qgsproject.cpp

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/***************************************************************************
                          qgsproject.cpp -  description
                             -------------------
  begin                : July 23, 2004
  copyright            : (C) 2004 by Mark Coletti
  email                : mcoletti at gmail.com
***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#include "qgsproject.h"

#include "qgsdatasourceuri.h"
#include "qgslabelingenginesettings.h"
#include "qgslayertree.h"
#include "qgslayertreeutils.h"
#include "qgslayertreeregistrybridge.h"
#include "qgslogger.h"
#include "qgsmessagelog.h"
#include "qgspluginlayer.h"
#include "qgspluginlayerregistry.h"
#include "qgsprojectfiletransform.h"
#include "qgssnappingconfig.h"
#include "qgspathresolver.h"
#include "qgsprojectstorage.h"
#include "qgsprojectstorageregistry.h"
#include "qgsprojectversion.h"
#include "qgsrasterlayer.h"
#include "qgsreadwritecontext.h"
#include "qgsrectangle.h"
#include "qgsrelationmanager.h"
#include "qgsannotationmanager.h"
#include "qgsvectorlayer.h"
#include "qgsvectorlayerjoininfo.h"
#include "qgsmapthemecollection.h"
#include "qgslayerdefinition.h"
#include "qgsunittypes.h"
#include "qgstransaction.h"
#include "qgstransactiongroup.h"
#include "qgsvectordataprovider.h"
#include "qgsprojectbadlayerhandler.h"
#include "qgssettings.h"
#include "qgsmaplayerlistutils.h"
#include "qgsmeshlayer.h"
#include "qgslayoutmanager.h"
#include "qgsmaplayerstore.h"
#include "qgsziputils.h"
#include "qgsauxiliarystorage.h"

#include <QApplication>
#include <QFileInfo>
#include <QDomNode>
#include <QObject>
#include <QTextStream>
#include <QTemporaryFile>
#include <QDir>
#include <QUrl>

#ifdef _MSC_VER
#include <sys/utime.h>
#else
#include <utime.h>
#endif

// canonical project instance
QgsProject *QgsProject::sProject = nullptr;

QStringList makeKeyTokens_( const QString &scope, const QString &key )
{
  QStringList keyTokens = QStringList( scope );
  keyTokens += key.split( '/', QString::SkipEmptyParts );

  // be sure to include the canonical root node
  keyTokens.push_front( QStringLiteral( "properties" ) );

  //check validy of keys since an unvalid xml name will will be dropped upon saving the xml file. If not valid, we print a message to the console.
  for ( int i = 0; i < keyTokens.size(); ++i )
  {
    QString keyToken = keyTokens.at( i );

    //invalid chars in XML are found at http://www.w3.org/TR/REC-xml/#NT-NameChar
    //note : it seems \x10000-\xEFFFF is valid, but it when added to the regexp, a lot of unwanted characters remain
    QString nameCharRegexp = QStringLiteral( "[^:A-Z_a-z\\xC0-\\xD6\\xD8-\\xF6\\xF8-\\x2FF\\x370-\\x37D\\x37F-\\x1FFF\\x200C-\\x200D\\x2070-\\x218F\\x2C00-\\x2FEF\\x3001-\\xD7FF\\xF900-\\xFDCF\\xFDF0-\\xFFFD\\-\\.0-9\\xB7\\x0300-\\x036F\\x203F-\\x2040]" );
    QString nameStartCharRegexp = QStringLiteral( "^[^:A-Z_a-z\\xC0-\\xD6\\xD8-\\xF6\\xF8-\\x2FF\\x370-\\x37D\\x37F-\\x1FFF\\x200C-\\x200D\\x2070-\\x218F\\x2C00-\\x2FEF\\x3001-\\xD7FF\\xF900-\\xFDCF\\xFDF0-\\xFFFD]" );

    if ( keyToken.contains( QRegExp( nameCharRegexp ) ) || keyToken.contains( QRegExp( nameStartCharRegexp ) ) )
    {

      QString errorString = QObject::tr( "Entry token invalid : '%1'. The token will not be saved to file." ).arg( keyToken );
      QgsMessageLog::logMessage( errorString, QString(), Qgis::Critical );

    }

  }

  return keyTokens;
}



QgsProjectProperty *findKey_( const QString &scope,
                              const QString &key,
                              QgsProjectPropertyKey &rootProperty )
{
  QgsProjectPropertyKey *currentProperty = &rootProperty;
  QgsProjectProperty *nextProperty;           // link to next property down hierarchy

  QStringList keySequence = makeKeyTokens_( scope, key );

  while ( !keySequence.isEmpty() )
  {
    // if the current head of the sequence list matches the property name,
    // then traverse down the property hierarchy
    if ( keySequence.first() == currentProperty->name() )
    {
      // remove front key since we're traversing down a level
      keySequence.pop_front();

      if ( 1 == keySequence.count() )
      {
        // if we have only one key name left, then return the key found
        return currentProperty->find( keySequence.front() );
      }
      else if ( keySequence.isEmpty() )
      {
        // if we're out of keys then the current property is the one we
        // want; i.e., we're in the rate case of being at the top-most
        // property node
        return currentProperty;
      }
      else if ( ( nextProperty = currentProperty->find( keySequence.first() ) ) )
      {
        if ( nextProperty->isKey() )
        {
          currentProperty = static_cast<QgsProjectPropertyKey *>( nextProperty );
        }
        else if ( nextProperty->isValue() && 1 == keySequence.count() )
        {
          // it may be that this may be one of several property value
          // nodes keyed by QDict string; if this is the last remaining
          // key token and the next property is a value node, then
          // that's the situation, so return the currentProperty
          return currentProperty;
        }
        else
        {
          // QgsProjectPropertyValue not Key, so return null
          return nullptr;
        }
      }
      else
      {
        // if the next key down isn't found
        // then the overall key sequence doesn't exist
        return nullptr;
      }
    }
    else
    {
      return nullptr;
    }
  }

  return nullptr;
}



QgsProjectProperty *addKey_( const QString &scope,
                             const QString &key,
                             QgsProjectPropertyKey *rootProperty,
                             const QVariant &value )
{
  QStringList keySequence = makeKeyTokens_( scope, key );

  // cursor through property key/value hierarchy
  QgsProjectPropertyKey *currentProperty = rootProperty;
  QgsProjectProperty *nextProperty; // link to next property down hierarchy
  QgsProjectPropertyKey *newPropertyKey = nullptr;

  while ( ! keySequence.isEmpty() )
  {
    // if the current head of the sequence list matches the property name,
    // then traverse down the property hierarchy
    if ( keySequence.first() == currentProperty->name() )
    {
      // remove front key since we're traversing down a level
      keySequence.pop_front();

      // if key sequence has one last element, then we use that as the
      // name to store the value
      if ( 1 == keySequence.count() )
      {
        currentProperty->setValue( keySequence.front(), value );
        return currentProperty;
      }
      // we're at the top element if popping the keySequence element
      // will leave it empty; in that case, just add the key
      else if ( keySequence.isEmpty() )
      {
        currentProperty->setValue( value );

        return currentProperty;
      }
      else if ( ( nextProperty = currentProperty->find( keySequence.first() ) ) )
      {
        currentProperty = dynamic_cast<QgsProjectPropertyKey *>( nextProperty );

        if ( currentProperty )
        {
          continue;
        }
        else            // QgsProjectPropertyValue not Key, so return null
        {
          return nullptr;
        }
      }
      else                // the next subkey doesn't exist, so add it
      {
        if ( ( newPropertyKey = currentProperty->addKey( keySequence.first() ) ) )
        {
          currentProperty = newPropertyKey;
        }
        continue;
      }
    }
    else
    {
      return nullptr;
    }
  }

  return nullptr;

}


void removeKey_( const QString &scope,
                 const QString &key,
                 QgsProjectPropertyKey &rootProperty )
{
  QgsProjectPropertyKey *currentProperty = &rootProperty;

  QgsProjectProperty *nextProperty = nullptr;   // link to next property down hierarchy
  QgsProjectPropertyKey *previousQgsPropertyKey = nullptr; // link to previous property up hierarchy

  QStringList keySequence = makeKeyTokens_( scope, key );

  while ( ! keySequence.isEmpty() )
  {
    // if the current head of the sequence list matches the property name,
    // then traverse down the property hierarchy
    if ( keySequence.first() == currentProperty->name() )
    {
      // remove front key since we're traversing down a level
      keySequence.pop_front();

      // if we have only one key name left, then try to remove the key
      // with that name
      if ( 1 == keySequence.count() )
      {
        currentProperty->removeKey( keySequence.front() );
      }
      // if we're out of keys then the current property is the one we
      // want to remove, but we can't delete it directly; we need to
      // delete it from the parent property key container
      else if ( keySequence.isEmpty() )
      {
        previousQgsPropertyKey->removeKey( currentProperty->name() );
      }
      else if ( ( nextProperty = currentProperty->find( keySequence.first() ) ) )
      {
        previousQgsPropertyKey = currentProperty;
        currentProperty = dynamic_cast<QgsProjectPropertyKey *>( nextProperty );

        if ( currentProperty )
        {
          continue;
        }
        else            // QgsProjectPropertyValue not Key, so return null
        {
          return;
        }
      }
      else                // if the next key down isn't found
      {
        // then the overall key sequence doesn't exist
        return;
      }
    }
    else
    {
      return;
    }
  }

}

QgsProject::QgsProject( QObject *parent )
  : QObject( parent )
  , mLayerStore( new QgsMapLayerStore( this ) )
  , mBadLayerHandler( new QgsProjectBadLayerHandler() )
  , mSnappingConfig( this )
  , mRelationManager( new QgsRelationManager( this ) )
  , mAnnotationManager( new QgsAnnotationManager( this ) )
  , mLayoutManager( new QgsLayoutManager( this ) )
  , mRootGroup( new QgsLayerTree )
  , mLabelingEngineSettings( new QgsLabelingEngineSettings )
  , mArchive( new QgsProjectArchive() )
  , mAuxiliaryStorage( new QgsAuxiliaryStorage() )
{
  mProperties.setName( QStringLiteral( "properties" ) );
  clear();

  // bind the layer tree to the map layer registry.
  // whenever layers are added to or removed from the registry,
  // layer tree will be updated
  mLayerTreeRegistryBridge = new QgsLayerTreeRegistryBridge( mRootGroup, this, this );
  connect( this, &QgsProject::layersAdded, this, &QgsProject::onMapLayersAdded );
  connect( this, &QgsProject::layersRemoved, this, [ = ] { cleanTransactionGroups(); } );
  connect( this, static_cast < void ( QgsProject::* )( const QList<QgsMapLayer *> & ) >( &QgsProject::layersWillBeRemoved ), this, &QgsProject::onMapLayersRemoved );

  // proxy map layer store signals to this
  connect( mLayerStore.get(), static_cast<void ( QgsMapLayerStore::* )( const QStringList & )>( &QgsMapLayerStore::layersWillBeRemoved ),
           this, static_cast<void ( QgsProject::* )( const QStringList & )>( &QgsProject::layersWillBeRemoved ) );
  connect( mLayerStore.get(), static_cast<void ( QgsMapLayerStore::* )( const QList<QgsMapLayer *> & )>( &QgsMapLayerStore::layersWillBeRemoved ),
           this, static_cast<void ( QgsProject::* )( const QList<QgsMapLayer *> & )>( &QgsProject::layersWillBeRemoved ) );
  connect( mLayerStore.get(), static_cast<void ( QgsMapLayerStore::* )( const QString & )>( &QgsMapLayerStore::layerWillBeRemoved ),
           this, static_cast<void ( QgsProject::* )( const QString & )>( &QgsProject::layerWillBeRemoved ) );
  connect( mLayerStore.get(), static_cast<void ( QgsMapLayerStore::* )( QgsMapLayer * )>( &QgsMapLayerStore::layerWillBeRemoved ),
           this, static_cast<void ( QgsProject::* )( QgsMapLayer * )>( &QgsProject::layerWillBeRemoved ) );
  connect( mLayerStore.get(), static_cast<void ( QgsMapLayerStore::* )( const QStringList & )>( &QgsMapLayerStore::layersRemoved ), this, &QgsProject::layersRemoved );
  connect( mLayerStore.get(), &QgsMapLayerStore::layerRemoved, this, &QgsProject::layerRemoved );
  connect( mLayerStore.get(), &QgsMapLayerStore::allLayersRemoved, this, &QgsProject::removeAll );
  connect( mLayerStore.get(), &QgsMapLayerStore::layersAdded, this, &QgsProject::layersAdded );
  connect( mLayerStore.get(), &QgsMapLayerStore::layerWasAdded, this, &QgsProject::layerWasAdded );
}


QgsProject::~QgsProject()
{
  clear();
  delete mBadLayerHandler;
  delete mRelationManager;
  delete mLayerTreeRegistryBridge;
  delete mRootGroup;
  if ( this == sProject )
  {
    sProject = nullptr;
  }
}

void QgsProject::setInstance( QgsProject *project )
{
  sProject = project;
}


QgsProject *QgsProject::instance()
{
  if ( !sProject )
  {
    sProject = new QgsProject;
  }
  return sProject;
}

void QgsProject::setTitle( const QString &title )
{
  if ( title == mMetadata.title() )
    return;

  mMetadata.setTitle( title );
  emit metadataChanged();

  setDirty( true );
}

QString QgsProject::title() const
{
  return mMetadata.title();
}

bool QgsProject::isDirty() const
{
  return mDirty;
}

void QgsProject::setDirty( const bool dirty )
{
  if ( dirty && mDirtyBlockCount > 0 )
    return;

  if ( mDirty == dirty )
    return;

  mDirty = dirty;
  emit isDirtyChanged( mDirty );
}

void QgsProject::setPresetHomePath( const QString &path )
{
  if ( path == mHomePath )
    return;

  mHomePath = path;
  emit homePathChanged();

  setDirty( true );
}

void QgsProject::setFileName( const QString &name )
{
  if ( name == mFile.fileName() )
    return;

  QString oldHomePath = homePath();

  mFile.setFileName( name );
  emit fileNameChanged();

  QString newHomePath = homePath();
  if ( newHomePath != oldHomePath )
    emit homePathChanged();

  setDirty( true );
}

QString QgsProject::fileName() const
{
  return mFile.fileName();
}

QFileInfo QgsProject::fileInfo() const
{
  return QFileInfo( mFile );
}

QgsProjectStorage *QgsProject::projectStorage() const
{
  return QgsApplication::projectStorageRegistry()->projectStorageFromUri( mFile.fileName() );
}

QDateTime QgsProject::lastModified() const
{
  if ( QgsProjectStorage *storage = projectStorage() )
  {
    QgsProjectStorage::Metadata metadata;
    storage->readProjectStorageMetadata( mFile.fileName(), metadata );
    return metadata.lastModified;
  }
  else
  {
    return QFileInfo( mFile.fileName() ).lastModified();
  }
}

QString QgsProject::absoluteFilePath() const
{
  if ( projectStorage() )
    return QString();

  if ( mFile.fileName().isEmpty() )
    return QString();  // this is to protect ourselves from getting current directory from QFileInfo::absoluteFilePath()

  return QFileInfo( mFile.fileName() ).absoluteFilePath();
}

QString QgsProject::baseName() const
{
  if ( QgsProjectStorage *storage = projectStorage() )
  {
    QgsProjectStorage::Metadata metadata;
    storage->readProjectStorageMetadata( mFile.fileName(), metadata );
    return metadata.name;
  }
  else
  {
    return QFileInfo( mFile.fileName() ).baseName();
  }
}

QgsCoordinateReferenceSystem QgsProject::crs() const
{
  return mCrs;
}

void QgsProject::setCrs( const QgsCoordinateReferenceSystem &crs )
{
  mCrs = crs;
  writeEntry( QStringLiteral( "SpatialRefSys" ), QStringLiteral( "/ProjectionsEnabled" ), crs.isValid() ? 1 : 0 );
  setDirty( true );
  emit crsChanged();
}

QString QgsProject::ellipsoid() const
{
  if ( !crs().isValid() )
    return GEO_NONE;

  return readEntry( QStringLiteral( "Measure" ), QStringLiteral( "/Ellipsoid" ), GEO_NONE );
}

void QgsProject::setEllipsoid( const QString &ellipsoid )
{
  writeEntry( QStringLiteral( "Measure" ), QStringLiteral( "/Ellipsoid" ), ellipsoid );
  setDirty( true );
  emit ellipsoidChanged( ellipsoid );
}

QgsCoordinateTransformContext QgsProject::transformContext() const
{
  return mTransformContext;
}

void QgsProject::setTransformContext( const QgsCoordinateTransformContext &context )
{
  mTransformContext = context;
  emit transformContextChanged();
}

void QgsProject::clear()
{
  QgsSettings s;

  mFile.setFileName( QString() );
  mProperties.clearKeys();
  mHomePath.clear();
  mAutoTransaction = false;
  mEvaluateDefaultValues = false;
  mDirty = false;
  mTrustLayerMetadata = false;
  mCustomVariables.clear();
  mMetadata = QgsProjectMetadata();
  if ( !s.value( QStringLiteral( "projects/anonymize_new_projects" ), false, QgsSettings::Core ).toBool() )
  {
    mMetadata.setCreationDateTime( QDateTime::currentDateTime() );
    mMetadata.setAuthor( QgsApplication::userFullName() );
  }
  emit metadataChanged();

  QgsCoordinateTransformContext context;
  context.readSettings();
  setTransformContext( context );

  mEmbeddedLayers.clear();
  mRelationManager->clear();
  mAnnotationManager->clear();
  mLayoutManager->clear();
  mSnappingConfig.reset();
  emit snappingConfigChanged( mSnappingConfig );

  mMapThemeCollection.reset( new QgsMapThemeCollection( this ) );
  emit mapThemeCollectionChanged();

  mLabelingEngineSettings->clear();

  mAuxiliaryStorage.reset( new QgsAuxiliaryStorage() );
  mArchive->clear();

  emit labelingEngineSettingsChanged();

  // reset some default project properties
  // XXX THESE SHOULD BE MOVED TO STATUSBAR RELATED SOURCE
  writeEntry( QStringLiteral( "PositionPrecision" ), QStringLiteral( "/Automatic" ), true );
  writeEntry( QStringLiteral( "PositionPrecision" ), QStringLiteral( "/DecimalPlaces" ), 2 );
  writeEntry( QStringLiteral( "Paths" ), QStringLiteral( "/Absolute" ), false );

  //copy default units to project
  writeEntry( QStringLiteral( "Measurement" ), QStringLiteral( "/DistanceUnits" ), s.value( QStringLiteral( "/qgis/measure/displayunits" ) ).toString() );
  writeEntry( QStringLiteral( "Measurement" ), QStringLiteral( "/AreaUnits" ), s.value( QStringLiteral( "/qgis/measure/areaunits" ) ).toString() );

  removeAllMapLayers();
  mRootGroup->clear();

  setDirty( false );
  emit cleared();
}

// basically a debugging tool to dump property list values
void dump_( const QgsProjectPropertyKey &topQgsPropertyKey )
{
  QgsDebugMsg( "current properties:" );
  topQgsPropertyKey.dump();
}


void _getProperties( const QDomDocument &doc, QgsProjectPropertyKey &project_properties )
{
  QDomElement propertiesElem = doc.documentElement().firstChildElement( QStringLiteral( "properties" ) );

  if ( propertiesElem.isNull() )  // no properties found, so we're done
  {
    return;
  }

  QDomNodeList scopes = propertiesElem.childNodes();

  if ( scopes.count() < 1 )
  {
    QgsDebugMsg( "empty ``properties'' XML tag ... bailing" );
    return;
  }

  if ( ! project_properties.readXml( propertiesElem ) )
  {
    QgsDebugMsg( "Project_properties.readXml() failed" );
  }
}


static void _getTitle( const QDomDocument &doc, QString &title )
{
  QDomNodeList nl = doc.elementsByTagName( QStringLiteral( "title" ) );

  title.clear();               // by default the title will be empty

  if ( !nl.count() )
  {
    QgsDebugMsg( "unable to find title element" );
    return;
  }

  QDomNode titleNode = nl.item( 0 );  // there should only be one, so zeroth element OK

  if ( !titleNode.hasChildNodes() ) // if not, then there's no actual text
  {
    QgsDebugMsg( "unable to find title element" );
    return;
  }

  QDomNode titleTextNode = titleNode.firstChild();  // should only have one child

  if ( !titleTextNode.isText() )
  {
    QgsDebugMsg( "unable to find title element" );
    return;
  }

  QDomText titleText = titleTextNode.toText();

  title = titleText.data();

}

QgsProjectVersion getVersion( const QDomDocument &doc )
{
  QDomNodeList nl = doc.elementsByTagName( QStringLiteral( "qgis" ) );

  if ( !nl.count() )
  {
    QgsDebugMsg( " unable to find qgis element in project file" );
    return QgsProjectVersion( 0, 0, 0, QString() );
  }

