Qwt User's Guide: QwtPlotLegendItem Class Reference

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QwtPlotLegendItem Class Reference

A class which draws a legend inside the plot canvas. More...

`#include <qwt_plot_legenditem.h>`

Inheritance diagram for QwtPlotLegendItem:
[legend]

## Public Types
enum | BackgroundMode { LegendBackground, ItemBackground }
| Background mode. More...
Public Types inherited from QwtPlotItem
enum | RttiValues { Rtti_PlotItem = 0, Rtti_PlotGrid, Rtti_PlotScale, Rtti_PlotLegend, Rtti_PlotMarker, Rtti_PlotCurve, Rtti_PlotSpectroCurve, Rtti_PlotIntervalCurve, Rtti_PlotHistogram, Rtti_PlotSpectrogram, Rtti_PlotSVG, Rtti_PlotTradingCurve, Rtti_PlotBarChart, Rtti_PlotMultiBarChart, Rtti_PlotShape, Rtti_PlotTextLabel, Rtti_PlotZone, Rtti_PlotUserItem = 1000 }
| Runtime type information. More...
enum | ItemAttribute { Legend = 0x01, AutoScale = 0x02, Margins = 0x04 }
| Plot Item Attributes. More...
enum | ItemInterest { ScaleInterest = 0x01, LegendInterest = 0x02 }
| Plot Item Interests. More...
enum | RenderHint { RenderAntialiased = 0x1 }
| Render hints. More...
typedef QFlags< ItemAttribute > | ItemAttributes
| Plot Item Attributes.
typedef QFlags< ItemInterest > | ItemInterests
| Plot Item Interests.
typedef QFlags< RenderHint > | RenderHints
| Render hints.

## Public Member Functions
| QwtPlotLegendItem ()
| Constructor.
virtual | ~QwtPlotLegendItem ()
| Destructor.
virtual int | rtti () const
void | setAlignment (Qt::Alignment)
| Set the alignmnet. More...
Qt::Alignment | alignment () const
void | setMaxColumns (uint)
| Limit the number of columns. More...
uint | maxColumns () const
void | setMargin (int)
| Set the margin around legend items. More...
int | margin () const
void | setSpacing (int)
| Set the spacing between the legend items. More...
int | spacing () const
void | setItemMargin (int)
int | itemMargin () const
void | setItemSpacing (int)
int | itemSpacing () const
void | setFont (const QFont &)
QFont | font () const
void | setBorderDistance (int numPixels)
| Set the margin between the legend and the canvas border. More...
int | borderDistance () const
void | setBorderRadius (double)
double | borderRadius () const
void | setBorderPen (const QPen &)
QPen | borderPen () const
void | setBackgroundBrush (const QBrush &)
| Set the background brush. More...
QBrush | backgroundBrush () const
void | setBackgroundMode (BackgroundMode)
| Set the background mode. More...
BackgroundMode | backgroundMode () const
void | setTextPen (const QPen &)
| Set the pen for drawing text labels. More...
QPen | textPen () const
virtual void | draw (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &rect) const
void | clearLegend ()
| Remove all items from the legend.
virtual void | updateLegend (const QwtPlotItem *, const QList< QwtLegendData > &)
virtual QRect | geometry (const QRectF &canvasRect) const
virtual QSize | minimumSize (const QwtLegendData &) const
virtual int | heightForWidth (const QwtLegendData &, int w) const
QList< const QwtPlotItem * > | plotItems () const
QList< QRect > | legendGeometries (const QwtPlotItem *) const
Public Member Functions inherited from QwtPlotItem
| QwtPlotItem (const QwtText &title=QwtText())
virtual | ~QwtPlotItem ()
| Destroy the QwtPlotItem.
void | attach (QwtPlot *plot)
| Attach the item to a plot. More...
void | detach ()
| This method detaches a QwtPlotItem from any QwtPlot it has been associated with. More...
QwtPlot * | plot () const
| Return attached plot.
void | setTitle (const QString &title)
void | setTitle (const QwtText &title)
const QwtText & | title () const
void | setItemAttribute (ItemAttribute, bool on=true)
bool | testItemAttribute (ItemAttribute) const
void | setItemInterest (ItemInterest, bool on=true)
bool | testItemInterest (ItemInterest) const
void | setRenderHint (RenderHint, bool on=true)
bool | testRenderHint (RenderHint) const
void | setRenderThreadCount (uint numThreads)
uint | renderThreadCount () const
void | setLegendIconSize (const QSize &)
QSize | legendIconSize () const
double | z () const
void | setZ (double z)
| Set the z value. More...
void | show ()
| Show the item.
void | hide ()
| Hide the item.
virtual void | setVisible (bool)
bool | isVisible () const
void | setAxes (int xAxis, int yAxis)
void | setXAxis (int axis)
int | xAxis () const
| Return xAxis.
void | setYAxis (int axis)
int | yAxis () const
| Return yAxis.
virtual void | itemChanged ()
virtual void | legendChanged ()
virtual QRectF | boundingRect () const
virtual void | getCanvasMarginHint (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasSize, double &left, double &top, double &right, double &bottom) const
| Calculate a hint for the canvas margin. More...
virtual void | updateScaleDiv (const QwtScaleDiv &, const QwtScaleDiv &)
| Update the item to changes of the axes scale division. More...
QRectF | scaleRect (const QwtScaleMap &, const QwtScaleMap &) const
| Calculate the bounding scale rectangle of 2 maps. More...
QRectF | paintRect (const QwtScaleMap &, const QwtScaleMap &) const
| Calculate the bounding paint rectangle of 2 maps. More...
virtual QList< QwtLegendData > | legendData () const
| Return all information, that is needed to represent the item on the legend. More...
virtual QwtGraphic | legendIcon (int index, const QSizeF &) const

## Protected Member Functions
virtual void | drawLegendData (QPainter *painter, const QwtPlotItem *, const QwtLegendData &, const QRectF &) const
virtual void | drawBackground (QPainter *, const QRectF &rect) const
Protected Member Functions inherited from QwtPlotItem
QwtGraphic | defaultIcon (const QBrush &, const QSizeF &) const
| Return a default icon from a brush. More...

## Detailed Description

A class which draws a legend inside the plot canvas.

QwtPlotLegendItem can be used to draw a inside the plot canvas. It can be used together with a QwtLegend or instead of it to have more space for the plot canvas.

In opposite to QwtLegend the legend item is not interactive. To identify mouse clicks on a legend item an event filter needs to be installed catching mouse events ob the plot canvas. The geometries of the legend items are available using legendGeometries().

The legend item is aligned to plot canvas according to its alignment() flags. It might have a background for the complete legend ( usually semi transparent ) or for each legend item.

Note
  An external QwtLegend with a transparent background on top the plot canvas might be another option with a similar effect.

## Member Enumeration Documentation

enum QwtPlotLegendItem::BackgroundMode

Background mode.

Depending on the mode the complete legend or each item might have an background.

The default setting is LegendBackground.

See Also
  setBackgroundMode(), setBackgroundBrush(), drawBackground()

Enumerator
LegendBackground | The legend has a background.
ItemBackground | Each item has a background.

## Member Function Documentation

Qt::Alignment QwtPlotLegendItem::alignment | ( |  | ) | const

Returns
  Alignment flags

See Also
  setAlignment()

QBrush QwtPlotLegendItem::backgroundBrush | ( |  | ) | const

Returns
  Brush is used to fill the background

See Also
  setBackgroundBrush(), backgroundMode(), drawBackground()

QwtPlotLegendItem::BackgroundMode QwtPlotLegendItem::backgroundMode | ( |  | ) | const

Returns
  backgroundMode

See Also
  setBackgroundMode(), backgroundBrush(), drawBackground()

int QwtPlotLegendItem::borderDistance | ( |  | ) | const

Returns
  Margin between the legend and the canvas border

See Also
  margin()

