QwtPlotCurve(3)

NAME
QwtPlotCurve - A plot item, that represents a series of points.

SYNOPSIS

#include <qwt_plot_curve.h>

Inherits QwtPlotSeriesItem, and QwtSeriesStore< QPointF >.

  Public Types
enum CurveStyle { NoCurve = -1, Lines, Sticks, Steps, Dots, UserCurve = 100 }
enum CurveAttribute { Inverted = 0x01, Fitted = 0x02 }
enum LegendAttribute { LegendNoAttribute = 0x00, LegendShowLine = 0x01, LegendShowSymbol = 0x02, LegendShowBrush = 0x04 }
enum PaintAttribute { ClipPolygons = 0x01, FilterPoints = 0x02, MinimizeMemory = 0x04, ImageBuffer = 0x08 }
typedef QFlags< CurveAttribute > CurveAttributes
Curve attributes.
typedef QFlags< LegendAttribute > LegendAttributes
Legend attributes.
typedef QFlags< PaintAttribute > PaintAttributes
Paint attributes.

  Public Member Functions
QwtPlotCurve (const QString &title=QString())
QwtPlotCurve (const QwtText &title)
virtual ~QwtPlotCurve ()
Destructor.
virtual int rtti () const
void setPaintAttribute (PaintAttribute, bool on=true)
bool testPaintAttribute (PaintAttribute) const
void setLegendAttribute (LegendAttribute, bool on=true)
bool testLegendAttribute (LegendAttribute) const
void setRawSamples (const double *xData, const double *yData, int size)
Initialize the data by pointing to memory blocks which are not managed by QwtPlotCurve.
void setSamples (const double *xData, const double *yData, int size)
void setSamples (const QVector< double > &xData, const QVector< double > &yData)
Initialize data with x- and y-arrays (explicitly shared)
void setSamples (const QVector< QPointF > &)
void setSamples (QwtSeriesData< QPointF > *)
int closestPoint (const QPoint &pos, double *dist=NULL) const
double minXValue () const
boundingRect().left()
double maxXValue () const
boundingRect().right()
double minYValue () const
boundingRect().top()
double maxYValue () const
boundingRect().bottom()
void setCurveAttribute (CurveAttribute, bool on=true)
bool testCurveAttribute (CurveAttribute) const
void setPen (const QColor &, qreal width=0.0, Qt::PenStyle=Qt::SolidLine)
void setPen (const QPen &)
const QPen & pen () const
void setBrush (const QBrush &)
Assign a brush.
const QBrush & brush () const
void setBaseline (double)
Set the value of the baseline.
double baseline () const
void setStyle (CurveStyle style)
CurveStyle style () const
void setSymbol (QwtSymbol *)
Assign a symbol.
const QwtSymbol * symbol () const
void setCurveFitter (QwtCurveFitter *)
QwtCurveFitter * curveFitter () const
virtual void drawSeries (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const
virtual QwtGraphic legendIcon (int index, const QSizeF &) const

  Protected Member Functions
void init ()
Initialize internal members.
virtual void drawCurve (QPainter *, int style, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const
Draw the line part (without symbols) of a curve interval.
virtual void drawSymbols (QPainter *, const QwtSymbol &, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const
virtual void drawLines (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const
Draw lines.
virtual void drawSticks (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const
virtual void drawDots (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const
virtual void drawSteps (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const
virtual void fillCurve (QPainter *, const QwtScaleMap &, const QwtScaleMap &, const QRectF &canvasRect, QPolygonF &) const
void closePolyline (QPainter *, const QwtScaleMap &, const QwtScaleMap &, QPolygonF &) const
Complete a polygon to be a closed polygon including the area between the original polygon and the baseline.

Detailed Description

A plot item, that represents a series of points. A curve is the representation of a series of points in the x-y plane. It supports different display styles, interpolation ( f.e. spline ) and symbols.

Usage

    a) Assign curve properties
        When a curve is created, it is configured to draw black solid lines with in QwtPlotCurve::Lines style and no symbols. You can change this by calling setPen(), setStyle() and setSymbol().

    b) Connect/Assign data.
        QwtPlotCurve gets its points using a QwtSeriesData object offering a bridge to the real storage of the points ( like QAbstractItemModel ). There are several convenience classes derived from QwtSeriesData, that also store the points inside ( like QStandardItemModel ). QwtPlotCurve also offers a couple of variations of setSamples(), that build QwtSeriesData objects from arrays internally.

    c) Attach the curve to a plot
        See QwtPlotItem::attach()

Example:
    see examples/bode

See also
    QwtPointSeriesData, QwtSymbol, QwtScaleMap

Member Enumeration Documentation

  enum QwtPlotCurve::CurveAttribute
Attribute for drawing the curve

See also
    setCurveAttribute(), testCurveAttribute(), curveFitter()

Enumerator

Inverted
    For QwtPlotCurve::Steps only. Draws a step function from the right to the left.

