Provided by: libqwt-doc_6.1.4-2_all 
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 [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 QwtPlotMarker, QwtPlotLegendItem, QwtPlotRasterItem, QwtPlotShapeItem,
QwtPlotSpectrogram, QwtPlotScaleItem, QwtPlotGrid, QwtPlotTextLabel, QwtPlotZoneItem,
QwtPlotSvgItem, and QwtPlotSeriesItem.
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.
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, 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 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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