Qwt User's Guide
QwtScaleEngine Class Reference

Base class for scale engines. More...

#include <qwt_scale_engine.h>

Inheritance diagram for QwtScaleEngine:

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.
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 maxMajorSteps, int maxMinorSteps, double stepSize=0.0) const =0
 Calculate a scale division.
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.

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

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()

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

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()

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()

List of all members.

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