[composer] Fix area calculation in expressions with OTF (fix #9791)

Adds an argument to QgsExpression::replaceExpressionText to allow
passing an optional QgsDistanceArea to use during calculations.
Ensure that html and label composer items correctly specify this
argument.

python/core/qgsexpression.sip

@@ -90,17 +90,26 @@ class QgsExpression
     //! Sets the geometry calculator used in evaluation of expressions,
     // instead of the default.
     void setGeomCalculator( const QgsDistanceArea &calc );
-
+    
     /** This function currently replaces each expression between [% and %]
        in the string with the result of its evaluation on the feature
        passed as argument.
 
        Additional substitutions can be passed through the substitutionMap
        parameter
+       @param action
+       @param feat
+       @param layer
+       @param substitutionMap
+       @param distanceArea optional QgsDistanceArea. If specified, the QgsDistanceArea is used for distance
+       and area conversion
     */
     static QString replaceExpressionText( const QString &action, const QgsFeature *feat,
                                           QgsVectorLayer *layer,
-                                          const QMap<QString, QVariant> *substitutionMap = 0 );
+                                          const QMap<QString, QVariant> *substitutionMap = 0,
+                                          const QgsDistanceArea* distanceArea = 0
+                                        );
+
     enum UnaryOperator
     {
       uoNot,

src/core/composer/qgscomposerhtml.cpp

@@ -22,6 +22,8 @@
 #include "qgsexpression.h"
 #include "qgslogger.h"
 #include "qgsnetworkcontentfetcher.h"
+#include "qgsvectorlayer.h"
+#include "qgsproject.h"
 
 #include <QCoreApplication>
 #include <QPainter>
@@ -42,9 +44,11 @@ QgsComposerHtml::QgsComposerHtml( QgsComposition* c, bool createUndoCommands )
     , mMaxBreakDistance( 10 )
     , mExpressionFeature( 0 )
     , mExpressionLayer( 0 )
+    , mDistanceArea( 0 )
     , mEnableUserStylesheet( false )
     , mFetcher( 0 )
 {
+  mDistanceArea = new QgsDistanceArea();
   mHtmlUnitsToMM = htmlUnitsToMM();
   mWebPage = new QWebPage();
   mWebPage->mainFrame()->setScrollBarPolicy( Qt::Horizontal, Qt::ScrollBarAlwaysOff );
@@ -92,14 +96,17 @@ QgsComposerHtml::QgsComposerHtml()
     , mMaxBreakDistance( 10 )
     , mExpressionFeature( 0 )
     , mExpressionLayer( 0 )
+    , mDistanceArea( 0 )
     , mFetcher( 0 )
 {
+  mDistanceArea = new QgsDistanceArea();
   mFetcher = new QgsNetworkContentFetcher();
   connect( mFetcher, SIGNAL( finished() ), this, SLOT( frameLoaded() ) );
 }
 
 QgsComposerHtml::~QgsComposerHtml()
 {
+  delete mDistanceArea;
   delete mWebPage;
   delete mRenderedPage;
   mFetcher->deleteLater();
@@ -179,7 +186,7 @@ void QgsComposerHtml::loadHtml()
   //evaluate expressions
   if ( mEvaluateExpressions )
   {
-    loadedHtml = QgsExpression::replaceExpressionText( loadedHtml, mExpressionFeature, mExpressionLayer );
+    loadedHtml = QgsExpression::replaceExpressionText( loadedHtml, mExpressionFeature, mExpressionLayer, 0, mDistanceArea );
   }
 
   mLoaded = false;
@@ -522,6 +529,22 @@ void QgsComposerHtml::setExpressionContext( QgsFeature* feature, QgsVectorLayer*
 {
   mExpressionFeature = feature;
   mExpressionLayer = layer;
+
+  //setup distance area conversion
+  if ( layer )
+  {
+    mDistanceArea->setSourceCrs( layer->crs().srsid() );
+  }
+  else if ( mComposition )
+  {
+    //set to composition's mapsettings' crs
+    mDistanceArea->setSourceCrs( mComposition->mapSettings().destinationCrs().srsid() );
+  }
+  if ( mComposition )
+  {
+    mDistanceArea->setEllipsoidalMode( mComposition->mapSettings().hasCrsTransformEnabled() );
+  }
+  mDistanceArea->setEllipsoid( QgsProject::instance()->readEntry( "Measure", "/Ellipsoid", GEO_NONE ) );
 }
 
 void QgsComposerHtml::refreshExpressionContext()

src/core/composer/qgscomposerhtml.h

@@ -24,6 +24,7 @@ class QImage;
 class QgsFeature;
 class QgsVectorLayer;
 class QgsNetworkContentFetcher;
+class QgsDistanceArea;
 
 class CORE_EXPORT QgsComposerHtml: public QgsComposerMultiFrame
 {
@@ -242,6 +243,8 @@ class CORE_EXPORT QgsComposerHtml: public QgsComposerMultiFrame
 
     QgsFeature* mExpressionFeature;
     QgsVectorLayer* mExpressionLayer;
+    QgsDistanceArea* mDistanceArea;
+
     QString mUserStylesheet;
     bool mEnableUserStylesheet;
 

src/core/composer/qgscomposerlabel.cpp

@@ -21,6 +21,8 @@
 #include "qgsexpression.h"
 #include "qgsnetworkaccessmanager.h"
 #include "qgscomposermodel.h"
+#include "qgsvectorlayer.h"
+#include "qgsproject.h"
 
 #include <QCoreApplication>
 #include <QDate>
@@ -32,12 +34,20 @@
 #include <QWebPage>
 #include <QEventLoop>
 
