/** \ingroup MapComposer
 * A item that forms part of a map composition.
 */
class QgsComposerObject : QObject
{
%TypeHeaderCode
#include <qgscomposerobject.h>
%End

  public:

    /** Data defined properties for different item types
   */
  enum DataDefinedProperty
  {
    NoProperty = 0, /*< no property */
    AllProperties, /*< all properties for item */
    //composer page properties
    PresetPaperSize, /*< preset paper size for composition */
    PaperWidth, /*< paper width */
    PaperHeight, /*< paper height */
    NumPages, /*< number of pages in composition */
    PaperOrientation, /*< paper orientation */
    //general composer item properties
    PageNumber, /*< page number for item placement */
    PositionX, /*< x position on page */
    PositionY, /*< y position on page */
    ItemWidth, /*< width of item */
    ItemHeight, /*< height of item */
    ItemRotation, /*< rotation of item */
    Transparency, /*< item transparency */
    BlendMode, /*< item blend mode */
    //composer map
    MapRotation, /*< map rotation */
    MapScale, /*< map scale */
    MapXMin, /*< map extent x minimum */
    MapYMin, /*< map extent y minimum */
    MapXMax, /*< map extent x maximum */
    MapYMax, /*< map extent y maximum */
    //composer picture
    PictureSource /*< picture source url */
  };

  /** Specifies whether the value returned by a function should be the original, user
   * set value, or the current evaluated value for the property. This may differ if
   * a property has a data defined expression active.
   */
  enum PropertyValueType
  {
    EvaluatedValue = 0, /*< return the current evaluated value for the property */
    OriginalValue /*< return the original, user set value */
  };

    /**Constructor
     * @param composition parent composition
     */
    QgsComposerObject( QgsComposition* composition );
    virtual ~QgsComposerObject();

    /**Returns the composition the item is attached to.
     * @returns QgsComposition for item.
     */
    const QgsComposition* composition() const;

    /**Stores item state in DOM element
     * @param elem is DOM element corresponding to 'Composer' tag
     * @param doc is the DOM document
     */
    virtual bool writeXML( QDomElement& elem, QDomDocument & doc ) const;

    /**Sets item state from DOM element
     * @param itemElem is DOM node corresponding to item tag
     * @param doc is DOM document
     */
    virtual bool readXML( const QDomElement& itemElem, const QDomDocument& doc );

    /**Returns a reference to the data defined settings for one of the item's data defined properties.
     * @param property data defined property to return
     * @note this method was added in version 2.5
    */
    QgsDataDefined* dataDefinedProperty( const DataDefinedProperty property ) const;

    /**Sets parameters for a data defined property for the item
     * @param property data defined property to set
     * @param active true if data defined property is active, false if it is disabled
     * @param useExpression true if the expression should be used
     * @param expression expression for data defined property
     * @field field name if the data defined property should take its value from a field
     * @note this method was added in version 2.5
    */
    void setDataDefinedProperty( const DataDefinedProperty property, const bool active, const bool useExpression, const QString &expression, const QString &field );

  public slots:

    /**Triggers a redraw for the item*/
    virtual void repaint();

    /**Refreshes a data defined property for the item by reevaluating the property's value
     * and redrawing the item with this new value.
     * @param property data defined property to refresh. If property is set to
     * QgsComposerItem::AllProperties then all data defined properties for the item will be
     * refreshed.
     * @note this method was added in version 2.5
    */
    virtual void refreshDataDefinedProperty( const DataDefinedProperty property = AllProperties );


  protected:

    /**Evaluate a data defined property and return the calculated value
     * @returns true if data defined property could be successfully evaluated
     * @param property data defined property to evaluate
     * @param expressionValue QVariant for storing the evaluated value
     * @note this method was added in version 2.5
    */
    bool dataDefinedEvaluate( QgsComposerObject::DataDefinedProperty property, QVariant &expressionValue );

  signals:
    /**Emitted when the item changes. Signifies that the item widgets must update the
     * gui elements.
    */
    void itemChanged();

};