Merge pull request #3341 from nyalldawson/boundary

New method for calculating geometry boundary

Author: nyalldawson

python/core/geometry/qgsabstractgeometryv2.sip

@@ -130,6 +130,13 @@ class QgsAbstractGeometryV2
      */
     bool isMeasure() const;
 
+    /** Returns the closure of the combinatorial boundary of the geometry (ie the topological boundary of the geometry).
+     * For instance, a polygon geometry will have a boundary consisting of the linestrings for each ring in the polygon.
+     * @returns boundary for geometry. May be null for some geometry types.
+     * @note added in QGIS 3.0
+     */
+    virtual QgsAbstractGeometryV2* boundary() const = 0;
+
     //import
 
     /** Sets the geometry from a WKB string.

python/core/geometry/qgscurvepolygonv2.sip

@@ -29,6 +29,8 @@ class QgsCurvePolygonV2: public QgsSurfaceV2
     virtual double area() const;
     virtual double perimeter() const;
     QgsPolygonV2* surfaceToPolygon() const;
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
+
 
     //curve polygon interface
     int numInteriorRings() const;

python/core/geometry/qgscurvev2.sip

@@ -75,6 +75,8 @@ class QgsCurveV2: public QgsAbstractGeometryV2
      */
     virtual QgsCurveV2* reversed() const = 0 /Factory/;
 
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
+
     /** Returns a geometry without curves. Caller takes ownership
     * @param tolerance segmentation tolerance
     * @param toleranceType maximum segmentation angle or maximum difference between approximation and curve*/

python/core/geometry/qgsgeometrycollectionv2.sip

@@ -30,6 +30,7 @@ class QgsGeometryCollectionV2: public QgsAbstractGeometryV2
     virtual int dimension() const;
     virtual QString geometryType() const;
     virtual void clear();
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
 
     /** Adds a geometry and takes ownership. Returns true in case of success.*/
     virtual bool addGeometry( QgsAbstractGeometryV2* g /Transfer/ );

python/core/geometry/qgsmulticurvev2.sip

@@ -26,4 +26,6 @@ class QgsMultiCurveV2: public QgsGeometryCollectionV2
      * @note added in QGIS 2.14
      */
     QgsMultiCurveV2* reversed() const /Factory/;
+
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
 };

python/core/geometry/qgsmultipointv2.sip

@@ -20,6 +20,8 @@ class QgsMultiPointV2: public QgsGeometryCollectionV2
     /** Adds a geometry and takes ownership. Returns true in case of success*/
     virtual bool addGeometry( QgsAbstractGeometryV2* g );
 
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
+
   protected:
 
     virtual bool wktOmitChildType() const;

python/core/geometry/qgsmultipolygonv2.sip

@@ -24,6 +24,8 @@ class QgsMultiPolygonV2: public QgsMultiSurfaceV2
     @return the converted geometry. Caller takes ownership*/
     QgsAbstractGeometryV2* toCurveType() const /Factory/;
 
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
+
   protected:
 
     virtual bool wktOmitChildType() const;

python/core/geometry/qgsmultisurfacev2.sip

@@ -20,6 +20,8 @@ class QgsMultiSurfaceV2: public QgsGeometryCollectionV2
     /** Adds a geometry and takes ownership. Returns true in case of success*/
     virtual bool addGeometry( QgsAbstractGeometryV2* g );
 
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
+
     /** Returns a geometry without curves. Caller takes ownership*/
     QgsAbstractGeometryV2* segmentize() const /Factory/;
 };

python/core/geometry/qgspointv2.sip

@@ -157,6 +157,7 @@ class QgsPointV2: public QgsAbstractGeometryV2
                     bool transformZ = false );
     void transform( const QTransform& t );
     virtual QList< QList< QList< QgsPointV2 > > > coordinateSequence() const;
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
 
     //low-level editing
     virtual bool insertVertex( QgsVertexId position, const QgsPointV2& vertex );

python/core/geometry/qgspolygonv2.sip

@@ -35,4 +35,5 @@ class QgsPolygonV2: public QgsCurvePolygonV2
     //overridden to handle LineString25D rings
     virtual void setExteriorRing( QgsCurveV2* ring /Transfer/ );
 
