Layer tree model support replacement of layer tree + layer node handl…

…es removal of layer cleanly

python/core/layertree/qgslayertreemodellegendnode.sip

@@ -67,7 +67,7 @@ class QgsSimpleLegendNode : QgsLayerTreeModelLegendNode
 #include <qgslayertreemodellegendnode.h>
 %End
   public:
-    QgsSimpleLegendNode( QgsLayerTreeLayer* nodeLayer, const QString& label, const QIcon& icon = QIcon() );
+    QgsSimpleLegendNode( QgsLayerTreeLayer* nodeLayer, const QString& label, const QString& id, const QIcon& icon = QIcon() );
 
     virtual QVariant data( int role ) const;
 };

src/core/layertree/qgslayertreelayer.cpp

@@ -57,6 +57,8 @@ void QgsLayerTreeLayer::attachToLayer()
   {
     mLayer = l;
     mLayerName = l->name();
+    // make sure we are notified if the layer is removed
+    connect( QgsMapLayerRegistry::instance(), SIGNAL( layersWillBeRemoved( QStringList ) ), this, SLOT( registryLayersWillBeRemoved( QStringList ) ) );
   }
   else
   {
@@ -153,3 +155,17 @@ void QgsLayerTreeLayer::registryLayersAdded( QList<QgsMapLayer*> layers )
     }
   }
 }
+
+void QgsLayerTreeLayer::registryLayersWillBeRemoved( const QStringList& layerIds )
+{
+  if ( layerIds.contains( mLayerId ) )
+  {
+    emit layerWillBeUnloaded();
+
+    // stop listening to removal signals and start hoping that the layer may be added again
+    disconnect( QgsMapLayerRegistry::instance(), SIGNAL( layersWillBeRemoved( QStringList ) ), this, SLOT( registryLayersWillBeRemoved( QStringList ) ) );
+    connect( QgsMapLayerRegistry::instance(), SIGNAL( layersAdded( QList<QgsMapLayer*> ) ), this, SLOT( registryLayersAdded( QList<QgsMapLayer*> ) ) );
+
+    mLayer = 0;
+  }
+}

src/core/layertree/qgslayertreelayer.h

@@ -66,10 +66,14 @@ class CORE_EXPORT QgsLayerTreeLayer : public QgsLayerTreeNode
 
   protected slots:
     void registryLayersAdded( QList<QgsMapLayer*> layers );
+    void registryLayersWillBeRemoved( const QStringList& layerIds );
 
   signals:
     //! emitted when a previously unavailable layer got loaded
     void layerLoaded();
+    //! emitted when a previously available layer got unloaded (from layer registry)
+    //! @note added in 2.6
+    void layerWillBeUnloaded();
 
   protected:
     void attachToLayer();

src/core/layertree/qgslayertreemodel.cpp

@@ -36,19 +36,9 @@ QgsLayerTreeModel::QgsLayerTreeModel( QgsLayerTreeGroup* rootNode, QObject *pare
     , mFlags( ShowSymbology | AllowSymbologyChangeState )
     , mAutoCollapseSymNodesCount( -1 )
 {
-  Q_ASSERT( mRootNode );
-
-  connect( mRootNode, SIGNAL( willAddChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeWillAddChildren( QgsLayerTreeNode*, int, int ) ) );
-  connect( mRootNode, SIGNAL( addedChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeAddedChildren( QgsLayerTreeNode*, int, int ) ) );
-  connect( mRootNode, SIGNAL( willRemoveChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeWillRemoveChildren( QgsLayerTreeNode*, int, int ) ) );
-  connect( mRootNode, SIGNAL( removedChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeRemovedChildren() ) );
-  connect( mRootNode, SIGNAL( visibilityChanged( QgsLayerTreeNode*, Qt::CheckState ) ), this, SLOT( nodeVisibilityChanged( QgsLayerTreeNode* ) ) );
-
-  connect( mRootNode, SIGNAL( customPropertyChanged( QgsLayerTreeNode*, QString ) ), this, SLOT( nodeCustomPropertyChanged( QgsLayerTreeNode*, QString ) ) );
+  connectToRootNode();
 
   mFontLayer.setBold( true );
-
-  connectToLayers( mRootNode );
 }
 
 QgsLayerTreeModel::~QgsLayerTreeModel()
@@ -461,6 +451,21 @@ QgsLayerTreeGroup*QgsLayerTreeModel::rootGroup()
   return mRootNode;
 }
 
