QwtScaleEngine

Section: C Library Functions (3) Updated: 22 Mar 2009 Local index Up

NAME

QwtScaleEngine - Base class for scale engines.

SYNOPSIS

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: