QWT API (English) 7.3.0
Qt Widget Library for Technical Applications - English API Documentation
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Classes | Public Types | Public Member Functions | Protected Member Functions | List of all members
QwtPlotItem Class Referenceabstract

Base class for items on the plot canvas. More...

#include <qwt_plot_item.h>

Inheritance diagram for QwtPlotItem:
QwtPlotArrowMarker QwtPlotGraphicItem QwtPlotGrid QwtPlotLegendItem QwtPlotMarker QwtPlotRasterItem QwtPlotScaleItem QwtPlotSeriesItem QwtPlotShapeItem QwtPlotTextLabel QwtPlotZoneItem

Classes

class  PrivateData
 

Public Types

enum  RttiValues {
  Rtti_PlotItem = 0 , Rtti_PlotGrid , Rtti_PlotScale , Rtti_PlotLegend ,
  Rtti_PlotMarker , Rtti_PlotCurve , Rtti_PlotSpectroCurve , Rtti_PlotIntervalCurve ,
  Rtti_PlotHistogram , Rtti_PlotSpectrogram , Rtti_PlotGraphic , Rtti_PlotTradingCurve ,
  Rtti_PlotBarChart , Rtti_PlotMultiBarChart , Rtti_PlotShape , Rtti_PlotTextLabel ,
  Rtti_PlotZone , Rtti_PlotVectorField , Rtti_PlotArrowMarker , Rtti_PlotBoxChart ,
  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...
 

Public Member Functions

 QwtPlotItem ()
 Default constructor.
 
 QwtPlotItem (const QString &title)
 Constructor with title as QString.
 
 QwtPlotItem (const QwtText &title)
 Constructor with title as QwtText.
 
virtual ~QwtPlotItem ()
 Destructor.
 
virtual void attach (QwtPlot *plot)
 Attach the item to a plot.
 
void detach ()
 Detach the item from the plot.
 
QwtPlotplot () const
 Get the plot the item is attached to.
 
void setTitle (const QString &title)
 Set the title using a QString.
 
void setTitle (const QwtText &title)
 Set the title using a QwtText.
 
const QwtTexttitle () const
 Get the title.
 
virtual int rtti () const
 Runtime type information.
 
void setItemAttribute (ItemAttribute, bool on=true)
 Set an item attribute.
 
bool testItemAttribute (ItemAttribute) const
 Test an item attribute.
 
void setItemInterest (ItemInterest, bool on=true)
 Set an item interest.
 
bool testItemInterest (ItemInterest) const
 Test an item interest.
 
void setRenderHint (RenderHint, bool on=true)
 Set a render hint.
 
bool testRenderHint (RenderHint) const
 Test a render hint.
 
void setRenderThreadCount (uint numThreads)
 Set the number of render threads.
 
uint renderThreadCount () const
 Get the number of render threads.
 
void setLegendIconSize (const QSize &)
 Set the legend icon size.
 
QSize legendIconSize () const
 Get the legend icon size.
 
double z () const
 Get the z-value.
 
void setZ (double z)
 Set the z-value.
 
void show ()
 Show the item.
 
void hide ()
 Hide the item.
 
virtual void setVisible (bool)
 Set the visibility.
 
bool isVisible () const
 Check if the item is visible.
 
void setAxes (QwtAxisId xAxis, QwtAxisId yAxis)
 Set both axes.
 
void setXAxis (QwtAxisId)
 Set the x-axis.
 
QwtAxisId xAxis () const
 Get the x-axis.
 
void setYAxis (QwtAxisId)
 Set the y-axis.
 
QwtAxisId yAxis () const
 Get the y-axis.
 
virtual void itemChanged ()
 Notify the plot that the item has changed.
 
virtual void legendChanged ()
 Notify the item that the legend has changed.
 
virtual void draw (QPainter *painter, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect) const =0
 Draw the item.
 
virtual QRectF boundingRect () const
 Get the bounding rectangle.
 
virtual void getCanvasMarginHint (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, double &left, double &top, double &right, double &bottom) const
 Get margin hints for the canvas.
 
virtual void updateScaleDiv (const QwtScaleDiv &, const QwtScaleDiv &)
 Update the item with new scale divisions.
 
virtual void updateLegend (const QwtPlotItem *, const QList< QwtLegendData > &)
 Update the item with changes of the legend.
 
QRectF scaleRect (const QwtScaleMap &, const QwtScaleMap &) const
 Calculate the scale rectangle.
 
QRectF paintRect (const QwtScaleMap &, const QwtScaleMap &) const
 Calculate the paint rectangle.
 
virtual QList< QwtLegendDatalegendData () const
 Return legend data.
 
virtual QwtGraphic legendIcon (int index, const QSizeF &) const
 Return a legend icon.
 

Protected Member Functions

QwtGraphic defaultIcon (const QBrush &, const QSizeF &) const
 Create a default icon.
 

Detailed Description

Base class for items on the plot canvas.

A plot item is "something", that can be painted on the plot canvas, or only affects the scales of the plot widget. They can be categorized as:

Depending on the QwtPlotItem::ItemAttribute flags, an item is included into autoscaling or has an entry on the legend.

Before misusing the existing item classes it might be better to implement a new type of plot item ( don't implement a watermark as spectrogram ). Deriving a new type of QwtPlotItem primarily means to implement the YourPlotItem::draw() method.

See also
The cpuplot example shows the implementation of additional plot items.

Member Enumeration Documentation

◆ ItemAttribute

Plot Item Attributes.

Various aspects of a plot widget depend on the attributes of the attached plot items. If and how a single plot item participates in these updates depends on its attributes.

See also
setItemAttribute(), testItemAttribute(), ItemInterest
Enumerator
Legend 

The item is represented on the legend.

AutoScale 

The boundingRect() of the item is included in the autoscaling calculation as long as its width or height is >= 0.0.

Margins 

The item needs extra space to display something outside its bounding rectangle.

See also
getCanvasMarginHint()

◆ ItemInterest

Plot Item Interests.

Plot items might depend on the situation of the corresponding plot widget. By enabling an interest the plot item will be notified, when the corresponding attribute of the plot widgets has changed.

See also
setItemAttribute(), testItemAttribute(), ItemInterest
Enumerator
ScaleInterest 

The item is interested in updates of the scales

See also
updateScaleDiv()
LegendInterest 

The item is interested in updates of the legend ( of other items ) This flag is intended for items, that want to implement a legend for displaying entries of other plot item.

Note
If the plot item wants to be represented on a legend enable QwtPlotItem::Legend instead.
See also
updateLegend()

◆ RenderHint

Render hints.

Enumerator
RenderAntialiased 

Enable antialiasing.

◆ RttiValues

Runtime type information.

RttiValues is used to cast plot items, without having to enable runtime type information of the compiler.

Enumerator
Rtti_PlotItem 

Unspecific value, that can be used, when it doesn't matter.

Rtti_PlotGrid 

For QwtPlotGrid.

Rtti_PlotScale 

For QwtPlotScaleItem.

Rtti_PlotLegend 

For QwtPlotLegendItem.

Rtti_PlotMarker 

For QwtPlotMarker.

Rtti_PlotCurve 

For QwtPlotCurve.

Rtti_PlotSpectroCurve 

For QwtPlotSpectroCurve.

Rtti_PlotIntervalCurve 

For QwtPlotIntervalCurve.

Rtti_PlotHistogram 

For QwtPlotHistogram.

Rtti_PlotSpectrogram 

For QwtPlotSpectrogram.

Rtti_PlotGraphic 

For QwtPlotGraphicItem, QwtPlotSvgItem.

Rtti_PlotTradingCurve 

For QwtPlotTradingCurve.

Rtti_PlotBarChart 

For QwtPlotBarChart.

Rtti_PlotMultiBarChart 

For QwtPlotMultiBarChart.

Rtti_PlotShape 

For QwtPlotShapeItem.

