[composer] Allow data defined symbol expressions using atlas feature …

…properties for page background

src/app/composer/qgscompositionwidget.cpp

@@ -386,7 +386,13 @@ void QgsCompositionWidget::on_mPageStyleButton_clicked()
     return;
   }
 
-  QgsSymbolV2SelectorDialog d( mComposition->pageStyleSymbol(), QgsStyleV2::defaultStyle(), 0 );
+  QgsVectorLayer* coverageLayer = 0;
+  // use the atlas coverage layer, if any
+  if ( mComposition->atlasComposition().enabled() )
+  {
+    coverageLayer = mComposition->atlasComposition().coverageLayer();
+  }
+  QgsSymbolV2SelectorDialog d( mComposition->pageStyleSymbol(), QgsStyleV2::defaultStyle(), coverageLayer );
 
   if ( d.exec() == QDialog::Accepted )
   {

src/core/composer/qgsatlascomposition.cpp

@@ -24,6 +24,7 @@
 #include "qgsexpression.h"
 #include "qgsgeometry.h"
 #include "qgscomposerlabel.h"
+#include "qgspaperitem.h"
 #include "qgsmaplayerregistry.h"
 
 QgsAtlasComposition::QgsAtlasComposition( QgsComposition* composition ) :
@@ -369,12 +370,19 @@ void QgsAtlasComposition::prepareForFeature( int featureI )
   // evaluate label expressions
   QList<QgsComposerLabel*> labels;
   mComposition->composerItems( labels );
-
   for ( QList<QgsComposerLabel*>::iterator lit = labels.begin(); lit != labels.end(); ++lit )
   {
     ( *lit )->setExpressionContext( &mCurrentFeature, mCoverageLayer );
   }
 
+  // update page background (in case it uses data defined symbology with atlas properties)
+  QList<QgsPaperItem*> pages;
+  mComposition->composerItems( pages );
+  for ( QList<QgsPaperItem*>::iterator pageIt = pages.begin(); pageIt != pages.end(); ++pageIt )
+  {
+    ( *pageIt )->update();
+  }
+
   // set the new extent (and render)
   mComposerMap->setNewAtlasFeatureExtent( new_extent );
 

src/core/composer/qgsatlascomposition.h

@@ -110,6 +110,9 @@ class CORE_EXPORT QgsAtlasComposition : public QObject
     void lastFeature();
     void firstFeature();
 
+    /** Returns the current atlas feature. Must be called after prepareForFeature( i ). */
+    QgsFeature* currentFeature() { return &mCurrentFeature; }
+
   signals:
     /** emitted when one of the parameters changes */
     void parameterChanged();

src/core/composer/qgspaperitem.cpp

@@ -190,10 +190,21 @@ void QgsPaperItem::paint( QPainter* painter, const QStyleOptionGraphicsItem* ite
   calculatePageMargin();
   QPolygonF pagePolygon = QPolygonF( QRectF( mPageMargin, mPageMargin, rect().width() - 2 * mPageMargin, rect().height() - 2 * mPageMargin ) );
   QList<QPolygonF> rings; //empty list
-  mComposition->pageStyleSymbol()->renderPolygon( pagePolygon, &rings, 0, context );
+
+  //need to render using atlas feature properties?
+  if ( mComposition->atlasComposition().enabled() && mComposition->atlasMode() != QgsComposition::AtlasOff )
+  {
+    //using an atlas, so render using current atlas feature
+    //since there may be data defined symbols using atlas feature properties
+    mComposition->pageStyleSymbol()->renderPolygon( pagePolygon, &rings, mComposition->atlasComposition().currentFeature(), context );
+  }
+  else
+  {
+    mComposition->pageStyleSymbol()->renderPolygon( pagePolygon, &rings, 0, context );
+  }
+
   mComposition->pageStyleSymbol()->stopRender( context );
   painter->restore();
-
 }
 
 void QgsPaperItem::calculatePageMargin()