Streamline expression context generation (#3350)

* Save more data to QML * Virtual fields * Map tips * Display expression * Read only flag * Streamline expression context generation Whenever an object is able to generate an expression context it implements the method createExpressionContext() declared in QgsExpressionContextGenerator. This makes a cleaner API and allows using QgsFieldExpressionWidget and QgsDataDefinedButton from python because standard OO programming approaches are used instead of callbacks and void pointers. * Colorize output of doc and sip tests * Fix build * Fix sip complaints * Fix rebase problems * Workaround failing bindings test
qgis · Aug 10, 2016 · 58ea211 · 58ea211 · nyalldawson · Aug 10, 2016
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diff --git a/ci/travis/linux/qt4/before_install.sh b/ci/travis/linux/qt4/before_install.sh
@@ -21,4 +21,4 @@ curl -L https://github.com/opengisch/osgeo4travis/archive/qt4bin.tar.gz | tar -x
 curl -L https://cmake.org/files/v3.5/cmake-3.5.0-Linux-x86_64.tar.gz | tar --strip-components=1 -zxC /home/travis/osgeo4travis
 
 popd
-pip install --user autopep8 nose2 pyyaml mock future
+pip install --user autopep8 nose2 pyyaml mock future termcolor
diff --git a/ci/travis/linux/qt5/before_install.sh b/ci/travis/linux/qt5/before_install.sh
@@ -28,4 +28,4 @@ curl -L https://github.com/opengisch/osgeo4travis/archive/qt5bin.tar.gz | tar -x
 curl -L https://cmake.org/files/v3.5/cmake-3.5.0-Linux-x86_64.tar.gz | tar --strip-components=1 -zxC /home/travis/osgeo4travis
 popd
 
-pip install psycopg2 numpy nose2 pyyaml mock future
+pip install psycopg2 numpy nose2 pyyaml mock future termcolor
diff --git a/doc/api_break.dox b/doc/api_break.dox
@@ -393,6 +393,18 @@ be returned in place of a null pointer.</li>
 QgsExpressionContext variables should be used in their place.</li>
 </ul>
 
+\subsection qgis_api_break_3_0_QgsDataDefinedButton QgsDataDefinedButton
+
+<ul>
+<li>registerGetExpressionContextCallback has been removed in favor of registerExpressionContextGenerator</li>
+</ul>
+
+\subsection qgis_api_break_3_0_QgsFieldExpressionWidget QgsFieldExpressionWidget
+
+<ul>
+<li>registerGetExpressionContextCallback has been removed in favor of registerExpressionContextGenerator</li>
+</ul>
+
 \subsection qgis_api_break_3_0_QgsDataDefinedSymbolDialog QgsDataDefinedSymbolDialog
 
 <ul>

diff --git a/python/core/composer/qgscomposerattributetablev2.sip b/python/core/composer/qgscomposerattributetablev2.sip
@@ -281,5 +281,5 @@ class QgsComposerAttributeTableV2 : QgsComposerTableV2
      */
     bool getTableContents( QgsComposerTableContents &contents );
 
-    virtual QgsExpressionContext* createExpressionContext() const /Factory/;
+    virtual QgsExpressionContext createExpressionContext() const;
 };
diff --git a/python/core/composer/qgscomposerframe.sip b/python/core/composer/qgscomposerframe.sip
@@ -78,5 +78,5 @@ class QgsComposerFrame: QgsComposerItem
      */
     bool isEmpty() const;
 
-    virtual QgsExpressionContext* createExpressionContext() const;
+    virtual QgsExpressionContext createExpressionContext() const;
 };
diff --git a/python/core/composer/qgscomposeritem.sip b/python/core/composer/qgscomposeritem.sip
@@ -645,7 +645,7 @@ class QgsComposerItem : QgsComposerObject, QGraphicsRectItem
      * scopes for global, project, composition, atlas and item properties.
      * @note added in QGIS 2.12
      */
-    QgsExpressionContext* createExpressionContext() const /Factory/;
+    QgsExpressionContext createExpressionContext() const;
 
   public slots:
     /** Sets the item rotation

diff --git a/python/core/composer/qgscomposermap.sip b/python/core/composer/qgscomposermap.sip
@@ -769,7 +769,7 @@ class QgsComposerMap : QgsComposerItem
      * @note added in 2.6 */
     void requestedExtent( QgsRectangle& extent ) const;
 
-    virtual QgsExpressionContext* createExpressionContext() const;
+    virtual QgsExpressionContext createExpressionContext() const;
 
   signals:
     void extentChanged();

diff --git a/python/core/composer/qgscomposermapgrid.sip b/python/core/composer/qgscomposermapgrid.sip
@@ -796,6 +796,6 @@ class QgsComposerMapGrid : QgsComposerMapItem
      */
     QColor frameFillColor2() const;
 
-    virtual QgsExpressionContext* createExpressionContext() const;
+    virtual QgsExpressionContext createExpressionContext() const;
 
 };
diff --git a/python/core/composer/qgscomposerobject.sip b/python/core/composer/qgscomposerobject.sip
@@ -142,7 +142,7 @@ class QgsComposerObject : QObject
      * scopes for global, project and composition properties.
      * @note added in QGIS 2.12
      */
-    virtual QgsExpressionContext* createExpressionContext() const /Factory/;
+    virtual QgsExpressionContext createExpressionContext() const;
 
   public slots:
 

diff --git a/python/core/composer/qgscomposition.sip b/python/core/composer/qgscomposition.sip
@@ -845,7 +845,7 @@ class QgsComposition : QGraphicsScene
      * scopes for global, project, composition and atlas properties.
      * @note added in QGIS 2.12
      */
-    QgsExpressionContext* createExpressionContext() const;
+    QgsExpressionContext createExpressionContext() const;
 
   protected:
     void init();

diff --git a/python/core/core.sip b/python/core/core.sip
@@ -49,6 +49,7 @@
 %Include qgserror.sip
 %Include qgsexpression.sip
 %Include qgsexpressioncontext.sip
+%Include qgsexpressioncontextgenerator.sip
 %Include qgsfeature.sip
 %Include qgsfeaturefilterprovider.sip
 %Include qgsfeatureiterator.sip

diff --git a/python/core/qgsexpressioncontextgenerator.sip b/python/core/qgsexpressioncontextgenerator.sip
@@ -0,0 +1,41 @@
+/***************************************************************************
+  qgsexpressioncontextgenerator.sip - QgsExpressionContextGenerator
+
+ ---------------------
+ begin                : 1.8.2016
+ copyright            : (C) 2016 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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+/**
+ * \ingroup core
+ * Abstract interface for generating an expression context.
+ *
+ * You need to implement this interface in a class and register this class with
+ * QgsFieldExpressionWidget::registerExpressionGenerator().
+ *
+ * Whenever this widget requires an expression context it will call the createExpressionContext()
+ * method to get a context.
+ *
+ * @note added in QGIS 3.0
+ */
+
+class QgsExpressionContextGenerator
+{
+%TypeHeaderCode
+#include "qgsexpressioncontextgenerator.h"
+%End
+
+  public:
+    /**
+     * This method needs to be reimplemented in all classes which implement this interface
+     * and return an expression context.
+     */
+    virtual QgsExpressionContext createExpressionContext() const = 0;
+};
diff --git a/python/core/qgsproject.sip b/python/core/qgsproject.sip
@@ -324,6 +324,8 @@ class QgsProject : QObject
      */
     void setEvaluateDefaultValues( bool evaluateDefaultValues );
 
+    QgsExpressionContext createExpressionContext() const;
+
   protected:
 
     /** Set error message from read/write operation

diff --git a/python/core/qgsvectorlayer.sip b/python/core/qgsvectorlayer.sip
@@ -1385,6 +1385,8 @@ class QgsVectorLayer : QgsMapLayer
      */
     void setMapTipTemplate( const QString& mapTipTemplate );
 
+    QgsExpressionContext createExpressionContext() const;
+
   public slots:
     /**
      * Select feature by its ID

diff --git a/python/gui/qgsdatadefinedbutton.sip b/python/gui/qgsdatadefinedbutton.sip
@@ -185,17 +185,14 @@ class QgsDataDefinedButton : QToolButton
      */
     void clearCheckedWidgets();
 
