[FEATURE] Add option for simple line symbols to be drawn only inside a

polygon. Allows for creation of "national geographic" style borders on
maps where a thick border does not overlap into neighbouring polygons.

Author: nyalldawson

python/core/symbology-ng/qgslinesymbollayerv2.sip

@@ -55,6 +55,12 @@ class QgsSimpleLineSymbolLayerV2 : QgsLineSymbolLayerV2
 
     QVector<qreal> customDashVector() const;
     void setCustomDashVector( const QVector<qreal>& vector );
+    
+    //Returns true if the line should only be drawn inside the polygon
+    bool drawInsidePolygon() const;
+    //Set to true if the line should only be drawn inside the polygon
+    void setDrawInsidePolygon( bool drawInsidePolygon );
+    
 };
 
 /////////

python/gui/symbology-ng/qgssymbollayerv2widget.sip

@@ -43,6 +43,7 @@ class QgsSimpleLineSymbolLayerV2Widget : QgsSymbolLayerV2Widget
     void on_mOffsetUnitComboBox_currentIndexChanged( int index );
     void on_mDashPatternUnitComboBox_currentIndexChanged( int index );
     void on_mDataDefinedPropertiesButton_clicked();
+    void on_mDrawInsideCheckBox_stateChanged( int state );
 
   protected:
     //creates a new icon for the 'change pattern' button

src/core/symbology-ng/qgslinesymbollayerv2.cpp

@@ -30,7 +30,7 @@
 
 QgsSimpleLineSymbolLayerV2::QgsSimpleLineSymbolLayerV2( QColor color, double width, Qt::PenStyle penStyle )
     : mPenStyle( penStyle ), mPenJoinStyle( DEFAULT_SIMPLELINE_JOINSTYLE ), mPenCapStyle( DEFAULT_SIMPLELINE_CAPSTYLE ), mOffset( 0 ), mOffsetUnit( QgsSymbolV2::MM ),
-    mUseCustomDashPattern( false ), mCustomDashPatternUnit( QgsSymbolV2::MM )
+    mUseCustomDashPattern( false ), mCustomDashPatternUnit( QgsSymbolV2::MM ), mDrawInsidePolygon( false )
 {
   mColor = color;
   mWidth = width;
@@ -94,6 +94,11 @@ QgsSymbolLayerV2* QgsSimpleLineSymbolLayerV2::create( const QgsStringMap& props
     l->setCustomDashPatternUnit( QgsSymbolLayerV2Utils::decodeOutputUnit( props["customdash_unit"] ) );
   }
 
+  if ( props.contains( "draw_inside_polygon" ) )
+  {
+    l->setDrawInsidePolygon( props["draw_inside_polygon"].toInt() );
+  }
+
   //data defined properties
   if ( props.contains( "color_expression" ) )
     l->setDataDefinedProperty( "color", props["color_expression"] );
@@ -191,6 +196,15 @@ void QgsSimpleLineSymbolLayerV2::renderPolyline( const QPolygonF& points, QgsSym
     return;
   }
 
+  if ( mDrawInsidePolygon )
+  {
+    //only drawing the line on the interior of the polygon, so set clip path for painter
+    p->save();
+    QPainterPath clipPath;
+    clipPath.addPolygon( points );
+    p->setClipPath( clipPath, Qt::IntersectClip );
+  }
+
   if ( offset == 0 )
   {
     p->drawPolyline( points );
@@ -200,6 +214,12 @@ void QgsSimpleLineSymbolLayerV2::renderPolyline( const QPolygonF& points, QgsSym
     double scaledOffset = offset * QgsSymbolLayerV2Utils::lineWidthScaleFactor( context.renderContext(), mOffsetUnit );
     p->drawPolyline( ::offsetLine( points, scaledOffset ) );
   }
+
+  if ( mDrawInsidePolygon )
+  {
+    //restore painter to reset clip path
+    p->restore();
+  }
 }
 
 QgsStringMap QgsSimpleLineSymbolLayerV2::properties() const
@@ -216,6 +236,7 @@ QgsStringMap QgsSimpleLineSymbolLayerV2::properties() const
   map["use_custom_dash"] = ( mUseCustomDashPattern ? "1" : "0" );
   map["customdash"] = QgsSymbolLayerV2Utils::encodeRealVector( mCustomDashVector );
   map["customdash_unit"] = QgsSymbolLayerV2Utils::encodeOutputUnit( mCustomDashPatternUnit );
+  map["draw_inside_polygon"] = ( mDrawInsidePolygon ? "1" : "0" );
   saveDataDefinedProperties( map );
   return map;
 }
@@ -231,6 +252,7 @@ QgsSymbolLayerV2* QgsSimpleLineSymbolLayerV2::clone() const
   l->setPenCapStyle( mPenCapStyle );
   l->setUseCustomDashPattern( mUseCustomDashPattern );
   l->setCustomDashVector( mCustomDashVector );
+  l->setDrawInsidePolygon( mDrawInsidePolygon );
   copyDataDefinedProperties( l );
   return l;
 }
@@ -387,7 +409,15 @@ void QgsSimpleLineSymbolLayerV2::applyDataDefinedSymbology( QgsSymbolV2RenderCon
 
 double QgsSimpleLineSymbolLayerV2::estimateMaxBleed() const
 {
-  return ( mWidth / 2.0 ) + mOffset;
+  if ( mDrawInsidePolygon )
+  {
+    //set to clip line to the interior of polygon, so we expect no bleed
+    return 0;
+  }
+  else
+  {
+    return ( mWidth / 2.0 ) + mOffset;
+  }
 }
 