  QDomNode qgisNode = nl.item( 0 );  // there should only be one, so zeroth element OK

  QDomElement qgisElement = qgisNode.toElement(); // qgis node should be element
  QgsProjectVersion projectVersion( qgisElement.attribute( QStringLiteral( "version" ) ) );
  return projectVersion;
}


QgsSnappingConfig QgsProject::snappingConfig() const
{
  return mSnappingConfig;
}

void QgsProject::setSnappingConfig( const QgsSnappingConfig &snappingConfig )
{
  if ( mSnappingConfig == snappingConfig )
    return;

  mSnappingConfig = snappingConfig;
  setDirty();
  emit snappingConfigChanged( mSnappingConfig );
}

bool QgsProject::_getMapLayers( const QDomDocument &doc, QList<QDomNode> &brokenNodes )
{
  // Layer order is set by the restoring the legend settings from project file.
  // This is done on the 'readProject( ... )' signal

  QDomNodeList nl = doc.elementsByTagName( QStringLiteral( "maplayer" ) );

  // process the map layer nodes

  if ( 0 == nl.count() )      // if we have no layers to process, bail
  {
    return true; // Decided to return "true" since it's
    // possible for there to be a project with no
    // layers; but also, more imporantly, this
    // would cause the tests/qgsproject to fail
    // since the test suite doesn't currently
    // support test layers
  }

  bool returnStatus = true;

  emit layerLoaded( 0, nl.count() );

  // order layers based on their dependencies
  QgsLayerDefinition::DependencySorter depSorter( doc );
  if ( depSorter.hasCycle() || depSorter.hasMissingDependency() )
    return false;

  QVector<QDomNode> sortedLayerNodes = depSorter.sortedLayerNodes();

  int i = 0;
  Q_FOREACH ( const QDomNode &node, sortedLayerNodes )
  {
    QDomElement element = node.toElement();

    QString name = node.namedItem( QStringLiteral( "layername" ) ).toElement().text();
    if ( !name.isNull() )
      emit loadingLayer( tr( "Loading layer %1" ).arg( name ) );

    if ( element.attribute( QStringLiteral( "embedded" ) ) == QLatin1String( "1" ) )
    {
      createEmbeddedLayer( element.attribute( QStringLiteral( "id" ) ), readPath( element.attribute( QStringLiteral( "project" ) ) ), brokenNodes );
      continue;
    }
    else
    {
      QgsReadWriteContext context;
      context.setPathResolver( pathResolver() );
      if ( !addLayer( element, brokenNodes, context ) )
      {
        returnStatus = false;
      }
      const auto messages = context.takeMessages();
      if ( messages.count() )
      {
        emit loadingLayerMessageReceived( tr( "Loading layer %1" ).arg( name ), messages );
      }
    }
    emit layerLoaded( i + 1, nl.count() );
    i++;
  }

  return returnStatus;
}

bool QgsProject::addLayer( const QDomElement &layerElem, QList<QDomNode> &brokenNodes, QgsReadWriteContext &context )
{
  QString type = layerElem.attribute( QStringLiteral( "type" ) );
  QgsDebugMsgLevel( "Layer type is " + type, 4 );
  QgsMapLayer *mapLayer = nullptr;

  if ( type == QLatin1String( "vector" ) )
  {
    mapLayer = new QgsVectorLayer;

    // apply specific settings to vector layer
    if ( QgsVectorLayer *vl = qobject_cast<QgsVectorLayer *>( mapLayer ) )
    {
      vl->setReadExtentFromXml( mTrustLayerMetadata );
    }
  }
  else if ( type == QLatin1String( "raster" ) )
  {
    mapLayer = new QgsRasterLayer;
  }
  else if ( type == QLatin1String( "mesh" ) )
  {
    mapLayer = new QgsMeshLayer;
  }
  else if ( type == QLatin1String( "plugin" ) )
  {
    QString typeName = layerElem.attribute( QStringLiteral( "name" ) );
    mapLayer = QgsApplication::pluginLayerRegistry()->createLayer( typeName );
  }

  if ( !mapLayer )
  {
    QgsDebugMsg( "Unable to create layer" );

    return false;
  }

  Q_CHECK_PTR( mapLayer ); // NOLINT

  // have the layer restore state that is stored in Dom node
  if ( mapLayer->readLayerXml( layerElem, context ) && mapLayer->isValid() )
  {
    emit readMapLayer( mapLayer, layerElem );

    QList<QgsMapLayer *> myLayers;
    myLayers << mapLayer;
    addMapLayers( myLayers );

    return true;
  }
  else
  {
    delete mapLayer;

    QgsDebugMsg( "Unable to load " + type + " layer" );
    brokenNodes.push_back( layerElem );
    return false;
  }
}

bool QgsProject::read( const QString &filename )
{
  mFile.setFileName( filename );

  return read();
}

bool QgsProject::read()
{
  QString filename = mFile.fileName();
  bool rc;

  if ( QgsProjectStorage *storage = projectStorage() )
  {
    QTemporaryFile inDevice;
    if ( !inDevice.open() )
    {
      setError( tr( "Unable to open %1" ).arg( inDevice.fileName() ) );
      return false;
    }

    QgsReadWriteContext context;
    if ( !storage->readProject( filename, &inDevice, context ) )
    {
      QString err = tr( "Unable to open %1" ).arg( filename );
      QList<QgsReadWriteContext::ReadWriteMessage> messages = context.takeMessages();
      if ( !messages.isEmpty() )
        err += QStringLiteral( "\n\n" ) + messages.last().message();
      setError( err );
      return false;
    }

    return unzip( inDevice.fileName() );  // calls setError() if returning false
  }

  if ( QgsZipUtils::isZipFile( mFile.fileName() ) )
  {
    rc = unzip( mFile.fileName() );
  }
  else
  {
    mAuxiliaryStorage.reset( new QgsAuxiliaryStorage( *this ) );
    rc = readProjectFile( mFile.fileName() );
  }

  mFile.setFileName( filename );
  return rc;
}

bool QgsProject::readProjectFile( const QString &filename )
{
  QFile projectFile( filename );
  clearError();

  std::unique_ptr<QDomDocument> doc( new QDomDocument( QStringLiteral( "qgis" ) ) );

  if ( !projectFile.open( QIODevice::ReadOnly | QIODevice::Text ) )
  {
    projectFile.close();

    setError( tr( "Unable to open %1" ).arg( projectFile.fileName() ) );

    return false;
  }

  // location of problem associated with errorMsg
  int line, column;
  QString errorMsg;

  if ( !doc->setContent( &projectFile, &errorMsg, &line, &column ) )
  {
    // want to make this class as GUI independent as possible; so commented out
#if 0
    QMessageBox::critical( 0, tr( "Read Project File" ),
                           tr( "%1 at line %2 column %3" ).arg( errorMsg ).arg( line ).arg( column ) );
#endif

    QString errorString = tr( "Project file read error in file %1: %2 at line %3 column %4" )
                          .arg( projectFile.fileName(), errorMsg ).arg( line ).arg( column );

    QgsDebugMsg( errorString );

    projectFile.close();

    setError( tr( "%1 for file %2" ).arg( errorString, projectFile.fileName() ) );

    return false;
  }

  projectFile.close();


  QgsDebugMsg( "Opened document " + projectFile.fileName() );

  // get project version string, if any
  QgsProjectVersion fileVersion = getVersion( *doc );
  QgsProjectVersion thisVersion( Qgis::QGIS_VERSION );

  if ( thisVersion > fileVersion )
  {
    QgsLogger::warning( "Loading a file that was saved with an older "
                        "version of qgis (saved in " + fileVersion.text() +
                        ", loaded in " + Qgis::QGIS_VERSION +
                        "). Problems may occur." );

    QgsProjectFileTransform projectFile( *doc, fileVersion );

    // Shows a warning when an old project file is read.
    emit oldProjectVersionWarning( fileVersion.text() );
    QgsDebugMsg( "Emitting oldProjectVersionWarning(oldVersion)." );

    projectFile.updateRevision( thisVersion );
  }

  // start new project, just keep the file name and auxiliary storage
  QString fileName = mFile.fileName();
  std::unique_ptr<QgsAuxiliaryStorage> aStorage = std::move( mAuxiliaryStorage );
  clear();
  mAuxiliaryStorage = std::move( aStorage );
  mFile.setFileName( fileName );

  // now get any properties
  _getProperties( *doc, mProperties );

  QgsDebugMsg( QString::number( mProperties.count() ) + " properties read" );

  dump_( mProperties );

  // get older style project title
  QString oldTitle;
  _getTitle( *doc, oldTitle );

  QDomNodeList homePathNl = doc->elementsByTagName( QStringLiteral( "homePath" ) );
  if ( homePathNl.count() > 0 )
  {
    QDomElement homePathElement = homePathNl.at( 0 ).toElement();
    QString homePath = homePathElement.attribute( QStringLiteral( "path" ) );
    if ( !homePath.isEmpty() )
      setPresetHomePath( homePath );
  }
  else
  {
    emit homePathChanged();
  }

  QgsReadWriteContext context;
  context.setPathResolver( pathResolver() );

  //crs
  QgsCoordinateReferenceSystem projectCrs;
  if ( readNumEntry( QStringLiteral( "SpatialRefSys" ), QStringLiteral( "/ProjectionsEnabled" ), 0 ) )
  {
    // first preference - dedicated projectCrs node
    QDomNode srsNode = doc->documentElement().namedItem( QStringLiteral( "projectCrs" ) );
    if ( !srsNode.isNull() )
    {
      projectCrs.readXml( srsNode );
    }

    if ( !projectCrs.isValid() )
    {
      QString projCrsString = readEntry( QStringLiteral( "SpatialRefSys" ), QStringLiteral( "/ProjectCRSProj4String" ) );
      long currentCRS = readNumEntry( QStringLiteral( "SpatialRefSys" ), QStringLiteral( "/ProjectCRSID" ), -1 );

      // try the CRS
      if ( currentCRS >= 0 )
      {
        projectCrs = QgsCoordinateReferenceSystem::fromSrsId( currentCRS );
      }

      // if that didn't produce a match, try the proj.4 string
      if ( !projCrsString.isEmpty() && ( !projectCrs.isValid() || projectCrs.toProj4() != projCrsString ) )
      {
        projectCrs = QgsCoordinateReferenceSystem::fromProj4( projCrsString );
      }

      // last just take the given id
      if ( !projectCrs.isValid() )
      {
        projectCrs = QgsCoordinateReferenceSystem::fromSrsId( currentCRS );
      }
    }
  }
  mCrs = projectCrs;

  QStringList datumErrors;
  if ( !mTransformContext.readXml( doc->documentElement(), context, datumErrors ) )
  {
    emit missingDatumTransforms( datumErrors );
  }
  emit transformContextChanged();

  QDomNodeList nl = doc->elementsByTagName( QStringLiteral( "projectMetadata" ) );
  if ( !nl.isEmpty() )
  {
    QDomElement metadataElement = nl.at( 0 ).toElement();
    mMetadata.readMetadataXml( metadataElement );
  }
  else
  {
    // older project, no metadata => remove auto generated metadata which is populated on QgsProject::clear()
    mMetadata = QgsProjectMetadata();
  }
  if ( mMetadata.title().isEmpty() && !oldTitle.isEmpty() )
  {
    // upgrade older title storage to storing within project metadata.
    mMetadata.setTitle( oldTitle );
  }
  emit metadataChanged();

  nl = doc->elementsByTagName( QStringLiteral( "autotransaction" ) );
  if ( nl.count() )
  {
    QDomElement transactionElement = nl.at( 0 ).toElement();
    if ( transactionElement.attribute( QStringLiteral( "active" ), QStringLiteral( "0" ) ).toInt() == 1 )
      mAutoTransaction = true;
  }

  nl = doc->elementsByTagName( QStringLiteral( "evaluateDefaultValues" ) );
  if ( nl.count() )
  {
    QDomElement evaluateDefaultValuesElement = nl.at( 0 ).toElement();
    if ( evaluateDefaultValuesElement.attribute( QStringLiteral( "active" ), QStringLiteral( "0" ) ).toInt() == 1 )
      mEvaluateDefaultValues = true;
  }

  nl = doc->elementsByTagName( QStringLiteral( "trust" ) );
  if ( nl.count() )
  {
    QDomElement trustElement = nl.at( 0 ).toElement();
    if ( trustElement.attribute( QStringLiteral( "active" ), QStringLiteral( "0" ) ).toInt() == 1 )
      mTrustLayerMetadata = true;
  }

  // read the layer tree from project file

  mRootGroup->setCustomProperty( QStringLiteral( "loading" ), 1 );

  QDomElement layerTreeElem = doc->documentElement().firstChildElement( QStringLiteral( "layer-tree-group" ) );
  if ( !layerTreeElem.isNull() )
  {
    mRootGroup->readChildrenFromXml( layerTreeElem, context );
  }
  else
  {
    QgsLayerTreeUtils::readOldLegend( mRootGroup, doc->documentElement().firstChildElement( QStringLiteral( "legend" ) ) );
  }

  mLayerTreeRegistryBridge->setEnabled( false );

  // get the map layers
  QList<QDomNode> brokenNodes;
  bool clean = _getMapLayers( *doc, brokenNodes );

  // review the integrity of the retrieved map layers
  if ( !clean )
  {
    QgsDebugMsg( "Unable to get map layers from project file." );

    if ( !brokenNodes.isEmpty() )
    {
      QgsDebugMsg( "there are " + QString::number( brokenNodes.size() ) + " broken layers" );
    }

    // we let a custom handler decide what to do with missing layers
    // (default implementation ignores them, there's also a GUI handler that lets user choose correct path)
    mBadLayerHandler->handleBadLayers( brokenNodes );
  }

  // Resolve references to other layers
  // Needs to be done here once all dependent layers are loaded
  QMap<QString, QgsMapLayer *> layers = mLayerStore->mapLayers();
  for ( QMap<QString, QgsMapLayer *>::iterator it = layers.begin(); it != layers.end(); it++ )
  {
    it.value()->resolveReferences( this );
  }

  mLayerTreeRegistryBridge->setEnabled( true );

  // load embedded groups and layers
  loadEmbeddedNodes( mRootGroup );

  // now that layers are loaded, we can resolve layer tree's references to the layers
  mRootGroup->resolveReferences( this );


  if ( !layerTreeElem.isNull() )
  {
    mRootGroup->readLayerOrderFromXml( layerTreeElem );
  }

  // Load pre 3.0 configuration
  QDomElement layerTreeCanvasElem = doc->documentElement().firstChildElement( QStringLiteral( "layer-tree-canvas" ) );
  if ( !layerTreeCanvasElem.isNull( ) )
  {
    mRootGroup->readLayerOrderFromXml( layerTreeCanvasElem );
  }

  // make sure the are just valid layers
  QgsLayerTreeUtils::removeInvalidLayers( mRootGroup );

  mRootGroup->removeCustomProperty( QStringLiteral( "loading" ) );

  mMapThemeCollection.reset( new QgsMapThemeCollection( this ) );
  emit mapThemeCollectionChanged();
  mMapThemeCollection->readXml( *doc );

  mLabelingEngineSettings->readSettingsFromProject( this );
  emit labelingEngineSettingsChanged();

  mAnnotationManager->readXml( doc->documentElement(), context );
  mLayoutManager->readXml( doc->documentElement(), *doc );

  // reassign change dependencies now that all layers are loaded
  QMap<QString, QgsMapLayer *> existingMaps = mapLayers();
  for ( QMap<QString, QgsMapLayer *>::iterator it = existingMaps.begin(); it != existingMaps.end(); it++ )
  {
    it.value()->setDependencies( it.value()->dependencies() );
  }

  mSnappingConfig.readProject( *doc );

  //add variables defined in project file
  QStringList variableNames = readListEntry( QStringLiteral( "Variables" ), QStringLiteral( "/variableNames" ) );
  QStringList variableValues = readListEntry( QStringLiteral( "Variables" ), QStringLiteral( "/variableValues" ) );

  mCustomVariables.clear();
  if ( variableNames.length() == variableValues.length() )
  {
    for ( int i = 0; i < variableNames.length(); ++i )
    {
      mCustomVariables.insert( variableNames.at( i ), variableValues.at( i ) );
    }
  }
  else
  {
    QgsMessageLog::logMessage( tr( "Project Variables Invalid" ), tr( "The project contains invalid variable settings." ) );
  }
  emit customVariablesChanged();
  emit crsChanged();
  emit ellipsoidChanged( ellipsoid() );

  // read the project: used by map canvas and legend
  emit readProject( *doc );
  emit snappingConfigChanged( mSnappingConfig );

  // if all went well, we're allegedly in pristine state
  if ( clean )
    setDirty( false );

  emit nonIdentifiableLayersChanged( nonIdentifiableLayers() );

  return true;
}


void QgsProject::loadEmbeddedNodes( QgsLayerTreeGroup *group )
{

  Q_FOREACH ( QgsLayerTreeNode *child, group->children() )
  {
    if ( QgsLayerTree::isGroup( child ) )
    {
      QgsLayerTreeGroup *childGroup = QgsLayerTree::toGroup( child );
      if ( childGroup->customProperty( QStringLiteral( "embedded" ) ).toInt() )
      {
        // make sure to convert the path from relative to absolute
        QString projectPath = readPath( childGroup->customProperty( QStringLiteral( "embedded_project" ) ).toString() );
        childGroup->setCustomProperty( QStringLiteral( "embedded_project" ), projectPath );
        QgsLayerTreeGroup *newGroup = createEmbeddedGroup( childGroup->name(), projectPath, childGroup->customProperty( QStringLiteral( "embedded-invisible-layers" ) ).toStringList() );
        if ( newGroup )
        {
          QList<QgsLayerTreeNode *> clonedChildren;
          Q_FOREACH ( QgsLayerTreeNode *newGroupChild, newGroup->children() )
            clonedChildren << newGroupChild->clone();
          delete newGroup;

          childGroup->insertChildNodes( 0, clonedChildren );
        }
      }
      else
      {
        loadEmbeddedNodes( childGroup );
      }
    }
    else if ( QgsLayerTree::isLayer( child ) )
    {
      if ( child->customProperty( QStringLiteral( "embedded" ) ).toInt() )
      {
        QList<QDomNode> brokenNodes;
        createEmbeddedLayer( QgsLayerTree::toLayer( child )->layerId(), child->customProperty( QStringLiteral( "embedded_project" ) ).toString(), brokenNodes );
      }
    }

  }
}

QVariantMap QgsProject::customVariables() const
{
  return mCustomVariables;
}

void QgsProject::setCustomVariables( const QVariantMap &variables )
{
  if ( variables == mCustomVariables )
    return;

  //write variable to project
  QStringList variableNames;
  QStringList variableValues;

  QVariantMap::const_iterator it = variables.constBegin();
  for ( ; it != variables.constEnd(); ++it )
  {
    variableNames << it.key();
    variableValues << it.value().toString();
  }

  writeEntry( QStringLiteral( "Variables" ), QStringLiteral( "/variableNames" ), variableNames );
  writeEntry( QStringLiteral( "Variables" ), QStringLiteral( "/variableValues" ), variableValues );

  mCustomVariables = variables;

  emit customVariablesChanged();
}

void QgsProject::setLabelingEngineSettings( const QgsLabelingEngineSettings &settings )
{
  *mLabelingEngineSettings = settings;
  emit labelingEngineSettingsChanged();
}

const QgsLabelingEngineSettings &QgsProject::labelingEngineSettings() const
{
  return *mLabelingEngineSettings;
}

QgsMapLayerStore *QgsProject::layerStore()
{
  return mLayerStore.get();
}

const QgsMapLayerStore *QgsProject::layerStore() const
{
  return mLayerStore.get();
}

QList<QgsVectorLayer *> QgsProject::avoidIntersectionsLayers() const
{
  QList<QgsVectorLayer *> layers;
  QStringList layerIds = readListEntry( QStringLiteral( "Digitizing" ), QStringLiteral( "/AvoidIntersectionsList" ), QStringList() );
  Q_FOREACH ( const QString &layerId, layerIds )
  {
    if ( QgsVectorLayer *vlayer = qobject_cast<QgsVectorLayer *>( mapLayer( layerId ) ) )
      layers << vlayer;
  }
  return layers;
}

void QgsProject::setAvoidIntersectionsLayers( const QList<QgsVectorLayer *> &layers )
{
  QStringList list;
  Q_FOREACH ( QgsVectorLayer *layer, layers )
    list << layer->id();
  writeEntry( QStringLiteral( "Digitizing" ), QStringLiteral( "/AvoidIntersectionsList" ), list );
  emit avoidIntersectionsLayersChanged();
}