-    //! Callback function for retrieving the expression context for the button
-    //typedef QgsExpressionContext( *ExpressionContextCallback )( const void* context );
-
-    /** Register callback function for retrieving the expression context for the button
-     * @param fnGetExpressionContext call back function, will be called when the data defined
-     * button requires the current expression context
-     * @param context context for callback function
-     * @note added in QGIS 2.12
-     * @note not available in Python bindings
+    /**
+     * Register an expression context generator class that will be used to retrieve
+     * an expression context for the button.
+     * @param generator A QgsExpressionContextGenerator class that will be used to
+     *                  create an expression context when required.
+     * @note added in QGIS 3.0
      */
-    //void registerGetExpressionContextCallback( ExpressionContextCallback fnGetExpressionContext, const void* context );
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator* generator );
 
     /**
      * Sets an assistant used to define the data defined object properties.

diff --git a/python/gui/qgsfieldexpressionwidget.sip b/python/gui/qgsfieldexpressionwidget.sip
@@ -56,17 +56,14 @@ class QgsFieldExpressionWidget : QWidget
     //! Returns the currently used layer
     QgsVectorLayer* layer() const;
 
-    //! Callback function for retrieving the expression context for the expression
-    //typedef QgsExpressionContext( *ExpressionContextCallback )( const void* context );
-
-    /** Register callback function for retrieving the expression context for the expression
-     * @param fnGetExpressionContext call back function, will be called when the widget requires
-     * the current expression context
-     * @param context context for callback function
-     * @note added in QGIS 2.12
-     * @note not available in Python bindings
+    /**
+     * Register an expression context generator class that will be used to retrieve
+     * an expression context for the widget.
+     * @param generator A QgsExpressionContextGenerator class that will be used to
+     *                  create an expression context when required.
+     * @note added in QGIS 3.0
      */
-    //void registerGetExpressionContextCallback( ExpressionContextCallback fnGetExpressionContext, const void* context );
+    void registerExpressionContextGenerator( QgsExpressionContextGenerator* generator );
 
   signals:
     //! the signal is emitted when the currently selected field changes

diff --git a/python/gui/symbology-ng/qgsrendererwidget.sip b/python/gui/symbology-ng/qgsrendererwidget.sip
@@ -122,9 +122,15 @@ class QgsDataDefinedValueDialog : QDialog
     void dataDefinedChanged();
 
   protected:
-    QgsDataDefined symbolDataDefined() const;
+    /**
+     * Should be called in the constructor of child classes.
+     *
+     * @note May be missing Python bindings depending on the platform.
+     */
     void init( const QString& description ); // needed in children ctor to call virtual
 
+  private:
+    QgsDataDefined symbolDataDefined() const;
     virtual QgsDataDefined symbolDataDefined( const QgsSymbol* ) const = 0;
     virtual double value( const QgsSymbol* ) const = 0;
     virtual void setDataDefined( QgsSymbol* symbol, const QgsDataDefined& dd ) = 0;

diff --git a/python/gui/symbology-ng/qgssymbollayerwidget.sip b/python/gui/symbology-ng/qgssymbollayerwidget.sip
@@ -51,15 +51,9 @@ class QgsSymbolLayerWidget : QWidget
     void setExpressionContext( QgsExpressionContext* context );
 
   protected:
+    void registerDataDefinedButton( QgsDataDefinedButton* button, const QString& propertyName, QgsDataDefinedButton::DataType type, const QString& description );
 
