Move merge selected features logic to QgsVectorLayer

domi4484 · m-kuhn · commit 41b0477f15b5 · 2023-03-30T17:35:40.000+02:00
diff --git a/python/core/auto_generated/vector/qgsvectorlayer.sip.in b/python/core/auto_generated/vector/qgsvectorlayer.sip.in
@@ -2652,6 +2652,19 @@ Configuration and logic to apply automatically on any edit happening on this lay
 Returns the manager of the stored expressions for this layer.
 
 .. versionadded:: 3.10
+%End
+
+    bool mergeSelectedFeatures( const QgsAttributes &mergeAttributes, QgsGeometry unionGeometry, QString &errorMessage );
+%Docstring
+Merge selected features into a single one.
+
+:param mergeAttributes: are the resulting attributes in the merged feature
+:param unionGeometry: is the resulting geometry of the merged feature
+:param errorMessage: will be set to a descriptive error message if any occurs
+
+:return: ``True`` if the merge was successful, or ``False`` if the operation failed.
+
+.. versionadded:: 3.30
 %End
 
   public slots:
diff --git a/src/app/qgisapp.cpp b/src/app/qgisapp.cpp
@@ -9517,9 +9517,8 @@ void QgisApp::mergeSelectedFeatures()
     return;
   }
 
-  //get selected feature ids (as a QSet<int> )
-  const QgsFeatureIds &featureIdSet = vl->selectedFeatureIds();
-  if ( featureIdSet.size() < 2 )
+  // Check at least two features are selected
+  if ( vl->selectedFeatureIds().size() < 2 )
   {
     visibleMessageBar()->pushMessage(
       tr( "Not enough features selected" ),
@@ -9593,104 +9592,37 @@ void QgisApp::mergeSelectedFeatures()
       }
       return;
     }
-  }
-
-  QgsAttributes attrs = d.mergedAttributes();
-  QgsAttributeMap newAttributes;
-  QString errorMessage;
-  QgsFeatureId mergeFeatureId = FID_NULL;
-  for ( int i = 0; i < attrs.count(); ++i )
-  {
-    QVariant val = attrs.at( i );
-    bool isDefaultValue = vl->fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
-                          vl->dataProvider() &&
-                          vl->dataProvider()->defaultValueClause( vl->fields().fieldOriginIndex( i ) ) == val;
-    bool isPrimaryKey =  vl->fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
-                         vl->dataProvider() &&
-                         vl->dataProvider()->pkAttributeIndexes().contains( vl->fields().fieldOriginIndex( i ) );
-
-    if ( isPrimaryKey && !isDefaultValue )
-    {
-      QgsFeatureRequest request;
-      request.setFlags( QgsFeatureRequest::Flag::NoGeometry );
-      // Handle multi pks
-      if ( vl->dataProvider()->pkAttributeIndexes().count() > 1 && vl->dataProvider()->pkAttributeIndexes().count() <= attrs.count() )
-      {
-        const auto pkIdxList { vl->dataProvider()->pkAttributeIndexes() };
-        QStringList conditions;
-        QStringList fieldNames;
-        for ( const int &pkIdx : std::as_const( pkIdxList ) )
-        {
-          const QgsField pkField { vl->fields().field( pkIdx ) };
-          conditions.push_back( QgsExpression::createFieldEqualityExpression( pkField.name(), attrs.at( pkIdx ), pkField.type( ) ) );
-          fieldNames.push_back( pkField.name() );
-        }
-        request.setSubsetOfAttributes( fieldNames, vl->fields( ) );
-        request.setFilterExpression( conditions.join( QStringLiteral( " AND " ) ) );
-      }
-      else  // single pk
-      {
-        const QgsField pkField { vl->fields().field( i ) };
-        request.setSubsetOfAttributes( QStringList() << pkField.name(), vl->fields( ) );
-        request.setFilterExpression( QgsExpression::createFieldEqualityExpression( pkField.name(), val, pkField.type( ) ) );
-      }
-
-      QgsFeature f;
-      QgsFeatureIterator featureIterator = vl->getFeatures( request );
-      if ( featureIterator.nextFeature( f ) )
+    else if ( !QgsWkbTypes::isMultiType( vl->wkbType() ) )
+    {
+      const QgsGeometryCollection *c = qgsgeometry_cast<const QgsGeometryCollection *>( unionGeom.constGet() );
+      if ( ( c && c->partCount() > 1 ) || !unionGeom.convertToSingleType() )
       {
-        mergeFeatureId = f.id( );
+        visibleMessageBar()->pushMessage(
+          tr( "Merge failed" ),
+          tr( "Resulting geometry type (multipart) is incompatible with layer type (singlepart)." ),
+          Qgis::MessageLevel::Critical );
+        return;
       }
     }
-
-    // convert to destination data type
-    if ( !isDefaultValue && !vl->fields().at( i ).convertCompatible( val, &errorMessage ) )
-    {
-      visibleMessageBar()->pushMessage(
-        tr( "Invalid result" ),
-        tr( "Could not store value '%1' in field of type %2: %3" ).arg( attrs.at( i ).toString(), vl->fields().at( i ).typeName(), errorMessage ),
-        Qgis::MessageLevel::Warning );
-    }
-    newAttributes[ i ] = val;
-  }
-
-  vl->beginEditCommand( tr( "Merged features" ) );
-
-  QgsFeature mergeFeature;
-  if ( mergeFeatureId == FID_NULL )
-  {
-    // Create new feature
-    mergeFeature = QgsVectorLayerUtils::createFeature( vl, unionGeom, newAttributes );
-  }
-  else
-  {
-    // Merge into existing feature
-    featureIdsAfter.remove( mergeFeatureId );
-  }
-
-  // Delete other features
-  QgsFeatureIds::const_iterator feature_it = featureIdsAfter.constBegin();
-  for ( ; feature_it != featureIdsAfter.constEnd(); ++feature_it )
-  {
-    vl->deleteFeature( *feature_it );
   }
 
