qgsrelationeditorwidget.cpp

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/***************************************************************************
    qgsrelationeditor.cpp
     --------------------------------------
    Date                 : 17.5.2013
    Copyright            : (C) 2013 Matthias Kuhn
    Email                : matthias at opengis dot ch
 ***************************************************************************
 *                                                                         *
 *   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 "qgsrelationeditorwidget.h"

#include "qgsapplication.h"
#include "qgsdistancearea.h"
#include "qgsfeatureiterator.h"
#include "qgsvectordataprovider.h"
#include "qgsexpression.h"
#include "qgsfeature.h"
#include "qgsfeatureselectiondlg.h"
#include "qgsgenericfeatureselectionmanager.h"
#include "qgsrelation.h"
#include "qgsvectorlayertools.h"
#include "qgsproject.h"
#include "qgstransactiongroup.h"
#include "qgslogger.h"
#include "qgsvectorlayerutils.h"
#include "qgsmapcanvas.h"

#include <QHBoxLayout>
#include <QLabel>
#include <QMessageBox>

QgsRelationEditorWidget::QgsRelationEditorWidget( QWidget *parent )
  : QgsCollapsibleGroupBox( parent )
{
  QVBoxLayout *topLayout = new QVBoxLayout( this );
  topLayout->setContentsMargins( 0, 9, 0, 0 );
  setLayout( topLayout );

  // buttons
  QHBoxLayout *buttonLayout = new QHBoxLayout();
  buttonLayout->setContentsMargins( 0, 0, 0, 0 );
  // toggle editing
  mToggleEditingButton = new QToolButton( this );
  mToggleEditingButton->setObjectName( QStringLiteral( "mToggleEditingButton" ) );
  mToggleEditingButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionToggleEditing.svg" ) ) );
  mToggleEditingButton->setText( tr( "Toggle editing" ) );
  mToggleEditingButton->setEnabled( false );
  mToggleEditingButton->setCheckable( true );
  mToggleEditingButton->setToolTip( tr( "Toggle editing mode for child layer" ) );
  buttonLayout->addWidget( mToggleEditingButton );
  // save Edits
  mSaveEditsButton = new QToolButton( this );
  mSaveEditsButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionSaveEdits.svg" ) ) );
  mSaveEditsButton->setText( tr( "Save child layer edits" ) );
  mSaveEditsButton->setToolTip( tr( "Save child layer edits" ) );
  mSaveEditsButton->setEnabled( true );
  buttonLayout->addWidget( mSaveEditsButton );
  // add feature
  mAddFeatureButton = new QToolButton( this );
  mAddFeatureButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionNewTableRow.svg" ) ) );
  mAddFeatureButton->setText( tr( "Add child feature" ) );
  mAddFeatureButton->setToolTip( tr( "Add child feature" ) );
  mAddFeatureButton->setObjectName( QStringLiteral( "mAddFeatureButton" ) );
  buttonLayout->addWidget( mAddFeatureButton );
  // duplicate feature
  mDuplicateFeatureButton = new QToolButton( this );
  mDuplicateFeatureButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionDuplicateFeature.svg" ) ) );
  mDuplicateFeatureButton->setText( tr( "Duplicate child feature" ) );
  mDuplicateFeatureButton->setToolTip( tr( "Duplicate child feature" ) );
  mDuplicateFeatureButton->setObjectName( QStringLiteral( "mDuplicateFeatureButton" ) );
  buttonLayout->addWidget( mDuplicateFeatureButton );
  // delete feature
  mDeleteFeatureButton = new QToolButton( this );
  mDeleteFeatureButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionDeleteSelected.svg" ) ) );
  mDeleteFeatureButton->setText( tr( "Delete child feature" ) );
  mDeleteFeatureButton->setToolTip( tr( "Delete child feature" ) );
  mDeleteFeatureButton->setObjectName( QStringLiteral( "mDeleteFeatureButton" ) );
  buttonLayout->addWidget( mDeleteFeatureButton );
  // link feature
  mLinkFeatureButton = new QToolButton( this );
  mLinkFeatureButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionLink.svg" ) ) );
  mLinkFeatureButton->setText( tr( "Link existing features" ) );
  mLinkFeatureButton->setToolTip( tr( "Link existing child features" ) );
  mLinkFeatureButton->setObjectName( QStringLiteral( "mLinkFeatureButton" ) );
  buttonLayout->addWidget( mLinkFeatureButton );
  // unlink feature
  mUnlinkFeatureButton = new QToolButton( this );
  mUnlinkFeatureButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionUnlink.svg" ) ) );
  mUnlinkFeatureButton->setText( tr( "Unlink feature" ) );
  mUnlinkFeatureButton->setToolTip( tr( "Unlink child feature" ) );
  mUnlinkFeatureButton->setObjectName( QStringLiteral( "mUnlinkFeatureButton" ) );
  buttonLayout->addWidget( mUnlinkFeatureButton );
  // zoom to linked feature
  mZoomToFeatureButton = new QToolButton( this );
  mZoomToFeatureButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionZoomToSelected.svg" ) ) );
  mZoomToFeatureButton->setText( tr( "Zoom To Feature" ) );
  mZoomToFeatureButton->setToolTip( tr( "Zoom to child feature" ) );
  mZoomToFeatureButton->setObjectName( QStringLiteral( "mZoomToFeatureButton" ) );
  buttonLayout->addWidget( mZoomToFeatureButton );
  // spacer
  buttonLayout->addItem( new QSpacerItem( 0, 0, QSizePolicy::Expanding ) );
  // form view
  mFormViewButton = new QToolButton( this );
  mFormViewButton->setText( tr( "Form view" ) );
  mFormViewButton->setToolTip( tr( "Switch to form view" ) );
  mFormViewButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionPropertyItem.svg" ) ) );
  mFormViewButton->setCheckable( true );
  mFormViewButton->setChecked( mViewMode == QgsDualView::AttributeEditor );
  buttonLayout->addWidget( mFormViewButton );
  // table view
  mTableViewButton = new QToolButton( this );
  mTableViewButton->setText( tr( "Table view" ) );
  mTableViewButton->setToolTip( tr( "Switch to table view" ) );
  mTableViewButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mActionOpenTable.svg" ) ) );
  mTableViewButton->setCheckable( true );
  mTableViewButton->setChecked( mViewMode == QgsDualView::AttributeTable );
  buttonLayout->addWidget( mTableViewButton );
  // button group
  mViewModeButtonGroup = new QButtonGroup( this );
  mViewModeButtonGroup->addButton( mFormViewButton, QgsDualView::AttributeEditor );
  mViewModeButtonGroup->addButton( mTableViewButton, QgsDualView::AttributeTable );

  // add buttons layout
  topLayout->addLayout( buttonLayout );

  mRelationLayout = new QGridLayout();
  mRelationLayout->setContentsMargins( 0, 0, 0, 0 );
  topLayout->addLayout( mRelationLayout );

  mDualView = new QgsDualView( this );
  mDualView->setView( mViewMode );
  mFeatureSelectionMgr = new QgsGenericFeatureSelectionManager( mDualView );
  mDualView->setFeatureSelectionManager( mFeatureSelectionMgr );

  mRelationLayout->addWidget( mDualView );

  connect( this, &QgsCollapsibleGroupBoxBasic::collapsedStateChanged, this, &QgsRelationEditorWidget::onCollapsedStateChanged );
  connect( mViewModeButtonGroup, static_cast<void ( QButtonGroup::* )( int )>( &QButtonGroup::buttonClicked ),
           this, static_cast<void ( QgsRelationEditorWidget::* )( int )>( &QgsRelationEditorWidget::setViewMode ) );
  connect( mToggleEditingButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::toggleEditing );
  connect( mSaveEditsButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::saveEdits );
  connect( mAddFeatureButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::addFeature );
  connect( mDuplicateFeatureButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::duplicateFeature );
  connect( mDeleteFeatureButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::deleteSelectedFeatures );
  connect( mLinkFeatureButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::linkFeature );
  connect( mUnlinkFeatureButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::unlinkSelectedFeatures );
  connect( mZoomToFeatureButton, &QAbstractButton::clicked, this, &QgsRelationEditorWidget::zoomToSelectedFeatures );
  connect( mFeatureSelectionMgr, &QgsIFeatureSelectionManager::selectionChanged, this, &QgsRelationEditorWidget::updateButtons );

  connect( mDualView, &QgsDualView::showContextMenuExternally, this, &QgsRelationEditorWidget::showContextMenu );

