Optimized QLocale to access system locale on demand.

Changed the initialization of the system locale to make construction of the
QLocale object as lightweight as possible. So now the default contructor just
creates a QLocale and QSystemLocale objects, but doesn't try to fill the cache
in the latter with data from the system and postpones it until it is actually
requested (most applications create QLocale objects on the stack and might not
even use the data from the system locale, so we don't need to initialize system
locale right away).

Reviewed-by: Thiago Macieira

4 files changed, 164 insertions, 60 deletions

diff --git a/src/corelib/tools/qlocale.cpp b/src/corelib/tools/qlocale.cpp
index ff10fa1..1df4fa0 100644
--- a/src/corelib/tools/qlocale.cpp
+++ b/src/corelib/tools/qlocale.cpp
@@ -1274,11 +1274,25 @@ QLocale QSystemLocale::fallbackLocale() const
 */
 QVariant QSystemLocale::query(QueryType type, QVariant /* in */) const
 {
-    if (type == MeasurementSystem) {
+    switch (type) {
+    case MeasurementSystem:
         return QVariant(unixGetSystemMeasurementSystem());
-    } else {
-        return QVariant();
+    case LanguageId:
+    case CountryId: {
+        QString locale = QLatin1String(envVarLocale());
+        QLocale::Language lang;
+        QLocale::Country cntry;
+        getLangAndCountry(locale, lang, cntry);
+        if (type == LanguageId)
+            return lang;
+        if (cntry == QLocale::AnyCountry)
+            return fallbackLocale().country();
+        return cntry;
     }
+    default:
+        break;
+    }
+    return QVariant();
 }
 
 #elif !defined(Q_OS_SYMBIAN)
@@ -1388,7 +1402,8 @@ QSystemLocale::QSystemLocale()
 
 /*! \internal */
 QSystemLocale::QSystemLocale(bool)
-{ }
+{
+}
 
 /*!
   Deletes the object.
@@ -1410,16 +1425,71 @@ static const QSystemLocale *systemLocale()
     return QSystemLocale_globalSystemLocale();
 }
 
+// returns the private data for the system locale. Cached data will not be
+// initialized until the updateSystemPrivate is called.
+static const QLocalePrivate *systemPrivate()
+{
+#ifndef QT_NO_SYSTEMLOCALE
+    if (!system_lp) {
+        system_lp = globalLocalePrivate();
+        // mark the locale as uninitialized system locale
+        system_lp->m_language_id = 0;
+    }
+    return system_lp;
+#else
+    return locale_data;
+#endif
+}
+
+#ifndef QT_NO_SYSTEMLOCALE
+static const QLocalePrivate *maybeSystemPrivate()
+{
+    return system_lp;
+}
+#endif
+
+static const QLocalePrivate *defaultPrivate()
+{
+    if (!default_lp)
+        default_lp = systemPrivate();
+    return default_lp;
+}
+
+bool QLocalePrivate::isUninitializedSystemLocale() const
+{
+    return this == maybeSystemPrivate() && m_language_id == 0;
+}
+
+QVariant QLocalePrivate::querySystemLocale(QSystemLocale::QueryType type, const QVariant &in) const
+{
+    QVariant res = systemLocale()->query(type, in);
+    if (res.isNull() && isUninitializedSystemLocale()) {
+        // if we were not able to get data from the system, initialize the
+        // system locale private data (which is essentially equals to this)
+        // with a fallback locale.
+        QLocalePrivate *system_private = globalLocalePrivate();
+        *system_private = *systemLocale()->fallbackLocale().d();
+        // internal cache is not initialized with values from the system, mark
+        // it as not fully initialized system locale.
+        system_private->m_language_id = 0;
+    }
+    return res;
+}
+
+// retrieves data from the system locale and caches them locally.
 void QLocalePrivate::updateSystemPrivate()
 {
     const QSystemLocale *sys_locale = systemLocale();
     if (!system_lp)
-        system_lp = globalLocalePrivate();
+        return;
+
+    // copy over the information from the fallback locale and modify
     *system_lp = *sys_locale->fallbackLocale().d();
 
     QVariant res = sys_locale->query(QSystemLocale::LanguageId, QVariant());
     if (!res.isNull())
         system_lp->m_language_id = res.toInt();
+
     res = sys_locale->query(QSystemLocale::CountryId, QVariant());
     if (!res.isNull())
         system_lp->m_country_id = res.toInt();
@@ -1446,26 +1516,6 @@ void QLocalePrivate::updateSystemPrivate()
 }
 #endif
 
-static const QLocalePrivate *systemPrivate()
-{
-#ifndef QT_NO_SYSTEMLOCALE
-    // copy over the information from the fallback locale and modify
-    if (!system_lp || system_lp->m_language_id == 0)
-        QLocalePrivate::updateSystemPrivate();
-
-    return system_lp;
-#else
-    return locale_data;
-#endif
-}
-
-static const QLocalePrivate *defaultPrivate()
-{
-    if (!default_lp)
-        default_lp = systemPrivate();
-    return default_lp;
-}
-
 static QString getLocaleListData(const ushort *data, int size, int index)
 {
     static const ushort separator = ';';
@@ -2283,7 +2333,12 @@ void QLocale::setDefault(const QLocale &locale)
 */
 QLocale::Language QLocale::language() const
 {
-    return Language(d()->languageId());
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return Language(dd->languageId());
 }
 
 /*!
@@ -2293,7 +2348,12 @@ QLocale::Language QLocale::language() const
 */
 QLocale::Country QLocale::country() const
 {
-    return Country(d()->countryId());
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return Country(dd->countryId());
 }
 
 /*!
@@ -2631,8 +2691,8 @@ QString QLocale::toString(const QDate &date, FormatType format) const
         return QString();
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(format == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(format == LongFormat
                                              ? QSystemLocale::DateToStringLong : QSystemLocale::DateToStringShort,
                                              date);
         if (!res.isNull())
@@ -2726,8 +2786,8 @@ QString QLocale::toString(const QDateTime &dateTime, FormatType format) const
         return QString();
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(format == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(format == LongFormat
                                              ? QSystemLocale::DateTimeToStringLong
                                              : QSystemLocale::DateTimeToStringShort,
                                              dateTime);
@@ -2752,8 +2812,8 @@ QString QLocale::toString(const QTime &time, FormatType format) const
         return QString();
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(format == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(format == LongFormat
                                              ? QSystemLocale::TimeToStringLong : QSystemLocale::TimeToStringShort,
                                              time);
         if (!res.isNull())
@@ -2779,8 +2839,8 @@ QString QLocale::toString(const QTime &time, FormatType format) const
 QString QLocale::dateFormat(FormatType format) const
 {
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(format == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(format == LongFormat
                                              ? QSystemLocale::DateFormatLong : QSystemLocale::DateFormatShort,
                                              QVariant());
         if (!res.isNull())
@@ -2816,8 +2876,8 @@ QString QLocale::dateFormat(FormatType format) const
 QString QLocale::timeFormat(FormatType format) const
 {
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(format == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(format == LongFormat
                                              ? QSystemLocale::TimeFormatLong : QSystemLocale::TimeFormatShort,
                                              QVariant());
         if (!res.isNull())
@@ -2853,8 +2913,8 @@ QString QLocale::timeFormat(FormatType format) const
 QString QLocale::dateTimeFormat(FormatType format) const
 {
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(format == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(format == LongFormat
                                              ? QSystemLocale::DateTimeFormatLong
                                              : QSystemLocale::DateTimeFormatShort,
                                              QVariant());
@@ -3021,7 +3081,12 @@ QDateTime QLocale::toDateTime(const QString &string, const QString &format) cons
 */
 QChar QLocale::decimalPoint() const
 {
-    return d()->decimal();
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return dd->decimal();
 }
 
 /*!
@@ -3031,7 +3096,12 @@ QChar QLocale::decimalPoint() const
 */
 QChar QLocale::groupSeparator() const
 {
-    return d()->group();
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return dd->group();
 }
 
 /*!
@@ -3041,7 +3111,12 @@ QChar QLocale::groupSeparator() const
 */
 QChar QLocale::percent() const
 {
-    return d()->percent();
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return dd->percent();
 }
 
 /*!
@@ -3051,7 +3126,12 @@ QChar QLocale::percent() const
 */
 QChar QLocale::zeroDigit() const
 {
-    return d()->zero();
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return dd->zero();
 }
 
 /*!
@@ -3061,7 +3141,12 @@ QChar QLocale::zeroDigit() const
 */
 QChar QLocale::negativeSign() const
 {
-    return d()->minus();
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return dd->minus();
 }
 
 /*!
@@ -3071,7 +3156,12 @@ QChar QLocale::negativeSign() const
 */
 QChar QLocale::positiveSign() const
 {
-    return d()->plus();
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return dd->plus();
 }
 
 /*!
@@ -3081,7 +3171,12 @@ QChar QLocale::positiveSign() const
 */
 QChar QLocale::exponential() const
 {
-    return d()->exponential();
+    const QLocalePrivate *dd = d();
+#ifndef QT_NO_SYSTEMLOCALE
+    if (dd->isUninitializedSystemLocale())
+        QLocalePrivate::updateSystemPrivate();
+#endif
+    return dd->exponential();
 }
 
 static bool qIsUpper(char c)
@@ -3200,8 +3295,8 @@ QString QLocale::monthName(int month, FormatType type) const
         return QString();
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(type == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(type == LongFormat
                                              ? QSystemLocale::MonthNameLong : QSystemLocale::MonthNameShort,
                                              month);
         if (!res.isNull())
@@ -3246,8 +3341,8 @@ QString QLocale::standaloneMonthName(int month, FormatType type) const
         return QString();
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(type == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(type == LongFormat
                                              ? QSystemLocale::MonthNameLong : QSystemLocale::MonthNameShort,
                                              month);
         if (!res.isNull())
@@ -3293,8 +3388,8 @@ QString QLocale::dayName(int day, FormatType type) const
         return QString();
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(type == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(type == LongFormat
                                              ? QSystemLocale::DayNameLong : QSystemLocale::DayNameShort,
                                              day);
         if (!res.isNull())
@@ -3342,8 +3437,8 @@ QString QLocale::standaloneDayName(int day, FormatType type) const
         return QString();
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(type == LongFormat
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(type == LongFormat
                                              ? QSystemLocale::DayNameLong : QSystemLocale::DayNameShort,
                                              day);
         if (!res.isNull())
@@ -3387,8 +3482,8 @@ QLocale::MeasurementSystem QLocale::measurementSystem() const
     bool found = false;
 
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(QSystemLocale::MeasurementSystem, QVariant());
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(QSystemLocale::MeasurementSystem, QVariant());
         if (!res.isNull()) {
             meas = MeasurementSystem(res.toInt());
             found = true;
@@ -3415,8 +3510,8 @@ QLocale::MeasurementSystem QLocale::measurementSystem() const
 QString QLocale::amText() const
 {
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(QSystemLocale::AMText, QVariant());
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(QSystemLocale::AMText, QVariant());
         if (!res.isNull())
             return res.toString();
     }
@@ -3435,8 +3530,8 @@ QString QLocale::amText() const
 QString QLocale::pmText() const
 {
 #ifndef QT_NO_SYSTEMLOCALE
-    if (d() == systemPrivate()) {
-        QVariant res = systemLocale()->query(QSystemLocale::PMText, QVariant());
+    if (d() == maybeSystemPrivate()) {
+        QVariant res = d()->querySystemLocale(QSystemLocale::PMText, QVariant());
         if (!res.isNull())
             return res.toString();
     }
diff --git a/src/corelib/tools/qlocale.h b/src/corelib/tools/qlocale.h
index e854c84..9b7b214 100644
--- a/src/corelib/tools/qlocale.h
+++ b/src/corelib/tools/qlocale.h
@@ -638,6 +638,7 @@ public:
         ;
 private:
     friend struct QLocalePrivate;
+
     // ### We now use this field to pack an index into locale_data and NumberOptions.
     // ### Qt 5: change to a QLocaleData *d; uint numberOptions.
     union {
diff --git a/src/corelib/tools/qlocale_p.h b/src/corelib/tools/qlocale_p.h
index ecf79e9..b1bdea7 100644
--- a/src/corelib/tools/qlocale_p.h
+++ b/src/corelib/tools/qlocale_p.h
@@ -132,6 +132,8 @@ public:
                           CharBuff *result) const;
     inline char digitToCLocale(const QChar &c) const;
 
+    inline bool isUninitializedSystemLocale() const;
+    QVariant querySystemLocale(QSystemLocale::QueryType type, const QVariant &in) const;
     static void updateSystemPrivate();
 
     enum NumberMode { IntegerMode, DoubleStandardMode, DoubleScientificMode };
diff --git a/tests/auto/qlocale/tst_qlocale.cpp b/tests/auto/qlocale/tst_qlocale.cpp
index 3dc4dad..8dd5fbb 100644
--- a/tests/auto/qlocale/tst_qlocale.cpp
+++ b/tests/auto/qlocale/tst_qlocale.cpp
@@ -158,9 +158,15 @@ void tst_QLocale::ctor()
     QCoreApplication app(argc, (char**)&argv);
 #endif
     QLocale default_locale = QLocale::system();
+
+    QVERIFY(!default_locale.monthName(1, QLocale::LongFormat).isEmpty());
+    QVERIFY(!default_locale.monthName(1, QLocale::ShortFormat).isEmpty());
+    QVERIFY(default_locale.language() != 0);
+
     QLocale::Language default_lang = default_locale.language();
     QLocale::Country default_country = default_locale.country();
 
+
     qDebug("Default: %s/%s", QLocale::languageToString(default_lang).toLatin1().constData(),
             QLocale::countryToString(default_country).toLatin1().constData());