Explicitly set the target feature for merge operation

qgis · Mar 30, 2023 · 3ea1674 · 3ea1674
1 parent ae3573b
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Showing 9 changed files with 148 additions and 83 deletions.
diff --git a/python/core/auto_generated/vector/qgsvectorlayereditutils.sip.in b/python/core/auto_generated/vector/qgsvectorlayereditutils.sip.in
@@ -312,10 +312,11 @@ editing.
 .. versionadded:: 3.16
 %End
 
-    bool mergeFeatures( const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, QgsGeometry unionGeometry, QString &errorMessage /Out/ );
+    bool mergeFeatures( const QgsFeatureId &targetFeatureId, const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, const QgsGeometry &unionGeometry, QString &errorMessage /Out/ );
 %Docstring
 Merge features into a single one.
 
+:param targetFeatureId: id of the target feature
 :param mergeFeatureIds: id list of features to merge
 :param mergeAttributes: are the resulting attributes in the merged feature
 :param unionGeometry: is the resulting geometry of the merged feature

diff --git a/src/app/qgisapp.cpp b/src/app/qgisapp.cpp
@@ -9609,7 +9609,7 @@ void QgisApp::mergeSelectedFeatures()
 
   QString errorMessage;
   QgsVectorLayerEditUtils vectorLayerEditUtils( vl );
-  bool success = vectorLayerEditUtils.mergeFeatures( vl->selectedFeatureIds(), d.mergedAttributes(), unionGeom, errorMessage );
+  bool success = vectorLayerEditUtils.mergeFeatures( d.targetFeatureId(), vl->selectedFeatureIds(), d.mergedAttributes(), unionGeom, errorMessage );
 
   if ( !success )
   {

diff --git a/src/app/qgsmergeattributesdialog.cpp b/src/app/qgsmergeattributesdialog.cpp
@@ -108,6 +108,9 @@ QgsMergeAttributesDialog::QgsMergeAttributesDialog( const QgsFeatureList &featur
       break;
   }
 
+  if ( ! mFeatureList.isEmpty() )
+    mTargetFeatureId = mFeatureList.first().id();
+
   connect( mSkipAllButton, &QAbstractButton::clicked, this, &QgsMergeAttributesDialog::setAllToSkip );
   connect( mTableWidget, &QTableWidget::cellChanged, this, &QgsMergeAttributesDialog::tableWidgetCellChanged );
 
@@ -465,6 +468,8 @@ void QgsMergeAttributesDialog::setAllAttributesFromFeature( QgsFeatureId feature
       currentComboBox->setCurrentIndex( currentComboBox->findData( QStringLiteral( "f%1" ).arg( FID_TO_STRING( featureId ) ) ) );
     }
   }
+
+  mTargetFeatureId = featureId;
 }
 
 QVariant QgsMergeAttributesDialog::calcStatistic( int col, QgsStatisticalSummary::Statistic stat )
@@ -666,12 +671,18 @@ void QgsMergeAttributesDialog::mRemoveFeatureFromSelectionButton_clicked()
         f_it != mFeatureList.end();
         ++f_it )
   {
+    if ( f_it->id() == mTargetFeatureId )
+      mTargetFeatureId = FID_NULL;
+
     if ( f_it->id() == featureId )
     {
       mFeatureList.erase( f_it );
       break;
     }
   }
+
+  if ( mTargetFeatureId == FID_NULL && !mFeatureList.isEmpty() )
+    mTargetFeatureId = mFeatureList.first().id();
 }
 
 void QgsMergeAttributesDialog::tableWidgetCellChanged( int row, int column )
@@ -745,6 +756,11 @@ QgsAttributes QgsMergeAttributesDialog::mergedAttributes() const
   return results;
 }
 
+QgsFeatureId QgsMergeAttributesDialog::targetFeatureId() const
+{
+  return mTargetFeatureId;
+}
+
 QSet<int> QgsMergeAttributesDialog::skippedAttributeIndexes() const
 {
   QSet<int> skipped;

diff --git a/src/app/qgsmergeattributesdialog.h b/src/app/qgsmergeattributesdialog.h
@@ -49,6 +49,18 @@ class APP_EXPORT QgsMergeAttributesDialog: public QDialog, private Ui::QgsMergeA
 
     QgsAttributes mergedAttributes() const;
 
+    /**
+     * Returns the id of the target feature.
+     * By default it is the first feature of the list. Otherwise the feature explicitly selected
+     * with buttons "Take attributes from selected feature" or "Take attributes from feature with
+     * the largest area".
+     *
+     * \returns The id of the target feature.
+     *
+     * \since QGIS 3.30
+     */
+    QgsFeatureId targetFeatureId() const;
+
     /**
      * Returns a list of attribute indexes which should be skipped when merging (e.g., attributes
      * which have been set to "skip"
@@ -102,6 +114,7 @@ class APP_EXPORT QgsMergeAttributesDialog: public QDialog, private Ui::QgsMergeA
     void createRubberBandForFeature( QgsFeatureId featureId );
 
