Fix string cast

Enforce proper string cast using QT_NO_CAST_TO_ASCII and friends.

Change-Id: I039b23144c8d57f12aad1c27f29654b382078222
Reviewed-by: Jarkko Koivikko <jarkko.koivikko@code-q.fi>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

39 files changed, 239 insertions, 115 deletions

diff --git a/src/plugin/plugin.cpp b/src/plugin/plugin.cpp
index fb54ce65..e1e03df7 100644
--- a/src/plugin/plugin.cpp
+++ b/src/plugin/plugin.cpp
@@ -84,10 +84,10 @@ QPlatformInputContext *QVirtualKeyboardPlugin::create(const QString &system, con
             qCWarning(qlcVirtualKeyboard) << "Error loading extension - metadata not found!";
             continue;
         }
-        const QString inputMethod = metaData.value("InputMethod").toString();
+        const QString inputMethod = metaData.value(QLatin1String("InputMethod")).toString();
         if (!inputMethod.isEmpty() && inputMethodList.contains(inputMethod)) {
             qCWarning(qlcVirtualKeyboard) << "Ignored extension" << extensionName <<
-                                             "by" << metaData.value("Provider").toString() <<
+                                             "by" << metaData.value(QLatin1String("Provider")).toString() <<
                                              "-" << inputMethod << "is already registered!";
             continue;
         }
diff --git a/src/plugin/plugin.pro b/src/plugin/plugin.pro
index 2256b677..8cf53c9a 100644
--- a/src/plugin/plugin.pro
+++ b/src/plugin/plugin.pro
@@ -12,6 +12,12 @@ HEADERS += \
 OTHER_FILES += \
     qtvirtualkeyboard.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 win32 {
     QMAKE_TARGET_PRODUCT = "Qt Virtual Keyboard (Qt $$QT_VERSION)"
     QMAKE_TARGET_DESCRIPTION = "Virtual Keyboard for Qt."
diff --git a/src/plugins/hangul/hangul.pro b/src/plugins/hangul/hangul.pro
index 5106ce34..5ce08a65 100644
--- a/src/plugins/hangul/hangul.pro
+++ b/src/plugins/hangul/hangul.pro
@@ -12,6 +12,12 @@ SOURCES += \
 OTHER_FILES += \
     hangul.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../config.pri)
 
 LAYOUT_FILES += \
diff --git a/src/plugins/hunspell/hunspellinputmethod/hunspellinputmethod.pro b/src/plugins/hunspell/hunspellinputmethod/hunspellinputmethod.pro
index d2a47e0c..9dc2e654 100644
--- a/src/plugins/hunspell/hunspellinputmethod/hunspellinputmethod.pro
+++ b/src/plugins/hunspell/hunspellinputmethod/hunspellinputmethod.pro
@@ -16,6 +16,12 @@ HEADERS += \
     hunspellworker_p.h \
     qhunspellinputmethod_global.h
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 
 hunspell-library: QMAKE_USE += hunspell
diff --git a/src/plugins/hunspell/hunspellinputmethod/hunspellworker.cpp b/src/plugins/hunspell/hunspellinputmethod/hunspellworker.cpp
index 6387ee16..15af0841 100644
--- a/src/plugins/hunspell/hunspellinputmethod/hunspellworker.cpp
+++ b/src/plugins/hunspell/hunspellinputmethod/hunspellworker.cpp
@@ -763,7 +763,7 @@ void HunspellWorker::run()
                 continue;
             perf.start();
             currentTask->run();
-            qCDebug(lcHunspell) << QString(QLatin1String(currentTask->metaObject()->className()) + "::run(): time:").toLatin1().constData() << perf.elapsed() << "ms";
+            qCDebug(lcHunspell) << QString(QLatin1String(currentTask->metaObject()->className()) + QLatin1String("::run(): time:")).toLatin1().constData() << perf.elapsed() << "ms";
         }
     }
     if (hunspell) {
diff --git a/src/plugins/hunspell/plugin/plugin.pro b/src/plugins/hunspell/plugin/plugin.pro
index 99eab6c9..1981b5e5 100644
--- a/src/plugins/hunspell/plugin/plugin.pro
+++ b/src/plugins/hunspell/plugin/plugin.pro
@@ -8,6 +8,12 @@ SOURCES += \
 OTHER_FILES += \
     hunspell.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 
 hunspell-library {
diff --git a/src/plugins/lipi-toolkit/plugin/lipiinputmethod.cpp b/src/plugins/lipi-toolkit/plugin/lipiinputmethod.cpp
index 00e82541..ca23c491 100644
--- a/src/plugins/lipi-toolkit/plugin/lipiinputmethod.cpp
+++ b/src/plugins/lipi-toolkit/plugin/lipiinputmethod.cpp
@@ -117,19 +117,19 @@ public:
         if (context == currentContext)
             return;
 
-        qCDebug(lcLipi) << "LipiInputMethodPrivate::setContext():" << QString(context.toHex());
+        qCDebug(lcLipi) << "LipiInputMethodPrivate::setContext():" << QLatin1String(context.toHex());
 
         clearTraces();
 
         deviceInfo.reset(new LTKCaptureDevice());
-        deviceInfo->setSamplingRate(traceCaptureDeviceInfo.value("sampleRate", 60).toInt());
-        deviceInfo->setXDPI(traceCaptureDeviceInfo.value("dpi", 96).toInt());
+        deviceInfo->setSamplingRate(traceCaptureDeviceInfo.value(QLatin1String("sampleRate"), 60).toInt());
+        deviceInfo->setXDPI(traceCaptureDeviceInfo.value(QLatin1String("dpi"), 96).toInt());
         deviceInfo->setYDPI(deviceInfo->getXDPI());
-        deviceInfo->setLatency(traceCaptureDeviceInfo.value("latency", 0.0).toFloat());
-        deviceInfo->setUniformSampling(traceCaptureDeviceInfo.value("uniform", false).toBool());
+        deviceInfo->setLatency(traceCaptureDeviceInfo.value(QLatin1String("latency"), 0.0).toFloat());
+        deviceInfo->setUniformSampling(traceCaptureDeviceInfo.value(QLatin1String("uniform"), false).toBool());
 
         screenContext.reset(new LTKScreenContext());
-        QRectF boundingBox(traceScreenInfo.value("boundingBox").toRectF());
+        QRectF boundingBox(traceScreenInfo.value(QLatin1String("boundingBox")).toRectF());
         if (!boundingBox.isEmpty()) {
             screenContext->setBboxLeft(boundingBox.left());
             screenContext->setBboxTop(boundingBox.top());
@@ -137,7 +137,7 @@ public:
             screenContext->setBboxBottom(boundingBox.bottom());
         }
 
-        QVariantList horizontalRulers(traceScreenInfo.value("horizontalRulers", QVariantList()).toList());
+        QVariantList horizontalRulers(traceScreenInfo.value(QLatin1String("horizontalRulers"), QVariantList()).toList());
         if (!horizontalRulers.isEmpty()) {
             for (QVariantList::ConstIterator i = horizontalRulers.constBegin();
                  i != horizontalRulers.constEnd(); i++) {
@@ -145,7 +145,7 @@ public:
             }
         }
 
-        QVariantList verticalRulers(traceScreenInfo.value("verticalRulers", QVariantList()).toList());
+        QVariantList verticalRulers(traceScreenInfo.value(QLatin1String("verticalRulers"), QVariantList()).toList());
         if (!horizontalRulers.isEmpty()) {
             for (QVariantList::ConstIterator i = verticalRulers.constBegin();
                  i != verticalRulers.constEnd(); i++) {
@@ -182,7 +182,7 @@ public:
 #endif
 
         QVirtualKeyboardTrace *trace = new QVirtualKeyboardTrace();
-        trace->setChannels(QStringList("t"));
+        trace->setChannels(QStringList(QLatin1String("t")));
         traceList.append(trace);
 