+void QgsLayerTreeModel::setRootGroup( QgsLayerTreeGroup* newRootGroup )
+{
+  beginResetModel();
+
+  disconnectFromRootNode();
+
+  Q_ASSERT( mSymbologyNodes.isEmpty() );
+
+  mRootNode = newRootGroup;
+
+  connectToRootNode();
+
+  endResetModel();
+}
+
 void QgsLayerTreeModel::refreshLayerSymbology( QgsLayerTreeLayer* nodeLayer )
 {
   // update title
@@ -609,6 +614,18 @@ void QgsLayerTreeModel::nodeLayerLoaded()
   connectToLayer( nodeLayer );
 }
 
+void QgsLayerTreeModel::nodeLayerWillBeUnloaded()
+{
+  QgsLayerTreeLayer* nodeLayer = qobject_cast<QgsLayerTreeLayer*>( sender() );
+  if ( !nodeLayer )
+    return;
+
+  disconnectFromLayer( nodeLayer );
+
+  // wait for the layer to appear again
+  connect( nodeLayer, SIGNAL( layerLoaded() ), this, SLOT( nodeLayerLoaded() ) );
+}
+
 void QgsLayerTreeModel::layerLegendChanged()
 {
   if ( !testFlag( ShowSymbology ) )
@@ -685,6 +702,9 @@ void QgsLayerTreeModel::connectToLayer( QgsLayerTreeLayer* nodeLayer )
     return;
   }
 
+  // watch if the layer is getting removed
+  connect( nodeLayer, SIGNAL( layerWillBeUnloaded() ), this, SLOT( nodeLayerWillBeUnloaded() ) );
+
   if ( testFlag( ShowSymbology ) )
   {
     addSymbologyToLayer( nodeLayer );
@@ -733,6 +753,8 @@ static int _numLayerCount( QgsLayerTreeGroup* group, const QString& layerId )
 
 void QgsLayerTreeModel::disconnectFromLayer( QgsLayerTreeLayer* nodeLayer )
 {
+  disconnect( nodeLayer, 0, this, 0 ); // disconnect from delayed load of layer
+
   if ( !nodeLayer->layer() )
     return; // we were never connected
 
@@ -759,6 +781,39 @@ void QgsLayerTreeModel::connectToLayers( QgsLayerTreeGroup* parentGroup )
   }
 }
 
+void QgsLayerTreeModel::disconnectFromLayers( QgsLayerTreeGroup* parentGroup )
+{
+  foreach ( QgsLayerTreeNode* node, parentGroup->children() )
+  {
+    if ( QgsLayerTree::isGroup( node ) )
+      disconnectFromLayers( QgsLayerTree::toGroup( node ) );
+    else if ( QgsLayerTree::isLayer( node ) )
+      disconnectFromLayer( QgsLayerTree::toLayer( node ) );
+  }
+}
+
+void QgsLayerTreeModel::connectToRootNode()
+{
+  Q_ASSERT( mRootNode );
+
+  connect( mRootNode, SIGNAL( willAddChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeWillAddChildren( QgsLayerTreeNode*, int, int ) ) );
+  connect( mRootNode, SIGNAL( addedChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeAddedChildren( QgsLayerTreeNode*, int, int ) ) );
+  connect( mRootNode, SIGNAL( willRemoveChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeWillRemoveChildren( QgsLayerTreeNode*, int, int ) ) );
+  connect( mRootNode, SIGNAL( removedChildren( QgsLayerTreeNode*, int, int ) ), this, SLOT( nodeRemovedChildren() ) );
+  connect( mRootNode, SIGNAL( visibilityChanged( QgsLayerTreeNode*, Qt::CheckState ) ), this, SLOT( nodeVisibilityChanged( QgsLayerTreeNode* ) ) );
+
+  connect( mRootNode, SIGNAL( customPropertyChanged( QgsLayerTreeNode*, QString ) ), this, SLOT( nodeCustomPropertyChanged( QgsLayerTreeNode*, QString ) ) );
+
+  connectToLayers( mRootNode );
+}
+
+void QgsLayerTreeModel::disconnectFromRootNode()
+{
+  disconnect( mRootNode, 0, this, 0 );
+
+  disconnectFromLayers( mRootNode );
+}
+
 void QgsLayerTreeModel::recursivelyEmitDataChanged( const QModelIndex& idx )
 {
   QgsLayerTreeNode* node = index2node( idx );