Rtti_PlotTextLabel 

For QwtPlotTextLabel.

Rtti_PlotZone 

For QwtPlotZoneItem.

Rtti_PlotVectorField 

For QwtPlotVectorField.

Rtti_PlotArrowMarker 

For QwtPlotArrowMarker.

Rtti_PlotBoxChart 

Boxplot chart item.

Rtti_PlotUserItem 

Values >= Rtti_PlotUserItem are reserved for plot items not implemented in the Qwt library.

Constructor & Destructor Documentation

◆ QwtPlotItem()

QwtPlotItem::QwtPlotItem ( )
explicit

Default constructor.

Constructs a QwtPlotItem with default settings.

Constructor with title as QString

Parameters
[in]titleTitle of the item

Constructs a QwtPlotItem with the given title.

Constructor with title as QwtText

Parameters
[in]titleTitle of the item

Constructs a QwtPlotItem with the given title.

Destructor

Destroys the QwtPlotItem and detaches it from any plot.

Member Function Documentation

◆ attach()

void QwtPlotItem::attach ( QwtPlot plot)
virtual

Attach the item to a plot.

Parameters
[in]plotPlot widget to attach to

This method will attach a QwtPlotItem to the QwtPlot argument. It will first detach the QwtPlotItem from any plot from a previous call to attach (if necessary). If a nullptr argument is passed, it will detach from any QwtPlot it was attached to.

See also
detach()

Reimplemented in QwtPlotBarChart, QwtPlotBoxChart, QwtPlotCurve, QwtPlotHistogram, QwtPlotIntervalCurve, and QwtPlotMultiBarChart.

◆ boundingRect()

QRectF QwtPlotItem::boundingRect ( ) const
virtual

Get the bounding rectangle.

Returns
An invalid bounding rect: QRectF(1.0, 1.0, -2.0, -2.0)
Note
A width or height < 0.0 is ignored by the autoscaler.

Reimplemented in QwtPlotArrowMarker, QwtPlotBarChart, QwtPlotBoxChart, QwtPlotGraphicItem, QwtPlotHistogram, QwtPlotIntervalCurve, QwtPlotMarker, QwtPlotMultiBarChart, QwtPlotRasterItem, QwtPlotSeriesItem, QwtPlotShapeItem, QwtPlotTradingCurve, QwtPlotVectorField, and QwtPlotZoneItem.

◆ defaultIcon()

QwtGraphic QwtPlotItem::defaultIcon ( const QBrush &  brush,
const QSizeF &  size 
) const
protected

Create a default icon.

Return a default icon from a brush.

◆ detach()

void QwtPlotItem::detach ( )

Detach the item from the plot.

This method detaches a QwtPlotItem from any QwtPlot it has been associated with. detach() is equivalent to calling attach( nullptr ).

See also
attach()

◆ draw()

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

Draw the item.

Parameters
painterPainter
xMapMaps x-values into pixel coordinates.
yMapMaps y-values into pixel coordinates.
canvasRectContents rect of the canvas in painter coordinates

Implemented in QwtPlotTextLabel, QwtPlotZoneItem, QwtPlotMarker, QwtPlotGraphicItem, QwtPlotGrid, QwtPlotLegendItem, QwtPlotRasterItem, QwtPlotScaleItem, QwtPlotSeriesItem, QwtPlotShapeItem, QwtPlotSpectrogram, and QwtPlotArrowMarker.

◆ getCanvasMarginHint()

void QwtPlotItem::getCanvasMarginHint ( const QwtScaleMap xMap,
const QwtScaleMap yMap,
const QRectF &  canvasRect,
double &  left,
double &  top,
double &  right,
double &  bottom 
) const
virtual

Get margin hints for the canvas.

Calculate a hint for the canvas margin.

Parameters
[in]xMapMaps x-values into pixel coordinates
[in]yMapMaps y-values into pixel coordinates
[in]canvasRectContents rectangle of the canvas in painter coordinates
[out]leftReturns the left margin
[out]topReturns the top margin
[out]rightReturns the right margin
[out]bottomReturns the bottom margin

When the QwtPlotItem::Margins flag is enabled the plot item indicates, that it needs some margins at the borders of the canvas. This is e.g. used by bar charts to reserve space for displaying the bars. The margins are in target device coordinates (pixels on screen). The default implementation returns 0 for all margins.

See also
QwtPlot::getCanvasMarginsHint(), QwtPlot::updateCanvasMargins()

Reimplemented in QwtPlotAbstractBarChart.

◆ hide()

void QwtPlotItem::hide ( )

Hide the item.

Equivalent to calling setVisible( false ).

See also
show(), setVisible(), isVisible()

◆ isVisible()

bool QwtPlotItem::isVisible ( ) const

Check if the item is visible.

Returns
true if visible, false otherwise
See also
setVisible(), show(), hide()

◆ itemChanged()

void QwtPlotItem::itemChanged ( )
virtual

Notify the plot that the item has changed.

Update the legend and call QwtPlot::autoRefresh() for the parent plot.

See also
QwtPlot::legendChanged(), QwtPlot::autoRefresh()

◆ legendChanged()

void QwtPlotItem::legendChanged ( )
virtual

Notify the item that the legend has changed.

Notify that the legend has changed.

Update the legend of the parent plot.

See also
QwtPlot::updateLegend(), itemChanged()

◆ legendData()

QList< QwtLegendData > QwtPlotItem::legendData ( ) const
virtual

Return legend data.

Return all information needed to represent the item on the legend.

Returns
Data that is needed to represent the item on the legend

Most items are represented by one entry on the legend showing an icon and a text, but e.g. QwtPlotMultiBarChart displays one entry for each bar. QwtLegendData is basically a list of QVariants that makes it possible to overload and reimplement legendData() to return almost any type of information, that is understood by the receiver that acts as the legend. The default implementation returns one entry with the title() of the item and the legendIcon().

See also
title(), legendIcon(), QwtLegend, QwtPlotLegendItem

Reimplemented in QwtPlotBarChart, and QwtPlotMultiBarChart.

◆ legendIcon()

QwtGraphic QwtPlotItem::legendIcon ( int  index,
const QSizeF &  size 
) const
virtual

Return a legend icon.

Get the icon representing the item on the legend.

Parameters
[in]indexIndex of the legend entry (usually there is only one)
[in]sizeIcon size
Returns
Icon representing the item on the legend

The default implementation returns an invalid icon.

See also
setLegendIconSize(), legendData()

Reimplemented in QwtPlotBarChart, QwtPlotBoxChart, QwtPlotCurve, QwtPlotHistogram, QwtPlotIntervalCurve, QwtPlotMarker, QwtPlotMultiBarChart, QwtPlotShapeItem, QwtPlotTradingCurve, QwtPlotVectorField, and QwtPlotArrowMarker.

◆ legendIconSize()

QSize QwtPlotItem::legendIconSize ( ) const

Get the legend icon size.

Returns
Legend icon size
See also
setLegendIconSize(), legendIcon()

◆ paintRect()

QRectF QwtPlotItem::paintRect ( const QwtScaleMap xMap,
const QwtScaleMap yMap 
) const

Calculate the paint rectangle.

Calculate the bounding paint rectangle of 2 maps.

Parameters
[in]xMapMaps x-values into pixel coordinates
[in]yMapMaps y-values into pixel coordinates
Returns
Bounding paint rectangle of the scale maps, not normalized

◆ plot()

QwtPlot * QwtPlotItem::plot ( ) const

Get the plot the item is attached to.

Returns
Attached plot, or nullptr if not attached

◆ renderThreadCount()

uint QwtPlotItem::renderThreadCount ( ) const

Get the number of render threads.

Returns
Number of threads to be used for rendering. If renderThreadCount() is set to 0, the system specific ideal thread count is used.

◆ rtti()

int QwtPlotItem::rtti ( ) const
virtual

Runtime type information.

Get runtime type information.