QPen QwtPlotLegendItem::borderPen | ( |  | ) | const

Returns
  Pen for drawing the border

See Also
  setBorderPen(), backgroundBrush()

double QwtPlotLegendItem::borderRadius | ( |  | ) | const

Returns
  Radius of the border

See Also
  setBorderRadius(), setBorderPen()

void QwtPlotLegendItem::draw | ( | QPainter * | painter,
|  | const QwtScaleMap & | xMap,
|  | const QwtScaleMap & | yMap,
|  | const QRectF & | canvasRect
| ) |  | const
| virtual

Draw the legend

Parameters

  painter | Painter
  xMap | x Scale Map
  yMap | y Scale Map
  canvasRect | Contents rectangle of the canvas in painter coordinates

Implements QwtPlotItem.

void QwtPlotLegendItem::drawBackground | ( | QPainter * | painter,
|  | const QRectF & | rect
| ) |  | const
| protectedvirtual

Draw a rounded rect

Parameters

  painter | Painter
  rect | Bounding rectangle

See Also
  setBorderRadius(), setBorderPen(), setBackgroundBrush(), setBackgroundMode()

void QwtPlotLegendItem::drawLegendData | ( | QPainter * | painter,
|  | const QwtPlotItem * | plotItem,
|  | const QwtLegendData & | data,
|  | const QRectF & | rect
| ) |  | const
| protectedvirtual

Draw an entry on the legend

Parameters

  painter | Qt Painter
  plotItem | Plot item, represented by the entry
  data | Attributes of the legend entry
  rect | Bounding rectangle for the entry

QFont QwtPlotLegendItem::font | ( |  | ) | const

Returns
  Font used for drawing the text label

See Also
  setFont()

QRect QwtPlotLegendItem::geometry | ( | const QRectF & | canvasRect | ) | const
| virtual

Calculate the geometry of the legend on the canvas

Parameters

  canvasRect | Geometry of the canvas

Returns
  Geometry of the legend

int QwtPlotLegendItem::heightForWidth | ( | const QwtLegendData & | data,
|  | int | width
| ) |  | const
| virtual

Returns
  The preferred height, for a width.

Parameters

  data | Attributes of the legend entry
  width | Width

int QwtPlotLegendItem::itemMargin | ( |  | ) | const

Returns
  Margin around each item

See Also
  setItemMargin(), itemSpacing(), margin(), spacing()

int QwtPlotLegendItem::itemSpacing | ( |  | ) | const

Returns
  Spacing inside of each item

See Also
  setItemSpacing(), itemMargin(), margin(), spacing()

QList< QRect > QwtPlotLegendItem::legendGeometries | ( | const QwtPlotItem * | plotItem | ) | const

Returns
  Geometries of the items of a plot item

Note
  Usually a plot item has only one entry on the legend

int QwtPlotLegendItem::margin | ( |  | ) | const

Returns
  Margin around the legend items

See Also
  setMargin(), spacing(), itemMargin(), itemSpacing()

uint QwtPlotLegendItem::maxColumns | ( |  | ) | const

Returns
  Maximum number of columns

See Also
  maxColumns(), QwtDynGridLayout::maxColumns()

QSize QwtPlotLegendItem::minimumSize | ( | const QwtLegendData & | data | ) | const
| virtual

Minimum size hint needed to display an entry

Parameters

  data | Attributes of the legend entry

Returns
  Minimum size

QList< const QwtPlotItem * > QwtPlotLegendItem::plotItems | ( |  | ) | const

Returns
  All plot items with an entry on the legend

Note
  A plot item might have more than one entry on the legend

int QwtPlotLegendItem::rtti | ( |  | ) | const
| virtual

Returns
  QwtPlotItem::Rtti_PlotLegend

Reimplemented from QwtPlotItem.

void QwtPlotLegendItem::setAlignment | ( | Qt::Alignment | alignment | ) |

Set the alignmnet.

Alignment means the position of the legend relative to the geometry of the plot canvas.

Parameters

  alignment | Alignment flags

See Also
  alignment(), setMaxColumns()

Note
  To align a legend with many items horizontally the number of columns need to be limited

void QwtPlotLegendItem::setBackgroundBrush | ( | const QBrush & | brush | ) |

Set the background brush.

The brush is used to fill the background

Parameters

  brush | Brush

See Also
  backgroundBrush(), setBackgroundMode(), drawBackground()

void QwtPlotLegendItem::setBackgroundMode | ( | BackgroundMode | mode | ) |

Set the background mode.

Depending on the mode the complete legend or each item might have an background.

The default setting is LegendBackground.

See Also
  backgroundMode(), setBackgroundBrush(), drawBackground()

void QwtPlotLegendItem::setBorderDistance | ( | int | distance | ) |

Set the margin between the legend and the canvas border.

The default setting for the margin is 10 pixels.

Parameters

  distance | Margin in pixels

See Also
  setMargin()

void QwtPlotLegendItem::setBorderPen | ( | const QPen & | pen | ) |

Set the pen for drawing the border

Parameters

  pen | Border pen

See Also
  borderPen(), setBackgroundBrush()

void QwtPlotLegendItem::setBorderRadius | ( | double | radius | ) |

Set the radius for the border

Parameters

  radius | A value <= 0 defines a rectangular border

See Also
  borderRadius(), setBorderPen()

void QwtPlotLegendItem::setFont | ( | const QFont & | font | ) |

Change the font used for drawing the text label

Parameters

  font | Legend font

See Also
  font()

void QwtPlotLegendItem::setItemMargin | ( | int | margin | ) |

Set the margin around each item

Parameters

  margin | Margin

See Also
  itemMargin(), setItemSpacing(), setMargin(), setSpacing()

void QwtPlotLegendItem::setItemSpacing | ( | int | spacing | ) |

Set the spacing inside of each item

Parameters

  spacing | Spacing

See Also
  itemSpacing(), setItemMargin(), setMargin(), setSpacing()

void QwtPlotLegendItem::setMargin | ( | int | margin | ) |

Set the margin around legend items.

The default setting for the margin is 0.

Parameters

  margin | Margin in pixels

See Also
  margin(), setSpacing(), setItemMargin(), setItemSpacing

void QwtPlotLegendItem::setMaxColumns | ( | uint | maxColumns | ) |

Limit the number of columns.

When aligning the legend horizontally ( Qt::AlignLeft, Qt::AlignRight ) the number of columns needs to be limited to avoid, that the width of the legend grows with an increasing number of entries.

Parameters

  maxColumns | Maximum number of columns. 0 means unlimited.

See Also
  maxColumns(), QwtDynGridLayout::setMaxColumns()

void QwtPlotLegendItem::setSpacing | ( | int | spacing | ) |

Set the spacing between the legend items.

Parameters

  spacing | Spacing in pixels

See Also
  spacing(), setMargin()

void QwtPlotLegendItem::setTextPen | ( | const QPen & | pen | ) |

Set the pen for drawing text labels.

Parameters

  pen | Text pen

See Also
  textPen(), setFont()

int QwtPlotLegendItem::spacing | ( |  | ) | const

Returns
  Spacing between the legend items

See Also
  setSpacing(), margin(), itemSpacing(), itemMargin()

QPen QwtPlotLegendItem::textPen | ( |  | ) | const

Returns
  Pen for drawing text labels

See Also
  setTextPen(), font()

void QwtPlotLegendItem::updateLegend | ( | const QwtPlotItem * | plotItem,
|  | const QList< QwtLegendData > & | data
| ) |  |
| virtual

Update the legend items according to modifications of a plot item

Parameters

  plotItem | Plot item
  data | Attributes of the legend entries

Reimplemented from QwtPlotItem.