Qwt User's Guide: QwtPlotItem Class Reference

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QwtPlotItem Class Reference

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

#include <qwt_plot_item.h>

Public Types
enum	RttiValues { Rtti_PlotItem = 0, Rtti_PlotGrid, Rtti_PlotScale, Rtti_PlotMarker, Rtti_PlotCurve, Rtti_PlotHistogram, Rtti_PlotSpectrogram, Rtti_PlotSVG, Rtti_PlotUserItem = 1000 }
enum	ItemAttribute { Legend = 1, AutoScale = 2 }
enum	RenderHint { RenderAntialiased = 1 }
Public Member Functions
	QwtPlotItem (const QwtText &title=QwtText())
virtual	~QwtPlotItem ()
void	attach (QwtPlot *plot)
void	detach ()
QwtPlot *	plot () const
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	setRenderHint (RenderHint, bool on=true)
bool	testRenderHint (RenderHint) const
double	z () const
void	setZ (double z)
void	show ()
void	hide ()
virtual void	setVisible (bool)
bool	isVisible () const
void	setAxis (int xAxis, int yAxis)
void	setXAxis (int axis)
int	xAxis () const
void	setYAxis (int axis)
int	yAxis () const
virtual void	itemChanged ()
virtual void	draw (QPainter *painter, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRect &canvasRect) const =0
virtual QwtDoubleRect	boundingRect () const
virtual void	updateLegend (QwtLegend *) const
virtual void	updateScaleDiv (const QwtScaleDiv &, const QwtScaleDiv &)
virtual QWidget *	legendItem () const
QwtDoubleRect	scaleRect (const QwtScaleMap &, const QwtScaleMap &) const
QRect	paintRect (const QwtScaleMap &, const QwtScaleMap &) const
QRect	transform (const QwtScaleMap &, const QwtScaleMap &, const QwtDoubleRect &) const
QwtDoubleRect	invTransform (const QwtScaleMap &, const QwtScaleMap &, const QRect &) const

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 legnd.

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

enum QwtPlotItem::ItemAttribute

Plot Item Attributes

Legend
The item is represented on the legend.
AutoScale
The boundingRect() of the item is included in the autoscaling calculation.

See also:: setItemAttribute(), testItemAttribute()

enum QwtPlotItem::RenderHint

Render hints.

enum QwtPlotItem::RttiValues

Runtime type information.

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

Constructor & Destructor Documentation

QwtPlotItem::QwtPlotItem ( const QwtText & title = QwtText() ) [explicit]

Constructor

Parameters:

title

Title of the item

QwtPlotItem::~QwtPlotItem ( ) [virtual]

Destroy the QwtPlotItem.

Member Function Documentation

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:: QwtPlotItem::detach()

QwtDoubleRect QwtPlotItem::boundingRect ( ) const [virtual]

Returns:: An invalid bounding rect: QwtDoubleRect(1.0, 1.0, -2.0, -2.0)

Reimplemented in QwtPlotCurve, QwtPlotMarker, QwtPlotSpectrogram, and QwtPlotSvgItem.

void QwtPlotItem::detach ( ) [inline]

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

detach() is equivalent to calling attach( NULL )

See also:: attach( QwtPlot* plot )

virtual void QwtPlotItem::draw	(	QPainter *	painter,
		const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QRect &	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 QwtPlotCurve, QwtPlotGrid, QwtPlotMarker, QwtPlotRasterItem, QwtPlotScaleItem, QwtPlotSpectrogram, and QwtPlotSvgItem.

void QwtPlotItem::hide ( )

Hide the item.

QwtDoubleRect QwtPlotItem::invTransform	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QRect &	rect
	)			const

Transform a rectangle from paint to scale coordinates

Parameters:

	xMap	X map
	yMap	Y map
	rect	Rectangle in paint coordinates

Returns:: Rectangle in scale coordinates

See also:: transform()

bool QwtPlotItem::isVisible ( ) const

Returns:: true if visible

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

void QwtPlotItem::itemChanged ( ) [virtual]

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

See also:: updateLegend()

QWidget * QwtPlotItem::legendItem ( ) const [virtual]

Allocate the widget that represents the item on the legend.

