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NAME

       QwtDateScaleEngine - A scale engine for date/time values.

SYNOPSIS

       #include <qwt_date_scale_engine.h>

       Inherits QwtLinearScaleEngine.

   Public Member Functions
       QwtDateScaleEngine (Qt::TimeSpec=Qt::LocalTime)
           Constructor.
       virtual ~QwtDateScaleEngine ()
           Destructor.
       void setTimeSpec (Qt::TimeSpec)
       Qt::TimeSpec timeSpec () const
       void setUtcOffset (int seconds)
       int utcOffset () const
       void setWeek0Type (QwtDate::Week0Type)
       QwtDate::Week0Type week0Type () const
       void setMaxWeeks (int)
       int maxWeeks () const
       virtual void autoScale (int maxNumSteps, double &x1, double &x2, double &stepSize) const
       virtual QwtScaleDiv divideScale (double x1, double x2, int maxMajorSteps, int
           maxMinorSteps, double stepSize=0.0) const
           Calculate a scale division for a date/time interval.
       virtual QwtDate::IntervalType intervalType (const QDateTime &, const QDateTime &, int
           maxSteps) const
       QDateTime toDateTime (double) const

   Protected Member Functions
       virtual QDateTime alignDate (const QDateTime &, double stepSize, QwtDate::IntervalType,
           bool up) const

   Additional Inherited Members

Detailed Description

       A scale engine for date/time values.

       QwtDateScaleEngine builds scales from a time intervals. Together with QwtDateScaleDraw it
       can be used for axes according to date/time values.

       Years, months, weeks, days, hours and minutes are organized in steps with non constant
       intervals. QwtDateScaleEngine classifies intervals and aligns the boundaries and tick
       positions according to this classification.

       QwtDateScaleEngine supports representations depending on Qt::TimeSpec specifications. The
       valid range for scales is limited by the range of QDateTime, that differs between Qt4 and
       Qt5.

       Datetime values are expected as the number of milliseconds since 1970-01-01T00:00:00
       Universal Coordinated Time - also known as 'The Epoch', that can be converted to QDateTime
       using QwtDate::toDateTime().

       See also:
           QwtDate, QwtPlot::setAxisScaleEngine(), QwtAbstractScale::setScaleEngine()

Constructor & Destructor Documentation

   QwtDateScaleEngine::QwtDateScaleEngine (Qt::TimeSpec timeSpec = Qt::LocalTime)
       Constructor. The engine is initialized to build scales for the given time specification.
       It classifies intervals > 4 weeks as >= Qt::Month. The first week of a year is defined
       like for QwtDate::FirstThursday.

       Parameters:
           timeSpec Time specification

       See also:
           setTimeSpec(), setMaxWeeks(), setWeek0Type()

Member Function Documentation

   QDateTime QwtDateScaleEngine::alignDate (const QDateTime & dateTime, double stepSize,
       QwtDate::IntervalType intervalType, bool up) const [protected],  [virtual]
       Align a date/time value for a step size

       For Qt::Day alignments there is no 'natural day 0' - instead the first day of the year is
       used to avoid jumping major ticks positions when panning a scale. For other alignments (
       f.e according to the first day of the month ) alignDate() has to be overloaded.

       Parameters:
           dateTime Date/time value
           stepSize Step size
           intervalType Interval type
           up When true dateTime is ceiled - otherwise it is floored

       Returns:
           Aligned date/time value

   void QwtDateScaleEngine::autoScale (int maxNumSteps, double & x1, double & x2, double &
       stepSize) const [virtual]
       Align and divide an interval

       The algorithm aligns and divides the interval into steps.

       Datetime interval divisions are usually not equidistant and the calculated stepSize can
       only be used as an approximation for the steps calculated by divideScale().

       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 (Out)

       See also:
           QwtScaleEngine::setAttribute()

       Reimplemented from QwtLinearScaleEngine.

   QwtScaleDiv QwtDateScaleEngine::divideScale (double x1, double x2, int maxMajorSteps, int
       maxMinorSteps, double stepSize = 0.0) const [virtual]
       Calculate a scale division for a date/time interval.

       Parameters:
           x1 First interval limit
           x2 Second interval limit
           maxMajorSteps Maximum for the number of major steps
           maxMinorSteps Maximum number of minor steps
           stepSize Step size. If stepSize == 0, the scaleEngine calculates one.

       Returns:
           Calculated scale division

       Reimplemented from QwtLinearScaleEngine.

   QwtDate::IntervalType QwtDateScaleEngine::intervalType (const QDateTime & minDate, const
       QDateTime & maxDate, int maxSteps) const [virtual]
       Classification of a date/time interval division

       Parameters:
           minDate Minimum ( = earlier ) of the interval
           maxDate Maximum ( = later ) of the interval
           maxSteps Maximum for the number of steps

       Returns:
           Interval classification

   int QwtDateScaleEngine::maxWeeks () const
       Returns:
           Upper limit for the number of weeks, when an interval can be classified as Qt::Week.

       See also:
           setMaxWeeks(), week0Type()

   void QwtDateScaleEngine::setMaxWeeks (int weeks)
       Set a upper limit for the number of weeks, when an interval can be classified as Qt::Week.

       The default setting is 4 weeks.

       Parameters:
           weeks Upper limit for the number of weeks

       Note:
           In business charts a year is often divided into weeks [1-52]

       See also:
           maxWeeks(), setWeek0Type()

   void QwtDateScaleEngine::setTimeSpec (Qt::TimeSpec timeSpec)
       Set the time specification used by the engine

       Parameters:
           timeSpec Time specification

       See also:
           timeSpec(), setUtcOffset(), toDateTime()

   void QwtDateScaleEngine::setUtcOffset (int seconds)
       Set the offset in seconds from Coordinated Universal Time

       Parameters:
           seconds Offset in seconds

       Note:
           The offset has no effect beside for the time specification Qt::OffsetFromUTC.

       See also:
           QDate::utcOffset(), setTimeSpec(), toDateTime()

   void QwtDateScaleEngine::setWeek0Type (QwtDate::Week0Type week0Type)
       Sets how to identify the first week of a year.

       Parameters:
           week0Type Mode how to identify the first week of a year

       See also:
           week0Type(), setMaxWeeks()

       Note:
           week0Type has no effect beside for intervals classified as QwtDate::Week.

   Qt::TimeSpec QwtDateScaleEngine::timeSpec () const
       Returns:
           Time specification used by the engine

       See also:
           setTimeSpec(), utcOffset(), toDateTime()

   QDateTime QwtDateScaleEngine::toDateTime (double value) const
       Translate a double value into a QDateTime object.

       For QDateTime result is bounded by QwtDate::minDate() and QwtDate::maxDate()

       Returns:
           QDateTime object initialized with timeSpec() and utcOffset().

       See also:
           timeSpec(), utcOffset(), QwtDate::toDateTime()

   int QwtDateScaleEngine::utcOffset () const
       Returns:
           Offset in seconds from Coordinated Universal Time

       Note:
           The offset has no effect beside for the time specification Qt::OffsetFromUTC.

       See also:
           QDate::setUtcOffset(), setTimeSpec(), toDateTime()

   QwtDate::Week0Type QwtDateScaleEngine::week0Type () const
       Returns:
           Setting how to identify the first week of a year.

       See also:
           setWeek0Type(), maxWeeks()

Author

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