class QgsDataDefinedButton :  QToolButton
{
%TypeHeaderCode
#include <qgsdatadefinedbutton.h>
%End
  public:
    enum DataType
    {
      AnyType,
      String,
      Int,
      Double,
    };
    typedef QFlags<QgsDataDefinedButton::DataType> DataTypes;

    /**
     * Construct a new data defined button
     *
     * @param parent The parent QWidget
     * @param vl Pointer to the associated vector layer
     * @param datadefined Data defined property
     * @param datatypes The expected data types to be compared against the variant type of the QgsField from data source and expression result
     * @param description The description of expected input data
     */
    QgsDataDefinedButton( QWidget* parent = 0,
                          const QgsVectorLayer* vl = 0,
                          const QgsDataDefined* datadefined = 0,
                          DataTypes datatypes = AnyType,
                          QString description = "" );
    ~QgsDataDefinedButton();

    /**
     * Initialize a newly constructed data defined button (useful if button already included from form layout)
     *
     * @param vl Pointer to the associated vector layer
     * @param datadefined Data defined property
     * @param datatypes The expected data types to be compared against the variant type of the QgsField from data source and expression result
     * @param description The description of expected input data
     */
    void init( const QgsVectorLayer* vl,
               const QgsDataDefined* datadefined = 0,
               DataTypes datatypes = AnyType,
               QString description = QString( "" ) );

    QMap< QString, QString > definedProperty() const;

    /**
     * Whether the current data definition or expression is to be used
     */
    bool isActive();

    /**
     * Whether the current expression is to be used instead of field mapping
     */
    bool useExpression();

    /**
     * The current defined expression
     */
    QString getExpression() const;

    /**
     * The current defined field
     */
    QString getField() const;

    /**
     * The current definition
     * @returns empty QString if not active, otherwise currently defined expression or field name
     */
    QString currentDefinition() const;

    /**
     * The valid data types that will work for the definition (QVariant-coercible to expected type)
     * Compared against the variant type of the QgsField from data source and expression result
     */
    const DataTypes& validDataTypes() const;

    /**
     * The full definition description and current definition (internally generated on a contextual basis)
     */
    QString fullDescription() const;

    /**
     * The usage information about this data definition
     */
    QString usageInfo() const;

    /**
     * Set the usage information about this data definition
     */
    void setUsageInfo( const QString& info );

    /**
     * Register list of sibling widgets that get disabled/enabled when data definition or expression is set/unset
     */
    void registerEnabledWidgets( QList<QWidget*> wdgts );

    /**
     * Register a sibling widget that gets disabled/enabled when data definition or expression is set/unset
     */
    void registerEnabledWidget( QWidget* wdgt );

    /**
     * Return widget siblings that get disabled/enabled when data definition or expression is set/unset
     *
     * @return unguarded pointers from guarded ones
     */
    QList<QWidget*> registeredEnabledWidgets();

    /**
     * Clears list of sibling widgets
     */
    void clearEnabledWidgets();

    /**
     * Register list of sibling widgets that get checked when data definition or expression is active
     */
    void registerCheckedWidgets( QList<QWidget*> wdgts );

    /**
     * Register a sibling widget that get checked when data definition or expression is active
     */
    void registerCheckedWidget( QWidget* wdgt );

    /**
     * Return widget siblings that get checked when data definition or expression is active
     *
     * @return unguarded pointers from guarded ones
     */
    QList<QWidget*> registeredCheckedWidgets();

    /**
     * Clears list of checkable sibling widgets
     */
    void clearCheckedWidgets();

    /**
     * Common descriptions for expected input values
     */
    static QString trString();
    static QString boolDesc();
    static QString anyStringDesc();
    static QString intDesc();
    static QString intPosDesc();
    static QString intPosOneDesc();
    static QString doubleDesc();
    static QString doublePosDesc();
    static QString doubleXYDesc();
    static QString double180RotDesc();
    static QString intTranspDesc();
    static QString unitsMmMuDesc();
    static QString unitsMmMuPercentDesc();
    static QString colorNoAlphaDesc();
    static QString colorAlphaDesc();
    static QString textHorzAlignDesc();
    static QString textVertAlignDesc();
    static QString penJoinStyleDesc();
    static QString blendModesDesc();
    static QString svgPathDesc();

  public slots:
    /**
     * Set whether the current data definition or expression is to be used
     */
    void setActive( bool active );

    /**
     * Set siblings' enabled property when data definition or expression is set/unset
     */
    void disableEnabledWidgets( bool disable );

    /**
     * Set siblings' checked property when data definition or expression is active
     */
    void checkCheckedWidgets( bool check );

  signals:
    /**
     * Emitted when data definition or expression is changed
     * @param definition The current definition or expression (empty string if inactive)
     */
    void dataDefinedChanged( const QString& definition );

    /**
     * Emitted when active state changed
     * @param active Whether the definition is active
     */
    void dataDefinedActivated( bool active );

  protected:
    void mouseReleaseEvent( QMouseEvent *event );

    /**
     * Set whether the current expression is to be used instead of field mapping
     */
    void setUseExpression( bool use );

    /**
     * Set the current defined expression
     */
    void setExpression( QString exp );

    /**
     * Set the current defined field
     */
    void setField( QString field );

};