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QwtScaleEngine

NAME

QwtScaleEngine -

SYNOPSIS

Inherited by QwtLinearScaleEngine, and QwtLog10ScaleEngine.

Detailed Description

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.

Definition at line 50 of file qwt_scale_engine.h.

Public Types

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

Public Member Functions

QwtScaleEngine ()

virtual ~QwtScaleEngine ()

void setAttribute (Attribute, bool on=true)

bool testAttribute (Attribute) const

void setAttributes (int)

int attributes () const

void setReference (double reference)

double reference () const

void setMargins (double m1, double m2)

double loMargin () const

double hiMargin () 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

virtual QwtScaleTransformation * transformation () const=0

Protected Member Functions

bool contains (const QwtDoubleInterval &, double val) const

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

double divideInterval (double interval, int numSteps) const

QwtDoubleInterval buildInterval (double v) const

Member Enumeration Documentation

enum QwtScaleEngine::Attribute

see QwtScaleEngine::setAttribute, testAttribute

Definition at line 54 of file qwt_scale_engine.h.

Constructor & Destructor Documentation

QwtScaleEngine::QwtScaleEngine () [explicit]

Ctor.

Definition at line 169 of file qwt_scale_engine.cpp.

QwtScaleEngine::~QwtScaleEngine () [virtual]

Dtor.

Definition at line 176 of file qwt_scale_engine.cpp.

Member Function Documentation

void QwtScaleEngine::setAttribute (Attribute attribute, bool on = true)

Change a scale attribute

Parameters:

attribute Attribute to change
on On/Off

The behaviour of the scale engine can be changed with the following attributes:

QwtScaleEngine::IncludeReference

Build a scale which includes the reference value.

QwtScaleEngine::Symmetric

Build a scale which is symmetric to the reference value.

QwtScaleEngine::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.

QwtScaleEngine::Inverted

Turn the scale upside down.

See also:

QwtScaleEngine::testAttribute()

Definition at line 339 of file qwt_scale_engine.cpp.

bool QwtScaleEngine::testAttribute (Attribute attribute) const

Check if a attribute is set.

Parameters:

attribute Attribute to be tested

See also:

QwtScaleEngine::setAttribute() for a description of the possible options.

Definition at line 353 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::autoScale(), and QwtLinearScaleEngine::autoScale().

void QwtScaleEngine::setAttributes (int attributes)

Change the scale attribute

Parameters:

attributes Set scale attributes

See also:

QwtScaleEngine::attributes()

Definition at line 364 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::divideScale().

int QwtScaleEngine::attributes () const

Return the scale attributes

Definition at line 372 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::divideScale().

void QwtScaleEngine::setReference (double r)

Specify a reference point.

Parameters:

r new reference value

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

Definition at line 384 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::divideScale().

double QwtScaleEngine::reference () const

Returns:

the reference value

See also:

QwtScaleEngine::setReference(), QwtScaleEngine::setAttribute()

Definition at line 393 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::autoScale(), QwtLinearScaleEngine::autoScale(), and QwtLog10ScaleEngine::divideScale().

void QwtScaleEngine::setMargins (double mlo, double mhi)

Specify margins at the scale's endpoints.

Parameters:

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

QwtScaleEngine::hiMargin, QwtScaleEngine::loMargin

Definition at line 219 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::divideScale().

double QwtScaleEngine::loMargin () const

Returns:

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

See also:

QwtScaleEngine::setMargins()

Definition at line 187 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::autoScale(), QwtLinearScaleEngine::autoScale(), and QwtLog10ScaleEngine::divideScale().

double QwtScaleEngine::hiMargin () const

Returns:

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

See also:

QwtScaleEngine::setMargins()

Definition at line 198 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::autoScale(), QwtLinearScaleEngine::autoScale(), and QwtLog10ScaleEngine::divideScale().

virtual void QwtScaleEngine::autoScale (int maxNumSteps, double & x1, double & x2, double & stepSize) const [pure virtual]

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 QwtLinearScaleEngine, and QwtLog10ScaleEngine.

virtual QwtScaleDiv QwtScaleEngine::divideScale (double x1, double x2, int maxMajSteps, int maxMinSteps, double stepSize = 0.0) const [pure virtual]

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 QwtLinearScaleEngine, and QwtLog10ScaleEngine.

virtual QwtScaleTransformation* QwtScaleEngine::transformation () const [pure virtual]

Returns:

a transformation

Implemented in QwtLinearScaleEngine, and QwtLog10ScaleEngine.

bool QwtScaleEngine::contains (const QwtDoubleInterval & interval, double value) const [protected]

Check if an interval 'contains' a value

Parameters:

interval Interval
value Value

See also:

QwtScaleArithmetic::compareEps

Definition at line 251 of file qwt_scale_engine.cpp.

References QwtScaleArithmetic::compareEps(), QwtDoubleInterval::isValid(), QwtDoubleInterval::maxValue(), QwtDoubleInterval::minValue(), and QwtDoubleInterval::width().

Referenced by strip().

QwtValueList QwtScaleEngine::strip (const QwtValueList & ticks, const QwtDoubleInterval & interval) const [protected]

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

Parameters:

ticks Tick list
interval Interval

Returns:

Stripped tick list

Definition at line 280 of file qwt_scale_engine.cpp.

References contains(), and QwtDoubleInterval::isValid().

double QwtScaleEngine::divideInterval (double intervalSize, int numSteps) const [protected]

Calculate a step size for an interval size

Parameters:

intervalSize Interval size
numSteps Number of steps

Returns:

Step size

Definition at line 233 of file qwt_scale_engine.cpp.

References QwtScaleArithmetic::ceil125(), and QwtScaleArithmetic::divideEps().

Referenced by QwtLog10ScaleEngine::autoScale(), QwtLinearScaleEngine::autoScale(), QwtLog10ScaleEngine::divideScale(), and QwtLinearScaleEngine::divideScale().

QwtDoubleInterval QwtScaleEngine::buildInterval (double v) const [protected]

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]

Definition at line 309 of file qwt_scale_engine.cpp.

Referenced by QwtLog10ScaleEngine::autoScale(), and QwtLinearScaleEngine::autoScale().

Author

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