     QgsFeatureList mFeatureList;
+    QgsFeatureId mTargetFeatureId = FID_NULL;
     QgsVectorLayer *mVectorLayer = nullptr;
     QgsMapCanvas *mMapCanvas = nullptr;
     //! Item that highlights the selected feature in the merge table

diff --git a/src/core/vector/qgsvectorlayereditutils.cpp b/src/core/vector/qgsvectorlayereditutils.cpp
@@ -721,18 +721,17 @@ int QgsVectorLayerEditUtils::addTopologicalPoints( const QgsPointXY &p )
   return addTopologicalPoints( QgsPoint( p ) );
 }
 
-bool QgsVectorLayerEditUtils::mergeFeatures( const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, QgsGeometry unionGeometry, QString &errorMessage )
+bool QgsVectorLayerEditUtils::mergeFeatures( const QgsFeatureId &targetFeatureId, const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, const QgsGeometry &unionGeometry, QString &errorMessage )
 {
   errorMessage.clear();
 
-  if ( mergeFeatureIds.size() < 2 )
+  if ( mergeFeatureIds.isEmpty() )
   {
-    errorMessage = QObject::tr( "Not enough features to merge, the merge tool requires at least two features" );
+    errorMessage = QObject::tr( "List of features to merge is empty" );
     return false;
   }
 
   QgsAttributeMap newAttributes;
-  QgsFeatureId mergeFeatureId = FID_NULL;
   for ( int i = 0; i < mergeAttributes.count(); ++i )
   {
     QVariant val = mergeAttributes.at( i );
@@ -741,48 +740,6 @@ bool QgsVectorLayerEditUtils::mergeFeatures( const QgsFeatureIds &mergeFeatureId
                           mLayer->dataProvider() &&
                           mLayer->dataProvider()->defaultValueClause( mLayer->fields().fieldOriginIndex( i ) ) == val;
 
-    // Check if features can merged into an existing one
-    if ( mergeFeatureId == FID_NULL )
-    {
-      bool isPrimaryKey =  mLayer->fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
-                           mLayer->dataProvider() &&
-                           mLayer->dataProvider()->pkAttributeIndexes().contains( mLayer->fields().fieldOriginIndex( i ) );
-
-      if ( isPrimaryKey && !isDefaultValue )
-      {
-        QgsFeatureRequest request;
-        request.setFlags( QgsFeatureRequest::Flag::NoGeometry );
-        // Handle multi pks
-        if ( mLayer->dataProvider()->pkAttributeIndexes().count() > 1 && mLayer->dataProvider()->pkAttributeIndexes().count() <= mergeAttributes.count() )
-        {
-          const auto pkIdxList { mLayer->dataProvider()->pkAttributeIndexes() };
-          QStringList conditions;
-          QStringList fieldNames;
-          for ( const int &pkIdx : std::as_const( pkIdxList ) )
-          {
-            const QgsField pkField { mLayer->fields().field( pkIdx ) };
-            conditions.push_back( QgsExpression::createFieldEqualityExpression( pkField.name(), mergeAttributes.at( pkIdx ), pkField.type( ) ) );
-            fieldNames.push_back( pkField.name() );
-          }
-          request.setSubsetOfAttributes( fieldNames, mLayer->fields( ) );
-          request.setFilterExpression( conditions.join( QLatin1String( " AND " ) ) );
-        }
-        else  // single pk
-        {
-          const QgsField pkField { mLayer->fields().field( i ) };
-          request.setSubsetOfAttributes( QStringList() << pkField.name(), mLayer->fields( ) );
-          request.setFilterExpression( QgsExpression::createFieldEqualityExpression( pkField.name(), val, pkField.type( ) ) );
-        }
-
-        QgsFeature f;
-        QgsFeatureIterator featureIterator = mLayer->getFeatures( request );
-        if ( featureIterator.nextFeature( f ) )
-        {
-          mergeFeatureId = f.id( );
-        }
-      }
-    }
-
     // convert to destination data type
     QString errorMessageConvertCompatible;
     if ( !isDefaultValue && !mLayer->fields().at( i ).convertCompatible( val, &errorMessageConvertCompatible ) )
@@ -795,38 +752,18 @@ bool QgsVectorLayerEditUtils::mergeFeatures( const QgsFeatureIds &mergeFeatureId
 
   mLayer->beginEditCommand( QObject::tr( "Merged features" ) );
 
