Improve the default selection of locale for QCollator

QCollator was using the default-constructed QLocale() as its default;
this locale's default was the system locale; however, that didn't pay
any attention to system settings for collation such as Unix's
environment variable LC_COLLATE or the MS-Win LOCALE_SSORTLOCALE
configuration option.

Teach the system locale back-ends to look up their relevant settings,
add QLocale::collation() as a channel via which to access that and
change no-parameter construction of QCollator to a separate
implementation (rather than the constructor taking QLocale having a
default) using it.

[ChangeLog][QtCore][QLocale] The system locale now knows what to use
for collation, QLocale::system().collation().

[ChangeLog][QtCore][QCollator] The default QCollator now uses the
system's collation locale, rather than the system locale itself.

Fixes: QTBUG-58621
Change-Id: I90f86621541385330315d1f9d6a4b982bdcea9d5
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/corelib/tools/qlocale_win.cpp b/src/corelib/tools/qlocale_win.cpp
index ebc4430046..dc904ad02d 100644
--- a/src/corelib/tools/qlocale_win.cpp
+++ b/src/corelib/tools/qlocale_win.cpp
@@ -120,6 +120,7 @@ struct QSystemLocalePrivate
     QVariant toString(const QTime &, QLocale::FormatType);
     QVariant toString(const QDateTime &, QLocale::FormatType);
     QVariant measurementSystem();
+    QVariant collation();
     QVariant amText();
     QVariant pmText();
     QVariant firstDayOfWeek();
@@ -455,6 +456,11 @@ QVariant QSystemLocalePrivate::measurementSystem()
     return QLocale::MetricSystem;
 }
 
+QVariant QSystemLocalePrivate::collation()
+{
+    return getLocaleInfo(LOCALE_SSORTLOCALE);
+}
+
 QVariant QSystemLocalePrivate::amText()
 {
     wchar_t output[15]; // maximum length including  terminating zero character for Win2003+
@@ -808,6 +814,8 @@ QVariant QSystemLocale::query(QueryType type, QVariant in = QVariant()) const
         return QVariant(QLocale::AnyScript);
     case MeasurementSystem:
         return d->measurementSystem();
+    case Collation:
+        return d->collation();
     case AMText:
         return d->amText();
     case PMText: