Inserting two legends in a QwtPlot with different content

[Momergil]

Hello!

I have a QwtPlot which, instead of plotting curves, will show only items from a class derived from QwtPlotMarker. This markers will be categorized by both color (item family) and symbol (item type).

I need to show two legends in such a graph: one will show the color differentiation and should hide or show its contents when the marker colors are selected in a menu and the other, always fully visible, will show the symbol differentiation. My question is: how to do that?

Two essential problems are being faced here: one is how to add two QwtPlotLegendItem, one at the side of the other and in the same corner of the graph, if the position of such legends are generic ("TopCorner" instead of a move(QPos()) command). If I add two legends to the same spot one would probably go under the other, which is not what I want.

The second problem is how to do such a division in the plots. For the color plot, I imagine that adding some empty QwtPlotCurves with the right Pens and titles and showing them when appropriate would do the trick. But how to make this only appear in just one of the legends? And how could I create and configure the symbol legend? (for this I have no idea on how to do it).


Any help would be appreciated.

Thanks,

Momergil

[Momergil]

No one have a clue? I'm quite in a hurry with this

Btw, the trick with QwtPlotCurves worked just fine. The problem now is really to create the symbol legend.


I appreciate any help,

Momergil

[Uwe]

Two essential problems are being faced here: one is how to add two QwtPlotLegendItem, one at the side of the other and in the same corner of the graph

Overload QwtPlotLegendItem::geometry() and return what you need.

The second problem is how to do such a division in the plots.

virtual void YourLegendItem::updateLegend( const QwtPlotItem *plotItem,
        const QList<QwtLegendData> &data )
{
    if ( plotItem->rtti() == ... )
        return;
 
    QwtPlotLegendItem::updateLegend( plotItem, data );
}

virtual void YourLegendItem::updateLegend( const QwtPlotItem *plotItem,
        const QList<QwtLegendData> &data )
{
    if ( plotItem->rtti() == ... )
        return;

    QwtPlotLegendItem::updateLegend( plotItem, data );
}

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And how could I create and configure the symbol legend?

The plot items are responsible for the information, that is displayed on the legend. Usually it is the title of the item and the icon, that is returned from QwtPlotItem::legendIcon(). But it is also possible to return more information - what is f.e. used by QwtPlotMultiBarChart.

All relevant plot items should offer an implementation of QwtPlotItem::legendIcon(), but the default setting of the QwtPlotItem::Legend flag depends on the type of plot item. For curves it is on, while f.e. for markers you would have to enable it to see them on the legend.

marker->setItemAttribute( QwtPlotItem::Legend, true );

marker->setItemAttribute( QwtPlotItem::Legend, true );

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Uwe