Base class for scale engines. More...

#include <qwt_scale_engine.h>

Inheritance diagram for QwtScaleEngine:

[legend]

Public Types
enum	Attribute { NoAttribute = 0x00, IncludeReference = 0x01, Symmetric = 0x02, Floating = 0x04, Inverted = 0x08 }

typedef QFlags< Attribute >	Attributes
	Layout attributes.

Public Member Functions
	QwtScaleEngine (uint base=10)

virtual	~QwtScaleEngine ()
	Destructor.

void	setBase (uint base)

uint	base () const

void	setAttribute (Attribute, bool on=true)

bool	testAttribute (Attribute) const

void	setAttributes (Attributes)

Attributes	attributes () const

void	setReference (double)
	Specify a reference point. More...

double	reference () const

void	setMargins (double lower, double upper)
	Specify margins at the scale's endpoints. More...

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 maxMajorSteps, int maxMinorSteps, double stepSize=0.0) const =0
	Calculate a scale division. More...

void	setTransformation (QwtTransform *)

QwtTransform *	transformation () const

Protected Member Functions
bool	contains (const QwtInterval &, double value) const

QList< double >	strip (const QList< double > &, const QwtInterval &) const

double	divideInterval (double intervalSize, int numSteps) const

QwtInterval	buildInterval (double value) const
	Build an interval around a value. More...

Detailed Description

Base class for scale engines.

A scale engine tries to find "reasonable" ranges and step sizes for scales.

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

Qwt offers implementations for logarithmic and linear scales.

Member Enumeration Documentation

◆ Attribute

enum QwtScaleEngine::Attribute

Layout attributes

See also: setAttribute(), testAttribute(), reference(), lowerMargin(), upperMargin()

Enumerator
NoAttribute	No attributes.
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.

Constructor & Destructor Documentation

◆ QwtScaleEngine()

QwtScaleEngine::QwtScaleEngine ( uint base = 10 )

explicit

Constructor

Parameters

base	Base of the scale engine

See also: setBase()

Member Function Documentation

◆ attributes()

QwtScaleEngine::Attributes QwtScaleEngine::attributes ( ) const

Returns: Scale attributes

See also: Attribute, setAttributes(), testAttribute()

◆ autoScale()

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 QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.

◆ base()

uint QwtScaleEngine::base ( ) const

Returns: base Base of the scale engine

See also: setBase()

◆ buildInterval()

QwtInterval QwtScaleEngine::buildInterval ( double value ) const

protected

Build an interval around a value.

In case of v == 0.0 the interval is [-0.5, 0.5], otherwide it is [0.5 * v, 1.5 * v]

Parameters

value Initial value

Returns: Calculated interval

◆ contains()

bool QwtScaleEngine::contains	(	const QwtInterval &	interval,
		double	value
	)		const

protected

Check if an interval "contains" a value

Parameters

interval	Interval
value	Value

Returns: True, when the value is inside the interval

◆ divideInterval()

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

◆ divideScale()

virtual QwtScaleDiv QwtScaleEngine::divideScale	(	double	x1,
		double	x2,
		int	maxMajorSteps,
		int	maxMinorSteps,
		double	stepSize = `0.0`
	)		const

pure virtual

Calculate a scale division.

Parameters

x1	First interval limit
x2	Second interval limit
maxMajorSteps	Maximum for the number of major steps
maxMinorSteps	Maximum number of minor steps
stepSize	Step size. If stepSize == 0.0, the scaleEngine calculates one.

Returns: Calculated scale division

Implemented in QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.

◆ lowerMargin()

double QwtScaleEngine::lowerMargin ( ) const

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

See also: setMargins()

◆ reference()

double QwtScaleEngine::reference ( ) const

Returns: the reference value

See also: setReference(), setAttribute()

◆ 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()

◆ setAttributes()

void QwtScaleEngine::setAttributes ( Attributes attributes )

Change the scale attribute

Parameters

attributes Set scale attributes

See also: Attribute, attributes()

◆ setBase()

void QwtScaleEngine::setBase ( uint base )

Set the base of the scale engine

While a base of 10 is what 99.9% of all applications need certain scales might need a different base: f.e 2

The default setting is 10

Parameters

base	Base of the engine

See also: base()

◆ setMargins()

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

QwtLogScaleEngine measures the margins in decades.

See also: upperMargin(), lowerMargin()

◆ setReference()

void QwtScaleEngine::setReference ( double reference )

Specify a reference point.

Parameters

reference New reference value

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

See also: Attribute

◆ setTransformation()

void QwtScaleEngine::setTransformation ( QwtTransform * transform )

Assign a transformation

Parameters

transform Transformation

The transformation object is used as factory for clones that are returned by transformation()

The scale engine takes ownership of the transformation.

See also: QwtTransform::copy(), transformation()

◆ strip()

QList< double > QwtScaleEngine::strip	(	const QList< double > &	ticks,
		const QwtInterval &	interval
	)		const

protected

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

Parameters

ticks	Tick list
interval	Interval

Returns: Stripped tick list

◆ testAttribute()

bool QwtScaleEngine::testAttribute ( Attribute attribute ) const

Returns: True, if attribute is enabled.

Parameters

attribute Attribute to be tested

See also: Attribute, setAttribute()

◆ transformation()

QwtTransform * QwtScaleEngine::transformation ( ) const

Create and return a clone of the transformation of the engine. When the engine has no special transformation NULL is returned, indicating no transformation.

Returns: A clone of the transfomation

See also: setTransformation()

◆ upperMargin()

double QwtScaleEngine::upperMargin ( ) const

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

See also: setMargins()

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

◆ Attribute

Constructor & Destructor Documentation

◆ QwtScaleEngine()

Member Function Documentation

◆ attributes()

◆ autoScale()

◆ base()

◆ buildInterval()

◆ contains()

◆ divideInterval()

◆ divideScale()

◆ lowerMargin()

◆ reference()

◆ setAttribute()

◆ setAttributes()

◆ setBase()

◆ setMargins()

◆ setReference()

◆ setTransformation()

◆ strip()

◆ testAttribute()

◆ transformation()

◆ upperMargin()