Qwt User's Guide: QwtScaleEngine Class Reference

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QwtScaleEngine Class Reference

Base class for scale engines. More...

#include <qwt_scale_engine.h>

Inheritance diagram for QwtScaleEngine:
[legend]

List of all members.

Public Types

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

Public Member Functions

 QwtScaleEngine ()
virtual ~QwtScaleEngine ()
void setAttribute (Attribute, bool on=true)
bool testAttribute (Attribute) const
void setAttributes (int)
int attributes () const
void setReference (double reference)
double reference () const
void setMargins (double lower, double upper)
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
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

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()

Constructor & Destructor Documentation

QwtScaleEngine::QwtScaleEngine (  )  [explicit]

Constructor.

QwtScaleEngine::~QwtScaleEngine (  )  [virtual]

Destructor.

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 QwtLinearScaleEngine, and QwtLog10ScaleEngine.

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 QwtLinearScaleEngine, and QwtLog10ScaleEngine.

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:
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 QwtLinearScaleEngine, and QwtLog10ScaleEngine.

double QwtScaleEngine::upperMargin (  )  const
Returns:
the margin at the upper end of the scale The default margin is 0.
See also:
setMargins()
Generated on Wed Sep 2 18:37:27 2009 for Qwt User's Guide by  doxygen 1.6.1
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