Added PropertyContainer::handleMissingProperty(...) and PropertyContainer::handleChangedPropertyType(...).

These are helper functions to simplify migrating older files.

src/App/PropertyContainer.cpp

@@ -152,6 +152,36 @@ const char* PropertyContainer::getPropertyName(const Property* prop)const
 const PropertyData * PropertyContainer::getPropertyDataPtr(void){return &propertyData;} 
 const PropertyData & PropertyContainer::getPropertyData(void) const{return propertyData;} 
 
+/**
+ * @brief PropertyContainer::handleMissingProperty is called during restore to possibly
+ * fix reading of older versions of this property container.
+ *
+ * The default implementation does nothing.
+ *
+ * @param reader The XML stream to read from.
+ * @param PropName Name of property on file that does not exist in the container anymore.
+ */
+
+void PropertyContainer::handleMissingProperty(XMLReader &reader, const char *PropName)
+{
+}
+
+/**
+ * @brief PropertyContainer::handleChangedPropertyType is called during restore to possibly
+ * fix reading of older versions of the property container. This method is typically called
+ * if the property on file has changed its type in more recent versions.
+ *
+ * The default implementation does nothing.
+ *
+ * @param reader The XML stream to read from.
+ * @param TypeName Name of property type on file.
+ * @param prop Pointer to property to restore. Its type differs from TypeName.
+ */
+
+void PropertyContainer::handleChangedPropertyType(XMLReader &reader, const char *TypeName, Property *prop)
+{
+}
+
 PropertyData PropertyContainer::propertyData;
 
 /**
@@ -234,8 +264,17 @@ void PropertyContainer::Restore(Base::XMLReader &reader)
         // not its name. In this case we would force to read-in a wrong property
         // type and the behaviour would be undefined.
         try {
-            if (prop && strcmp(prop->getTypeId().getName(), TypeName) == 0)
-                prop->Restore(reader);
+
+            // Property not found in container, but one file?
+            if (!prop)
+                handleMissingProperty(reader, PropName);
+            else {
+                // Has the type changed?
+                if (strcmp(prop->getTypeId().getName(), TypeName) != 0)
+                    handleChangedPropertyType(reader, TypeName, prop);
+                else
+                    prop->Restore(reader); // All as before
+            }
         }
         catch (const Base::XMLParseException&) {
             throw; // re-throw

src/App/PropertyContainer.h

@@ -196,6 +196,10 @@ protected:
   static const  PropertyData * getPropertyDataPtr(void); 
   virtual const PropertyData& getPropertyData(void) const; 
 
+  virtual void handleMissingProperty(Base::XMLReader &reader, const char *PropName);
+
+  virtual void handleChangedPropertyType(Base::XMLReader &reader, const char * TypeName, Property * prop);
+
 private:
   // forbidden
   PropertyContainer(const PropertyContainer&);