GEOMETRY: fix regression on split multipart

Fix #54155
qgis · Sep 29, 2023 · b235eee · b235eee
1 parent 8a3ee8a
commit b235eee
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Showing 3 changed files with 41 additions and 12 deletions.
diff --git a/src/core/geometry/qgsgeos.cpp b/src/core/geometry/qgsgeos.cpp
@@ -1042,12 +1042,12 @@ geos::unique_ptr QgsGeos::linePointDifference( GEOSGeometry *GEOSsplitPoint ) co
   QgsMultiCurve lines;
 
   //For each part
-  for ( int i = 0; i < multiCurve->numGeometries(); ++i )
+  for ( int geometryIndex = 0; geometryIndex < multiCurve->numGeometries(); ++geometryIndex )
   {
-    const QgsLineString *line = qgsgeometry_cast<const QgsLineString *>( multiCurve->geometryN( i ) );
+    const QgsLineString *line = qgsgeometry_cast<const QgsLineString *>( multiCurve->geometryN( geometryIndex ) );
     if ( !line )
     {
-      const QgsCurve *curve = qgsgeometry_cast<const QgsCurve *>( multiCurve->geometryN( i ) );
+      const QgsCurve *curve = qgsgeometry_cast<const QgsCurve *>( multiCurve->geometryN( geometryIndex ) );
       line = curve->curveToLine();
     }
     if ( !line )
@@ -1056,14 +1056,23 @@ geos::unique_ptr QgsGeos::linePointDifference( GEOSGeometry *GEOSsplitPoint ) co
     }
     // we gather the intersection points and their distance from previous node grouped by segment
     QMap< int, QVector< QPair< double, QgsPoint > > >pointMap;
-    for ( int p = 0; p < splitPoints->numGeometries(); ++p )
+    for ( int splitPointIndex = 0; splitPointIndex < splitPoints->numGeometries(); ++splitPointIndex )
     {
-      const QgsPoint *intersectionPoint = splitPoints->pointN( p );
+      const QgsPoint *intersectionPoint = splitPoints->pointN( splitPointIndex );
+
       QgsPoint segmentPoint2D;
       QgsVertexId nextVertex;
       // With closestSegment we only get a 2D point so we need to interpolate if we
       // don't want to lose Z data
       line->closestSegment( *intersectionPoint, segmentPoint2D, nextVertex );
+
+      // The intersection might belong to another part, skip it
+      // Note: cannot test for equality because of Z
+      if ( intersectionPoint->x() != segmentPoint2D.x() || intersectionPoint->y() != segmentPoint2D.y() )
+      {
+        continue;
+      }
+
       const QgsLineString segment = QgsLineString( line->pointN( nextVertex.vertex - 1 ), line->pointN( nextVertex.vertex ) );
       const double distance = segmentPoint2D.distance( line->pointN( nextVertex.vertex - 1 ) );
 
@@ -1089,25 +1098,25 @@ geos::unique_ptr QgsGeos::linePointDifference( GEOSGeometry *GEOSsplitPoint ) co
     QgsLineString newLine;
     int nVertices = line->numPoints();
     QgsPoint splitPoint;
-    for ( int j = 0; j < nVertices; ++j )
+    for ( int vertexIndex = 0; vertexIndex < nVertices; ++vertexIndex )
     {
-      QgsPoint currentPoint = line->pointN( j );
+      QgsPoint currentPoint = line->pointN( vertexIndex );
       newLine.addVertex( currentPoint );
-      if ( pointMap.contains( j ) )
+      if ( pointMap.contains( vertexIndex ) )
       {
         // For each intersecting point
-        for ( int k = 0; k < pointMap[ j ].size(); ++k )
+        for ( int k = 0; k < pointMap[ vertexIndex ].size(); ++k )
         {
-          splitPoint = pointMap[ j ][k].second;
+          splitPoint = pointMap[ vertexIndex ][k].second;
           if ( splitPoint == currentPoint )
           {
             lines.addGeometry( newLine.clone() );
             newLine = QgsLineString();
             newLine.addVertex( currentPoint );
           }
-          else if ( splitPoint == line->pointN( j + 1 ) )
+          else if ( splitPoint == line->pointN( vertexIndex + 1 ) )
           {
-            newLine.addVertex( line->pointN( j + 1 ) );
+            newLine.addVertex( line->pointN( vertexIndex + 1 ) );
             lines.addGeometry( newLine.clone() );
             newLine = QgsLineString();
           }

diff --git a/tests/src/core/geometry/testqgsgeometry.cpp b/tests/src/core/geometry/testqgsgeometry.cpp
@@ -2403,6 +2403,16 @@ void TestQgsGeometry::splitGeometry()
   QCOMPARE( g2.splitGeometry( QgsPointSequence() << QgsPoint( -63290.25259721936890855, -79165.28533450335089583 ) << QgsPoint( -63290.25259721936890855, -79160.28533450335089583 ), newGeoms, false, testPoints ), Qgis::GeometryOperationResult::Success );
   QCOMPARE( newGeoms.count(), 1 );
   QCOMPARE( newGeoms[0].asWkt( 17 ), QStringLiteral( "LineString (-63290.25259721937618451 -79162.78533450335089583, -63290.25259721936890855 -79162.78533450335089583)" ) );
+
+  // Should not split the first part - https://github.com/qgis/QGIS/issues/54155
+  g2 = QgsGeometry::fromWkt( "MultiLinestring((0 1, 1 0),(0 2, 2 0))" );
+  testPoints.clear();
+  newGeoms.clear();
+  QCOMPARE( g2.splitGeometry( QgsPointSequence() << QgsPoint( 0.8, 0.8 ) << QgsPoint( 1.2, 1.2 ), newGeoms, false, testPoints, false ), Qgis::GeometryOperationResult::Success );
+  QCOMPARE( newGeoms.count(), 3 );
+  QCOMPARE( newGeoms[0].asWkt( 0 ), QStringLiteral( "MultiLineString ((0 2, 1 1))" ) );
+  QCOMPARE( newGeoms[1].asWkt( 0 ), QStringLiteral( "MultiLineString ((1 1, 2 0))" ) );
+  QCOMPARE( newGeoms[2].asWkt( 0 ), QStringLiteral( "MultiLineString ((0 1, 1 0))" ) );
 }
 
 void TestQgsGeometry::snappedToGrid()

diff --git a/tests/src/python/test_qgsgeometry.py b/tests/src/python/test_qgsgeometry.py
@@ -7363,6 +7363,16 @@ def testSplitGeometry(self):
         self.assertGeometriesEqual(square, r2)
         self.assertGeometriesEqual(parts[0], r1)
 
+        multilinestring = QgsGeometry.fromWkt("MultiLinestring((0 1, 1 0),(0 2, 2 0))")
+        blade = QgsCompoundCurve()
+        blade.addCurve(QgsLineString([QgsPointXY(0.8, 0.8), QgsPointXY(1.2, 1.2)]))
+        result, splitted, _ = multilinestring.splitGeometry(blade, False, False, False)
+        self.assertEqual(result, Qgis.GeometryOperationResult.Success)
+        self.assertEqual(len(splitted), 3)
+        self.assertTrue(compareWkt(splitted[0].asWkt(), 'MultiLineString ((0 2, 1 1))'))
+        self.assertTrue(compareWkt(splitted[1].asWkt(), 'MultiLineString ((1 1, 2 0))'))
+        self.assertTrue(compareWkt(splitted[2].asWkt(), 'MultiLineString ((0 1, 1 0))'))
+
 
 if __name__ == '__main__':
     unittest.main()