[FEATURE] Allow definition of rendering order for renderers

This allows defining the order in which features are processed by
renderers.

python/gui/qgsorderbydialog.sip

@@ -0,0 +1,34 @@
+/***************************************************************************
+ qgsorderbydialog.h
+
+ ---------------------
+ begin                : 20.12.2015
+ copyright            : (C) 2015 by Matthias Kuhn
+ email                : matthias@opengis.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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+class QgsOrderByDialog : QDialog
+{
+%TypeHeaderCode
+#include "qgsorderbydialog.h"
+%End
+  public:
+    QgsOrderByDialog( QgsVectorLayer* layer, QWidget* parent = nullptr );
+
+    /**
+     * Set the order by to manage
+     */
+    void setOrderBys( const QList<QgsFeatureRequest::OrderByClause>& orderBys );
+
+    /**
+     * Get the order by defined in the dialog
+     */
+    QgsFeatureRequest::OrderBy orderBys();
+};

src/core/qgsfeaturerequest.cpp

@@ -346,7 +346,7 @@ void QgsFeatureRequest::OrderBy::load( const QDomElement& elem )
   for ( int i = 0; i < clauses.size(); ++i )
   {
     QDomElement clauseElem = clauses.at( i ).toElement();
-    QString expression = clauseElem.toText().data();
+    QString expression = clauseElem.text();
     bool asc = clauseElem.attribute( "asc" ).toInt() != 0;
     bool nullsFirst  = clauseElem.attribute( "nullsFirst" ).toInt() != 0;
 

src/core/qgsvectorlayerrenderer.cpp

@@ -150,10 +150,13 @@ bool QgsVectorLayerRenderer::render()
   QgsRectangle requestExtent = mContext.extent();
   mRendererV2->modifyRequestExtent( requestExtent, mContext );
 
+  QgsFeatureRequest::OrderBy orderBy = mRendererV2->orderBy();
+
   QgsFeatureRequest featureRequest = QgsFeatureRequest()
                                      .setFilterRect( requestExtent )
                                      .setSubsetOfAttributes( mAttrNames, mFields )
-                                     .setExpressionContext( mContext.expressionContext() );
+                                     .setExpressionContext( mContext.expressionContext() )
+                                     .setOrderBys( orderBy );
 
   const QgsFeatureFilterProvider* featureFilterProvider = mContext.featureFilterProvider();
   if ( featureFilterProvider )

src/core/symbology-ng/qgscategorizedsymbolrendererv2.cpp

@@ -498,7 +498,7 @@ QgsCategorizedSymbolRendererV2* QgsCategorizedSymbolRendererV2::clone() const
   r->setUsingSymbolLevels( usingSymbolLevels() );
   r->setSizeScaleField( sizeScaleField() );
 
-  copyPaintEffect( r );
+  copyRendererData( r );
   return r;
 }
 
@@ -761,6 +761,13 @@ QDomElement QgsCategorizedSymbolRendererV2::save( QDomDocument& doc )
   if ( mPaintEffect && !QgsPaintEffectRegistry::isDefaultStack( mPaintEffect ) )
     mPaintEffect->saveProperties( doc, rendererElem );
 
+  if ( !mOrderBy.isEmpty() )
+  {
+    QDomElement orderBy = doc.createElement( "orderby" );
+    mOrderBy.save( orderBy );
+    rendererElem.appendChild( orderBy );
+  }
+
   return rendererElem;
 }
 

src/core/symbology-ng/qgsgraduatedsymbolrendererv2.cpp

@@ -529,7 +529,7 @@ QgsGraduatedSymbolRendererV2* QgsGraduatedSymbolRendererV2::clone() const
   r->setSizeScaleField( sizeScaleField() );
   r->setLabelFormat( labelFormat() );
   r->setGraduatedMethod( graduatedMethod() );
-  copyPaintEffect( r );
+  copyRendererData( r );
   return r;
 }
 
@@ -1171,6 +1171,13 @@ QDomElement QgsGraduatedSymbolRendererV2::save( QDomDocument& doc )
   if ( mPaintEffect && !QgsPaintEffectRegistry::isDefaultStack( mPaintEffect ) )
     mPaintEffect->saveProperties( doc, rendererElem );
 
