Fix 2.5D renderer problem when order of walls matters

E.g. when the walls have different styles

Author: m-kuhn

resources/function_help/json/order_parts

@@ -0,0 +1,20 @@
+{
+  "name": "order_parts",
+  "type": "function",
+  "description": "Orders the parts of a MultiGeometry by a given criteria",
+  "arguments": [
+    {"arg":"geom","description":"a multi-type geometry"},
+    {"arg":"orderby","description":"an expression string defining the order criteria"},
+    {"arg":"ascending","description":"boolean, True for ascending, False for descending"}
+  ],
+  "examples": [
+    {
+      "expression":"order_parts(geom_from_wkt('MultiPolygon (((1 1, 5 1, 5 5, 1 5, 1 1)),((1 1, 9 1, 9 9, 1 9, 1 1)))'), 'area($geometry)', False)",
+      "returns":"MultiPolygon (((1 1, 9 1, 9 9, 1 9, 1 1)),((1 1, 5 1, 5 5, 1 5, 1 1)))"
+    },
+    {
+      "expression":"order_parts(geom_from_wkt('LineString(1 2, 3 2, 4 3)'), '1', True)",
+      "returns":"LineString(1 2, 3 2, 4 3)"
+    }
+  ]
+}

src/core/qgsexpression.cpp

@@ -46,6 +46,7 @@
 #include "qgsmultilinestringv2.h"
 #include "qgscurvepolygonv2.h"
 #include "qgsexpressionprivate.h"
+#include "qgsexpressionsorter.h"
 
 #if QT_VERSION < 0x050000
 #include <qtextdocument.h>
@@ -2168,6 +2169,70 @@ static QVariant fcnExtrude( const QVariantList& values, const QgsExpressionConte
   return result;
 }
 
+static QVariant fcnOrderParts( const QVariantList& values, const QgsExpressionContext* ctx, QgsExpression* parent )
+{
+  if ( values.length() < 2 )
+    return QVariant();
+
+  QgsGeometry fGeom = getGeometry( values.at( 0 ), parent );
+
+  if ( !fGeom.isMultipart() )
+    return values.at( 0 );
+
+  QString expString = getStringValue( values.at( 1 ), parent );
+  bool asc = values.value( 2 ).toBool();
+
+  QgsExpressionContext* unconstedContext;
+  QgsFeature f;
+  if ( ctx )
+  {
+    // ExpressionSorter wants a modifiable expression context, but it will return it in the same shape after
+    // so no reason to worry
+    unconstedContext = const_cast<QgsExpressionContext*>( ctx );
+    f = ctx->feature();
+  }
+  else
+  {
+    // If there's no context provided, create a fake one
+    unconstedContext = new QgsExpressionContext();
+  }
+
+  QgsGeometryCollectionV2* collection = dynamic_cast<QgsGeometryCollectionV2*>( fGeom.geometry() );
+  Q_ASSERT( collection ); // Should have failed the multipart check above
+
+  QgsFeatureRequest::OrderBy orderBy;
+  orderBy.append( QgsFeatureRequest::OrderByClause( expString, asc ) );
+  QgsExpressionSorter sorter( orderBy );
+
+  QList<QgsFeature> partFeatures;
+  for ( int i = 0; i < collection->partCount(); ++i )
+  {
+    f.setGeometry( QgsGeometry( collection->geometryN( i )->clone() ) );
+    partFeatures << f;
+  }
+
+  sorter.sortFeatures( partFeatures, unconstedContext );
+
+  QgsGeometryCollectionV2* orderedGeom = dynamic_cast<QgsGeometryCollectionV2*>( fGeom.geometry()->clone() );
+
+  Q_ASSERT( orderedGeom );
+
+  while ( orderedGeom->partCount() )
+    orderedGeom->removeGeometry( 0 );
+
+  Q_FOREACH ( const QgsFeature& feature, partFeatures )
+  {
+    orderedGeom->addGeometry( feature.constGeometry()->geometry()->clone() );
+  }
+
+  QVariant result = QVariant::fromValue( QgsGeometry( orderedGeom ) );
+
+  if ( !ctx )
+    delete unconstedContext;
+
+  return result;
+}
+
 static QVariant fcnClosestPoint( const QVariantList& values, const QgsExpressionContext*, QgsExpression* parent )
 {
   QgsGeometry fromGeom = getGeometry( values.at( 0 ), parent );
@@ -2954,6 +3019,7 @@ const QList<QgsExpression::Function*>& QgsExpression::Functions()
     << new StaticFunction( "geometry", 1, fcnGetGeometry, "GeometryGroup", QString(), true )
     << new StaticFunction( "transform", 3, fcnTransformGeometry, "GeometryGroup" )
     << new StaticFunction( "extrude", 3, fcnExtrude, "GeometryGroup", QString() )
+    << new StaticFunction( "order_parts", 3, fcnOrderParts, "GeometryGroup", QString() )
     << new StaticFunction( "closest_point", 2, fcnClosestPoint, "GeometryGroup" )
     << new StaticFunction( "shortest_line", 2, fcnShortestLine, "GeometryGroup" )
     << new StaticFunction( "$rownum", 0, fcnRowNumber, "deprecated" )

src/core/symbology-ng/qgs25drenderer.cpp

@@ -28,10 +28,24 @@
   ")"
 
