In Vertex editing, when doing a mousedown to choose which geometry to

edit, the closest geometry will be selected (not just the first within
snapping range), 

AND then the closest vertex *on that geometry* will be
selected.  

This disambiguates between the same vertex shared amongst
multiple geometries.


git-svn-id: http://svn.osgeo.org/qgis/trunk@5550 c8812cc2-4d05-0410-92ff-de0c093fc19c

src/core/qgsgeometry.cpp

@@ -1316,6 +1316,30 @@ bool QgsGeometry::vertexAt(double &x, double &y,
 }
 
 
+double QgsGeometry::sqrDistToVertexAt(QgsPoint& point,
+                                      QgsGeometryVertexIndex& atVertex) const
+{
+  double x;
+  double y;
+
+  if (vertexAt(x, y, atVertex))
+  {
+#ifdef QGISDEBUG
+    std::cout << "QgsGeometry::sqrDistToVertexAt: Exiting with distance to " << x << " " << y << "." << std::endl;
+#endif
+    return point.sqrDist(x, y);
+  }
+  else
+  {
+#ifdef QGISDEBUG
+    std::cout << "QgsGeometry::sqrDistToVertexAt: Exiting with std::numeric_limits<double>::max()." << std::endl;
+#endif
+    // probably safest to bail out with a very large number
+    return std::numeric_limits<double>::max();
+  }
+}
+
+
 QgsPoint QgsGeometry::closestVertexWithContext(QgsPoint& point,
                                                QgsGeometryVertexIndex& atVertex,
                                                double& sqrDist)

src/core/qgsgeometry.h

@@ -133,6 +133,15 @@ class QgsGeometry {
      */
     bool vertexAt(double &x, double &y, QgsGeometryVertexIndex atVertex) const;
 
+    /**
+        Returns the squared cartesian distance between the given point
+        to the given vertex index (vertex at the given position number,
+        ring and item (first number is index 0))
+
+     */
+    double sqrDistToVertexAt(QgsPoint& point,
+                             QgsGeometryVertexIndex& atVertex) const;
+
     /**
         Returns, in atVertex, the closest vertex in this geometry to the given point.
         The squared cartesian distance is also returned in sqrDist.

src/gui/qgsmaptoolvertexedit.cpp

@@ -101,8 +101,9 @@ void QgsMapToolVertexEdit::canvasPressEvent(QMouseEvent * e)
     //Find nearest segment of the selected line, move that node to the mouse location
     if (!snapSegmentWithContext(point))
       {
-	QMessageBox::warning(0, "Error", "Could not snap vertex. Have you set the tolerance?",
-                         QMessageBox::Ok, Qt::NoButton);
+	QMessageBox::warning(0, "Error", 
+          QObject::tr("Could not snap segment. Have you set the tolerance in Settings > Project Properties > General?"),
+          QMessageBox::Ok, Qt::NoButton);
 	return;
       }
 
@@ -130,15 +131,32 @@ void QgsMapToolVertexEdit::canvasPressEvent(QMouseEvent * e)
 #endif
 
     // Find the closest line segment to the mouse position
-    // Then set up the rubber band to its endpoints
+    // Then find the closest vertex on that line segment
+    // Then set up the rubber band to its adjoining vertexes
 
-    //Find nearest segment of the selected line, move that node to the mouse location    
-    if (!snapVertexWithContext(point))
-      {
-	QMessageBox::warning(0, "Error", "Could not snap vertex. Have you set the tolerance?",
-                         QMessageBox::Ok, Qt::NoButton);
-	return;
-      }
+    QgsPoint snapPoint;
+
+    snapPoint = point;
+    if (!snapSegmentWithContext(snapPoint))
+    {
+      QMessageBox::warning(0, "Error", 
+        QObject::tr("Could not snap segment. Have you set the tolerance in Settings > Project Properties > General?"),
+      QMessageBox::Ok, Qt::NoButton);
+      return;
+    }
+
+    snapPoint = point;
+    if (!snapVertexOfSnappedSegment(snapPoint))
+    {
+      QMessageBox::warning(0, "Error", 
+        QObject::tr("Could not snap vertex. Have you set the tolerance in Settings > Project Properties > General?"),
+      QMessageBox::Ok, Qt::NoButton);
+      return;
+    }
+
+#ifdef QGISDEBUG
+    qWarning("Creating rubber band for moveVertex");
+#endif
 
     index = mSnappedAtVertex;
     createRubberBand();
@@ -178,8 +196,9 @@ void QgsMapToolVertexEdit::canvasPressEvent(QMouseEvent * e)
     // TODO: Find nearest segment of the selected line, move that node to the mouse location
     if (!snapVertexWithContext(point))
       {
-	QMessageBox::warning(0, "Error", "Could not snap vertex. Have you set the tolerance?",
-                         QMessageBox::Ok, Qt::NoButton);
+	QMessageBox::warning(0, "Error", 
+          QObject::tr("Could not snap vertex. Have you set the tolerance in Settings > Project Properties > General?"),
+          QMessageBox::Ok, Qt::NoButton);
 	return;
       }
 
@@ -216,14 +235,15 @@ bool QgsMapToolVertexEdit::snapSegmentWithContext(QgsPoint& point)
   if (!vlayer->snapSegmentWithContext(point, beforeVertex, atFeatureId, atGeometry, tolerance()))
   {
     mSnappedAtFeatureId = -1;
-    QMessageBox::warning(0, "Error", "Could not snap segment. Have you set the tolerance?",
-                         QMessageBox::Ok, Qt::NoButton);
+    QMessageBox::warning(0, "Error",
+      QObject::tr("Could not snap segment. Have you set the tolerance in Settings > Project Properties > General?"),
+      QMessageBox::Ok, Qt::NoButton);
     return FALSE;
   }
   else
   {
 #ifdef QGISDEBUG
-      std::cout << "QgsMapToolVertexEdit: Snapped to segment fid " << atFeatureId << "." << std::endl;
+      std::cout << "QgsMapToolVertexEdit::snapSegmentWithContext: Snapped to segment fid " << atFeatureId << "." << std::endl;
 #endif
 
     // Save where we snapped to
@@ -266,6 +286,50 @@ bool QgsMapToolVertexEdit::snapVertexWithContext(QgsPoint& point)
   }
 }
 
+bool QgsMapToolVertexEdit::snapVertexOfSnappedSegment(QgsPoint& point)
+{
+  double twoBeforeVertexSqrDist;
+  double    beforeVertexSqrDist;
+
+  // Set up the "other side" of the snapped-to segment
+  QgsGeometryVertexIndex snappedTwoBeforeVertex(mSnappedBeforeVertex);
+  snappedTwoBeforeVertex.decrement_back();
+
+#ifdef QGISDEBUG
+  std::cout << "QgsMapToolVertexEdit::snapVertexOfSnappedSegment: Choice of "
+            << snappedTwoBeforeVertex.toString().toLocal8Bit().data() << " or " 
+            << mSnappedBeforeVertex.toString().toLocal8Bit().data() << "." << std::endl;
+#endif
+
+
+  twoBeforeVertexSqrDist = mSnappedAtGeometry.sqrDistToVertexAt(point, snappedTwoBeforeVertex);
+  beforeVertexSqrDist    = mSnappedAtGeometry.sqrDistToVertexAt(point, mSnappedBeforeVertex);
+
+#ifdef QGISDEBUG
+  std::cout << "QgsMapToolVertexEdit::snapVertexOfSnappedSegment: Choice of "
+            << twoBeforeVertexSqrDist << " or " 
+            << beforeVertexSqrDist << "." << std::endl;
+#endif
+
+
+  // See which of the two verticies is closer (i.e. smaller squared distance)
+  if (twoBeforeVertexSqrDist < beforeVertexSqrDist)
+  {
+    mSnappedAtVertex = snappedTwoBeforeVertex;
+  }
+  else
+  {
+    mSnappedAtVertex = mSnappedBeforeVertex;
+  }
+
+#ifdef QGISDEBUG
+  std::cout << "QgsMapToolVertexEdit::snapVertexOfSnappedSegment: Chose "
+            << mSnappedAtVertex.toString().toLocal8Bit().data() << "." << std::endl;
+#endif
+
+  return TRUE;
+}
+
 bool QgsMapToolVertexEdit::snapVertex(QgsPoint& point, int exclFeatureId, int exclVertexNr)
 {
   QgsVectorLayer* vlayer = dynamic_cast<QgsVectorLayer*>(mCanvas->currentLayer());

