QwtScaleEngine (3)

#include <qwt_scale_engine.h>

Inherited by QwtLinearScaleEngine, and QwtLog10ScaleEngine.

Public Types

enum Attribute { NoAttribute = 0, IncludeReference = 1, Symmetric = 2, Floating = 4, Inverted = 8 }

Public Member Functions

QwtScaleEngine ()

virtual ~QwtScaleEngine ()

int attributes () const

virtual void autoScale (int maxNumSteps, double &x1, double &x2, double &stepSize) const =0

virtual QwtScaleDiv divideScale (double x1, double x2, int maxMajSteps, int maxMinSteps, double stepSize=0.0) const =0

double lowerMargin () const

double reference () const

void setAttribute (Attribute, bool on=true)

void setAttributes (int)

void setMargins (double lower, double upper)

void setReference (double reference)

bool testAttribute (Attribute) const

virtual QwtScaleTransformation * transformation () const =0

double upperMargin () const

Protected Member Functions

QwtDoubleInterval buildInterval (double v) const

bool contains (const QwtDoubleInterval &, double val) const

double divideInterval (double interval, int numSteps) const

QwtValueList strip (const QwtValueList &, const QwtDoubleInterval &) const

Base class for scale engines.

A scale engine trys to find 'reasonable' ranges and step sizes for scales.

The layout of the scale can be varied with setAttribute().

Qwt offers implementations for logarithmic (log10) and linear scales. Contributions for other types of scale engines (date/time, log2 ... ) are welcome.

enum \fBQwtScaleEngine::Attribute\fP

• IncludeReference

  Build a scale which includes the reference() value.

• Symmetric

  Build a scale which is symmetric to the reference() value.

• Floating

  The endpoints of the scale are supposed to be equal the outmost included values plus the specified margins (see setMargins()). If this attribute is not set, the endpoints of the scale will be integer multiples of the step size.

• Inverted

  Turn the scale upside down.

See also:

setAttribute(), testAttribute(), reference(), lowerMargin(), upperMargin()

int QwtScaleEngine::attributes () const

Return the scale attributes

See also:

Attribute, setAttributes(), testAttribute()

virtual void QwtScaleEngine::autoScale (intmaxNumSteps, double &x1, double &x2, double &stepSize) const\fC [pure virtual]\fP

Align and divide an interval

Parameters:

maxNumSteps Max. number of steps

x1 First limit of the interval (In/Out)

x2 Second limit of the interval (In/Out)

stepSize Step size (Return value)

Implemented in QwtLog10ScaleEngine, and QwtLinearScaleEngine.

\fBQwtDoubleInterval\fP QwtScaleEngine::buildInterval (doublev) const\fC [protected]\fP

Build an interval for a value. In case of v == 0.0 the interval is [-0.5, 0.5], otherwide it is [0.5 * v, 1.5 * v]

bool QwtScaleEngine::contains (const \fBQwtDoubleInterval\fP &interval, doublevalue) const\fC [protected]\fP

Check if an interval 'contains' a value

Parameters:

interval Interval

value Value

See also:

QwtScaleArithmetic::compareEps()

double QwtScaleEngine::divideInterval (doubleintervalSize, intnumSteps) const\fC [protected]\fP

Calculate a step size for an interval size

Parameters:

intervalSize Interval size

numSteps Number of steps

Returns:

Step size

virtual \fBQwtScaleDiv\fP QwtScaleEngine::divideScale (doublex1, doublex2, intmaxMajSteps, intmaxMinSteps, doublestepSize = \fC0.0\fP) const\fC [pure virtual]\fP

Calculate a scale division. Parameters:

x1 First interval limit

x2 Second interval limit

maxMajSteps Maximum for the number of major steps

maxMinSteps Maximum number of minor steps

stepSize Step size. If stepSize == 0.0, the scaleEngine calculates one.

Implemented in QwtLog10ScaleEngine, and QwtLinearScaleEngine.

double QwtScaleEngine::lowerMargin () const

Returns:

the margin at the lower end of the scale The default margin is 0.

See also:

setMargins()

double QwtScaleEngine::reference () const

Returns:

the reference value

See also:

setReference(), setAttribute()

void QwtScaleEngine::setAttribute (\fBAttribute\fPattribute, boolon = \fCtrue\fP)

Change a scale attribute

Parameters:

attribute Attribute to change

on On/Off

See also:

Attribute, testAttribute()

void QwtScaleEngine::setAttributes (intattributes)

Change the scale attribute

Parameters:

attributes Set scale attributes

See also:

Attribute, attributes()

void QwtScaleEngine::setMargins (doublelower, doubleupper)

Specify margins at the scale's endpoints. Parameters:

lower minimum distance between the scale's lower boundary and the smallest enclosed value

upper minimum distance between the scale's upper boundary and the greatest enclosed value

Margins can be used to leave a minimum amount of space between the enclosed intervals and the boundaries of the scale.

Warning:

• QwtLog10ScaleEngine measures the margins in decades.

See also:

upperMargin(), lowerMargin()

void QwtScaleEngine::setReference (doubler)

Specify a reference point. Parameters:

r new reference value

The reference point is needed if options IncludeReference or Symmetric are active. Its default value is 0.0.

See also:

Attribute

QwtValueList QwtScaleEngine::strip (const QwtValueList &ticks, const \fBQwtDoubleInterval\fP &interval) const\fC [protected]\fP

Remove ticks from a list, that are not inside an interval

Parameters:

ticks Tick list

interval Interval

Returns:

Stripped tick list

bool QwtScaleEngine::testAttribute (\fBAttribute\fPattribute) const

Check if a attribute is set.

Parameters:

attribute Attribute to be tested

See also:

Attribute, setAttribute()

virtual \fBQwtScaleTransformation\fP* QwtScaleEngine::transformation () const\fC [pure virtual]\fP

Returns:

a transformation

Implemented in QwtLog10ScaleEngine, and QwtLinearScaleEngine.

double QwtScaleEngine::upperMargin () const

Returns:

the margin at the upper end of the scale The default margin is 0.

See also:

setMargins()

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