129 lines
3.4 KiB
C++
129 lines
3.4 KiB
C++
/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************
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* Qwt Widget Library
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* Copyright (C) 1997 Josef Wilgen
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* Copyright (C) 2002 Uwe Rathmann
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the Qwt License, Version 1.0
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*****************************************************************************/
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#ifndef _QWT_DATE_H_
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#define _QWT_DATE_H_
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#include "qwt_global.h"
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#include <qdatetime.h>
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/*!
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\brief A collection of methods around date/time values
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Qt offers convenient classes for dealing with date/time values,
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but Qwt uses coordinate systems that are based on doubles.
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QwtDate offers methods to translate from QDateTime to double and v.v.
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A double is interpreted as the number of milliseconds since
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1970-01-01T00:00:00 Universal Coordinated Time - also known
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as "The Epoch".
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While the range of the Julian day in Qt4 is limited to [0, MAX_INT],
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Qt5 stores it as qint64 offering a huge range of valid dates.
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As the significance of a double is below this ( assuming a
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fraction of 52 bits ) the translation is not
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bijective with rounding errors for dates very far from Epoch.
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For a resolution of 1 ms those start to happen for dates above the
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year 144683.
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An axis for a date/time interval is expected to be aligned
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and divided in time/date units like seconds, minutes, ...
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QwtDate offers several algorithms that are needed to
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calculate these axes.
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\sa QwtDateScaleEngine, QwtDateScaleDraw, QDate, QTime
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*/
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class QWT_EXPORT QwtDate
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{
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public:
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/*!
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How to identify the first week of year differs between
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countries.
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*/
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enum Week0Type
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{
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/*!
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According to ISO 8601 the first week of a year is defined
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as "the week with the year's first Thursday in it".
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FirstThursday corresponds to the numbering that is
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implemented in QDate::weekNumber().
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*/
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FirstThursday,
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/*!
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"The week with January 1.1 in it."
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In the U.S. this definition is more common than
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FirstThursday.
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*/
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FirstDay
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};
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/*!
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Classification of an time interval
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Time intervals needs to be classified to decide how to
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align and divide it.
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*/
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enum IntervalType
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{
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//! The interval is related to milliseconds
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Millisecond,
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//! The interval is related to seconds
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Second,
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//! The interval is related to minutes
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Minute,
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//! The interval is related to hours
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Hour,
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//! The interval is related to days
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Day,
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//! The interval is related to weeks
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Week,
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//! The interval is related to months
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Month,
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//! The interval is related to years
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Year
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};
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enum
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{
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//! The Julian day of "The Epoch"
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JulianDayForEpoch = 2440588
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};
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static QDate minDate();
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static QDate maxDate();
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static QDateTime toDateTime( double value,
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Qt::TimeSpec = Qt::UTC );
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static double toDouble( const QDateTime & );
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static QDateTime ceil( const QDateTime &, IntervalType );
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static QDateTime floor( const QDateTime &, IntervalType );
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static QDate dateOfWeek0( int year, Week0Type );
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static int weekNumber( const QDate &, Week0Type );
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static int utcOffset( const QDateTime & );
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static QString toString( const QDateTime &,
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const QString & format, Week0Type );
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};
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#endif
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