Introduce a FeaturesProxyModel to conditionally sort features list an…

…d value relations (#3543)

* Introduce a FeaturesProxyModel to conditionally sort features list and value relations

MMFeaturesListPage is sorted according to the layer's QgsAttributeTableConfig
MMFormValueRelationEditor is sorted by value when the widget has the OrderByValue config set

* Address review comments

* Invalidate proxy model when disabling sorting
Remove unused private variables
Don't try to disconnect the first time model is set

* Add tests

* do initialization bits once

* call setupSorting() on the model only once

app/CMakeLists.txt

@@ -52,6 +52,7 @@ set(MM_SRCS
     compass.cpp
     featurelayerpair.cpp
     featuresmodel.cpp
+    featuresproxymodel.cpp
     fieldsmodel.cpp
     guidelinecontroller.cpp
     identifykit.cpp
@@ -135,6 +136,7 @@ set(MM_HDRS
     enumhelper.h
     featurelayerpair.h
     featuresmodel.h
+    featuresproxymodel.h
     fieldsmodel.h
     guidelinecontroller.h
     identifykit.h

app/featuresmodel.cpp

@@ -141,6 +141,7 @@ QVariant FeaturesModel::data( const QModelIndex &index, int role ) const
     case LayerName: return pair.layer() ? pair.layer()->name() : QString();
     case LayerIcon: return pair.layer() ? InputUtils::loadIconFromLayer( pair.layer() ) : QString();
     case Qt::DisplayRole: return featureTitle( pair );
+    case SortValue: return sortValue( pair );
   }
 
   return QVariant();
@@ -177,6 +178,15 @@ QVariant FeaturesModel::featureTitle( const FeatureLayerPair &featurePair ) cons
   return title;
 }
 
+QVariant FeaturesModel::sortValue( const FeatureLayerPair &featurePair ) const
+{
+  QgsExpressionContext context( QgsExpressionContextUtils::globalProjectLayerScopes( featurePair.layer() ) );
+  context.setFeature( featurePair.feature() );
+  QgsExpression expr( mSortExpression );
+  QVariant result = expr.evaluate( &context );
+  return result;
+}
+
 QString FeaturesModel::searchResultPair( const FeatureLayerPair &pair ) const
 {
   if ( mSearchExpression.isEmpty() )
@@ -280,6 +290,7 @@ QHash<int, QByteArray> FeaturesModel::roleNames() const
   roleNames[SearchResult] = QStringLiteral( "SearchResult" ).toLatin1();
   roleNames[LayerName] = QStringLiteral( "LayerName" ).toLatin1();
   roleNames[LayerIcon] = QStringLiteral( "LayerIcon" ).toLatin1();
+  roleNames[SortValue] = QStringLiteral( "SortValue" ).toLatin1();
   return roleNames;
 }
 
@@ -372,3 +383,19 @@ QgsVectorLayer *FeaturesModel::layer() const
 {
   return mLayer;
 }
+
+void FeaturesModel::setupSorting()
+{
+  mSortExpression = mLayer ? mLayer->attributeTableConfig().sortExpression() : QString();
+  mSortOrder = mLayer ? mLayer->attributeTableConfig().sortOrder() : Qt::AscendingOrder;
+}
+
+bool FeaturesModel::sortingEnabled() const
+{
+  return !mSortExpression.isEmpty();
+}
+
+Qt::SortOrder FeaturesModel::sortOrder() const
+{
+  return mSortOrder;
+}

app/featuresmodel.h

@@ -64,6 +64,7 @@ class FeaturesModel : public QAbstractListModel
       SearchResult, // pair of attribute and its value by which the feature was found, empty if search expression is empty
       LayerName,
       LayerIcon,
+      SortValue,
     };
     Q_ENUM( ModelRoles );
 
@@ -117,6 +118,15 @@ class FeaturesModel : public QAbstractListModel
 
     int layerFeaturesCount() const;
 
+    //! Populates the sort expression and sort order for the model
+    virtual void setupSorting();
+
+    //! Returns true if there is a sort expression set for the model
+    bool sortingEnabled() const;
+
+    //! Returns the order in witch the model should be sorted
+    Qt::SortOrder sortOrder() const;
+
   signals:
 
     void featuresLimitChanged( int featuresLimit );
@@ -139,6 +149,9 @@ class FeaturesModel : public QAbstractListModel
 
     virtual QVariant featureTitle( const FeatureLayerPair &featurePair ) const;
 
+    QString mSortExpression;
+    Qt::SortOrder mSortOrder = Qt::AscendingOrder;
+
   private slots:
     void onFutureFinished();
 
@@ -151,6 +164,9 @@ class FeaturesModel : public QAbstractListModel
     //! Returns found attribute and its value from search expression for feature
     QString searchResultPair( const FeatureLayerPair &feat ) const;
 
+    //! Evaluates the sort expression and returns the value used for this feature when sorting the model
+    QVariant sortValue( const FeatureLayerPair &featurePair ) const;
+
     const int FEATURES_LIMIT = 10000; //!< Number of maximum features loaded from layer
 
