCharacteristic() {}
+    virtual void copyFrom(const AbstractCharacteristic *other) = 0;
 
     /**
      * The process function is the core of this characteristics system.

src/karts/cached_characteristic.hpp

@@ -21,6 +21,8 @@
 
 #include "karts/abstract_characteristic.hpp"
 
+#include <assert.h>
+
 class CachedCharacteristic : public AbstractCharacteristic
 {
 private:
@@ -46,7 +48,7 @@ public:
 
     /** Fetches all cached values from the original source. */
     void updateSource();
-
+    virtual void copyFrom(const AbstractCharacteristic *other) { assert(false); }
     virtual void process(CharacteristicType type, Value value, bool *is_set) const;
 };
 

src/karts/combined_characteristic.hpp

@@ -21,6 +21,8 @@
 
 #include "karts/abstract_characteristic.hpp"
 
+#include <assert.h>
+
 class CombinedCharacteristic : public AbstractCharacteristic
 {
 private:
@@ -32,6 +34,10 @@ public:
     void addCharacteristic(const AbstractCharacteristic *characteristic);
 
     virtual void process(CharacteristicType type, Value value, bool *is_set) const;
+    virtual void copyFrom(const AbstractCharacteristic *other)
+    {
+        assert(false);
+    }
 };
 
 #endif

src/karts/kart_properties.cpp

@@ -125,8 +125,10 @@ void KartProperties::copyForPlayer(const KartProperties *source)
     // So all pointer variables need to be separately allocated and assigned.
     if (source->m_characteristic)
     {
+        // Remove the shared reference by creating a new pointer
         m_characteristic.reset(new XmlCharacteristic());
-        *m_characteristic = *source->m_characteristic;
+        m_characteristic->copyFrom(source->getCharacteristic());
+
         // Combine the characteristics for this object. We can't copy it because
         // this object has other pointers (to m_characteristic).
         combineCharacteristics();

src/karts/xml_characteristic.cpp

@@ -31,6 +31,17 @@ XmlCharacteristic::XmlCharacteristic(const XMLNode *node) :
         load(node);
 }   // XmlCharacteristic constructor
 
+// ----------------------------------------------------------------------------
+/** Copies the characteristics from the specified other characteristic class
+ *  into this class.
+ */
+void XmlCharacteristic::copyFrom(const AbstractCharacteristic *other)
+{
+    const XmlCharacteristic *xc = dynamic_cast<const XmlCharacteristic*>(other);
+    assert(xc!=NULL);
+    m_values = xc->m_values;
+}   // operator=
+
 // ----------------------------------------------------------------------------
 /** process will execute the operation that is specified in the saved string.
  *  The format of the operations is specified in kart_characteristics.xml.

src/karts/xml_characteristic.hpp

@@ -37,6 +37,7 @@ public:
     virtual void process(CharacteristicType type, Value value, bool *is_set) const;
 
     void load(const XMLNode *node);
+    virtual void copyFrom(const AbstractCharacteristic *other);
 
 private:
     static void processFloat(const std::string &processor, float *value, bool *is_set);