Returns
rtti value for the specific class

Return rtti for the specific class represented. QwtPlotItem is simply a virtual interface class, and base classes will implement this method with specific rtti values so a user can differentiate them. The rtti value is useful for environments, where the runtime type information is disabled and it is not possible to do a dynamic_cast<...>.

See also
RttiValues

Reimplemented in QwtPlotArrowMarker, QwtPlotBarChart, QwtPlotBoxChart, QwtPlotCurve, QwtPlotGraphicItem, QwtPlotGrid, QwtPlotHistogram, QwtPlotIntervalCurve, QwtPlotLegendItem, QwtPlotMarker, QwtPlotMultiBarChart, QwtPlotScaleItem, QwtPlotShapeItem, QwtPlotSpectroCurve, QwtPlotSpectrogram, QwtPlotTextLabel, QwtPlotTradingCurve, QwtPlotVectorField, and QwtPlotZoneItem.

◆ scaleRect()

QRectF QwtPlotItem::scaleRect ( const QwtScaleMap xMap,
const QwtScaleMap yMap 
) const

Calculate the scale rectangle.

Calculate the bounding scale rectangle of 2 maps.

Parameters
[in]xMapMaps x-values into pixel coordinates
[in]yMapMaps y-values into pixel coordinates
Returns
Bounding scale rect of the scale maps, not normalized

◆ setAxes()

void QwtPlotItem::setAxes ( QwtAxisId  xAxisId,
QwtAxisId  yAxisId 
)

Set both axes.

Set X and Y axes.

Parameters
[in]xAxisIdX Axis identifier
[in]yAxisIdY Axis identifier

The item will be painted according to the coordinates of its axes.

See also
setXAxis(), setYAxis(), xAxis(), yAxis()

◆ setItemAttribute()

void QwtPlotItem::setItemAttribute ( ItemAttribute  attribute,
bool  on = true 
)

Set an item attribute.

Parameters
[in]attributeAttribute type to set
[in]ontrue to enable, false to disable

Toggle an item attribute.

See also
testItemAttribute(), ItemInterest

◆ setItemInterest()

void QwtPlotItem::setItemInterest ( ItemInterest  interest,
bool  on = true 
)

Set an item interest.

Parameters
[in]interestInterest type to set
[in]ontrue to enable, false to disable

Toggle an item interest.

See also
testItemInterest(), ItemAttribute

◆ setLegendIconSize()

void QwtPlotItem::setLegendIconSize ( const QSize &  size)

Set the legend icon size.

Set the size of the legend icon.

Parameters
[in]sizeIcon size

The default setting is 8x8 pixels.

See also
legendIconSize(), legendIcon()

◆ setRenderHint()

void QwtPlotItem::setRenderHint ( RenderHint  hint,
bool  on = true 
)

Set a render hint.

Parameters
[in]hintRender hint to set
[in]ontrue to enable, false to disable

Toggle a render hint.

See also
testRenderHint(), RenderHint

◆ setRenderThreadCount()

void QwtPlotItem::setRenderThreadCount ( uint  numThreads)

Set the number of render threads.

Parameters
[in]numThreadsNumber of threads to be used for rendering. If numThreads is set to 0, the system specific ideal thread count is used.

On multi core systems rendering of certain plot item (e.g. QwtPlotRasterItem) can be done in parallel in several threads. The default setting is set to 1.

◆ setTitle() [1/2]

void QwtPlotItem::setTitle ( const QString &  title)

Set the title using a QString.

Parameters
[in]titleTitle text
See also
title()

◆ setTitle() [2/2]

void QwtPlotItem::setTitle ( const QwtText title)

Set the title using a QwtText.

Parameters
[in]titleTitle text
See also
title()

◆ setVisible()

void QwtPlotItem::setVisible ( bool  on)
virtual

Set the visibility.

Set the visibility of the item.

Parameters
[in]onShow if true, otherwise hide
See also
isVisible(), show(), hide()

◆ setXAxis()

void QwtPlotItem::setXAxis ( QwtAxisId  axisId)

Set the x-axis.

