Expression variable for the currently rendered part

During rendering, two new variables will be available:

  * `geometry_part_count`
  * `geometry_part_num` (1-based index)

Useful to apply different styles to different parts of multipart
features

python/core/qgsexpressioncontext.sip

@@ -344,6 +344,11 @@ class QgsExpressionContext
      */
     void appendScope( QgsExpressionContextScope* scope /Transfer/ );
 
+    /**
+     * Remove the last scope from the expression context.
+     */
+    void popScope();
+
     /** Appends a scope to the end of the context. This scope will override
      * any matching variables or functions provided by existing scopes within the
      * context. Ownership of the scope is transferred to the stack.

python/core/symbology-ng/qgssymbolv2.sip

@@ -191,6 +191,13 @@ class QgsSymbolV2
      */
     void renderFeature( const QgsFeature& feature, QgsRenderContext& context, int layer = -1, bool selected = false, bool drawVertexMarker = false, int currentVertexMarkerType = 0, int currentVertexMarkerSize = 0 );
 
+    /**
+     * Returns the symbol render context. Only valid between startRender and stopRender calls.
+     *
+     * @return The symbol render context
+     */
+    QgsSymbolV2RenderContext* symbolRenderContext();
+
   protected:
     QgsSymbolV2( SymbolType type, const QgsSymbolLayerV2List& layers /Transfer/ ); // can't be instantiated
 
@@ -283,6 +290,21 @@ class QgsSymbolV2RenderContext
 
     // workaround for sip 4.7. Don't use assignment - will fail with assertion error
     // QgsSymbolV2RenderContext& operator=( const QgsSymbolV2RenderContext& );
+
+    /**
+     * This scope is always available when a symbol of this type is being rendered.
+     *
+     * @return An expression scope for details about this symbol
+     */
+    QgsExpressionContextScope* expressionContextScope();
+    /**
+     * Set an expression scope for this symbol.
+     *
+     * Will take ownership.
+     *
+     * @param contextScope An expression scope for details about this symbol
+     */
+    void setExpressionContextScope( QgsExpressionContextScope* contextScope /Transfer/);
 };
 
 

src/core/qgsexpressioncontext.cpp

@@ -381,6 +381,12 @@ void QgsExpressionContext::appendScope( QgsExpressionContextScope* scope )
   mStack.append( scope );
 }
 
+void QgsExpressionContext::popScope()
+{
+  if ( !mStack.isEmpty() )
+    mStack.pop_back();
+}
+
 QgsExpressionContext& QgsExpressionContext::operator<<( QgsExpressionContextScope* scope )
 {
   mStack.append( scope );

src/core/qgsexpressioncontext.h

@@ -378,6 +378,11 @@ class CORE_EXPORT QgsExpressionContext
      */
     void appendScope( QgsExpressionContextScope* scope );
 
+    /**
+     * Remove the last scope from the expression context.
+     */
+    void popScope();
+
     /** Appends a scope to the end of the context. This scope will override
      * any matching variables or functions provided by existing scopes within the
      * context. Ownership of the scope is transferred to the stack.

src/core/symbology-ng/qgsgeometrygeneratorsymbollayerv2.cpp

@@ -186,17 +186,20 @@ bool QgsGeometryGeneratorSymbolLayerV2::isCompatibleWithSymbol( QgsSymbolV2* sym
   Q_UNUSED( symbol )
   return true;
 }
-
 void QgsGeometryGeneratorSymbolLayerV2::render( QgsSymbolV2RenderContext& context )
 {
-  QgsGeometry geom = mExpression->evaluate( &context.renderContext().expressionContext() ).value<QgsGeometry>();
   if ( context.feature() )
   {
-    QgsFeature f = *context.feature();
+    QgsExpressionContext& expressionContext = context.renderContext().expressionContext();
+
+    QgsFeature f = expressionContext.feature();
+    QgsGeometry geom = mExpression->evaluate( &expressionContext ).value<QgsGeometry>();
     f.setGeometry( geom );
 