Fitted
    Only in combination with QwtPlotCurve::Lines A QwtCurveFitter tries to interpolate/smooth the curve, before it is painted.

Note
    Curve fitting requires temporary memory for calculating coefficients and additional points. If painting in QwtPlotCurve::Fitted mode is slow it might be better to fit the points, before they are passed to QwtPlotCurve.

  enum QwtPlotCurve::CurveStyle
Curve styles.

See also
    setStyle(), style()

Enumerator

NoCurve
    Don't draw a curve. Note: This doesn't affect the symbols.

Lines
    Connect the points with straight lines. The lines might be interpolated depending on the 'Fitted' attribute. Curve fitting can be configured using setCurveFitter().

Sticks
    Draw vertical or horizontal sticks ( depending on the orientation() ) from a baseline which is defined by setBaseline().

Steps
    Connect the points with a step function. The step function is drawn from the left to the right or vice versa, depending on the QwtPlotCurve::Inverted attribute.

Dots
    Draw dots at the locations of the data points. Note: This is different from a dotted line (see setPen()), and faster as a curve in QwtPlotCurve::NoStyle style and a symbol painting a point.

UserCurve
    Styles >= QwtPlotCurve::UserCurve are reserved for derived classes of QwtPlotCurve that overload drawCurve() with additional application specific curve types.

  enum QwtPlotCurve::LegendAttribute
Attributes how to represent the curve on the legend

See also
    setLegendAttribute(), testLegendAttribute(), QwtPlotItem::legendData(), legendIcon()

Enumerator

LegendNoAttribute
    QwtPlotCurve tries to find a color representing the curve and paints a rectangle with it.

LegendShowLine
    If the style() is not QwtPlotCurve::NoCurve a line is painted with the curve pen().

LegendShowSymbol
    If the curve has a valid symbol it is painted.

LegendShowBrush
    If the curve has a brush a rectangle filled with the curve brush() is painted.

  enum QwtPlotCurve::PaintAttribute
Attributes to modify the drawing algorithm. The default setting enables ClipPolygons | FilterPoints

See also
    setPaintAttribute(), testPaintAttribute()

Enumerator

ClipPolygons
    Clip polygons before painting them. In situations, where points are far outside the visible area (f.e when zooming deep) this might be a substantial improvement for the painting performance

FilterPoints
    Tries to reduce the data that has to be painted, by sorting out duplicates, or paintings outside the visible area. Might have a notable impact on curves with many close points. Only a couple of very basic filtering algorithms are implemented.

MinimizeMemory
    Minimize memory usage that is temporarily needed for the translated points, before they get painted. This might slow down the performance of painting

ImageBuffer
    Render the points to a temporary image and paint the image. This is a very special optimization for Dots style, when having a huge amount of points. With a reasonable number of points QPainter::drawPoints() will be faster.

Constructor & Destructor Documentation

  QwtPlotCurve::QwtPlotCurve (const QString & title = QString()) [explicit]
Constructor

Parameters
    title Title of the curve

  QwtPlotCurve::QwtPlotCurve (const QwtText & title) [explicit]
Constructor

Parameters
    title Title of the curve

Member Function Documentation

  double QwtPlotCurve::baseline () const

Returns
    Value of the baseline

See also
    setBaseline()

  const QBrush & QwtPlotCurve::brush () const

Returns
    Brush used to fill the area between lines and the baseline

See also
    setBrush(), setBaseline(), baseline()

  void QwtPlotCurve::closePolyline (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, QPolygonF & polygon) const [protected]

Complete a polygon to be a closed polygon including the area between the original polygon and the baseline.

Parameters
    painter Painter
    xMap X map
    yMap Y map
    polygon Polygon to be completed

  int QwtPlotCurve::closestPoint (const QPoint & pos, double * dist = NULL) const
Find the closest curve point for a specific position

Parameters
    pos Position, where to look for the closest curve point
    dist If dist != NULL, closestPoint() returns the distance between the position and the closest curve point

Returns
    Index of the closest curve point, or -1 if none can be found ( f.e when the curve has no points )

Note
    closestPoint() implements a dumb algorithm, that iterates over all points

  QwtCurveFitter * QwtPlotCurve::curveFitter () const
Get the curve fitter. If curve fitting is disabled NULL is returned.

Returns
    Curve fitter

See also
    setCurveFitter(), Fitted

  void QwtPlotCurve::drawCurve (QPainter * painter, int style, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const [protected], [virtual]

Draw the line part (without symbols) of a curve interval.