-  QgsFeatureIds featureIdsToDelete = mergeFeatureIds;
-
-  QgsFeature mergeFeature;
-  if ( mergeFeatureId == FID_NULL )
-  {
-    // Create new feature
-    mergeFeature = QgsVectorLayerUtils::createFeature( mLayer, unionGeometry, newAttributes );
-  }
-  else
-  {
-    // Merge into existing feature
-    featureIdsToDelete.remove( mergeFeatureId );
-  }
-
-  // Delete other features
-  QgsFeatureIds::const_iterator feature_it = featureIdsToDelete.constBegin();
-  for ( ; feature_it != featureIdsToDelete.constEnd(); ++feature_it )
+  // Delete other features but the target feature
+  QgsFeatureIds::const_iterator feature_it = mergeFeatureIds.constBegin();
+  for ( ; feature_it != mergeFeatureIds.constEnd(); ++feature_it )
   {
-    mLayer->deleteFeature( *feature_it );
+    if ( *feature_it != targetFeatureId )
+      mLayer->deleteFeature( *feature_it );
   }
 
-  if ( mergeFeatureId == FID_NULL )
-  {
-    // Add the new feature
-    mLayer->addFeature( mergeFeature );
-  }
-  else
-  {
-    // Modify merge feature
-    mLayer->changeGeometry( mergeFeatureId, unionGeometry );
-    mLayer->changeAttributeValues( mergeFeatureId, newAttributes );
-  }
+  // Modify merge feature
+  QgsGeometry mergeGeometry = unionGeometry;
+  mLayer->changeGeometry( targetFeatureId, mergeGeometry );
+  mLayer->changeAttributeValues( targetFeatureId, newAttributes );
 
   mLayer->endEditCommand();
 

diff --git a/src/core/vector/qgsvectorlayereditutils.h b/src/core/vector/qgsvectorlayereditutils.h
@@ -270,6 +270,7 @@ class CORE_EXPORT QgsVectorLayerEditUtils
 
     /**
      * Merge features into a single one.
+     * \param targetFeatureId id of the target feature
      * \param mergeFeatureIds id list of features to merge
      * \param mergeAttributes are the resulting attributes in the merged feature
      * \param unionGeometry is the resulting geometry of the merged feature
@@ -279,7 +280,7 @@ class CORE_EXPORT QgsVectorLayerEditUtils
      *
      * \since QGIS 3.30
      */
-    bool mergeFeatures( const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, QgsGeometry unionGeometry, QString &errorMessage SIP_OUT );
+    bool mergeFeatures( const QgsFeatureId &targetFeatureId, const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, const QgsGeometry &unionGeometry, QString &errorMessage SIP_OUT );
 
   private:
 

diff --git a/tests/src/app/CMakeLists.txt b/tests/src/app/CMakeLists.txt
@@ -46,6 +46,7 @@ set(TESTS
   testqgsmeshcalculatordialog.cpp
   testqgsgpsinformationwidget.cpp
   testqgslabelpropertydialog.cpp
+  testqgsmergeattributesdialog.cpp
 )
 
 if (HAVE_GEOREFERENCER)

diff --git a/tests/src/app/testqgsmergeattributesdialog.cpp b/tests/src/app/testqgsmergeattributesdialog.cpp
@@ -0,0 +1,97 @@
+/***************************************************************************
+     testqgsmergeattributesdialog.cpp
+     --------------------------------
+    Date                 : Feb 2023
+    Copyright            : (C) 2023 by Damiano Lombardi
+    Email                : damiano 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 "qgstest.h"
+#include <QObject>
+
+#include "qgisapp.h"
+#include "qgsapplication.h"
+#include "qgsvectorlayer.h"
+#include "qgsmergeattributesdialog.h"
+
+class TestQgsMergeattributesDialog : public QObject
+{
+    Q_OBJECT
+
+  public:
+    TestQgsMergeattributesDialog() = default;
+
+  private:
+    QgisApp *mQgisApp = nullptr;
+
+  private slots:
+
+    void initTestCase()
+    {
+      QgsApplication::init();
+      QgsApplication::initQgis();
+      mQgisApp = new QgisApp();
+    }
+
+    void cleanupTestCase()
+    {
+      QgsApplication::exitQgis();
+    }
+
+    void test()
+    {
+      // Create test layer
+      QgsVectorFileWriter::SaveVectorOptions options;
+      QgsVectorLayer ml( "Polygon", "test", "memory" );
+      QVERIFY( ml.isValid() );
+      QTemporaryFile tmpFile( QDir::tempPath() +  "/TestQgsMergeattributesDialog" );
+      tmpFile.open();
+      const QString fileName( tmpFile.fileName( ) );
+      options.driverName = "GPKG";
+      options.layerName = "test";
+      QString newFilename;
+      const QgsVectorFileWriter::WriterError error( QgsVectorFileWriter::writeAsVectorFormatV3(
+            &ml,
+            fileName,
+            ml.transformContext(),
+            options, nullptr,
+            &newFilename ) );
+
+      QCOMPARE( error, QgsVectorFileWriter::WriterError::NoError );
+      QgsVectorLayer layer( QStringLiteral( "%1|layername=test" ).arg( newFilename ), "src_test", "ogr" );
+      QVERIFY( layer.startEditing() );
+      QgsVectorDataProvider *pr = layer.dataProvider();
+
+      // Create a feature
+      QgsFeature f1( layer.fields(), 1 );
+      f1.setGeometry( QgsGeometry::fromWkt( "POLYGON((0 0, 5 0, 5 5, 0 5, 0 0))" ) );
+      QVERIFY( pr->addFeature( f1 ) );
+      QCOMPARE( layer.featureCount(), 1 );
+
+      // And a bigger feature
+      QgsFeature f2( layer.fields(), 2 );
+      f2.setGeometry( QgsGeometry::fromWkt( "POLYGON((3 3, 10 3, 10 10, 3 10, 3 3))" ) );
+      QVERIFY( pr->addFeature( f2 ) );
+      QCOMPARE( layer.featureCount(), 2 );
+
+      // Merge the attributes together
+      QgsMergeAttributesDialog dialog( QgsFeatureList() << f1 << f2, &layer, mQgisApp->mapCanvas() );
+
+      // At beginnning the first feature of the list is the target
+      QCOMPARE( dialog.targetFeatureId(), f1.id() );
+
+      // Check after taking feature with largest geometry
+      QVERIFY( QMetaObject::invokeMethod( &dialog, "mFromLargestPushButton_clicked" ) );
+      QCOMPARE( dialog.targetFeatureId(), f2.id() );
+    }
+};
+
+QGSTEST_MAIN( TestQgsMergeattributesDialog )
+#include "testqgsmergeattributesdialog.moc"
diff --git a/tests/src/python/test_qgsvectorlayereditutils.py b/tests/src/python/test_qgsvectorlayereditutils.py
@@ -494,13 +494,13 @@ def testMergeFeatures(self):
         self.assertTrue(layer.startEditing())
         layer.addAttribute(QgsField('name', QVariant.String))
         pr = layer.dataProvider()
+
         f1 = QgsFeature(layer.fields(), 1)
         f1.setGeometry(QgsGeometry.fromWkt('POLYGON((0 0, 5 0, 5 5, 0 5, 0 0))'))
         f1.setAttribute('name', 'uno')
         assert pr.addFeatures([f1])
         self.assertEqual(layer.featureCount(), 1)
 
-        pr = layer.dataProvider()
         f2 = QgsFeature(layer.fields(), 2)
         f2.setGeometry(QgsGeometry.fromWkt('POLYGON((3 3, 8 3, 8 8, 3 8, 3 3))'))
         f2.setAttribute('name', 'due')
@@ -514,7 +514,7 @@ def testMergeFeatures(self):
         self.assertFalse(unionGeom.isNull())
 
         vle = QgsVectorLayerEditUtils(layer)
-        success, errorMessage = vle.mergeFeatures(featureIds, ['tre'], unionGeom)
+        success, errorMessage = vle.mergeFeatures(f1.id(), featureIds, ['tre'], unionGeom)
         self.assertFalse(errorMessage)
         self.assertTrue(success)
 
@@ -545,16 +545,15 @@ def testMergeFeaturesIntoExisting(self):
             options=options)
 
         layer = QgsVectorLayer(tempgpkg, 'my_layer', 'ogr')
-
         self.assertTrue(layer.startEditing())
         pr = layer.dataProvider()
+
         f1 = QgsFeature(layer.fields(), 1)
         f1.setGeometry(QgsGeometry.fromWkt('POLYGON((0 0, 5 0, 5 5, 0 5, 0 0))'))
         f1.setAttribute('name', 'uno')
         assert pr.addFeatures([f1])
         self.assertEqual(layer.featureCount(), 1)
 
-        pr = layer.dataProvider()
         f2 = QgsFeature(layer.fields(), 2)
         f2.setGeometry(QgsGeometry.fromWkt('POLYGON((3 3, 8 3, 8 8, 3 8, 3 3))'))
         f2.setAttribute('name', 'due')
@@ -568,7 +567,7 @@ def testMergeFeaturesIntoExisting(self):
         self.assertFalse(unionGeom.isNull())
 
         vle = QgsVectorLayerEditUtils(layer)
-        success, errorMessage = vle.mergeFeatures(featureIds, [2, 'tre'], unionGeom)
+        success, errorMessage = vle.mergeFeatures(f2.id(), featureIds, [2, 'tre'], unionGeom)
         self.assertFalse(errorMessage)
         self.assertTrue(success)