         return trace;
@@ -271,7 +271,7 @@ public:
                         saveTraces(Qt::Key_Space, 100);
 #endif
                         cancelRecognition();
-                        ic->inputEngine()->virtualKeyClick(Qt::Key_Space, QString(" "), Qt::NoModifier);
+                        ic->inputEngine()->virtualKeyClick(Qt::Key_Space, QLatin1String(" "), Qt::NoModifier);
                     } else if (swipeTouchCount == 2) {
                         // Double swipe: commit word, or insert space
                         cancelRecognition();
@@ -282,7 +282,7 @@ public:
                             return;
                         }
 #endif
-                        ic->inputEngine()->virtualKeyClick(Qt::Key_Space, QString(" "), Qt::NoModifier);
+                        ic->inputEngine()->virtualKeyClick(Qt::Key_Space, QLatin1String(" "), Qt::NoModifier);
                     }
                     return;
                 }
@@ -325,14 +325,14 @@ public:
         vector<LTKChannel> channels;
         channels.push_back(LTKChannel("X", DT_INT, true));
         channels.push_back(LTKChannel("Y", DT_INT, true));
-        bool hasTime = trace->channels().contains("t");
+        bool hasTime = trace->channels().contains(QLatin1String("t"));
         if (hasTime)
             channels.push_back(LTKChannel("T", DT_FLOAT, true));
         LTKTraceFormat traceFormat(channels);
         LTKTrace ltktrace(traceFormat);
 
         const QVariantList points = trace->points();
-        const QVariantList timeData = hasTime ? trace->channelData("t") : QVariantList();
+        const QVariantList timeData = hasTime ? trace->channelData(QLatin1String("t")) : QVariantList();
         QVariantList::ConstIterator t = timeData.constBegin();
         for (const QVariant &p : points) {
             const QPointF pt(p.toPointF());
@@ -355,7 +355,7 @@ public:
 #endif
         stopRecognizeTimer();
         clearTraces();
-        if (recognitionTask && !delayedResult.isEmpty() && recognitionTask->resultId() == delayedResult["resultId"].toInt())
+        if (recognitionTask && !delayedResult.isEmpty() && recognitionTask->resultId() == delayedResult[QLatin1String("resultId")].toInt())
             processResult(delayedResult);
         delayedResult.clear();
         recognitionTask.reset();
@@ -408,7 +408,7 @@ public:
     {
         if (!resultList.isEmpty()) {
             const QVariantMap result = resultList.at(0).toMap();
-            if (recognitionTask && recognitionTask->resultId() == result["resultId"].toInt())
+            if (recognitionTask && recognitionTask->resultId() == result[QLatin1String("resultId")].toInt())
                 delayedResult = result;
             else
                 processResult(result);
@@ -417,13 +417,13 @@ public:
 
     void processResult(const QVariantMap &result)
     {
-        const QChar ch = result["unicode"].toChar();
+        const QChar ch = result[QLatin1String("unicode")].toChar();
         const QChar chUpper = ch.toUpper();
 #ifdef QT_VIRTUALKEYBOARD_RECORD_TRACE_INPUT
         // In recording mode, the text case must match with the current text case
         if (unipenTrace) {
             if (!ch.isLetter() || (ch.isUpper() == (textCase == QVirtualKeyboardInputEngine::TextCase::Upper)))
-                saveTraces(ch.unicode(), qRound(result["confidence"].toDouble() * 100));
+                saveTraces(ch.unicode(), qRound(result[QLatin1String("confidence")].toDouble() * 100));
             delete unipenTrace;
             unipenTrace = 0;
         }
@@ -448,7 +448,7 @@ public:
 
