QwtPlotItem(3)

NAME
QwtPlotItem - Base class for items on the plot canvas.

SYNOPSIS

#include <qwt_plot_item.h>

Inherits QwtLegendItemManager.

Inherited by QwtPlotCurve, QwtPlotGrid, QwtPlotMarker, QwtPlotRasterItem, QwtPlotScaleItem, and QwtPlotSvgItem.

  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:
    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

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

See also:
    QwtPlot::updateAxes()

Reimplemented in QwtPlotGrid, and QwtPlotScaleItem.

  int QwtPlotItem::xAxis () const

Return xAxis.

  int QwtPlotItem::yAxis () const

Return yAxis.

  double QwtPlotItem::z () const

Plot items are painted in increasing z-order.

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

Author

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