+    QgsExpressionContextScope* subSymbolExpressionContextScope = mSymbol->symbolRenderContext()->expressionContextScope();
+
+    subSymbolExpressionContextScope->setFeature( f );
+
     mSymbol->renderFeature( f, context.renderContext() );
   }
 }
-
-

src/core/symbology-ng/qgssymbolv2.cpp

@@ -88,6 +88,7 @@ QgsSymbolV2::QgsSymbolV2( SymbolType type, const QgsSymbolLayerV2List& layers )
     , mRenderHints( 0 )
     , mClipFeaturesToExtent( true )
     , mLayer( nullptr )
+    , mSymbolRenderContext( nullptr )
 {
 
   // check they're all correct symbol layers
@@ -235,6 +236,7 @@ const unsigned char* QgsSymbolV2::_getPolygon( QPolygonF& pts, QList<QPolygonF>&
 
 QgsSymbolV2::~QgsSymbolV2()
 {
+  delete mSymbolRenderContext;
   // delete all symbol layers (we own them, so it's okay)
   qDeleteAll( mLayers );
 }
@@ -434,8 +436,14 @@ bool QgsSymbolV2::changeSymbolLayer( int index, QgsSymbolLayerV2* layer )
 
 void QgsSymbolV2::startRender( QgsRenderContext& context, const QgsFields* fields )
 {
+  delete mSymbolRenderContext;
+  mSymbolRenderContext = new QgsSymbolV2RenderContext( context, outputUnit(), mAlpha, false, mRenderHints, nullptr, fields, mapUnitScale() );
+
   QgsSymbolV2RenderContext symbolContext( context, outputUnit(), mAlpha, false, mRenderHints, nullptr, fields, mapUnitScale() );
 
+  QgsExpressionContextScope* scope = new QgsExpressionContextScope( QApplication::translate( "QgsSymbolV2", "Symbol Scope" ) );
+
+  mSymbolRenderContext->setExpressionContextScope( scope );
 
   Q_FOREACH ( QgsSymbolLayerV2* layer, mLayers )
     layer->startRender( symbolContext );
@@ -443,10 +451,12 @@ void QgsSymbolV2::startRender( QgsRenderContext& context, const QgsFields* field
 
 void QgsSymbolV2::stopRender( QgsRenderContext& context )
 {
-  QgsSymbolV2RenderContext symbolContext( context, outputUnit(), mAlpha, false, mRenderHints, nullptr, nullptr, mapUnitScale() );
-
+  Q_UNUSED( context )
   Q_FOREACH ( QgsSymbolLayerV2* layer, mLayers )
-    layer->stopRender( symbolContext );
+    layer->stopRender( *mSymbolRenderContext );
+
+  delete mSymbolRenderContext;
+  mSymbolRenderContext = nullptr;
 
   mLayer = nullptr;
 }
@@ -701,6 +711,10 @@ void QgsSymbolV2::renderFeature( const QgsFeature& feature, QgsRenderContext& co
     deleteSegmentizedGeometry = true;
   }
 
+  context.expressionContext().appendScope( mSymbolRenderContext->expressionContextScope() );
+  mSymbolRenderContext->expressionContextScope()->setVariable( "geometry_part_count", segmentizedGeometry->geometry()->partCount() );
+  mSymbolRenderContext->expressionContextScope()->setVariable( "geometry_part_num", 1 );
+
   switch ( QgsWKBTypes::flatType( segmentizedGeometry->geometry()->wkbType() ) )
   {
     case QgsWKBTypes::Point:
@@ -766,6 +780,8 @@ void QgsSymbolV2::renderFeature( const QgsFeature& feature, QgsRenderContext& co
 
