Added optional argument to keep legacy API and behavior

python/core/qgsbrowsermodel.sip

@@ -5,7 +5,7 @@ class QgsBrowserModel : QAbstractItemModel
 %End
 
   public:
-    explicit QgsBrowserModel( QObject *parent = 0 );
+    explicit QgsBrowserModel( QObject *parent = 0, bool initialize = true );
     ~QgsBrowserModel();
 
     enum ItemDataRole
@@ -81,6 +81,12 @@ class QgsBrowserModel : QAbstractItemModel
     bool canFetchMore( const QModelIndex & parent ) const;
     void fetchMore( const QModelIndex & parent );
 
+    //! Returns true if the model has been initialized
+    bool initialized( );
+
+    //! Delayed initialization
+    void init();
+
   signals:
     /** Emitted when item children fetch was finished */
     void stateChanged( const QModelIndex & index, QgsDataItem::State oldState );

src/app/qgisapp.cpp

@@ -804,7 +804,8 @@ QgisApp::QgisApp( QSplashScreen *splash, bool restorePlugins, bool skipVersionCh
   mSnappingDialog->setObjectName( "SnappingOption" );
   endProfile();
 
-  mBrowserModel = new QgsBrowserModel( this );
+  // Create the (shared) model with delayed initialization
+  mBrowserModel = new QgsBrowserModel( this, false );
   mBrowserWidget = new QgsBrowserDockWidget( tr( "Browser Panel" ), mBrowserModel, this );
   mBrowserWidget->setObjectName( "Browser" );
   addDockWidget( Qt::LeftDockWidgetArea, mBrowserWidget );

src/core/qgsbrowsermodel.cpp

@@ -47,12 +47,14 @@ static bool cmpByDataItemName_( QgsDataItem* a, QgsDataItem* b )
   return QString::localeAwareCompare( a->name(), b->name() ) < 0;
 }
 
-QgsBrowserModel::QgsBrowserModel( QObject *parent )
+QgsBrowserModel::QgsBrowserModel( QObject *parent, bool initialize )
     : QAbstractItemModel( parent )
     , mFavourites( nullptr )
     , mProjectHome( nullptr )
     , mInitialized( false )
 {
+  if ( initialize )
+    init();
 }
 
 QgsBrowserModel::~QgsBrowserModel()

src/core/qgsbrowsermodel.h

@@ -53,7 +53,13 @@ class CORE_EXPORT QgsBrowserModel : public QAbstractItemModel
     Q_OBJECT
 
   public:
-    explicit QgsBrowserModel( QObject *parent = nullptr );
+
+    /**
+      * @brief QgsBrowserModel
+      * @param parent
+      * @param initialize immediately called init, default to true
+      */
+    explicit QgsBrowserModel( QObject *parent = nullptr , bool initialize = true );
     ~QgsBrowserModel();
 
     enum ItemDataRole