src/core/layertree/qgslayertreemodel.h

@@ -110,6 +110,9 @@ class CORE_EXPORT QgsLayerTreeModel : public QAbstractItemModel
 
     //! Return pointer to the root node of the layer tree. Always a non-null pointer.
     QgsLayerTreeGroup* rootGroup();
+    //! Reset the model and use a new root group node
+    //! @note added in 2.6
+    void setRootGroup( QgsLayerTreeGroup* newRootGroup );
 
     //! Force a refresh of symbology of layer node.
     //! Not necessary to call when layer's renderer is changed as the model listens to these events.
@@ -143,6 +146,7 @@ class CORE_EXPORT QgsLayerTreeModel : public QAbstractItemModel
     void nodeCustomPropertyChanged( QgsLayerTreeNode* node, const QString& key );
 
     void nodeLayerLoaded();
+    void nodeLayerWillBeUnloaded();
     void layerLegendChanged();
 
     void layerNeedsUpdate();
@@ -154,7 +158,10 @@ class CORE_EXPORT QgsLayerTreeModel : public QAbstractItemModel
     void connectToLayer( QgsLayerTreeLayer* nodeLayer );
     void disconnectFromLayer( QgsLayerTreeLayer* nodeLayer );
 
-    void connectToLayers(QgsLayerTreeGroup* parentGroup );
+    void connectToLayers( QgsLayerTreeGroup* parentGroup );
+    void disconnectFromLayers( QgsLayerTreeGroup* parentGroup );
+    void connectToRootNode();
+    void disconnectFromRootNode();
 
     //! emit dataChanged() for layer tree node items
     void recursivelyEmitDataChanged( const QModelIndex& index = QModelIndex() );

src/gui/layertree/qgslayertreeview.cpp

@@ -61,6 +61,8 @@ void QgsLayerTreeView::setModel( QAbstractItemModel* model )
 
   connect( selectionModel(), SIGNAL( currentChanged( QModelIndex, QModelIndex ) ), this, SLOT( onCurrentChanged() ) );
 
+  connect( layerTreeModel(), SIGNAL( modelReset() ), this, SLOT( onModelReset() ) );
+
   updateExpandedStateFromNode( layerTreeModel()->rootGroup() );
 }
 
@@ -172,6 +174,11 @@ void QgsLayerTreeView::onExpandedChanged( QgsLayerTreeNode* node, bool expanded
     setExpanded( idx, expanded );
 }
 
+void QgsLayerTreeView::onModelReset()
+{
+  updateExpandedStateFromNode( layerTreeModel()->rootGroup() );
+}
+
 void QgsLayerTreeView::updateExpandedStateFromNode( QgsLayerTreeNode* node )
 {
   QModelIndex idx = layerTreeModel()->node2index( node );

src/gui/layertree/qgslayertreeview.h

@@ -105,6 +105,7 @@ class GUI_EXPORT QgsLayerTreeView : public QTreeView
 
     void onCurrentChanged();
     void onExpandedChanged( QgsLayerTreeNode* node, bool expanded );
+    void onModelReset();
 
   protected:
     //! helper class with default actions. Lazily initialized.