+  QString errorMessage;
+  bool success = vl->mergeSelectedFeatures( d.mergedAttributes(), unionGeom, errorMessage );
 
-  if ( mergeFeatureId == FID_NULL )
+  if ( !success )
   {
-    // Add the new feature
-    vl->addFeature( mergeFeature );
+    visibleMessageBar()->pushMessage(
+      tr( "Merge failed" ),
+      errorMessage,
+      Qgis::MessageLevel::Critical );
   }
-  else
+  else if ( success && !errorMessage.isEmpty() )
   {
-    // Modify merge feature
-    vl->changeGeometry( mergeFeatureId, unionGeom );
-    vl->changeAttributeValues( mergeFeatureId, newAttributes );
+    visibleMessageBar()->pushMessage(
+      tr( "Invalid result" ),
+      errorMessage,
+      Qgis::MessageLevel::Warning );
   }
-
-  vl->endEditCommand();
-
-  vl->triggerRepaint();
 }
 
 void QgisApp::vertexTool()
diff --git a/src/core/vector/qgsvectorlayer.cpp b/src/core/vector/qgsvectorlayer.cpp
@@ -5863,6 +5863,120 @@ void QgsVectorLayer::setAllowCommit( bool allowCommit )
   emit allowCommitChanged();
 }
 