  // Set initial state for add/remove etc. buttons
  updateButtons();
}

void QgsRelationEditorWidget::setRelationFeature( const QgsRelation &relation, const QgsFeature &feature )
{
  if ( mRelation.isValid() )
  {
    disconnect( mRelation.referencingLayer(), &QgsVectorLayer::editingStarted, this, &QgsRelationEditorWidget::updateButtons );
    disconnect( mRelation.referencingLayer(), &QgsVectorLayer::editingStopped, this, &QgsRelationEditorWidget::updateButtons );
  }

  mRelation = relation;
  mFeature = feature;

  connect( mRelation.referencingLayer(), &QgsVectorLayer::editingStarted, this, &QgsRelationEditorWidget::updateButtons );
  connect( mRelation.referencingLayer(), &QgsVectorLayer::editingStopped, this, &QgsRelationEditorWidget::updateButtons );

  if ( mShowLabel )
    setTitle( relation.name() );

  QgsVectorLayer *lyr = relation.referencingLayer();

  bool canChangeAttributes = lyr->dataProvider()->capabilities() & QgsVectorDataProvider::ChangeAttributeValues;
  if ( canChangeAttributes && !lyr->readOnly() )
  {
    mToggleEditingButton->setEnabled( true );
    updateButtons();
  }
  else
  {
    mToggleEditingButton->setEnabled( false );
  }

  setObjectName( QStringLiteral( "referenced/" ) + mRelation.name() );

  // If not yet initialized, it is not (yet) visible, so we don't load it to be faster (lazy loading)
  // If it is already initialized, it has been set visible before and the currently shown feature is changing
  // and the widget needs updating

  if ( mVisible )
  {
    QgsFeatureRequest myRequest = mRelation.getRelatedFeaturesRequest( mFeature );
    mDualView->init( mRelation.referencingLayer(), nullptr, myRequest, mEditorContext );
  }
}

void QgsRelationEditorWidget::setRelations( const QgsRelation &relation, const QgsRelation &nmrelation )
{
  if ( mRelation.isValid() )
  {
    disconnect( mRelation.referencingLayer(), &QgsVectorLayer::editingStarted, this, &QgsRelationEditorWidget::updateButtons );
    disconnect( mRelation.referencingLayer(), &QgsVectorLayer::editingStopped, this, &QgsRelationEditorWidget::updateButtons );
  }

  if ( mNmRelation.isValid() )
  {
    disconnect( mNmRelation.referencedLayer(), &QgsVectorLayer::editingStarted, this, &QgsRelationEditorWidget::updateButtons );
    disconnect( mNmRelation.referencedLayer(), &QgsVectorLayer::editingStopped, this, &QgsRelationEditorWidget::updateButtons );
  }

  mRelation = relation;
  mNmRelation = nmrelation;

  if ( !mRelation.isValid() )
    return;

  mToggleEditingButton->setVisible( true );

  const auto transactionGroups = QgsProject::instance()->transactionGroups();
  for ( auto it = transactionGroups.constBegin(); it != transactionGroups.constEnd(); ++it )
  {
    if ( it.value()->layers().contains( mRelation.referencingLayer() ) )
    {
      mToggleEditingButton->setVisible( false );
      mSaveEditsButton->setVisible( false );
    }
  }

  connect( mRelation.referencingLayer(), &QgsVectorLayer::editingStarted, this, &QgsRelationEditorWidget::updateButtons );
  connect( mRelation.referencingLayer(), &QgsVectorLayer::editingStopped, this, &QgsRelationEditorWidget::updateButtons );

  if ( mNmRelation.isValid() )
  {
    connect( mNmRelation.referencedLayer(), &QgsVectorLayer::editingStarted, this, &QgsRelationEditorWidget::updateButtons );
    connect( mNmRelation.referencedLayer(), &QgsVectorLayer::editingStopped, this, &QgsRelationEditorWidget::updateButtons );
  }

  setTitle( relation.name() );

  QgsVectorLayer *lyr = relation.referencingLayer();

  bool canChangeAttributes = lyr->dataProvider()->capabilities() & QgsVectorDataProvider::ChangeAttributeValues;
  if ( canChangeAttributes && !lyr->readOnly() )
  {
    mToggleEditingButton->setEnabled( true );
    updateButtons();
  }
  else
  {
    mToggleEditingButton->setEnabled( false );
  }

  if ( mNmRelation.isValid() )
    mZoomToFeatureButton->setVisible( mNmRelation.referencedLayer()->isSpatial() );
  else
    mZoomToFeatureButton->setVisible( mRelation.referencingLayer()->isSpatial() );

  setObjectName( QStringLiteral( "referenced/" ) + mRelation.name() );

  updateUi();
}

void QgsRelationEditorWidget::setEditorContext( const QgsAttributeEditorContext &context )
{
  mEditorContext = context;
}

QgsIFeatureSelectionManager *QgsRelationEditorWidget::featureSelectionManager()
{
  return mFeatureSelectionMgr;
}

void QgsRelationEditorWidget::setViewMode( QgsDualView::ViewMode mode )
{
  mDualView->setView( mode );
  mViewMode = mode;
}

void QgsRelationEditorWidget::setFeature( const QgsFeature &feature )
{
  mFeature = feature;

  updateUi();
}

void QgsRelationEditorWidget::updateButtons()
{
  bool editable = false;
  bool linkable = false;
  bool selectionNotEmpty = mFeatureSelectionMgr->selectedFeatureCount();

  if ( mRelation.isValid() )
  {
    editable = mRelation.referencingLayer()->isEditable();
    linkable = mRelation.referencingLayer()->isEditable();
  }

  if ( mNmRelation.isValid() )
  {
    editable = mNmRelation.referencedLayer()->isEditable();
  }

  mAddFeatureButton->setEnabled( editable );
  mDuplicateFeatureButton->setEnabled( editable && selectionNotEmpty );
  mLinkFeatureButton->setEnabled( linkable );
  mDeleteFeatureButton->setEnabled( editable && selectionNotEmpty );
  mUnlinkFeatureButton->setEnabled( linkable && selectionNotEmpty );

  mZoomToFeatureButton->setVisible(
    mEditorContext.mapCanvas() && (
      (
        mNmRelation.isValid() &&
        mNmRelation.referencedLayer()->geometryType() != QgsWkbTypes::NullGeometry &&
        mNmRelation.referencedLayer()->geometryType() != QgsWkbTypes::UnknownGeometry
      )
      ||
      (
        mRelation.isValid() &&
        mRelation.referencedLayer()->geometryType() != QgsWkbTypes::NullGeometry &&
        mRelation.referencedLayer()->geometryType() != QgsWkbTypes::UnknownGeometry
      )
    )
  );

  mZoomToFeatureButton->setEnabled( selectionNotEmpty );

  mToggleEditingButton->setChecked( editable );
  mSaveEditsButton->setEnabled( editable );
}

void QgsRelationEditorWidget::addFeature()
{
  QgsAttributeMap keyAttrs;

  const QgsVectorLayerTools *vlTools = mEditorContext.vectorLayerTools();

  if ( mNmRelation.isValid() )
  {
    // n:m Relation: first let the user create a new feature on the other table
    // and autocreate a new linking feature.
    QgsFeature f;
    if ( vlTools->addFeature( mNmRelation.referencedLayer(), QgsAttributeMap(), QgsGeometry(), &f ) )
    {
      // Fields of the linking table
      const QgsFields fields = mRelation.referencingLayer()->fields();

      // Expression context for the linking table
      QgsExpressionContext context = mRelation.referencingLayer()->createExpressionContext();

