Reduce SessionItem signaling

• reduce SessionItem signaling regarding sample items
• cleanup/simplify code
• fix warning

GUI/Model/Sample/ParticleLayoutItem.h

@@ -34,7 +34,19 @@ public:
 
     ParticleLayoutItem();
 
-    DoubleDescriptor totalDensity() const;
+    //! The density value which belonging only to the layout.
+    //!
+    //! This is the editable value. If an interference is present, this value may not be the one to
+    //! be used for building the domain layout or to be presented. For the correct value-to-use,
+    //! whether an interference is present or not, use totalDensity().
+    DoubleDescriptor ownDensity() const;
+
+    //! The real density.
+    //!
+    //! Returns ownDensity() if the interference is not influencing the density. If the
+    //! interference is defining the density, this is the interference-calculated density.
+    double totalDensity() const;
+
     DoubleDescriptor weight() const;
 
     QVector<ItemWithParticles*> particles() const;
@@ -46,10 +58,14 @@ public:
     void setInterference(InterferenceItem* interference);
     void removeInterference();
 
-    void updateDensityValue();
+    // #baMigration Use only while not migrated from SessionModel!
+    void enableDensity(bool b);
 
-private:
-    void updateDensityAppearance();
+    //! Returns whether total density is defined by the currently selected interference.
+    //!
+    //! Two dimensional interference calculates density automatically; in these cases the "own"
+    //! total density value should not be edited but set by the one from the interference.
+    bool totalDensityIsDefinedByInterference() const;
 };
 
 template <typename T> T* ParticleLayoutItem::createInterference()