Parameters
    painter Painter
    style curve style, see QwtPlotCurve::CurveStyle
    xMap x map
    yMap y map
    canvasRect Contents rectangle of the canvas
    from index of the first point to be painted
    to index of the last point to be painted

See also
    draw(), drawDots(), drawLines(), drawSteps(), drawSticks()

  void QwtPlotCurve::drawDots (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const [protected], [virtual]
Draw dots

Parameters
    painter Painter
    xMap x map
    yMap y map
    canvasRect Contents rectangle of the canvas
    from index of the first point to be painted
    to index of the last point to be painted

See also
    draw(), drawCurve(), drawSticks(), drawLines(), drawSteps()

  void QwtPlotCurve::drawLines (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const [protected], [virtual]

Draw lines. If the CurveAttribute Fitted is enabled a QwtCurveFitter tries to interpolate/smooth the curve, before it is painted.

Parameters
    painter Painter
    xMap x map
    yMap y map
    canvasRect Contents rectangle of the canvas
    from index of the first point to be painted
    to index of the last point to be painted

See also
    setCurveAttribute(), setCurveFitter(), draw(), drawLines(), drawDots(), drawSteps(), drawSticks()

  void QwtPlotCurve::drawSeries (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const [virtual]
Draw an interval of the curve

Parameters
    painter Painter
    xMap Maps x-values into pixel coordinates.
    yMap Maps y-values into pixel coordinates.
    canvasRect Contents rectangle of the canvas
    from Index of the first point to be painted
    to Index of the last point to be painted. If to < 0 the curve will be painted to its last point.

See also
    drawCurve(), drawSymbols(),

Implements QwtPlotSeriesItem.

  void QwtPlotCurve::drawSteps (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const [protected], [virtual]
Draw step function

The direction of the steps depends on Inverted attribute.

Parameters
    painter Painter
    xMap x map
    yMap y map
    canvasRect Contents rectangle of the canvas
    from index of the first point to be painted
    to index of the last point to be painted

See also
    CurveAttribute, setCurveAttribute(), draw(), drawCurve(), drawDots(), drawLines(), drawSticks()

  void QwtPlotCurve::drawSticks (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const [protected], [virtual]
Draw sticks

Parameters
    painter Painter
    xMap x map
    yMap y map
    canvasRect Contents rectangle of the canvas
    from index of the first point to be painted
    to index of the last point to be painted

See also
    draw(), drawCurve(), drawDots(), drawLines(), drawSteps()

  void QwtPlotCurve::drawSymbols (QPainter * painter, const QwtSymbol & symbol, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const [protected], [virtual]
Draw symbols

Parameters
    painter Painter
    symbol Curve symbol
    xMap x map
    yMap y map
    canvasRect Contents rectangle of the canvas
    from Index of the first point to be painted
    to Index of the last point to be painted

See also
    setSymbol(), drawSeries(), drawCurve()

  void QwtPlotCurve::fillCurve (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, QPolygonF & polygon) const [protected], [virtual]
Fill the area between the curve and the baseline with the curve brush

Parameters
    painter Painter
    xMap x map
    yMap y map
    canvasRect Contents rectangle of the canvas
    polygon Polygon - will be modified !

See also
    setBrush(), setBaseline(), setStyle()

  QwtGraphic QwtPlotCurve::legendIcon (int index, const QSizeF & size) const [virtual]

Returns
    Icon representing the curve on the legend

Parameters
    index Index of the legend entry ( ignored as there is only one )
    size Icon size

See also
    QwtPlotItem::setLegendIconSize(), QwtPlotItem::legendData()

Reimplemented from QwtPlotItem.

  const QPen & QwtPlotCurve::pen () const

Returns
    Pen used to draw the lines

See also
    setPen(), brush()

  int QwtPlotCurve::rtti () const [virtual]

Returns
    QwtPlotItem::Rtti_PlotCurve

Reimplemented from QwtPlotItem.

  void QwtPlotCurve::setBaseline (double value)

Set the value of the baseline. The baseline is needed for filling the curve with a brush or the Sticks drawing style.

The interpretation of the baseline depends on the orientation(). With Qt::Vertical, the baseline is interpreted as a horizontal line at y = baseline(), with Qt::Horizontal, it is interpreted as a vertical line at x = baseline().

The default value is 0.0.

Parameters
    value Value of the baseline

See also
    baseline(), setBrush(), setStyle(), QwtPlotAbstractSeriesItem::orientation()

  void QwtPlotCurve::setBrush (const QBrush & brush)

Assign a brush. In case of brush.style() != QBrush::NoBrush and style() != QwtPlotCurve::Sticks the area between the curve and the baseline will be filled.

In case !brush.color().isValid() the area will be filled by pen.color(). The fill algorithm simply connects the first and the last curve point to the baseline. So the curve data has to be sorted (ascending or descending).