      QgsAttributeMap linkAttributes;
      Q_FOREACH ( const QgsRelation::FieldPair &fieldPair, mRelation.fieldPairs() )
      {
        int index = fields.indexOf( fieldPair.first );
        linkAttributes.insert( index,  mFeature.attribute( fieldPair.second ) );
      }

      Q_FOREACH ( const QgsRelation::FieldPair &fieldPair, mNmRelation.fieldPairs() )
      {
        int index = fields.indexOf( fieldPair.first );
        linkAttributes.insert( index, f.attribute( fieldPair.second ) );
      }
      QgsFeature linkFeature = QgsVectorLayerUtils::createFeature( mRelation.referencingLayer(), QgsGeometry(), linkAttributes, &context );

      mRelation.referencingLayer()->addFeature( linkFeature );

      updateUi();
    }
  }
  else
  {
    QgsFields fields = mRelation.referencingLayer()->fields();

    Q_FOREACH ( const QgsRelation::FieldPair &fieldPair, mRelation.fieldPairs() )
    {
      keyAttrs.insert( fields.indexFromName( fieldPair.referencingField() ), mFeature.attribute( fieldPair.referencedField() ) );
    }

    vlTools->addFeature( mDualView->masterModel()->layer(), keyAttrs );
  }
}

void QgsRelationEditorWidget::linkFeature()
{
  QgsVectorLayer *layer = nullptr;

  if ( mNmRelation.isValid() )
    layer = mNmRelation.referencedLayer();
  else
    layer = mRelation.referencingLayer();

  QgsFeatureSelectionDlg selectionDlg( layer, mEditorContext, this );

  if ( selectionDlg.exec() )
  {
    if ( mNmRelation.isValid() )
    {
      QgsFeatureIterator it = mNmRelation.referencedLayer()->getFeatures(
                                QgsFeatureRequest()
                                .setFilterFids( selectionDlg.selectedFeatures() )
                                .setSubsetOfAttributes( mNmRelation.referencedFields() ) );

      QgsFeature relatedFeature;

      QgsFeatureList newFeatures;

      // Fields of the linking table
      const QgsFields fields = mRelation.referencingLayer()->fields();

      // Expression context for the linking table
      QgsExpressionContext context = mRelation.referencingLayer()->createExpressionContext();

      QgsAttributeMap linkAttributes;
      Q_FOREACH ( const QgsRelation::FieldPair &fieldPair, mRelation.fieldPairs() )
      {
        int index = fields.indexOf( fieldPair.first );
        linkAttributes.insert( index,  mFeature.attribute( fieldPair.second ) );
      }

      while ( it.nextFeature( relatedFeature ) )
      {
        Q_FOREACH ( const QgsRelation::FieldPair &fieldPair, mNmRelation.fieldPairs() )
        {
          int index = fields.indexOf( fieldPair.first );
          linkAttributes.insert( index, relatedFeature.attribute( fieldPair.second ) );
        }
        const QgsFeature linkFeature = QgsVectorLayerUtils::createFeature( mRelation.referencingLayer(), QgsGeometry(), linkAttributes, &context );

        newFeatures << linkFeature;
      }

      mRelation.referencingLayer()->addFeatures( newFeatures );
      QgsFeatureIds ids;
      Q_FOREACH ( const QgsFeature &f, newFeatures )
        ids << f.id();
      mRelation.referencingLayer()->selectByIds( ids );


      updateUi();
    }
    else
    {
      QMap<int, QVariant> keys;
      Q_FOREACH ( const QgsRelation::FieldPair &fieldPair, mRelation.fieldPairs() )
      {
        int idx = mRelation.referencingLayer()->fields().lookupField( fieldPair.referencingField() );
        QVariant val = mFeature.attribute( fieldPair.referencedField() );
        keys.insert( idx, val );
      }

      Q_FOREACH ( QgsFeatureId fid, selectionDlg.selectedFeatures() )
      {
        QMapIterator<int, QVariant> it( keys );
        while ( it.hasNext() )
        {
          it.next();
          mRelation.referencingLayer()->changeAttributeValue( fid, it.key(), it.value() );
        }
      }
    }
  }
}

void QgsRelationEditorWidget::duplicateFeature()
{
  QgsVectorLayer *layer = mRelation.referencingLayer();

  QgsFeatureIterator fit = layer->getFeatures( QgsFeatureRequest().setFilterFids( mFeatureSelectionMgr->selectedFeatureIds() ) );
  QgsFeature f;
  while ( fit.nextFeature( f ) )
  {
    QgsVectorLayerUtils::QgsDuplicateFeatureContext duplicatedFeatureContext;
    QgsVectorLayerUtils::duplicateFeature( layer, f, QgsProject::instance(), 0, duplicatedFeatureContext );
  }
}

void QgsRelationEditorWidget::deleteFeature( const QgsFeatureId featureid )
{
  deleteFeatures( QgsFeatureIds() << featureid );
}

void QgsRelationEditorWidget::deleteSelectedFeatures()
{
  deleteFeatures( mFeatureSelectionMgr->selectedFeatureIds() );
}

void QgsRelationEditorWidget::deleteFeatures( const QgsFeatureIds &featureids )
{
  bool deleteFeatures = true;

  QgsVectorLayer *layer;
  if ( mNmRelation.isValid() )
  {
    layer = mNmRelation.referencedLayer();

    // When deleting a linked feature within an N:M relation,
    // check if the feature is linked to more than just one feature.
    // In case it is linked more than just once, ask the user for confirmation
    // as it is likely he was not aware of the implications and might either
    // leave the dataset in a corrupted state (referential integrity) or if
    // the fk constraint is ON CASCADE DELETE, there may be several linking
    // entries deleted along.

    QgsFeatureRequest deletedFeaturesRequest;
    deletedFeaturesRequest.setFilterFids( featureids );
    deletedFeaturesRequest.setFlags( QgsFeatureRequest::NoGeometry );
    deletedFeaturesRequest.setSubsetOfAttributes( QgsAttributeList() << mNmRelation.referencedFields().first() );

    QgsFeatureIterator deletedFeatures = layer->getFeatures( deletedFeaturesRequest );
    QStringList deletedFeaturesPks;
    QgsFeature feature;
    while ( deletedFeatures.nextFeature( feature ) )
    {
      deletedFeaturesPks.append( QgsExpression::quotedValue( feature.attribute( mNmRelation.referencedFields().first() ) ) );
    }

    QgsFeatureRequest linkingFeaturesRequest;
    linkingFeaturesRequest.setFlags( QgsFeatureRequest::NoGeometry );
    linkingFeaturesRequest.setNoAttributes();

    QString linkingFeaturesRequestExpression;
    if ( !deletedFeaturesPks.empty() )
    {
      linkingFeaturesRequestExpression = QStringLiteral( "%1 IN (%2)" ).arg( QgsExpression::quotedColumnRef( mNmRelation.fieldPairs().first().first ), deletedFeaturesPks.join( ',' ) );
      linkingFeaturesRequest.setFilterExpression( linkingFeaturesRequestExpression );

      QgsFeatureIterator relatedLinkingFeatures = mNmRelation.referencingLayer()->getFeatures( linkingFeaturesRequest );

      int relatedLinkingFeaturesCount = 0;
      while ( relatedLinkingFeatures.nextFeature( feature ) )
      {
        relatedLinkingFeaturesCount++;
      }

      if ( deletedFeaturesPks.size() == 1 && relatedLinkingFeaturesCount > 1 )
      {
        QMessageBox messageBox( QMessageBox::Question, tr( "Really delete entry?" ), tr( "The entry on %1 is still linked to %2 features on %3. Do you want to delete it?" ).arg( mNmRelation.referencedLayer()->name(), QString::number( relatedLinkingFeaturesCount ), mRelation.referencedLayer()->name() ), QMessageBox::NoButton, this );
        messageBox.addButton( QMessageBox::Cancel );
        QAbstractButton *deleteButton = messageBox.addButton( tr( "Delete" ),  QMessageBox::AcceptRole );