         QStringList homeLocations = QStandardPaths::standardLocations(QStandardPaths::HomeLocation);
         if (!homeLocations.isEmpty()) {
-            QString filePath = QStringLiteral("%1/%2").arg(homeLocations.at(0)).arg("VIRTUAL_KEYBOARD_TRACES");
+            QString filePath = QStringLiteral("%1/%2").arg(homeLocations.at(0)).arg(QLatin1String("VIRTUAL_KEYBOARD_TRACES"));
             unipenTrace->setDirectory(filePath);
             unipenTrace->save(unicode, confidence);
         }
@@ -625,7 +625,10 @@ void LipiInputMethod::resultsAvailable(const QVariantList &resultList)
         qCDebug(lcLipi) << "LipiInputMethod::resultsAvailable():";
         for (int i = 0; i < resultList.size(); i++) {
             QVariantMap result = resultList.at(i).toMap();
-            qCDebug(lcLipi) << QString("%1: %2 (%3)").arg(i + 1).arg(result["unicode"].toChar()).arg(result["confidence"].toFloat()).toUtf8().constData();
+            const QChar unicode = result[QLatin1String("unicode")].toChar();
+            const double confidence = result[QLatin1String("confidence")].toDouble();
+            qCDebug(lcLipi) << QStringLiteral("%1: %2 (%3)").arg(i + 1)
+                               .arg(unicode).arg(confidence).toUtf8().constData();
         }
     }
     Q_D(LipiInputMethod);
diff --git a/src/plugins/lipi-toolkit/plugin/lipisharedrecognizer.cpp b/src/plugins/lipi-toolkit/plugin/lipisharedrecognizer.cpp
index 8a45dcb6..090f129c 100644
--- a/src/plugins/lipi-toolkit/plugin/lipisharedrecognizer.cpp
+++ b/src/plugins/lipi-toolkit/plugin/lipisharedrecognizer.cpp
@@ -90,7 +90,7 @@ bool LipiSharedRecognizer::setModel(const QString &modelName)
     qCDebug(lcLipi) << "LipiSharedRecognizer::setModel():" << modelName;
 
     if (!s_lipiEngine) {
-        qWarning() << "Engine not initialized";
+        qCWarning(lcLipi) << "Engine not initialized";
         return false;
     }
 
@@ -187,16 +187,16 @@ int LipiSharedRecognizer::loadLipiInterface()
             */
             bool lipiRootVarIsEmpty = qEnvironmentVariableIsEmpty("LIPI_ROOT");
             s_lipiRoot = lipiRootVarIsEmpty ?
-                        QDir(QLibraryInfo::location(QLibraryInfo::DataPath) + "/qtvirtualkeyboard/lipi_toolkit").absolutePath() :
+                        QDir(QLibraryInfo::location(QLibraryInfo::DataPath) + QLatin1String("/qtvirtualkeyboard/lipi_toolkit")).absolutePath() :
                         qEnvironmentVariable("LIPI_ROOT");
 
             bool lipiLibVarIsEmpty = qEnvironmentVariableIsEmpty("LIPI_LIB");
             if (!lipiLibVarIsEmpty)
                 s_lipiLib = qEnvironmentVariable("LIPI_LIB");
             else if (!lipiRootVarIsEmpty)
-                s_lipiLib = s_lipiRoot + "/lib";
+                s_lipiLib = s_lipiRoot + QLatin1String("/lib");
             else
-                s_lipiLib = QDir(QLibraryInfo::location(QLibraryInfo::PluginsPath) + "/lipi_toolkit").absolutePath();
+                s_lipiLib = QDir(QLibraryInfo::location(QLibraryInfo::PluginsPath) + QLatin1String("/lipi_toolkit")).absolutePath();
         }
 
         QScopedPointer<LTKOSUtil> osUtil(LTKOSUtilFactory::getInstance());
@@ -205,7 +205,7 @@ int LipiSharedRecognizer::loadLipiInterface()
 
         int result = osUtil->loadSharedLib(lipiLibPath, LIPIENGINE_MODULE_STR, &s_lipiEngineHandle);
         if (result != SUCCESS) {
-            qWarning() << QString("Error %1: Could not open shared library for module '%2'").arg(result).arg(LIPIENGINE_MODULE_STR);
+            qCWarning(lcLipi) << QStringLiteral("Error %1: Could not open shared library for module '%2'").arg(result).arg(QLatin1String(LIPIENGINE_MODULE_STR));
             return result;
         }
 
@@ -215,13 +215,13 @@ int LipiSharedRecognizer::loadLipiInterface()
 
         result = osUtil->getFunctionAddress(s_lipiEngineHandle, "createLTKLipiEngine", (void **)&s_createLTKLipiEngine);
         if (result != SUCCESS) {
-            qWarning() << QString("Error %1: %2").arg(result).arg(getErrorMessage(result).c_str());
+            qCWarning(lcLipi) << QStringLiteral("Error %1: %2").arg(result).arg(QLatin1String(getErrorMessage(result).c_str()));
             return result;
         }
 
         result = osUtil->getFunctionAddress(s_lipiEngineHandle, "deleteLTKLipiEngine", (void **)&s_deleteLTKLipiEngine);
         if (result != SUCCESS) {
-            qWarning() << QString("Error %1: %2").arg(result).arg(getErrorMessage(result).c_str());
+            qCWarning(lcLipi) << QStringLiteral("Error %1: %2").arg(result).arg(QLatin1String(getErrorMessage(result).c_str()));
             return result;
         }
 
@@ -235,7 +235,7 @@ int LipiSharedRecognizer::loadLipiInterface()
 
         result = s_lipiEngine->initializeLipiEngine();
         if (result != SUCCESS) {
-            qWarning() << QString("Error %1: %2").arg(result).arg(getErrorMessage(result).c_str());
+            qCWarning(lcLipi) << QStringLiteral("Error %1: %2").arg(result).arg(QLatin1String(getErrorMessage(result).c_str()));
             return result;
         }
     }
@@ -266,9 +266,9 @@ int LipiSharedRecognizer::loadLipiEngineConfig()
 {
     s_lipiEngineConfigEntries.clear();
 
-    const QString &lipiEngineConfigFile(QDir::toNativeSeparators(QString("%1/projects/lipiengine.cfg").arg(s_lipiRoot)));
+    const QString &lipiEngineConfigFile(QDir::toNativeSeparators(QStringLiteral("%1/projects/lipiengine.cfg").arg(s_lipiRoot)));
     if (!QFileInfo::exists(lipiEngineConfigFile)) {
-        qWarning() << "File not found" << lipiEngineConfigFile;
+        qCWarning(lcLipi) << "File not found" << lipiEngineConfigFile;
         return FAILURE;
     }
 
@@ -291,11 +291,11 @@ int LipiSharedRecognizer::resolveLogicalNameToProjectProfile(const QString &logi
     if (configEntry == s_lipiEngineConfigEntries.end())
         return FAILURE;
 
-    QStringList parts = QString(configEntry->second.c_str()).split('(', QString::SkipEmptyParts);
+    QStringList parts = QString::fromLatin1(configEntry->second.c_str()).split(QLatin1Char('('), QString::SkipEmptyParts);
     if (parts.length() != 2)
         return FAILURE;
 
-    parts[1].replace(')', "");
+    parts[1].replace(QLatin1Char(')'), QString());
 
     outProjectName = parts[0].trimmed();
     outProfileName = parts[1].trimmed();
@@ -323,7 +323,7 @@ int LipiSharedRecognizer::loadModelData(const QString &logicalName)
         string strProfile = profile.toStdString();
         int result = s_lipiEngine->createShapeRecognizer(strProject, strProfile, &s_shapeRecognizer);
         if (result == SUCCESS) {
-            result = loadMapping(QDir::toNativeSeparators(QString("%1/projects/%2/config/unicodeMapfile_%2.ini").arg(s_lipiRoot).arg(project)));
+            result = loadMapping(QDir::toNativeSeparators(QStringLiteral("%1/projects/%2/config/unicodeMapfile_%2.ini").arg(s_lipiRoot).arg(project)));
             if (result == SUCCESS) {
                 s_lipiWorker = new LipiWorker(s_shapeRecognizer);
                 QSharedPointer<LipiLoadModelDataTask> loadModelDataTask(new LipiLoadModelDataTask());
@@ -337,7 +337,7 @@ int LipiSharedRecognizer::loadModelData(const QString &logicalName)
         qCDebug(lcLipi) << "LipiSharedRecognizer::loadModelData(): time:" << perf.elapsed() << "ms";
 
     if (result != SUCCESS) {
-        qWarning() << QString("Error %1: %2").arg(result).arg(getErrorMessage(result).c_str());
+        qCWarning(lcLipi) << QStringLiteral("Error %1: %2").arg(result).arg(QLatin1String(getErrorMessage(result).c_str()));
         unloadModelData();
     }
 
@@ -370,7 +370,7 @@ void LipiSharedRecognizer::unloadModelData()
 int LipiSharedRecognizer::loadMapping(const QString &mapFile)
 {
     if (!QFileInfo(mapFile).exists()) {
-        qWarning() << "File not found" << mapFile;
+        qCWarning(lcLipi) << "File not found" << mapFile;
         return FAILURE;
     }
 
