Start on implementing contexts for render operations

Author: nyalldawson

python/core/qgsmapsettings.sip

@@ -118,6 +118,19 @@ class QgsMapSettings
     //! Return the calculated scale of the map
     double scale() const;
 
+    /** Sets the expression context. This context is used for all expression evaluation
+     * associated with this map settings.
+     * @see expressionContext()
+     * @note added in QGIS 2.12
+     */
+    void setExpressionContext( const QgsExpressionContext& context );
+
+    /** Gets the expression context. This context should be used for all expression evaluation
+     * associated with this map settings.
+     * @see setExpressionContext()
+     * @note added in QGIS 2.12
+     */
+    const QgsExpressionContext& expressionContext() const;
 
     // -- utility functions --
 

src/core/composer/qgscomposermap.cpp

@@ -232,6 +232,10 @@ QgsMapSettings QgsComposerMap::mapSettings( const QgsRectangle& extent, const QS
     jobMapSettings.setFlag( QgsMapSettings::UseRenderingOptimization, false );
   }
 
+  QgsExpressionContext* context = createExpressionContext();
+  jobMapSettings.setExpressionContext( *context );
+  delete context;
+
   //update $map variable. Use QgsComposerItem's id since that is user-definable
   QgsExpression::setSpecialColumn( "$map", QgsComposerItem::id() );
 

src/core/qgsmapsettings.h

@@ -26,6 +26,7 @@
 #include "qgsmaptopixel.h"
 #include "qgsrectangle.h"
 #include "qgsscalecalculator.h"
+#include "qgsexpressioncontext.h"
 
 class QPainter;
 
@@ -164,6 +165,19 @@ class CORE_EXPORT QgsMapSettings
     //! Return the calculated scale of the map
     double scale() const;
 
+    /** Sets the expression context. This context is used for all expression evaluation
+     * associated with this map settings.
+     * @see expressionContext()
+     * @note added in QGIS 2.12
+     */
+    void setExpressionContext( const QgsExpressionContext& context ) { mExpressionContext = context; }
+
+    /** Gets the expression context. This context should be used for all expression evaluation
+     * associated with this map settings.
+     * @see setExpressionContext()
+     * @note added in QGIS 2.12
+     */
+    const QgsExpressionContext& expressionContext() const { return mExpressionContext; }
 
     // -- utility functions --
 
@@ -240,6 +254,7 @@ class CORE_EXPORT QgsMapSettings
 
     QStringList mLayers;
     QMap<QString, QString> mLayerStyleOverrides;
+    QgsExpressionContext mExpressionContext;
 
     bool mProjectionsEnabled;
     QgsCoordinateReferenceSystem mDestCRS;

src/core/qgsrendercontext.cpp

@@ -56,6 +56,7 @@ QgsRenderContext QgsRenderContext::fromMapSettings( const QgsMapSettings& mapSet
   ctx.setRasterScaleFactor( 1.0 );
   ctx.setScaleFactor( mapSettings.outputDpi() / 25.4 ); // = pixels per mm
   ctx.setRendererScale( mapSettings.scale() );
+  ctx.setExpressionContext( mapSettings.expressionContext() );
 
   //this flag is only for stopping during the current rendering progress,
   //so must be false at every new render operation

src/core/qgsrendercontext.h

@@ -24,6 +24,7 @@
 #include "qgsmaptopixel.h"
 #include "qgsrectangle.h"
 #include "qgsvectorsimplifymethod.h"
+#include "qgsexpressioncontext.h"
 
 class QPainter;
 
@@ -118,6 +119,27 @@ class CORE_EXPORT QgsRenderContext
     const QgsVectorSimplifyMethod& vectorSimplifyMethod() const { return mVectorSimplifyMethod; }
     void setVectorSimplifyMethod( const QgsVectorSimplifyMethod& simplifyMethod ) { mVectorSimplifyMethod = simplifyMethod; }
 
+    /** Sets the expression context. This context is used for all expression evaluation
+     * associated with this render context.
+     * @see expressionContext()
+     * @note added in QGIS 2.12
+     */
+    void setExpressionContext( const QgsExpressionContext& context ) { mExpressionContext = context; }
+
+    /** Gets the expression context. This context should be used for all expression evaluation
+     * associated with this render context.
+     * @see setExpressionContext()
+     * @note added in QGIS 2.12
+     */
+    QgsExpressionContext& expressionContext() { return mExpressionContext; }
+
+    /** Gets the expression context (const version). This context should be used for all expression evaluation
+     * associated with this render context.
+     * @see setExpressionContext()
+     * @note added in QGIS 2.12
+     */
+    const QgsExpressionContext& expressionContext() const { return mExpressionContext; }
+
   private:
 
     /** Painter for rendering operations*/
@@ -165,6 +187,9 @@ class CORE_EXPORT QgsRenderContext
 
     /** Simplification object which holds the information about how to simplify the features for fast rendering */
     QgsVectorSimplifyMethod mVectorSimplifyMethod;
+
+    /** Expression context */
+    QgsExpressionContext mExpressionContext;
 };
 
 #endif

src/core/qgsvectorlayerrenderer.cpp

@@ -92,6 +92,8 @@ QgsVectorLayerRenderer::QgsVectorLayerRenderer( QgsVectorLayer* layer, QgsRender
     mRendererV2->setVertexMarkerAppearance( mVertexMarkerStyle, mVertexMarkerSize );
   }
 
+  mContext.expressionContext() << QgsExpressionContextUtils::layerScope( layer );
+
   mAttrNames = mRendererV2->usedAttributes();
 
   //register label and diagram layer to the labeling engine
@@ -280,6 +282,8 @@ void QgsVectorLayerRenderer::drawRendererV2( QgsFeatureIterator& fit )
         break;
       }
 
+      mContext.expressionContext().setFeature( fet );
+
       bool sel = mContext.showSelection() && mSelectedFeatureIds.contains( fet.id() );
       bool drawMarker = ( mDrawVertexMarkers && mContext.drawEditingInformation() && ( !mVertexMarkerOnlyForSelection || sel ) );
 
@@ -364,6 +368,7 @@ void QgsVectorLayerRenderer::drawRendererV2Levels( QgsFeatureIterator& fit )
 
     if ( mContext.labelingEngine() )
     {
+      mContext.expressionContext().setFeature( fet );
       if ( mLabeling )
       {
         mContext.labelingEngine()->registerFeature( mLayerID, fet, mContext );
@@ -420,6 +425,8 @@ void QgsVectorLayerRenderer::drawRendererV2Levels( QgsFeatureIterator& fit )
         // maybe vertex markers should be drawn only during the last pass...
         bool drawMarker = ( mDrawVertexMarkers && mContext.drawEditingInformation() && ( !mVertexMarkerOnlyForSelection || sel ) );
 
+        mContext.expressionContext().setFeature( *fit );
+
         try
         {
           mRendererV2->renderFeature( *fit, mContext, layer, sel, drawMarker );