       for ( int i = 0; i < mp->numGeometries(); ++i )
       {
+        mSymbolRenderContext->expressionContextScope()->setVariable( "geometry_part_num", i + 1 );
+
         const QgsPointV2* point = static_cast< const QgsPointV2* >( mp->geometryN( i ) );
         _getPoint( pt, context, point );
         static_cast<QgsMarkerSymbolV2*>( this )->renderPoint( pt, &feature, context, layer, selected );
@@ -793,6 +809,8 @@ void QgsSymbolV2::renderFeature( const QgsFeature& feature, QgsRenderContext& co
 
       for ( unsigned int i = 0; i < num; ++i )
       {
+        mSymbolRenderContext->expressionContextScope()->setVariable( "geometry_part_num", i + 1 );
+
         if ( geomCollection )
         {
           context.setGeometry( geomCollection->geometryN( i ) );
@@ -824,6 +842,8 @@ void QgsSymbolV2::renderFeature( const QgsFeature& feature, QgsRenderContext& co
 
       for ( unsigned int i = 0; i < num; ++i )
       {
+        mSymbolRenderContext->expressionContextScope()->setVariable( "geometry_part_num", i + 1 );
+
         if ( geomCollection )
         {
           context.setGeometry( geomCollection->geometryN( i ) );
@@ -869,6 +889,13 @@ void QgsSymbolV2::renderFeature( const QgsFeature& feature, QgsRenderContext& co
   {
     delete segmentizedGeometry;
   }
+
+  context.expressionContext().popScope();
+}
+
+QgsSymbolV2RenderContext* QgsSymbolV2::symbolRenderContext()
+{
+  return mSymbolRenderContext;
 }
 
 ////////////////////
@@ -876,6 +903,7 @@ void QgsSymbolV2::renderFeature( const QgsFeature& feature, QgsRenderContext& co
 
 QgsSymbolV2RenderContext::QgsSymbolV2RenderContext( QgsRenderContext& c, QgsSymbolV2::OutputUnit u, qreal alpha, bool selected, int renderHints, const QgsFeature* f, const QgsFields* fields, const QgsMapUnitScale& mapUnitScale )
     : mRenderContext( c ),
+    mExpressionContextScope( nullptr ),
     mOutputUnit( u ),
     mMapUnitScale( mapUnitScale ),
     mAlpha( alpha ),
@@ -888,7 +916,7 @@ QgsSymbolV2RenderContext::QgsSymbolV2RenderContext( QgsRenderContext& c, QgsSymb
 
 QgsSymbolV2RenderContext::~QgsSymbolV2RenderContext()
 {
-
+  delete mExpressionContextScope;
 }
 
 void QgsSymbolV2RenderContext::setOriginalValueVariable( const QVariant& value )
@@ -916,6 +944,16 @@ QgsSymbolV2RenderContext& QgsSymbolV2RenderContext::operator=( const QgsSymbolV2
   return *this;
 }
 
+QgsExpressionContextScope* QgsSymbolV2RenderContext::expressionContextScope()
+{
+  return mExpressionContextScope;
+}
+
+void QgsSymbolV2RenderContext::setExpressionContextScope( QgsExpressionContextScope* contextScope )
+{
+  mExpressionContextScope = contextScope;
+}
+
 ///////////////////
 
 QgsMarkerSymbolV2* QgsMarkerSymbolV2::createSimple( const QgsStringMap& properties )

src/core/symbology-ng/qgssymbolv2.h

@@ -241,6 +241,13 @@ class CORE_EXPORT QgsSymbolV2
      */
     void renderFeature( const QgsFeature& feature, QgsRenderContext& context, int layer = -1, bool selected = false, bool drawVertexMarker = false, int currentVertexMarkerType = 0, int currentVertexMarkerSize = 0 );
 
+    /**
+     * Returns the symbol render context. Only valid between startRender and stopRender calls.
+     *
+     * @return The symbol render context
+     */
+    QgsSymbolV2RenderContext* symbolRenderContext();
+
   protected:
     QgsSymbolV2( SymbolType type, const QgsSymbolLayerV2List& layers ); // can't be instantiated
 