+bool QgsVectorLayer::mergeSelectedFeatures( const QgsAttributes &mergeAttributes, QgsGeometry unionGeometry, QString &errorMessage )
+{
+  errorMessage.clear();
+
+  if ( selectedFeatureIds().size() < 2 )
+  {
+    errorMessage = tr( "Not enough features selected, the merge tool requires at least two selected features" );
+    return false;
+  }
+
+  QgsAttributeMap newAttributes;
+  QgsFeatureId mergeFeatureId = FID_NULL;
+  for ( int i = 0; i < mergeAttributes.count(); ++i )
+  {
+    QVariant val = mergeAttributes.at( i );
+
+    bool isDefaultValue = fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
+                          dataProvider() &&
+                          dataProvider()->defaultValueClause( fields().fieldOriginIndex( i ) ) == val;
+
+    // Check if features can merged into an existing one
+    if ( mergeFeatureId == FID_NULL )
+    {
+      bool isPrimaryKey =  fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
+                           dataProvider() &&
+                           dataProvider()->pkAttributeIndexes().contains( fields().fieldOriginIndex( i ) );
+
+      if ( isPrimaryKey && !isDefaultValue )
+      {
+        QgsFeatureRequest request;
+        request.setFlags( QgsFeatureRequest::Flag::NoGeometry );
+        // Handle multi pks
+        if ( dataProvider()->pkAttributeIndexes().count() > 1 && dataProvider()->pkAttributeIndexes().count() <= mergeAttributes.count() )
+        {
+          const auto pkIdxList { dataProvider()->pkAttributeIndexes() };
+          QStringList conditions;
+          QStringList fieldNames;
+          for ( const int &pkIdx : std::as_const( pkIdxList ) )
+          {
+            const QgsField pkField { fields().field( pkIdx ) };
+            conditions.push_back( QgsExpression::createFieldEqualityExpression( pkField.name(), mergeAttributes.at( pkIdx ), pkField.type( ) ) );
+            fieldNames.push_back( pkField.name() );
+          }
+          request.setSubsetOfAttributes( fieldNames, fields( ) );
+          request.setFilterExpression( conditions.join( QStringLiteral( " AND " ) ) );
+        }
+        else  // single pk
+        {
+          const QgsField pkField { fields().field( i ) };
+          request.setSubsetOfAttributes( QStringList() << pkField.name(), fields( ) );
+          request.setFilterExpression( QgsExpression::createFieldEqualityExpression( pkField.name(), val, pkField.type( ) ) );
+        }
+
+        QgsFeature f;
+        QgsFeatureIterator featureIterator = getFeatures( request );
+        if ( featureIterator.nextFeature( f ) )
+        {
+          mergeFeatureId = f.id( );
+        }
+      }
+    }
+
+    // convert to destination data type
+    QString errorMessageConvertCompatible;
+    if ( !isDefaultValue && !fields().at( i ).convertCompatible( val, &errorMessageConvertCompatible ) )
+    {
+      if ( errorMessage.isEmpty() )
+        errorMessage = tr( "Could not store value '%1' in field of type %2: %3" ).arg( mergeAttributes.at( i ).toString(), fields().at( i ).typeName(), errorMessageConvertCompatible );
+    }
+    newAttributes[ i ] = val;
+  }
+
+  beginEditCommand( tr( "Merged features" ) );
+
+  QgsFeatureIds featureIdsAfter = selectedFeatureIds();
+
+  QgsFeature mergeFeature;
+  if ( mergeFeatureId == FID_NULL )
+  {
+    // Create new feature
+    mergeFeature = QgsVectorLayerUtils::createFeature( this, unionGeometry, newAttributes );
+  }
+  else
+  {
+    // Merge into existing feature
+    featureIdsAfter.remove( mergeFeatureId );
+  }
+
+  // Delete other features
+  QgsFeatureIds::const_iterator feature_it = featureIdsAfter.constBegin();
+  for ( ; feature_it != featureIdsAfter.constEnd(); ++feature_it )
+  {
+    deleteFeature( *feature_it );
+  }
+
+  if ( mergeFeatureId == FID_NULL )
+  {
+    // Add the new feature
+    addFeature( mergeFeature );
+  }
+  else
+  {
+    // Modify merge feature
+    changeGeometry( mergeFeatureId, unionGeometry );
+    changeAttributeValues( mergeFeatureId, newAttributes );
+  }
+
+  endEditCommand();
+
+  triggerRepaint();
+
+  return true;
+}
+
 QgsGeometryOptions *QgsVectorLayer::geometryOptions() const
 {
   return mGeometryOptions.get();
diff --git a/src/core/vector/qgsvectorlayer.h b/src/core/vector/qgsvectorlayer.h
@@ -2480,6 +2480,18 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      */
     QgsStoredExpressionManager *storedExpressionManager() { return mStoredExpressionManager; }
 
+    /**
+     * Merge selected features into a single one.
+     * \param mergeAttributes are the resulting attributes in the merged feature
+     * \param unionGeometry is the resulting geometry of the merged feature
+     * \param errorMessage will be set to a descriptive error message if any occurs
+     *
+     * \returns TRUE if the merge was successful, or FALSE if the operation failed.
+     *
+     * \since QGIS 3.30
+     */
+    bool mergeSelectedFeatures( const QgsAttributes &mergeAttributes, QgsGeometry unionGeometry, QString &errorMessage );
+
   public slots:
 
     /**
