Man page - qwtplotitem(3)

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Manual

QwtPlotItem

NAME

QwtPlotItem - Base class for items on the plot canvas.

SYNOPSIS

#include <qwt_plot_item.h>

Inherited by QwtPlotGrid , QwtPlotLegendItem , QwtPlotMarker , QwtPlotRasterItem , QwtPlotScaleItem , QwtPlotSeriesItem , QwtPlotShapeItem , QwtPlotSvgItem , QwtPlotTextLabel , and QwtPlotZoneItem .

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.
enum ItemAttribute { Legend = 0x01, AutoScale = 0x02, Margins = 0x04 }
Plot Item Attributes.
enum ItemInterest { ScaleInterest = 0x01, LegendInterest = 0x02 }
Plot Item Interests.
enum RenderHint { RenderAntialiased = 0x1 }
Render hints.
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.
void detach ()
This method detaches a QwtPlotItem from any QwtPlot it has been associated with.
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.
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.
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.
virtual void updateScaleDiv (const QwtScaleDiv &, const QwtScaleDiv &)
Update the item to changes of the axes scale division.
virtual void updateLegend (const QwtPlotItem *, const QList< QwtLegendData > &)
Update the item to changes of the legend info.
QRectF scaleRect (const QwtScaleMap &, const QwtScaleMap &) const
Calculate the bounding scale rectangle of 2 maps.
QRectF paintRect (const QwtScaleMap &, const QwtScaleMap &) const
Calculate the bounding paint rectangle of 2 maps.
virtual QList< QwtLegendData > legendData () const
Return all information, that is needed to represent the item on the legend.
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.

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

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()

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()

enum QwtPlotItem::RenderHint

Render hints.

Enumerator
RenderAntialiased

Enable antialiasing.

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

Constructor

Parameters:

title Title of the item

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:

detach()

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

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

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()

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

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

void QwtPlotItem::getCanvasMarginHint (const QwtScaleMap & xMap, constQwtScaleMap & 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 .

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:

QwtPlot::legendChanged(), QwtPlot::autoRefresh()

void QwtPlotItem::legendChanged () [virtual]

Update the legend of the parent plot.

See also:

QwtPlot::updateLegend() , itemChanged()

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 QwtPlotBarChart , and QwtPlotMultiBarChart .

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

QSize QwtPlotItem::legendIconSize () const

Returns:

Legend icon size

See also:

setLegendIconSize() , legendIcon()

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

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.

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

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

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

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

Toggle an item attribute

Parameters:

attribute Attribute type
on true/false

See also:

testItemAttribute() , ItemInterest

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

Toggle an item interest

Parameters:

interest Interest type
on true/false

See also:

testItemInterest() , ItemAttribute

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()

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::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 )

void QwtPlotItem::setTitle (const QString & title)

Set a new title

Parameters:

title Title

See also:

title()

void QwtPlotItem::setTitle (const QwtText & title)

Set a new title

Parameters:

title Title

See also:

title()

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

Show/Hide the item

Parameters:

on 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 ( QwtPlot::xBottom or QwtPlot::xTop )

See also:

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

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

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()

bool QwtPlotItem::testItemAttribute (ItemAttribute attribute) const

Test an item attribute

Parameters:

attribute Attribute type

Returns:

true/false

See also:

setItemAttribute() , ItemInterest

bool QwtPlotItem::testItemInterest (ItemInterest interest) const

Test an item interest

Parameters:

interest Interest type

Returns:

true/false

See also:

setItemInterest() , 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()

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 .

void QwtPlotItem::updateScaleDiv (const QwtScaleDiv & xScaleDiv, constQwtScaleDiv & 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 QwtPlotScaleItem , QwtPlotGrid , and QwtPlotSeriesItem .

double QwtPlotItem::z () const

Plot items are painted in increasing z-order.

Returns:

setZ() , QwtPlotDict::itemList()

Author

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