Man page - qwtplotcurve(3)

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Manual

QwtPlotCurve

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, constQwtScaleMap & 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, constQRectF & 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::Horizontal, the baseline is interpreted as a horizontal line at y = baseline() , with Qt::Vertical, 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, constQVector< 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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