QwtScaleEngine Class Reference

#include <qwt_scale_engine.h>

Inheritance diagram for QwtScaleEngine:

List of all members.

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

---

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()

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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 QwtLog10ScaleEngine, and QwtLinearScaleEngine.

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 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	(	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 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()