Add QgsAbstractGeometry::simplifiedTypeRef

Returns a reference to the simplest lossless representation of this geometry,
e.g. if the geometry is a multipart geometry type with a single member geometry,
a reference to that part will be returned.

This method employs the following logic:

- For multipart geometries containing a single part only a direct reference to that part will be returned.
- For compound curve geometries containing a single curve only a direct reference to that curve will be returned.

This method returns a reference only, and does not involve any geometry cloning.

python/core/auto_generated/geometry/qgsabstractgeometry.sip.in

@@ -719,6 +719,22 @@ Converts the geometry to a specified type.
 :return: ``True`` if conversion was successful
 
 .. versionadded:: 2.14
+%End
+
+    virtual const QgsAbstractGeometry *simplifiedTypeRef() const /HoldGIL/;
+%Docstring
+Returns a reference to the simplest lossless representation of this geometry,
+e.g. if the geometry is a multipart geometry type with a single member geometry,
+a reference to that part will be returned.
+
+This method employs the following logic:
+
+- For multipart geometries containing a single part only a direct reference to that part will be returned.
+- For compound curve geometries containing a single curve only a direct reference to that curve will be returned.
+
+This method returns a reference only, and does not involve any geometry cloning.
+
+.. versionadded:: 3.20
 %End
 
     virtual bool isValid( QString &error /Out/, int flags = 0 ) const = 0;

python/core/auto_generated/geometry/qgscompoundcurve.sip.in

@@ -85,6 +85,8 @@ of the curve.
 
     virtual bool boundingBoxIntersects( const QgsRectangle &rectangle ) const /HoldGIL/;
 
+    virtual const QgsAbstractGeometry *simplifiedTypeRef() const /HoldGIL/;
+
 
     int nCurves() const /HoldGIL/;
 %Docstring

python/core/auto_generated/geometry/qgsgeometrycollection.sip.in

@@ -245,6 +245,8 @@ Returns a geometry without curves. Caller takes ownership
 
     virtual QgsGeometryCollection *toCurveType() const /Factory/;
 
+    virtual const QgsAbstractGeometry *simplifiedTypeRef() const /HoldGIL/;
+
 
     virtual bool transform( QgsAbstractGeometryTransformer *transformer, QgsFeedback *feedback = 0 );
 

src/3d/symbols/qgsline3dsymbol_p.cpp

@@ -105,12 +105,14 @@ void QgsBufferedLine3DSymbolHandler::processFeature( const QgsFeature &f, const
   LineData &out = mSelectedIds.contains( f.id() ) ? outSelected : outNormal;
 
   QgsGeometry geom = f.geometry();
+  const QgsAbstractGeometry *g = geom.constGet()->simplifiedTypeRef();
 
   // segmentize curved geometries if necessary
-  if ( QgsWkbTypes::isCurvedType( geom.constGet()->wkbType() ) )
-    geom = QgsGeometry( geom.constGet()->segmentize() );
-
-  const QgsAbstractGeometry *g = geom.constGet();
+  if ( QgsWkbTypes::isCurvedType( g->wkbType() ) )
+  {
+    geom = QgsGeometry( g->segmentize() );
+    g = geom.constGet()->simplifiedTypeRef();
+  }
 
   // TODO: configurable
   const int nSegments = 4;
@@ -375,11 +377,14 @@ void QgsThickLine3DSymbolHandler::processFeature( const QgsFeature &f, const Qgs
   QgsLineVertexData &out = mSelectedIds.contains( f.id() ) ? outSelected : outNormal;
 
   QgsGeometry geom = f.geometry();
-  // segmentize curved geometries if necessary
-  if ( QgsWkbTypes::isCurvedType( geom.constGet()->wkbType() ) )
-    geom = QgsGeometry( geom.constGet()->segmentize() );
+  const QgsAbstractGeometry *g = geom.constGet()->simplifiedTypeRef();
 
-  const QgsAbstractGeometry *g = geom.constGet();
+  // segmentize curved geometries if necessary
+  if ( QgsWkbTypes::isCurvedType( g->wkbType() ) )
+  {
+    geom = QgsGeometry( g->segmentize() );
+    g = geom.constGet()->simplifiedTypeRef();
+  }
 
   if ( const QgsLineString *ls = qgsgeometry_cast<const QgsLineString *>( g ) )
   {

src/3d/symbols/qgspolygon3dsymbol_p.cpp

@@ -163,12 +163,14 @@ void QgsPolygon3DSymbolHandler::processFeature( const QgsFeature &f, const Qgs3D
   PolygonData &out = mSelectedIds.contains( f.id() ) ? outSelected : outNormal;
 