@@ -310,6 +317,9 @@ class CORE_EXPORT QgsSymbolV2
     const QgsVectorLayer* mLayer; //current vectorlayer
 
   private:
+    //! Initialized in startRender, destroyed in stopRender
+    QgsSymbolV2RenderContext* mSymbolRenderContext;
+
     Q_DISABLE_COPY( QgsSymbolV2 )
 
 };
@@ -365,8 +375,24 @@ class CORE_EXPORT QgsSymbolV2RenderContext
     // workaround for sip 4.7. Don't use assignment - will fail with assertion error
     QgsSymbolV2RenderContext& operator=( const QgsSymbolV2RenderContext& );
 
+    /**
+     * This scope is always available when a symbol of this type is being rendered.
+     *
+     * @return An expression scope for details about this symbol
+     */
+    QgsExpressionContextScope* expressionContextScope();
+    /**
+     * Set an expression scope for this symbol.
+     *
+     * Will take ownership.
+     *
+     * @param contextScope An expression scope for details about this symbol
+     */
+    void setExpressionContextScope( QgsExpressionContextScope* contextScope );
+
   private:
     QgsRenderContext& mRenderContext;
+    QgsExpressionContextScope* mExpressionContextScope;
     QgsSymbolV2::OutputUnit mOutputUnit;
     QgsMapUnitScale mMapUnitScale;
     qreal mAlpha;

tests/src/core/testqgsexpressioncontext.cpp

@@ -219,6 +219,9 @@ void TestQgsExpressionContext::contextScopeFunctions()
 void TestQgsExpressionContext::contextStack()
 {
   QgsExpressionContext context;
+
+  context.popScope();
+
   //test retrieving from empty context
   QVERIFY( !context.hasVariable( "test" ) );
   QVERIFY( !context.variable( "test" ).isValid() );
@@ -290,6 +293,11 @@ void TestQgsExpressionContext::contextStack()
   scope2->addVariable( QgsExpressionContextScope::StaticVariable( "readonly", 5, true ) );
   QVERIFY( context.isReadOnly( "readonly" ) );
   QVERIFY( !context.isReadOnly( "test" ) );
+
+  // Check scopes can be popped
+  context.popScope();
+  QCOMPARE( scopes.length(), 2 );
+  QCOMPARE( scopes.at( 0 ), scope1 );
 }
 
 void TestQgsExpressionContext::contextCopy()

tests/src/python/CMakeLists.txt

@@ -59,6 +59,7 @@ ADD_PYTHON_TEST(PyQgsShapefileProvider test_provider_shapefile.py)
 ADD_PYTHON_TEST(PyQgsSpatialIndex test_qgsspatialindex.py)
 ADD_PYTHON_TEST(PyQgsSpatialiteProvider test_provider_spatialite.py)
 ADD_PYTHON_TEST(PyQgsSymbolLayerV2 test_qgssymbollayerv2.py)
+ADD_PYTHON_TEST(PyQgsSymbolExpressionVariables test_qgssymbolexpressionvariables.py)
 ADD_PYTHON_TEST(PyQgsSyntacticSugar test_syntactic_sugar.py)
 ADD_PYTHON_TEST(PyQgsVectorColorRamp test_qgsvectorcolorramp.py)
 ADD_PYTHON_TEST(PyQgsVectorFileWriter test_qgsvectorfilewriter.py)

