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

#include <qwt_plot_item.h>

Inheritance diagram for QwtPlotItem:

[legend]

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_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
	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

virtual int	rtti () 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 void	draw (QPainter *painter, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect) const =0
	Draw the item. More...

virtual QRectF	boundingRect () const

virtual void	getCanvasMarginHint (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, 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...

virtual void	updateLegend (const QwtPlotItem *, const QList< QwtLegendData > &)
	Update the item to changes of the legend info. 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
QwtGraphic	defaultIcon (const QBrush &, const QSizeF &) const
	Return a default icon from a brush. More...

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:

Representator
A "Representator" is an item that represents some sort of data on the plot canvas. The different representator classes are organized according to the characteristics of the data:
- QwtPlotMarker Represents a point or a horizontal/vertical coordinate
- QwtPlotCurve Represents a series of points
- QwtPlotSpectrogram ( QwtPlotRasterItem ) Represents raster data
- ...
Decorators
A "Decorator" is an item, that displays additional information, that is not related to any data:
- QwtPlotGrid
- QwtPlotScaleItem
- QwtPlotSvgItem
- ...

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

enum QwtPlotItem::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

enum QwtPlotItem::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

enum QwtPlotItem::RenderHint

Render hints.

Enumerator
RenderAntialiased	Enable antialiasing.

◆ RttiValues

enum QwtPlotItem::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_PlotSVG	For 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_PlotUserItem	Values >= Rtti_PlotUserItem are reserved for plot items not implemented in the Qwt library.

Constructor & Destructor Documentation

◆ QwtPlotItem()

QwtPlotItem::QwtPlotItem ( const QwtText & title = QwtText() )

explicit

Constructor

Parameters

title Title of the item

Member Function Documentation

◆ attach()

void QwtPlotItem::attach ( QwtPlot * plot )

Attach the item to a plot.

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 NULL argument is passed, it will detach from any QwtPlot it was attached to.

Parameters

plot	Plot widget

See also: detach()

◆ boundingRect()

QRectF QwtPlotItem::boundingRect ( ) const

virtual

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 QwtPlotZoneItem, QwtPlotTradingCurve, QwtPlotSvgItem, QwtPlotShapeItem, QwtPlotSeriesItem, QwtPlotRasterItem, QwtPlotMultiBarChart, QwtPlotMarker, QwtPlotIntervalCurve, QwtPlotHistogram, and QwtPlotBarChart.

◆ defaultIcon()

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

protected

Return a default icon from a brush.

The default icon is a filled rectangle used in several derived classes as legendIcon().

Parameters

brush	Fill brush
size	Icon size

Returns: A filled rectangle

◆ detach()

void QwtPlotItem::detach ( )

This method detaches a QwtPlotItem from any QwtPlot it has been associated with.

detach() is equivalent to calling attach( NULL )

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

painter	Painter
xMap	Maps x-values into pixel coordinates.
yMap	Maps y-values into pixel coordinates.
canvasRect	Contents rect of the canvas in painter coordinates

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

◆ getCanvasMarginHint()

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

virtual

Calculate a hint for the canvas 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 f.e. used by bar charts to reserve space for displaying the bars.

The margins are in target device coordinates ( pixels on screen )

Parameters

xMap	Maps x-values into pixel coordinates.
yMap	Maps y-values into pixel coordinates.
canvasRect	Contents rectangle of the canvas in painter coordinates
left	Returns the left margin
top	Returns the top margin
right	Returns the right margin
bottom	Returns the bottom margin

The default implementation returns 0 for all margins

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

Reimplemented in QwtPlotAbstractBarChart.

◆ isVisible()

bool QwtPlotItem::isVisible ( ) const

Returns: true if visible

See also: setVisible(), show(), hide()

◆ itemChanged()

void QwtPlotItem::itemChanged ( )

virtual

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

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

◆ legendChanged()

void QwtPlotItem::legendChanged ( )

virtual

Update the legend of the parent plot.

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

◆ legendData()

QList< QwtLegendData > QwtPlotItem::legendData ( ) const

virtual

Return all information, 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 f.e. 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().

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

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

Reimplemented in QwtPlotMultiBarChart, and QwtPlotBarChart.

◆ legendIcon()

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

virtual

Returns: Icon representing the item on the legend

The default implementation returns an invalid icon

Parameters

index	Index of the legend entry ( usually there is only one )
size	Icon size

See also: setLegendIconSize(), legendData()

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

◆ legendIconSize()

QSize QwtPlotItem::legendIconSize ( ) const

Returns: Legend icon size

See also: setLegendIconSize(), legendIcon()

◆ paintRect()

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

Calculate the bounding paint rectangle of 2 maps.

Parameters

xMap	Maps x-values into pixel coordinates.
yMap	Maps y-values into pixel coordinates.

Returns: Bounding paint rectangle of the scale maps, not normalized

◆ renderThreadCount()

uint QwtPlotItem::renderThreadCount ( ) const

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

◆ rtti()

int QwtPlotItem::rtti ( ) const

virtual

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<...>.

Returns: rtti value

See also: RttiValues

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

◆ scaleRect()

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

Calculate the bounding scale rectangle of 2 maps.

Parameters

xMap	Maps x-values into pixel coordinates.
yMap	Maps y-values into pixel coordinates.

Returns: Bounding scale rect of the scale maps, not normalized

◆ setAxes()

void QwtPlotItem::setAxes	(	int	xAxis,
		int	yAxis
	)

Set X and Y axis

The item will painted according to the coordinates of its Axes.

Parameters

xAxis	X Axis ( QwtPlot::xBottom or QwtPlot::xTop )
yAxis	Y Axis ( QwtPlot::yLeft or QwtPlot::yRight )

See also: setXAxis(), setYAxis(), xAxis(), yAxis(), QwtPlot::Axis

◆ setItemAttribute()

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

Toggle an item attribute

Parameters

attribute	Attribute type
on	true/false

See also: testItemAttribute(), ItemInterest

◆ setItemInterest()

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

Toggle an item interest

Parameters

interest	Interest type
on	true/false

See also: testItemInterest(), ItemAttribute

◆ setLegendIconSize()

void QwtPlotItem::setLegendIconSize ( const QSize & size )

Set the size of the legend icon

The default setting is 8x8 pixels

Parameters

size Size

See also: legendIconSize(), legendIcon()

◆ setRenderHint()

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

Toggle an render hint

Parameters

hint	Render hint
on	true/false

See also: testRenderHint(), RenderHint

◆ setRenderThreadCount()

void QwtPlotItem::setRenderThreadCount ( uint numThreads )

On multi core systems rendering of certain plot item ( f.e QwtPlotRasterItem ) can be done in parallel in several threads.

The default setting is set to 1.

Parameters

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

The default thread count is 1 ( = no additional threads )

◆ setTitle() [1/2]

void QwtPlotItem::setTitle ( const QString & title )

Set a new title

Parameters

title Title

See also: title()

◆ setTitle() [2/2]

void QwtPlotItem::setTitle ( const QwtText & title )

Set a new title

Parameters

title Title

See also: title()

◆ setVisible()

void QwtPlotItem::setVisible ( bool on )

virtual

Show/Hide the item

Parameters

on	Show if true, otherwise hide

See also: isVisible(), show(), hide()

◆ setXAxis()

void QwtPlotItem::setXAxis ( int axis )

Set the X axis

The item will painted according to the coordinates its Axes.

Parameters

axis	X Axis ( QwtPlot::xBottom or QwtPlot::xTop )

See also: setAxes(), setYAxis(), xAxis(), QwtPlot::Axis

◆ setYAxis()

void QwtPlotItem::setYAxis ( int axis )

Set the Y axis

The item will painted according to the coordinates its Axes.

Parameters

axis	Y Axis ( QwtPlot::yLeft or QwtPlot::yRight )

See also: setAxes(), setXAxis(), yAxis(), QwtPlot::Axis

◆ setZ()

void QwtPlotItem::setZ ( double z )

Set the z value.

Plot items are painted in increasing z-order.

Parameters

z Z-value

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

◆ testItemAttribute()

bool QwtPlotItem::testItemAttribute ( ItemAttribute attribute ) const

Test an item attribute

Parameters

attribute Attribute type

Returns: true/false

See also: setItemAttribute(), ItemInterest

◆ testItemInterest()

bool QwtPlotItem::testItemInterest ( ItemInterest interest ) const

Test an item interest

Parameters

interest Interest type

Returns: true/false

See also: setItemInterest(), ItemAttribute

◆ testRenderHint()

bool QwtPlotItem::testRenderHint ( RenderHint hint ) const

Test a render hint

Parameters

hint	Render hint

Returns: true/false

See also: setRenderHint(), RenderHint

◆ title()

const QwtText & QwtPlotItem::title ( ) const

Returns: Title of the item

See also: setTitle()

◆ updateLegend()

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

virtual

Update the item to changes of the legend info.

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.

Parameters

item	Plot item to be displayed on a legend
data	Attributes how to display item on the legend

See also: QwtPlotLegendItem

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

Reimplemented in QwtPlotLegendItem.

◆ updateScaleDiv()

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

virtual

Update the item to changes of the axes scale division.

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.

Parameters

xScaleDiv	Scale division of the x-axis
yScaleDiv	Scale division of the y-axis

See also: QwtPlot::updateAxes(), ScaleInterest

Reimplemented in QwtPlotGrid, QwtPlotSeriesItem, and QwtPlotScaleItem.

◆ z()

double QwtPlotItem::z ( ) const

Plot items are painted in increasing z-order.

Returns: setZ(), QwtPlotDict::itemList()

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

◆ ItemAttribute

◆ ItemInterest

◆ RenderHint

◆ RttiValues

Constructor & Destructor Documentation

◆ QwtPlotItem()

Member Function Documentation

◆ attach()

◆ boundingRect()

◆ defaultIcon()

◆ detach()

◆ draw()

◆ getCanvasMarginHint()

◆ isVisible()

◆ itemChanged()

◆ legendChanged()

◆ legendData()

◆ legendIcon()

◆ legendIconSize()

◆ paintRect()

◆ renderThreadCount()

◆ rtti()

◆ scaleRect()

◆ setAxes()

◆ setItemAttribute()

◆ setItemInterest()

◆ setLegendIconSize()

◆ setRenderHint()

◆ setRenderThreadCount()

◆ setTitle() [1/2]

◆ setTitle() [2/2]

◆ setVisible()

◆ setXAxis()

◆ setYAxis()

◆ setZ()

◆ testItemAttribute()

◆ testItemInterest()

◆ testRenderHint()

◆ title()

◆ updateLegend()

◆ updateScaleDiv()

◆ z()