Clarify what QSystemLocale::fallbackLocale() is used for

Change-Id: I8f073f996505ccb42020b32fd76520ecef54e628
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/text/qlocale.cpp

@@ -707,7 +707,7 @@ static void updateSystemPrivate()
     sys_locale->query(QSystemLocale::LocaleChanged);
 
     // Populate global with fallback as basis:
-    globalLocaleData = locale_data[sys_locale->fallbackUiLocaleIndex()];
+    globalLocaleData = locale_data[sys_locale->fallbackLocaleIndex()];
 
     QVariant res = sys_locale->query(QSystemLocale::LanguageId);
     if (!res.isNull()) {
@@ -4240,7 +4240,7 @@ QStringList QLocale::uiLanguages() const
         for (const auto &entry : uiLanguages)
             locales.append(QLocale(entry));
         if (locales.isEmpty())
-            locales.append(systemLocale()->fallbackUiLocale());
+            locales.append(systemLocale()->fallbackLocale());
     } else
 #endif
     {

src/corelib/text/qlocale.qdoc

@@ -1112,13 +1112,6 @@
   \sa FormatType
 */
 
-/*!
-    \fn QLocale QSystemLocale::fallbackUiLocale() const
-
-    \since 4.6
-    Returns the fallback locale obtained from the system.
-*/
-
 /*!
     \fn QVariant QSystemLocale::query(QueryType type, QVariant in = QVariant()) const
 
@@ -1129,6 +1122,17 @@
     \sa QSystemLocale::QueryType
 */
 
+/*!
+    \fn QLocale QSystemLocale::fallbackLocale() const
+
+    \since 4.6
+
+    Returns the locale used if the system locale is not able to answer a query.
+
+    Must be a QLocale instance based on the built-in CLDR data, and should
+    match what the system locale is using as closely as that data supports.
+*/
+
 /*!
     \class QSystemLocale::CurrencyToStringArgument
     \inmodule QtCore

src/corelib/text/qlocale_mac.mm

@@ -418,7 +418,7 @@ static QVariant macQuoteString(QSystemLocale::QueryType type, QStringView str)
 
 #ifndef QT_NO_SYSTEMLOCALE
 
-QLocale QSystemLocale::fallbackUiLocale() const
+QLocale QSystemLocale::fallbackLocale() const
 {
     return QLocale(getMacLocaleName());
 }

src/corelib/text/qlocale_p.h

@@ -127,9 +127,9 @@ public:
         StandaloneMonthNameShort // QString, in: int
     };
     virtual QVariant query(QueryType type, QVariant in = QVariant()) const;
-    virtual QLocale fallbackUiLocale() const;
 
-    inline uint fallbackUiLocaleIndex() const;
+    virtual QLocale fallbackLocale() const;
+    inline uint fallbackLocaleIndex() const;
 private:
     QSystemLocale(bool);
     friend class QSystemLocaleSingleton;
@@ -428,7 +428,7 @@ public:
 };
 
 #ifndef QT_NO_SYSTEMLOCALE
-uint QSystemLocale::fallbackUiLocaleIndex() const { return fallbackUiLocale().d->m_index; }
+uint QSystemLocale::fallbackLocaleIndex() const { return fallbackLocale().d->m_index; }
 #endif
 
 template <>

src/corelib/text/qlocale_unix.cpp

@@ -133,7 +133,7 @@ static bool contradicts(const QString &maybe, const QString &known)
     return !(maybeId.acceptLanguage(knownId.language_id) && maybeId.acceptScriptCountry(knownId));
 }
 
-QLocale QSystemLocale::fallbackUiLocale() const
+QLocale QSystemLocale::fallbackLocale() const
 {
     // See man 7 locale for precedence - LC_ALL beats LC_MESSAGES beats LANG:
     QString lang = qEnvironmentVariable("LC_ALL");

src/corelib/text/qlocale_win.cpp

@@ -702,7 +702,7 @@ QString QSystemLocalePrivate::winToQtFormat(QStringView sys_fmt)
     return result;
 }
 
-QLocale QSystemLocale::fallbackUiLocale() const
+QLocale QSystemLocale::fallbackLocale() const
 {
     return QLocale(QString::fromLatin1(getWinLocaleName()));
 }
@@ -762,8 +762,8 @@ QVariant QSystemLocale::query(QueryType type, QVariant in) const
         if (type == LanguageId)
             return lid.language_id;
         if (type == ScriptId)
-            return lid.script_id ? lid.script_id : ushort(fallbackUiLocale().script());
-        return lid.country_id ? lid.country_id : ushort(fallbackUiLocale().country());
+            return lid.script_id ? lid.script_id : ushort(fallbackLocale().script());
+        return lid.country_id ? lid.country_id : ushort(fallbackLocale().country());
     }
     case MeasurementSystem:
         return d->measurementSystem();

src/plugins/platforms/android/qandroidsystemlocale.cpp

@@ -187,7 +187,7 @@ QVariant QAndroidSystemLocale::query(QueryType type, QVariant in) const
     return QVariant();
 }
 
-QLocale QAndroidSystemLocale::fallbackUiLocale() const
+QLocale QAndroidSystemLocale::fallbackLocale() const
 {
     QReadLocker locker(&m_lock);
     return m_locale;

src/plugins/platforms/android/qandroidsystemlocale.h

@@ -51,7 +51,7 @@ public:
     QAndroidSystemLocale();
 
     QVariant query(QueryType type, QVariant in) const override;
-    QLocale fallbackUiLocale() const override;
+    QLocale fallbackLocale() const override;
 
 private:
     void getLocaleFromJava() const;

tests/auto/corelib/text/qlocale/tst_qlocale.cpp

@@ -3056,7 +3056,7 @@ public:
         return QVariant();
     }
 
-    QLocale fallbackUiLocale() const override
+    QLocale fallbackLocale() const override
     {
         return m_locale;
     }