geometry: allow removing parts and rings or geometries by removing all vertices

(fixes #10684)

Author: jef-n

src/app/nodetool/qgsselectedfeature.cpp

@@ -258,7 +258,7 @@ void QgsSelectedFeature::deleteSelectedVertexes()
   beginGeometryChange();
 
   int count = 0;
-  for ( int i = mVertexMap.size() - 1; i > -1; i-- )
+  for ( int i = mVertexMap.size() - 1; i > -1 && nSelected > 0; i-- )
   {
     if ( mVertexMap[i]->isSelected() )
     {

src/core/qgsgeometry.cpp

@@ -1363,18 +1363,31 @@ bool QgsGeometry::moveVertex( double x, double y, int atVertex )
   }
 }
 
-bool QgsGeometry::deleteVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int atVertex, bool hasZValue, int &pointIndex, bool isRing, bool lastItem )
+// copy vertices from srcPtr to dstPtr and skip/delete one vertex
+// @param srcPtr ring/part starting with number of points (adjusted in each call)
+// @param dstPtr ring/part to copy to (adjusted in each call)
+// @param atVertex index of vertex to skip
+// @param hasZValue points have 3 elements
+// @param pointIndex reference to index of first ring/part vertex in overall object (adjusted in each call)
+// @param isRing srcPtr points to a ring
+// @param lastItem last ring/part, atVertex after this one must be wrong
+// @return
+//   0 no delete was done
+//   1 "normal" delete was done
+//   2 last element of the ring/part was deleted
+int QgsGeometry::deleteVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int atVertex, bool hasZValue, int &pointIndex, bool isRing, bool lastItem )
 {
   QgsDebugMsg( QString( "atVertex:%1 hasZValue:%2 pointIndex:%3 isRing:%4" ).arg( atVertex ).arg( hasZValue ).arg( pointIndex ).arg( isRing ) );
   const int ps = ( hasZValue ? 3 : 2 ) * sizeof( double );
   int nPoints;
   srcPtr >> nPoints;
 
+  // copy complete ring/part if vertex is in a following one
   if ( atVertex < pointIndex || atVertex >= pointIndex + nPoints )
   {
     // atVertex does not exist
     if ( lastItem && atVertex >= pointIndex + nPoints )
-      return false;
+      return 0;
 
     dstPtr << nPoints;
 
@@ -1383,14 +1396,25 @@ bool QgsGeometry::deleteVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int a
     dstPtr += len;
     srcPtr += len;
     pointIndex += nPoints;
-    return false;
+    return 0;
   }
 
+  // delete the first vertex of a ring instead of the last
   if ( isRing && atVertex == pointIndex + nPoints - 1 )
     atVertex = pointIndex;
 
+  if ( nPoints == ( isRing ? 2 : 1 ) )
+  {
+    // last point of the part/ring is deleted
+    // skip the whole part/ring
+    srcPtr += nPoints * ps;
+    pointIndex += nPoints;
+    return 2;
+  }
+
   dstPtr << nPoints - 1;
 
+  // copy ring before vertex
   int len = ( atVertex - pointIndex ) * ps;
   if ( len > 0 )
   {
@@ -1399,9 +1423,13 @@ bool QgsGeometry::deleteVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int a
     srcPtr += len;
   }
 
+  // skip deleted vertex
   srcPtr += ps;
 
+  // copy reset of ring
   len = ( pointIndex + nPoints - atVertex - 1 ) * ps;
+
+  // save position of vertex, if we delete the first vertex of a ring
   const unsigned char *first = 0;
   if ( isRing && atVertex == pointIndex )
   {
@@ -1416,20 +1444,22 @@ bool QgsGeometry::deleteVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int a
     srcPtr += len;
   }
 
+  // copy new first vertex instead of the old last, if we deleted the original first vertex
   if ( first )
   {
     memcpy( dstPtr, first, ps );
     dstPtr += ps;
     srcPtr += ps;
   }
 
-  pointIndex += nPoints - 1;
+  pointIndex += nPoints;
 
-  return true;
+  return 1;
 }
 
 bool QgsGeometry::deleteVertex( int atVertex )
 {
+  QgsDebugMsg( QString( "atVertex:%1" ).arg( atVertex ) );
   if ( atVertex < 0 )
     return false;
 
@@ -1468,7 +1498,14 @@ bool QgsGeometry::deleteVertex( int atVertex )
     case QGis::WKBLineString:
     {
       int pointIndex = 0;
-      deleted = deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, false, true );
+      int res = deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, false, true );
+      if ( res == 2 )
+      {
+        // Linestring with 0 points
+        dstPtr << 0;
+      }
+
+      deleted = res != 0;
       break;
     }
 
@@ -1477,10 +1514,17 @@ bool QgsGeometry::deleteVertex( int atVertex )
     {
       int nRings;
       srcPtr >> nRings;
+      QgsWkbPtr ptrN( dstPtr );
       dstPtr << nRings;
 
       for ( int ringnr = 0, pointIndex = 0; ringnr < nRings; ++ringnr )
-        deleted |= deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, true, ringnr == nRings - 1 );
+      {
+        int res = deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, true, ringnr == nRings - 1 );
+        if ( res == 2 )
+          ptrN << nRings - 1;
+
+        deleted |= res != 0;
+      }
 
       break;
     }
@@ -1524,13 +1568,24 @@ bool QgsGeometry::deleteVertex( int atVertex )
     {
       int nLines;
       srcPtr >> nLines;
+      QgsWkbPtr ptrN( dstPtr );
       dstPtr << nLines;
 
       for ( int linenr = 0, pointIndex = 0; linenr < nLines; ++linenr )
       {
+        QgsWkbPtr saveDstPtr( dstPtr );
         srcPtr >> endianness >> wkbType;
         dstPtr << endianness << wkbType;
-        deleted |= deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, false, linenr == nLines - 1 );
+
+        int res = deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, false, linenr == nLines - 1 );
+        if ( res == 2 )
+        {
+          // line string was completely removed
+          ptrN << nLines - 1;
+          dstPtr = saveDstPtr;
+        }
+
+        deleted |= res != 0;
       }
 
       break;
@@ -1541,16 +1596,38 @@ bool QgsGeometry::deleteVertex( int atVertex )
     {
       int nPolys;
       srcPtr >> nPolys;
+      QgsWkbPtr ptrNPolys( dstPtr );
       dstPtr << nPolys;
 
       for ( int polynr = 0, pointIndex = 0; polynr < nPolys; ++polynr )
       {
         int nRings;
         srcPtr >> endianness >> wkbType >> nRings;
-        dstPtr << endianness << wkbType << nRings;
+        QgsWkbPtr saveDstPolyPtr( dstPtr );
+        dstPtr << endianness << wkbType;
+        QgsWkbPtr ptrNRings( dstPtr );
+        dstPtr << nRings;
 
         for ( int ringnr = 0; ringnr < nRings; ++ringnr )
-          deleted |= deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, true, polynr == nPolys - 1 && ringnr == nRings - 1 );
+        {
+          int res = deleteVertex( srcPtr, dstPtr, atVertex, hasZValue, pointIndex, true, polynr == nPolys - 1 && ringnr == nRings - 1 );
+          if ( res == 2 )
+          {
+            // ring was completely removed
+            if ( nRings == 1 )
+            {
+              // last ring => remove polygon
+              ptrNPolys << nPolys - 1;
+              dstPtr = saveDstPolyPtr;
+            }
+            else
+            {
+              ptrNRings << nRings - 1;
+            }
+          }
+
+          deleted |= res != 0;
+        }
       }
       break;
     }

src/core/qgsgeometry.h

@@ -648,7 +648,7 @@ class CORE_EXPORT QgsGeometry
     double leftOf( double x, double y, double& x1, double& y1, double& x2, double& y2 );
 
     static inline bool moveVertex( QgsWkbPtr &wkbPtr, const double &x, const double &y, int atVertex, bool hasZValue, int &pointIndex, bool isRing );
-    static inline bool deleteVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int atVertex, bool hasZValue, int &pointIndex, bool isRing, bool lastItem );
+    static inline int deleteVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int atVertex, bool hasZValue, int &pointIndex, bool isRing, bool lastItem );
     static inline bool insertVertex( QgsConstWkbPtr &srcPtr, QgsWkbPtr &dstPtr, int beforeVertex, const double &x, const double &y, bool hasZValue, int &pointIndex, bool isRing );
 
     /** try to convert the geometry to a point */

tests/src/python/CMakeLists.txt

@@ -4,7 +4,7 @@ ADD_PYTHON_TEST(PyQgsLocalServer test_qgis_local_server.py)
 ADD_PYTHON_TEST(PyQgsFontUtils test_qgsfontutils.py)
 ADD_PYTHON_TEST(PyQgsFeature test_qgsfeature.py)
 ADD_PYTHON_TEST(PyQgsFeatureIterator test_qgsfeatureiterator.py)
-ADD_PYTHON_TEST(PyQgsGeometry test_qgsgeometry.py)
+ADD_PYTHON_TEST(PyQgsGeometryTest test_qgsgeometry.py)
 ADD_PYTHON_TEST(PyQgsGeometryAvoidIntersections test_qgsgeometry_avoid_intersections.py)
 ADD_PYTHON_TEST(PyQgsVectorLayer test_qgsvectorlayer.py)
 ADD_PYTHON_TEST(PyQgsRasterLayer test_qgsrasterlayer.py)

tests/src/python/test_qgsgeometry.py

@@ -950,6 +950,31 @@ def testDeleteVertex(self):
         wkt = polygon.exportToWkt()
         assert compareWkt( expwkt, wkt ), "Expected:\n%s\nGot:\n%s\n" % (expwkt, wkt )
 
+        # 3-+-+-+-+-+-+-+-+-2
+        # |                 |
+        # + 8-7 3-2 8-7 3-2 +
+        # | | | | | | | | | |
+        # + 5-6 0-1 5-6 0-1 +
+        # |                 |
+        # 0-+-+-+-+---+-+-+-1
+        polygon = QgsGeometry.fromWkt( "POLYGON((0 0,9 0,9 3,0 3,0 0),(1 1,2 1,2 2,1 2,1 1),(3 1,4 1,4 2,3 2,3 1),(5 1,6 1,6 2,5 2,5 1),(7 1,8 1,8 2,7 2,7 1))" )
+        #                                          0   1   2   3   4     5   6   7   8   9    10  11  12  13  14    15  16  17  18  19    20  21  22  23  24
+
+        for i in range(4):
+            assert polygon.deleteVertex(16), "Delete vertex 16 failed" % i
+
+        expwkt = "POLYGON((0 0,9 0,9 3,0 3,0 0),(1 1,2 1,2 2,1 2,1 1),(3 1,4 1,4 2,3 2,3 1),(7 1,8 1,8 2,7 2,7 1))"
+        wkt = polygon.exportToWkt()
+        assert compareWkt( expwkt, wkt ), "Expected:\n%s\nGot:\n%s\n" % (expwkt, wkt )
+
+        for i in range(3):
+            for j in range(4):
+               assert polygon.deleteVertex(5), "Delete vertex 5 failed" % i
+
+        expwkt = "POLYGON((0 0,9 0,9 3,0 3,0 0))"
+        wkt = polygon.exportToWkt()
+        assert compareWkt( expwkt, wkt ), "Expected:\n%s\nGot:\n%s\n" % (expwkt, wkt )
+
     def testInsertVertex(self):
         linestring = QgsGeometry.fromWkt( "LINESTRING(1 0,2 0)" )