+  if ( !mOrderBy.isEmpty() )
+  {
+    QDomElement orderBy = doc.createElement( "orderby" );
+    mOrderBy.save( orderBy );
+    rendererElem.appendChild( orderBy );
+  }
+
   return rendererElem;
 }
 

src/core/symbology-ng/qgsheatmaprenderer.cpp

@@ -297,7 +297,7 @@ QgsHeatmapRenderer* QgsHeatmapRenderer::clone() const
   newRenderer->setMaximumValue( mExplicitMax );
   newRenderer->setRenderQuality( mRenderQuality );
   newRenderer->setWeightExpression( mWeightExpressionString );
-  copyPaintEffect( newRenderer );
+  copyRendererData( newRenderer );
 
   return newRenderer;
 }
@@ -365,6 +365,13 @@ QDomElement QgsHeatmapRenderer::save( QDomDocument& doc )
   if ( mPaintEffect && !QgsPaintEffectRegistry::isDefaultStack( mPaintEffect ) )
     mPaintEffect->saveProperties( doc, rendererElem );
 
+  if ( !mOrderBy.isEmpty() )
+  {
+    QDomElement orderBy = doc.createElement( "orderby" );
+    mOrderBy.save( orderBy );
+    rendererElem.appendChild( orderBy );
+  }
+
   return rendererElem;
 }
 

src/core/symbology-ng/qgsrendererv2.cpp

@@ -204,6 +204,15 @@ void QgsFeatureRendererV2::setScaleMethodToSymbol( QgsSymbolV2* symbol, int scal
   }
 }
 
+void QgsFeatureRendererV2::copyRendererData( QgsFeatureRendererV2* destRenderer ) const
+{
+  if ( !destRenderer || !mPaintEffect )
+    return;
+
+  destRenderer->setPaintEffect( mPaintEffect->clone() );
+  destRenderer->mOrderBy = mOrderBy;
+}
+
 void QgsFeatureRendererV2::copyPaintEffect( QgsFeatureRendererV2 *destRenderer ) const
 {
   if ( !destRenderer || !mPaintEffect )
@@ -212,7 +221,6 @@ void QgsFeatureRendererV2::copyPaintEffect( QgsFeatureRendererV2 *destRenderer )
   destRenderer->setPaintEffect( mPaintEffect->clone() );
 }
 
-
 QgsFeatureRendererV2::QgsFeatureRendererV2( const QString& type )
     : mType( type )
     , mUsingSymbolLevels( false )
@@ -331,6 +339,10 @@ QgsFeatureRendererV2* QgsFeatureRendererV2::load( QDomElement& element )
     {
       r->setPaintEffect( QgsPaintEffectRegistry::instance()->createEffect( effectElem ) );
     }
+
+    // restore order by
+    QDomElement orderByElem = element.firstChildElement( "orderby" );
+    r->mOrderBy.load( orderByElem );
   }
   return r;
 }
@@ -344,6 +356,12 @@ QDomElement QgsFeatureRendererV2::save( QDomDocument& doc )
   if ( mPaintEffect && !QgsPaintEffectRegistry::isDefaultStack( mPaintEffect ) )
     mPaintEffect->saveProperties( doc, rendererElem );
 
+  if ( !mOrderBy.isEmpty() )
+  {
+    QDomElement orderBy = doc.createElement( "orderby" );
+    mOrderBy.save( orderBy );
+    rendererElem.appendChild( orderBy );
+  }
   return rendererElem;
 }
 
@@ -598,6 +616,16 @@ void QgsFeatureRendererV2::setPaintEffect( QgsPaintEffect *effect )
   mPaintEffect = effect;
 }
 
+QgsFeatureRequest::OrderBy QgsFeatureRendererV2::orderBy()
+{
+  return mOrderBy;
+}
+
+void QgsFeatureRendererV2::setOrderBy( const QgsFeatureRequest::OrderBy& orderBys )
+{
+  mOrderBy = orderBys;
+}
+
 void QgsFeatureRendererV2::convertSymbolSizeScale( QgsSymbolV2 * symbol, QgsSymbolV2::ScaleMethod method, const QString & field )
 {
   if ( symbol->type() == QgsSymbolV2::Marker )

src/core/symbology-ng/qgsrendererv2.h

@@ -21,6 +21,7 @@
 #include "qgsrendercontext.h"
 #include "qgssymbolv2.h"
 #include "qgsfield.h"
+#include "qgsfeaturerequest.h"
 
