Attribute table selection: performance improvements

When selecting features with the mouse (click and drag) only redraw
the map canvas, once the mouse is released.

Author: m-kuhn

src/gui/attributetable/qgsattributetablefiltermodel.cpp

@@ -179,7 +179,10 @@ void QgsAttributeTableFilterModel::masterSelectionChanged( const QItemSelection
   }
 
   // Now emit the signal
-  layer()->setSelectedFeatures( layer()->selectedFeaturesIds() );
+  if ( mSyncSelection )
+  {
+    layer()->setSelectedFeatures( layer()->selectedFeaturesIds() );
+  }
 
   connect( layer(), SIGNAL( selectionChanged() ), this, SLOT( selectionChanged() ) );
 }
@@ -321,6 +324,17 @@ QItemSelectionModel* QgsAttributeTableFilterModel::masterSelection()
   return mMasterSelection;
 }
 
+void QgsAttributeTableFilterModel::disableSelectionSync()
+{
+  mSyncSelection = false;
+}
+
+void QgsAttributeTableFilterModel::enableSelectionSync()
+{
+  mSyncSelection = true;
+  layer()->setSelectedFeatures( layer()->selectedFeaturesIds() );
+}
+
 QModelIndex QgsAttributeTableFilterModel::mapToMaster( const QModelIndex &proxyIndex ) const
 {
   // Master is source

src/gui/attributetable/qgsattributetablefiltermodel.h

@@ -91,6 +91,11 @@ class GUI_EXPORT QgsAttributeTableFilterModel: public QSortFilterProxyModel
      */
     inline QgsVectorLayer *layer() const { return masterModel()->layer(); }
 
+    /**
+     * Returns the layerCache this filter acts on.
+     *
+     * @return The layer cache
+     */
     inline QgsVectorLayerCache *layerCache() const { return masterModel()->layerCache(); }
 
     /**
@@ -120,6 +125,21 @@ class GUI_EXPORT QgsAttributeTableFilterModel: public QSortFilterProxyModel
      */
     QItemSelectionModel* masterSelection();
 
+    /**
+     * Disables selection synchronisation with the map canvas. Changes to the selection in the master
+     * model are propagated to the layer, but no redraw is requested until @link{enableSelectionSync()}
+     * is called.
+     */
+    void disableSelectionSync();
+
+    /**
+     * Enables selection synchronisation with the map canvas. Changes to the selection in the master
+     * are propagated and upon every change, a redraw will be requested. This method will update the
+     * selection to account for any cached selection change since @link{disableSelectionSync()} was
+     * called.
+     */
+    void enableSelectionSync();
+
     virtual QModelIndex mapToMaster( const QModelIndex &proxyIndex ) const;
 
     virtual QModelIndex mapFromMaster( const QModelIndex &sourceIndex ) const;
@@ -194,6 +214,7 @@ class GUI_EXPORT QgsAttributeTableFilterModel: public QSortFilterProxyModel
     bool mSelectedOnTop;
     QItemSelectionModel* mMasterSelection;
     QgsAttributeTableModel* mTableModel;
+    bool mSyncSelection;
 };
 
 #endif

src/gui/attributetable/qgsattributetableview.cpp

@@ -46,7 +46,7 @@ QgsAttributeTableView::QgsAttributeTableView( QWidget *parent )
   setSelectionMode( QAbstractItemView::ExtendedSelection );
   setSortingEnabled( true );
 
-  connect( verticalHeader(), SIGNAL( sectionClicked( int ) ), SLOT( onVerticalHeaderSectionClicked( int ) ) );
+  verticalHeader()->viewport()->installEventFilter( this );
 }
 
 QgsAttributeTableView::~QgsAttributeTableView()
@@ -75,6 +75,30 @@ void QgsAttributeTableView::setCanvasAndLayerCache( QgsMapCanvas *canvas, QgsVec
   delete filterModel;
 }
 
+bool QgsAttributeTableView::eventFilter(QObject *object, QEvent *event)
+{
+  if ( object == verticalHeader()->viewport() )
+  {
+
+    qDebug() << "Event " << event->type();
+
+    switch ( event->type() )
+    {
+      case QEvent::MouseButtonPress:
+        mFilterModel->disableSelectionSync();
+        break;
+
+      case QEvent::MouseButtonRelease:
+        mFilterModel->enableSelectionSync();
+        break;
+
+      default:
+        break;
+    }
+  }
+  return false;
+}
+
 void QgsAttributeTableView::setModel( QgsAttributeTableFilterModel* filterModel )
 {
   if ( mFilterModel )
@@ -158,22 +182,6 @@ void QgsAttributeTableView::keyPressEvent( QKeyEvent *event )
   }
 }
 