QgsExpressionContext QgsProject::createExpressionContext() const
{
  QgsExpressionContext context;

  context << QgsExpressionContextUtils::globalScope()
          << QgsExpressionContextUtils::projectScope( this );

  return context;
}

void QgsProject::onMapLayersAdded( const QList<QgsMapLayer *> &layers )
{
  QMap<QString, QgsMapLayer *> existingMaps = mapLayers();

  bool tgChanged = false;

  Q_FOREACH ( QgsMapLayer *layer, layers )
  {
    QgsVectorLayer *vlayer = qobject_cast<QgsVectorLayer *>( layer );
    if ( vlayer )
    {
      if ( autoTransaction() )
      {
        if ( QgsTransaction::supportsTransaction( vlayer ) )
        {
          QString connString = QgsDataSourceUri( vlayer->source() ).connectionInfo();
          QString key = vlayer->providerType();

          QgsTransactionGroup *tg = mTransactionGroups.value( qMakePair( key, connString ) );

          if ( !tg )
          {
            tg = new QgsTransactionGroup();
            mTransactionGroups.insert( qMakePair( key, connString ), tg );
            tgChanged = true;
          }
          tg->addLayer( vlayer );
        }
      }
      vlayer->dataProvider()->setProviderProperty( QgsVectorDataProvider::EvaluateDefaultValues, evaluateDefaultValues() );
    }

    if ( tgChanged )
      emit transactionGroupsChanged();

    connect( layer, &QgsMapLayer::configChanged, this, [ = ] { setDirty(); } );

    // check if we have to update connections for layers with dependencies
    for ( QMap<QString, QgsMapLayer *>::iterator it = existingMaps.begin(); it != existingMaps.end(); it++ )
    {
      QSet<QgsMapLayerDependency> deps = it.value()->dependencies();
      if ( deps.contains( layer->id() ) )
      {
        // reconnect to change signals
        it.value()->setDependencies( deps );
      }
    }
  }

  if ( mSnappingConfig.addLayers( layers ) )
    emit snappingConfigChanged( mSnappingConfig );
}

void QgsProject::onMapLayersRemoved( const QList<QgsMapLayer *> &layers )
{
  if ( mSnappingConfig.removeLayers( layers ) )
    emit snappingConfigChanged( mSnappingConfig );
}

void QgsProject::cleanTransactionGroups( bool force )
{
  bool changed = false;
  for ( QMap< QPair< QString, QString>, QgsTransactionGroup *>::Iterator tg = mTransactionGroups.begin(); tg != mTransactionGroups.end(); )
  {
    if ( tg.value()->isEmpty() || force )
    {
      delete tg.value();
      tg = mTransactionGroups.erase( tg );
      changed = true;
    }
    else
    {
      ++tg;
    }
  }
  if ( changed )
    emit transactionGroupsChanged();
}

bool QgsProject::readLayer( const QDomNode &layerNode )
{
  QgsReadWriteContext context;
  context.setPathResolver( pathResolver() );
  QList<QDomNode> brokenNodes;
  if ( addLayer( layerNode.toElement(), brokenNodes, context ) )
  {
    // have to try to update joins for all layers now - a previously added layer may be dependent on this newly
    // added layer for joins
    QVector<QgsVectorLayer *> vectorLayers = layers<QgsVectorLayer *>();
    Q_FOREACH ( QgsVectorLayer *layer, vectorLayers )
    {
      // TODO: should be only done later - and with all layers (other layers may have referenced this layer)
      layer->resolveReferences( this );
    }

    return true;
  }
  return false;
}

bool QgsProject::write( const QString &filename )
{
  mFile.setFileName( filename );

  return write();
}

bool QgsProject::write()
{
  if ( QgsProjectStorage *storage = projectStorage() )
  {
    // for projects stored in a custom storage, we cannot use relative paths since the storage most likely
    // will not be in a file system
    writeEntry( QStringLiteral( "Paths" ), QStringLiteral( "/Absolute" ), true );

    QString tempPath = QStandardPaths::standardLocations( QStandardPaths::TempLocation ).at( 0 );
    QString tmpZipFilename( tempPath + QDir::separator() + QUuid::createUuid().toString() );

    if ( !zip( tmpZipFilename ) )
      return false;  // zip() already calls setError() when returning false

    QFile tmpZipFile( tmpZipFilename );
    if ( !tmpZipFile.open( QIODevice::ReadOnly ) )
    {
      setError( tr( "Unable to read file %1" ).arg( tmpZipFilename ) );
      return false;
    }

    QgsReadWriteContext context;
    if ( !storage->writeProject( mFile.fileName(), &tmpZipFile, context ) )
    {
      QString err = tr( "Unable to save project to storage %1" ).arg( mFile.fileName() );
      QList<QgsReadWriteContext::ReadWriteMessage> messages = context.takeMessages();
      if ( !messages.isEmpty() )
        err += QStringLiteral( "\n\n" ) + messages.last().message();
      setError( err );
      return false;
    }

    tmpZipFile.close();
    QFile::remove( tmpZipFilename );

    return true;
  }

  if ( QgsZipUtils::isZipFile( mFile.fileName() ) )
  {
    return zip( mFile.fileName() );
  }
  else
  {
    // write project file even if the auxiliary storage is not correctly
    // saved
    const bool asOk = saveAuxiliaryStorage();
    const bool writeOk = writeProjectFile( mFile.fileName() );

    // errors raised during writing project file are more important
    if ( !asOk && writeOk )
      setError( tr( "Unable to save auxiliary storage" ) );

    return asOk && writeOk;
  }
}

bool QgsProject::writeProjectFile( const QString &filename )
{
  QFile projectFile( filename );
  clearError();

  // if we have problems creating or otherwise writing to the project file,
  // let's find out up front before we go through all the hand-waving
  // necessary to create all the Dom objects
  QFileInfo myFileInfo( projectFile );
  if ( myFileInfo.exists() && !myFileInfo.isWritable() )
  {
    setError( tr( "%1 is not writable. Please adjust permissions (if possible) and try again." )
              .arg( projectFile.fileName() ) );
    return false;
  }

  QgsReadWriteContext context;
  context.setPathResolver( pathResolver() );

  QDomImplementation DomImplementation;
  DomImplementation.setInvalidDataPolicy( QDomImplementation::DropInvalidChars );

  QDomDocumentType documentType =
    DomImplementation.createDocumentType( QStringLiteral( "qgis" ), QStringLiteral( "http://mrcc.com/qgis.dtd" ),
                                          QStringLiteral( "SYSTEM" ) );
  std::unique_ptr<QDomDocument> doc( new QDomDocument( documentType ) );

  QDomElement qgisNode = doc->createElement( QStringLiteral( "qgis" ) );
  qgisNode.setAttribute( QStringLiteral( "projectname" ), title() );
  qgisNode.setAttribute( QStringLiteral( "version" ), QStringLiteral( "%1" ).arg( Qgis::QGIS_VERSION ) );

  doc->appendChild( qgisNode );

  QDomElement homePathNode = doc->createElement( QStringLiteral( "homePath" ) );
  homePathNode.setAttribute( QStringLiteral( "path" ), mHomePath );
  qgisNode.appendChild( homePathNode );

  // title
  QDomElement titleNode = doc->createElement( QStringLiteral( "title" ) );
  qgisNode.appendChild( titleNode );

  QDomElement transactionNode = doc->createElement( QStringLiteral( "autotransaction" ) );
  transactionNode.setAttribute( QStringLiteral( "active" ), mAutoTransaction ? "1" : "0" );
  qgisNode.appendChild( transactionNode );

  QDomElement evaluateDefaultValuesNode = doc->createElement( QStringLiteral( "evaluateDefaultValues" ) );
  evaluateDefaultValuesNode.setAttribute( QStringLiteral( "active" ), mEvaluateDefaultValues ? "1" : "0" );
  qgisNode.appendChild( evaluateDefaultValuesNode );

  QDomElement trustNode = doc->createElement( QStringLiteral( "trust" ) );
  trustNode.setAttribute( QStringLiteral( "active" ), mTrustLayerMetadata ? "1" : "0" );
  qgisNode.appendChild( trustNode );

  QDomText titleText = doc->createTextNode( title() );  // XXX why have title TWICE?
  titleNode.appendChild( titleText );

  // write project CRS
  QDomElement srsNode = doc->createElement( QStringLiteral( "projectCrs" ) );
  mCrs.writeXml( srsNode, *doc );
  qgisNode.appendChild( srsNode );

  // write layer tree - make sure it is without embedded subgroups
  QgsLayerTreeNode *clonedRoot = mRootGroup->clone();
  QgsLayerTreeUtils::replaceChildrenOfEmbeddedGroups( QgsLayerTree::toGroup( clonedRoot ) );
  QgsLayerTreeUtils::updateEmbeddedGroupsProjectPath( QgsLayerTree::toGroup( clonedRoot ), this ); // convert absolute paths to relative paths if required

  clonedRoot->writeXml( qgisNode, context );
  delete clonedRoot;

  mSnappingConfig.writeProject( *doc );

  // let map canvas and legend write their information
  emit writeProject( *doc );

  // within top level node save list of layers
  const QMap<QString, QgsMapLayer *> &layers = mapLayers();

  // Iterate over layers in zOrder
  // Call writeXml() on each
  QDomElement projectLayersNode = doc->createElement( QStringLiteral( "projectlayers" ) );

  QMap<QString, QgsMapLayer *>::ConstIterator li = layers.constBegin();
  while ( li != layers.end() )
  {
    QgsMapLayer *ml = li.value();

    if ( ml )
    {
      QHash< QString, QPair< QString, bool> >::const_iterator emIt = mEmbeddedLayers.constFind( ml->id() );
      if ( emIt == mEmbeddedLayers.constEnd() )
      {
        // general layer metadata
        QDomElement maplayerElem = doc->createElement( QStringLiteral( "maplayer" ) );

        ml->writeLayerXml( maplayerElem, *doc, context );

        emit writeMapLayer( ml, maplayerElem, *doc );

        projectLayersNode.appendChild( maplayerElem );
      }
      else
      {
        // layer defined in an external project file
        // only save embedded layer if not managed by a legend group
        if ( emIt.value().second )
        {
          QDomElement mapLayerElem = doc->createElement( QStringLiteral( "maplayer" ) );
          mapLayerElem.setAttribute( QStringLiteral( "embedded" ), 1 );
          mapLayerElem.setAttribute( QStringLiteral( "project" ), writePath( emIt.value().first ) );
          mapLayerElem.setAttribute( QStringLiteral( "id" ), ml->id() );
          projectLayersNode.appendChild( mapLayerElem );
        }
      }
    }
    li++;
  }

  qgisNode.appendChild( projectLayersNode );