 #include <QList>
 #include <QString>
@@ -343,6 +344,18 @@ class CORE_EXPORT QgsFeatureRendererV2
      */
     void setForceRasterRender( bool forceRaster ) { mForceRaster = forceRaster; }
 
+    /**
+     * Get the order in which features shall be processed by this renderer.
+     * @note added in QGIS 2.14
+     */
+    QgsFeatureRequest::OrderBy orderBy();
+
+    /**
+     * Define the order in which features shall be processed by this renderer.
+     * @note added in QGIS 2.14
+     */
+    void setOrderBy( const QgsFeatureRequest::OrderBy& orderBys );
+
   protected:
     QgsFeatureRendererV2( const QString& type );
 
@@ -366,10 +379,21 @@ class CORE_EXPORT QgsFeatureRendererV2
 
     void setScaleMethodToSymbol( QgsSymbolV2* symbol, int scaleMethod );
 
-    /** Copies paint effect of this renderer to another renderer
+    /**
+     * Clones generic renderer data to another renderer.
+     * Currently clones
+     *  * Order By
+     *  * Paint Effect
+     *
      * @param destRenderer destination renderer for copied effect
      */
-    void copyPaintEffect( QgsFeatureRendererV2 *destRenderer ) const;
+    void copyRendererData( QgsFeatureRendererV2 *destRenderer ) const;
+
+    /** Copies paint effect of this renderer to another renderer
+     * @param destRenderer destination renderer for copied effect
+     * @deprecated use copyRendererData instead
+     */
+    Q_DECL_DEPRECATED void copyPaintEffect( QgsFeatureRendererV2 *destRenderer ) const;
 
     QString mType;
 
@@ -393,6 +417,8 @@ class CORE_EXPORT QgsFeatureRendererV2
      */
     static void convertSymbolRotation( QgsSymbolV2 * symbol, const QString & field );
 
+    QgsFeatureRequest::OrderBy mOrderBy;
+
   private:
     Q_DISABLE_COPY( QgsFeatureRendererV2 )
 };

src/core/symbology-ng/qgssinglesymbolrendererv2.cpp

@@ -201,7 +201,7 @@ QgsSingleSymbolRendererV2* QgsSingleSymbolRendererV2::clone() const
   QgsSingleSymbolRendererV2* r = new QgsSingleSymbolRendererV2( mSymbol->clone() );
   r->setUsingSymbolLevels( usingSymbolLevels() );
   r->setSizeScaleField( sizeScaleField() );
-  copyPaintEffect( r );
+  copyRendererData( r );
   return r;
 }
 
@@ -381,6 +381,12 @@ QDomElement QgsSingleSymbolRendererV2::save( QDomDocument& doc )
   if ( mPaintEffect && !QgsPaintEffectRegistry::isDefaultStack( mPaintEffect ) )
     mPaintEffect->saveProperties( doc, rendererElem );
 
+  if ( !mOrderBy.isEmpty() )
+  {
+    QDomElement orderBy = doc.createElement( "orderby" );
+    mOrderBy.save( orderBy );
+    rendererElem.appendChild( orderBy );
+  }
   return rendererElem;
 }
 

src/gui/CMakeLists.txt

@@ -238,6 +238,7 @@ SET(QGIS_GUI_SRCS
   qgsnewvectorlayerdialog.cpp
   qgsnumericsortlistviewitem.cpp
   qgsoptionsdialogbase.cpp
+  qgsorderbydialog.cpp
   qgsowssourceselect.cpp
   qgspixmaplabel.cpp
   qgspluginmanagerinterface.cpp
@@ -367,6 +368,7 @@ SET(QGIS_GUI_MOC_HDRS
   qgsnewnamedialog.h
   qgsnewvectorlayerdialog.h
   qgsoptionsdialogbase.h
+  qgsorderbydialog.h
   qgsowssourceselect.h
   qgspixmaplabel.h
   qgspluginmanagerinterface.h

