qwt_plot.cpp

  \sa QwtPlotItem::legendData(), legendDataChanged()
 */
void QwtPlot::updateLegend()
{
    const QwtPlotItemList& itmList = itemList();
    for ( QwtPlotItemIterator it = itmList.begin();
        it != itmList.end(); ++it )
    {
        updateLegend( *it );
    }
}

/*!
  Emit legendDataChanged() for a plot item

  \param plotItem Plot item
  \sa QwtPlotItem::legendData(), legendDataChanged()
 */
void QwtPlot::updateLegend( const QwtPlotItem *plotItem )
{
    if ( plotItem == NULL )
        return;

    QList<QwtLegendData> legendData;

    if ( plotItem->testItemAttribute( QwtPlotItem::Legend ) )
        legendData = plotItem->legendData();

    const QVariant itemInfo = itemToInfo( const_cast< QwtPlotItem *>( plotItem) );
    Q_EMIT legendDataChanged( itemInfo, legendData );
}

/*!
  \brief Update all plot items interested in legend attributes

  Call QwtPlotItem::updateLegend(), when the QwtPlotItem::LegendInterest
  flag is set.

  \param itemInfo Info about the plot item
  \param legendData Entries to be displayed for the plot item ( usually 1 )

  \sa QwtPlotItem::LegendInterest,
      QwtPlotLegendItem, QwtPlotItem::updateLegend()
 */
void QwtPlot::updateLegendItems( const QVariant &itemInfo,
    const QList<QwtLegendData> &legendData )
{
    QwtPlotItem *plotItem = infoToItem( itemInfo );
    if ( plotItem )
    {
        const QwtPlotItemList& itmList = itemList();
        for ( QwtPlotItemIterator it = itmList.begin();
            it != itmList.end(); ++it )
        {
            QwtPlotItem *item = *it;
            if ( item->testItemInterest( QwtPlotItem::LegendInterest ) )
                item->updateLegend( plotItem, legendData );
        }
    }
}

/*!
  \brief Attach/Detach a plot item 

  \param plotItem Plot item
  \param on When true attach the item, otherwise detach it
 */
void QwtPlot::attachItem( QwtPlotItem *plotItem, bool on )
{
    if ( plotItem->testItemInterest( QwtPlotItem::LegendInterest ) )
    {
        // plotItem is some sort of legend

        const QwtPlotItemList& itmList = itemList();
        for ( QwtPlotItemIterator it = itmList.begin();
            it != itmList.end(); ++it )
        {
            QwtPlotItem *item = *it;

            QList<QwtLegendData> legendData;
            if ( on && item->testItemAttribute( QwtPlotItem::Legend ) )
            {
                legendData = item->legendData();
                plotItem->updateLegend( item, legendData );
            }
        }
    }

    if ( on )
        insertItem( plotItem );
    else 
        removeItem( plotItem );

    Q_EMIT itemAttached( plotItem, on );

    if ( plotItem->testItemAttribute( QwtPlotItem::Legend ) )
    {
        // the item wants to be represented on the legend

        if ( on )
        {
            updateLegend( plotItem );
        }
        else
        {
            const QVariant itemInfo = itemToInfo( plotItem );
            Q_EMIT legendDataChanged( itemInfo, QList<QwtLegendData>() );
        }
    }

    if ( autoReplot() )
        update();
}

/*!
  \brief Build an information, that can be used to identify
         a plot item on the legend.

  The default implementation simply wraps the plot item
  into a QVariant object. When overloading itemToInfo()
  usually infoToItem() needs to reimplemeted too.

\code
    QVariant itemInfo;
    qVariantSetValue( itemInfo, plotItem );
\endcode

  \param plotItem Plot item
  \return Plot item embedded in a QVariant
  \sa infoToItem()
 */
QVariant QwtPlot::itemToInfo( QwtPlotItem *plotItem ) const
{
    QVariant itemInfo;
    qVariantSetValue( itemInfo, plotItem );

    return itemInfo;
}

/*!
  \brief Identify the plot item according to an item info object,
         that has bee generated from itemToInfo().

  The default implementation simply tries to unwrap a QwtPlotItem 
  pointer:

\code
    if ( itemInfo.canConvert<QwtPlotItem *>() )
        return qvariant_cast<QwtPlotItem *>( itemInfo );
\endcode
  \param itemInfo Plot item
  \return A plot item, when successful, otherwise a NULL pointer.
  \sa itemToInfo()
*/
QwtPlotItem *QwtPlot::infoToItem( const QVariant &itemInfo ) const
{
    if ( itemInfo.canConvert<QwtPlotItem *>() )
        return qvariant_cast<QwtPlotItem *>( itemInfo );

    return NULL;
}