-QgsComposerLabel::QgsComposerLabel( QgsComposition *composition ):
-    QgsComposerItem( composition ), mHtmlState( 0 ), mHtmlUnitsToMM( 1.0 ),
-    mHtmlLoaded( false ), mMargin( 1.0 ), mFontColor( QColor( 0, 0, 0 ) ),
-    mHAlignment( Qt::AlignLeft ), mVAlignment( Qt::AlignTop ),
-    mExpressionFeature( 0 ), mExpressionLayer( 0 )
+QgsComposerLabel::QgsComposerLabel( QgsComposition *composition )
+    : QgsComposerItem( composition )
+    , mHtmlState( 0 )
+    , mHtmlUnitsToMM( 1.0 )
+    , mHtmlLoaded( false )
+    , mMargin( 1.0 )
+    , mFontColor( QColor( 0, 0, 0 ) )
+    , mHAlignment( Qt::AlignLeft )
+    , mVAlignment( Qt::AlignTop )
+    , mExpressionFeature( 0 )
+    , mExpressionLayer( 0 )
+    , mDistanceArea( 0 )
 {
+  mDistanceArea = new QgsDistanceArea();
   mHtmlUnitsToMM = htmlUnitsToMM();
 
   //get default composer font from settings
@@ -71,6 +81,7 @@ QgsComposerLabel::QgsComposerLabel( QgsComposition *composition ):
 
 QgsComposerLabel::~QgsComposerLabel()
 {
+  delete mDistanceArea;
 }
 
 void QgsComposerLabel::paint( QPainter* painter, const QStyleOptionGraphicsItem* itemStyle, QWidget* pWidget )
@@ -221,6 +232,23 @@ void QgsComposerLabel::setExpressionContext( QgsFeature* feature, QgsVectorLayer
   mExpressionFeature = feature;
   mExpressionLayer = layer;
   mSubstitutions = substitutions;
+
+  //setup distance area conversion
+  if ( layer )
+  {
+    mDistanceArea->setSourceCrs( layer->crs().srsid() );
+  }
+  else if ( mComposition )
+  {
+    //set to composition's mapsettings' crs
+    mDistanceArea->setSourceCrs( mComposition->mapSettings().destinationCrs().srsid() );
+  }
+  if ( mComposition )
+  {
+    mDistanceArea->setEllipsoidalMode( mComposition->mapSettings().hasCrsTransformEnabled() );
+  }
+  mDistanceArea->setEllipsoid( QgsProject::instance()->readEntry( "Measure", "/Ellipsoid", GEO_NONE ) );
+
   // Force label to redraw -- fixes label printing for labels with blend modes when used with atlas
   update();
 }
@@ -248,7 +276,7 @@ QString QgsComposerLabel::displayText() const
   replaceDateText( displayText );
   QMap<QString, QVariant> subs = mSubstitutions;
   subs[ "$page" ] = QVariant(( int )mComposition->itemPageNumber( this ) + 1 );
-  return QgsExpression::replaceExpressionText( displayText, mExpressionFeature, mExpressionLayer, &subs );
+  return QgsExpression::replaceExpressionText( displayText, mExpressionFeature, mExpressionLayer, &subs, mDistanceArea );
 }
 
 void QgsComposerLabel::replaceDateText( QString& text ) const

src/core/composer/qgscomposerlabel.h

@@ -22,6 +22,7 @@
 
 class QgsVectorLayer;
 class QgsFeature;
+class QgsDistanceArea;
 
 /** \ingroup MapComposer
  * A label that can be placed onto a map composition.
@@ -143,8 +144,7 @@ class CORE_EXPORT QgsComposerLabel: public QgsComposerItem
     QgsFeature* mExpressionFeature;
     QgsVectorLayer* mExpressionLayer;
     QMap<QString, QVariant> mSubstitutions;
-
-
+    QgsDistanceArea* mDistanceArea;
 };
 
 #endif

src/core/qgsexpression.cpp

@@ -1989,7 +1989,7 @@ void QgsExpression::acceptVisitor( QgsExpression::Visitor& v ) const
 
 QString QgsExpression::replaceExpressionText( const QString &action, const QgsFeature *feat,
     QgsVectorLayer *layer,
-    const QMap<QString, QVariant> *substitutionMap )
+    const QMap<QString, QVariant> *substitutionMap , const QgsDistanceArea *distanceArea )
 {
   QString expr_action;
 
@@ -2030,6 +2030,12 @@ QString QgsExpression::replaceExpressionText( const QString &action, const QgsFe
       continue;
     }
 
+    if ( distanceArea )
+    {
+      //if QgsDistanceArea specified for area/distance conversion, use it
+      exp.setGeomCalculator( *distanceArea );
+    }
+
     QVariant result;
     if ( layer )
     {

src/core/qgsexpression.h

@@ -183,10 +183,18 @@ class CORE_EXPORT QgsExpression
 
        Additional substitutions can be passed through the substitutionMap
        parameter
+       @param action
+       @param feat
+       @param layer
+       @param substitutionMap
+       @param distanceArea optional QgsDistanceArea. If specified, the QgsDistanceArea is used for distance
+       and area conversion
     */
     static QString replaceExpressionText( const QString &action, const QgsFeature *feat,
                                           QgsVectorLayer *layer,
-                                          const QMap<QString, QVariant> *substitutionMap = 0 );
+                                          const QMap<QString, QVariant> *substitutionMap = 0,
+                                          const QgsDistanceArea* distanceArea = 0
+                                        );
     enum UnaryOperator
     {
       uoNot,