Set the X axis.

Parameters
[in]axisIdX Axis identifier

The item will be painted according to the coordinates of its axis.

See also
setAxes(), setYAxis(), xAxis()

◆ setYAxis()

void QwtPlotItem::setYAxis ( QwtAxisId  axisId)

Set the y-axis.

Set the Y axis.

Parameters
[in]axisIdY Axis identifier

The item will be painted according to the coordinates of its axis.

See also
setAxes(), setXAxis(), yAxis()

◆ setZ()

void QwtPlotItem::setZ ( double  z)

Set the z-value.

Parameters
[in]zZ-value for the item

Plot items are painted in increasing z-order.

See also
z(), QwtPlotDict::itemList()

◆ show()

void QwtPlotItem::show ( )

Show the item.

Equivalent to calling setVisible( true ).

See also
hide(), setVisible(), isVisible()

◆ testItemAttribute()

bool QwtPlotItem::testItemAttribute ( ItemAttribute  attribute) const

Test an item attribute.

Parameters
[in]attributeAttribute type to test
Returns
true if the attribute is enabled, false otherwise
See also
setItemAttribute(), ItemInterest

◆ testItemInterest()

bool QwtPlotItem::testItemInterest ( ItemInterest  interest) const

Test an item interest.

Parameters
[in]interestInterest type to test
Returns
true if the interest is enabled, false otherwise
See also
setItemInterest(), ItemAttribute

◆ testRenderHint()

bool QwtPlotItem::testRenderHint ( RenderHint  hint) const

Test a render hint.

Parameters
[in]hintRender hint to test
Returns
true if the render hint is enabled, false otherwise
See also
setRenderHint(), RenderHint

◆ title()

const QwtText & QwtPlotItem::title ( ) const

Get the title.

Get the title of the item.

Returns
Title of the item
See also
setTitle()

◆ updateLegend()

void QwtPlotItem::updateLegend ( const QwtPlotItem item,
const QList< QwtLegendData > &  data 
)
virtual

Update the item with changes of the legend.

Update the item to changes of the legend info.

Parameters
[in]itemPlot item to be displayed on a legend
[in]dataAttributes how to display item on the legend

Plot items that want to display a legend (not those, that want to be displayed on a legend!) will have to implement updateLegend(). updateLegend() is only called when the LegendInterest interest is enabled. The default implementation does nothing.

Note
Plot items, that want to be displayed on a legend need to enable the QwtPlotItem::Legend flag and to implement legendData() and legendIcon().
See also
QwtPlotLegendItem

Reimplemented in QwtPlotLegendItem.

◆ updateScaleDiv()

void QwtPlotItem::updateScaleDiv ( const QwtScaleDiv xScaleDiv,
const QwtScaleDiv yScaleDiv 
)
virtual

Update the item with new scale divisions.

Update the item to changes of the axes scale division.

Parameters
[in]xScaleDivScale division of the x-axis
[in]yScaleDivScale division of the y-axis

Update the item, when the axes of plot have changed. The default implementation does nothing, but items that depend on the scale division (like QwtPlotGrid()) have to reimplement updateScaleDiv(). updateScaleDiv() is only called when the ScaleInterest interest is enabled. The default implementation does nothing.

See also
QwtPlot::updateAxes(), ScaleInterest

Reimplemented in QwtPlotScaleItem, QwtPlotSeriesItem, and QwtPlotGrid.

◆ xAxis()

QwtAxisId QwtPlotItem::xAxis ( ) const

Get the x-axis.

Get the X axis.

Returns
X Axis identifier

◆ yAxis()

QwtAxisId QwtPlotItem::yAxis ( ) const

Get the y-axis.

Get the Y axis.

Returns
Y Axis identifier

◆ z()

double QwtPlotItem::z ( ) const

Get the z-value.

Returns
Z-value of the item

Plot items are painted in increasing z-order.

See also
setZ(), QwtPlotDict::itemList()

The documentation for this class was generated from the following files: