qgsexpressioncontextutils.cpp

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/***************************************************************************
     qgsexpressioncontextutils.cpp
     ------------------------
    Date                 : April 2015
    Copyright            : (C) 2015 by Nyall Dawson
    Email                : nyall dot dawson at gmail dot 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 "qgsexpressioncontextutils.h"
 
#include "qgsapplication.h"
#include "qgsexpression.h"
#include "qgsexpressionnodeimpl.h"
#include "qgsexpressionutils.h"
#include "qgsfeatureid.h"
#include "qgslayoutatlas.h"
#include "qgslayoutitem.h"
#include "qgslayoutitemmap.h"
#include "qgslayoutmultiframe.h"
#include "qgslayoutpagecollection.h"
#include "qgslayoutrendercontext.h"
#include "qgslayoutreportcontext.h"
#include "qgsmaplayerfactory.h"
#include "qgsmaplayerlistutils_p.h"
#include "qgsmapsettings.h"
#include "qgsmarkersymbol.h"
#include "qgsmeshlayer.h"
#include "qgsprocessingalgorithm.h"
#include "qgsprocessingcontext.h"
#include "qgsprocessingmodelalgorithm.h"
#include "qgsproject.h"
#include "qgsprojoperation.h"
#include "qgsproviderregistry.h"
#include "qgstriangularmesh.h"
#include "qgsunittypes.h"
#include "qgsvectorlayer.h"
#include "qgsvectortileutils.h"
 
#include <QString>
 
using namespace Qt::StringLiterals;
 
QgsExpressionContextScope *QgsExpressionContextUtils::globalScope()
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Global" ) );
 
  const QVariantMap customVariables = QgsApplication::customVariables();
 
  for ( QVariantMap::const_iterator it = customVariables.constBegin(); it != customVariables.constEnd(); ++it )
  {
    scope->setVariable( it.key(), it.value(), true );
  }
 
  //add some extra global variables
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"qgis_version"_s, Qgis::version(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"qgis_version_no"_s, Qgis::versionInt(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"qgis_short_version"_s, u"%1.%2"_s.arg( Qgis::versionInt() / 10000 ).arg( Qgis::versionInt() / 100 % 100 ), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"qgis_release_name"_s, Qgis::releaseName(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"qgis_platform"_s, QgsApplication::platform(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"qgis_os_name"_s, QgsApplication::osName(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"qgis_locale"_s, QgsApplication::locale(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"user_account_name"_s, QgsApplication::userLoginName(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"user_full_name"_s, QgsApplication::userFullName(), true, true ) );
 
  return scope;
}
 
void QgsExpressionContextUtils::setGlobalVariable( const QString &name, const QVariant &value )
{
  QgsApplication::setCustomVariable( name, value );
}
 
void QgsExpressionContextUtils::setGlobalVariables( const QVariantMap &variables )
{
  QgsApplication::setCustomVariables( variables );
}
 
void QgsExpressionContextUtils::removeGlobalVariable( const QString &name )
{
  QVariantMap vars = QgsApplication::customVariables();
  if ( vars.remove( name ) )
    QgsApplication::setCustomVariables( vars );
}

 
class GetLayoutItemVariables : public QgsScopedExpressionFunction
{
  public:
    GetLayoutItemVariables( const QgsLayout *c )
      : QgsScopedExpressionFunction( u"item_variables"_s, QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( u"id"_s ), u"Layout"_s )
      , mLayout( c )
    {}
 
    QVariant func( const QVariantList &values, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( !mLayout )
        return QVariant();
 
      const QString id = values.at( 0 ).toString();
 
      const QgsLayoutItem *item = mLayout->itemById( id );
      if ( !item )
        return QVariant();
 
      const QgsExpressionContext c = item->createExpressionContext();
 
      return c.variablesToMap();
    }
 
    QgsScopedExpressionFunction *clone() const override
    {
      return new GetLayoutItemVariables( mLayout );
    }
 
  private:
 
    const QgsLayout *mLayout = nullptr;
 
};
 
 
class GetLayoutMapLayerCredits : public QgsScopedExpressionFunction
{
  public:
    GetLayoutMapLayerCredits( const QgsLayout *c )
      : QgsScopedExpressionFunction( u"map_credits"_s,
                                     QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( u"id"_s, true )
                                     << QgsExpressionFunction::Parameter( u"include_layer_names"_s, true, false )
                                     << QgsExpressionFunction::Parameter( u"layer_name_separator"_s, true, u": "_s ), u"Layout"_s )
      , mLayout( c )
    {}
 
    QVariant func( const QVariantList &values, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( !mLayout )
        return QVariant();
 
      const QString id = values.value( 0 ).toString();
      const bool includeLayerNames = values.value( 1 ).toBool();
      const QString layerNameSeparator = values.value( 2 ).toString();
 
      QList< QgsLayoutItemMap * > maps;
      mLayout->layoutItems( maps );
 
      // collect all the layers in matching maps first
      QList< const QgsMapLayer * > layers;
      bool foundMap = false;
      for ( QgsLayoutItemMap *map : std::as_const( maps ) )
      {
        if ( !id.isEmpty() && map->id() != id )
          continue;
 
        foundMap = true;
 
        const QgsExpressionContext c = map->createExpressionContext();
        const QVariantList mapLayers = c.variable( u"map_layers"_s ).toList();
 
 
        for ( const QVariant &value : mapLayers )
        {
          if ( const QgsMapLayer *layer = qobject_cast< const QgsMapLayer * >( value.value< QObject * >() ) )
          {
            if ( !layers.contains( layer ) )
              layers << layer;
          }
        }
      }
      if ( !foundMap )
        return QVariant();
 
      QVariantList res;
      res.reserve( layers.size() );
      for ( const QgsMapLayer *layer : std::as_const( layers ) )
      {
        const QStringList credits = !layer->metadata().rights().isEmpty() ? layer->metadata().rights() : QStringList() << layer->serverProperties()->attribution();
        for ( const QString &credit : credits )
        {
          if ( credit.trimmed().isEmpty() )
            continue;
 
          const QString creditString = includeLayerNames ? layer->name() + layerNameSeparator + credit
                                       : credit;
 
          if ( !res.contains( creditString ) )
            res << creditString;
        }
      }
 
      return res;
    }
 
    QgsScopedExpressionFunction *clone() const override
    {
      return new GetLayoutMapLayerCredits( mLayout );
    }
 
  private:
 
    const QgsLayout *mLayout = nullptr;
 
