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Work round ICU disagreeing with TZDB about zone transitions

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Since the TZ backend resorts to ICU for display names, we got
inconsistent results if they disagree about when transitions happened.
Also, ICU uses the current (or only recent history) names for the
zone, so one currently not doing DST (Africa/Tripoli) doesn't get a
report of its DST name at a historical time when it did DST (but ICU
doesn't know about it). Since the ICU backend, in any case, doesn't
override the displayName(qint64, ...), we can simply use the QTZP base
version instead of overloading in the TZ back-end, so we only delegate
to ICU when it might actually help. This also saves duplicating some
locking and lazy-initialization code.

In the process, turn a unique lock into a scoped lock within a
suitable scope. Also, make a comment more grammatical and less
verbose.

Change-Id: Iaaed1fb6a380be8b4258c43cbc4bacd5784345fb
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
This commit is contained in:
Edward Welbourne 2023-10-24 15:48:57 +02:00
parent 358745d7de
commit 1e74f67e54
3 changed files with 16 additions and 34 deletions
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3
src/corelib/time/qtimezoneprivate_p.h
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@ -290,9 +290,6 @@ public:
QLocale::Territory territory() const override; QLocale::Territory territory() const override;
QString comment() const override; QString comment() const override;
QString displayName(qint64 atMSecsSinceEpoch,
QTimeZone::NameType nameType,
const QLocale &locale) const override;
QString displayName(QTimeZone::TimeType timeType, QString displayName(QTimeZone::TimeType timeType,
QTimeZone::NameType nameType, QTimeZone::NameType nameType,
const QLocale &locale) const override; const QLocale &locale) const override;

41
src/corelib/time/qtimezoneprivate_tz.cpp
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@ -1022,46 +1022,27 @@ QString QTzTimeZonePrivate::comment() const
return QString::fromUtf8(tzZones->value(m_id).comment); return QString::fromUtf8(tzZones->value(m_id).comment);
} }
QString QTzTimeZonePrivate::displayName(qint64 atMSecsSinceEpoch,
QTimeZone::NameType nameType,
const QLocale &locale) const
{
#if QT_CONFIG(icu)
auto lock = qt_unique_lock(s_icu_mutex);
if (!m_icu)
m_icu = new QIcuTimeZonePrivate(m_id);
// TODO small risk may not match if tran times differ due to outdated files
// TODO Some valid TZ names are not valid ICU names, use translation table?
if (m_icu->isValid())
return m_icu->displayName(atMSecsSinceEpoch, nameType, locale);
lock.unlock();
#else
Q_UNUSED(nameType);
Q_UNUSED(locale);
#endif
// Fall back to base-class:
return QTimeZonePrivate::displayName(atMSecsSinceEpoch, nameType, locale);
}
QString QTzTimeZonePrivate::displayName(QTimeZone::TimeType timeType, QString QTzTimeZonePrivate::displayName(QTimeZone::TimeType timeType,
QTimeZone::NameType nameType, QTimeZone::NameType nameType,
const QLocale &locale) const const QLocale &locale) const
{ {
// TZ DB lacks localized names (it only has IANA IDs), so delegate to ICU
// for those, when available.
#if QT_CONFIG(icu) #if QT_CONFIG(icu)
auto lock = qt_unique_lock(s_icu_mutex); {
if (!m_icu) auto lock = qt_scoped_lock(s_icu_mutex);
m_icu = new QIcuTimeZonePrivate(m_id); // TODO Some valid TZ names are not valid ICU names, use translation table?
// TODO small risk may not match if tran times differ due to outdated files if (!m_icu)
// TODO Some valid TZ names are not valid ICU names, use translation table? m_icu = new QIcuTimeZonePrivate(m_id);
if (m_icu->isValid()) if (m_icu->isValid())
return m_icu->displayName(timeType, nameType, locale); return m_icu->displayName(timeType, nameType, locale);
lock.unlock(); }
#else #else
Q_UNUSED(timeType); Q_UNUSED(timeType);
Q_UNUSED(nameType); Q_UNUSED(nameType);
Q_UNUSED(locale); Q_UNUSED(locale);
#endif #endif
// If no ICU available then have to use abbreviations instead // If ICU is unavailable, fall back to abbreviations.
// Abbreviations don't have GenericTime // Abbreviations don't have GenericTime
if (timeType == QTimeZone::GenericTime) if (timeType == QTimeZone::GenericTime)
timeType = QTimeZone::StandardTime; timeType = QTimeZone::StandardTime;

6
tests/auto/corelib/text/qlocale/tst_qlocale.cpp
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@ -173,7 +173,11 @@ tst_QLocale::tst_QLocale()
// Some tests are specific to CET, test if it applies: // Some tests are specific to CET, test if it applies:
: europeanTimeZone( : europeanTimeZone(
QDate(2013, 1, 1).startOfDay().offsetFromUtc() == 3600 QDate(2013, 1, 1).startOfDay().offsetFromUtc() == 3600
&& QDate(2013, 6, 1).startOfDay().offsetFromUtc() == 7200) && QDate(2013, 6, 1).startOfDay().offsetFromUtc() == 7200
// ICU in a zone not currently doing DST may ignore any historical DST
// excursions in its display-names (Africa/Tripoli).
&& QDate(QDate::currentDate().year(), 1, 1).startOfDay().offsetFromUtc() == 3600
&& QDate(QDate::currentDate().year(), 7, 1).startOfDay().offsetFromUtc() == 7200)
{ {
qRegisterMetaType<QLocale::FormatType>("QLocale::FormatType"); qRegisterMetaType<QLocale::FormatType>("QLocale::FormatType");
} }