   QgsGeometry geom = f.geometry();
+  const QgsAbstractGeometry *g = geom.constGet()->simplifiedTypeRef();
 
   // segmentize curved geometries if necessary
-  if ( QgsWkbTypes::isCurvedType( geom.constGet()->wkbType() ) )
-    geom = QgsGeometry( geom.constGet()->segmentize() );
-
-  const QgsAbstractGeometry *g = geom.constGet();
+  if ( QgsWkbTypes::isCurvedType( g->wkbType() ) )
+  {
+    geom = QgsGeometry( g->segmentize() );
+    g = geom.constGet()->simplifiedTypeRef();
+  }
 
   const QgsPropertyCollection &ddp = mSymbol->dataDefinedProperties();
   bool hasDDHeight = ddp.isActive( QgsAbstract3DSymbol::PropertyHeight );

src/core/geometry/qgsabstractgeometry.cpp

@@ -280,6 +280,11 @@ bool QgsAbstractGeometry::convertTo( QgsWkbTypes::Type type )
   return true;
 }
 
+const QgsAbstractGeometry *QgsAbstractGeometry::simplifiedTypeRef() const
+{
+  return this;
+}
+
 void QgsAbstractGeometry::filterVertices( const std::function<bool ( const QgsPoint & )> & )
 {
   // Ideally this would be pure virtual, but SIP has issues with that

src/core/geometry/qgsabstractgeometry.h

@@ -706,6 +706,22 @@ class CORE_EXPORT QgsAbstractGeometry
      */
     virtual bool convertTo( QgsWkbTypes::Type type );
 
+    /**
+     * Returns a reference to the simplest lossless representation of this geometry,
+     * e.g. if the geometry is a multipart geometry type with a single member geometry,
+     * a reference to that part will be returned.
+     *
+     * This method employs the following logic:
+     *
+     * - For multipart geometries containing a single part only a direct reference to that part will be returned.
+     * - For compound curve geometries containing a single curve only a direct reference to that curve will be returned.
+     *
+     * This method returns a reference only, and does not involve any geometry cloning.
+     *
+     * \since QGIS 3.20
+     */
+    virtual const QgsAbstractGeometry *simplifiedTypeRef() const SIP_HOLDGIL;
+
     /**
      * Checks validity of the geometry, and returns TRUE if the geometry is valid.
      *

src/core/geometry/qgscompoundcurve.cpp

@@ -562,6 +562,14 @@ bool QgsCompoundCurve::boundingBoxIntersects( const QgsRectangle &rectangle ) co
   return QgsAbstractGeometry::boundingBoxIntersects( rectangle );
 }
 
+const QgsAbstractGeometry *QgsCompoundCurve::simplifiedTypeRef() const
+{
+  if ( mCurves.size() == 1 )
+    return mCurves.at( 0 );
+  else
+    return this;
+}
+
 const QgsCurve *QgsCompoundCurve::curveAt( int i ) const
 {
   if ( i < 0 || i >= mCurves.size() )

src/core/geometry/qgscompoundcurve.h

@@ -74,6 +74,7 @@ class CORE_EXPORT QgsCompoundCurve: public QgsCurve
     QgsCompoundCurve *snappedToGrid( double hSpacing, double vSpacing, double dSpacing = 0, double mSpacing = 0 ) const override SIP_FACTORY;
     bool removeDuplicateNodes( double epsilon = 4 * std::numeric_limits<double>::epsilon(), bool useZValues = false ) override;
     bool boundingBoxIntersects( const QgsRectangle &rectangle ) const override SIP_HOLDGIL;
+    const QgsAbstractGeometry *simplifiedTypeRef() const override SIP_HOLDGIL;
 
     /**
      * Returns the number of curves in the geometry.

src/core/geometry/qgsgeometrycollection.cpp

@@ -1020,6 +1020,14 @@ QgsGeometryCollection *QgsGeometryCollection::toCurveType() const
   return newCollection.release();
 }
 
