[FEATURE] Add translate expression function

Funded by
 * Regional Council of Picardy
 * ADUGA
 * Ville de Nyon
 * Wetu GIT cc

resources/function_help/json/translate

@@ -0,0 +1,10 @@
+{
+  "name": "translate",
+  "type": "function",
+  "description": "Returns a translated version of a geometry. Calculations are in the Spatial Reference System of this geometry.",
+  "arguments": [ {"arg":"geom","description":"a geometry"},
+                 {"arg":"dx","description":"delta x"},
+                 {"arg":"dy","description":"delta y"}
+               ],
+  "examples": [ { "expression":"translate($geometry, 5, 10)", "returns":"a geometry of the same type like the original one"}]
+}

src/core/qgsexpression.cpp

@@ -1710,6 +1710,14 @@ static QVariant fcnBuffer( const QVariantList& values, const QgsExpressionContex
   delete geom;
   return result;
 }
+static QVariant fcnTranslate( const QVariantList& values, const QgsExpressionContext*, QgsExpression* parent )
+{
+  QgsGeometry fGeom = getGeometry( values.at( 0 ), parent );
+  double dx = getDoubleValue( values.at( 1 ), parent );
+  double dy = getDoubleValue( values.at( 2 ), parent );
+  fGeom.translate( dx, dy );
+  return QVariant::fromValue( fGeom );
+}
 static QVariant fcnCentroid( const QVariantList& values, const QgsExpressionContext*, QgsExpression* parent )
 {
   QgsGeometry fGeom = getGeometry( values.at( 0 ), parent );
@@ -2495,6 +2503,7 @@ const QList<QgsExpression::Function*>& QgsExpression::Functions()
     << new StaticFunction( "contains", 2, fcnContains, "GeometryGroup" )
     << new StaticFunction( "overlaps", 2, fcnOverlaps, "GeometryGroup" )
     << new StaticFunction( "within", 2, fcnWithin, "GeometryGroup" )
+    << new StaticFunction( "translate", 3, fcnTranslate, "GeometryGroup" )
     << new StaticFunction( "buffer", -1, fcnBuffer, "GeometryGroup" )
     << new StaticFunction( "centroid", 1, fcnCentroid, "GeometryGroup" )
     << new StaticFunction( "reverse", 1, fcnReverse, "GeometryGroup" )

tests/src/core/testqgsexpression.cpp

@@ -1424,7 +1424,9 @@ class TestQgsExpression: public QObject
       QTest::addColumn<bool>( "needGeom" );
       QTest::addColumn<void*>( "resultptr" );
 
-      QgsPolyline polygon_ring;
+      QgsPoint point( 0, 0 );
+      QgsPolyline line, polygon_ring;
+      line << QgsPoint( 0, 0 ) << QgsPoint( 10, 10 );
       polygon_ring << QgsPoint( 0, 0 ) << QgsPoint( 10, 10 ) << QgsPoint( 10, 0 ) << QgsPoint( 0, 0 );
       QgsPolygon polygon;
       polygon << polygon_ring;
@@ -1460,6 +1462,13 @@ class TestQgsExpression: public QObject
       QTest::newRow( "convexHull multi" ) << "convexHull( geomFromWKT('GEOMETRYCOLLECTION(POINT(0 1), POINT(0 0), POINT(1 0), POINT(1 1))') )" << ( void* ) geom << false << false << ( void* ) QgsGeometry::fromWkt( "POLYGON ((0 0,0 1,1 1,1 0,0 0))" );
       geom = QgsGeometry::fromPolygon( polygon );
       QTest::newRow( "bounds" ) << "bounds( $geometry )" << ( void* ) geom << false << true << ( void* ) QgsGeometry::fromRect( geom->boundingBox() );
+
+      geom = QgsGeometry::fromPolygon( polygon );
+      QTest::newRow( "translate" ) << "translate( $geometry, 1, 2)" << ( void* ) geom << false << true << ( void* ) QgsGeometry::fromWkt( "POLYGON ((1 2,11 12,11 2,1 2))" );
+      geom = QgsGeometry::fromPolyline( line );
+      QTest::newRow( "translate" ) << "translate( $geometry, -1, 2)" << ( void* ) geom << false << true << ( void* ) QgsGeometry::fromWkt( "LINESTRING (-1 2, 9 12)" );
+      geom = QgsGeometry::fromPoint( point );
+      QTest::newRow( "translate" ) << "translate( $geometry, 1, -2)" << ( void* ) geom << false << true << ( void* ) QgsGeometry::fromWkt( "POINT(1 -2)" );
     }
 
     void eval_geometry_method()