Base class for scale engines. More...

#include <qwt_scale_engine.h>

Inheritance diagram for QwtScaleEngine:

Collaboration diagram for QwtScaleEngine:

Classes
class	PrivateData
Public Types
enum	Attribute { NoAttribute = 0, IncludeReference = 1, Symmetric = 2, Floating = 4, Inverted = 8 }
Public Member Functions
	QwtScaleEngine ()
	Constructor.
virtual	~QwtScaleEngine ()
	Destructor.
void	setAttribute (Attribute, bool on=true)
bool	testAttribute (Attribute) const
void	setAttributes (int)
int	attributes () const
void	setReference (double reference)
	Specify a reference point.
double	reference () const
void	setMargins (double lower, double upper)
	Specify margins at the scale's endpoints.
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
	Calculate a scale division.
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
	Build an interval for a value.

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.

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()

Enumerator:

NoAttribute
IncludeReference
Symmetric
Floating
Inverted

Definition at line 69 of file qwt_scale_engine.h.

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

Constructor & Destructor Documentation

QwtScaleEngine::QwtScaleEngine ( ) [explicit]

Constructor.

Definition at line 169 of file qwt_scale_engine.cpp.

{
    d_data = new PrivateData;
}

QwtScaleEngine::~QwtScaleEngine ( ) [virtual]

Destructor.

Definition at line 176 of file qwt_scale_engine.cpp.

{
    delete d_data;
}

Member Function Documentation

int QwtScaleEngine::attributes ( ) const

Return the scale attributes

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

Definition at line 357 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::attributes.

Referenced by QwtLog10ScaleEngine::divideScale(), and setAttributes().

{
    return d_data->attributes;
}

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.

Referenced by QwtPlot::updateAxes().

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.

References qwtAbs.

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

{
    const double delta = (v == 0.0) ? 0.5 : qwtAbs(0.5 * v);
    return QwtDoubleInterval(v - delta, v + delta);
}

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().

{
    if (!interval.isValid() )
        return false;
    
    if ( QwtScaleArithmetic::compareEps(value, 
        interval.minValue(), interval.width()) < 0 )
    {
        return false;
    }

    if ( QwtScaleArithmetic::compareEps(value, 
        interval.maxValue(), interval.width()) > 0 )
    {
        return false;
    }

    return true;
}

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().

{
    if ( numSteps <= 0 )
        return 0.0;

    double v = QwtScaleArithmetic::divideEps(intervalSize, numSteps);
    return QwtScaleArithmetic::ceil125(v);
}

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.

Referenced by QwtAbstractScale::rescale(), and QwtPlot::updateAxes().

double QwtScaleEngine::lowerMargin ( ) const

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

See also:: setMargins()

Definition at line 187 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::lowerMargin.

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

{ 
    return d_data->lowerMargin; 
}

double QwtScaleEngine::reference ( ) const

Returns:: the reference value

See also:: setReference(), setAttribute()

Definition at line 380 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::referenceValue.

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

{ 
    return d_data->referenceValue; 
}

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

Change a scale attribute

Parameters:

attribute	Attribute to change
on	On/Off

See also:: Attribute, testAttribute()

Definition at line 323 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::attributes.

{
    if (on)
       d_data->attributes |= attribute;
    else
       d_data->attributes &= (~attribute);
}

void QwtScaleEngine::setAttributes ( int attributes )

Change the scale attribute

Parameters:

attributes Set scale attributes

See also:: Attribute, attributes()

Definition at line 348 of file qwt_scale_engine.cpp.

References attributes(), and QwtScaleEngine::PrivateData::attributes.

Referenced by QwtLog10ScaleEngine::divideScale().

{
    d_data->attributes = 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()

Definition at line 219 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::lowerMargin, qwtMax, and QwtScaleEngine::PrivateData::upperMargin.

Referenced by QwtLog10ScaleEngine::divideScale().

{
    d_data->lowerMargin = qwtMax(lower, 0.0);
    d_data->upperMargin = qwtMax(upper, 0.0);
}

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

Definition at line 371 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::referenceValue.

Referenced by QwtLog10ScaleEngine::divideScale().

{
    d_data->referenceValue = r;
}

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(), int(), and QwtDoubleInterval::isValid().

{
    if ( !interval.isValid() || ticks.count() == 0 )
        return QwtValueList();

    if ( contains(interval, ticks.first())
        && contains(interval, ticks.last()) )
    {
        return ticks;
    }

    QwtValueList strippedTicks;
    for ( int i = 0; i < (int)ticks.count(); i++ )
    {
        if ( contains(interval, ticks[i]) )
            strippedTicks += ticks[i];
    }
    return strippedTicks;
}

bool QwtScaleEngine::testAttribute ( Attribute attribute ) const

Check if a attribute is set.

Parameters:

attribute Attribute to be tested

See also:: Attribute, setAttribute()

Definition at line 337 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::attributes.

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

{
    return bool(d_data->attributes & attribute);
}

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

Returns:: a transformation

Implemented in QwtLinearScaleEngine, and QwtLog10ScaleEngine.

Referenced by QwtAbstractScale::rescale(), and QwtPlot::updateAxes().

double QwtScaleEngine::upperMargin ( ) const

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

See also:: setMargins()

Definition at line 198 of file qwt_scale_engine.cpp.

References QwtScaleEngine::PrivateData::upperMargin.

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

{ 
    return d_data->upperMargin; 
}

The documentation for this class was generated from the following files:

QwtScaleEngine Class Reference

Classes

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation