[layertree] Fix #10347 - save also old <legend> tag

QGIS server does not use QgsProject for loading of QGIS project.
In order to allow reading of new projects, let's also write the original <legend> tag to the project.
Ideally the server should be ported to new layer tree implementation, but that requires
non-trivial changes to the server components.
The <legend> tag is ignored by QGIS application in >= 2.4 and this way also the new project files
can be opened in older versions of QGIS without loosing information about layer groups.

src/app/qgisapp.cpp

@@ -9546,6 +9546,20 @@ void QgisApp::projectChanged( const QDomDocument &doc )
 
 void QgisApp::writeProject( QDomDocument &doc )
 {
+  // QGIS server does not use QgsProject for loading of QGIS project.
+  // In order to allow reading of new projects, let's also write the original <legend> tag to the project.
+  // Ideally the server should be ported to new layer tree implementation, but that requires
+  // non-trivial changes to the server components.
+  // The <legend> tag is ignored by QGIS application in >= 2.4 and this way also the new project files
+  // can be opened in older versions of QGIS without loosing information about layer groups.
+
+  QgsLayerTreeNode* clonedRoot = QgsProject::instance()->layerTreeRoot()->clone();
+  QgsLayerTreeUtils::removeChildrenOfEmbeddedGroups( QgsLayerTree::toGroup( clonedRoot ) );
+  QDomElement oldLegendElem = QgsLayerTreeUtils::writeOldLegend( doc, QgsLayerTree::toGroup( clonedRoot ),
+                mLayerTreeCanvasBridge->hasCustomLayerOrder(), mLayerTreeCanvasBridge->customLayerOrder() );
+  delete clonedRoot;
+  doc.firstChildElement( "qgis" ).appendChild( oldLegendElem );
+
   projectChanged( doc );
 }
 

src/core/layertree/qgslayertreeutils.cpp

@@ -99,6 +99,79 @@ bool QgsLayerTreeUtils::readOldLegendLayerOrder( const QDomElement& legendElem,
 }
 
 
+static QDomElement _writeOldLegendLayer( QDomDocument& doc, QgsLayerTreeLayer* nodeLayer, bool hasCustomOrder, const QStringList& order )
+{
+  int drawingOrder = -1;
+  if ( hasCustomOrder )
+    drawingOrder = order.indexOf( nodeLayer->layerId() );
+
+  QDomElement layerElem = doc.createElement( "legendlayer" );
+  layerElem.setAttribute( "drawingOrder", drawingOrder );
+  layerElem.setAttribute( "open", nodeLayer->isExpanded() ? "true" : "false" );
+  layerElem.setAttribute( "checked", QgsLayerTreeUtils::checkStateToXml( nodeLayer->isVisible() ) );
+  layerElem.setAttribute( "name", nodeLayer->layerName() );
+  layerElem.setAttribute( "showFeatureCount", nodeLayer->customProperty( "showFeatureCount" ).toInt() );
+
+  QDomElement fileGroupElem = doc.createElement( "filegroup" );
+  fileGroupElem.setAttribute( "open", nodeLayer->isExpanded() ? "true" : "false" );
+  fileGroupElem.setAttribute( "hidden", "false" );
+
+  QDomElement layerFileElem = doc.createElement( "legendlayerfile" );
+  layerFileElem.setAttribute( "isInOverview", nodeLayer->customProperty( "overview" ).toInt() );
+  layerFileElem.setAttribute( "layerid", nodeLayer->layerId() );
+  layerFileElem.setAttribute( "visible", nodeLayer->isVisible() == Qt::Checked ? 1 : 0 );
+
+  layerElem.appendChild( fileGroupElem );
+  fileGroupElem.appendChild( layerFileElem );
+  return layerElem;
+}
+
+// need forward declaration as write[..]Group and write[..]GroupChildren call each other
+static void _writeOldLegendGroupChildren( QDomDocument& doc, QDomElement& groupElem, QgsLayerTreeGroup* nodeGroup, bool hasCustomOrder, const QStringList& order );
+
+static QDomElement _writeOldLegendGroup( QDomDocument& doc, QgsLayerTreeGroup* nodeGroup, bool hasCustomOrder, const QStringList& order )
+{
+  QDomElement groupElem = doc.createElement( "legendgroup" );
+  groupElem.setAttribute( "open", nodeGroup->isExpanded() ? "true" : "false" );
+  groupElem.setAttribute( "name", nodeGroup->name() );
+  groupElem.setAttribute( "checked", QgsLayerTreeUtils::checkStateToXml( nodeGroup->isVisible() ) );
+
+  if ( nodeGroup->customProperty( "embedded" ).toInt() )
+  {
+    groupElem.setAttribute( "embedded", 1 );
+    groupElem.setAttribute( "project", nodeGroup->customProperty( "embedded_project" ).toString() );
+  }
+
+  _writeOldLegendGroupChildren( doc, groupElem, nodeGroup, hasCustomOrder, order );
+  return groupElem;
+}
+
+
+static void _writeOldLegendGroupChildren( QDomDocument& doc, QDomElement& groupElem, QgsLayerTreeGroup* nodeGroup, bool hasCustomOrder, const QStringList& order )
+{
+  foreach ( QgsLayerTreeNode* node, nodeGroup->children() )
+  {
+    if ( QgsLayerTree::isGroup( node ) )
+    {
+      groupElem.appendChild( _writeOldLegendGroup( doc, QgsLayerTree::toGroup( node ), hasCustomOrder, order ) );
+    }
+    else if ( QgsLayerTree::isLayer( node ) )
+    {
+      groupElem.appendChild( _writeOldLegendLayer( doc, QgsLayerTree::toLayer( node ), hasCustomOrder, order ) );
+    }
+  }
+}
+
+
+QDomElement QgsLayerTreeUtils::writeOldLegend( QDomDocument& doc, QgsLayerTreeGroup* root, bool hasCustomOrder, const QStringList& order )
+{
+  QDomElement legendElem = doc.createElement( "legend" );
+  legendElem.setAttribute( "updateDrawingOrder", hasCustomOrder ? "false" : "true" );
+
+  _writeOldLegendGroupChildren( doc, legendElem, root, hasCustomOrder, order );
+
+  return legendElem;
+}
 
