#9480: New option for CentroidFillSymbolLayerV2 to force centroid inside of polygons

src/core/symbology-ng/qgsfillsymbollayerv2.cpp

@@ -3166,7 +3166,7 @@ QSet<QString> QgsPointPatternFillSymbolLayer::usedAttributes() const
 //////////////
 
 
-QgsCentroidFillSymbolLayerV2::QgsCentroidFillSymbolLayerV2(): mMarker( NULL )
+QgsCentroidFillSymbolLayerV2::QgsCentroidFillSymbolLayerV2(): mMarker( NULL ), mPointOnSurface( false )
 {
   setSubSymbol( new QgsMarkerSymbolV2() );
 }
@@ -3178,8 +3178,12 @@ QgsCentroidFillSymbolLayerV2::~QgsCentroidFillSymbolLayerV2()
 
 QgsSymbolLayerV2* QgsCentroidFillSymbolLayerV2::create( const QgsStringMap& properties )
 {
-  Q_UNUSED( properties );
-  return new QgsCentroidFillSymbolLayerV2();
+  QgsCentroidFillSymbolLayerV2* sl = new QgsCentroidFillSymbolLayerV2();
+
+  if ( properties.contains( "point_on_surface" ) )
+    sl->setPointOnSurface( properties["point_on_surface"].toInt() != 0 );
+
+  return sl;
 }
 
 QString QgsCentroidFillSymbolLayerV2::layerType() const
@@ -3208,13 +3212,15 @@ void QgsCentroidFillSymbolLayerV2::renderPolygon( const QPolygonF& points, QList
 {
   Q_UNUSED( rings );
 
-  QPointF centroid = QgsSymbolLayerV2Utils::polygonCentroid( points );
+  QPointF centroid = mPointOnSurface ? QgsSymbolLayerV2Utils::polygonPointOnSurface( points ) : QgsSymbolLayerV2Utils::polygonCentroid( points );
   mMarker->renderPoint( centroid, context.feature(), context.renderContext(), -1, context.selected() );
 }
 
 QgsStringMap QgsCentroidFillSymbolLayerV2::properties() const
 {
-  return QgsStringMap();
+  QgsStringMap map;
+  map["point_on_surface"] = QString::number( mPointOnSurface );
+  return map;
 }
 
 QgsSymbolLayerV2* QgsCentroidFillSymbolLayerV2::clone() const
@@ -3223,6 +3229,7 @@ QgsSymbolLayerV2* QgsCentroidFillSymbolLayerV2::clone() const
   x->mAngle = mAngle;
   x->mColor = mColor;
   x->setSubSymbol( mMarker->clone() );
+  x->setPointOnSurface( mPointOnSurface );
   return x;
 }
 
@@ -3246,9 +3253,9 @@ QgsSymbolLayerV2* QgsCentroidFillSymbolLayerV2::createFromSld( QDomElement &elem
   layers.append( l );
   QgsMarkerSymbolV2 *marker = new QgsMarkerSymbolV2( layers );
 
-  QgsCentroidFillSymbolLayerV2* x = new QgsCentroidFillSymbolLayerV2();
-  x->setSubSymbol( marker );
-  return x;
+  QgsCentroidFillSymbolLayerV2* sl = new QgsCentroidFillSymbolLayerV2();
+  sl->setSubSymbol( marker );
+  return sl;
 }
 
 

src/core/symbology-ng/qgsfillsymbollayerv2.h

@@ -904,8 +904,12 @@ class CORE_EXPORT QgsCentroidFillSymbolLayerV2 : public QgsFillSymbolLayerV2
 
     virtual QSet<QString> usedAttributes() const;
 
+    void setPointOnSurface( bool pointOnSurface ) { mPointOnSurface = pointOnSurface; }
+    bool pointOnSurface() const { return mPointOnSurface; }
+
   protected:
     QgsMarkerSymbolV2* mMarker;
+    bool mPointOnSurface;
 };
 
 #endif

src/core/symbology-ng/qgssymbollayerv2utils.cpp

@@ -3179,6 +3179,62 @@ QPointF QgsSymbolLayerV2Utils::polygonCentroid( const QPolygonF& points )
   return QPointF( cx, cy );
 }
 