-void QgsAttributeTableView::onVerticalHeaderSectionClicked( int logicalIndex )
-{
-  Q_UNUSED( logicalIndex )
-
-  QgsFeatureIds selectedFeatures;
-
-  QModelIndexList selectedRows = selectionModel()->selectedRows();
-
-  foreach ( QModelIndex row, selectedRows )
-  {
-    selectedFeatures.insert( mFilterModel->rowToId( row ) );
-  }
-
-  emit selectionChangeFinished( selectedFeatures );
-}
-
 void QgsAttributeTableView::onFilterAboutToBeInvalidated()
 {
   disconnect( selectionModel(), SIGNAL( selectionChanged( QItemSelection, QItemSelection ) ), this, SLOT( onSelectionChanged( QItemSelection, QItemSelection ) ) );

src/gui/attributetable/qgsattributetableview.h

@@ -63,6 +63,18 @@ class GUI_EXPORT QgsAttributeTableView : public QTableView
      */
     void setCanvasAndLayerCache( QgsMapCanvas *canvas, QgsVectorLayerCache *layerCache );
 
+    /**
+     * This event filter is installed on the verticalHeader to intercept mouse press and release
+     * events. These are used to disable / enable live synchronisation with the map canvas selection
+     * which can be slow due to recurring canvas repaints. Updating the
+     *
+     * @param object The object which is the target of the event.
+     * @param event  The intercepted event
+     *
+     * @return Returns always false, so the event gets processed
+     */
+    virtual bool eventFilter( QObject* object, QEvent* event );
+
   protected:
     /**
      * Called for mouse press events on a table cell.
@@ -124,23 +136,7 @@ class GUI_EXPORT QgsAttributeTableView : public QTableView
 
     void finished();
 
-    /**
-     * @brief
-     * Is emitted, after the selection has been changed.
-     *
-     * @param selectedFeatures  A list of currently selected features.
-     */
-    void selectionChangeFinished( const QgsFeatureIds &selectedFeatures );
-
   public slots:
-    /**
-     * Is triggered after a mouse release event on the vertical header.
-     * Emits a selectionChangeFinished() signal, so the underlying sort filter
-     * can adapt to the current selection without disturbing the users current interaction.
-     *
-     * @param logicalIndex The section's logical index
-     */
-    void onVerticalHeaderSectionClicked( int logicalIndex );
     void onFilterAboutToBeInvalidated();
     void onFilterInvalidated();
     void onSelectionChanged( const QItemSelection& selected, const QItemSelection& deselected );

src/gui/attributetable/qgsfeaturelistmodel.cpp

@@ -238,3 +238,13 @@ int QgsFeatureListModel::rowCount( const QModelIndex& parent ) const
   Q_UNUSED( parent )
   return sourceModel()->rowCount();
 }
+
+void QgsFeatureListModel::disableSelectionSync()
+{
+  mFilterModel->disableSelectionSync();
+}
+
+void QgsFeatureListModel::enableSelectionSync()
+{
+  mFilterModel->enableSelectionSync();
+}

src/gui/attributetable/qgsfeaturelistmodel.h

@@ -85,6 +85,21 @@ class QgsFeatureListModel : public QAbstractProxyModel
     virtual int columnCount( const QModelIndex&parent = QModelIndex() ) const;
     virtual int rowCount( const QModelIndex& parent = QModelIndex() ) const;
 
+    /**
+     * Disables selection synchronisation with the map canvas. Changes to the selection in the master
+     * model are propagated to the layer, but no redraw is requested until @link{enableSelectionSync()}
+     * is called.
+     */
+    void disableSelectionSync();
+
+    /**
+     * Enables selection synchronisation with the map canvas. Changes to the selection in the master
+     * are propagated and upon every change, a redraw will be requested. This method will update the
+     * selection to account for any cached selection change since @link{disableSelectionSync()} was
+     * called.
+     */
+    void enableSelectionSync();
+
   public slots:
     void onBeginRemoveRows( const QModelIndex& parent, int first, int last );
     void onEndRemoveRows( const QModelIndex& parent, int first, int last );

src/gui/attributetable/qgsfeaturelistview.cpp

@@ -115,15 +115,22 @@ void QgsFeatureListView::mousePressEvent( QMouseEvent *event )
   }
   else
   {
+    mModel->disableSelectionSync();
     QListView::mousePressEvent( event );
   }
 }
 
 void QgsFeatureListView::mouseReleaseEvent( QMouseEvent *event )
 {
-  mEditSelectionDrag = false;
-
-  QListView::mouseReleaseEvent( event );
+  if ( mEditSelectionDrag )
+  {
+    mEditSelectionDrag = false;
+  }
+  else
+  {
+    QListView::mouseReleaseEvent( event );
+    mModel->enableSelectionSync();
+  }
 }
 
 void QgsFeatureListView::editSelectionChanged( QItemSelection deselected, QItemSelection selected )