port Define Projection algorithm to C++

python/plugins/processing/algs/help/qgis.yaml

@@ -33,11 +33,6 @@ qgis:convertgeometrytype: >
 
   See the "Polygonize" or "Lines to polygons" algorithm for alternative options.
 
-qgis:definecurrentprojection: >
-  This algorithm sets an existing Shapefile's projection to the provided CRS. Contrary to the "Assign projection" algorithm, it will not output a new layer.
-
-  The .prj and .qpj files associated with the Shapefile will be overwritten - or created if missing - to match the provided CRS.
-
 qgis:distancematrix: >
   This algorithm creates a table containing a distance matrix, with distances between all the points in a points layer.
 

python/plugins/processing/algs/qgis/QgisAlgorithmProvider.py

@@ -29,7 +29,6 @@
 from .BoxPlot import BoxPlot
 from .CheckValidity import CheckValidity
 from .Climb import Climb
-from .DefineProjection import DefineProjection
 from .EliminateSelection import EliminateSelection
 from .ExecuteSQL import ExecuteSQL
 from .ExportGeometryInfo import ExportGeometryInfo
@@ -94,7 +93,6 @@ def getAlgs(self):
             BoxPlot(),
             CheckValidity(),
             Climb(),
-            DefineProjection(),
             EliminateSelection(),
             ExecuteSQL(),
             ExportGeometryInfo(),

src/analysis/CMakeLists.txt

@@ -80,6 +80,7 @@ set(QGIS_ANALYSIS_SRCS
   processing/qgsalgorithmcoveragevalidate.cpp
   processing/qgsalgorithmcreatedirectory.cpp
   processing/qgsalgorithmdbscanclustering.cpp
+  processing/qgsalgorithmdefineprojection.cpp
   processing/qgsalgorithmdelaunaytriangulation.cpp
   processing/qgsalgorithmdeleteduplicategeometries.cpp
   processing/qgsalgorithmdensifygeometriesbycount.cpp

src/analysis/processing/qgsalgorithmdefineprojection.cpp

@@ -0,0 +1,137 @@
+/***************************************************************************
+                         qgsalgorithmdefineprojection.cpp
+                         ---------------------
+    begin                : February 2025
+    copyright            : (C) 2025 by Alexander Bruy
+    email                : alexander dot bruy 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 "qgsalgorithmdefineprojection.h"
+#include "qgsvectorlayer.h"
+#include "qgsproviderregistry.h"
+
+///@cond PRIVATE
+
+QString QgsDefineProjectionAlgorithm::name() const
+{
+  return QStringLiteral( "definecurrentprojection" );
+}
+
+QString QgsDefineProjectionAlgorithm::displayName() const
+{
+  return QObject::tr( "Define projection" );
+}
+
+QStringList QgsDefineProjectionAlgorithm::tags() const
+{
+  return QObject::tr( "layer,shp,prj,qpj,change,alter" ).split( ',' );
+}
+
+QString QgsDefineProjectionAlgorithm::group() const
+{
+  return QObject::tr( "Vector general" );
+}
+
+QString QgsDefineProjectionAlgorithm::groupId() const
+{
+  return QStringLiteral( "vectorgeneral" );
+}
+
+QString QgsDefineProjectionAlgorithm::shortHelpString() const
+{
+  return QObject::tr( "Sets an existing layer's projection to the provided CRS without reprojecting features. "
+                      "Contrary to the \"Assign projection\" algorithm, it will not output a new layer.\n\n"
+                      "If the input layer is a shapefile, the .prj file will be overwritten — or created if "
+                      "missing — to match the provided CRS." );
+}
+
+QgsDefineProjectionAlgorithm *QgsDefineProjectionAlgorithm::createInstance() const
+{
+  return new QgsDefineProjectionAlgorithm();
+}
+
+void QgsDefineProjectionAlgorithm::initAlgorithm( const QVariantMap & )
+{
+  addParameter( new QgsProcessingParameterVectorLayer( QStringLiteral( "INPUT" ), QObject::tr( "Input shapefile" ), QList<int>() << static_cast<int>( Qgis::ProcessingSourceType::VectorAnyGeometry ) ) );
+  addParameter( new QgsProcessingParameterCrs( QStringLiteral( "CRS" ), QObject::tr( "CRS" ), QgsCoordinateReferenceSystem( "EPSG:4326" ) ) );
+  addOutput( new QgsProcessingOutputVectorLayer( QStringLiteral( "OUTPUT" ), QObject::tr( "Layer with projection" ) ) );
+}
+
+bool QgsDefineProjectionAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
+{
+  QgsVectorLayer *layer = parameterAsVectorLayer( parameters, QStringLiteral( "INPUT" ), context );
+  const QgsCoordinateReferenceSystem crs = parameterAsCrs( parameters, QStringLiteral( "CRS" ), context );
+
+  if ( !layer )
+    throw QgsProcessingException( QObject::tr( "Invalid input layer" ) );
+
+  mLayerId = layer->id();
+
+  if ( layer->providerType().compare( QStringLiteral( "ogr" ), Qt::CaseSensitivity::CaseInsensitive ) == 0 )
+  {
+    const QVariantMap parts = QgsProviderRegistry::instance()->decodeUri( layer->providerType(), layer->dataProvider()->dataSourceUri() );
+    QString layerPath;
+    if ( parts.size() > 0 )
+    {
+      layerPath = parts.value( QStringLiteral( "path" ) ).toString();
+    }
+
+    if ( !layerPath.isEmpty() && layerPath.endsWith( QStringLiteral( ".shp" ), Qt::CaseSensitivity::CaseInsensitive ) )
+    {
+      const QString filePath = layerPath.chopped( 4 );
+      const QString wkt = crs.toWkt( Qgis::CrsWktVariant::Wkt1Esri );
+
+      QFile prjFile( filePath + QLatin1String( ".prj" ) );
+      if ( prjFile.open( QIODevice::WriteOnly | QIODevice::Truncate ) )
+      {
+        QTextStream stream( &prjFile );
+        stream << wkt << Qt::endl;
+      }
+      else
+      {
+        feedback->pushWarning( QObject::tr( "Failed to open .prj file for writing." ) );
+      }
+
+      QFile qpjFile( filePath + QLatin1String( ".qpj" ) );
+      if ( qpjFile.exists() )
+      {
+        qpjFile.remove();
+      }
+    }
+    else
+    {
+      feedback->pushWarning( QObject::tr( "Data source isn't a shapefile, skipping .prj creation" ) );
+    }
+  }
+  else
+  {
+    feedback->pushInfo( QObject::tr( "Data source isn't a shapefile, skipping .prj creation" ) );
+  }
+
+  layer->setCrs( crs );
+  layer->triggerRepaint();
+
+  return true;
+}
+
+QVariantMap QgsDefineProjectionAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
+{
+  Q_UNUSED( parameters );
+  Q_UNUSED( context );
+  Q_UNUSED( feedback );
+
+  QVariantMap results;
+  results.insert( QStringLiteral( "OUTPUT" ), mLayerId );
+  return results;
+}
+
+///@endcond

src/analysis/processing/qgsalgorithmdefineprojection.h

@@ -0,0 +1,54 @@
+/***************************************************************************
+                         qgsalgorithmdefineprojection.h
+                         ---------------------
+    begin                : February 2025
+    copyright            : (C) 2025 by Alexander Bruy
+    email                : alexander dot bruy 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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSALGORITHMDEFINEPROJECTION_H
+#define QGSALGORITHMDEFINEPROJECTION_H
+
+#define SIP_NO_FILE
+
+#include "qgis_sip.h"
+#include "qgsprocessingalgorithm.h"
+
+///@cond PRIVATE
+
+/**
+ * Native define layer projection algorithm.
+ */
+class QgsDefineProjectionAlgorithm : public QgsProcessingAlgorithm
+{
+  public:
+    QgsDefineProjectionAlgorithm() = default;
+    void initAlgorithm( const QVariantMap &configuration = QVariantMap() ) override;
+    QString name() const override;
+    QString displayName() const override;
+    QStringList tags() const override;
+    QString group() const override;
+    QString groupId() const override;
+    QString shortHelpString() const override;
+    QgsDefineProjectionAlgorithm *createInstance() const override SIP_FACTORY;
+
+  protected:
+    bool prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) override;
+    QVariantMap processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) override;
+
+  private:
+    QString mLayerId;
+};
+
+///@endcond PRIVATE
+
+#endif // QGSALGORITHMDEFINEPROJECTION_H

src/analysis/processing/qgsnativealgorithms.cpp

@@ -61,6 +61,7 @@
 #include "qgsalgorithmcoveragevalidate.h"
 #include "qgsalgorithmcreatedirectory.h"
 #include "qgsalgorithmdbscanclustering.h"
+#include "qgsalgorithmdefineprojection.h"
 #include "qgsalgorithmdelaunaytriangulation.h"
 #include "qgsalgorithmdeleteduplicategeometries.h"
 #include "qgsalgorithmdensifygeometriesbycount.h"
@@ -350,6 +351,7 @@ void QgsNativeAlgorithms::loadAlgorithms()
   addAlgorithm( new QgsCoverageValidateAlgorithm() );
   addAlgorithm( new QgsCreateDirectoryAlgorithm() );
   addAlgorithm( new QgsDbscanClusteringAlgorithm() );
+  addAlgorithm( new QgsDefineProjectionAlgorithm() );
   addAlgorithm( new QgsDelaunayTriangulationAlgorithm() );
   addAlgorithm( new QgsDeleteDuplicateGeometriesAlgorithm() );
   addAlgorithm( new QgsDetectVectorChangesAlgorithm() );