diff options
Diffstat (limited to 'src/corelib/time/qcalendar.cpp')
| -rw-r--r-- | src/corelib/time/qcalendar.cpp | 106 |
1 files changed, 92 insertions, 14 deletions
diff --git a/src/corelib/time/qcalendar.cpp b/src/corelib/time/qcalendar.cpp index a355df2100..c87d4b7cf3 100644 --- a/src/corelib/time/qcalendar.cpp +++ b/src/corelib/time/qcalendar.cpp @@ -25,9 +25,8 @@ QT_BEGIN_NAMESPACE -namespace { - -struct CaseInsensitiveAnyStringViewLessThan { +struct QCalendarRegistryCaseInsensitiveAnyStringViewLessThan +{ struct is_transparent {}; bool operator()(QAnyStringView lhs, QAnyStringView rhs) const { @@ -35,8 +34,6 @@ struct CaseInsensitiveAnyStringViewLessThan { } }; -} // unnamed namespace - namespace QtPrivate { /* @@ -70,7 +67,7 @@ class QCalendarRegistry */ QFlatMap< QString, QCalendarBackend *, - CaseInsensitiveAnyStringViewLessThan, + QCalendarRegistryCaseInsensitiveAnyStringViewLessThan, QStringList, std::vector<QCalendarBackend *> > byName; @@ -501,8 +498,8 @@ Q_GLOBAL_STATIC(QtPrivate::QCalendarRegistry, calendarRegistry); base-classes for custom calendar backends, but cannot be instantiated themselves. - \sa calendarId(), QDate, QDateTime, QDateEdit, - QDateTimeEdit, QCalendarWidget + \sa calendarId(), QDate, QDateTime, QDateEdit, QDateTimeEdit, + QCalendarWidget, {The Low-Level API: Extending Qt Applications} */ /*! @@ -856,18 +853,73 @@ int QCalendarBackend::maximumMonthsInYear() const already used in QDate::dayOfWeek() to mean an invalid date). The calendar should treat the numbers used as an \c enum, whose values need not be contiguous, nor need they follow closely from the 1 through 7 of the usual - returns. It suffices that weekDayName() can recognize each such number as - identifying a distinct name, that it returns to identify the particular - intercallary day. + returns. It suffices that; + \list + \li weekDayName() can recognize each such number as identifying a distinct + name, that it returns to identify the particular intercallary day; and + \li matchCenturyToWeekday() can determine what century adjustment aligns a + given date within a century to a given day of the week, where this is + relevant and possible. + \endlist This base implementation uses the day-numbering that various calendars have borrowed off the Hebrew calendar. - \sa weekDayName(), standaloneWeekDayName(), QDate::dayOfWeek() - */ + \sa weekDayName(), standaloneWeekDayName(), QDate::dayOfWeek(), Qt::DayOfWeek +*/ int QCalendarBackend::dayOfWeek(qint64 jd) const { - return QRoundingDown::qMod(jd, 7) + 1; + return QRoundingDown::qMod<7>(jd) + 1; +} + +/*! + \since 6.7 + Adjusts century of \a parts to match \a dow. + + Preserves parts.month and parts.day while adjusting parts.year by a multiple + of 100 (taking the absence of year zero into account, when relevant) to + obtain a date for which dayOfWeek() is \a dow. Prefers smaller changes over + larger and increases to the century over decreases of the same + magnitude. Returns the Julian Day number for the selected date or + std::numeric_limits<qint64>::min(), a.k.a. QDate::nullJd(), if there is no + date matching these requirements. + + The base-class provides a brute-force implementation that steps outwards + from the given date by centures, above and below by up to 14 centuries, in + search of a matching date. This is neither computationally efficient nor + elegant but should work as advertised for calendars in which every month-day + combination does appear on all days of the week, across sufficiently many + centuries. +*/ +qint64 QCalendarBackend::matchCenturyToWeekday(const QCalendar::YearMonthDay &parts, int dow) const +{ + Q_ASSERT(parts.isValid()); + // Brute-force solution as fall-back. + const auto checkOffset = [parts, dow, this](int centuries) -> std::optional<qint64> { + // Offset parts.year by the given number of centuries: + int year = parts.year + centuries * 100; + // but take into account the effect of crossing zero, if we did: + if (!hasYearZero() && (parts.year > 0) != (year > 0)) + year += parts.year > 0 ? -1 : +1; + qint64 jd; + if (isDateValid(year, parts.month, parts.day) + && dateToJulianDay(year, parts.month, parts.day, &jd) + && dayOfWeek(jd) == dow) { + return jd; + } + return std::nullopt; + }; + // Empirically, aside from Gregorian, each calendar finds every dow within + // any 29-century run, so 14 centuries is the biggest offset we ever need. + for (int offset = 0; offset < 15; ++offset) { + if (auto jd = checkOffset(offset)) + return *jd; + if (offset) { + if (auto jd = checkOffset(-offset)) + return *jd; + } + } + return (std::numeric_limits<qint64>::min)(); } // Month and week-day name look-ups (implemented in qlocale.cpp): @@ -1428,6 +1480,32 @@ QDate QCalendar::dateFromParts(const QCalendar::YearMonthDay &parts) const } /*! + \since 6.7 + Adjusts the century of a date to match a given day of the week. + + For use when given a date's day of week, day of month, month and last two + digits of the year. Returns a QDate instance with the given \a dow as its \l + {QDate::}{dayOfWeek()}, matching the given \a parts in month and day of the + month. The returned QDate's \l {QDate::}{year()} shall differ from + \c{parts.year} by a multiple of 100, preferring small multiples over larger + and positive multiples over their negations. + + If no date matches these conditions, an invalid QDate is returned: the day + of week is incompatible with the other data given. This arises, for example, + with the Gregorian calendar, whose 400-year cycle is a whole number of weeks + long, so any given month and day of that month only ever falls, in years + with a given last two digits, on four days of the week. (In the special case + of February 29th at the turn of a century, when that is a leap year, only + one day of the week is possible: Tuesday.) +*/ +QDate QCalendar::matchCenturyToWeekday(const QCalendar::YearMonthDay &parts, int dow) const +{ + SAFE_D(); + return d && parts.isValid() + ? QDate::fromJulianDay(d->matchCenturyToWeekday(parts, dow)) : QDate(); +} + +/*! Converts a QDate to a year, month, and day of the month. The returned structure's isValid() shall be false if the calendar is unable |