+    virtual QgsAbstractGeometryV2* boundary() const /Factory/;
 };

resources/function_help/json/boundary

@@ -0,0 +1,8 @@
+{
+  "name": "boundary",
+  "type": "function",
+  "description":"Returns the closure of the combinatorial boundary of the geometry (ie the topological boundary of the geometry). For instance, a polygon geometry will have a boundary consisting of the linestrings for each ring in the polygon. Some geometry types do not have a defined boundary, eg points or geometry collections, and will return null.",
+  "arguments": [ {"arg":"geometry","description":"a geometry"} ],
+  "examples": [ { "expression":"geom_to_wkt(boundary(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))')))", "returns":"'LineString(1 1,0 0,-1 1,1 1)'"}]
+}
+

src/core/geometry/qgsabstractgeometryv2.h

@@ -111,10 +111,16 @@ class CORE_EXPORT QgsAbstractGeometryV2
     virtual bool isValid() const = 0;
     virtual QgsMultiPointV2* locateAlong() const = 0;
     virtual QgsMultiCurveV2* locateBetween() const = 0;
-    virtual QgsCurveV2* boundary() const = 0;
     virtual QgsRectangle envelope() const = 0;
 #endif
 
+    /** Returns the closure of the combinatorial boundary of the geometry (ie the topological boundary of the geometry).
+     * For instance, a polygon geometry will have a boundary consisting of the linestrings for each ring in the polygon.
+     * @returns boundary for geometry. May be null for some geometry types.
+     * @note added in QGIS 3.0
+     */
+    virtual QgsAbstractGeometryV2* boundary() const = 0;
+
     //import
 
     /** Sets the geometry from a WKB string.

src/core/geometry/qgscurvepolygonv2.cpp

@@ -23,6 +23,7 @@
 #include "qgslinestringv2.h"
 #include "qgspolygonv2.h"
 #include "qgswkbptr.h"
+#include "qgsmulticurvev2.h"
 #include <QPainter>
 #include <QPainterPath>
 
@@ -420,6 +421,25 @@ QgsPolygonV2* QgsCurvePolygonV2::surfaceToPolygon() const
   return polygon;
 }
 
+QgsAbstractGeometryV2* QgsCurvePolygonV2::boundary() const
+{
+  if ( mInteriorRings.isEmpty() )
+  {
+    return mExteriorRing->clone();
+  }
+  else
+  {
+    QgsMultiCurveV2* multiCurve = new QgsMultiCurveV2();
+    multiCurve->addGeometry( mExteriorRing->clone() );
+    int nInteriorRings = mInteriorRings.size();
+    for ( int i = 0; i < nInteriorRings; ++i )
+    {
+      multiCurve->addGeometry( mInteriorRings.at( i )->clone() );
+    }
+    return multiCurve;
+  }
+}
+
 QgsPolygonV2* QgsCurvePolygonV2::toPolygon( double tolerance, SegmentationToleranceType toleranceType ) const
 {
   if ( !mExteriorRing )

src/core/geometry/qgscurvepolygonv2.h

@@ -55,6 +55,7 @@ class CORE_EXPORT QgsCurvePolygonV2: public QgsSurfaceV2
     virtual double area() const override;
     virtual double perimeter() const override;
     QgsPolygonV2* surfaceToPolygon() const override;
+    virtual QgsAbstractGeometryV2* boundary() const override;
 
     //curve polygon interface
     int numInteriorRings() const;

src/core/geometry/qgscurvev2.cpp

@@ -18,6 +18,7 @@
 #include "qgscurvev2.h"
 #include "qgslinestringv2.h"
 #include "qgspointv2.h"
+#include "qgsmultipointv2.h"
 
 QgsCurveV2::QgsCurveV2(): QgsAbstractGeometryV2()
 {}
@@ -80,6 +81,20 @@ bool QgsCurveV2::nextVertex( QgsVertexId& id, QgsPointV2& vertex ) const
   return pointAt( id.vertex, vertex, id.type );
 }
 
+QgsAbstractGeometryV2* QgsCurveV2::boundary() const
+{
+  if ( isEmpty() )
+    return nullptr;
+
+  if ( isClosed() )
+    return nullptr;
+
+  QgsMultiPointV2* multiPoint = new QgsMultiPointV2();
+  multiPoint->addGeometry( new QgsPointV2( startPoint() ) );
+  multiPoint->addGeometry( new QgsPointV2( endPoint() ) );
+  return multiPoint;
+}
+
 QgsCurveV2* QgsCurveV2::segmentize( double tolerance, SegmentationToleranceType toleranceType ) const
 {
   return curveToLine( tolerance, toleranceType );

src/core/geometry/qgscurvev2.h

@@ -102,6 +102,8 @@ class CORE_EXPORT QgsCurveV2: public QgsAbstractGeometryV2
      */
     virtual QgsCurveV2* reversed() const = 0;
 
+    virtual QgsAbstractGeometryV2* boundary() const override;
+
     /** Returns a geometry without curves. Caller takes ownership
      * @param tolerance segmentation tolerance
      * @param toleranceType maximum segmentation angle or maximum difference between approximation and curve*/

src/core/geometry/qgsgeometrycollectionv2.cpp

@@ -75,6 +75,11 @@ void QgsGeometryCollectionV2::clear()
   clearCache(); //set bounding box invalid
 }
 
+QgsAbstractGeometryV2*QgsGeometryCollectionV2::boundary() const
+{
+  return nullptr;
+}
+
 int QgsGeometryCollectionV2::numGeometries() const
 {
   return mGeometries.size();

src/core/geometry/qgsgeometrycollectionv2.h

@@ -54,6 +54,7 @@ class CORE_EXPORT QgsGeometryCollectionV2: public QgsAbstractGeometryV2
     virtual int dimension() const override;
     virtual QString geometryType() const override { return "GeometryCollection"; }
     virtual void clear() override;
+    virtual QgsAbstractGeometryV2* boundary() const override;
 
     /** Adds a geometry and takes ownership. Returns true in case of success.*/
     virtual bool addGeometry( QgsAbstractGeometryV2* g );

src/core/geometry/qgsmulticurvev2.cpp

@@ -20,6 +20,7 @@ email                : marco.hugentobler at sourcepole dot com
 #include "qgscompoundcurvev2.h"
 #include "qgsgeometryutils.h"
 #include "qgslinestringv2.h"
+#include "qgsmultipointv2.h"
 
 QgsMultiCurveV2::QgsMultiCurveV2()
     : QgsGeometryCollectionV2()
@@ -125,3 +126,25 @@ QgsMultiCurveV2* QgsMultiCurveV2::reversed() const
   }
   return reversedMultiCurve;
 }
+
+QgsAbstractGeometryV2* QgsMultiCurveV2::boundary() const
+{
+  QgsMultiPointV2* multiPoint = new QgsMultiPointV2();
+  for ( int i = 0; i < mGeometries.size(); ++i )
+  {
+    if ( QgsCurveV2* curve = dynamic_cast<QgsCurveV2*>( mGeometries.at( i ) ) )
+    {
+      if ( !curve->isClosed() )
+      {
+        multiPoint->addGeometry( new QgsPointV2( curve->startPoint() ) );
+        multiPoint->addGeometry( new QgsPointV2( curve->endPoint() ) );
+      }
+    }
+  }
+  if ( multiPoint->numGeometries() == 0 )
+  {
+    delete multiPoint;
+    return nullptr;
+  }
+  return multiPoint;
+}

src/core/geometry/qgsmulticurvev2.h

@@ -47,6 +47,9 @@ class CORE_EXPORT QgsMultiCurveV2: public QgsGeometryCollectionV2
      * @note added in QGIS 2.14
      */
     QgsMultiCurveV2* reversed() const;
+
+    virtual QgsAbstractGeometryV2* boundary() const override;
+
 };
 
 #endif // QGSMULTICURVEV2_H

src/core/geometry/qgsmultilinestringv2.cpp

@@ -118,3 +118,4 @@ QgsAbstractGeometryV2* QgsMultiLineStringV2::toCurveType() const
   }
   return multiCurve;
 }
+

src/core/geometry/qgsmultipointv2.cpp

@@ -105,3 +105,8 @@ bool QgsMultiPointV2::addGeometry( QgsAbstractGeometryV2* g )
   setZMTypeFromSubGeometry( g, QgsWKBTypes::MultiPoint );
   return QgsGeometryCollectionV2::addGeometry( g );
 }
+
+QgsAbstractGeometryV2* QgsMultiPointV2::boundary() const
+{
+  return nullptr;
+}

src/core/geometry/qgsmultipointv2.h

@@ -44,6 +44,8 @@ class CORE_EXPORT QgsMultiPointV2: public QgsGeometryCollectionV2
     /** Adds a geometry and takes ownership. Returns true in case of success*/
     virtual bool addGeometry( QgsAbstractGeometryV2* g ) override;
 
+    virtual QgsAbstractGeometryV2* boundary() const override;
+
   protected:
 
     virtual bool wktOmitChildType() const override { return true; }

src/core/geometry/qgsmultipolygonv2.cpp

@@ -20,6 +20,7 @@ email                : marco.hugentobler at sourcepole dot com
 #include "qgslinestringv2.h"
 #include "qgspolygonv2.h"
 #include "qgscurvepolygonv2.h"
+#include "qgsmultilinestringv2.h"
 
