Optimize simple marker rendering perfomance

expression( "..." ) call create QString object at every invocation. For
layers with simple markers this overhead take upto 10% of rendering time.

Move expression finding to startRender() method.

Signed-off-by: Yauhen Kharuzhy <jekhor@gmail.com>

Author: jekhor

src/core/symbology-ng/qgsmarkersymbollayerv2.cpp

@@ -46,6 +46,8 @@ QgsSimpleMarkerSymbolLayerV2::QgsSimpleMarkerSymbolLayerV2( QString name, QColor
   mScaleMethod = scaleMethod;
   mSizeUnit = QgsSymbolV2::MM;
   mOffsetUnit = QgsSymbolV2::MM;
+  mAngleExpression = NULL;
+  mNameExpression = NULL;
 }
 
 QgsSymbolLayerV2* QgsSimpleMarkerSymbolLayerV2::create( const QgsStringMap& props )
@@ -231,6 +233,10 @@ void QgsSimpleMarkerSymbolLayerV2::startRender( QgsSymbolV2RenderContext& contex
   }
 
   prepareExpressions( context.layer(), context.renderContext().rendererScale() );
+  mAngleExpression = expression( "angle" );
+  mNameExpression = expression( "name" );
+
+  QgsMarkerSymbolLayerV2::startRender( context );
 }
 
 
@@ -456,19 +462,17 @@ void QgsSimpleMarkerSymbolLayerV2::renderPoint( const QPointF& point, QgsSymbolV
 
   //angle
   double angle = mAngle;
-  QgsExpression* angleExpression = expression( "angle" );
-  if ( angleExpression )
+  if ( mAngleExpression )
   {
-    angle = angleExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toDouble();
+    angle = mAngleExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toDouble();
   }
   if ( angle )
     off = _rotatedOffset( off, angle );
 
   //data defined shape?
-  QgsExpression* nameExpression = expression( "name" );
-  if ( nameExpression )
+  if ( mNameExpression )
   {
-    QString name = nameExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString();
+    QString name = mNameExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString();
     if ( !prepareShape( name ) ) // drawing as a polygon
     {
       preparePath( name ); // drawing as a painter path
@@ -517,7 +521,7 @@ void QgsSimpleMarkerSymbolLayerV2::renderPoint( const QPointF& point, QgsSymbolV
       transform.scale( half, half );
     }
 
-    bool hasDataDefinedRotation = context.renderHints() & QgsSymbolV2::DataDefinedRotation || angleExpression;
+    bool hasDataDefinedRotation = context.renderHints() & QgsSymbolV2::DataDefinedRotation || mAngleExpression;
     if ( angle != 0 && hasDataDefinedRotation )
       transform.rotate( angle );
 

src/core/symbology-ng/qgsmarkersymbollayerv2.h

@@ -105,6 +105,10 @@ class CORE_EXPORT QgsSimpleMarkerSymbolLayerV2 : public QgsMarkerSymbolLayerV2
 
     //Maximum width/height of cache image
     static const int mMaximumCacheWidth = 3000;
+
+  private:
+    QgsExpression *mAngleExpression;
+    QgsExpression *mNameExpression;
 };
 
 //////////

src/core/symbology-ng/qgssymbollayerv2.cpp

@@ -173,6 +173,9 @@ QgsMarkerSymbolLayerV2::QgsMarkerSymbolLayerV2( bool locked )
     : QgsSymbolLayerV2( QgsSymbolV2::Marker, locked ), mSizeUnit( QgsSymbolV2::MM ),  mOffsetUnit( QgsSymbolV2::MM ),
     mHorizontalAnchorPoint( HCenter ), mVerticalAnchorPoint( VCenter )
 {
+    mOffsetExpression = NULL;
+    mHorizontalAnchorExpression = NULL;
+    mVerticalAnchorExpression = NULL;
 }
 
