From e541a3f099798e2258116d3c031b35274d789783 Mon Sep 17 00:00:00 2001
From: Kai Koehne <kai.koehne@qt.io>
Date: Thu, 30 Jan 2020 11:08:50 +0100
Subject: QTranslator: Expose language of translation file

This allows for instance to show the current UI language in the UI,
or to load additional translations that match the .qm file by other
means.

This is especially useful in the case of QTranslator::load(QLocale(),
...), in which case different language and country combinations might
be tried.

Another option is to inspect the file name via QTranslator::filePath();
however, this is more error-prone, and might also miss information
(if the .qm file name doesn't have a country suffix, or no suffix at
all).

Change-Id: I6f565d53d8f50e21241ccae6c4de264747ac8f81
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
---
 src/corelib/kernel/qtranslator.cpp                   |  19 +++++++++++++++++--
 src/corelib/kernel/qtranslator.h                     |   1 +
 tests/auto/corelib/kernel/qtranslator/hellotr_la.qm  | Bin 230 -> 237 bytes
 .../corelib/kernel/qtranslator/tst_qtranslator.cpp   |   9 +++++++--
 4 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/corelib/kernel/qtranslator.cpp b/src/corelib/kernel/qtranslator.cpp
index 822f96c499..2205366696 100644
--- a/src/corelib/kernel/qtranslator.cpp
+++ b/src/corelib/kernel/qtranslator.cpp
@@ -283,7 +283,7 @@ class QTranslatorPrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QTranslator)
 public:
-    enum { Contexts = 0x2f, Hashes = 0x42, Messages = 0x69, NumerusRules = 0x88, Dependencies = 0x96 };
+    enum { Contexts = 0x2f, Hashes = 0x42, Messages = 0x69, NumerusRules = 0x88, Dependencies = 0x96, Language = 0xa7 };
 
     QTranslatorPrivate() :
 #if defined(QT_USE_MMAP)
@@ -316,6 +316,7 @@ public:
     uint contextLength;
     uint numerusRulesLength;
 
+    QString language;
     QString filePath;
 
     bool do_load(const QString &filename, const QString &directory);
@@ -833,7 +834,9 @@ bool QTranslatorPrivate::do_load(const uchar *data, qsizetype len, const QString
             break;
         }
 
-        if (tag == QTranslatorPrivate::Contexts) {
+        if (tag == QTranslatorPrivate::Language) {
+            language = QString::fromUtf8((const char*)data, blockLen);
+        } else if (tag == QTranslatorPrivate::Contexts) {
             contextArray = data;
             contextLength = blockLen;
         } else if (tag == QTranslatorPrivate::Hashes) {
@@ -1095,6 +1098,7 @@ void QTranslatorPrivate::clear()
     qDeleteAll(subTranslators);
     subTranslators.clear();
 
+    language.clear();
     filePath.clear();
 
     if (QCoreApplicationPrivate::isTranslatorInstalled(q))
@@ -1138,6 +1142,17 @@ bool QTranslator::isEmpty() const
             && d->subTranslators.isEmpty();
 }
 
+/*!
+    \since 5.15
+
+    Returns the target language as stored in the translation file.
+ */
+QString QTranslator::language() const
+{
+    Q_D(const QTranslator);
+    return d->language;
+}
+
 /*!
     \since 5.15
 
diff --git a/src/corelib/kernel/qtranslator.h b/src/corelib/kernel/qtranslator.h
index 0c6efbbc7f..61a39c4089 100644
--- a/src/corelib/kernel/qtranslator.h
+++ b/src/corelib/kernel/qtranslator.h
@@ -63,6 +63,7 @@ public:
 
     virtual bool isEmpty() const;
 
+    QString language() const;
     QString filePath() const;
 
     bool load(const QString & filename,
diff --git a/tests/auto/corelib/kernel/qtranslator/hellotr_la.qm b/tests/auto/corelib/kernel/qtranslator/hellotr_la.qm
index cc42afe05c..25c0aad583 100644
Binary files a/tests/auto/corelib/kernel/qtranslator/hellotr_la.qm and b/tests/auto/corelib/kernel/qtranslator/hellotr_la.qm differ
diff --git a/tests/auto/corelib/kernel/qtranslator/tst_qtranslator.cpp b/tests/auto/corelib/kernel/qtranslator/tst_qtranslator.cpp
index cc0f97139f..9fde7da816 100644
--- a/tests/auto/corelib/kernel/qtranslator/tst_qtranslator.cpp
+++ b/tests/auto/corelib/kernel/qtranslator/tst_qtranslator.cpp
@@ -110,9 +110,10 @@ void tst_QTranslator::load_data()
     QTest::addColumn<QString>("filepath");
     QTest::addColumn<bool>("isEmpty");
     QTest::addColumn<QString>("translation");
+    QTest::addColumn<QString>("language");
 
-    QTest::newRow("hellotr_la") << "hellotr_la.qm" << false << "Hallo Welt!";
-    QTest::newRow("hellotr_empty") << "hellotr_empty.qm" << true << "";
+    QTest::newRow("hellotr_la") << "hellotr_la.qm" << false << "Hallo Welt!" << "de";
+    QTest::newRow("hellotr_empty") << "hellotr_empty.qm" << true << "" << "";
 }
 
 void tst_QTranslator::load()
@@ -120,6 +121,7 @@ void tst_QTranslator::load()
     QFETCH(QString, filepath);
     QFETCH(bool, isEmpty);
     QFETCH(QString, translation);
+    QFETCH(QString, language);
 
     {
         QTranslator tor;
@@ -127,6 +129,7 @@ void tst_QTranslator::load()
         QCOMPARE(tor.isEmpty(), isEmpty);
         QCOMPARE(tor.translate("QPushButton", "Hello world!"), translation);
         QCOMPARE(tor.filePath(), filepath);
+        QCOMPARE(tor.language(), language);
     }
 
     {
@@ -138,6 +141,7 @@ void tst_QTranslator::load()
         QCOMPARE(tor.isEmpty(), isEmpty);
         QCOMPARE(tor.translate("QPushButton", "Hello world!"), translation);
         QCOMPARE(tor.filePath(), "");
+        QCOMPARE(tor.language(), language);
     }
 
     {
@@ -147,6 +151,7 @@ void tst_QTranslator::load()
         QCOMPARE(tor.isEmpty(), isEmpty);
         QCOMPARE(tor.translate("QPushButton", "Hello world!"), translation);
         QCOMPARE(tor.filePath(), path);
+        QCOMPARE(tor.language(), language);
     }
 }
 
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