 QgsMultiPolygonV2::QgsMultiPolygonV2()
     : QgsMultiSurfaceV2()
@@ -133,3 +134,38 @@ QgsAbstractGeometryV2* QgsMultiPolygonV2::toCurveType() const
   }
   return multiSurface;
 }
+
+QgsAbstractGeometryV2* QgsMultiPolygonV2::boundary() const
+{
+  QgsMultiLineStringV2* multiLine = new QgsMultiLineStringV2();
+  for ( int i = 0; i < mGeometries.size(); ++i )
+  {
+    if ( QgsPolygonV2* polygon = dynamic_cast<QgsPolygonV2*>( mGeometries.at( i ) ) )
+    {
+      QgsAbstractGeometryV2* polygonBoundary = polygon->boundary();
+
+      if ( QgsLineStringV2* lineStringBoundary = dynamic_cast< QgsLineStringV2* >( polygonBoundary ) )
+      {
+        multiLine->addGeometry( lineStringBoundary );
+      }
+      else if ( QgsMultiLineStringV2* multiLineStringBoundary = dynamic_cast< QgsMultiLineStringV2* >( polygonBoundary ) )
+      {
+        for ( int j = 0; j < multiLineStringBoundary->numGeometries(); ++j )
+        {
+          multiLine->addGeometry( multiLineStringBoundary->geometryN( j )->clone() );
+        }
+        delete multiLineStringBoundary;
+      }
+      else
+      {
+        delete polygonBoundary;
+      }
+    }
+  }
+  if ( multiLine->numGeometries() == 0 )
+  {
+    delete multiLine;
+    return nullptr;
+  }
+  return multiLine;
+}

src/core/geometry/qgsmultipolygonv2.h

@@ -40,14 +40,15 @@ class CORE_EXPORT QgsMultiPolygonV2: public QgsMultiSurfaceV2
     QDomElement asGML3( QDomDocument& doc, int precision = 17, const QString& ns = "gml" ) const override;
     QString asJSON( int precision = 17 ) const override;
 
-
     /** Adds a geometry and takes ownership. Returns true in case of success*/
     virtual bool addGeometry( QgsAbstractGeometryV2* g ) override;
 
     /** Returns the geometry converted to the more generic curve type QgsMultiSurfaceV2
     @return the converted geometry. Caller takes ownership*/
     QgsAbstractGeometryV2* toCurveType() const override;
 
+    virtual QgsAbstractGeometryV2* boundary() const override;
+
   protected:
 
     virtual bool wktOmitChildType() const override { return true; }

src/core/geometry/qgsmultisurfacev2.cpp

@@ -21,6 +21,7 @@ email                : marco.hugentobler at sourcepole dot com
 #include "qgslinestringv2.h"
 #include "qgspolygonv2.h"
 #include "qgscurvepolygonv2.h"
+#include "qgsmulticurvev2.h"
 
 QgsMultiSurfaceV2::QgsMultiSurfaceV2()
     : QgsGeometryCollectionV2()
@@ -132,3 +133,21 @@ bool QgsMultiSurfaceV2::addGeometry( QgsAbstractGeometryV2* g )
   setZMTypeFromSubGeometry( g, QgsWKBTypes::MultiSurface );
   return QgsGeometryCollectionV2::addGeometry( g );
 }
+
+QgsAbstractGeometryV2* QgsMultiSurfaceV2::boundary() const
+{
+  QgsMultiCurveV2* multiCurve = new QgsMultiCurveV2();
+  for ( int i = 0; i < mGeometries.size(); ++i )
+  {
+    if ( QgsSurfaceV2* surface = dynamic_cast<QgsSurfaceV2*>( mGeometries.at( i ) ) )
+    {
+      multiCurve->addGeometry( surface->boundary() );
+    }
+  }
+  if ( multiCurve->numGeometries() == 0 )
+  {
+    delete multiCurve;
+    return nullptr;
+  }
+  return multiCurve;
+}

src/core/geometry/qgsmultisurfacev2.h

@@ -43,6 +43,8 @@ class CORE_EXPORT QgsMultiSurfaceV2: public QgsGeometryCollectionV2
 
     /** Adds a geometry and takes ownership. Returns true in case of success*/
     virtual bool addGeometry( QgsAbstractGeometryV2* g ) override;
+
+    virtual QgsAbstractGeometryV2* boundary() const override;
 };
 
 #endif // QGSMULTISURFACEV2_H

src/core/geometry/qgspointv2.cpp

@@ -281,6 +281,11 @@ QgsCoordinateSequenceV2 QgsPointV2::coordinateSequence() const
   return cs;
 }
 
+QgsAbstractGeometryV2* QgsPointV2::boundary() const
+{
+  return nullptr;
+}
+
 /***************************************************************************
  * This class is considered CRITICAL and any change MUST be accompanied with
  * full unit tests.