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QwtScaleEngine(3) Qwt User's Guide QwtScaleEngine(3)

QwtScaleEngine -

#include <qwt_scale_engine.h>

Inherited by QwtLinearScaleEngine, and QwtLog10ScaleEngine.


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


QwtScaleEngine ()
virtual ~QwtScaleEngine ()
int 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 (int)
void setMargins (double lower, double upper)
void setReference (double reference)
bool testAttribute (Attribute) const
virtual QwtScaleTransformation * transformation () const =0
double upperMargin () const


QwtDoubleInterval buildInterval (double v) const
bool contains (const QwtDoubleInterval &, double val) const
double divideInterval (double interval, int numSteps) const
QwtValueList strip (const QwtValueList &, const QwtDoubleInterval &) const

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.

  • 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()

Return the scale attributes

See also:

Attribute, setAttributes(), testAttribute()

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 QwtLog10ScaleEngine, and QwtLinearScaleEngine.

QwtDoubleInterval QwtScaleEngine::buildInterval (doublev) 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]

Check if an interval 'contains' a value

Parameters:

interval Interval
value Value

See also:

QwtScaleArithmetic::compareEps()

Calculate a step size for an interval size

Parameters:

intervalSize Interval size
numSteps Number of steps

Returns:

Step size

virtual QwtScaleDiv QwtScaleEngine::divideScale (doublex1, doublex2, intmaxMajSteps, intmaxMinSteps, doublestepSize = 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 QwtLog10ScaleEngine, and QwtLinearScaleEngine.

Returns:

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

See also:

setMargins()

Returns:

the reference value

See also:

setReference(), setAttribute()

Change a scale attribute

Parameters:

attribute Attribute to change
on On/Off

See also:

Attribute, testAttribute()

Change the scale attribute

Parameters:

attributes Set scale attributes

See also:

Attribute, attributes()

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()

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

Remove ticks from a list, that are not inside an interval

Parameters:

ticks Tick list
interval Interval

Returns:

Stripped tick list

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 QwtLog10ScaleEngine, and QwtLinearScaleEngine.

Returns:

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

See also:

setMargins()

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Tue Nov 20 2012 Version 5.2.3