src/gui/qgsorderbydialog.cpp

@@ -0,0 +1,178 @@
+/***************************************************************************
+ qgosorderbydialog.cpp
+
+ ---------------------
+ begin                : 20.12.2015
+ copyright            : (C) 2015 by Matthias Kuhn
+ email                : matthias@opengis.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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsorderbydialog.h"
+
+#include "qgsexpressionbuilderdialog.h"
+
+#include <QTableWidget>
+#include <QCheckBox>
+#include <QKeyEvent>
+
+QgsOrderByDialog::QgsOrderByDialog( QgsVectorLayer* layer, QWidget* parent )
+    : QDialog( parent )
+    , mLayer( layer )
+{
+  setupUi( this );
+  connect( mOrderByTableWidget, SIGNAL( cellDoubleClicked( int, int ) ), this, SLOT( onCellDoubleClicked( int, int ) ) );
+  connect( mOrderByTableWidget, SIGNAL( cellChanged( int, int ) ), this, SLOT( onCellChanged( int, int ) ) );
+
+  mOrderByTableWidget->horizontalHeader()->setResizeMode( QHeaderView::Stretch );
+  mOrderByTableWidget->horizontalHeader()->setResizeMode( 1, QHeaderView::Interactive );
+  mOrderByTableWidget->horizontalHeader()->setResizeMode( 2, QHeaderView::Interactive );
+
+  mOrderByTableWidget->installEventFilter( this );
+}
+
+void QgsOrderByDialog::setOrderBy( const QgsFeatureRequest::OrderBy& orderBy )
+{
+  mOrderByTableWidget->clear();
+  mOrderByTableWidget->setRowCount( orderBy.length() + 1 );
+
+  int i = 0;
+  Q_FOREACH ( const QgsFeatureRequest::OrderByClause& orderByClause, orderBy )
+  {
+    QTableWidgetItem* expressionItem  = new QTableWidgetItem( orderByClause.expression().expression() );
+    QCheckBox* ascCheckBox        = new QCheckBox();
+    ascCheckBox->setChecked( orderByClause.ascending() );
+    QCheckBox* nullsFirstCheckBox = new QCheckBox();
+    nullsFirstCheckBox->setChecked( orderByClause.nullsFirst() );
+
+    mOrderByTableWidget->setItem( i, 0, expressionItem );
+    mOrderByTableWidget->setCellWidget( i, 1, ascCheckBox );
+    mOrderByTableWidget->setCellWidget( i, 2, nullsFirstCheckBox );
+
+    ++i;
+  }
+
+  // Add an empty widget at the end
+  QTableWidgetItem* expressionItem  = new QTableWidgetItem( "" );
+  QCheckBox* ascCheckBox        = new QCheckBox();
+  ascCheckBox->setChecked( true );
+  QCheckBox* nullsFirstCheckBox = new QCheckBox();
+
+  mOrderByTableWidget->setItem( i, 0, expressionItem );
+  mOrderByTableWidget->setCellWidget( i, 1, ascCheckBox );
+  mOrderByTableWidget->setCellWidget( i, 2, nullsFirstCheckBox );
+}
+
+QgsFeatureRequest::OrderBy QgsOrderByDialog::orderBy()
+{
+  QgsFeatureRequest::OrderBy orderBys;
+
+  for ( int i = 0; i < mOrderByTableWidget->rowCount(); ++i )
+  {
+    QString expressionText = mOrderByTableWidget->item( i, 0 )->text();
+
+    if ( ! expressionText.isEmpty() )
+    {
+      bool asc = static_cast<QCheckBox*>( mOrderByTableWidget->cellWidget( i, 1 ) )->checkState();
+      bool nullsFirst = static_cast<QCheckBox*>( mOrderByTableWidget->cellWidget( i, 2 ) )->checkState();
+      QgsFeatureRequest::OrderByClause orderBy( expressionText, asc, nullsFirst );
+
+      orderBys << orderBy;
+    }
+  }
+
+  return orderBys;
+}
+
+void QgsOrderByDialog::onCellDoubleClicked( int row, int column )
+{
+  // Only act on first cell where the expression text is
+  if ( 0 == column )
+  {
+    QgsExpressionBuilderDialog dlg( mLayer );
+
+    dlg.setExpressionText( mOrderByTableWidget->item( row, column )->text() );
+
+    if ( dlg.exec() )
+    {
+      QString expressionText = dlg.expressionText();
+
+      mOrderByTableWidget->item( row, column )->setText( expressionText );
+
+      if ( row == mOrderByTableWidget->rowCount() - 1 )
+      {
+        // Add an empty widget at the end if the last row was edited
+        mOrderByTableWidget->insertRow( mOrderByTableWidget->rowCount() );
+
+        QTableWidgetItem* expressionItem  = new QTableWidgetItem( "" );
+        QCheckBox* ascCheckBox        = new QCheckBox();
+        ascCheckBox->setChecked( true );
+        QCheckBox* nullsFirstCheckBox = new QCheckBox();
+
+        mOrderByTableWidget->setItem( row + 1, 0, expressionItem );
+        mOrderByTableWidget->setCellWidget( row + 1, 1, ascCheckBox );
+        mOrderByTableWidget->setCellWidget( row + 1, 2, nullsFirstCheckBox );
+      }
+    }
+  }
+}
+
+void QgsOrderByDialog::onCellChanged( int row, int column )
+{
+  // If the text was cleared
+  if ( mOrderByTableWidget->item( row, column )->text().isEmpty() )
+  {
+    // If the first column (expression text) and not the last row was edited
+    if ( 0 == column && row != mOrderByTableWidget->rowCount() - 1 )
+    {
+      {
+        mOrderByTableWidget->removeRow( row );
+      }
+    }
+  }
+  else
+  {
+    // If it's the last row and an expression was added: add a new empty one
+    if ( row == mOrderByTableWidget->rowCount() - 1 && !mOrderByTableWidget->item( row, column )->text().isEmpty() )
+    {
+      // Add an empty widget at the end if the last row was edited
+      mOrderByTableWidget->insertRow( mOrderByTableWidget->rowCount() );
+
+      QTableWidgetItem* expressionItem  = new QTableWidgetItem( "" );
+      QCheckBox* ascCheckBox        = new QCheckBox();
+      ascCheckBox->setChecked( true );
+      QCheckBox* nullsFirstCheckBox = new QCheckBox();
+
+      mOrderByTableWidget->setItem( row + 1, 0, expressionItem );
+      mOrderByTableWidget->setCellWidget( row + 1, 1, ascCheckBox );
+      mOrderByTableWidget->setCellWidget( row + 1, 2, nullsFirstCheckBox );
+    }
+  }
+}
+
+bool QgsOrderByDialog::eventFilter( QObject* obj, QEvent* e )
+{
+  Q_UNUSED( obj )
+  Q_ASSERT( obj == mOrderByTableWidget );
+
+  if ( e->type() == QEvent::KeyPress )
+  {
+    QKeyEvent* keyEvent = static_cast<QKeyEvent*>( e );
+
+    if ( keyEvent->key() == Qt::Key_Delete )
+    {
+      if ( mOrderByTableWidget->currentRow() != mOrderByTableWidget->rowCount() - 1 )
+        mOrderByTableWidget->removeRow( mOrderByTableWidget->currentRow() );
+      return true;
+    }
+  }
+
+  return false;
+}
+