};
 
class GetCurrentFormFieldValue : public QgsScopedExpressionFunction
{
  public:
    GetCurrentFormFieldValue( )
      : QgsScopedExpressionFunction( u"current_value"_s, QgsExpressionFunction::ParameterList() << u"field_name"_s, u"Form"_s )
    {}
 
    QVariant func( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      const QString fieldName( values.at( 0 ).toString() );
      const QgsFeature feat( context->variable( u"current_feature"_s ).value<QgsFeature>() );
      if ( fieldName.isEmpty() || ! feat.isValid( ) )
      {
        return QVariant();
      }
      return feat.attribute( fieldName ) ;
    }
 
    QgsScopedExpressionFunction *clone() const override
    {
      return new GetCurrentFormFieldValue( );
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    };
 
};
 
class GetCurrentParentFormFieldValue : public QgsScopedExpressionFunction
{
  public:
    GetCurrentParentFormFieldValue( )
      : QgsScopedExpressionFunction( u"current_parent_value"_s, QgsExpressionFunction::ParameterList() << u"field_name"_s, u"Form"_s )
    {}
 
    QVariant func( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      const QString fieldName( values.at( 0 ).toString() );
      const QgsFeature feat( context->variable( u"current_parent_feature"_s ).value<QgsFeature>() );
      if ( fieldName.isEmpty() || ! feat.isValid( ) )
      {
        return QVariant();
      }
      return feat.attribute( fieldName ) ;
    }
 
    QgsScopedExpressionFunction *clone() const override
    {
      return new GetCurrentParentFormFieldValue( );
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    };
 
};
 
 
class GetProcessingParameterValue : public QgsScopedExpressionFunction
{
  public:
    GetProcessingParameterValue( const QVariantMap &params )
      : QgsScopedExpressionFunction( u"parameter"_s, QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( u"name"_s ), u"Processing"_s )
      , mParams( params )
    {}
 
    QVariant func( const QVariantList &values, const QgsExpressionContext *, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      return mParams.value( values.at( 0 ).toString() );
    }
 
    QgsScopedExpressionFunction *clone() const override
    {
      return new GetProcessingParameterValue( mParams );
    }
 
  private:
 
    const QVariantMap mParams;
 
};

 
 
QgsExpressionContextScope *QgsExpressionContextUtils::formScope( const QgsFeature &formFeature, const QString &formMode )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Form" ) );
  scope->addFunction( u"current_value"_s, new GetCurrentFormFieldValue( ) );
  scope->setVariable( u"current_geometry"_s, formFeature.geometry( ), true );
  scope->setVariable( u"current_feature"_s, formFeature, true );
  scope->setVariable( u"form_mode"_s, formMode, true );
  return scope;
}
 
 
QgsExpressionContextScope *QgsExpressionContextUtils::parentFormScope( const QgsFeature &parentFormFeature, const QString &parentFormMode )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Parent Form" ) );
  scope->addFunction( u"current_parent_value"_s, new GetCurrentParentFormFieldValue( ) );
  scope->setVariable( u"current_parent_geometry"_s, parentFormFeature.geometry( ), true );
  scope->setVariable( u"current_parent_feature"_s, parentFormFeature, true );
  scope->setVariable( u"parent_form_mode"_s, parentFormMode, true );
  return scope;
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::projectScope( const QgsProject *project )
{
  if ( !project )
  {
    QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Project" ) );
    return scope;
  }
  else
    return project->createExpressionContextScope();
}
 
void QgsExpressionContextUtils::setProjectVariable( QgsProject *project, const QString &name, const QVariant &value )
{
  if ( !project )
    return;
 
  QVariantMap vars = project->customVariables();
 
  vars.insert( name, value );
 
  project->setCustomVariables( vars );
}
 
void QgsExpressionContextUtils::setProjectVariables( QgsProject *project, const QVariantMap &variables )
{
  if ( !project )
    return;
 
  project->setCustomVariables( variables );
}
 
void QgsExpressionContextUtils::removeProjectVariable( QgsProject *project, const QString &name )
{
  if ( !project )
  {
    return;
  }
 
  QVariantMap vars = project->customVariables();
  if ( vars.remove( name ) )
    project->setCustomVariables( vars );
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::layerScope( const QgsMapLayer *layer )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Layer" ) );
 
  if ( !layer )
    return scope;
 
  //add variables defined in layer properties
  const QStringList variableNames = layer->customProperty( u"variableNames"_s ).toStringList();
  const QStringList variableValues = layer->customProperty( u"variableValues"_s ).toStringList();
 
  int varIndex = 0;
  for ( const QString &variableName : variableNames )
  {
    if ( varIndex >= variableValues.length() )
    {
      break;
    }
 
    const QVariant varValue = variableValues.at( varIndex );
    varIndex++;
    scope->setVariable( variableName, varValue, true );
  }
 
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_name"_s, layer->name(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_id"_s, layer->id(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"_layer_crs"_s, QVariant::fromValue<QgsCoordinateReferenceSystem>( layer->crs() ), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_crs"_s, layer->crs().authid(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer"_s, QVariant::fromValue<QgsWeakMapLayerPointer >( QgsWeakMapLayerPointer( const_cast<QgsMapLayer *>( layer ) ) ), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_crs_ellipsoid"_s, layer->crs().ellipsoidAcronym(), true, true ) );
 
 
  const QgsCoordinateReferenceSystem verticalCrs = layer->verticalCrs();
  if ( verticalCrs.isValid() )
  {
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_vertical_crs"_s, verticalCrs.authid(), true, true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_vertical_crs_definition"_s, verticalCrs.toProj(), true, true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_vertical_crs_description"_s, verticalCrs.description(), true, true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_vertical_crs_wkt"_s, verticalCrs.toWkt( Qgis::CrsWktVariant::Preferred ), true ) );
  }
 
  const QgsVectorLayer *vLayer = qobject_cast< const QgsVectorLayer * >( layer );
  if ( vLayer )
  {
    scope->setFields( vLayer->fields() );
  }
 
  //TODO - add functions. Possibilities include:
  //is_selected
  //field summary stats
 
  return scope;
}
 
QList<QgsExpressionContextScope *> QgsExpressionContextUtils::globalProjectLayerScopes( const QgsMapLayer *layer )
{
  QList<QgsExpressionContextScope *> scopes;
  scopes << globalScope();
 
  QgsProject *project = QgsProject::instance();  // TODO: use project associated with layer skip-keyword-check
  if ( project )
    scopes << projectScope( project );
 
  if ( layer )
    scopes << layerScope( layer );
  return scopes;
}
 
 
void QgsExpressionContextUtils::setLayerVariable( QgsMapLayer *layer, const QString &name, const QVariant &value )
{
  if ( !layer )
    return;
 
  // write variable to layer
  QStringList variableNames = layer->customProperty( u"variableNames"_s ).toStringList();
  QStringList variableValues = layer->customProperty( u"variableValues"_s ).toStringList();
 
  // Set variable value if it is already in list
  const int index = variableNames.indexOf( name );
  if ( index != -1 )
  {
    variableValues[ index ] = value.toString();
  }
  // Otherwise, append it to the list
  else
  {
    variableNames << name;
    variableValues << value.toString();
  }
 
  layer->setCustomProperty( u"variableNames"_s, variableNames );
  layer->setCustomProperty( u"variableValues"_s, variableValues );
}
 
void QgsExpressionContextUtils::setLayerVariables( QgsMapLayer *layer, const QVariantMap &variables )
{
  if ( !layer )
    return;
 
  QStringList variableNames;
  QStringList variableValues;
 
  QVariantMap::const_iterator it = variables.constBegin();
  for ( ; it != variables.constEnd(); ++it )
  {
    variableNames << it.key();
    variableValues << it.value().toString();
  }
 
  layer->setCustomProperty( u"variableNames"_s, variableNames );
  layer->setCustomProperty( u"variableValues"_s, variableValues );
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::mapSettingsScope( const QgsMapSettings &mapSettings )
{
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  // and because people don't read that ^^, I'm going to blast it all over this function
 
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Map Settings" ) );
 
  //add known map settings context variables
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_id"_s, "canvas", true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_rotation"_s, mapSettings.rotation(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_scale"_s, mapSettings.scale(), true ) );
 
  scope->setVariable( u"zoom_level"_s, QgsVectorTileUtils::scaleToZoomLevel( mapSettings.scale(), 0, 99999 ), true );
  scope->setVariable( u"vector_tile_zoom"_s, QgsVectorTileUtils::scaleToZoom( mapSettings.scale() ), true );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  const QgsGeometry extent = QgsGeometry::fromRect( mapSettings.visibleExtent() );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_extent"_s, QVariant::fromValue( extent ), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_extent_width"_s, mapSettings.visibleExtent().width(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_extent_height"_s, mapSettings.visibleExtent().height(), true ) );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  const QgsGeometry centerPoint = QgsGeometry::fromPointXY( mapSettings.visibleExtent().center() );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_extent_center"_s, QVariant::fromValue( centerPoint ), true ) );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs"_s, mapSettings.destinationCrs().authid(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs_definition"_s, mapSettings.destinationCrs().toProj(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_units"_s, QgsUnitTypes::toString( mapSettings.mapUnits() ), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs_description"_s, mapSettings.destinationCrs().description(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs_acronym"_s, mapSettings.destinationCrs().projectionAcronym(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs_projection"_s, mapSettings.destinationCrs().operation().description(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs_ellipsoid"_s, mapSettings.destinationCrs().ellipsoidAcronym(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs_proj4"_s, mapSettings.destinationCrs().toProj(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_crs_wkt"_s, mapSettings.destinationCrs().toWkt( Qgis::CrsWktVariant::Preferred ), true ) );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  QVariantList layersIds;
  QVariantList layers;
  const QList<QgsMapLayer *> layersInMap = mapSettings.layers( true );
  layersIds.reserve( layersInMap.count() );
  layers.reserve( layersInMap.count() );
  for ( QgsMapLayer *layer : layersInMap )
  {
    layersIds << layer->id();
    layers << QVariant::fromValue<QgsWeakMapLayerPointer>( QgsWeakMapLayerPointer( layer ) );
  }
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_layer_ids"_s, layersIds, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_layers"_s, layers, true ) );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  scope->addFunction( u"is_layer_visible"_s, new GetLayerVisibility( mapSettings.layers( true ), mapSettings.scale() ) );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_start_time"_s, mapSettings.isTemporal() ? mapSettings.temporalRange().begin() : QVariant(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_end_time"_s, mapSettings.isTemporal() ? mapSettings.temporalRange().end() : QVariant(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_interval"_s, mapSettings.isTemporal() ? QgsInterval( mapSettings.temporalRange().end() - mapSettings.temporalRange().begin() ) : QVariant(), true ) );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  const QgsDoubleRange zRange = mapSettings.zRange();
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_z_range_lower"_s, !zRange.isInfinite() ? zRange.lower() : QVariant(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"map_z_range_upper"_s, !zRange.isInfinite() ? zRange.upper() : QVariant(), true ) );
 
  // IMPORTANT: ANY CHANGES HERE ALSO NEED TO BE MADE TO QgsLayoutItemMap::createExpressionContext()
  // (rationale is described in QgsLayoutItemMap::createExpressionContext() )
 
  if ( mapSettings.frameRate() >= 0 )
    scope->setVariable( u"frame_rate"_s, mapSettings.frameRate(), true );
  if ( mapSettings.currentFrame() >= 0 )
    scope->setVariable( u"frame_number"_s, mapSettings.currentFrame(), true );
 
  return scope;
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::mapToolCaptureScope( const QList<QgsPointLocator::Match> &matches )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Map Tool Capture" ) );
 
  QVariantList matchList;
 
  for ( const QgsPointLocator::Match &match : matches )
  {
    QVariantMap matchMap;
 
    matchMap.insert( u"valid"_s, match.isValid() );
    matchMap.insert( u"layer"_s, QVariant::fromValue<QgsWeakMapLayerPointer>( QgsWeakMapLayerPointer( match.layer() ) ) );
    matchMap.insert( u"feature_id"_s, match.featureId() );
    matchMap.insert( u"vertex_index"_s, match.vertexIndex() );
    matchMap.insert( u"distance"_s, match.distance() );
 
    matchList.append( matchMap );
  }
 
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"snapping_results"_s, matchList ) );
 
  return scope;
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::mapLayerPositionScope( const QgsPointXY &position )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Map Layer Position" ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layer_cursor_point"_s, QVariant::fromValue( QgsGeometry::fromPointXY( position ) ) ) );
  return scope;
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::updateSymbolScope( const QgsSymbol *symbol, QgsExpressionContextScope *symbolScope )
{
  if ( !symbolScope )
    return nullptr;
 
  symbolScope->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_SYMBOL_COLOR, symbol ? symbol->color() : QColor(), true ) );
 
  double angle = 0.0;
  const QgsMarkerSymbol *markerSymbol = dynamic_cast< const QgsMarkerSymbol * >( symbol );
  if ( markerSymbol )
  {
    angle = markerSymbol->angle();
  }
  symbolScope->addVariable( QgsExpressionContextScope::StaticVariable( QgsExpressionContext::EXPR_SYMBOL_ANGLE, angle, true ) );
 
  return symbolScope;
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::layoutScope( const QgsLayout *layout )
{
  auto scope = std::make_unique<QgsExpressionContextScope>( QObject::tr( "Layout" ) );
  if ( !layout )
    return scope.release();
 
  //add variables defined in layout properties
  const QStringList variableNames = layout->customProperty( u"variableNames"_s ).toStringList();
  const QStringList variableValues = layout->customProperty( u"variableValues"_s ).toStringList();
 
  int varIndex = 0;
 
  for ( const QString &variableName : variableNames )
  {
    if ( varIndex >= variableValues.length() )
    {
      break;
    }
 
    const QVariant varValue = variableValues.at( varIndex );
    varIndex++;
    scope->setVariable( variableName, varValue );
  }
 
  //add known layout context variables
  if ( const QgsMasterLayoutInterface *l = dynamic_cast< const QgsMasterLayoutInterface * >( layout ) )
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_name"_s, l->name(), true ) );
 
  // get the list of pages
  QList<int> pages;
  for ( int i = 0; i < layout->pageCollection()->pageCount(); i++ )
  {
    if ( layout->renderContext().isPreviewRender() || ( layout->pageCollection()->shouldExportPage( i ) ) )
    {
      pages << i;
    }
  }
 
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_numpages"_s, pages.size(), true ) );
  if ( layout->pageCollection()->pageCount() > 0 )
  {
    // just take first page size
    const QSizeF s = layout->pageCollection()->page( 0 )->sizeWithUnits().toQSizeF();
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_pageheight"_s, s.height(), true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_pagewidth"_s, s.width(), true ) );
  }
 
  QVariantList offsets;
  for ( int i = 0; i < layout->pageCollection()->pageCount(); i++ )
  {
    if ( pages.contains( i ) )
    {
      const QPointF p = layout->pageCollection()->pagePositionToLayoutPosition( i, QgsLayoutPoint( 0, 0 ) );
      offsets << p.y();
    }
  }
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_pageoffsets"_s, offsets, true ) );
 
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_dpi"_s, layout->renderContext().dpi(), true ) );
 
  scope->addFunction( u"item_variables"_s, new GetLayoutItemVariables( layout ) );
  scope->addFunction( u"map_credits"_s, new GetLayoutMapLayerCredits( layout ) );
 
  if ( layout->reportContext().layer() )
  {
    scope->setFields( layout->reportContext().layer()->fields() );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_layerid"_s, layout->reportContext().layer()->id(), true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_layername"_s, layout->reportContext().layer()->name(), true ) );
  }
 
  if ( layout->reportContext().feature().isValid() )
  {
    const QgsFeature atlasFeature = layout->reportContext().feature();
    scope->setFeature( atlasFeature );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_feature"_s, QVariant::fromValue( atlasFeature ), true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_featureid"_s, FID_IS_NULL( atlasFeature.id() ) ? QVariant() : atlasFeature.id(), true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_geometry"_s, QVariant::fromValue( atlasFeature.geometry() ), true ) );
  }
 
  return scope.release();
}
 
void QgsExpressionContextUtils::setLayoutVariable( QgsLayout *layout, const QString &name, const QVariant &value )
{
  if ( !layout )
    return;
 
  //write variable to layout
  QStringList variableNames = layout->customProperty( u"variableNames"_s ).toStringList();
  QStringList variableValues = layout->customProperty( u"variableValues"_s ).toStringList();
 
  variableNames << name;
  variableValues << value.toString();
 
  layout->setCustomProperty( u"variableNames"_s, variableNames );
  layout->setCustomProperty( u"variableValues"_s, variableValues );
}
 
void QgsExpressionContextUtils::setLayoutVariables( QgsLayout *layout, const QVariantMap &variables )
{
  if ( !layout )
    return;
 
  QStringList variableNames;
  QStringList variableValues;
 
  QVariantMap::const_iterator it = variables.constBegin();
  for ( ; it != variables.constEnd(); ++it )
  {
    variableNames << it.key();
    variableValues << it.value().toString();
  }
 
  layout->setCustomProperty( u"variableNames"_s, variableNames );
  layout->setCustomProperty( u"variableValues"_s, variableValues );
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::atlasScope( const QgsLayoutAtlas *atlas )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Atlas" ) );
  if ( !atlas )
  {
    //add some dummy atlas variables. This is done so that as in certain contexts we want to show
    //users that these variables are available even if they have no current value
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_pagename"_s, QString(), true, true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_feature"_s, QVariant::fromValue( QgsFeature() ), true, true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_featureid"_s, QVariant(), true, true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_geometry"_s, QVariant::fromValue( QgsGeometry() ), true, true ) );
    return scope;
  }
 
