Add method for highlighting variables in the expression builder

python/core/qgsexpressioncontext.sip

@@ -221,6 +221,21 @@ class QgsExpressionContext
      */
     QVariant variable( const QString& name ) const;
 
+    /** Returns true if the specified variable name is intended to be highlighted to the
+     * user. This is used by the expression builder to more prominently display the
+     * variable.
+     * @param name variable name
+     * @see setHighlightedVariables()
+     */
+    bool isHighlightedVariable( const QString& name ) const;
+
+    /** Sets the list of variable names within the context intended to be highlighted to the user. This
+     * is used by the expression builder to more prominently display these variables.
+     * @param variableNames variable names to highlight
+     * @see isHighlightedVariable()
+     */
+    void setHighlightedVariables( const QStringList& variableNames );
+
     /** Returns the currently active scope from the context for a specified variable name.
      * As scopes later in the stack override earlier contexts, this will be the last matching
      * scope which contains a matching variable.

python/gui/qgsexpressionbuilderwidget.sip

@@ -121,10 +121,12 @@ class QgsExpressionBuilderWidget : QWidget
       * @param expressionText The text that is inserted into the expression area when the user double clicks on the item.
       * @param helpText The help text that the user will see when item is selected.
       * @param type The type of the expression item.
+      * @param highlightedItem set to true to make the item highlighted, which inserts a bold copy of the item at the top level
       */
     void registerItem( QString group, QString label, QString expressionText,
                        QString helpText = "",
-                       QgsExpressionItem::ItemType type = QgsExpressionItem::ExpressionNode );
+                       QgsExpressionItem::ItemType type = QgsExpressionItem::ExpressionNode,
+                       bool highlightedItem = false );
 
     bool isExpressionValid();
 

src/core/qgsexpressioncontext.cpp

@@ -158,6 +158,7 @@ QgsExpressionContext::QgsExpressionContext( const QgsExpressionContext& other )
   {
     mStack << new QgsExpressionContextScope( *scope );
   }
+  mHighlightedVariables = other.mHighlightedVariables;
 }
 
 QgsExpressionContext& QgsExpressionContext::operator=( const QgsExpressionContext & other )
@@ -168,6 +169,7 @@ QgsExpressionContext& QgsExpressionContext::operator=( const QgsExpressionContex
   {
     mStack << new QgsExpressionContextScope( *scope );
   }
+  mHighlightedVariables = other.mHighlightedVariables;
   return *this;
 }
 
@@ -193,6 +195,16 @@ QVariant QgsExpressionContext::variable( const QString& name ) const
   return scope ? scope->variable( name ) : QVariant();
 }
 
+bool QgsExpressionContext::isHighlightedVariable( const QString &name ) const
+{
+  return mHighlightedVariables.contains( name );
+}
+
+void QgsExpressionContext::setHighlightedVariables( const QStringList& variableNames )
+{
+  mHighlightedVariables = variableNames;
+}
+
 const QgsExpressionContextScope* QgsExpressionContext::activeScopeForVariable( const QString& name ) const
 {
   //iterate through stack backwards, so that higher priority variables take precedence

src/core/qgsexpressioncontext.h

@@ -252,6 +252,21 @@ class CORE_EXPORT QgsExpressionContext
      */
     QVariant variable( const QString& name ) const;
 
+    /** Returns true if the specified variable name is intended to be highlighted to the
+     * user. This is used by the expression builder to more prominently display the
+     * variable.
+     * @param name variable name
+     * @see setHighlightedVariables()
+     */
+    bool isHighlightedVariable( const QString& name ) const;
+
+    /** Sets the list of variable names within the context intended to be highlighted to the user. This
+     * is used by the expression builder to more prominently display these variables.
+     * @param variableNames variable names to highlight
+     * @see isHighlightedVariable()
+     */
+    void setHighlightedVariables( const QStringList& variableNames );
+
     /** Returns the currently active scope from the context for a specified variable name.
      * As scopes later in the stack override earlier contexts, this will be the last matching
      * scope which contains a matching variable.
@@ -373,6 +388,7 @@ class CORE_EXPORT QgsExpressionContext
   private:
 
     QList< QgsExpressionContextScope* > mStack;
+    QStringList mHighlightedVariables;
 
 };
 

src/gui/qgsexpressionbuilderwidget.cpp

@@ -336,10 +336,11 @@ void QgsExpressionBuilderWidget::registerItem( QString group,
     QString label,
     QString expressionText,
     QString helpText,
-    QgsExpressionItem::ItemType type )
+    QgsExpressionItem::ItemType type, bool highlightedItem )
 {
   QgsExpressionItem* item = new QgsExpressionItem( label, expressionText, helpText, type );
   item->setData( label, Qt::UserRole );
+
   // Look up the group and insert the new function.
   if ( mExpressionGroups.contains( group ) )
   {
@@ -355,6 +356,18 @@ void QgsExpressionBuilderWidget::registerItem( QString group,
     mModel->appendRow( newgroupNode );
     mExpressionGroups.insert( group, newgroupNode );
   }
+
+  if ( highlightedItem )
+  {
+    //insert a copy as a top level item
+    QgsExpressionItem* topLevelItem = new QgsExpressionItem( label, expressionText, helpText, type );
+    topLevelItem->setData( label, Qt::UserRole );
+    QFont font = topLevelItem->font();
+    font.setBold( true );
+    topLevelItem->setFont( font );
+    mModel->appendRow( topLevelItem );
+  }
+
 }
 
 bool QgsExpressionBuilderWidget::isExpressionValid()
@@ -581,7 +594,10 @@ void QgsExpressionBuilderWidget::loadExpressionContext()
   QStringList variableNames = mExpressionContext.filteredVariableNames();
   Q_FOREACH ( QString variable, variableNames )
   {
-    registerItem( "Variables", variable, " @" + variable + " ", QgsExpression::variableHelpText( variable, true, mExpressionContext.variable( variable ) ) );
+    registerItem( "Variables", variable, " @" + variable + " ",
+                  QgsExpression::variableHelpText( variable, true, mExpressionContext.variable( variable ) ),
+                  QgsExpressionItem::ExpressionNode,
+                  mExpressionContext.isHighlightedVariable( variable ) );
   }
 
   // Load the functions from the expression context

src/gui/qgsexpressionbuilderwidget.h

@@ -163,10 +163,12 @@ class GUI_EXPORT QgsExpressionBuilderWidget : public QWidget, private Ui::QgsExp
       * @param expressionText The text that is inserted into the expression area when the user double clicks on the item.
       * @param helpText The help text that the user will see when item is selected.
       * @param type The type of the expression item.
+      * @param highlightedItem set to true to make the item highlighted, which inserts a bold copy of the item at the top level
       */
     void registerItem( QString group, QString label, QString expressionText,
                        QString helpText = "",
-                       QgsExpressionItem::ItemType type = QgsExpressionItem::ExpressionNode );
+                       QgsExpressionItem::ItemType type = QgsExpressionItem::ExpressionNode,
+                       bool highlightedItem = false );
 
     bool isExpressionValid();