Fix layer tree expanded state when used expand/collapse all (fixes #15691)

(cherry picked from commit de85fdd)

Author: wonder-sk

python/gui/layertree/qgslayertreeview.sip

@@ -72,6 +72,14 @@ class QgsLayerTreeView : QTreeView
     //! Force refresh of layer symbology. Normally not needed as the changes of layer's renderer are monitored by the model
     void refreshLayerSymbology( const QString& layerId );
 
+    //! Enhancement of QTreeView::expandAll() that also records expanded state in layer tree nodes
+    //! @note added in QGIS 2.18
+    void expandAllNodes();
+
+    //! Enhancement of QTreeView::collapseAll() that also records expanded state in layer tree nodes
+    //! @note added in QGIS 2.18
+    void collapseAllNodes();
+
   signals:
     //! Emitted when a current layer is changed
     void currentLayerChanged( QgsMapLayer* layer );

src/app/qgisapp.cpp

@@ -3104,11 +3104,11 @@ void QgisApp::initLayerTreeView()
   QAction* actionExpandAll = new QAction( tr( "Expand All" ), this );
   actionExpandAll->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionExpandTree.svg" ) ) );
   actionExpandAll->setToolTip( tr( "Expand All" ) );
-  connect( actionExpandAll, SIGNAL( triggered( bool ) ), mLayerTreeView, SLOT( expandAll() ) );
+  connect( actionExpandAll, SIGNAL( triggered( bool ) ), mLayerTreeView, SLOT( expandAllNodes() ) );
   QAction* actionCollapseAll = new QAction( tr( "Collapse All" ), this );
   actionCollapseAll->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionCollapseTree.svg" ) ) );
   actionCollapseAll->setToolTip( tr( "Collapse All" ) );
-  connect( actionCollapseAll, SIGNAL( triggered( bool ) ), mLayerTreeView, SLOT( collapseAll() ) );
+  connect( actionCollapseAll, SIGNAL( triggered( bool ) ), mLayerTreeView, SLOT( collapseAllNodes() ) );
 
   QWidget* spacer = new QWidget();
   spacer->setSizePolicy( QSizePolicy::Expanding, QSizePolicy::Expanding );

src/gui/layertree/qgslayertreeview.cpp

@@ -336,3 +336,49 @@ void QgsLayerTreeView::refreshLayerSymbology( const QString& layerId )
   if ( nodeLayer )
     layerTreeModel()->refreshLayerLegend( nodeLayer );
 }
+
+
+static void _expandAllLegendNodes( QgsLayerTreeLayer* nodeLayer, bool expanded, QgsLayerTreeModel* model )
+{
+  // for layers we also need to find out with legend nodes contain some children and make them expanded/collapsed
+  // if we are collapsing, we just write out an empty list
+  QStringList lst;
+  if ( expanded )
+  {
+    Q_FOREACH ( QgsLayerTreeModelLegendNode* legendNode, model->layerLegendNodes( nodeLayer ) )
+    {
+      QString parentKey = legendNode->data( QgsLayerTreeModelLegendNode::ParentRuleKeyRole ).toString();
+      if ( !parentKey.isEmpty() && !lst.contains( parentKey ) )
+        lst << parentKey;
+    }
+  }
+  nodeLayer->setCustomProperty( "expandedLegendNodes", lst );
+}
+
+
+static void _expandAllNodes( QgsLayerTreeGroup* parent, bool expanded, QgsLayerTreeModel* model )
+{
+  Q_FOREACH ( QgsLayerTreeNode* node, parent->children() )
+  {
+    node->setExpanded( expanded );
+    if ( QgsLayerTree::isGroup( node ) )
+      _expandAllNodes( QgsLayerTree::toGroup( node ), expanded, model );
+    else if ( QgsLayerTree::isLayer( node ) )
+      _expandAllLegendNodes( QgsLayerTree::toLayer( node ), expanded, model );
+  }
+}
+
+
+void QgsLayerTreeView::expandAllNodes()
+{
+  // unfortunately expandAll() does not emit expanded() signals
+  _expandAllNodes( layerTreeModel()->rootGroup(), true, layerTreeModel() );
+  expandAll();
+}
+
+void QgsLayerTreeView::collapseAllNodes()
+{
+  // unfortunately collapseAll() does not emit collapsed() signals
+  _expandAllNodes( layerTreeModel()->rootGroup(), false, layerTreeModel() );
+  collapseAll();
+}

src/gui/layertree/qgslayertreeview.h

@@ -92,6 +92,14 @@ class GUI_EXPORT QgsLayerTreeView : public QTreeView
     //! Force refresh of layer symbology. Normally not needed as the changes of layer's renderer are monitored by the model
     void refreshLayerSymbology( const QString& layerId );
 
+    //! Enhancement of QTreeView::expandAll() that also records expanded state in layer tree nodes
+    //! @note added in QGIS 2.18
+    void expandAllNodes();
+
+    //! Enhancement of QTreeView::collapseAll() that also records expanded state in layer tree nodes
+    //! @note added in QGIS 2.18
+    void collapseAllNodes();
+
   signals:
     //! Emitted when a current layer is changed
     void currentLayerChanged( QgsMapLayer* layer );