  QDomElement layerOrderNode = doc->createElement( QStringLiteral( "layerorder" ) );
  Q_FOREACH ( QgsMapLayer *layer, mRootGroup->customLayerOrder() )
  {
    QDomElement mapLayerElem = doc->createElement( QStringLiteral( "layer" ) );
    mapLayerElem.setAttribute( QStringLiteral( "id" ), layer->id() );
    layerOrderNode.appendChild( mapLayerElem );
  }
  qgisNode.appendChild( layerOrderNode );

  mLabelingEngineSettings->writeSettingsToProject( this );

  // now add the optional extra properties

  dump_( mProperties );

  QgsDebugMsg( QString( "there are %1 property scopes" ).arg( static_cast<int>( mProperties.count() ) ) );

  if ( !mProperties.isEmpty() ) // only worry about properties if we
    // actually have any properties
  {
    mProperties.writeXml( QStringLiteral( "properties" ), qgisNode, *doc );
  }

  mMapThemeCollection->writeXml( *doc );

  mTransformContext.writeXml( qgisNode, context );

  QDomElement metadataElem = doc->createElement( QStringLiteral( "projectMetadata" ) );
  mMetadata.writeMetadataXml( metadataElem, *doc );
  qgisNode.appendChild( metadataElem );

  QDomElement annotationsElem = mAnnotationManager->writeXml( *doc, context );
  qgisNode.appendChild( annotationsElem );

  QDomElement layoutElem = mLayoutManager->writeXml( *doc );
  qgisNode.appendChild( layoutElem );

  // now wrap it up and ship it to the project file
  doc->normalize();             // XXX I'm not entirely sure what this does

  // Create backup file
  if ( QFile::exists( fileName() ) )
  {
    QFile backupFile( QStringLiteral( "%1~" ).arg( filename ) );
    bool ok = true;
    ok &= backupFile.open( QIODevice::WriteOnly | QIODevice::Truncate );
    ok &= projectFile.open( QIODevice::ReadOnly );

    QByteArray ba;
    while ( ok && !projectFile.atEnd() )
    {
      ba = projectFile.read( 10240 );
      ok &= backupFile.write( ba ) == ba.size();
    }

    projectFile.close();
    backupFile.close();

    if ( !ok )
    {
      setError( tr( "Unable to create backup file %1" ).arg( backupFile.fileName() ) );
      return false;
    }

    QFileInfo fi( fileName() );
    struct utimbuf tb = { fi.lastRead().toTime_t(), fi.lastModified().toTime_t() };
    utime( backupFile.fileName().toUtf8().constData(), &tb );
  }

  if ( !projectFile.open( QIODevice::WriteOnly | QIODevice::Truncate ) )
  {
    projectFile.close();         // even though we got an error, let's make
    // sure it's closed anyway

    setError( tr( "Unable to save to file %1" ).arg( projectFile.fileName() ) );
    return false;
  }

  QTemporaryFile tempFile;
  bool ok = tempFile.open();
  if ( ok )
  {
    QTextStream projectFileStream( &tempFile );
    doc->save( projectFileStream, 2 );  // save as utf-8
    ok &= projectFileStream.pos() > -1;

    ok &= tempFile.seek( 0 );

    QByteArray ba;
    while ( ok && !tempFile.atEnd() )
    {
      ba = tempFile.read( 10240 );
      ok &= projectFile.write( ba ) == ba.size();
    }

    ok &= projectFile.error() == QFile::NoError;

    projectFile.close();
  }

  tempFile.close();

  if ( !ok )
  {
    setError( tr( "Unable to save to file %1. Your project "
                  "may be corrupted on disk. Try clearing some space on the volume and "
                  "check file permissions before pressing save again." )
              .arg( projectFile.fileName() ) );
    return false;
  }

  setDirty( false );               // reset to pristine state

  emit projectSaved();

  return true;
}

bool QgsProject::writeEntry( const QString &scope, QString const &key, bool value )
{
  setDirty( true );

  return addKey_( scope, key, &mProperties, value );
}

bool QgsProject::writeEntry( const QString &scope, const QString &key, double value )
{
  setDirty( true );

  return addKey_( scope, key, &mProperties, value );
}

bool QgsProject::writeEntry( const QString &scope, QString const &key, int value )
{
  setDirty( true );

  return addKey_( scope, key, &mProperties, value );
}

bool QgsProject::writeEntry( const QString &scope, const QString &key, const QString &value )
{
  setDirty( true );

  return addKey_( scope, key, &mProperties, value );
}

bool QgsProject::writeEntry( const QString &scope, const QString &key, const QStringList &value )
{
  setDirty( true );

  return addKey_( scope, key, &mProperties, value );
}

QStringList QgsProject::readListEntry( const QString &scope,
                                       const QString &key,
                                       const QStringList &def,
                                       bool *ok ) const
{
  QgsProjectProperty *property = findKey_( scope, key, mProperties );

  QVariant value;

  if ( property )
  {
    value = property->value();

    bool valid = QVariant::StringList == value.type();
    if ( ok )
      *ok = valid;

    if ( valid )
    {
      return value.toStringList();
    }
  }

  return def;
}


QString QgsProject::readEntry( const QString &scope,
                               const QString &key,
                               const QString &def,
                               bool *ok ) const
{
  QgsProjectProperty *property = findKey_( scope, key, mProperties );

  QVariant value;

  if ( property )
  {
    value = property->value();

    bool valid = value.canConvert( QVariant::String );
    if ( ok )
      *ok = valid;

    if ( valid )
      return value.toString();
  }

  return def;
}

int QgsProject::readNumEntry( const QString &scope, const QString &key, int def,
                              bool *ok ) const
{
  QgsProjectProperty *property = findKey_( scope, key, mProperties );

  QVariant value;

  if ( property )
  {
    value = property->value();
  }

  bool valid = value.canConvert( QVariant::Int );

  if ( ok )
  {
    *ok = valid;
  }

  if ( valid )
  {
    return value.toInt();
  }

  return def;
}

double QgsProject::readDoubleEntry( const QString &scope, const QString &key,
                                    double def,
                                    bool *ok ) const
{
  QgsProjectProperty *property = findKey_( scope, key, mProperties );
  if ( property )
  {
    QVariant value = property->value();

    bool valid = value.canConvert( QVariant::Double );
    if ( ok )
      *ok = valid;

    if ( valid )
      return value.toDouble();
  }

  return def;
}

bool QgsProject::readBoolEntry( const QString &scope, const QString &key, bool def,
                                bool *ok ) const
{
  QgsProjectProperty *property = findKey_( scope, key, mProperties );

  if ( property )
  {
    QVariant value = property->value();

    bool valid = value.canConvert( QVariant::Bool );
    if ( ok )
      *ok = valid;

    if ( valid )
      return value.toBool();
  }

  return def;
}


bool QgsProject::removeEntry( const QString &scope, const QString &key )
{
  removeKey_( scope, key, mProperties );

  setDirty( true );

  return !findKey_( scope, key, mProperties );
}


QStringList QgsProject::entryList( const QString &scope, const QString &key ) const
{
  QgsProjectProperty *foundProperty = findKey_( scope, key, mProperties );

  QStringList entries;

  if ( foundProperty )
  {
    QgsProjectPropertyKey *propertyKey = dynamic_cast<QgsProjectPropertyKey *>( foundProperty );

    if ( propertyKey )
    { propertyKey->entryList( entries ); }
  }

  return entries;
}

QStringList QgsProject::subkeyList( const QString &scope, const QString &key ) const
{
  QgsProjectProperty *foundProperty = findKey_( scope, key, mProperties );

  QStringList entries;

  if ( foundProperty )
  {
    QgsProjectPropertyKey *propertyKey = dynamic_cast<QgsProjectPropertyKey *>( foundProperty );

    if ( propertyKey )
    { propertyKey->subkeyList( entries ); }
  }

  return entries;
}

void QgsProject::dumpProperties() const
{
  dump_( mProperties );
}

QgsPathResolver QgsProject::pathResolver() const
{
  bool absolutePaths = readBoolEntry( QStringLiteral( "Paths" ), QStringLiteral( "/Absolute" ), false );
  return QgsPathResolver( absolutePaths ? QString() : fileName() );
}

QString QgsProject::readPath( const QString &src ) const
{
  return pathResolver().readPath( src );
}

QString QgsProject::writePath( const QString &src ) const
{
  return pathResolver().writePath( src );
}

void QgsProject::setError( const QString &errorMessage )
{
  mErrorMessage = errorMessage;
}

QString QgsProject::error() const
{
  return mErrorMessage;
}

void QgsProject::clearError()
{
  setError( QString() );
}

void QgsProject::setBadLayerHandler( QgsProjectBadLayerHandler *handler )
{
  delete mBadLayerHandler;
  mBadLayerHandler = handler;
}

QString QgsProject::layerIsEmbedded( const QString &id ) const
{
  QHash< QString, QPair< QString, bool > >::const_iterator it = mEmbeddedLayers.find( id );
  if ( it == mEmbeddedLayers.constEnd() )
  {
    return QString();
  }
  return it.value().first;
}

bool QgsProject::createEmbeddedLayer( const QString &layerId, const QString &projectFilePath, QList<QDomNode> &brokenNodes,
                                      bool saveFlag )
{
  QgsDebugCall;

  static QString sPrevProjectFilePath;
  static QDateTime sPrevProjectFileTimestamp;
  static QDomDocument sProjectDocument;

  QDateTime projectFileTimestamp = QFileInfo( projectFilePath ).lastModified();

  if ( projectFilePath != sPrevProjectFilePath || projectFileTimestamp != sPrevProjectFileTimestamp )
  {
    sPrevProjectFilePath.clear();

    QFile projectFile( projectFilePath );
    if ( !projectFile.open( QIODevice::ReadOnly ) )
    {
      return false;
    }

    if ( !sProjectDocument.setContent( &projectFile ) )
    {
      return false;
    }

    sPrevProjectFilePath = projectFilePath;
    sPrevProjectFileTimestamp = projectFileTimestamp;
  }

  // does project store paths absolute or relative?
  bool useAbsolutePaths = true;

  QDomElement propertiesElem = sProjectDocument.documentElement().firstChildElement( QStringLiteral( "properties" ) );
  if ( !propertiesElem.isNull() )
  {
    QDomElement absElem = propertiesElem.firstChildElement( QStringLiteral( "Paths" ) ).firstChildElement( QStringLiteral( "Absolute" ) );
    if ( !absElem.isNull() )
    {
      useAbsolutePaths = absElem.text().compare( QLatin1String( "true" ), Qt::CaseInsensitive ) == 0;
    }
  }