 QVector<qreal> QgsSimpleLineSymbolLayerV2::dxfCustomDashPattern( QgsSymbolV2::OutputUnit& unit ) const

src/core/symbology-ng/qgslinesymbollayerv2.h

@@ -91,6 +91,11 @@ class CORE_EXPORT QgsSimpleLineSymbolLayerV2 : public QgsLineSymbolLayerV2
     QVector<qreal> customDashVector() const { return mCustomDashVector; }
     void setCustomDashVector( const QVector<qreal>& vector ) { mCustomDashVector = vector; }
 
+    //Returns true if the line should only be drawn inside the polygon
+    bool drawInsidePolygon() const { return mDrawInsidePolygon; }
+    //Set to true if the line should only be drawn inside the polygon
+    void setDrawInsidePolygon( bool drawInsidePolygon ) { mDrawInsidePolygon = drawInsidePolygon; }
+
     QVector<qreal> dxfCustomDashPattern( QgsSymbolV2::OutputUnit& unit ) const;
 
     double dxfWidth( const QgsDxfExport& e, const QgsSymbolV2RenderContext& context ) const;
@@ -112,6 +117,8 @@ class CORE_EXPORT QgsSimpleLineSymbolLayerV2 : public QgsLineSymbolLayerV2
     /**Vector with an even number of entries for the */
     QVector<qreal> mCustomDashVector;
 
+    bool mDrawInsidePolygon;
+
   private:
     //helper functions for data defined symbology
     void applyDataDefinedSymbology( QgsSymbolV2RenderContext& context, QPen& pen, QPen& selPen, double& offset );

src/gui/symbology-ng/qgssymbollayerv2widget.cpp

@@ -52,6 +52,12 @@ QgsSimpleLineSymbolLayerV2Widget::QgsSimpleLineSymbolLayerV2Widget( const QgsVec
 
   setupUi( this );
 
+  if ( vl && vl->geometryType() != QGis::Polygon )
+  {
+    //draw inside polygon checkbox only makes sense for polygon layers
+    mDrawInsideCheckBox->hide();
+  }
+
   connect( spinWidth, SIGNAL( valueChanged( double ) ), this, SLOT( penWidthChanged() ) );
   connect( btnChangeColor, SIGNAL( colorChanged( const QColor& ) ), this, SLOT( colorChanged( const QColor& ) ) );
   connect( cboPenStyle, SIGNAL( currentIndexChanged( int ) ), this, SLOT( penStyleChanged() ) );
@@ -104,6 +110,13 @@ void QgsSimpleLineSymbolLayerV2Widget::setSymbolLayer( QgsSymbolLayerV2* layer )
   mCustomCheckBox->blockSignals( true );
   mCustomCheckBox->setCheckState( useCustomDashPattern ? Qt::Checked : Qt::Unchecked );
   mCustomCheckBox->blockSignals( false );
+
+  //draw inside polygon?
+  bool drawInsidePolygon = mLayer->drawInsidePolygon();
+  mDrawInsideCheckBox->blockSignals( true );
+  mDrawInsideCheckBox->setCheckState( drawInsidePolygon ? Qt::Checked : Qt::Unchecked );
+  mDrawInsideCheckBox->blockSignals( false );
+
   updatePatternIcon();
 }
 
@@ -189,6 +202,13 @@ void QgsSimpleLineSymbolLayerV2Widget::on_mDashPatternUnitComboBox_currentIndexC
   emit changed();
 }
 
+void QgsSimpleLineSymbolLayerV2Widget::on_mDrawInsideCheckBox_stateChanged( int state )
+{
+  bool checked = ( state == Qt::Checked );
+  mLayer->setDrawInsidePolygon( checked );
+  emit changed();
+}
+
 void QgsSimpleLineSymbolLayerV2Widget::on_mDataDefinedPropertiesButton_clicked()
 {
   if ( !mLayer )

src/gui/symbology-ng/qgssymbollayerv2widget.h

@@ -71,6 +71,7 @@ class GUI_EXPORT QgsSimpleLineSymbolLayerV2Widget : public QgsSymbolLayerV2Widge
     void on_mOffsetUnitComboBox_currentIndexChanged( int index );
     void on_mDashPatternUnitComboBox_currentIndexChanged( int index );
     void on_mDataDefinedPropertiesButton_clicked();
+    void on_mDrawInsideCheckBox_stateChanged( int state );
 
   protected:
     QgsSimpleLineSymbolLayerV2* mLayer;

src/ui/symbollayer/widget_simpleline.ui

@@ -23,7 +23,16 @@
    <property name="horizontalSpacing">
     <number>28</number>
    </property>
-   <property name="margin">
+   <property name="leftMargin">
+    <number>1</number>
+   </property>
+   <property name="topMargin">
+    <number>1</number>
+   </property>
+   <property name="rightMargin">
+    <number>1</number>
+   </property>
+   <property name="bottomMargin">
     <number>1</number>
    </property>
    <item row="0" column="0">
@@ -242,7 +251,7 @@
      </item>
     </widget>
    </item>
-   <item row="8" column="0" colspan="2">
+   <item row="11" column="0" colspan="2">
     <widget class="QPushButton" name="mDataDefinedPropertiesButton">
      <property name="sizePolicy">
       <sizepolicy hsizetype="Minimum" vsizetype="Fixed">
@@ -255,6 +264,17 @@
      </property>
     </widget>
    </item>
+   <item row="9" column="0" colspan="2">
+    <layout class="QHBoxLayout" name="horizontalLayout_4">
+     <item>
+      <widget class="QCheckBox" name="mDrawInsideCheckBox">
+       <property name="text">
+        <string>Draw line only inside polygon</string>
+       </property>
+      </widget>
+     </item>
+    </layout>
+   </item>
   </layout>
  </widget>
  <customwidgets>