QwtPlotItem(3) Qwt User's Guide QwtPlotItem(3)

QwtPlotItem - Base class for items on the plot canvas.

#include <qwt_plot_item.h>

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


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_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
typedef QFlags< ItemInterest > ItemInterests
typedef QFlags< RenderHint > RenderHints


QwtPlotItem ()
QwtPlotItem (const QString &title)
QwtPlotItem (const QwtText &title)
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 (QwtAxisId xAxis, QwtAxisId yAxis)
void setXAxis (QwtAxisId)
QwtAxisId xAxis () const
Return xAxis. void setYAxis (QwtAxisId)
QwtAxisId 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


QwtGraphic defaultIcon (const QBrush &, const QSizeF &) const
Return a default icon from a brush.

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.

Definition at line 66 of file qwt_plot_item.h.

typedef QFlags<ItemAttribute > QwtPlotItem::ItemAttributes

An ORed combination of ItemAttribute values.

Definition at line 167 of file qwt_plot_item.h.

typedef QFlags<ItemInterest > QwtPlotItem::ItemInterests

An ORed combination of ItemInterest values.

Definition at line 200 of file qwt_plot_item.h.

typedef QFlags<RenderHint > QwtPlotItem::RenderHints

An ORed combination of RenderHint values.

Definition at line 209 of file qwt_plot_item.h.

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

The item is represented on the legend.
The boundingRect() of the item is included in the autoscaling calculation as long as its width or height is >= 0.0.
The item needs extra space to display something outside its bounding rectangle.

See also

getCanvasMarginHint()

Definition at line 147 of file qwt_plot_item.h.

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

The item is interested in updates of the scales

See also

updateScaleDiv()
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()

Definition at line 179 of file qwt_plot_item.h.

enum QwtPlotItem::RenderHint

Render hints.

Enumerator

Enable antialiasing.

Definition at line 203 of file qwt_plot_item.h.

enum QwtPlotItem::RttiValues

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

Enumerator

Unspecific value, that can be used, when it doesn't matter.
For QwtPlotGrid.
For QwtPlotScaleItem.
For QwtPlotLegendItem.
For QwtPlotMarker.
For QwtPlotCurve.
For QwtPlotSpectroCurve.
For QwtPlotIntervalCurve.
For QwtPlotHistogram.
For QwtPlotSpectrogram.
For QwtPlotGraphicItem, QwtPlotSvgItem.
For QwtPlotTradingCurve.
For QwtPlotBarChart.
For QwtPlotMultiBarChart.
For QwtPlotShapeItem.
For QwtPlotTextLabel.
For QwtPlotZoneItem.
For QwtPlotVectorField.
Values >= Rtti_PlotUserItem are reserved for plot items not implemented in the Qwt library.

Definition at line 75 of file qwt_plot_item.h.

Constructor

Definition at line 55 of file qwt_plot_item.cpp.

Constructor

Parameters

title Title of the item

Definition at line 64 of file qwt_plot_item.cpp.

Constructor

Parameters

title Title of the item

Definition at line 74 of file qwt_plot_item.cpp.

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()

Definition at line 98 of file qwt_plot_item.cpp.

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, QwtPlotVectorField, QwtPlotTradingCurve, QwtPlotShapeItem, QwtPlotSeriesItem, QwtPlotRasterItem, QwtPlotMultiBarChart, QwtPlotMarker, QwtPlotIntervalCurve, QwtPlotHistogram, QwtPlotGraphicItem, and QwtPlotBarChart.

Definition at line 568 of file qwt_plot_item.cpp.

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

Definition at line 422 of file qwt_plot_item.cpp.

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

See also

attach()

Definition at line 119 of file qwt_plot_item.cpp.

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

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.

Definition at line 595 of file qwt_plot_item.cpp.

Returns

true if visible

See also

setVisible(), show(), hide()

Definition at line 470 of file qwt_plot_item.cpp.

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

See also

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

Definition at line 481 of file qwt_plot_item.cpp.

Update the legend of the parent plot.

See also

QwtPlot::updateLegend(), itemChanged()

Definition at line 491 of file qwt_plot_item.cpp.

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.

Definition at line 626 of file qwt_plot_item.cpp.

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

Definition at line 402 of file qwt_plot_item.cpp.

Returns

Legend icon size

See also

setLegendIconSize(), legendIcon()

Definition at line 386 of file qwt_plot_item.cpp.

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

Definition at line 720 of file qwt_plot_item.cpp.

Returns

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

Definition at line 360 of file qwt_plot_item.cpp.

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, QwtPlotVectorField, QwtPlotTradingCurve, QwtPlotTextLabel, QwtPlotSpectrogram, QwtPlotSpectroCurve, QwtPlotShapeItem, QwtPlotScaleItem, QwtPlotMultiBarChart, QwtPlotMarker, QwtPlotLegendItem, QwtPlotIntervalCurve, QwtPlotHistogram, QwtPlotGrid, QwtPlotGraphicItem, QwtPlotCurve, and QwtPlotBarChart.

Definition at line 136 of file qwt_plot_item.cpp.

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

Definition at line 705 of file qwt_plot_item.cpp.

Set X and Y axis

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

Parameters

xAxisId X Axis
yAxisId Y Axis

See also

setXAxis(), setYAxis(), xAxis(), yAxis()

Definition at line 507 of file qwt_plot_item.cpp.

Toggle an item attribute

Parameters

attribute Attribute type
on true/false

See also

testItemAttribute(), ItemInterest

Definition at line 228 of file qwt_plot_item.cpp.

Toggle an item interest

Parameters

interest Interest type
on true/false

See also

testItemInterest(), ItemAttribute

Definition at line 279 of file qwt_plot_item.cpp.

Set the size of the legend icon

The default setting is 8x8 pixels

Parameters

size Size

See also

legendIconSize(), legendIcon()

Definition at line 373 of file qwt_plot_item.cpp.

Toggle an render hint

Parameters

hint Render hint
on true/false

See also

testRenderHint(), RenderHint

Definition at line 312 of file qwt_plot_item.cpp.

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 )

Definition at line 350 of file qwt_plot_item.cpp.

Set a new title

Parameters

title Title

See also

title()

Definition at line 187 of file qwt_plot_item.cpp.

Set a new title

Parameters

title Title

See also

title()

Definition at line 198 of file qwt_plot_item.cpp.

Show/Hide the item

Parameters

on Show if true, otherwise hide

See also

isVisible(), show(), hide()

Definition at line 457 of file qwt_plot_item.cpp.

Set the X axis

The item will painted according to the coordinates its Axes.

Parameters

axisId X Axis

See also

setAxes(), setYAxis(), xAxis()

Definition at line 526 of file qwt_plot_item.cpp.

Set the Y axis

The item will painted according to the coordinates its Axes.

Parameters

axisId Y Axis

See also

setAxes(), setXAxis(), yAxis()

Definition at line 543 of file qwt_plot_item.cpp.

Set the z value. Plot items are painted in increasing z-order.

Parameters

z Z-value

See also

z(), QwtPlotDict::itemList()

Definition at line 165 of file qwt_plot_item.cpp.

Test an item attribute

Parameters

attribute Attribute type

Returns

true/false

See also

setItemAttribute(), ItemInterest

Definition at line 266 of file qwt_plot_item.cpp.

Test an item interest

Parameters

interest Interest type

Returns

true/false

See also

setItemInterest(), ItemAttribute

Definition at line 299 of file qwt_plot_item.cpp.

Test a render hint

Parameters

hint Render hint

Returns

true/false

See also

setRenderHint(), RenderHint

Definition at line 332 of file qwt_plot_item.cpp.

Returns

Title of the item

See also

setTitle()

Definition at line 215 of file qwt_plot_item.cpp.

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.

Definition at line 690 of file qwt_plot_item.cpp.

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.

Definition at line 665 of file qwt_plot_item.cpp.

Plot items are painted in increasing z-order.

Returns

setZ(), QwtPlotDict::itemList()

Definition at line 152 of file qwt_plot_item.cpp.

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