Qwt User's Guide  6.0.2
Public Types | Public Member Functions | Protected Member Functions
QwtScaleEngine Class Reference

#include <qwt_scale_engine.h>

Inheritance diagram for QwtScaleEngine:
Inheritance graph
[legend]

List of all members.

Public Types

enum  Attribute {
  NoAttribute = 0x00,
  IncludeReference = 0x01,
  Symmetric = 0x02,
  Floating = 0x04,
  Inverted = 0x08
}
typedef QFlags< AttributeAttributes

Public Member Functions

 QwtScaleEngine ()
virtual ~QwtScaleEngine ()
Attributes 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 (Attributes)
void setMargins (double lower, double upper)
void setReference (double reference)
bool testAttribute (Attribute) const
virtual QwtScaleTransformationtransformation () const =0
double upperMargin () const

Protected Member Functions

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

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 (log10) and linear scales. Contributions for other types of scale engines (date/time, log2 ... ) are welcome.


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.


Member Function Documentation

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

Implemented in QwtLog10ScaleEngine, and QwtLinearScaleEngine.

QwtInterval 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 QwtInterval interval,
double  value 
) const
protected

Check if an interval "contains" a value

Parameters:
intervalInterval
valueValue
See also:
QwtScaleArithmetic::compareEps()
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  maxMajSteps,
int  maxMinSteps,
double  stepSize = 0.0 
) const
pure virtual

Calculate a scale division.

Parameters:
x1First interval limit
x2Second interval limit
maxMajStepsMaximum for the number of major steps
maxMinStepsMaximum number of minor steps
stepSizeStep 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:
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::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
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

Check if a attribute is set.

Parameters:
attributeAttribute 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()