+QPointF QgsSymbolLayerV2Utils::polygonPointOnSurface( const QPolygonF& points )
+{
+  QPointF centroid = QgsSymbolLayerV2Utils::polygonCentroid( points );
+
+  // check if centroid inside in polygon
+  if ( !QgsSymbolLayerV2Utils::pointInPolygon( points, centroid ) )
+  {
+    unsigned int i, pointCount = points.count();
+
+    QgsPolyline polyline( pointCount );
+    for ( i = 0; i < pointCount; ++i ) polyline[i] = QgsPoint( points[i].x(), points[i].y() );
+
+    QgsGeometry* geom = QgsGeometry::fromPolygon( QgsPolygon() << polyline );
+    if ( geom )
+    {
+      QgsGeometry* pointOnSurfaceGeom = geom->pointOnSurface();
+
+      if ( pointOnSurfaceGeom )
+      {
+        QgsPoint point = pointOnSurfaceGeom->asPoint();
+        delete pointOnSurfaceGeom;
+        delete geom;
+
+        return QPointF( point.x(), point.y() );
+      }
+      delete geom;
+    }
+  }
+  return centroid;
+}
+
+bool QgsSymbolLayerV2Utils::pointInPolygon( const QPolygonF &points, const QPointF &point )
+{
+  bool inside = false;
+
+  double x = point.x();
+  double y = point.y();
+
+  for ( int i = 0, j = points.count() - 1; i < points.count(); i++ )
+  {
+    const QPointF& p1 = points[i];
+    const QPointF& p2 = points[j];
+
+    if ( p1.x() == x && p1.y() == y )
+      return true;
+
+    if ( ( p1.y() < y && p2.y() >= y ) || ( p2.y() < y && p1.y() >= y ) )
+    {
+      if ( p1.x() + ( y - p1.y() ) / ( p2.y() - p1.y() )*( p2.x() - p1.x() ) <= x )
+        inside = !inside;
+    }
+
+    j = i;
+  }
+  return inside;
+}
 
 QgsExpression* QgsSymbolLayerV2Utils::fieldOrExpressionToExpression( const QString& fieldOrExpression )
 {

src/core/symbology-ng/qgssymbollayerv2utils.h

@@ -287,6 +287,12 @@ class CORE_EXPORT QgsSymbolLayerV2Utils
     //! Calculate the centroid point of a QPolygonF
     static QPointF polygonCentroid( const QPolygonF& points );
 
+    //! Calculate a point within of a QPolygonF
+    static QPointF polygonPointOnSurface( const QPolygonF& points );
+
+    //! Calculate whether a point is within of a QPolygonF
+    static bool pointInPolygon( const QPolygonF &points, const QPointF &point );
+
     /** Return a new valid expression instance for given field or expression string.
      * If the input is not a valid expression, it is assumed that it is a field name and gets properly quoted.
      * If the string is empty, returns null pointer.

src/gui/symbology-ng/qgssymbollayerv2widget.cpp

@@ -2794,6 +2794,11 @@ void QgsCentroidFillSymbolLayerV2Widget::setSymbolLayer( QgsSymbolLayerV2* layer
 
   // layer type is correct, we can do the cast
   mLayer = static_cast<QgsCentroidFillSymbolLayerV2*>( layer );
+
+  // set values
+  mDrawInsideCheckBox->blockSignals( true );
+  mDrawInsideCheckBox->setChecked( mLayer->pointOnSurface() );
+  mDrawInsideCheckBox->blockSignals( false );
 }
 
 QgsSymbolLayerV2* QgsCentroidFillSymbolLayerV2Widget::symbolLayer()
@@ -2801,5 +2806,8 @@ QgsSymbolLayerV2* QgsCentroidFillSymbolLayerV2Widget::symbolLayer()
   return mLayer;
 }
 
-
-
+void QgsCentroidFillSymbolLayerV2Widget::on_mDrawInsideCheckBox_stateChanged( int state )
+{
+  mLayer->setPointOnSurface( state == Qt::Checked );
+  emit changed();
+}

src/gui/symbology-ng/qgssymbollayerv2widget.h

@@ -482,6 +482,9 @@ class GUI_EXPORT QgsCentroidFillSymbolLayerV2Widget : public QgsSymbolLayerV2Wid
     virtual void setSymbolLayer( QgsSymbolLayerV2* layer );
     virtual QgsSymbolLayerV2* symbolLayer();
 
+  public slots:
+    void on_mDrawInsideCheckBox_stateChanged( int state );
+
   protected:
     QgsCentroidFillSymbolLayerV2* mLayer;
 };

src/ui/symbollayer/widget_centroidfill.ui

@@ -16,6 +16,13 @@
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout">
+     <item>
+      <widget class="QCheckBox" name="mDrawInsideCheckBox">
+       <property name="text">
+        <string>Force point inside polygon</string>
+       </property>
+      </widget>
+     </item>
      <item>
       <spacer>
        <property name="orientation">