     FeatureLayerPairs mFeatures;

app/featuresproxymodel.cpp

@@ -0,0 +1,48 @@
+/***************************************************************************
+ *                                                                         *
+ *   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 "featuresproxymodel.h"
+
+FeaturesProxyModel::FeaturesProxyModel( QObject *parent ) : QSortFilterProxyModel( parent )
+{
+  setSortRole( FeaturesModel::SortValue );
+  setSortCaseSensitivity( Qt::CaseInsensitive );
+}
+
+void FeaturesProxyModel::updateSorting()
+{
+  // don't sort if there is no sort expression for the layer
+  if ( mModel->sortingEnabled() )
+  {
+    sort( 0, mModel->sortOrder() );
+  }
+  else
+  {
+    invalidate();
+  }
+}
+
+FeaturesModel *FeaturesProxyModel::featuresSourceModel() const
+{
+  return mModel;
+}
+
+void FeaturesProxyModel::setFeaturesSourceModel( FeaturesModel *sourceModel )
+{
+  if ( mModel == sourceModel )
+    return;
+
+  if ( mModel )
+    disconnect( mModel, nullptr, this, nullptr );
+
+  mModel = sourceModel;
+  setSourceModel( mModel );
+  mModel->setupSorting();
+  connect( mModel, &FeaturesModel::fetchingResultsChanged, this, [ = ]( bool pending ) { if ( !pending ) updateSorting(); } );
+}

app/featuresproxymodel.h

@@ -0,0 +1,47 @@
+/***************************************************************************
+ *                                                                         *
+ *   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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef FEATURESPROXYMODEL_H
+#define FEATURESPROXYMODEL_H
+
+#include <QObject>
+#include <QSortFilterProxyModel>
+
+#include "featuresmodel.h"
+
+/**
+ * \brief The FeaturesProxyModel class used as a proxy sort model for the \see FeaturesModel class.
+ *
+ * FeaturesProxyModel is a QML type with required property of FeatureSourceModel. Without source model, this model does nothing (is not initialized).
+ * After setting source model, this model starts sorting if sortingEnabled() returns true for the source model.
+ */
+class FeaturesProxyModel : public QSortFilterProxyModel
+{
+    Q_OBJECT
+
+    Q_PROPERTY( FeaturesModel *featuresSourceModel READ featuresSourceModel WRITE setFeaturesSourceModel )
+
+  public:
+    explicit FeaturesProxyModel( QObject *parent = nullptr );
+    ~FeaturesProxyModel() override {};
+
+    FeaturesModel *featuresSourceModel() const;
+
+  public slots:
+    void setFeaturesSourceModel( FeaturesModel *sourceModel );
+
+  private:
+    void updateSorting();
+
+    FeaturesModel *mModel = nullptr; // not owned by this, needs to be set in order to proxy model to work
+
+    friend class TestModels;
+};
+
+#endif // FEATURESPROXYMODEL_H

app/main.cpp

@@ -91,6 +91,7 @@
 #include "position/positionkit.h"
 #include "scalebarkit.h"
 #include "featuresmodel.h"
+#include "featuresproxymodel.h"
 #include "relationfeaturesmodel.h"
 #include "relationreferencefeaturesmodel.h"
 #include "fieldvalidator.h"
@@ -326,6 +327,7 @@ void initDeclarative()
   qmlRegisterType< MapThemesModel >( "mm", 1, 0, "MapThemesModel" );
   qmlRegisterType< GuidelineController >( "mm", 1, 0, "GuidelineController" );
   qmlRegisterType< FeaturesModel >( "mm", 1, 0, "FeaturesModel" );
+  qmlRegisterType< FeaturesProxyModel >( "mm", 1, 0, "FeaturesProxyModel" );
   qmlRegisterType< RelationFeaturesModel >( "mm", 1, 0, "RelationFeaturesModel" );
   qmlRegisterType< ValueRelationFeaturesModel >( "mm", 1, 0, "ValueRelationFeaturesModel" );
   qmlRegisterType< RelationReferenceFeaturesModel >( "mm", 1, 0, "RelationReferenceFeaturesModel" );

app/qml/form/editors/MMFormValueRelationEditor.qml

@@ -76,11 +76,15 @@ MMFormComboboxBaseEditor {
       valueRole: "FeatureId"
       textRole: "FeatureTitle"
 
-      list.model: MM.ValueRelationFeaturesModel {
-        id: vrDropdownModel
+      list.model: MM.FeaturesProxyModel {
+        id: vrDropdownProxyModel
 
-        config: root._fieldConfig
-        pair: root._fieldFeatureLayerPair
+        featuresSourceModel: MM.ValueRelationFeaturesModel {
+          id: vrDropdownModel
+
+          config: root._fieldConfig
+          pair: root._fieldFeatureLayerPair
+        }
       }
 
       onSearchTextChanged: ( searchText ) => vrDropdownModel.searchExpression = searchText

app/qml/layers/MMFeaturesListPage.qml

@@ -55,10 +55,14 @@ MMComponents.MMPage {
         topMargin: __style.spacing20
       }
 
-      model: MM.FeaturesModel {
-        id: featuresModel
+      model: MM.FeaturesProxyModel {
+        id: featuresProxyModel
 
-        layer: root.selectedLayer
+        featuresSourceModel: MM.FeaturesModel {
+          id: featuresModel
+
+          layer: root.selectedLayer
+        }
       }
 
       clip: true