The default implementation is made for QwtPlotCurve and returns a QwtLegendItem(), but an item could be represented by any type of widget, by overloading legendItem() and updateLegend().

Returns:: QwtLegendItem()

See also:: updateLegend() QwtLegend()

Implements QwtLegendItemManager.

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

Calculate the bounding paint rect of 2 maps.

Parameters:

	xMap	X map
	yMap	X map

Returns:: Bounding rect of the scale maps

QwtPlot * QwtPlotItem::plot ( ) const

Return attached plot.

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 QwtPlotCurve, QwtPlotGrid, QwtPlotMarker, QwtPlotScaleItem, QwtPlotSpectrogram, and QwtPlotSvgItem.

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

Calculate the bounding scale rect of 2 maps.

Parameters:

	xMap	X map
	yMap	X map

Returns:: Bounding rect of the scale maps

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

Set X and Y axis

The item will painted according to the coordinates its Axes.

Parameters:

	xAxis	X Axis
	yAxis	Y Axis

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

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

Toggle an item attribute

Parameters:

	attribute	Attribute type
	on	true/false

See also:: testItemAttribute(), ItemAttribute

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

Toggle an render hint

Parameters:

	hint	Render hint
	on	true/false

See also:: testRenderHint(), RenderHint

void QwtPlotItem::setTitle ( const QwtText & title )

Set a new title

Parameters:

title

Title

See also:: title()

void QwtPlotItem::setTitle ( const QString & title )

Set a new title

Parameters:

title

Title

See also:: title()

void QwtPlotItem::setVisible ( bool on ) [virtual]

Show/Hide the item

Parameters:

Show if true, otherwise hide

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

void QwtPlotItem::setXAxis ( int axis )

Set the X axis

The item will painted according to the coordinates its Axes.

Parameters:

axis

X Axis

See also:: setAxis(), setYAxis(), xAxis()

void QwtPlotItem::setYAxis ( int axis )

Set the Y axis

The item will painted according to the coordinates its Axes.

Parameters:

axis

Y Axis

See also:: setAxis(), setXAxis(), yAxis()

void QwtPlotItem::setZ ( double z )

Set the z value.

Plot items are painted in increasing z-order.

Parameters:

Z-value

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

void QwtPlotItem::show ( )

Show the item.

bool QwtPlotItem::testItemAttribute ( ItemAttribute attribute ) const

Test an item attribute

Parameters:

attribute

Attribute type

Returns:: true/false

See also:: setItemAttribute(), ItemAttribute

bool QwtPlotItem::testRenderHint ( RenderHint hint ) const

Test a render hint

Parameters:

hint

Render hint

Returns:: true/false

See also:: setRenderHint(), RenderHint

const QwtText & QwtPlotItem::title ( ) const

Returns:: Title of the item

See also:: setTitle()

QRect QwtPlotItem::transform	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QwtDoubleRect &	rect
	)			const

Transform a rectangle

Parameters:

	xMap	X map
	yMap	Y map
	rect	Rectangle in scale coordinates

Returns:: Rectangle in paint coordinates

See also:: invTransform()

void QwtPlotItem::updateLegend ( QwtLegend * legend ) const [virtual]

Update the widget that represents the item on the legend.

updateLegend() is called from itemChanged() to adopt the widget representing the item on the legend to its new configuration.

The default implementation is made for QwtPlotCurve and updates a QwtLegendItem(), but an item could be represented by any type of widget, by overloading legendItem() and updateLegend().

Parameters:

legend

Legend

See also:: legendItem(), itemChanged(), QwtLegend()

Implements QwtLegendItemManager.

Reimplemented in QwtPlotCurve.

void QwtPlotItem::updateScaleDiv	(	const QwtScaleDiv &	,
		const QwtScaleDiv &
	)			`[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()

Parameters: