QwtAbstractLegend(3) Abstract base class for legend widgets.


#include <qwt_abstract_legend.h>

Inherits QFrame.

Inherited by QwtLegend.

Public Slots

virtual void updateLegend (const QVariant &itemInfo, const QList< QwtLegendData > &data)=0
Update the entries for a plot item.

Public Member Functions

QwtAbstractLegend (QWidget *parent=NULL)

virtual ~QwtAbstractLegend ()
virtual void renderLegend (QPainter *painter, const QRectF &rect, bool fillBackground) const =0

virtual bool isEmpty () const =0

virtual int scrollExtent (Qt::Orientation) const

Detailed Description

Abstract base class for legend widgets.

Legends, that need to be under control of the QwtPlot layout system need to be derived from QwtAbstractLegend.


Other type of legends can be implemented by connecting to the QwtPlot::legendDataChanged() signal. But as these legends are unknown to the plot layout system the layout code ( on screen and for QwtPlotRenderer ) need to be organized in application code.

See Also:


Constructor & Destructor Documentation

QwtAbstractLegend::QwtAbstractLegend (QWidget *parent = NULL) [explicit]



parent Parent widget

Member Function Documentation

virtual bool QwtAbstractLegend::isEmpty () const [pure virtual]


True, when no plot item is inserted

Implemented in QwtLegend.

virtual void QwtAbstractLegend::renderLegend (QPainter *painter, const QRectF &rect, boolfillBackground) const [pure virtual]

Render the legend into a given rectangle.


painter Painter
rect Bounding rectangle
fillBackground When true, fill rect with the widget background

See Also:

renderLegend() is used by QwtPlotRenderer

Implemented in QwtLegend.

int QwtAbstractLegend::scrollExtent (Qt::Orientationorientation) const [virtual]

Return the extent, that is needed for elements to scroll the legend ( usually scrollbars ),


orientation Orientation


Extent of the corresponding scroll element

Reimplemented in QwtLegend.

virtual void QwtAbstractLegend::updateLegend (const QVariant &itemInfo, const QList< QwtLegendData > &data) [pure virtual], [slot]

Update the entries for a plot item.


itemInfo Info about an item
data List of legend entry attributes for the item


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