QwtDblRange(3)

NAME
QwtDblRange - A class which controls a value within an interval.

SYNOPSIS

#include <qwt_drange.h>

Inherited by QwtCounter, and QwtSliderBase.

  Public Methods
QwtDblRange ()
virtual void fitValue (double)
virtual void incValue (int)
virtual void incPages (int)
void setPeriodic (bool tf)
void setRange (double vmin, double vmax, double vstep=0.0, int pagesize=1)
void setStep (double)
virtual void setValue (double)
double maxValue () const
double minValue () const
bool periodic () const
double step () const
int pageSize () const
double value () const

  Protected Methods
double exactValue () const
double exactPrevValue () const
double prevValue () const
virtual void valueChange ()
virtual void stepChange ()
virtual void rangeChange ()

DETAILED DESCRIPTION

A class which controls a value within an interval.

 This class is useful as a base class or a member for sliders. It represents an interval of type double within which a value can be moved. The value can be either an arbitrary point inside the interval (see QwtDblRange::setValue), or it can be fitted into a step raster (see QwtDblRange::fitValue and QwtDblRange::incValue).

As a special case, a QwtDblRange can be periodic, which means that a value outside the interval will be mapped to a value inside the interval when setValue(), fitValue(), incValue() or incPages() are called.

CONSTRUCTOR & DESTRUCTOR DOCUMENTATION

  QwtDblRange::QwtDblRange ()

Constructor.

 The range is initialized to [0.0, 100.0], the step size to 1.0, and the value to 0.0.

MEMBER FUNCTION DOCUMENTATION

  double QwtDblRange::exactPrevValue () const [protected]

Returns the exact previous value.

  double QwtDblRange::exactValue () const [protected]

Returns the exact value.

 The exact value is the value which QwtDblRange::value would return if the value were not adjusted to the step raster. It differs from the current value only if QwtDblRange::fitValue or QwtDblRange::incValue have been used before. This function is intended for internal use in derived classes.

  void QwtDblRange::fitValue (double val) [virtual]

Adjust the value to the closest point in the step raster.

Parameters:

x   value

Warning:
The value is clipped when it lies outside the range. When the range is QwtDblRange::periodic, it will be mapped to a point in the interval such that

 new value := x + n * (max. value - min. value)
 with an integer number n.

Reimplemented in QwtSliderBase.

  void QwtDblRange::incPages (int nPages) [virtual]

Increment the value by a specified number of pages.

Parameters:

nPages
    Number of pages to increment. A negative number decrements the value.

Warning:
The Page size is specified in the constructor.

  void QwtDblRange::incValue (int steps) [virtual]

Increment the value by a specified number of steps.

Parameters:

nSteps
    Number of steps to increment

Warning:
As a result of this operation, the new value will always be adjusted to the step raster.

Reimplemented in QwtSliderBase.

  double QwtDblRange::maxValue () const

Returns the value of the second border of the range.

 maxValue returns the value which has been specified as the second parameter in QwtDblRange::setRange.

See also:
setRange()

  double QwtDblRange::minValue () const

Returns the value at the first border of the range.

 minValue returns the value which has been specified as the first parameter in setRange().

See also:
setRange()

  int QwtDblRange::pageSize () const

Returns the page size in steps.

  bool QwtDblRange::periodic () const

Returns TRUE if the range is periodic.

See also:
setPeriodic()

  double QwtDblRange::prevValue () const [protected]

Returns the previous value.

  void QwtDblRange::rangeChange () [protected, virtual]

Notify a change of the range.

 This virtual function is called whenever the range changes. The default implementation does nothing.

Reimplemented in QwtSlider.

  void QwtDblRange::setPeriodic (bool tf)

Make the range periodic.

 When the range is periodic, the value will be set to a point inside the interval such that

 point = value + n * width

if the user tries to set a new value which is outside the range. If the range is nonperiodic (the default), values outside the range will be clipped.

Parameters:

tf  TRUE for a periodic range

  void QwtDblRange::setRange (double vmin, double vmax, double vstep = 0.0, int pageSize = 1)

Specify range and step size.

Parameters:

vmin
    lower boundary of the interval

vmax
    higher boundary of the interval

vstep
    step width

pageSize
    page size in steps

Warning:

A change of the range changes the value if it lies outside the new range. The current value will *not* be adjusted to the new step raster.

vmax < vmin is allowed.

If the step size is left out or set to zero, it will be set to 1/100 of the interval length.

If the step size has an absurd value, it will be corrected to a better one.

  void QwtDblRange::setStep (double vstep)

Change the step raster.

Parameters:

vstep
    new step width

Warning:
The value will not be adjusted to the new step raster.

  void QwtDblRange::setValue (double val) [virtual]

Set a new value without adjusting to the step raster.

Parameters:

x   new value

Warning:
The value is clipped when it lies outside the range. When the range is QwtDblRange::periodic, it will be mapped to a point in the interval such that

 new value := x + n * (max. value - min. value)
 with an integer number n.

Reimplemented in QwtSliderBase.

  double QwtDblRange::step () const

Returns:
the step size

See also:
QwtDblRange::setStep, QwtDblRange::setRange

  void QwtDblRange::stepChange () [protected, virtual]

Notify a change of the step size.

 This virtual function is called whenever the step size changes. The default implementation does nothing.

  double QwtDblRange::value () const

Returns the current value.

  void QwtDblRange::valueChange () [protected, virtual]

Notify a change of value.

 This virtual function is called whenever the value changes. The default implementation does nothing.

Reimplemented in QwtSliderBase, and QwtSlider.

AUTHOR

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