Added implementation of level of details per layer and item type pairs basis (items on every layer have a possibility to define the minimum VIEW scale to be shown).

common/view/view.cpp

@@ -459,7 +459,8 @@ struct VIEW::drawItem
             // Draw using cached information or create one
             int group = aItem->getGroup( currentLayer->id );
 
-            if( group >= 0 && aItem->ViewIsVisible() )
+            if( group >= 0 && aItem->ViewIsVisible() &&
+                aItem->ViewGetLOD( currentLayer->id ) < view->m_scale )
             {
                 gal->DrawGroup( group );
             }
@@ -471,7 +472,8 @@ struct VIEW::drawItem
                 gal->EndGroup();
             }
         }
-        else if( aItem->ViewIsVisible() )
+        else if( aItem->ViewIsVisible() &&
+                 aItem->ViewGetLOD( currentLayer->id ) < view->m_scale )
         {
             // Immediate mode
             view->m_painter->Draw( aItem, currentLayer->id );

include/view/view_item.h

@@ -227,6 +227,17 @@ public:
         return m_viewVisible;
     }
 
+    /**
+     * Function ViewGetLOD()
+     * Returns the level of detail of the item. A level of detail is the minimal VIEW scale that
+     * is sufficient for an item to be shown on a given layer.
+     */
+    virtual unsigned int ViewGetLOD( int aLayer ) const
+    {
+        // By default always show the item
+        return 0;
+    }
+
     /**
      * Function ViewUpdate()
      * For dynamic VIEWs, informs the associated VIEW that the graphical representation of