QTranslator improvements for QLocale UI languages

To be able to make use of the new QLocale::uiLanguages property, here is a new
overload in QTranslator::load that takes QLocale object as an argument and
tries to load the translation based on educated guesses of the locale name and
file name.

Task-number: related to QTBUG-7329
Reviewed-by: Zeno Albisser

2 files changed, 155 insertions, 0 deletions

diff --git a/src/corelib/kernel/qtranslator.cpp b/src/corelib/kernel/qtranslator.cpp
index d72c1ab..bdb1d5f 100644
--- a/src/corelib/kernel/qtranslator.cpp
+++ b/src/corelib/kernel/qtranslator.cpp
@@ -47,6 +47,7 @@
 
 #include "qfileinfo.h"
 #include "qstring.h"
+#include "qstringlist.h"
 #include "qcoreapplication.h"
 #include "qcoreapplication_p.h"
 #include "qdatastream.h"
@@ -55,6 +56,7 @@
 #include "qalgorithms.h"
 #include "qhash.h"
 #include "qtranslator_p.h"
+#include "qlocale.h"
 
 #if defined(Q_OS_UNIX) && !defined(Q_OS_SYMBIAN)
 #define QT_USE_MMAP
@@ -236,6 +238,7 @@ public:
     uint contextLength;
     uint numerusRulesLength;
 
+    bool do_load(const QString &filename);
     bool do_load(const uchar *data, int len);
     QString do_translate(const char *context, const char *sourceText, const char *comment,
                          int n) const;
@@ -435,7 +438,12 @@ bool QTranslator::load(const QString & filename, const QString & directory,
     }
 
     // realname is now the fully qualified name of a readable file.
+    return d->do_load(realname);
+}
 
+bool QTranslatorPrivate::do_load(const QString &realname)
+{
+    QTranslatorPrivate *d = this;
     bool ok = false;
 
 #ifdef QT_USE_MMAP
@@ -497,6 +505,147 @@ bool QTranslator::load(const QString & filename, const QString & directory,
     return d->do_load(reinterpret_cast<const uchar *>(d->unmapPointer), d->unmapLength);
 }
 
+static QString find_translation(const QLocale & locale,
+                                const QString & filename,
+                                const QString & prefix,
+                                const QString & directory,
+                                const QString & suffix)
+{
+    QString path;
+    if (QFileInfo(filename).isRelative()) {
+        path = directory;
+        if (!path.isEmpty() && !path.endsWith(QLatin1Char('/')))
+            path += QLatin1Char('/');
+    }
+
+    QFileInfo fi;
+    QString realname;
+    QStringList fuzzyLocales;
+
+    // see http://www.unicode.org/reports/tr35/#LanguageMatching for inspiration
+
+    QStringList languages = locale.uiLanguages();
+#if defined(Q_OS_UNIX) && !defined(Q_OS_SYMBIAN)
+    for (int i = languages.size()-1; i >= 0; --i) {
+        QString lang = languages.at(i);
+        QString lowerLang = lang.toLower();
+        if (lang != lowerLang)
+            languages.insert(i+1, lowerLang);
+    }
+#endif
+
+    // try explicit locales names first
+    foreach (QString localeName, languages) {
+        localeName.replace(QLatin1Char('-'), QLatin1Char('_'));
+
+        realname = path + filename + prefix + localeName + (suffix.isNull() ? QLatin1String(".qm") : suffix);
+        fi.setFile(realname);
+        if (fi.isReadable() && fi.isFile())
+            return realname;
+
+        realname = path + filename + prefix + localeName;
+        fi.setFile(realname);
+        if (fi.isReadable() && fi.isFile())
+            return realname;
+
+        fuzzyLocales.append(localeName);
+    }
+
+    // start guessing
+    foreach (QString localeName, fuzzyLocales) {
+        for (;;) {
+            int rightmost = localeName.lastIndexOf(QLatin1Char('_'));
+            // no truncations? fail
+            if (rightmost <= 0)
+                break;
+            localeName.truncate(rightmost);
+
+            realname = path + filename + prefix + localeName + (suffix.isNull() ? QLatin1String(".qm") : suffix);
+            fi.setFile(realname);
+            if (fi.isReadable() && fi.isFile())
+                return realname;
+
+            realname = path + filename + prefix + localeName;
+            fi.setFile(realname);
+            if (fi.isReadable() && fi.isFile())
+                return realname;
+        }
+    }
+
+    if (!suffix.isNull()) {
+        realname = path + filename + suffix;
+        fi.setFile(realname);
+        if (fi.isReadable() && fi.isFile())
+            return realname;
+    }
+
+    realname = path + filename + prefix;
+    fi.setFile(realname);
+    if (fi.isReadable() && fi.isFile())
+        return realname;
+
+    realname = path + filename;
+    fi.setFile(realname);
+    if (fi.isReadable() && fi.isFile())
+        return realname;
+
+    return QString();
+}
+
+/*!
+    \since 4.8
+
+    Loads \a filename + \a prefix + \a locale name + \a suffix (".qm" if the \a
+    suffix is not specified), which may be an absolute file name or relative to
+    \a directory. Returns true if the translation is successfully loaded;
+    otherwise returns false.
+
+    The previous contents of this translator object are discarded.
+
+    If the file name does not exist, other file names are tried
+    in the following order:
+
+    \list 1
+    \o File name without \a suffix appended.
+    \o File name with locale part after a "_" character stripped and \a suffix.
+    \o File name with locale part stripped without \a suffix appended.
+    \o File name with locale part stripped further, etc.
+    \endlist
+
+    For example, an application running in the locale with the following
+    l{QLocale::uiLanguages()}{ui languages} - "es", "fr-CA", "de" might call
+    load(QLocale::system(), "foo", ".", "/opt/foolib", ".qm"). load() would
+    then try to open the first existing readable file from this list:
+
+    \list 1
+    \o \c /opt/foolib/foo.es.qm
+    \o \c /opt/foolib/foo.es
+    \o \c /opt/foolib/foo.fr_CA.qm
+    \o \c /opt/foolib/foo.fr_CA
+    \o \c /opt/foolib/foo.de.qm
+    \o \c /opt/foolib/foo.de
+    \o \c /opt/foolib/foo.fr.qm
+    \o \c /opt/foolib/foo.fr
+    \o \c /opt/foolib/foo.qm
+    \o \c /opt/foolib/foo.
+    \o \c /opt/foolib/foo
+    \endlist
+
+    For OSs where file system is case sensitive, QTranslator also tries to load
+    a lower-cased version of the locale name.
+*/
+bool QTranslator::load(const QLocale & locale,
+                       const QString & filename,
+                       const QString & prefix,
+                       const QString & directory,
+                       const QString & suffix)
+{
+    Q_D(QTranslator);
+    d->clear();
+    QString fname = find_translation(locale, filename, prefix, directory, suffix);
+    return !fname.isEmpty() && d->do_load(fname);
+}
+
 /*!
   \overload load()
   \fn bool QTranslator::load(const uchar *data, int len)
diff --git a/src/corelib/kernel/qtranslator.h b/src/corelib/kernel/qtranslator.h
index 33e7f03..7a4fa00 100644
--- a/src/corelib/kernel/qtranslator.h
+++ b/src/corelib/kernel/qtranslator.h
@@ -53,6 +53,7 @@ QT_MODULE(Core)
 
 #ifndef QT_NO_TRANSLATION
 
+class QLocale;
 class QTranslatorPrivate;
 
 class Q_CORE_EXPORT QTranslator : public QObject
@@ -77,6 +78,11 @@ public:
               const QString & directory = QString(),
               const QString & search_delimiters = QString(),
               const QString & suffix = QString());
+    bool load(const QLocale & locale,
+              const QString & filename,
+              const QString & prefix = QString(),
+              const QString & directory = QString(),
+              const QString & suffix = QString());
     bool load(const uchar *data, int len);
 
 #ifdef QT3_SUPPORT