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NAME

       QwtScaleEngine -

SYNOPSIS

       #include <qwt_scale_engine.h>

       Inherited by QwtLinearScaleEngine, and QwtLog10ScaleEngine.

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

   Public Member Functions
       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

   Protected Member Functions
       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

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()

Member Function Documentation

   int QwtScaleEngine::attributes () const
       Return the scale attributes

       See also:
           Attribute, setAttributes(), testAttribute()

   virtual void QwtScaleEngine::autoScale (intmaxNumSteps, 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 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]

   bool QwtScaleEngine::contains (const QwtDoubleInterval &interval, doublevalue) const
       [protected]
       Check if an interval 'contains' a value

       Parameters:
           interval Interval
           value Value

       See also:
           QwtScaleArithmetic::compareEps()

   double QwtScaleEngine::divideInterval (doubleintervalSize, intnumSteps) 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 (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.

   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 (Attributeattribute, boolon = true)
       Change a scale attribute

       Parameters:
           attribute Attribute to change
           on On/Off

       See also:
           Attribute, testAttribute()

   void QwtScaleEngine::setAttributes (intattributes)
       Change the scale attribute

       Parameters:
           attributes Set scale attributes

       See also:
           Attribute, attributes()

   void QwtScaleEngine::setMargins (doublelower, doubleupper)
       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()
   void QwtScaleEngine::setReference (doubler)
       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 (Attributeattribute) 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 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()

Author

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