 #define WALL_EXPRESSION \
-  "extrude(" \
-  "  segments_to_lines( exterior_ring( $geometry ) )," \
-  "  cos( radians( eval( @qgis_25d_angle ) ) ) * eval( @qgis_25d_height )," \
-  "  sin( radians( eval( @qgis_25d_angle ) ) ) * eval( @qgis_25d_height )" \
+  "order_parts( "\
+  "  extrude(" \
+  "    segments_to_lines( exterior_ring( $geometry ) )," \
+  "    cos( radians( eval( @qgis_25d_angle ) ) ) * eval( @qgis_25d_height )," \
+  "    sin( radians( eval( @qgis_25d_angle ) ) ) * eval( @qgis_25d_height )" \
+  "  )," \
+  "  'distance(  $geometry,  translate(    @map_extent_center,    1000 * @map_extent_width * cos( radians( @qgis_25d_angle + 180 ) ),    1000 * @map_extent_width * sin( radians( @qgis_25d_angle + 180 ) )  ))'," \
+  "  False" \
+  ")"
+
+#define ORDER_BY_EXPRESSION \
+  "distance(" \
+  "  $geometry," \
+  "  translate(" \
+  "    @map_extent_center," \
+  "    1000 * @map_extent_width * cos( radians( @qgis_25d_angle + 180 ) )," \
+  "    1000 * @map_extent_width * sin( radians( @qgis_25d_angle + 180 ) )" \
+  "  )" \
   ")"
 
 Qgs25DRenderer::Qgs25DRenderer()
@@ -75,14 +89,7 @@ Qgs25DRenderer::Qgs25DRenderer()
 
   QgsFeatureRequest::OrderBy orderBy;
   orderBy << QgsFeatureRequest::OrderByClause(
-    "distance("
-    "  $geometry,"
-    "  translate("
-    "    @map_extent_center,"
-    "    1000 * @map_extent_width * cos( radians( @qgis_25d_angle + 180 ) ),"
-    "    1000 * @map_extent_width * sin( radians( @qgis_25d_angle + 180 ) )"
-    "  )"
-    ")",
+    ORDER_BY_EXPRESSION,
     false );
 
   setOrderBy( orderBy );

tests/src/core/testqgsexpression.cpp

@@ -586,6 +586,9 @@ class TestQgsExpression: public QObject
       QTest::newRow( "extrude geom" ) << "geom_to_wkt(extrude( geom_from_wkt('LineString( 1 2, 3 2, 4 3)'),1,2))" << false << QVariant( "Polygon ((1 2, 3 2, 4 3, 5 5, 4 4, 2 4, 1 2))" );
       QTest::newRow( "extrude not geom" ) << "extrude('g',5,6)" << true << QVariant();
       QTest::newRow( "extrude null" ) << "extrude(NULL,5,6)" << false << QVariant();
+      QTest::newRow( "order parts" ) << "geom_to_wkt(order_parts(geom_from_wkt('MultiPolygon (((1 1, 5 1, 5 5, 1 5, 1 1)),((1 1, 9 1, 9 9, 1 9, 1 1)))'), 'area($geometry)', False ) )" << false << QVariant( "MultiPolygon (((1 1, 9 1, 9 9, 1 9, 1 1)),((1 1, 5 1, 5 5, 1 5, 1 1)))" );
+      QTest::newRow( "order parts not geom" ) << "order_parts('g', 'area($geometry)', False )" << true << QVariant();
+      QTest::newRow( "order parts single geom" ) << "geom_to_wkt(order_parts(geom_from_wkt('POLYGON((2 0,2 2, 3 2, 3 0, 2 0))'), 'area($geometry)', False))" << false << QVariant( "Polygon ((2 0, 2 2, 3 2, 3 0, 2 0))" );
       QTest::newRow( "closest_point geom" ) << "geom_to_wkt(closest_point( geom_from_wkt('LineString( 1 1, 5 1, 5 5 )'),geom_from_wkt('Point( 6 3 )')))" << false << QVariant( "Point (5 3)" );
       QTest::newRow( "closest_point not geom" ) << "closest_point('g','b')" << true << QVariant();
       QTest::newRow( "closest_point null" ) << "closest_point(NULL,NULL)" << false << QVariant();