  //add known atlas variables
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_totalfeatures"_s, atlas->count(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_featurenumber"_s, atlas->currentFeatureNumber() + 1, true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_filename"_s, atlas->currentFilename(), true, true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_pagename"_s, atlas->nameForPage( atlas->currentFeatureNumber() ), true, true ) );
 
  if ( atlas->enabled() && atlas->coverageLayer() )
  {
    scope->setFields( atlas->coverageLayer()->fields() );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_layerid"_s, atlas->coverageLayer()->id(), true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_layername"_s, atlas->coverageLayer()->name(), true ) );
  }
 
  if ( atlas->enabled() )
  {
    const QgsFeature atlasFeature = atlas->layout()->reportContext().feature();
    scope->setFeature( atlasFeature );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_feature"_s, QVariant::fromValue( atlasFeature ), true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_featureid"_s, FID_IS_NULL( atlasFeature.id() ) ? QVariant() : atlasFeature.id(), true ) );
    scope->addVariable( QgsExpressionContextScope::StaticVariable( u"atlas_geometry"_s, QVariant::fromValue( atlasFeature.geometry() ), true ) );
  }
 
  return scope;
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::layoutItemScope( const QgsLayoutItem *item )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Layout Item" ) );
  if ( !item )
    return scope;
 
  //add variables defined in layout item properties
  const QStringList variableNames = item->customProperty( u"variableNames"_s ).toStringList();
  const QStringList variableValues = item->customProperty( u"variableValues"_s ).toStringList();
 
  int varIndex = 0;
  for ( const QString &variableName : variableNames )
  {
    if ( varIndex >= variableValues.length() )
    {
      break;
    }
 
    const QVariant varValue = variableValues.at( varIndex );
    varIndex++;
    scope->setVariable( variableName, varValue );
  }
 
  int itemPage = 1;
  bool itemPageFound = false;
  if ( item->layout() )
  {
    for ( int i = 0; i < item->layout()->pageCollection()->pageCount(); i++ )
    {
      if ( item->layout()->renderContext().isPreviewRender() || ( item->layout()->pageCollection()->shouldExportPage( i ) ) )
      {
        if ( i == item->page() )
        {
          itemPageFound = true;
          break;
        }
 
        itemPage++;
      }
    }
  }
  if ( !itemPageFound )
  {
    itemPage = -1;
  }
 
  //add known layout item context variables
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"item_id"_s, item->id(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"item_uuid"_s, item->uuid(), true ) );
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_page"_s, itemPage, true ) );
 
  if ( item->layout() )
  {
    const QgsLayoutItemPage *page = item->layout()->pageCollection()->page( item->page() );
    if ( page )
    {
      const QSizeF s = page->sizeWithUnits().toQSizeF();
      scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_pageheight"_s, s.height(), true ) );
      scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_pagewidth"_s, s.width(), true ) );
    }
    else
    {
      scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_pageheight"_s, QVariant(), true ) );
      scope->addVariable( QgsExpressionContextScope::StaticVariable( u"layout_pagewidth"_s, QVariant(), true ) );
    }
  }
 
  return scope;
}
 
void QgsExpressionContextUtils::setLayoutItemVariable( QgsLayoutItem *item, const QString &name, const QVariant &value )
{
  if ( !item )
    return;
 
  //write variable to layout item
  QStringList variableNames = item->customProperty( u"variableNames"_s ).toStringList();
  QStringList variableValues = item->customProperty( u"variableValues"_s ).toStringList();
 
  variableNames << name;
  variableValues << value.toString();
 
  item->setCustomProperty( u"variableNames"_s, variableNames );
  item->setCustomProperty( u"variableValues"_s, variableValues );
}
 
void QgsExpressionContextUtils::setLayoutItemVariables( QgsLayoutItem *item, const QVariantMap &variables )
{
  if ( !item )
    return;
 
  QStringList variableNames;
  QStringList variableValues;
 
  QVariantMap::const_iterator it = variables.constBegin();
  for ( ; it != variables.constEnd(); ++it )
  {
    variableNames << it.key();
    variableValues << it.value().toString();
  }
 
  item->setCustomProperty( u"variableNames"_s, variableNames );
  item->setCustomProperty( u"variableValues"_s, variableValues );
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::multiFrameScope( const QgsLayoutMultiFrame *frame )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Multiframe Item" ) );
  if ( !frame )
    return scope;
 
  //add variables defined in layout item properties
  const QStringList variableNames = frame->customProperty( u"variableNames"_s ).toStringList();
  const QStringList variableValues = frame->customProperty( u"variableValues"_s ).toStringList();
 
  int varIndex = 0;
  for ( const QString &variableName : variableNames )
  {
    if ( varIndex >= variableValues.length() )
    {
      break;
    }
 
    const QVariant varValue = variableValues.at( varIndex );
    varIndex++;
    scope->setVariable( variableName, varValue );
  }
 
  return scope;
}
 
void QgsExpressionContextUtils::setLayoutMultiFrameVariable( QgsLayoutMultiFrame *frame, const QString &name, const QVariant &value )
{
  if ( !frame )
    return;
 
  //write variable to layout multiframe
  QStringList variableNames = frame->customProperty( u"variableNames"_s ).toStringList();
  QStringList variableValues = frame->customProperty( u"variableValues"_s ).toStringList();
 
  variableNames << name;
  variableValues << value.toString();
 
  frame->setCustomProperty( u"variableNames"_s, variableNames );
  frame->setCustomProperty( u"variableValues"_s, variableValues );
}
 
void QgsExpressionContextUtils::setLayoutMultiFrameVariables( QgsLayoutMultiFrame *frame, const QVariantMap &variables )
{
  if ( !frame )
    return;
 
  QStringList variableNames;
  QStringList variableValues;
 
  QVariantMap::const_iterator it = variables.constBegin();
  for ( ; it != variables.constEnd(); ++it )
  {
    variableNames << it.key();
    variableValues << it.value().toString();
  }
 
  frame->setCustomProperty( u"variableNames"_s, variableNames );
  frame->setCustomProperty( u"variableValues"_s, variableValues );
}
 
QgsExpressionContext QgsExpressionContextUtils::createFeatureBasedContext( const QgsFeature &feature, const QgsFields &fields )
{
  QgsExpressionContextScope *scope = new QgsExpressionContextScope();
  scope->setFeature( feature );
  scope->setFields( fields );
  return QgsExpressionContext() << scope;
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::processingAlgorithmScope( const QgsProcessingAlgorithm *algorithm, const QVariantMap &parameters, QgsProcessingContext &context )
{
  // set aside for future use
  Q_UNUSED( context )
 
  auto scope = std::make_unique<QgsExpressionContextScope>( QObject::tr( "Algorithm" ) );
  scope->addFunction( u"parameter"_s, new GetProcessingParameterValue( parameters ) );
 
  if ( !algorithm )
    return scope.release();
 
  //add standard algorithm variables
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"algorithm_id"_s, algorithm->id(), true ) );
 
  return scope.release();
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::processingModelAlgorithmScope( const QgsProcessingModelAlgorithm *model, const QVariantMap &, QgsProcessingContext &context )
{
  auto modelScope = std::make_unique<QgsExpressionContextScope>( QObject::tr( "Model" ) );
  QString modelPath;
  if ( !model->sourceFilePath().isEmpty() )
  {
    modelPath = model->sourceFilePath();
  }
  else if ( context.project() )
  {
    // fallback to project path -- the model may be embedded in a project, OR an unsaved model. In either case the
    // project path is a logical value to fall back to
    modelPath = context.project()->projectStorage() ? context.project()->fileName() : context.project()->absoluteFilePath();
  }
 
  const QString modelFolder = !modelPath.isEmpty() ? QFileInfo( modelPath ).path() : QString();
  modelScope->addVariable( QgsExpressionContextScope::StaticVariable( u"model_path"_s, QDir::toNativeSeparators( modelPath ), true ) );
  modelScope->addVariable( QgsExpressionContextScope::StaticVariable( u"model_folder"_s, QDir::toNativeSeparators( modelFolder ), true, true ) );
  modelScope->addVariable( QgsExpressionContextScope::StaticVariable( u"model_name"_s, model->displayName(), true ) );
  modelScope->addVariable( QgsExpressionContextScope::StaticVariable( u"model_group"_s, model->group(), true ) );
 
  // custom variables
  const QVariantMap customVariables = model->variables();
  for ( auto it = customVariables.constBegin(); it != customVariables.constEnd(); ++it )
  {
    modelScope->addVariable( QgsExpressionContextScope::StaticVariable( it.key(), it.value(), true ) );
  }
 
  return modelScope.release();
}
 
QgsExpressionContextScope *QgsExpressionContextUtils::notificationScope( const QString &message )
{
  auto scope = std::make_unique<QgsExpressionContextScope>();
  scope->addVariable( QgsExpressionContextScope::StaticVariable( u"notification_message"_s, message, true ) );
  return scope.release();
}
 
void QgsExpressionContextUtils::registerContextFunctions()
{
  QgsExpression::registerFunction( new GetNamedProjectColor( nullptr ) );
  QgsExpression::registerFunction( new GetNamedProjectColorObject( nullptr ) );
  QgsExpression::registerFunction( new GetSensorData( ) );
  QgsExpression::registerFunction( new GetLayoutItemVariables( nullptr ) );
  QgsExpression::registerFunction( new GetLayoutMapLayerCredits( nullptr ) );
  QgsExpression::registerFunction( new GetLayerVisibility( QList<QgsMapLayer *>(), 0.0 ) );
  QgsExpression::registerFunction( new GetProcessingParameterValue( QVariantMap() ) );
  QgsExpression::registerFunction( new GetCurrentFormFieldValue( ) );
  QgsExpression::registerFunction( new GetCurrentParentFormFieldValue( ) );
  QgsExpression::registerFunction( new LoadLayerFunction( ) );
}
 
bool QgsScopedExpressionFunction::usesGeometry( const QgsExpressionNodeFunction *node ) const
{
  Q_UNUSED( node )
  return mUsesGeometry;
}
 
QSet<QString> QgsScopedExpressionFunction::referencedColumns( const QgsExpressionNodeFunction *node ) const
{
  Q_UNUSED( node )
  return mReferencedColumns;
}
 
bool QgsScopedExpressionFunction::isStatic( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
  return allParamsStatic( node, parent, context );
}
 
//
// GetLayerVisibility
//
 
QgsExpressionContextUtils::GetLayerVisibility::GetLayerVisibility( const QList<QgsMapLayer *> &layers, double scale )
  : QgsScopedExpressionFunction( u"is_layer_visible"_s, QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( u"id"_s ), u"General"_s )
  , mLayers( _qgis_listRawToQPointer( layers ) )
  , mScale( scale )
{
  for ( const auto &layer : mLayers )
  {
    if ( layer->hasScaleBasedVisibility() )
    {
      mScaleBasedVisibilityDetails[ layer ] = qMakePair( layer->minimumScale(), layer->maximumScale() );
    }
  }
}
 
QgsExpressionContextUtils::GetLayerVisibility::GetLayerVisibility()
  : QgsScopedExpressionFunction( u"is_layer_visible"_s, QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( u"id"_s ), u"General"_s )
{}
 
QVariant QgsExpressionContextUtils::GetLayerVisibility::func( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  if ( mLayers.isEmpty() )
  {
    return false;
  }
 
  bool isVisible = false;
  Q_NOWARN_DEPRECATED_PUSH
  QgsMapLayer *layer = QgsExpressionUtils::getMapLayer( values.at( 0 ), context, parent );
  Q_NOWARN_DEPRECATED_POP
  if ( layer && mLayers.contains( layer ) )
  {
    isVisible = true;
    if ( mScaleBasedVisibilityDetails.contains( layer ) && !qgsDoubleNear( mScale, 0.0 ) )
    {
      if ( ( !qgsDoubleNear( mScaleBasedVisibilityDetails[ layer ].first, 0.0 ) && mScale > mScaleBasedVisibilityDetails[ layer ].first ) ||
           ( !qgsDoubleNear( mScaleBasedVisibilityDetails[ layer ].second, 0.0 ) && mScale < mScaleBasedVisibilityDetails[ layer ].second ) )
      {
        isVisible = false;
      }
    }
  }
 
  return isVisible;
}
 
QgsScopedExpressionFunction *QgsExpressionContextUtils::GetLayerVisibility::clone() const
{
  GetLayerVisibility *func = new GetLayerVisibility();
  func->mLayers = mLayers;
  func->mScale = mScale;
  func->mScaleBasedVisibilityDetails = mScaleBasedVisibilityDetails;
  return func;
}
 
