qgsfieldcalculator.cpp

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/***************************************************************************
    qgsfieldcalculator.cpp
    ---------------------
    begin                : September 2009
    copyright            : (C) 2009 by Marco Hugentobler
    email                : marco at hugis dot net
 ***************************************************************************
 *                                                                         *
 *   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 <QMessageBox>
 
 
#include "qgsfieldcalculator.h"
#include "qgsdistancearea.h"
#include "qgsexpression.h"
#include "qgsfeatureiterator.h"
#include "qgsmapcanvas.h"
#include "qgsproject.h"
#include "qgsvectordataprovider.h"
#include "qgsvectorlayer.h"
#include "qgsexpressioncontext.h"
#include "qgsgeometry.h"
#include "qgssettings.h"
#include "qgsgui.h"
#include "qgsguiutils.h"
#include "qgsproxyprogresstask.h"
#include "qgsexpressioncontextutils.h"
#include "qgsvectorlayerjoinbuffer.h"
 
 
// FTC = FieldTypeCombo
constexpr int FTC_TYPE_ROLE_IDX = 0;
constexpr int FTC_TYPE_NAME_IDX = 1;
constexpr int FTC_MINLEN_IDX = 2;
constexpr int FTC_MAXLEN_IDX = 3;
constexpr int FTC_MINPREC_IDX = 4;
constexpr int FTC_MAXPREC_IDX = 5;
constexpr int FTC_SUBTYPE_IDX = 6;
 
QgsFieldCalculator::QgsFieldCalculator( QgsVectorLayer *vl, QWidget *parent )
  : QDialog( parent )
  , mVectorLayer( vl )
  , mAttributeId( -1 )
{
  setupUi( this );
  connect( mNewFieldGroupBox, &QGroupBox::toggled, this, &QgsFieldCalculator::mNewFieldGroupBox_toggled );
  connect( mUpdateExistingGroupBox, &QGroupBox::toggled, this, &QgsFieldCalculator::mUpdateExistingGroupBox_toggled );
  connect( mCreateVirtualFieldCheckbox, &QCheckBox::stateChanged, this, &QgsFieldCalculator::mCreateVirtualFieldCheckbox_stateChanged );
  connect( mOutputFieldNameLineEdit, &QLineEdit::textChanged, this, &QgsFieldCalculator::mOutputFieldNameLineEdit_textChanged );
  connect( mOutputFieldTypeComboBox, static_cast<void ( QComboBox::* )( int )>( &QComboBox::activated ), this, &QgsFieldCalculator::mOutputFieldTypeComboBox_activated );
 
  QgsGui::enableAutoGeometryRestore( this );
 
  if ( !vl )
    return;
  QgsVectorDataProvider *dataProvider = vl->dataProvider();
  if ( !dataProvider )
    return;
 
  const QgsVectorDataProvider::Capabilities caps = dataProvider->capabilities();
  mCanAddAttribute = caps & QgsVectorDataProvider::AddAttributes;
  mCanChangeAttributeValue = caps & QgsVectorDataProvider::ChangeAttributeValues;
 
  QgsExpressionContext expContext( QgsExpressionContextUtils::globalProjectLayerScopes( mVectorLayer ) );
 
  expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "row_number" ), 1, true ) );
  expContext.setHighlightedVariables( QStringList() << QStringLiteral( "row_number" ) );
 
  populateFields();
  populateOutputFieldTypes();
 
  connect( builder, &QgsExpressionBuilderWidget::expressionParsed, this, &QgsFieldCalculator::setOkButtonState );
  connect( mOutputFieldWidthSpinBox, &QAbstractSpinBox::editingFinished, this, &QgsFieldCalculator::setPrecisionMinMax );
  connect( mButtonBox, &QDialogButtonBox::helpRequested, this, &QgsFieldCalculator::showHelp );
 
  QgsDistanceArea myDa;
  myDa.setSourceCrs( vl->crs(), QgsProject::instance()->transformContext() );
  myDa.setEllipsoid( QgsProject::instance()->ellipsoid() );
  builder->setGeomCalculator( myDa );
 
  //default values for field width and precision
  mOutputFieldWidthSpinBox->setValue( 10 );
  mOutputFieldWidthSpinBox->setClearValue( 10 );
  mOutputFieldPrecisionSpinBox->setValue( 3 );
  mOutputFieldPrecisionSpinBox->setClearValue( 3 );
  setPrecisionMinMax();
 
  if ( vl->providerType() == QLatin1String( "ogr" ) && vl->storageType() == QLatin1String( "ESRI Shapefile" ) )
  {
    mOutputFieldNameLineEdit->setMaxLength( 10 );
  }
 
  if ( !mCanAddAttribute )
  {
    mCreateVirtualFieldCheckbox->setChecked( true );
    mCreateVirtualFieldCheckbox->setEnabled( false );
    mOnlyVirtualFieldsInfoLabel->setVisible( true );
    mInfoIcon->setVisible( true );
  }
  else
  {
    mOnlyVirtualFieldsInfoLabel->setVisible( false );
    mInfoIcon->setVisible( false );
  }
 
  if ( !mCanChangeAttributeValue )
  {
    mUpdateExistingGroupBox->setEnabled( false );
    mCreateVirtualFieldCheckbox->setChecked( true );
    mCreateVirtualFieldCheckbox->setEnabled( false );
  }
 
  Q_ASSERT( mNewFieldGroupBox->isEnabled() || mUpdateExistingGroupBox->isEnabled() );
 
  if ( mNewFieldGroupBox->isEnabled() )
  {
    mNewFieldGroupBox->setChecked( true );
  }
  else
  {
    mNewFieldGroupBox->setToolTip( tr( "Not available for layer" ) );
    mUpdateExistingGroupBox->setChecked( true );
    mUpdateExistingGroupBox->setCheckable( false );
  }
 
  if ( mUpdateExistingGroupBox->isEnabled() )
  {
    mUpdateExistingGroupBox->setChecked( !mNewFieldGroupBox->isEnabled() );
  }
  else
  {
    mUpdateExistingGroupBox->setToolTip( tr( "Not available for layer" ) );
    mNewFieldGroupBox->setChecked( true );
    mNewFieldGroupBox->setCheckable( false );
  }
 
  if ( ( mNewFieldGroupBox->isChecked() && mCreateVirtualFieldCheckbox->isChecked() ) || mVectorLayer->isEditable() )
  {
    mEditModeAutoTurnOnLabel->setVisible( false );
    mInfoIcon->setVisible( false );
  }
  else
  {
    mInfoIcon->setVisible( true );
  }
 
  const bool hasselection = vl->selectedFeatureCount() > 0;
  mOnlyUpdateSelectedCheckBox->setChecked( mCanChangeAttributeValue && hasselection );
  mOnlyUpdateSelectedCheckBox->setEnabled( mCanChangeAttributeValue && hasselection );
  mOnlyUpdateSelectedCheckBox->setText( tr( "Only update %1 selected features" ).arg( vl->selectedFeatureCount() ) );
 
  builder->initWithLayer( vl, expContext, QStringLiteral( "fieldcalc" ) );
 
  mInfoIcon->setPixmap( style()->standardPixmap( QStyle::SP_MessageBoxInformation ) );
 
  setWindowTitle( tr( "%1 — Field Calculator" ).arg( mVectorLayer->name() ) );
 
  setOkButtonState();
}
 
void QgsFieldCalculator::accept()
{
  builder->expressionTree()->saveToRecent( builder->expressionText(), QStringLiteral( "fieldcalc" ) );
 
  if ( !mVectorLayer )
    return;
 
  // Set up QgsDistanceArea each time we (re-)calculate
  QgsDistanceArea myDa;
 
  myDa.setSourceCrs( mVectorLayer->crs(), QgsProject::instance()->transformContext() );
  myDa.setEllipsoid( QgsProject::instance()->ellipsoid() );
 
  const QString calcString = builder->expressionText();
  QgsExpression exp( calcString );
  exp.setGeomCalculator( &myDa );
  exp.setDistanceUnits( QgsProject::instance()->distanceUnits() );
  exp.setAreaUnits( QgsProject::instance()->areaUnits() );
 
  QgsExpressionContext expContext( QgsExpressionContextUtils::globalProjectLayerScopes( mVectorLayer ) );
 
  if ( !exp.prepare( &expContext ) )
  {
    QMessageBox::critical( nullptr, tr( "Evaluation Error" ), exp.evalErrorString() );
    return;
  }
 
  bool updatingGeom = false;
 