-    void registerDataDefinedButton( QgsDataDefinedButton * button, const QString & propertyName, QgsDataDefinedButton::DataType type, const QString & description );
-
-    /** Get label for data defined entry.
-     * Implemented only for 'size' of marker symbols
-     * @note added in 2.1
-     * @deprecated no longer used
-     */
-    virtual QString dataDefinedPropertyLabel( const QString &entryName ) /Deprecated/;
+    QgsExpressionContext createExpressionContext() const;
 
   signals:
     /**

diff --git a/python/gui/symbology-ng/qgssymbolslistwidget.sip b/python/gui/symbology-ng/qgssymbolslistwidget.sip
@@ -68,10 +68,4 @@ class QgsSymbolsListWidget : QWidget
 
   signals:
     void changed();
-
-  protected:
-    void populateSymbolView();
-    void populateSymbols( const QStringList& symbols );
-    void updateSymbolColor();
-    void updateSymbolInfo();
 };
diff --git a/src/app/composer/qgsatlascompositionwidget.cpp b/src/app/composer/qgsatlascompositionwidget.cpp
@@ -26,18 +26,6 @@
 #include "qgscomposermap.h"
 #include "qgsvectorlayer.h"
 
-static QgsExpressionContext _getExpressionContext( const void* context )
-{
-  const QgsComposition* composition = ( const QgsComposition* ) context;
-  if ( !composition )
-  {
-    return QgsExpressionContext();
-  }
-
-  QScopedPointer< QgsExpressionContext > expContext( composition->createExpressionContext() );
-  return QgsExpressionContext( *expContext );
-}
-
 QgsAtlasCompositionWidget::QgsAtlasCompositionWidget( QWidget* parent, QgsComposition* c ):
     QWidget( parent ), mComposition( c )
 {
@@ -58,7 +46,7 @@ QgsAtlasCompositionWidget::QgsAtlasCompositionWidget( QWidget* parent, QgsCompos
   // connect to updates
   connect( &mComposition->atlasComposition(), SIGNAL( parameterChanged() ), this, SLOT( updateGuiElements() ) );
 
-  mPageNameWidget->registerGetExpressionContextCallback( &_getExpressionContext, mComposition );
+  mPageNameWidget->registerExpressionContextGenerator( mComposition );
 
   updateGuiElements();
 }
@@ -133,8 +121,8 @@ void QgsAtlasCompositionWidget::on_mAtlasFilenameExpressionButton_clicked()
     return;
   }
 
-  QScopedPointer<QgsExpressionContext> context( mComposition->createExpressionContext() );
-  QgsExpressionBuilderDialog exprDlg( atlasMap->coverageLayer(), mAtlasFilenamePatternEdit->text(), this, "generic", *context );
+  QgsExpressionContext context = mComposition->createExpressionContext();
+  QgsExpressionBuilderDialog exprDlg( atlasMap->coverageLayer(), mAtlasFilenamePatternEdit->text(), this, "generic", context );
   exprDlg.setWindowTitle( tr( "Expression based filename" ) );
 
   if ( exprDlg.exec() == QDialog::Accepted )
@@ -306,8 +294,8 @@ void QgsAtlasCompositionWidget::on_mAtlasFeatureFilterButton_clicked()
     return;
   }
 
-  QScopedPointer<QgsExpressionContext> context( mComposition->createExpressionContext() );
-  QgsExpressionBuilderDialog exprDlg( vl, mAtlasFeatureFilterEdit->text(), this, "generic", *context );
+  QgsExpressionContext context = mComposition->createExpressionContext();
+  QgsExpressionBuilderDialog exprDlg( vl, mAtlasFeatureFilterEdit->text(), this, "generic", context );
   exprDlg.setWindowTitle( tr( "Expression based filter" ) );
 
   if ( exprDlg.exec() == QDialog::Accepted )

diff --git a/src/app/composer/qgsattributeselectiondialog.cpp b/src/app/composer/qgsattributeselectiondialog.cpp
@@ -99,18 +99,17 @@ QgsComposerColumnSourceDelegate::QgsComposerColumnSourceDelegate( QgsVectorLayer
 
 }
 
-static QgsExpressionContext _getExpressionContext( const void* context )
+QgsExpressionContext QgsComposerColumnSourceDelegate::createExpressionContext() const
 {
-  const QgsComposerObject* object = ( const QgsComposerObject* ) context;
-  if ( !object )
+  if ( !mComposerObject )
   {
     return QgsExpressionContext();
   }
 