tests/src/python/test_qgssymbolexpressionvariables.py

@@ -0,0 +1,105 @@
+# -*- coding: utf-8 -*-
+
+"""
+***************************************************************************
+    test_qgssymbolexpressionvariables.py
+    ---------------------
+    Date                 : January 2016
+    Copyright            : (C) 2016 by Matthias Kuhn
+    Email                : matthias at opengis dot ch
+***************************************************************************
+*                                                                         *
+*   This program is free software; you can redistribute it and/or modify  *
+*   it under the terms of the GNU General Public License as published by  *
+*   the Free Software Foundation; either version 2 of the License, or     *
+*   (at your option) any later version.                                   *
+*                                                                         *
+***************************************************************************
+"""
+
+__author__ = 'Matthias Kuhn'
+__date__ = 'January 2016'
+__copyright__ = '(C) 2016, Matthiasd Kuhn'
+# This will get replaced with a git SHA1 when you do a git archive
+__revision__ = '$Format:%H$'
+
+import qgis
+import os
+
+from PyQt4.QtCore import QSize
+
+from qgis.core import (QgsVectorLayer,
+                       QgsMapLayerRegistry,
+                       QgsRectangle,
+                       QgsMultiRenderChecker,
+                       QgsSingleSymbolRendererV2,
+                       QgsFillSymbolV2,
+                       QgsMarkerSymbolV2,
+                       QgsRendererCategoryV2,
+                       QgsCategorizedSymbolRendererV2,
+                       QgsGraduatedSymbolRendererV2,
+                       QgsRendererRangeV2,
+                       QgsFeatureRequest
+                       )
+from utilities import (unitTestDataPath,
+                       getQgisTestApp,
+                       TestCase,
+                       unittest
+                       )
+# Convenience instances in case you may need them
+# not used in this test
+QGISAPP, CANVAS, IFACE, PARENT = getQgisTestApp()
+TEST_DATA_DIR = unitTestDataPath()
+
+
+class TestQgsSymbolExpressionVariables(TestCase):
+
+    def setUp(self):
+        myShpFile = os.path.join(TEST_DATA_DIR, 'polys.shp')
+        self.layer = QgsVectorLayer(myShpFile, 'Polys', 'ogr')
+        QgsMapLayerRegistry.instance().addMapLayer(self.layer)
+
+        rendered_layers = [self.layer.id()]
+        self.mapsettings = CANVAS.mapSettings()
+        self.mapsettings.setOutputSize(QSize(400, 400))
+        self.mapsettings.setOutputDpi(96)
+        self.mapsettings.setExtent(QgsRectangle(-163, 22, -70, 52))
+        self.mapsettings.setLayers(rendered_layers)
+
+    def tearDown(self):
+        QgsMapLayerRegistry.instance().removeAllMapLayers()
+
+    def testPartNum(self):
+        # Create rulebased style
+        sym1 = QgsFillSymbolV2.createSimple({'color': '#fdbf6f'})
+
+        renderer = QgsSingleSymbolRendererV2(sym1)
+        renderer.symbols()[0].symbolLayers()[0].setDataDefinedProperty('color', 'color_rgb( (@geometry_part_num - 1) * 200, 0, 0 )')
+        self.layer.setRendererV2(renderer)
+
+        # Setup rendering check
+        renderchecker = QgsMultiRenderChecker()
+        renderchecker.setMapSettings(self.mapsettings)
+        renderchecker.setControlName('expected_geometry_part_num')
+        result = renderchecker.runTest('part_geometry_part_num')
+
+        self.assertTrue(result)
+
+    def testPartCount(self):
+        # Create rulebased style
+        sym1 = QgsFillSymbolV2.createSimple({'color': '#fdbf6f'})
+
+        renderer = QgsSingleSymbolRendererV2(sym1)
+        renderer.symbols()[0].symbolLayers()[0].setDataDefinedProperty('color', 'color_rgb( (@geometry_part_count - 1) * 200, 0, 0 )')
+        self.layer.setRendererV2(renderer)
+
+        # Setup rendering check
+        renderchecker = QgsMultiRenderChecker()
+        renderchecker.setMapSettings(self.mapsettings)
+        renderchecker.setControlName('expected_geometry_part_count')
+        result = renderchecker.runTest('part_geometry_part_count')
+
+        self.assertTrue(result)
+
+if __name__ == '__main__':
+    unittest.main()