src/gui/qgsorderbydialog.h

@@ -0,0 +1,65 @@
+/***************************************************************************
+ qgsorderbydialog.h
+
+ ---------------------
+ begin                : 20.12.2015
+ copyright            : (C) 2015 by Matthias Kuhn
+ email                : matthias@opengis.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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSORDERBYDIALOG_H
+#define QGSORDERBYDIALOG_H
+
+#include <QDialog>
+
+#include "qgsfeaturerequest.h"
+
+#include "ui_qgsorderbydialogbase.h"
+
+/**
+ * This is a dialog to build and manage a list of order by clauses.
+ *
+ * @note added in 2.14
+ */
+
+class GUI_EXPORT QgsOrderByDialog : public QDialog, private Ui::OrderByDialogBase
+{
+    Q_OBJECT
+
+  public:
+    /**
+     * Create a new order by dialog. This helps building order by structures.
+     *
+     * @param layer  The vector layer for which the order by should be produced
+     * @param parent The parent widget, optional
+     */
+    QgsOrderByDialog( QgsVectorLayer* layer, QWidget* parent = nullptr );
+
+    /**
+     * Set the order by to manage
+     */
+    void setOrderBy( const QgsFeatureRequest::OrderBy& orderBy );
+
+    /**
+     * Get the order by defined in the dialog
+     */
+    QgsFeatureRequest::OrderBy orderBy();
+
+  private slots:
+    void onCellDoubleClicked( int row, int column );
+    void onCellChanged( int row, int column );
+
+  private:
+    QgsVectorLayer* mLayer;
+
+    bool eventFilter( QObject *obj, QEvent *e );
+};
+
+#endif // QGSORDERBYDIALOG_H

src/gui/symbology-ng/qgsrendererv2propertiesdialog.cpp

@@ -25,6 +25,7 @@
 #include "qgspointdisplacementrendererwidget.h"
 #include "qgsinvertedpolygonrendererwidget.h"
 #include "qgsheatmaprendererwidget.h"
+#include "qgsorderbydialog.h"
 
 #include "qgsapplication.h"
 #include "qgslogger.h"
@@ -109,13 +110,17 @@ QgsRendererV2PropertiesDialog::QgsRendererV2PropertiesDialog( QgsVectorLayer* la
   connect( mLayerTransparencySpnBx, SIGNAL( valueChanged( int ) ), mLayerTransparencySlider, SLOT( setValue( int ) ) );
 
   //paint effect widget
-  if ( mLayer->rendererV2() && mLayer->rendererV2()->paintEffect() )
+  if ( mLayer->rendererV2() )
   {
-    mPaintEffect = mLayer->rendererV2()->paintEffect()->clone();
-    mEffectWidget->setPaintEffect( mPaintEffect );
+    if ( mLayer->rendererV2()->paintEffect() )
+    {
+      mPaintEffect = mLayer->rendererV2()->paintEffect()->clone();
+      mEffectWidget->setPaintEffect( mPaintEffect );
+    }
+
+    mOrderBy = mLayer->rendererV2()->orderBy();
   }
 
-  QPixmap pix;
   QgsRendererV2Registry* reg = QgsRendererV2Registry::instance();
   QStringList renderers = reg->renderersList();
   Q_FOREACH ( const QString& name, renderers )
@@ -128,21 +133,31 @@ QgsRendererV2PropertiesDialog::QgsRendererV2PropertiesDialog( QgsVectorLayer* la
 
   // setup slot rendererChanged()
   connect( cboRenderers, SIGNAL( currentIndexChanged( int ) ), this, SLOT( rendererChanged() ) );
+  //setup order by
+  if ( mOrderBy.isEmpty() )
+  {
+    btnOrderBy->setEnabled( false );
+    checkboxEnableOrderBy->setChecked( false );
+    lineEditOrderBy->setEnabled( false );
+  }
+  else
+  {
+    checkboxEnableOrderBy->setChecked( true );
+  }
+  lineEditOrderBy->setReadOnly( true );
+  connect( checkboxEnableOrderBy, SIGNAL( toggled( bool ) ), btnOrderBy, SLOT( setEnabled( bool ) ) );
+  connect( checkboxEnableOrderBy, SIGNAL( toggled( bool ) ), lineEditOrderBy, SLOT( setEnabled( bool ) ) );
+  connect( btnOrderBy, SIGNAL( clicked( bool ) ), this, SLOT( showOrderByDialog() ) );
+  lineEditOrderBy->setText( mOrderBy.dump() );
 
   // set current renderer from layer
   QString rendererName = mLayer->rendererV2()->type();
-  for ( int i = 0; i < cboRenderers->count(); i++ )
-  {
-    if ( cboRenderers->itemData( i ).toString() == rendererName )
-    {
-      cboRenderers->setCurrentIndex( i );
-      return;
-    }
-  }
+
+  int rendererIdx = cboRenderers->findData( rendererName );
+  cboRenderers->setCurrentIndex( rendererIdx );
 
   // no renderer found... this mustn't happen
-  Q_ASSERT( false && "there must be a renderer!" );
-
+  Q_ASSERT( rendererIdx != -1 && "there must be a renderer!" );
 }
 
 QgsRendererV2PropertiesDialog::~QgsRendererV2PropertiesDialog()
@@ -223,6 +238,9 @@ void QgsRendererV2PropertiesDialog::apply()
   if ( renderer )
   {
     renderer->setPaintEffect( mPaintEffect->clone() );
+    // set the order by
+    renderer->setOrderBy( mOrderBy );
+
     mLayer->setRendererV2( renderer->clone() );
   }
 
@@ -240,6 +258,18 @@ void QgsRendererV2PropertiesDialog::onOK()
   accept();
 }
 
+void QgsRendererV2PropertiesDialog::showOrderByDialog()
+{
+  QgsOrderByDialog dlg( mLayer );
+
+  dlg.setOrderBy( mOrderBy );
+  if ( dlg.exec() )
+  {
+    mOrderBy = dlg.orderBy();
+    lineEditOrderBy->setText( mOrderBy.dump() );
+  }
+}
+
 
 void QgsRendererV2PropertiesDialog::keyPressEvent( QKeyEvent * e )
 {

src/gui/symbology-ng/qgsrendererv2propertiesdialog.h

@@ -21,6 +21,8 @@
 
 #include "ui_qgsrendererv2propsdialogbase.h"
 
+#include "qgsfeaturerequest.h"
+
 class QKeyEvent;
 
 class QgsVectorLayer;
@@ -52,6 +54,9 @@ class GUI_EXPORT QgsRendererV2PropertiesDialog : public QDialog, private Ui::Qgs
     void apply();
     void onOK();
 
+  private slots:
+    void showOrderByDialog();
+
   protected:
 
     //! Reimplements dialog keyPress event so we can ignore it
@@ -66,6 +71,8 @@ class GUI_EXPORT QgsRendererV2PropertiesDialog : public QDialog, private Ui::Qgs
     QgsPaintEffect* mPaintEffect;
 
     QgsMapCanvas* mMapCanvas;
+
+    QgsFeatureRequest::OrderBy mOrderBy;
 };
 
 

src/ui/qgsorderbydialogbase.ui

@@ -0,0 +1,89 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>OrderByDialogBase</class>
+ <widget class="QDialog" name="OrderByDialogBase">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>747</width>
+    <height>296</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Define order</string>
+  </property>
+  <layout class="QGridLayout" name="gridLayout">
+   <item row="1" column="0">
+    <widget class="QDialogButtonBox" name="buttonBox">
+     <property name="orientation">
+      <enum>Qt::Horizontal</enum>
+     </property>
+     <property name="standardButtons">
+      <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
+     </property>
+    </widget>
+   </item>
+   <item row="0" column="0">
+    <widget class="QTableWidget" name="mOrderByTableWidget">
+     <property name="selectionMode">
+      <enum>QAbstractItemView::SingleSelection</enum>
+     </property>
+     <property name="selectionBehavior">
+      <enum>QAbstractItemView::SelectRows</enum>
+     </property>
+     <column>
+      <property name="text">
+       <string>Expression</string>
+      </property>
+     </column>
+     <column>
+      <property name="text">
+       <string>Ascending</string>
+      </property>
+     </column>
+     <column>
+      <property name="text">
+       <string>Nulls First</string>
+      </property>
+     </column>
+    </widget>
+   </item>
+  </layout>
+ </widget>
+ <resources/>
+ <connections>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>accepted()</signal>
+   <receiver>OrderByDialogBase</receiver>
+   <slot>accept()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>248</x>
+     <y>254</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>157</x>
+     <y>274</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>rejected()</signal>
+   <receiver>OrderByDialogBase</receiver>
+   <slot>reject()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>316</x>
+     <y>260</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>286</x>
+     <y>274</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
+</ui>

src/ui/qgsrendererv2propsdialogbase.ui

@@ -85,6 +85,16 @@
       <bool>true</bool>
      </property>
      <layout class="QGridLayout" name="gridLayout">
+      <item row="2" column="0" colspan="4">
+       <widget class="QgsEffectStackCompactWidget" name="mEffectWidget" native="true">
+        <property name="minimumSize">
+         <size>
+          <width>16</width>
+          <height>16</height>
+         </size>
+        </property>
+       </widget>
+      </item>
       <item row="0" column="1" colspan="3">
        <layout class="QHBoxLayout" name="horizontalLayout_2">
         <item>
@@ -133,15 +143,30 @@
       <item row="1" column="1">
        <widget class="QgsBlendModeComboBox" name="mBlendModeComboBox"/>
       </item>
-      <item row="2" column="0" colspan="2">
-       <widget class="QgsEffectStackCompactWidget" name="mEffectWidget" native="true">
-        <property name="minimumSize">
-         <size>
-          <width>16</width>
-          <height>16</height>
-         </size>
-        </property>
-       </widget>
+      <item row="3" column="0" colspan="4">
+       <layout class="QHBoxLayout" name="horizontalLayout_3">
+        <item>
+         <widget class="QCheckBox" name="checkboxEnableOrderBy">
+          <property name="text">
+           <string>Control feature rendering order</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QLineEdit" name="lineEditOrderBy">
+          <property name="readOnly">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QToolButton" name="btnOrderBy">
+          <property name="text">
+           <string>...</string>
+          </property>
+         </widget>
+        </item>
+       </layout>
       </item>
      </layout>
     </widget>