  QgsReadWriteContext embeddedContext;
  if ( !useAbsolutePaths )
    embeddedContext.setPathResolver( QgsPathResolver( projectFilePath ) );

  QDomElement projectLayersElem = sProjectDocument.documentElement().firstChildElement( QStringLiteral( "projectlayers" ) );
  if ( projectLayersElem.isNull() )
  {
    return false;
  }

  QDomNodeList mapLayerNodes = projectLayersElem.elementsByTagName( QStringLiteral( "maplayer" ) );
  for ( int i = 0; i < mapLayerNodes.size(); ++i )
  {
    // get layer id
    QDomElement mapLayerElem = mapLayerNodes.at( i ).toElement();
    QString id = mapLayerElem.firstChildElement( QStringLiteral( "id" ) ).text();
    if ( id == layerId )
    {
      // layer can be embedded only once
      if ( mapLayerElem.attribute( QStringLiteral( "embedded" ) ) == QLatin1String( "1" ) )
      {
        return false;
      }

      mEmbeddedLayers.insert( layerId, qMakePair( projectFilePath, saveFlag ) );

      if ( addLayer( mapLayerElem, brokenNodes, embeddedContext ) )
      {
        return true;
      }
      else
      {
        mEmbeddedLayers.remove( layerId );
        return false;
      }
    }
  }

  return false;
}


QgsLayerTreeGroup *QgsProject::createEmbeddedGroup( const QString &groupName, const QString &projectFilePath, const QStringList &invisibleLayers )
{
  // open project file, get layer ids in group, add the layers
  QFile projectFile( projectFilePath );
  if ( !projectFile.open( QIODevice::ReadOnly ) )
  {
    return nullptr;
  }

  QDomDocument projectDocument;
  if ( !projectDocument.setContent( &projectFile ) )
  {
    return nullptr;
  }

  QgsReadWriteContext context;
  context.setPathResolver( pathResolver() );

  // store identify disabled layers of the embedded project
  QSet<QString> embeddedIdentifyDisabledLayers;
  QDomElement disabledLayersElem = projectDocument.documentElement().firstChildElement( QStringLiteral( "properties" ) ).firstChildElement( QStringLiteral( "Identify" ) ).firstChildElement( QStringLiteral( "disabledLayers" ) );
  if ( !disabledLayersElem.isNull() )
  {
    QDomNodeList valueList = disabledLayersElem.elementsByTagName( QStringLiteral( "value" ) );
    for ( int i = 0; i < valueList.size(); ++i )
    {
      embeddedIdentifyDisabledLayers.insert( valueList.at( i ).toElement().text() );
    }
  }

  QgsLayerTreeGroup *root = new QgsLayerTreeGroup;

  QDomElement layerTreeElem = projectDocument.documentElement().firstChildElement( QStringLiteral( "layer-tree-group" ) );
  if ( !layerTreeElem.isNull() )
  {
    root->readChildrenFromXml( layerTreeElem, context );
  }
  else
  {
    QgsLayerTreeUtils::readOldLegend( root, projectDocument.documentElement().firstChildElement( QStringLiteral( "legend" ) ) );
  }

  QgsLayerTreeGroup *group = root->findGroup( groupName );
  if ( !group || group->customProperty( QStringLiteral( "embedded" ) ).toBool() )
  {
    // embedded groups cannot be embedded again
    delete root;
    return nullptr;
  }

  // clone the group sub-tree (it is used already in a tree, we cannot just tear it off)
  QgsLayerTreeGroup *newGroup = QgsLayerTree::toGroup( group->clone() );
  delete root;
  root = nullptr;

  newGroup->setCustomProperty( QStringLiteral( "embedded" ), 1 );
  newGroup->setCustomProperty( QStringLiteral( "embedded_project" ), projectFilePath );

  // set "embedded" to all children + load embedded layers
  mLayerTreeRegistryBridge->setEnabled( false );
  initializeEmbeddedSubtree( projectFilePath, newGroup );
  mLayerTreeRegistryBridge->setEnabled( true );

  QStringList thisProjectIdentifyDisabledLayers = nonIdentifiableLayers();

  // consider the layers might be identify disabled in its project
  Q_FOREACH ( const QString &layerId, newGroup->findLayerIds() )
  {
    if ( embeddedIdentifyDisabledLayers.contains( layerId ) )
    {
      thisProjectIdentifyDisabledLayers.append( layerId );
    }

    QgsLayerTreeLayer *layer = newGroup->findLayer( layerId );
    if ( layer )
    {
      layer->resolveReferences( this );
      layer->setItemVisibilityChecked( invisibleLayers.contains( layerId ) );
    }
  }

  setNonIdentifiableLayers( thisProjectIdentifyDisabledLayers );

  return newGroup;
}

void QgsProject::initializeEmbeddedSubtree( const QString &projectFilePath, QgsLayerTreeGroup *group )
{
  Q_FOREACH ( QgsLayerTreeNode *child, group->children() )
  {
    // all nodes in the subtree will have "embedded" custom property set
    child->setCustomProperty( QStringLiteral( "embedded" ), 1 );

    if ( QgsLayerTree::isGroup( child ) )
    {
      initializeEmbeddedSubtree( projectFilePath, QgsLayerTree::toGroup( child ) );
    }
    else if ( QgsLayerTree::isLayer( child ) )
    {
      // load the layer into our project
      QList<QDomNode> brokenNodes;
      createEmbeddedLayer( QgsLayerTree::toLayer( child )->layerId(), projectFilePath, brokenNodes, false );
    }
  }
}

bool QgsProject::evaluateDefaultValues() const
{
  return mEvaluateDefaultValues;
}

void QgsProject::setEvaluateDefaultValues( bool evaluateDefaultValues )
{
  const QMap<QString, QgsMapLayer *> layers = mapLayers();
  QMap<QString, QgsMapLayer *>::const_iterator layerIt = layers.constBegin();
  for ( ; layerIt != layers.constEnd(); ++layerIt )
  {
    QgsVectorLayer *vl = qobject_cast<QgsVectorLayer *>( layerIt.value() );
    if ( vl )
    {
      vl->dataProvider()->setProviderProperty( QgsVectorDataProvider::EvaluateDefaultValues, evaluateDefaultValues );
    }
  }

  mEvaluateDefaultValues = evaluateDefaultValues;
}

void QgsProject::setTopologicalEditing( bool enabled )
{
  writeEntry( QStringLiteral( "Digitizing" ), QStringLiteral( "/TopologicalEditing" ), ( enabled ? 1 : 0 ) );
  emit topologicalEditingChanged();
}

bool QgsProject::topologicalEditing() const
{
  return readNumEntry( QStringLiteral( "Digitizing" ), QStringLiteral( "/TopologicalEditing" ), 0 );
}

QgsUnitTypes::DistanceUnit QgsProject::distanceUnits() const
{
  QString distanceUnitString = readEntry( QStringLiteral( "Measurement" ), QStringLiteral( "/DistanceUnits" ), QString() );
  if ( !distanceUnitString.isEmpty() )
    return QgsUnitTypes::decodeDistanceUnit( distanceUnitString );

  //fallback to QGIS default measurement unit
  QgsSettings s;
  bool ok = false;
  QgsUnitTypes::DistanceUnit type = QgsUnitTypes::decodeDistanceUnit( s.value( QStringLiteral( "/qgis/measure/displayunits" ) ).toString(), &ok );
  return ok ? type : QgsUnitTypes::DistanceMeters;
}

void QgsProject::setDistanceUnits( QgsUnitTypes::DistanceUnit unit )
{
  writeEntry( QStringLiteral( "Measurement" ), QStringLiteral( "/DistanceUnits" ), QgsUnitTypes::encodeUnit( unit ) );
}

QgsUnitTypes::AreaUnit QgsProject::areaUnits() const
{
  QString areaUnitString = readEntry( QStringLiteral( "Measurement" ), QStringLiteral( "/AreaUnits" ), QString() );
  if ( !areaUnitString.isEmpty() )
    return QgsUnitTypes::decodeAreaUnit( areaUnitString );

  //fallback to QGIS default area unit
  QgsSettings s;
  bool ok = false;
  QgsUnitTypes::AreaUnit type = QgsUnitTypes::decodeAreaUnit( s.value( QStringLiteral( "/qgis/measure/areaunits" ) ).toString(), &ok );
  return ok ? type : QgsUnitTypes::AreaSquareMeters;
}

void QgsProject::setAreaUnits( QgsUnitTypes::AreaUnit unit )
{
  writeEntry( QStringLiteral( "Measurement" ), QStringLiteral( "/AreaUnits" ), QgsUnitTypes::encodeUnit( unit ) );
}

QString QgsProject::homePath() const
{
  if ( !mHomePath.isEmpty() )
  {
    QFileInfo homeInfo( mHomePath );
    if ( !homeInfo.isRelative() )
      return mHomePath;
  }

  QFileInfo pfi( fileName() );
  if ( !pfi.exists() )
    return mHomePath;

  if ( !mHomePath.isEmpty() )
  {
    // path is relative to project file
    return QDir::cleanPath( pfi.path() + '/' + mHomePath );
  }
  else
  {
    return pfi.canonicalPath();
  }
}

QString QgsProject::presetHomePath() const
{
  return mHomePath;
}

QgsRelationManager *QgsProject::relationManager() const
{
  return mRelationManager;
}

const QgsLayoutManager *QgsProject::layoutManager() const
{
  return mLayoutManager.get();
}

QgsLayoutManager *QgsProject::layoutManager()
{
  return mLayoutManager.get();
}

QgsLayerTree *QgsProject::layerTreeRoot() const
{
  return mRootGroup;
}

QgsMapThemeCollection *QgsProject::mapThemeCollection()
{
  return mMapThemeCollection.get();
}

QgsAnnotationManager *QgsProject::annotationManager()
{
  return mAnnotationManager.get();
}

const QgsAnnotationManager *QgsProject::annotationManager() const
{
  return mAnnotationManager.get();
}

void QgsProject::setNonIdentifiableLayers( const QList<QgsMapLayer *> &layers )
{
  QStringList currentLayers = nonIdentifiableLayers();

  QStringList newLayers;
  Q_FOREACH ( QgsMapLayer *l, layers )
  {
    newLayers << l->id();
  }

  if ( newLayers == currentLayers )
    return;

  QStringList disabledLayerIds;

  Q_FOREACH ( QgsMapLayer *l, layers )
  {
    disabledLayerIds << l->id();
  }

  setNonIdentifiableLayers( disabledLayerIds );
}

void QgsProject::setNonIdentifiableLayers( const QStringList &layerIds )
{
  writeEntry( QStringLiteral( "Identify" ), QStringLiteral( "/disabledLayers" ), layerIds );

  emit nonIdentifiableLayersChanged( layerIds );
}

QStringList QgsProject::nonIdentifiableLayers() const
{
  return readListEntry( QStringLiteral( "Identify" ), QStringLiteral( "/disabledLayers" ) );
}

bool QgsProject::autoTransaction() const
{
  return mAutoTransaction;
}

void QgsProject::setAutoTransaction( bool autoTransaction )
{
  if ( autoTransaction != mAutoTransaction )
  {
    mAutoTransaction = autoTransaction;

    if ( autoTransaction )
      onMapLayersAdded( mapLayers().values() );
    else
      cleanTransactionGroups( true );
  }
}

QMap<QPair<QString, QString>, QgsTransactionGroup *> QgsProject::transactionGroups()
{
  return mTransactionGroups;
}


//
// QgsMapLayerStore methods
//


int QgsProject::count() const
{
  return mLayerStore->count();
}

QgsMapLayer *QgsProject::mapLayer( const QString &layerId ) const
{
  return mLayerStore->mapLayer( layerId );
}

QList<QgsMapLayer *> QgsProject::mapLayersByName( const QString &layerName ) const
{
  return mLayerStore->mapLayersByName( layerName );
}

bool QgsProject::unzip( const QString &filename )
{
  clearError();
  std::unique_ptr<QgsProjectArchive> archive( new QgsProjectArchive() );

  // unzip the archive
  if ( !archive->unzip( filename ) )
  {
    setError( tr( "Unable to unzip file '%1'" ).arg( filename ) );
    return false;
  }

  // test if zip provides a .qgs file
  if ( archive->projectFile().isEmpty() )
  {
    setError( tr( "Zip archive does not provide a project file" ) );
    return false;
  }

  // load auxiliary storage
  if ( !archive->auxiliaryStorageFile().isEmpty() )
  {
    // database file is already a copy as it's been unzipped. So we don't open
    // auxiliary storage in copy mode in this case
    mAuxiliaryStorage.reset( new QgsAuxiliaryStorage( archive->auxiliaryStorageFile(), false ) );
  }
  else
  {
    mAuxiliaryStorage.reset( new QgsAuxiliaryStorage( *this ) );
  }

  // read the project file
  if ( ! readProjectFile( archive->projectFile() ) )
  {
    setError( tr( "Cannot read unzipped qgs project file" ) );
    return false;
  }

  // keep the archive and remove the temporary .qgs file
  mArchive = std::move( archive );
  mArchive->clearProjectFile();

  return true;
}

bool QgsProject::zip( const QString &filename )
{
  clearError();

  // save the current project in a temporary .qgs file
  std::unique_ptr<QgsProjectArchive> archive( new QgsProjectArchive() );
  const QString baseName = QFileInfo( filename ).baseName();
  const QString qgsFileName = QStringLiteral( "%1.qgs" ).arg( baseName );
  QFile qgsFile( QDir( archive->dir() ).filePath( qgsFileName ) );

  bool writeOk = false;
  if ( qgsFile.open( QIODevice::WriteOnly | QIODevice::Truncate ) )
  {
    writeOk = writeProjectFile( qgsFile.fileName() );
    qgsFile.close();
  }

  // stop here with an error message
  if ( ! writeOk )
  {
    setError( tr( "Unable to write temporary qgs file" ) );
    return false;
  }

  // save auxiliary storage
  const QFileInfo info( qgsFile );
  const QString asFileName = info.path() + QDir::separator() + info.completeBaseName() + "." + QgsAuxiliaryStorage::extension();

  if ( ! saveAuxiliaryStorage( asFileName ) )
  {
    setError( tr( "Unable to save auxiliary storage" ) );
    return false;
  }

  // create the archive
  archive->addFile( qgsFile.fileName() );
  archive->addFile( asFileName );

  // zip
  if ( !archive->zip( filename ) )
  {
    setError( tr( "Unable to perform zip" ) );
    return false;
  }

  return true;
}

bool QgsProject::isZipped() const
{
  return QgsZipUtils::isZipFile( mFile.fileName() );
}

QList<QgsMapLayer *> QgsProject::addMapLayers(
  const QList<QgsMapLayer *> &layers,
  bool addToLegend,
  bool takeOwnership )
{
  const QList<QgsMapLayer *> myResultList = mLayerStore->addMapLayers( layers, takeOwnership );
  if ( !myResultList.isEmpty() )
  {
    if ( addToLegend )
      emit legendLayersAdded( myResultList );
  }

  if ( mAuxiliaryStorage )
  {
    for ( QgsMapLayer *mlayer : myResultList )
    {
      if ( mlayer->type() != QgsMapLayer::VectorLayer )
        continue;

      QgsVectorLayer *vl = qobject_cast<QgsVectorLayer *>( mlayer );
      if ( vl )
      {
        vl->loadAuxiliaryLayer( *mAuxiliaryStorage );
      }
    }
  }

  return myResultList;
}

QgsMapLayer *
QgsProject::addMapLayer( QgsMapLayer *layer,
                         bool addToLegend,
                         bool takeOwnership )
{
  QList<QgsMapLayer *> addedLayers;
  addedLayers = addMapLayers( QList<QgsMapLayer *>() << layer, addToLegend, takeOwnership );
  return addedLayers.isEmpty() ? nullptr : addedLayers[0];
}

void QgsProject::removeMapLayers( const QStringList &layerIds )
{
  mLayerStore->removeMapLayers( layerIds );
}

void QgsProject::removeMapLayers( const QList<QgsMapLayer *> &layers )
{
  mLayerStore->removeMapLayers( layers );
}

void QgsProject::removeMapLayer( const QString &layerId )
{
  mLayerStore->removeMapLayer( layerId );
}

void QgsProject::removeMapLayer( QgsMapLayer *layer )
{
  mLayerStore->removeMapLayer( layer );
}

QgsMapLayer *QgsProject::takeMapLayer( QgsMapLayer *layer )
{
  return mLayerStore->takeMapLayer( layer );
}

void QgsProject::removeAllMapLayers()
{
  mLayerStore->removeAllMapLayers();
}

void QgsProject::reloadAllLayers()
{
  QMap<QString, QgsMapLayer *> layers = mLayerStore->mapLayers();
  QMap<QString, QgsMapLayer *>::const_iterator it = layers.constBegin();
  for ( ; it != layers.constEnd(); ++it )
  {
    it.value()->reload();
  }
}

QMap<QString, QgsMapLayer *> QgsProject::mapLayers() const
{
  return mLayerStore->mapLayers();
}

QgsTransactionGroup *QgsProject::transactionGroup( const QString &providerKey, const QString &connString )
{
  return mTransactionGroups.value( qMakePair( providerKey, connString ) );
}

QgsCoordinateReferenceSystem QgsProject::defaultCrsForNewLayers() const
{
  QgsSettings settings;
  QgsCoordinateReferenceSystem defaultCrs;
  if ( settings.value( QStringLiteral( "/Projections/defaultBehavior" ), QStringLiteral( "prompt" ) ).toString() == QStringLiteral( "useProject" )
       || settings.value( QStringLiteral( "/Projections/defaultBehavior" ), QStringLiteral( "prompt" ) ).toString() == QStringLiteral( "prompt" ) )
  {
    // for new layers if the new layer crs method is set to either prompt or use project, then we use the project crs
    // (since "prompt" has no meaning here - the prompt will always be shown, it's just deciding on the default choice in the prompt!)
    defaultCrs = crs();
  }
  else
  {
    // global crs
    QString layerDefaultCrs = settings.value( QStringLiteral( "/Projections/layerDefaultCrs" ), GEO_EPSG_CRS_AUTHID ).toString();
    defaultCrs = QgsCoordinateReferenceSystem::fromOgcWmsCrs( layerDefaultCrs );
  }

  return defaultCrs;
}

void QgsProject::setTrustLayerMetadata( bool trust )
{
  mTrustLayerMetadata = trust;

  auto layers = mapLayers();
  for ( auto it = layers.constBegin(); it != layers.constEnd(); ++it )
  {
    QgsVectorLayer *vl = qobject_cast<QgsVectorLayer *>( it.value() );
    if ( vl )
    {
      vl->setReadExtentFromXml( trust );
    }
  }
}

bool QgsProject::saveAuxiliaryStorage( const QString &filename )
{
  const QMap<QString, QgsMapLayer *> layers = mapLayers();
  bool empty = true;
  for ( auto it = layers.constBegin(); it != layers.constEnd(); ++it )
  {
    if ( it.value()->type() != QgsMapLayer::VectorLayer )
      continue;

    QgsVectorLayer *vl = qobject_cast<QgsVectorLayer *>( it.value() );
    if ( vl && vl->auxiliaryLayer() )
    {
      vl->auxiliaryLayer()->save();
      empty &= vl->auxiliaryLayer()->auxiliaryFields().isEmpty();
    }
  }

  if ( !mAuxiliaryStorage->exists( *this ) && filename.isEmpty() && empty )
  {
    return true; // it's not an error
  }
  else if ( !filename.isEmpty() )
  {
    return mAuxiliaryStorage->saveAs( filename );
  }
  else
  {
    return mAuxiliaryStorage->saveAs( *this );
  }
}

const QgsAuxiliaryStorage *QgsProject::auxiliaryStorage() const
{
  return mAuxiliaryStorage.get();
}

QgsAuxiliaryStorage *QgsProject::auxiliaryStorage()
{
  return mAuxiliaryStorage.get();
}

const QgsProjectMetadata &QgsProject::metadata() const
{
  return mMetadata;
}

void QgsProject::setMetadata( const QgsProjectMetadata &metadata )
{
  mMetadata = metadata;
  emit metadataChanged();

  setDirty( true );
}

QSet<QgsMapLayer *> QgsProject::requiredLayers() const
{
  QSet<QgsMapLayer *> layers;
  const QStringList lst = readListEntry( QStringLiteral( "RequiredLayers" ), QStringLiteral( "Layers" ) );
  for ( const QString &layerId : lst )
  {
    if ( QgsMapLayer *layer = mapLayer( layerId ) )
      layers.insert( layer );
  }
  return layers;
}

void QgsProject::setRequiredLayers( const QSet<QgsMapLayer *> &layers )
{
  QStringList layerIds;
  for ( QgsMapLayer *layer : layers )
  {
    layerIds << layer->id();
  }
  writeEntry( QStringLiteral( "RequiredLayers" ), QStringLiteral( "Layers" ), layerIds );
}