Qwt User's Guide  6.1.0
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QwtScaleEngine Class Referenceabstract

Base class for scale engines. More...

#include <qwt_scale_engine.h>

Inheritance diagram for QwtScaleEngine:
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Public Types

enum  Attribute {
  NoAttribute = 0x00, IncludeReference = 0x01, Symmetric = 0x02, Floating = 0x04,
  Inverted = 0x08
}
 
typedef QFlags< AttributeAttributes
 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 reference)
 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 *)
 
QwtTransformtransformation () const
 

Protected Member Functions

bool contains (const QwtInterval &, double val) const
 
QList< double > strip (const QList< double > &, const QwtInterval &) const
 
double divideInterval (double interval, int numSteps) const
 
QwtInterval buildInterval (double v) 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

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 ( uint  base = 10)
explicit

Constructor

Parameters
baseBase of the scale engine
See Also
setBase()

Member Function Documentation

QwtScaleEngine::Attributes QwtScaleEngine::attributes ( ) const
Returns
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
maxNumStepsMax. number of steps
x1First limit of the interval (In/Out)
x2Second limit of the interval (In/Out)
stepSizeStep size (Return value)

Implemented in QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.

uint QwtScaleEngine::base ( ) const
Returns
base Base of the scale engine
See Also
setBase()
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
valueInitial value
Returns
Calculated interval
bool QwtScaleEngine::contains ( const QwtInterval interval,
double  value 
) const
protected

Check if an interval "contains" a value

Parameters
intervalInterval
valueValue
Returns
True, when the value is inside the interval
double QwtScaleEngine::divideInterval ( double  intervalSize,
int  numSteps 
) const
protected

Calculate a step size for an interval size

Parameters
intervalSizeInterval size
numStepsNumber of steps
Returns
Step size
virtual QwtScaleDiv QwtScaleEngine::divideScale ( double  x1,
double  x2,
int  maxMajorSteps,
int  maxMinorSteps,
double  stepSize = 0.0 
) const
pure virtual

Calculate a scale division.

Parameters
x1First interval limit
x2Second interval limit
maxMajorStepsMaximum for the number of major steps
maxMinorStepsMaximum number of minor steps
stepSizeStep size. If stepSize == 0.0, the scaleEngine calculates one.
Returns
Calculated scale division

Implemented in QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.

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
attributeAttribute to change
onOn/Off
See Also
Attribute, testAttribute()
void QwtScaleEngine::setAttributes ( Attributes  attributes)

Change the scale attribute

Parameters
attributesSet scale attributes
See Also
Attribute, attributes()
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
baseBase of the engine
See Also
base()
void QwtScaleEngine::setMargins ( double  lower,
double  upper 
)

Specify margins at the scale's endpoints.

Parameters
lowerminimum distance between the scale's lower boundary and the smallest enclosed value
upperminimum 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
See Also
upperMargin(), lowerMargin()
void QwtScaleEngine::setReference ( double  r)

Specify a reference point.

Parameters
rnew reference value

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

See Also
Attribute
void QwtScaleEngine::setTransformation ( QwtTransform transform)

Assign a transformation

Parameters
transformTransformation

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()
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
ticksTick list
intervalInterval
Returns
Stripped tick list
bool QwtScaleEngine::testAttribute ( Attribute  attribute) const
Returns
True, if attribute is enabled.
Parameters
attributeAttribute to be tested
See Also
Attribute, setAttribute()
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()
double QwtScaleEngine::upperMargin ( ) const
Returns
the margin at the upper end of the scale The default margin is 0.
See Also
setMargins()