Parameters
    brush New brush

See also
    brush(), setBaseline(), baseline()

  void QwtPlotCurve::setCurveAttribute (CurveAttribute attribute, bool on = true)
Specify an attribute for drawing the curve

Parameters
    attribute Curve attribute
    on On/Off

/sa testCurveAttribute(), setCurveFitter()

  void QwtPlotCurve::setCurveFitter (QwtCurveFitter * curveFitter)
Assign a curve fitter

The curve fitter 'smooths' the curve points, when the Fitted CurveAttribute is set. setCurveFitter(NULL) also disables curve fitting.

The curve fitter operates on the translated points ( = widget coordinates) to be functional for logarithmic scales. Obviously this is less performant for fitting algorithms, that reduce the number of points.

For situations, where curve fitting is used to improve the performance of painting huge series of points it might be better to execute the fitter on the curve points once and to cache the result in the QwtSeriesData object.

Parameters
    curveFitter() Curve fitter

See also
    Fitted

  void QwtPlotCurve::setLegendAttribute (LegendAttribute attribute, bool on = true)
Specify an attribute how to draw the legend icon

Parameters
    attribute Attribute
    on On/Off /sa testLegendAttribute(). legendIcon()

  void QwtPlotCurve::setPaintAttribute (PaintAttribute attribute, bool on = true)
Specify an attribute how to draw the curve

Parameters
    attribute Paint attribute
    on On/Off

See also
    testPaintAttribute()

  void QwtPlotCurve::setPen (const QColor & color, qreal width = 0.0, Qt::PenStyle style = Qt::SolidLine)
Build and assign a pen

In Qt5 the default pen width is 1.0 ( 0.0 in Qt4 ) what makes it non cosmetic ( see QPen::isCosmetic() ). This method has been introduced to hide this incompatibility.

Parameters
    color Pen color
    width Pen width
    style Pen style

See also
    pen(), brush()

  void QwtPlotCurve::setPen (const QPen & pen)
Assign a pen

Parameters
    pen New pen

See also
    pen(), brush()

  void QwtPlotCurve::setRawSamples (const double * xData, const double * yData, int size)

Initialize the data by pointing to memory blocks which are not managed by QwtPlotCurve. setRawSamples is provided for efficiency. It is important to keep the pointers during the lifetime of the underlying QwtCPointerData class.

Parameters
    xData pointer to x data
    yData pointer to y data
    size size of x and y

See also
    QwtCPointerData

  void QwtPlotCurve::setSamples (const double * xData, const double * yData, int size)
Set data by copying x- and y-values from specified memory blocks. Contrary to setRawSamples(), this function makes a 'deep copy' of the data.

Parameters
    xData pointer to x values
    yData pointer to y values
    size size of xData and yData

See also
    QwtPointArrayData

  void QwtPlotCurve::setSamples (const QVector< double > & xData, const QVector< double > & yData)

Initialize data with x- and y-arrays (explicitly shared)

Parameters
    xData x data
    yData y data

See also
    QwtPointArrayData

  void QwtPlotCurve::setSamples (const QVector< QPointF > & samples)
Initialize data with an array of points.

Parameters
    samples Vector of points

Note
    QVector is implicitly shared

    QPolygonF is derived from QVector<QPointF>

  void QwtPlotCurve::setSamples (QwtSeriesData< QPointF > * data)
Assign a series of points

setSamples() is just a wrapper for setData() without any additional value - beside that it is easier to find for the developer.

Parameters
    data Data

Warning
    The item takes ownership of the data object, deleting it when its not used anymore.

  void QwtPlotCurve::setStyle (CurveStyle style)
Set the curve's drawing style

Parameters
    style Curve style

See also
    style()

  void QwtPlotCurve::setSymbol (QwtSymbol * symbol)

Assign a symbol. The curve will take the ownership of the symbol, hence the previously set symbol will be delete by setting a new one. If symbol is NULL no symbol will be drawn.

Parameters
    symbol Symbol

See also
    symbol()

  QwtPlotCurve::CurveStyle QwtPlotCurve::style () const

Returns
    Style of the curve

See also
    setStyle()

  const QwtSymbol * QwtPlotCurve::symbol () const

Returns
    Current symbol or NULL, when no symbol has been assigned

See also
    setSymbol()

  bool QwtPlotCurve::testCurveAttribute (CurveAttribute attribute) const

Returns
    true, if attribute is enabled

See also
    setCurveAttribute()

  bool QwtPlotCurve::testLegendAttribute (LegendAttribute attribute) const

Returns
    True, when attribute is enabled

See also
    setLegendAttribute()

  bool QwtPlotCurve::testPaintAttribute (PaintAttribute attribute) const

Returns
    True, when attribute is enabled

See also
    setPaintAttribute()

Author

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