Introduce scale-based filtering of legend nodes (in WMS)

Author: wonder-sk

src/core/layertree/qgslayertreemodel.cpp

@@ -43,9 +43,10 @@ QgsLayerTreeModel::QgsLayerTreeModel( QgsLayerTreeGroup* rootNode, QObject *pare
 
 QgsLayerTreeModel::~QgsLayerTreeModel()
 {
-  foreach ( QList<QgsLayerTreeModelLegendNode*> nodeL, mSymbologyNodes )
+  foreach ( QList<QgsLayerTreeModelLegendNode*> nodeL, mOriginalSymbologyNodes )
     qDeleteAll( nodeL );
-  mSymbologyNodes.clear();
+  mOriginalSymbologyNodes.clear();
+  mSymbologyNodes.clear(); // does not own the nodes
 }
 
 QgsLayerTreeNode* QgsLayerTreeModel::index2node( const QModelIndex& index ) const
@@ -458,6 +459,7 @@ void QgsLayerTreeModel::setRootGroup( QgsLayerTreeGroup* newRootGroup )
   disconnectFromRootNode();
 
   Q_ASSERT( mSymbologyNodes.isEmpty() );
+  Q_ASSERT( mOriginalSymbologyNodes.isEmpty() );
 
   mRootNode = newRootGroup;
 
@@ -541,6 +543,16 @@ QFont QgsLayerTreeModel::layerTreeNodeFont( int nodeType ) const
   }
 }
 
+void QgsLayerTreeModel::setLegendFilterByScale( double scaleDenominator )
+{
+  mLegendFilterByScale = scaleDenominator;
+
+  // this could be later done in more efficient way
+  // by just updating active legend nodes, without refreshing original legend nodes
+  foreach ( QgsLayerTreeLayer* nodeLayer, mRootNode->findLayers() )
+    refreshLayerSymbology( nodeLayer );
+}
+
 void QgsLayerTreeModel::nodeWillAddChildren( QgsLayerTreeNode* node, int indexFrom, int indexTo )
 {
   Q_ASSERT( node );
@@ -664,7 +676,8 @@ void QgsLayerTreeModel::removeSymbologyFromLayer( QgsLayerTreeLayer* nodeLayer )
 {
   if ( mSymbologyNodes.contains( nodeLayer ) )
   {
-    qDeleteAll( mSymbologyNodes[nodeLayer] );
+    qDeleteAll( mOriginalSymbologyNodes[nodeLayer] );
+    mOriginalSymbologyNodes.remove( nodeLayer );
     mSymbologyNodes.remove( nodeLayer );
   }
 }
@@ -681,12 +694,15 @@ void QgsLayerTreeModel::addSymbologyToLayer( QgsLayerTreeLayer* nodeL )
 
   QList<QgsLayerTreeModelLegendNode*> lstNew = layerLegend->createLayerTreeModelLegendNodes( nodeL );
 
-  beginInsertRows( node2index( nodeL ), 0, lstNew.count() - 1 );
+  QList<QgsLayerTreeModelLegendNode*> filteredLstNew = filterLegendNodes( lstNew );
+
+  beginInsertRows( node2index( nodeL ), 0, filteredLstNew.count() - 1 );
 
   foreach ( QgsLayerTreeModelLegendNode* n, lstNew )
     n->setParent( nodeL );
 
-  mSymbologyNodes[nodeL] = lstNew;
+  mOriginalSymbologyNodes[nodeL] = lstNew;
+  mSymbologyNodes[nodeL] = filteredLstNew;
 
   endInsertRows();
 }
@@ -954,3 +970,16 @@ const QIcon& QgsLayerTreeModel::iconGroup()
 
   return icon;
 }
+
+QList<QgsLayerTreeModelLegendNode*> QgsLayerTreeModel::filterLegendNodes( const QList<QgsLayerTreeModelLegendNode*>& nodes )
+{
+  QList<QgsLayerTreeModelLegendNode*> filtered;
+  foreach ( QgsLayerTreeModelLegendNode* node, nodes )
+  {
+    if ( mLegendFilterByScale > 0 && !node->isScaleOK( mLegendFilterByScale ) )
+      continue;
+
+    filtered << node;
+  }
+  return filtered;
+}

src/core/layertree/qgslayertreemodel.h

@@ -137,6 +137,12 @@ class CORE_EXPORT QgsLayerTreeModel : public QAbstractItemModel
     //! Return at what number of symbology nodes the layer node should be collapsed. -1 means no auto-collapse (default).
     int autoCollapseSymbologyNodes() const { return mAutoCollapseSymNodesCount; }
 
+    //! Force only display of legend nodes which are valid for given scale denominator.
+    //! Setting value <= 0 will disable the functionality
+    //! @note added in 2.6
+    void setLegendFilterByScale( double scaleDenominator );
+    double legendFilterByScale() const { return mLegendFilterByScale; }
+
   signals:
 
   protected slots:
@@ -172,20 +178,30 @@ class CORE_EXPORT QgsLayerTreeModel : public QAbstractItemModel
 
     static const QIcon& iconGroup();
 
+    //! Filter nodes from QgsMapLayerLegend according to the current filtering rules
+    QList<QgsLayerTreeModelLegendNode*> filterLegendNodes( const QList<QgsLayerTreeModelLegendNode*>& nodes );
+
   protected:
     //! Pointer to the root node of the layer tree. Not owned by the model
     QgsLayerTreeGroup* mRootNode;
     //! Set of flags for the model
     Flags mFlags;
-    //! Data structure for storage of symbology nodes for each layer
+    //! Active symbology nodes for each layer node. May have been filtered.
+    //! Owner of legend nodes is still mOriginalSymbologyNodes !
     QMap<QgsLayerTreeLayer*, QList<QgsLayerTreeModelLegendNode*> > mSymbologyNodes;
+    //! Data structure for storage of symbology nodes for each layer.
+    //! These are nodes as received from QgsMapLayerLegend
+    QMap<QgsLayerTreeLayer*, QList<QgsLayerTreeModelLegendNode*> > mOriginalSymbologyNodes;
     //! Current index - will be underlined
     QPersistentModelIndex mCurrentIndex;
     //! Minimal number of nodes when symbology should be automatically collapsed. -1 = disabled
     int mAutoCollapseSymNodesCount;
 
     QFont mFontLayer;
     QFont mFontGroup;
+
+    //! scale denominator for filtering of legend nodes (<= 0 means no filtering)
+    double mLegendFilterByScale;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS( QgsLayerTreeModel::Flags )

src/core/layertree/qgslayertreemodellegendnode.h

@@ -58,6 +58,8 @@ class CORE_EXPORT QgsLayerTreeModelLegendNode : public QObject
     virtual QString userLabel() const { return mUserLabel; }
     virtual void setUserLabel( const QString& userLabel ) { mUserLabel = userLabel; }
 
+    virtual bool isScaleOK( double scale ) const { Q_UNUSED( scale ); return true; }
+
     struct ItemContext
     {
       //! Painter
@@ -133,6 +135,8 @@ class CORE_EXPORT QgsSymbolV2LegendNode : public QgsLayerTreeModelLegendNode
 
     void setUserLabel( const QString& userLabel ) { mUserLabel = userLabel; updateLabel(); }
 
+    virtual bool isScaleOK( double scale ) const { return mItem.isScaleOK( scale ); }
+
   private:
     void updateLabel();
 

src/mapserver/qgswmsserver.cpp

@@ -619,9 +619,8 @@ QImage* QgsWMSServer::getLegendGraphics()
 
   QList<QgsLayerTreeNode*> rootChildren = rootGroup.children();
 
-  // TODO: scale
-  //if ( scaleDenominator > 0 )
-  //  legendModel.setLegendFilterByScale( scaleDenominator );
+  if ( scaleDenominator > 0 )
+    legendModel.setLegendFilterByScale( scaleDenominator );
 
   // find out DPI
   QImage* tmpImage = createImage( 1, 1 );