        messageBox.exec();
        if ( messageBox.clickedButton() != deleteButton )
          deleteFeatures = false;
      }
      else if ( deletedFeaturesPks.size() > 1 && relatedLinkingFeaturesCount > deletedFeaturesPks.size() )
      {
        QMessageBox messageBox( QMessageBox::Question, tr( "Really delete entries?" ), tr( "The %1 entries on %2 are still linked to %3 features on %4. Do you want to delete them?" ).arg( QString::number( deletedFeaturesPks.size() ), mNmRelation.referencedLayer()->name(), QString::number( relatedLinkingFeaturesCount ), mRelation.referencedLayer()->name() ), QMessageBox::NoButton, this );
        messageBox.addButton( QMessageBox::Cancel );
        QAbstractButton *deleteButton = messageBox.addButton( tr( "Delete" ), QMessageBox::AcceptRole );

        messageBox.exec();
        if ( messageBox.clickedButton() != deleteButton )
          deleteFeatures = false;
      }
    }
  }
  else
  {
    layer = mRelation.referencingLayer();
  }

  if ( deleteFeatures )
  {
    layer->deleteFeatures( featureids );
    updateUi();
  }
}

void QgsRelationEditorWidget::unlinkFeature( const QgsFeatureId featureid )
{
  unlinkFeatures( QgsFeatureIds() << featureid );
}

void QgsRelationEditorWidget::unlinkSelectedFeatures()
{
  unlinkFeatures( mFeatureSelectionMgr->selectedFeatureIds() );
}

void QgsRelationEditorWidget::zoomToSelectedFeatures()
{
  QgsMapCanvas *c = mEditorContext.mapCanvas();
  if ( !c )
    return;

  c->zoomToFeatureIds(
    mNmRelation.isValid() ? mNmRelation.referencedLayer() : mRelation.referencingLayer(),
    mFeatureSelectionMgr->selectedFeatureIds()
  );
}

void QgsRelationEditorWidget::unlinkFeatures( const QgsFeatureIds &featureids )
{
  if ( mNmRelation.isValid() )
  {
    QgsFeatureIterator selectedIterator = mNmRelation.referencedLayer()->getFeatures(
                                            QgsFeatureRequest()
                                            .setFilterFids( featureids )
                                            .setSubsetOfAttributes( mNmRelation.referencedFields() ) );

    QgsFeature f;

    QStringList filters;

    while ( selectedIterator.nextFeature( f ) )
    {
      filters << '(' + mNmRelation.getRelatedFeaturesRequest( f ).filterExpression()->expression() + ')';
    }

    QString filter = QStringLiteral( "(%1) AND (%2)" ).arg(
                       mRelation.getRelatedFeaturesRequest( mFeature ).filterExpression()->expression(),
                       filters.join( QStringLiteral( " OR " ) ) );

    QgsFeatureIterator linkedIterator = mRelation.referencingLayer()->getFeatures( QgsFeatureRequest()
                                        .setNoAttributes()
                                        .setFilterExpression( filter ) );

    QgsFeatureIds fids;

    while ( linkedIterator.nextFeature( f ) )
    {
      fids << f.id();
      QgsDebugMsgLevel( FID_TO_STRING( f.id() ), 4 );
    }

    mRelation.referencingLayer()->deleteFeatures( fids );

    updateUi();
  }
  else
  {
    QMap<int, QgsField> keyFields;
    Q_FOREACH ( const QgsRelation::FieldPair &fieldPair, mRelation.fieldPairs() )
    {
      int idx = mRelation.referencingLayer()->fields().lookupField( fieldPair.referencingField() );
      if ( idx < 0 )
      {
        QgsDebugMsg( QStringLiteral( "referencing field %1 not found" ).arg( fieldPair.referencingField() ) );
        return;
      }
      QgsField fld = mRelation.referencingLayer()->fields().at( idx );
      keyFields.insert( idx, fld );
    }