 
 QString QgsLayerTreeUtils::checkStateToXml( Qt::CheckState state )
@@ -223,3 +296,17 @@ void QgsLayerTreeUtils::removeInvalidLayers( QgsLayerTreeGroup* group )
   foreach ( QgsLayerTreeNode* node, nodesToRemove )
     group->removeChildNode( node );
 }
+
+void QgsLayerTreeUtils::removeChildrenOfEmbeddedGroups( QgsLayerTreeGroup* group )
+{
+  foreach ( QgsLayerTreeNode* child, group->children() )
+  {
+    if ( QgsLayerTree::isGroup( child ) )
+    {
+      if ( child->customProperty( "embedded" ).toInt() )
+        QgsLayerTree::toGroup( child )->removeAllChildren();
+      else
+        removeChildrenOfEmbeddedGroups( QgsLayerTree::toGroup( child ) );
+    }
+  }
+}

src/core/layertree/qgslayertreeutils.h

@@ -20,6 +20,7 @@
 #include <QList>
 
 class QDomElement;
+class QDomDocument;
 class QStringList;
 
 class QgsLayerTreeGroup;
@@ -38,6 +39,8 @@ class CORE_EXPORT QgsLayerTreeUtils
     static bool readOldLegend( QgsLayerTreeGroup* root, const QDomElement& legendElem );
     //! Try to load custom layer order from <legend> tag from project files from QGIS 2.2 and below
     static bool readOldLegendLayerOrder( const QDomElement& legendElem, bool& hasCustomOrder, QStringList& order );
+    //! Return <legend> tag used in QGIS 2.2 and below
+    static QDomElement writeOldLegend( QDomDocument& doc, QgsLayerTreeGroup* root, bool hasCustomOrder, const QStringList& order );
 
     static QString checkStateToXml( Qt::CheckState state );
     static Qt::CheckState checkStateFromXml( QString txt );
@@ -45,7 +48,9 @@ class CORE_EXPORT QgsLayerTreeUtils
     static bool layersEditable( const QList<QgsLayerTreeLayer*>& layerNodes );
     static bool layersModified( const QList<QgsLayerTreeLayer*>& layerNodes );
 
-    static void removeInvalidLayers(QgsLayerTreeGroup* group );
+    static void removeInvalidLayers( QgsLayerTreeGroup* group );
+
+    static void removeChildrenOfEmbeddedGroups( QgsLayerTreeGroup* group );
 
   protected:
     static void addLegendGroupToTreeWidget( const QDomElement& groupElem, QgsLayerTreeGroup* parent );

src/core/qgsproject.cpp

@@ -995,21 +995,6 @@ void QgsProject::loadEmbeddedNodes( QgsLayerTreeGroup* group )
   }
 }
 
-void QgsProject::removeChildrenOfEmbeddedGroups( QgsLayerTreeGroup* group )
-{
-  foreach ( QgsLayerTreeNode* child, group->children() )
-  {
-    if ( QgsLayerTree::isGroup( child ) )
-    {
-      if ( child->customProperty( "embedded" ).toInt() )
-        QgsLayerTree::toGroup( child )->removeAllChildren();
-      else
-        removeChildrenOfEmbeddedGroups( QgsLayerTree::toGroup( child ) );
-    }
-  }
-}
-
-
 
 bool QgsProject::read( QDomNode & layerNode )
 {
@@ -1090,7 +1075,7 @@ bool QgsProject::write()
 
   // write layer tree - make sure it is without embedded subgroups
   QgsLayerTreeNode* clonedRoot = mRootGroup->clone();
-  removeChildrenOfEmbeddedGroups( QgsLayerTree::toGroup( clonedRoot ) );
+  QgsLayerTreeUtils::removeChildrenOfEmbeddedGroups( QgsLayerTree::toGroup( clonedRoot ) );
   clonedRoot->writeXML( qgisNode );
   delete clonedRoot;
 

src/core/qgsproject.h

@@ -357,8 +357,6 @@ class CORE_EXPORT QgsProject : public QObject
 
     void loadEmbeddedNodes( QgsLayerTreeGroup* group );
 
-    void removeChildrenOfEmbeddedGroups( QgsLayerTreeGroup* group );
-
   signals:
     //! emitted when project is being read
     void readProject( const QDomDocument & );