+const QgsAbstractGeometry *QgsGeometryCollection::simplifiedTypeRef() const
+{
+  if ( mGeometries.size() == 1 )
+    return mGeometries.at( 0 )->simplifiedTypeRef();
+  else
+    return this;
+}
+
 bool QgsGeometryCollection::transform( QgsAbstractGeometryTransformer *transformer, QgsFeedback *feedback )
 {
   if ( !transformer )

src/core/geometry/qgsgeometrycollection.h

@@ -237,6 +237,7 @@ class CORE_EXPORT QgsGeometryCollection: public QgsAbstractGeometry
     bool dropMValue() override;
     void swapXy() override;
     QgsGeometryCollection *toCurveType() const override SIP_FACTORY;
+    const QgsAbstractGeometry *simplifiedTypeRef() const override SIP_HOLDGIL;
 
     bool transform( QgsAbstractGeometryTransformer *transformer, QgsFeedback *feedback = nullptr ) override;
 

tests/src/core/testqgsgeometry.cpp

@@ -172,6 +172,9 @@ class TestQgsGeometry : public QObject
     void normalize_data();
     void normalize();
 
+    void simplifiedTypeRef_data();
+    void simplifiedTypeRef();
+
     // MK, Disabled 14.11.2014
     // Too unclear what exactly should be tested and which variations are allowed for the line
 #if 0
@@ -17878,6 +17881,36 @@ void TestQgsGeometry::normalize()
   QCOMPARE( geom.asWkt( 1 ), expected );
 }
 
+
+void TestQgsGeometry::simplifiedTypeRef_data()
+{
+  QTest::addColumn<QString>( "wkt" );
+  QTest::addColumn<QString>( "expected" );
+
+  QTest::newRow( "point empty" ) << QStringLiteral( "POINT EMPTY" )  << QStringLiteral( "Point EMPTY" );
+  QTest::newRow( "point" ) << QStringLiteral( "POINT (1 2)" )  << QStringLiteral( "Point (1 2)" );
+  QTest::newRow( "line empty" ) << QStringLiteral( "LINESTRING EMPTY" )  << QStringLiteral( "LineString EMPTY" );
+  QTest::newRow( "line" ) << QStringLiteral( "LINESTRING (1 1, 1 2, 1 3)" )  << QStringLiteral( "LineString (1 1, 1 2, 1 3)" );
+  QTest::newRow( "circular string" ) << QStringLiteral( "CIRCULARSTRINGZM (1 1 11 21, 1 0 12 22, 0 0 13 23, 0 1 14 24, 1 1 11 21)" )  << QStringLiteral( "CircularStringZM (1 1 11 21, 1 0 12 22, 0 0 13 23, 0 1 14 24, 1 1 11 21)" );
+  QTest::newRow( "compound curve empty" ) << QStringLiteral( "COMPOUNDCURVE EMPTY" )  << QStringLiteral( "CompoundCurve EMPTY" );
+  QTest::newRow( "compound curve one curve" ) << QStringLiteral( "COMPOUNDCURVE ((1 1, 1 2, 2 3))" )  << QStringLiteral( "LineString (1 1, 1 2, 2 3)" );
+  QTest::newRow( "compound curve two curves" ) << QStringLiteral( "COMPOUNDCURVE ((1 1, 1 2, 2 3),(2 3, 4 4))" )  << QStringLiteral( "CompoundCurve ((1 1, 1 2, 2 3),(2 3, 4 4))" );
+  QTest::newRow( "polygon empty" ) << QStringLiteral( "POLYGON EMPTY" )  << QStringLiteral( "Polygon EMPTY" );
+  QTest::newRow( "polygon exterior" ) << QStringLiteral( "POLYGON ((1 1, 0 1, 0 0, 1 0, 1 1))" )  << QStringLiteral( "Polygon ((1 1, 0 1, 0 0, 1 0, 1 1))" );
+  QTest::newRow( "collection empty" ) << QStringLiteral( "GEOMETRYCOLLECTION EMPTY" )  << QStringLiteral( "GeometryCollection EMPTY" );
+  QTest::newRow( "multipoint one point" ) << QStringLiteral( "MULTIPOINT(1 1)" )  << QStringLiteral( "Point (1 1)" );
+  QTest::newRow( "multipoint" ) << QStringLiteral( "MULTIPOINT(1 1, 3 4, 1 3, 2 2)" )  << QStringLiteral( "MultiPoint ((1 1),(3 4),(1 3),(2 2))" );
+}
+
+void TestQgsGeometry::simplifiedTypeRef()
+{
+  QFETCH( QString, wkt );
+  QFETCH( QString, expected );
+
+  QgsGeometry geom = QgsGeometry::fromWkt( wkt );
+  QCOMPARE( geom.constGet()->simplifiedTypeRef()->asWkt( 1 ), expected );
+}
+
 // MK, Disabled 14.11.2014
 // Too unclear what exactly should be tested and which variations are allowed for the line
 #if 0