-  QScopedPointer< QgsExpressionContext > expContext( object->createExpressionContext() );
-  expContext->lastScope()->setVariable( "row_number", 1 );
-  expContext->setHighlightedVariables( QStringList() << "row_number" );
-  return QgsExpressionContext( *expContext );
+  QgsExpressionContext expContext = mComposerObject->createExpressionContext();
+  expContext.lastScope()->setVariable( "row_number", 1 );
+  expContext.setHighlightedVariables( QStringList() << "row_number" );
+  return expContext;
 }
 
 QWidget* QgsComposerColumnSourceDelegate::createEditor( QWidget* parent, const QStyleOptionViewItem& option, const QModelIndex& index ) const
@@ -120,7 +119,7 @@ QWidget* QgsComposerColumnSourceDelegate::createEditor( QWidget* parent, const Q
 
   QgsFieldExpressionWidget *fieldExpression = new QgsFieldExpressionWidget( parent );
   fieldExpression->setLayer( mVectorLayer );
-  fieldExpression->registerGetExpressionContextCallback( &_getExpressionContext, mComposerObject );
+  fieldExpression->registerExpressionContextGenerator( this );
 
   //listen out for field changes
   connect( fieldExpression, SIGNAL( fieldChanged( QString ) ), this, SLOT( commitAndCloseEditor() ) );

diff --git a/src/app/composer/qgsattributeselectiondialog.h b/src/app/composer/qgsattributeselectiondialog.h
@@ -23,6 +23,7 @@
 #include <QSet>
 #include <QItemDelegate>
 #include "ui_qgsattributeselectiondialogbase.h"
+#include "qgsexpressioncontextgenerator.h"
 
 class QGridLayout;
 class QgsVectorLayer;
@@ -56,7 +57,7 @@ class QgsComposerColumnAlignmentDelegate : public QItemDelegate
 // QgsComposerColumnAlignmentDelegate
 
 /** A delegate for showing column attribute source as a QgsFieldExpressionWidget*/
-class QgsComposerColumnSourceDelegate : public QItemDelegate
+class QgsComposerColumnSourceDelegate : public QItemDelegate, private QgsExpressionContextGenerator
 {
     Q_OBJECT
 
@@ -71,6 +72,7 @@ class QgsComposerColumnSourceDelegate : public QItemDelegate
   private:
     QgsVectorLayer* mVectorLayer;
     const QgsComposerObject* mComposerObject;
+    QgsExpressionContext createExpressionContext() const override;
 };
 
 // QgsComposerColumnWidthDelegate

diff --git a/src/app/composer/qgscomposerarrowwidget.cpp b/src/app/composer/qgscomposerarrowwidget.cpp
@@ -311,7 +311,8 @@ void QgsComposerArrowWidget::on_mLineStyleButton_clicked()
 
   QgsLineSymbol* newSymbol = mArrow->lineSymbol()->clone();
   QgsSymbolSelectorDialog d( newSymbol, QgsStyle::defaultStyle(), nullptr, this );
-  d.setExpressionContext( mArrow->createExpressionContext() );
+  QgsExpressionContext context = mArrow->createExpressionContext();
+  d.setExpressionContext( &context );
 
   if ( d.exec() == QDialog::Accepted )
   {

diff --git a/src/app/composer/qgscomposerattributetablewidget.cpp b/src/app/composer/qgscomposerattributetablewidget.cpp
@@ -741,8 +741,8 @@ void QgsComposerAttributeTableWidget::on_mFeatureFilterButton_clicked()
     return;
   }
 
-  QScopedPointer<QgsExpressionContext> context( mComposerTable->createExpressionContext() );
-  QgsExpressionBuilderDialog exprDlg( mComposerTable->sourceLayer(), mFeatureFilterEdit->text(), this, "generic", *context );
+  QgsExpressionContext context = mComposerTable->createExpressionContext();
+  QgsExpressionBuilderDialog exprDlg( mComposerTable->sourceLayer(), mFeatureFilterEdit->text(), this, "generic", context );
   exprDlg.setWindowTitle( tr( "Expression based filter" ) );
   if ( exprDlg.exec() == QDialog::Accepted )
   {