 QgsLineSymbolLayerV2::QgsLineSymbolLayerV2( bool locked )
@@ -185,6 +188,13 @@ QgsFillSymbolLayerV2::QgsFillSymbolLayerV2( bool locked )
 {
 }
 
+void QgsMarkerSymbolLayerV2::startRender( QgsSymbolV2RenderContext& context )
+{
+  mOffsetExpression = expression( "offset" );
+  mHorizontalAnchorExpression = expression( "horizontal_anchor_point" );
+  mVerticalAnchorExpression = expression( "vertical_anchor_point" );
+}
+
 void QgsMarkerSymbolLayerV2::drawPreviewIcon( QgsSymbolV2RenderContext& context, QSize size )
 {
   startRender( context );
@@ -210,10 +220,9 @@ void QgsMarkerSymbolLayerV2::markerOffset( const QgsSymbolV2RenderContext& conte
   offsetX = mOffset.x();
   offsetY = mOffset.y();
 
-  QgsExpression* offsetExpression = expression( "offset" );
-  if ( offsetExpression )
+  if ( mOffsetExpression )
   {
-    QPointF offset = QgsSymbolLayerV2Utils::decodePoint( offsetExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString() );
+    QPointF offset = QgsSymbolLayerV2Utils::decodePoint( mOffsetExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString() );
     offsetX = offset.x();
     offsetY = offset.y();
   }
@@ -223,15 +232,13 @@ void QgsMarkerSymbolLayerV2::markerOffset( const QgsSymbolV2RenderContext& conte
 
   HorizontalAnchorPoint horizontalAnchorPoint = mHorizontalAnchorPoint;
   VerticalAnchorPoint verticalAnchorPoint = mVerticalAnchorPoint;
-  QgsExpression* horizontalAnchorExpression = expression( "horizontal_anchor_point" );
-  if ( horizontalAnchorExpression )
+  if ( mHorizontalAnchorExpression )
   {
-    horizontalAnchorPoint = decodeHorizontalAnchorPoint( horizontalAnchorExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString() );
+    horizontalAnchorPoint = decodeHorizontalAnchorPoint( mHorizontalAnchorExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString() );
   }
-  QgsExpression* verticalAnchorExpression = expression( "vertical_anchor_point" );
-  if ( verticalAnchorExpression )
+  if ( mVerticalAnchorExpression )
   {
-    verticalAnchorPoint = decodeVerticalAnchorPoint( verticalAnchorExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString() );
+    verticalAnchorPoint = decodeVerticalAnchorPoint( mVerticalAnchorExpression->evaluate( const_cast<QgsFeature*>( context.feature() ) ).toString() );
   }
 
   //correct horizontal position according to anchor point

src/core/symbology-ng/qgssymbollayerv2.h

@@ -146,6 +146,8 @@ class CORE_EXPORT QgsMarkerSymbolLayerV2 : public QgsSymbolLayerV2
       Bottom
     };
 
+    void startRender( QgsSymbolV2RenderContext& context );
+
     virtual void renderPoint( const QPointF& point, QgsSymbolV2RenderContext& context ) = 0;
 
     void drawPreviewIcon( QgsSymbolV2RenderContext& context, QSize size );
@@ -205,6 +207,10 @@ class CORE_EXPORT QgsMarkerSymbolLayerV2 : public QgsSymbolLayerV2
   private:
     static QgsMarkerSymbolLayerV2::HorizontalAnchorPoint decodeHorizontalAnchorPoint( const QString& str );
     static QgsMarkerSymbolLayerV2::VerticalAnchorPoint decodeVerticalAnchorPoint( const QString& str );
+
+    QgsExpression* mOffsetExpression;
+    QgsExpression* mHorizontalAnchorExpression;
+    QgsExpression* mVerticalAnchorExpression;
 };
 
 class CORE_EXPORT QgsLineSymbolLayerV2 : public QgsSymbolLayerV2