Offset curve tool: convert multiline features in both directions

Author: mhugent

src/app/qgsmaptooloffsetcurve.cpp

@@ -25,7 +25,7 @@
 #include "qgisapp.h"
 
 QgsMapToolOffsetCurve::QgsMapToolOffsetCurve( QgsMapCanvas* canvas ): QgsMapToolEdit( canvas ), mRubberBand( 0 ),
-    mOriginalGeometry( 0 ), mGeometryModified( false ), mDistanceItem( 0 ), mDistanceSpinBox( 0 ), mSnapVertexMarker( 0 ), mForceCopy( false )
+    mOriginalGeometry( 0 ), mGeometryModified( false ), mDistanceItem( 0 ), mDistanceSpinBox( 0 ), mSnapVertexMarker( 0 ), mForceCopy( false ), mMultiPartGeometry( false )
 {
 }
 
@@ -90,6 +90,11 @@ void QgsMapToolOffsetCurve::canvasReleaseEvent( QMouseEvent * e )
     return;
   }
 
+  if ( mMultiPartGeometry )
+  {
+    mModifiedGeometry.convertToMultiType();
+  }
+
   vlayer->beginEditCommand( tr( "Offset curve" ) );
 
   bool editOk;
@@ -218,27 +223,30 @@ QgsGeometry* QgsMapToolOffsetCurve::createOriginGeometry( QgsVectorLayer* vl, co
   {
     return 0;
   }
+  mMultiPartGeometry = false;
+  //assign feature part by vertex number (snap to vertex) or by before vertex number (snap to segment)
+  int partVertexNr = ( sr.snappedVertexNr == -1 ? sr.beforeVertexNr : sr.snappedVertexNr );
 
   if ( vl == currentVectorLayer() && !mForceCopy )
   {
     //don't consider selected geometries, only the snap result
-    return snappedFeature.geometryAndOwnership();
+    return convertToSingleLine( snappedFeature.geometryAndOwnership(), partVertexNr, mMultiPartGeometry );
   }
   else //snapped to a background layer
   {
     //if source layer is polygon / multipolygon, create a linestring from the snapped ring
     if ( vl->geometryType() == QGis::Polygon )
     {
       //make linestring from polygon ring and return this geometry
-      return linestringFromPolygon( snappedFeature.geometry(), sr.snappedVertexNr );
+      return linestringFromPolygon( snappedFeature.geometry(), partVertexNr );
     }
 
 
     //for background layers, try to merge selected entries together if snapped feature is contained in selection
     const QgsFeatureIds& selection = vl->selectedFeaturesIds();
     if ( selection.size() < 1 || !selection.contains( sr.snappedAtGeometry ) )
     {
-      return snappedFeature.geometryAndOwnership();
+      return convertToSingleLine( snappedFeature.geometryAndOwnership(), partVertexNr, mMultiPartGeometry );
     }
     else
     {
@@ -256,7 +264,7 @@ QgsGeometry* QgsMapToolOffsetCurve::createOriginGeometry( QgsVectorLayer* vl, co
       if ( geom->isMultipart() )
       {
         delete geom;
-        return snappedFeature.geometryAndOwnership();
+        return convertToSingleLine( snappedFeature.geometryAndOwnership(), sr.snappedVertexNr, mMultiPartGeometry );
       }
 
       return geom;
@@ -416,3 +424,43 @@ void QgsMapToolOffsetCurve::configureSnapper( QgsSnapper& s )
   s.setSnapLayers( snapLayers );
   s.setSnapMode( QgsSnapper::SnapWithOneResult );
 }
+
+QgsGeometry* QgsMapToolOffsetCurve::convertToSingleLine( QgsGeometry* geom, int vertex, bool& isMulti )
+{
+  if ( !geom )
+  {
+    return 0;
+  }
+
+  isMulti = false;
+  QGis::WkbType geomType = geom->wkbType();
+  if ( geomType == QGis::WKBLineString || geomType == QGis::WKBLineString25D )
+  {
+    return geom;
+  }
+  else if ( geomType == QGis::WKBMultiLineString || geomType == QGis::WKBMultiLineString25D )
+  {
+    //search vertex
+    isMulti = true;
+    int currentVertex = 0;
+    QgsMultiPolyline multiLine = geom->asMultiPolyline();
+    QgsMultiPolyline::const_iterator it = multiLine.constBegin();
+    for ( ; it != multiLine.constEnd(); ++it )
+    {
+      currentVertex += it->size();
+      if ( vertex < currentVertex )
+      {
+        QgsGeometry* g = QgsGeometry::fromPolyline( *it );
+        delete geom;
+        return g;
+      }
+    }
+  }
+  delete geom;
+  return 0;
+}
+
+QgsGeometry* QgsMapToolOffsetCurve::convertToMultiLine( QgsGeometry* geom )
+{
+  return 0;
+}

src/app/qgsmaptooloffsetcurve.h

@@ -61,6 +61,7 @@ class QgsMapToolOffsetCurve: public QgsMapToolEdit
     QgsVertexMarker* mSnapVertexMarker;
     /**Forces geometry copy (no modification of geometry in current layer)*/
     bool mForceCopy;
+    bool mMultiPartGeometry;
 
 
     void deleteRubberBandAndGeometry();
@@ -72,6 +73,10 @@ class QgsMapToolOffsetCurve: public QgsMapToolEdit
     QgsGeometry* linestringFromPolygon( QgsGeometry* featureGeom, int vertex );
     /**Sets snapping with default vertex search tolerance to all layers (to vertex and segment)*/
     void configureSnapper( QgsSnapper& s );
+    /**Returns a single line from a multiline (or does nothing if geometry is already a single line). Deletes the input geometry*/
+    QgsGeometry* convertToSingleLine( QgsGeometry* geom, int vertex, bool& isMulti );
+    /**Converts offset line back to a multiline if necessary*/
+    QgsGeometry* convertToMultiLine( QgsGeometry* geom );
 };
 
 #endif // QGSMAPTOOLOFFSETCURVE_H