  // Test for creating expression field based on ! mUpdateExistingGroupBox checked rather
  // than on mNewFieldGroupBox checked, as if the provider does not support adding attributes
  // then mUpdateExistingGroupBox is set to not checkable, and hence is not checked.  This
  // is a minimum fix to resolve this - better would be some GUI redesign...
  if ( ! mUpdateExistingGroupBox->isChecked() && mCreateVirtualFieldCheckbox->isChecked() )
  {
    mVectorLayer->addExpressionField( calcString, fieldDefinition() );
  }
  else
  {
    if ( !mVectorLayer->isEditable() )
      mVectorLayer->startEditing();
 
    QgsTemporaryCursorOverride cursorOverride( Qt::WaitCursor );
 
    mVectorLayer->beginEditCommand( QStringLiteral( "Field calculator" ) );
 
    //update existing field
    if ( mUpdateExistingGroupBox->isChecked() || !mNewFieldGroupBox->isEnabled() )
    {
      if ( mExistingFieldComboBox->currentData().toString() == QLatin1String( "geom" ) )
      {
        //update geometry
        mAttributeId = -1;
        updatingGeom = true;
      }
      else
      {
        bool ok = false;
        const int id = mExistingFieldComboBox->currentData().toInt( &ok );
        if ( ok )
          mAttributeId = id;
      }
    }
    else
    {
      //create new field
      const QgsField newField = fieldDefinition();
 
      if ( !mVectorLayer->addAttribute( newField ) )
      {
        cursorOverride.release();
        QMessageBox::critical( nullptr, tr( "Create New Field" ), tr( "Could not add the new field to the provider." ) );
        mVectorLayer->destroyEditCommand();
        return;
      }
 
      //get index of the new field
      const QgsFields &fields = mVectorLayer->fields();
 
      for ( int idx = 0; idx < fields.count(); ++idx )
      {
        if ( fields.at( idx ).name() == mOutputFieldNameLineEdit->text() )
        {
          mAttributeId = idx;
          break;
        }
      }
 
      //update expression context with new fields
      expContext.setFields( mVectorLayer->fields() );
      if ( ! exp.prepare( &expContext ) )
      {
        cursorOverride.release();
        QMessageBox::critical( nullptr, tr( "Evaluation Error" ), exp.evalErrorString() );
        return;
      }
    }
 
    if ( mAttributeId == -1 && !updatingGeom )
    {
      mVectorLayer->destroyEditCommand();
      return;
    }
 
    //go through all the features and change the new attribute
    QgsFeature feature;
    bool calculationSuccess = true;
    QString error;
 
    const bool useGeometry = exp.needsGeometry();
    int rownum = 1;
 
    const QgsField field = !updatingGeom ? mVectorLayer->fields().at( mAttributeId ) : QgsField();
 
    const bool newField = !mUpdateExistingGroupBox->isChecked();
    QVariant emptyAttribute;
    if ( newField )
      emptyAttribute = QVariant( field.type() );
 
    QgsFeatureRequest req = QgsFeatureRequest().setFlags( useGeometry ? QgsFeatureRequest::NoFlags : QgsFeatureRequest::NoGeometry );
    QSet< QString > referencedColumns = exp.referencedColumns();
    referencedColumns.insert( field.name() ); // need existing column value to store old attribute when changing field values
    req.setSubsetOfAttributes( referencedColumns, mVectorLayer->fields() );
    if ( mOnlyUpdateSelectedCheckBox->isChecked() )
    {
      req.setFilterFids( mVectorLayer->selectedFeatureIds() );
    }
    QgsFeatureIterator fit = mVectorLayer->getFeatures( req );
 
    std::unique_ptr< QgsScopedProxyProgressTask > task = std::make_unique< QgsScopedProxyProgressTask >( tr( "Calculating field" ) );
    const long long count = mOnlyUpdateSelectedCheckBox->isChecked() ? mVectorLayer->selectedFeatureCount() : mVectorLayer->featureCount();
    long long i = 0;
    while ( fit.nextFeature( feature ) )
    {
      i++;
      task->setProgress( i / static_cast< double >( count ) * 100 );
 
      expContext.setFeature( feature );
      expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "row_number" ), rownum, true ) );
 
      QVariant value = exp.evaluate( &expContext );
      if ( exp.hasEvalError() )
      {
        calculationSuccess = false;
        error = exp.evalErrorString();
        break;
      }
      else if ( updatingGeom )
      {
        if ( value.canConvert< QgsGeometry >() )
        {
          QgsGeometry geom = value.value< QgsGeometry >();
          mVectorLayer->changeGeometry( feature.id(), geom );
        }
      }
      else
      {
        ( void )field.convertCompatible( value );
        mVectorLayer->changeAttributeValue( feature.id(), mAttributeId, value, newField ? emptyAttribute : feature.attributes().value( mAttributeId ) );
      }
 
      rownum++;
    }
 
    if ( !calculationSuccess )
    {
      cursorOverride.release();
      task.reset();
      QMessageBox::critical( nullptr, tr( "Evaluation Error" ), tr( "An error occurred while evaluating the calculation string:\n%1" ).arg( error ) );
      mVectorLayer->destroyEditCommand();
      return;
    }
 
    mVectorLayer->endEditCommand();
  }
  QDialog::accept();
}
 
void QgsFieldCalculator::populateOutputFieldTypes()
{
  if ( !mVectorLayer )
  {
    return;
  }
 
  QgsVectorDataProvider *provider = mVectorLayer->dataProvider();
  if ( !provider )
  {
    return;
  }
 
  const int oldDataType = mOutputFieldTypeComboBox->currentData( Qt::UserRole + FTC_TYPE_ROLE_IDX ).toInt();
 
  mOutputFieldTypeComboBox->blockSignals( true );
 
  // Standard subset of fields in case of virtual
  const QList< QgsVectorDataProvider::NativeType > &typelist = mCreateVirtualFieldCheckbox->isChecked() ?
      ( QList< QgsVectorDataProvider::NativeType >()
        << QgsVectorDataProvider::NativeType( tr( "Whole number (integer)" ), QStringLiteral( "integer" ), QVariant::Int, 0, 10 )
        << QgsVectorDataProvider::NativeType( tr( "Decimal number (double)" ), QStringLiteral( "double precision" ), QVariant::Double, -1, -1, -1, -1 )
        << QgsVectorDataProvider::NativeType( tr( "Text (string)" ), QStringLiteral( "string" ), QVariant::String )
        // date time
        << QgsVectorDataProvider::NativeType( tr( "Date" ), QStringLiteral( "date" ), QVariant::Date, -1, -1, -1, -1 )
        << QgsVectorDataProvider::NativeType( tr( "Time" ), QStringLiteral( "time" ), QVariant::Time, -1, -1, -1, -1 )
        << QgsVectorDataProvider::NativeType( tr( "Date & Time" ), QStringLiteral( "datetime" ), QVariant::DateTime, -1, -1, -1, -1 )
        // string types
        << QgsVectorDataProvider::NativeType( tr( "Text, unlimited length (text)" ), QStringLiteral( "text" ), QVariant::String, -1, -1, -1, -1 )
        // boolean
        << QgsVectorDataProvider::NativeType( tr( "Boolean" ), QStringLiteral( "bool" ), QVariant::Bool )
        // blob
        << QgsVectorDataProvider::NativeType( tr( "Binary object (BLOB)" ), QStringLiteral( "binary" ), QVariant::ByteArray ) ) :
      provider->nativeTypes();
 
  mOutputFieldTypeComboBox->clear();
  for ( int i = 0; i < typelist.size(); i++ )
  {
    mOutputFieldTypeComboBox->addItem( typelist[i].mTypeDesc );
    mOutputFieldTypeComboBox->setItemData( i, static_cast<int>( typelist[i].mType ), Qt::UserRole + FTC_TYPE_ROLE_IDX );
    mOutputFieldTypeComboBox->setItemData( i, typelist[i].mTypeName, Qt::UserRole + FTC_TYPE_NAME_IDX );
    mOutputFieldTypeComboBox->setItemData( i, typelist[i].mMinLen, Qt::UserRole + FTC_MINLEN_IDX );
    mOutputFieldTypeComboBox->setItemData( i, typelist[i].mMaxLen, Qt::UserRole + FTC_MAXLEN_IDX );
    mOutputFieldTypeComboBox->setItemData( i, typelist[i].mMinPrec, Qt::UserRole + FTC_MINPREC_IDX );
    mOutputFieldTypeComboBox->setItemData( i, typelist[i].mMaxPrec, Qt::UserRole + FTC_MAXPREC_IDX );
    mOutputFieldTypeComboBox->setItemData( i, static_cast<int>( typelist[i].mSubType ), Qt::UserRole + FTC_SUBTYPE_IDX );
  }
  mOutputFieldTypeComboBox->blockSignals( false );
 
  const int idx = mOutputFieldTypeComboBox->findData( oldDataType, Qt::UserRole + FTC_TYPE_ROLE_IDX );
  if ( idx != -1 )
  {
    mOutputFieldTypeComboBox->setCurrentIndex( idx );
    mOutputFieldTypeComboBox_activated( idx );
  }
  else
  {
    mOutputFieldTypeComboBox->setCurrentIndex( 0 );
    mOutputFieldTypeComboBox_activated( 0 );
  }
}
 
void QgsFieldCalculator::mNewFieldGroupBox_toggled( bool on )
{
  mUpdateExistingGroupBox->setChecked( !on );
  if ( on && !mCanAddAttribute )
  {
    mOnlyVirtualFieldsInfoLabel->setVisible( true );
  }
  else
  {
    mOnlyVirtualFieldsInfoLabel->setVisible( false );
  }
 
  if ( ( mNewFieldGroupBox->isChecked() && mCreateVirtualFieldCheckbox->isChecked() ) || mVectorLayer->isEditable() )
  {
    mEditModeAutoTurnOnLabel->setVisible( false );
  }
  else
  {
    mEditModeAutoTurnOnLabel->setVisible( true );
  }
 
  mInfoIcon->setVisible( mOnlyVirtualFieldsInfoLabel->isVisible() || mEditModeAutoTurnOnLabel->isVisible() );
}
 
void QgsFieldCalculator::mUpdateExistingGroupBox_toggled( bool on )
{
  mNewFieldGroupBox->setChecked( !on );
  setOkButtonState();
 
  if ( on )
  {
    mOnlyUpdateSelectedCheckBox->setEnabled( mVectorLayer->selectedFeatureCount() > 0 );
  }
  else
  {
    mCreateVirtualFieldCheckbox_stateChanged( mCreateVirtualFieldCheckbox->checkState() );
  }
}
 
void QgsFieldCalculator::mCreateVirtualFieldCheckbox_stateChanged( int state )
{
  mOnlyUpdateSelectedCheckBox->setChecked( false );
  mOnlyUpdateSelectedCheckBox->setEnabled( state != Qt::Checked && mVectorLayer->selectedFeatureCount() > 0 );
 
  if ( ( mNewFieldGroupBox->isChecked() && mCreateVirtualFieldCheckbox->isChecked() ) || mVectorLayer->isEditable() )
  {
    mEditModeAutoTurnOnLabel->setVisible( false );
  }
  else
  {
    mEditModeAutoTurnOnLabel->setVisible( true );
  }
  populateOutputFieldTypes();
  mInfoIcon->setVisible( mOnlyVirtualFieldsInfoLabel->isVisible() || mEditModeAutoTurnOnLabel->isVisible() );
}
 
 
void QgsFieldCalculator::mOutputFieldNameLineEdit_textChanged( const QString &text )
{
  Q_UNUSED( text )
  setOkButtonState();
}
 
 
void QgsFieldCalculator::mOutputFieldTypeComboBox_activated( int index )
{
  mOutputFieldWidthSpinBox->setMinimum( mOutputFieldTypeComboBox->itemData( index, Qt::UserRole + FTC_MINLEN_IDX ).toInt() );
  mOutputFieldWidthSpinBox->setMaximum( mOutputFieldTypeComboBox->itemData( index, Qt::UserRole + FTC_MAXLEN_IDX ).toInt() );
  mOutputFieldWidthSpinBox->setEnabled( mOutputFieldWidthSpinBox->minimum() < mOutputFieldWidthSpinBox->maximum() );
  if ( mOutputFieldWidthSpinBox->value() < mOutputFieldWidthSpinBox->minimum() )
    mOutputFieldWidthSpinBox->setValue( mOutputFieldWidthSpinBox->minimum() );
  if ( mOutputFieldWidthSpinBox->value() > mOutputFieldWidthSpinBox->maximum() )
    mOutputFieldWidthSpinBox->setValue( mOutputFieldWidthSpinBox->maximum() );
 
  setPrecisionMinMax();
}
 
void QgsFieldCalculator::populateFields()
{
  if ( !mVectorLayer )
    return;
 
  const QgsFields &fields = mVectorLayer->fields();
  for ( int idx = 0; idx < fields.count(); ++idx )
  {
    switch ( fields.fieldOrigin( idx ) )
    {
      case QgsFields::OriginExpression:
      case QgsFields::OriginUnknown:
 
        continue; // can't be edited
 
      case QgsFields::OriginProvider:
      case QgsFields::OriginEdit:
        break; // can always be edited
 
      case QgsFields::OriginJoin:
      {
        // show joined fields (e.g. auxiliary fields) only if they have a non-hidden editor widget.
        // This enables them to be bulk field-calculated when a user needs to, but hides them by default
        // (since there's often MANY of these, e.g. after using the label properties tool on a layer)
        if ( fields.at( idx ).editorWidgetSetup().type() == QLatin1String( "Hidden" ) )
          continue;
 
