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128 lines
3.5 KiB
128 lines
3.5 KiB
/* -*- 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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