src/gui/qgsmaptoolvertexedit.h

@@ -69,12 +69,27 @@ class QgsMapToolVertexEdit : public QgsMapTool
     /**Searches the closest point within the project tolerance and setx  mSnappedAtFeatureId and mSnappedAtVertex*/
     bool snapVertexWithContext(QgsPoint& point);
 
+    /** Searches the closest vertex of "geometry" to the given "point" 
+
+        This is useful when selecting a vertex to move, as the selection process is a two step process:
+
+        1. Select the closest line segment to the mouse pointer.
+             - snapSegmentWithContext()
+        2. Select the closest vertex on (1).
+             - snapVertexOfSnappedSegement()
+
+        Step 1 is needed to disambiguate between two geometries sharing the same vertex.
+     */
+    bool snapVertexOfSnappedSegment(QgsPoint& point);
+
     /**Snaps a point (without setting mSnappedAtFeatureId and mSnappedAtVertex). Does not snap to the specified vertex,
      because during dragging, a vertex should not be snapped to itself*/
     bool snapVertex(QgsPoint& point, int exclFeatureId, int exclVertexNr);
-
+
+
     bool snapSegmentWithContext(QgsPoint& point);
-
+
+
     //! The snapped-to segment before this vertex number (identifying the vertex that is being moved)
     QgsGeometryVertexIndex mSnappedAtVertex;
 

src/gui/qgsvectorlayer.cpp

@@ -2990,8 +2990,6 @@ QgsGeometry& snappedGeometry, double tolerance)
       snappedFeatureId  = feature->featureId();
       snappedGeometry   = *(feature->geometry());
       segmentFound = true;
-      delete feature;
-      return true;
     }
     delete feature;
   }
@@ -3018,7 +3016,6 @@ QgsGeometry& snappedGeometry, double tolerance)
       snappedFeatureId  =   (*iter)->featureId();
       snappedGeometry   = *((*iter)->geometry());
       segmentFound = true;
-      return true;
     }
   }
 
@@ -3034,10 +3031,10 @@ QgsGeometry& snappedGeometry, double tolerance)
 	  snappedFeatureId  = it->first;
 	  snappedGeometry   = it->second;
 	  segmentFound = true;
-	  return true;
 	}
     }
-  return false;
+
+  return segmentFound;
 }
 
 

src/gui/qgsvectorlayer.h

@@ -380,7 +380,8 @@ public slots:
      If there is no point within this tolerance, point is left unchanged.
      @param tolerance   The snapping tolerance
      @return true if the position of point has been changed, and false otherwise */
-  bool snapPoint(QgsPoint& point, double tolerance);
+  bool snapPoint(QgsPoint& point,
+                 double tolerance);
 
   /**Snaps a point to the closest vertex if there is one within the snapping tolerance
      @param atVertex          Set to a vertex index of the snapped-to vertex
@@ -401,7 +402,7 @@ public slots:
                              QgsGeometry& snappedGeometry,
                              double tolerance);
 
-  /**Snaps a point to the closest line segment if there is one within the snapping tolerance (mSnappingTolerance)
+  /**Snaps a point to the closest line segment if there is one within the snapping tolerance ("tolerance")
      @param beforeVertex      Set to a value where the snapped-to segment is before this vertex index
      @param snappedFeatureId  Set to the feature ID that where the snapped-to segment belongs to.
      @param snappedGeometry   Set to the geometry that the snapped-to segment belongs to.