    Q_FOREACH ( QgsFeatureId fid, featureids )
    {
      QMapIterator<int, QgsField> it( keyFields );
      while ( it.hasNext() )
      {
        it.next();
        mRelation.referencingLayer()->changeAttributeValue( fid, it.key(), QVariant( it.value().type() ) );
      }
    }
  }
}

void QgsRelationEditorWidget::toggleEditing( bool state )
{
  if ( state )
  {
    mEditorContext.vectorLayerTools()->startEditing( mRelation.referencingLayer() );
    if ( mNmRelation.isValid() )
      mEditorContext.vectorLayerTools()->startEditing( mNmRelation.referencedLayer() );
  }
  else
  {
    mEditorContext.vectorLayerTools()->stopEditing( mRelation.referencingLayer() );
    if ( mNmRelation.isValid() )
      mEditorContext.vectorLayerTools()->stopEditing( mNmRelation.referencedLayer() );
  }
}

void QgsRelationEditorWidget::saveEdits()
{
  mEditorContext.vectorLayerTools()->saveEdits( mRelation.referencingLayer() );
  if ( mNmRelation.isValid() )
    mEditorContext.vectorLayerTools()->saveEdits( mNmRelation.referencedLayer() );
}

void QgsRelationEditorWidget::onCollapsedStateChanged( bool collapsed )
{
  if ( !collapsed )
  {
    mVisible = true;
    updateUi();
  }
}

void QgsRelationEditorWidget::updateUi()
{
  // If not yet initialized, it is not (yet) visible, so we don't load it to be faster (lazy loading)
  // If it is already initialized, it has been set visible before and the currently shown feature is changing
  // and the widget needs updating

  if ( mVisible )
  {
    QgsFeatureRequest myRequest = mRelation.getRelatedFeaturesRequest( mFeature );

    if ( mNmRelation.isValid() )
    {
      QgsFeatureIterator it = mRelation.referencingLayer()->getFeatures( myRequest );

      QgsFeature fet;

      QStringList filters;

      while ( it.nextFeature( fet ) )
      {
        QString filter = mNmRelation.getReferencedFeatureRequest( fet ).filterExpression()->expression();
        filters << filter.prepend( '(' ).append( ')' );
      }

      QgsFeatureRequest nmRequest;

      nmRequest.setFilterExpression( filters.join( QStringLiteral( " OR " ) ) );

      mDualView->init( mNmRelation.referencedLayer(), nullptr, nmRequest, mEditorContext );
    }
    else
    {
      mDualView->init( mRelation.referencingLayer(), nullptr, myRequest, mEditorContext );
    }
  }
}

bool QgsRelationEditorWidget::showLinkButton() const
{
  return mLinkFeatureButton->isVisible();
}

void QgsRelationEditorWidget::setShowLinkButton( bool showLinkButton )
{
  mLinkFeatureButton->setVisible( showLinkButton );
}

bool QgsRelationEditorWidget::showUnlinkButton() const
{
  return mUnlinkFeatureButton->isVisible();
}

void QgsRelationEditorWidget::setShowUnlinkButton( bool showUnlinkButton )
{
  mUnlinkFeatureButton->setVisible( showUnlinkButton );
}

bool QgsRelationEditorWidget::showLabel() const
{
  return mShowLabel;
}

void QgsRelationEditorWidget::setShowLabel( bool showLabel )
{
  mShowLabel = showLabel;

  if ( mShowLabel && mRelation.isValid() )
    setTitle( mRelation.name() );
  else
    setTitle( QString() );
}

void QgsRelationEditorWidget::showContextMenu( QgsActionMenu *menu, const QgsFeatureId fid )
{
  if ( mRelation.referencingLayer()->isEditable() )
  {
    QAction *qAction = nullptr;

    qAction = menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionDeleteSelected.svg" ) ),  tr( "Delete Feature" ) );
    connect( qAction, &QAction::triggered, this, [this, fid]() { deleteFeature( fid ); } );

    qAction = menu->addAction( QgsApplication::getThemeIcon( QStringLiteral( "/mActionUnlink.svg" ) ),  tr( "Unlink Feature" ) );
    connect( qAction, &QAction::triggered, this, [this, fid]() { unlinkFeature( fid ); } );
  }
}