Add possibility to temporarily disable layer tree to registry bridge

This is useful during the project load where the updates from
map layer registry would make the layers appear twice in the tree

Author: wonder-sk

src/core/layertree/qgslayertreeregistrybridge.cpp

@@ -7,6 +7,7 @@
 QgsLayerTreeRegistryBridge::QgsLayerTreeRegistryBridge(QgsLayerTreeGroup *root, QObject *parent)
   : QObject(parent)
   , mRoot(root)
+  , mEnabled(true)
 {
   connect(QgsMapLayerRegistry::instance(), SIGNAL(layersAdded(QList<QgsMapLayer*>)), this, SLOT(layersAdded(QList<QgsMapLayer*>)));
   connect(QgsMapLayerRegistry::instance(), SIGNAL(layersWillBeRemoved(QStringList)), this, SLOT(layersWillBeRemoved(QStringList)));
@@ -16,6 +17,9 @@ QgsLayerTreeRegistryBridge::QgsLayerTreeRegistryBridge(QgsLayerTreeGroup *root,
 
 void QgsLayerTreeRegistryBridge::layersAdded(QList<QgsMapLayer*> layers)
 {
+  if (!mEnabled)
+    return;
+
   foreach (QgsMapLayer* layer, layers)
   {
     mRoot->addLayer(layer);
@@ -24,6 +28,9 @@ void QgsLayerTreeRegistryBridge::layersAdded(QList<QgsMapLayer*> layers)
 
 void QgsLayerTreeRegistryBridge::layersWillBeRemoved(QStringList layerIds)
 {
+  if (!mEnabled)
+    return;
+
   foreach (QString layerId, layerIds)
   {
     QgsLayerTreeLayer* nodeLayer = mRoot->findLayer(layerId);

src/core/layertree/qgslayertreeregistrybridge.h

@@ -17,6 +17,9 @@ class CORE_EXPORT QgsLayerTreeRegistryBridge : public QObject
 public:
   explicit QgsLayerTreeRegistryBridge(QgsLayerTreeGroup* root, QObject *parent = 0);
 
+  void setEnabled(bool enabled) { mEnabled = enabled; }
+  bool isEnabled() const { return mEnabled; }
+
 signals:
 
 protected slots:
@@ -33,6 +36,7 @@ protected slots:
 protected:
   QgsLayerTreeGroup* mRoot;
   QStringList mLayerIdsForRemoval;
+  bool mEnabled;
 };
 
 #endif // QGSLAYERTREEREGISTRYBRIDGE_H

src/core/qgsproject.cpp

@@ -342,7 +342,7 @@ QgsProject::QgsProject()
   // bind the layer tree to the map layer registry.
   // whenever layers are added to or removed from the registry,
   // layer tree will be updated
-  new QgsLayerTreeRegistryBridge(mRootGroup, this);
+  mLayerTreeRegistryBridge = new QgsLayerTreeRegistryBridge(mRootGroup, this);
 
 } // QgsProject ctor
 
@@ -915,6 +915,8 @@ bool QgsProject::read()
 
   QgsDebugMsg( "Loaded layer tree:\n " + mRootGroup->dump() );
 
+  mLayerTreeRegistryBridge->setEnabled( false );
+
   // get the map layers
   QPair< bool, QList<QDomNode> > getMapLayersResults =  _getMapLayers( *doc );
 
@@ -935,6 +937,8 @@ bool QgsProject::read()
     mBadLayerHandler->handleBadLayers( getMapLayersResults.second, *doc );
   }
 
+  mLayerTreeRegistryBridge->setEnabled( true );
+
   // read the project: used by map canvas and legend
   emit readProject( *doc );
 

src/core/qgsproject.h

@@ -40,6 +40,7 @@ class QDomElement;
 class QDomNode;
 
 class QgsLayerTreeGroup;
+class QgsLayerTreeRegistryBridge;
 class QgsMapLayer;
 class QgsProjectBadLayerHandler;
 class QgsRelationManager;
@@ -417,6 +418,8 @@ class CORE_EXPORT QgsProject : public QObject
 
     QgsLayerTreeGroup* mRootGroup;
 
+    QgsLayerTreeRegistryBridge* mLayerTreeRegistryBridge;
+
 }; // QgsProject