        // only show editable joins
        int srcFieldIndex;
        const QgsVectorLayerJoinInfo *info = mVectorLayer->joinBuffer()->joinForFieldIndex( idx, fields, srcFieldIndex );
 
        if ( !info || !info->isEditable() )
          continue; // join is not editable
 
        break;
      }
    }
 
    const QString fieldName = fields.at( idx ).name();
 
    //insert into field combo box
    mExistingFieldComboBox->addItem( fields.iconForField( idx ), fieldName, idx );
  }
 
  if ( mVectorLayer->geometryType() != QgsWkbTypes::NullGeometry )
  {
    mExistingFieldComboBox->addItem( tr( "<geometry>" ), "geom" );
 
    QFont font = mExistingFieldComboBox->itemData( mExistingFieldComboBox->count() - 1, Qt::FontRole ).value<QFont>();
    font.setItalic( true );
    mExistingFieldComboBox->setItemData( mExistingFieldComboBox->count() - 1, font, Qt::FontRole );
  }
  mExistingFieldComboBox->setCurrentIndex( -1 );
}
 
void QgsFieldCalculator::setOkButtonState()
{
  QPushButton *okButton = mButtonBox->button( QDialogButtonBox::Ok );
 
  if ( ( mNewFieldGroupBox->isChecked() || !mUpdateExistingGroupBox->isEnabled() )
       && mOutputFieldNameLineEdit->text().isEmpty() )
  {
    okButton->setToolTip( tr( "Please enter a field name" ) );
    okButton->setEnabled( false );
    return;
  }
 
  if ( !builder->isExpressionValid() )
  {
    okButton->setToolTip( okButton->toolTip() + tr( "\n The expression is invalid see (more info) for details" ) );
    okButton->setEnabled( false );
    return;
  }
 
  okButton->setToolTip( QString() );
  okButton->setEnabled( true );
}
 
void QgsFieldCalculator::setPrecisionMinMax()
{
  const int idx = mOutputFieldTypeComboBox->currentIndex();
  const int minPrecType = mOutputFieldTypeComboBox->itemData( idx, Qt::UserRole + FTC_MINPREC_IDX ).toInt();
  const int maxPrecType = mOutputFieldTypeComboBox->itemData( idx, Qt::UserRole + FTC_MAXPREC_IDX ).toInt();
  const bool precisionIsEnabled = minPrecType < maxPrecType;
  mOutputFieldPrecisionSpinBox->setEnabled( precisionIsEnabled );
  // Do not set min/max if it's disabled or we'll loose the default value,
  // see https://github.com/qgis/QGIS/issues/26880 - QGIS saves integer field when
  // I create a new real field through field calculator (Update field works as intended)
  if ( precisionIsEnabled )
  {
    mOutputFieldPrecisionSpinBox->setMinimum( minPrecType );
    mOutputFieldPrecisionSpinBox->setMaximum( std::max( minPrecType, std::min( maxPrecType, mOutputFieldWidthSpinBox->value() ) ) );
  }
}
 
void QgsFieldCalculator::showHelp()
{
  QgsHelp::openHelp( QStringLiteral( "working_with_vector/attribute_table.html#editing-attribute-values" ) );
}
 
QgsField QgsFieldCalculator::fieldDefinition()
{
  return QgsField( mOutputFieldNameLineEdit->text(),
                   static_cast< QVariant::Type >( mOutputFieldTypeComboBox->currentData( Qt::UserRole + FTC_TYPE_ROLE_IDX ).toInt() ),
                   mOutputFieldTypeComboBox->currentData( Qt::UserRole + FTC_TYPE_NAME_IDX ).toString(),
                   mOutputFieldWidthSpinBox->value(),
                   mOutputFieldPrecisionSpinBox->isEnabled() ? mOutputFieldPrecisionSpinBox->value() : 0,
                   QString(),
                   static_cast< QVariant::Type >( mOutputFieldTypeComboBox->currentData( Qt::UserRole + FTC_SUBTYPE_IDX ).toInt() )
                 );
}