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QwtScaleEngine

QwtScaleEngine

Section: C Library Functions (3) Updated: 22 Mar 2009
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NAME

QwtScaleEngine - Base class for scale engines.

 

SYNOPSIS


#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 ()

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 lower, double upper)

double lowerMargin () const

double upperMargin () 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
 

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.  

Member Enumeration Documentation

 

enum QwtScaleEngine::Attribute

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()

 

Constructor & Destructor Documentation

 

QwtScaleEngine::QwtScaleEngine () [explicit]

Constructor.

 

QwtScaleEngine::~QwtScaleEngine () [virtual]

Destructor.

 

Member Function Documentation

 

int QwtScaleEngine::attributes () const

Return the scale attributes

See also:

Attribute, setAttributes(), testAttribute()

 

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.  

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]  

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()

 

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

 

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.  

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 (Attribute attribute, bool on = true)

Change a scale attribute

Parameters:

attribute Attribute to change
on On/Off

See also:

Attribute, testAttribute()

 

void QwtScaleEngine::setAttributes (int attributes)

Change the scale attribute

Parameters:

attributes Set scale attributes

See also:

Attribute, attributes()

 

void QwtScaleEngine::setMargins (double lower, double upper)

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 (double r)

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 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

 

bool QwtScaleEngine::testAttribute (Attribute attribute) const

Check if a attribute is set.

Parameters:

attribute Attribute to be tested

See also:

Attribute, setAttribute()

 

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

Returns:

a transformation

Implemented in QwtLinearScaleEngine, and QwtLog10ScaleEngine.  

double QwtScaleEngine::upperMargin () const

Returns:

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

See also:

setMargins()

 

Author

Generated automatically by Doxygen for Qwt User's Guide from the source code.


 

Index

NAME
SYNOPSIS
Public Types
Public Member Functions
Protected Member Functions
Detailed Description
Member Enumeration Documentation
enum QwtScaleEngine::Attribute
Constructor & Destructor Documentation
QwtScaleEngine::QwtScaleEngine () [explicit]
QwtScaleEngine::~QwtScaleEngine () [virtual]
Member Function Documentation
int QwtScaleEngine::attributes () const
virtual void QwtScaleEngine::autoScale (int maxNumSteps, double & x1, double & x2, double & stepSize) const [pure virtual]
QwtDoubleInterval QwtScaleEngine::buildInterval (double v) const [protected]
bool QwtScaleEngine::contains (const QwtDoubleInterval & interval, double value) const [protected]
double QwtScaleEngine::divideInterval (double intervalSize, int numSteps) const [protected]
virtual QwtScaleDiv QwtScaleEngine::divideScale (double x1, double x2, int maxMajSteps, int maxMinSteps, double stepSize = 0.0) const [pure virtual]
double QwtScaleEngine::lowerMargin () const
double QwtScaleEngine::reference () const
void QwtScaleEngine::setAttribute (Attribute attribute, bool on = true)
void QwtScaleEngine::setAttributes (int attributes)
void QwtScaleEngine::setMargins (double lower, double upper)
void QwtScaleEngine::setReference (double r)
QwtValueList QwtScaleEngine::strip (const QwtValueList & ticks, const QwtDoubleInterval & interval) const [protected]
bool QwtScaleEngine::testAttribute (Attribute attribute) const
virtual QwtScaleTransformation* QwtScaleEngine::transformation () const [pure virtual]
double QwtScaleEngine::upperMargin () const
Author

This document was created by man2html, using the manual pages.
Time: 21:53:53 GMT, April 16, 2011