//
// mesh expression context
//

class CurrentVertexZValueExpressionFunction: public QgsScopedExpressionFunction
{
  public:
    CurrentVertexZValueExpressionFunction():
      QgsScopedExpressionFunction( "$vertex_z",
                                   0,
                                   u"Meshes"_s )
    {}
 
    QgsScopedExpressionFunction *clone() const override {return new CurrentVertexZValueExpressionFunction();}
 
    QVariant func( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( context &&
           context->hasVariable( u"_mesh_vertex_index"_s ) &&
           context->hasVariable( u"_native_mesh"_s ) )
      {
        int vertexIndex = context->variable( u"_mesh_vertex_index"_s ).toInt();
        const QgsMesh nativeMesh = qvariant_cast<QgsMesh>( context->variable( u"_native_mesh"_s ) );
        const QgsMeshVertex &vertex = nativeMesh.vertex( vertexIndex );
        if ( !vertex.isEmpty() )
          return vertex.z();
      }
 
      return QVariant();
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    }
};
 
class CurrentVertexXValueExpressionFunction: public QgsScopedExpressionFunction
{
  public:
    CurrentVertexXValueExpressionFunction():
      QgsScopedExpressionFunction( "$vertex_x",
                                   0,
                                   u"Meshes"_s )
    {}
 
    QgsScopedExpressionFunction *clone() const override {return new CurrentVertexXValueExpressionFunction();}
 
    QVariant func( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( context &&
           context->hasVariable( u"_mesh_vertex_index"_s ) &&
           context->hasVariable( u"_native_mesh"_s ) )
      {
        int vertexIndex = context->variable( u"_mesh_vertex_index"_s ).toInt();
        const QgsMesh nativeMesh = qvariant_cast<QgsMesh>( context->variable( u"_native_mesh"_s ) );
        const QgsMeshVertex &vertex = nativeMesh.vertex( vertexIndex );
        if ( !vertex.isEmpty() )
          return vertex.x();
      }
 
      return QVariant();
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    }
};
 
class CurrentVertexYValueExpressionFunction: public QgsScopedExpressionFunction
{
  public:
    CurrentVertexYValueExpressionFunction():
      QgsScopedExpressionFunction( "$vertex_y",
                                   0,
                                   u"Meshes"_s )
    {}
 
    QgsScopedExpressionFunction *clone() const override {return new CurrentVertexYValueExpressionFunction();}
 
    QVariant func( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( context &&
           context->hasVariable( u"_mesh_vertex_index"_s ) &&
           context->hasVariable( u"_native_mesh"_s ) )
      {
        int vertexIndex = context->variable( u"_mesh_vertex_index"_s ).toInt();
        const QgsMesh nativeMesh = qvariant_cast<QgsMesh>( context->variable( u"_native_mesh"_s ) );
        const QgsMeshVertex &vertex = nativeMesh.vertex( vertexIndex );
        if ( !vertex.isEmpty() )
          return vertex.y();
      }
 
      return QVariant();
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    }
};
 
class CurrentVertexExpressionFunction: public QgsScopedExpressionFunction
{
  public:
    CurrentVertexExpressionFunction():
      QgsScopedExpressionFunction( "$vertex_as_point",
                                   0,
                                   u"Meshes"_s )
    {}
 
    QgsScopedExpressionFunction *clone() const override {return new CurrentVertexExpressionFunction();}
 
    QVariant func( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( context &&
           context->hasVariable( u"_mesh_vertex_index"_s ) &&
           context->hasVariable( u"_native_mesh"_s ) )
      {
        int vertexIndex = context->variable( u"_mesh_vertex_index"_s ).toInt();
        const QgsMesh nativeMesh = qvariant_cast<QgsMesh>( context->variable( u"_native_mesh"_s ) );
        const QgsMeshVertex &vertex = nativeMesh.vertex( vertexIndex );
        if ( !vertex.isEmpty() )
          return QVariant::fromValue( QgsGeometry( new QgsPoint( vertex ) ) );
      }
 
      return QVariant();
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    }
};
 
class CurrentVertexIndexExpressionFunction: public QgsScopedExpressionFunction
{
  public:
    CurrentVertexIndexExpressionFunction():
      QgsScopedExpressionFunction( "$vertex_index",
                                   0,
                                   u"Meshes"_s )
    {}
 
    QgsScopedExpressionFunction *clone() const override {return new CurrentVertexIndexExpressionFunction();}
 
    QVariant func( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( !context )
        return QVariant();
 
      if ( !context->hasVariable( u"_mesh_vertex_index"_s ) )
        return QVariant();
 
      return context->variable( u"_mesh_vertex_index"_s );
    }
 
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    }
};
 
class CurrentFaceAreaExpressionFunction: public QgsScopedExpressionFunction
{
  public:
    CurrentFaceAreaExpressionFunction():
      QgsScopedExpressionFunction( "$face_area",
                                   0,
                                   u"Meshes"_s )
    {}
 
    QgsScopedExpressionFunction *clone() const override {return new CurrentFaceAreaExpressionFunction();}
 
    QVariant func( const QVariantList &, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * ) override
    {
      if ( context &&
           context->hasVariable( u"_mesh_face_index"_s ) &&
           context->hasVariable( u"_native_mesh"_s ) )
      {
        const int faceIndex = context->variable( u"_mesh_face_index"_s ).toInt();
        const QgsMesh nativeMesh = qvariant_cast<QgsMesh>( context->variable( u"_native_mesh"_s ) );
        const QgsMeshFace &face = nativeMesh.face( faceIndex );
        if ( !face.isEmpty() )
        {
          QgsDistanceArea *calc = parent->geomCalculator();
          QgsGeometry geom = QgsMeshUtils::toGeometry( nativeMesh.face( faceIndex ), nativeMesh.vertices );
          if ( calc )
          {
            try
            {
              double area = calc->measureArea( geom );
              area = calc->convertAreaMeasurement( area, parent->areaUnits() );
              return QVariant( area );
            }
            catch ( QgsCsException & )
            {
              parent->setEvalErrorString( QObject::tr( "An error occurred while calculating area" ) );
              return QVariant();
            }
          }
          else
          {
            return QVariant( geom.area() );
          }
        }
      }
 
      return QVariant();
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    }
};
 
class CurrentFaceIndexExpressionFunction: public QgsScopedExpressionFunction
{
  public:
    CurrentFaceIndexExpressionFunction():
      QgsScopedExpressionFunction( "$face_index",
                                   0,
                                   u"Meshes"_s )
    {}
 
    QgsScopedExpressionFunction *clone() const override {return new CurrentFaceIndexExpressionFunction();}
 
    QVariant func( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * ) override
    {
      if ( !context )
        return QVariant();
 
      if ( !context->hasVariable( u"_mesh_face_index"_s ) )
        return QVariant();
 
      return context->variable( u"_mesh_face_index"_s ).toInt();
 
    }
 
    bool isStatic( const QgsExpressionNodeFunction *, QgsExpression *, const QgsExpressionContext * ) const override
    {
      return false;
    }
};
 
 
 
QgsExpressionContextScope *QgsExpressionContextUtils::meshExpressionScope( QgsMesh::ElementType elementType )
{
  auto scope = std::make_unique<QgsExpressionContextScope>();
 
  switch ( elementType )
  {
    case QgsMesh::Vertex:
    {
      QgsExpression::registerFunction( new CurrentVertexExpressionFunction, true );
      QgsExpression::registerFunction( new CurrentVertexXValueExpressionFunction, true );
      QgsExpression::registerFunction( new CurrentVertexYValueExpressionFunction, true );
      QgsExpression::registerFunction( new CurrentVertexZValueExpressionFunction, true );
      QgsExpression::registerFunction( new CurrentVertexIndexExpressionFunction, true );
      scope->addFunction( "$vertex_as_point", new CurrentVertexExpressionFunction );
      scope->addFunction( "$vertex_x", new CurrentVertexXValueExpressionFunction );
      scope->addFunction( "$vertex_y", new CurrentVertexYValueExpressionFunction );
      scope->addFunction( "$vertex_z", new CurrentVertexZValueExpressionFunction );
      scope->addFunction( "$vertex_index", new CurrentVertexIndexExpressionFunction );
    }
    break;
    case QgsMesh::Face:
    {
      QgsExpression::registerFunction( new CurrentFaceAreaExpressionFunction, true );
      QgsExpression::registerFunction( new CurrentFaceIndexExpressionFunction, true );
      scope->addFunction( "$face_area", new CurrentFaceAreaExpressionFunction );
      scope->addFunction( "$face_index", new CurrentFaceIndexExpressionFunction );
    }
    break;
    case QgsMesh::Edge:
      break;
  }
 
  return scope.release();
}
 
 
QVariant LoadLayerFunction::func( const QVariantList &, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
  parent->setEvalErrorString( QObject::tr( "Invalid arguments for load_layer function" ) );
  return QVariant();
}
 
bool LoadLayerFunction::isStatic( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
  if ( node->args()->count() > 1 )
  {
    if ( !context )
      return false;
 
    QPointer< QgsMapLayerStore > store( context->loadedLayerStore() );
    if ( !store )
    {
      parent->setEvalErrorString( QObject::tr( "load_layer cannot be used in this context" ) );
      return false;
    }
 
    QgsExpressionNode *uriNode = node->args()->at( 0 );
    QgsExpressionNode *providerNode = node->args()->at( 1 );
    if ( !uriNode->isStatic( parent, context ) )
    {
      parent->setEvalErrorString( QObject::tr( "load_layer requires a static value for the uri argument" ) );
      return false;
    }
    if ( !providerNode->isStatic( parent, context ) )
    {
      parent->setEvalErrorString( QObject::tr( "load_layer requires a static value for the provider argument" ) );
      return false;
    }
 
    const QString uri = uriNode->eval( parent, context ).toString();
    if ( uri.isEmpty() )
    {
      parent->setEvalErrorString( QObject::tr( "Invalid uri argument for load_layer" ) );
      return false;
    }
 
    const QString providerKey = providerNode->eval( parent, context ).toString();
    if ( providerKey.isEmpty() )
    {
      parent->setEvalErrorString( QObject::tr( "Invalid provider argument for load_layer" ) );
      return false;
    }
 
    const QgsCoordinateTransformContext transformContext = context->variable( u"_project_transform_context"_s ).value<QgsCoordinateTransformContext>();
 
    bool res = false;
    auto loadLayer = [ uri, providerKey, store, node, parent, &res, &transformContext ]
    {
      QgsProviderMetadata *metadata = QgsProviderRegistry::instance()->providerMetadata( providerKey );
      if ( !metadata )
      {
        parent->setEvalErrorString( QObject::tr( "Invalid provider argument for load_layer" ) );
        return;
      }
 
      if ( metadata->supportedLayerTypes().empty() )
      {
        parent->setEvalErrorString( QObject::tr( "Cannot use %1 provider for load_layer" ).arg( providerKey ) );
        return;
      }
 
      QgsMapLayerFactory::LayerOptions layerOptions( transformContext );
      layerOptions.loadAllStoredStyles = false;
      layerOptions.loadDefaultStyle = false;
 
      QgsMapLayer *layer = QgsMapLayerFactory::createLayer( uri, uri, metadata->supportedLayerTypes().value( 0 ), layerOptions, providerKey );
      if ( !layer )
      {
        parent->setEvalErrorString( QObject::tr( "Could not load_layer with uri: %1" ).arg( uri ) );
        return;
      }
      if ( !layer->isValid() )
      {
        delete layer;
        parent->setEvalErrorString( QObject::tr( "Could not load_layer with uri: %1" ).arg( uri ) );
        return;
      }
 
      store->addMapLayer( layer );
 
      node->setCachedStaticValue( QVariant::fromValue( QgsWeakMapLayerPointer( layer ) ) );
      res = true;
    };
 
    // Make sure we load the layer on the thread where the store lives
    if ( QThread::currentThread() == store->thread() )
      loadLayer();
    else
      QMetaObject::invokeMethod( store, std::move( loadLayer ), Qt::BlockingQueuedConnection );
 
    return res;
  }
  return false;
}
 
QgsScopedExpressionFunction *LoadLayerFunction::clone() const
{
  return new LoadLayerFunction();
}