A suggestion about QwtPlotLegendItem

[Nicho]

Hi Uwe,
I am using QWT6.1 - Downloaded at 20130630.
In my application, it's required to refresh the legend item when the data is changed and I found that :

In the updateLegend() of QwtPlotLegendItem, the layoutItems does not be cleared at each time.
So the list length will be longer and longer, and not be equal to the count of actual items.
eg.
updateLegend( plotItem, dataOfSize1 );
updateLegend( plotItem, dataOfSize2 );
updateLegend( plotItem, dataOfSize1 );
then at the third call of updateLegend(), it will crash.

The codes are like below.

Hope this information is useful.
Nicho

void QwtPlotLegendItem::updateLegend( const QwtPlotItem *plotItem,
        const QList<QwtLegendData> &data )
{
    if ( plotItem == NULL )
        return;
 
    QList<QwtLegendLayoutItem *> layoutItems;
 
    QMap<const QwtPlotItem *, QList<QwtLegendLayoutItem *> >::iterator it = 
        d_data->map.find( plotItem );
    if ( it != d_data->map.end() )
        layoutItems = it.value();
 
    bool changed = false;
 
    if ( data.size() != layoutItems.size() )
    {
        changed = true;
 
        for ( int i = 0; i < layoutItems.size(); i++ )
        {
            d_data->layout->removeItem( layoutItems[i] );
            delete layoutItems[i];//app may crash here.
        }
        layoutItems.clear();//suggestion      
        if ( it != d_data->map.end() )
            d_data->map.remove( plotItem );
 
        if ( !data.isEmpty() )
        {
            for ( int i = 0; i < data.size(); i++ )
            {
                QwtLegendLayoutItem *layoutItem = 
                    new QwtLegendLayoutItem( this, plotItem );
                d_data->layout->addItem( layoutItem );
                layoutItems += layoutItem;
            }
 
            d_data->map.insert( plotItem, layoutItems );
        }
    }
 
    for ( int i = 0; i < data.size(); i++ )
    {
        if ( layoutItems[i]->data().values() != data[i].values() )
        {
            layoutItems[i]->setData( data[i] );
            changed = true;
        }
    }
 
    if ( changed )
    {
        d_data->layout->invalidate();
        itemChanged();
    }
}

void QwtPlotLegendItem::updateLegend( const QwtPlotItem *plotItem,
        const QList<QwtLegendData> &data )
{
    if ( plotItem == NULL )
        return;

    QList<QwtLegendLayoutItem *> layoutItems;

    QMap<const QwtPlotItem *, QList<QwtLegendLayoutItem *> >::iterator it = 
        d_data->map.find( plotItem );
    if ( it != d_data->map.end() )
        layoutItems = it.value();

    bool changed = false;

    if ( data.size() != layoutItems.size() )
    {
        changed = true;

        for ( int i = 0; i < layoutItems.size(); i++ )
        {
            d_data->layout->removeItem( layoutItems[i] );
            delete layoutItems[i];//app may crash here.
        }
        layoutItems.clear();//suggestion      
        if ( it != d_data->map.end() )
            d_data->map.remove( plotItem );

        if ( !data.isEmpty() )
        {
            for ( int i = 0; i < data.size(); i++ )
            {
                QwtLegendLayoutItem *layoutItem = 
                    new QwtLegendLayoutItem( this, plotItem );
                d_data->layout->addItem( layoutItem );
                layoutItems += layoutItem;
            }

            d_data->map.insert( plotItem, layoutItems );
        }
    }

    for ( int i = 0; i < data.size(); i++ )
    {
        if ( layoutItems[i]->data().values() != data[i].values() )
        {
            layoutItems[i]->setData( data[i] );
            changed = true;
        }
    }

    if ( changed )
    {
        d_data->layout->invalidate();
        itemChanged();
    }
}

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