@@ -381,15 +381,15 @@ int LipiSharedRecognizer::loadMapping(const QString &mapFile)
         for (stringStringMap::const_iterator i = cfgFileMap.begin(); i != cfgFileMap.end(); i++) {
             if (i->first.empty())
                 continue;
-            if (!QChar(i->first.at(0)).isDigit())
+            if (!QChar::fromLatin1(i->first.at(0)).isDigit())
                 continue;
 
             bool ok;
-            int id = QString(i->first.c_str()).toInt(&ok, 10);
+            int id = QString::fromLatin1(i->first.c_str()).toInt(&ok, 10);
             if (!ok)
                 continue;
 
-            QChar ch = QChar(QString(i->second.c_str()).toInt(&ok, 16));
+            QChar ch = QChar(QString::fromLatin1(i->second.c_str()).toInt(&ok, 16));
             if (!ok)
                 continue;
 
diff --git a/src/plugins/lipi-toolkit/plugin/lipiworker.cpp b/src/plugins/lipi-toolkit/plugin/lipiworker.cpp
index b1e8320d..ffe5c3b7 100644
--- a/src/plugins/lipi-toolkit/plugin/lipiworker.cpp
+++ b/src/plugins/lipi-toolkit/plugin/lipiworker.cpp
@@ -58,7 +58,7 @@ void LipiLoadModelDataTask::run()
     int result = shapeRecognizer->loadModelData();
     qCDebug(lcLipi) << "LipiLoadModelDataTask::run(): time:" << perf.elapsed() << "ms";
     if (result != SUCCESS)
-        qWarning() << QString("Error %1: %2").arg(result).arg(getErrorMessage(result).c_str());
+        qCWarning(lcLipi) << QStringLiteral("Error %1: %2").arg(result).arg(QLatin1String(getErrorMessage(result).c_str()));
 }
 
 /*!
@@ -159,10 +159,10 @@ void LipiRecognitionResultsTask::run()
          i != resultVector->end(); i++) {
         QVariantMap result;
         int shapeId = i->getShapeId();
-        result["resultId"] = _resultId;
-        result["shapeId"] = shapeId;
-        result["unicode"] = unicodeMap.value(shapeId);
-        result["confidence"] = i->getConfidence();
+        result[QLatin1String("resultId")] = _resultId;
+        result[QLatin1String("shapeId")] = shapeId;
+        result[QLatin1String("unicode")] = unicodeMap.value(shapeId);
+        result[QLatin1String("confidence")] = i->getConfidence();
         resultList.append(result);
     }
 
diff --git a/src/plugins/lipi-toolkit/plugin/plugin.pro b/src/plugins/lipi-toolkit/plugin/plugin.pro
index 427d2aa8..c3a12440 100644
--- a/src/plugins/lipi-toolkit/plugin/plugin.pro
+++ b/src/plugins/lipi-toolkit/plugin/plugin.pro
@@ -15,6 +15,12 @@ SOURCES += \
 OTHER_FILES += \
     lipi.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 
 INCLUDEPATH += \
diff --git a/src/plugins/openwnn/3rdparty/openwnn/openwnn.pro b/src/plugins/openwnn/3rdparty/openwnn/openwnn.pro
index 6c75d8ee..150ed169 100644
--- a/src/plugins/openwnn/3rdparty/openwnn/openwnn.pro
+++ b/src/plugins/openwnn/3rdparty/openwnn/openwnn.pro
@@ -51,6 +51,12 @@ HEADERS += \
     wnnEngine/include/romkanhalfkatakana.h \
     wnnEngine/include/wnnlookuptable.h
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 load(qt_helper_lib)
 
 CONFIG += qt
diff --git a/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/composingtext.cpp b/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/composingtext.cpp
index 82022c8e..1f9ca4ff 100644
--- a/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/composingtext.cpp
+++ b/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/composingtext.cpp
@@ -210,7 +210,7 @@ void ComposingText::debugout() const
         QString tmp;
         for (QList<StrSegment>::ConstIterator it = d->mStringLayer[i].constBegin();
              it != d->mStringLayer[i].constEnd(); it++) {
-            tmp += QString("(%1,%2,%3)").arg(it->string).arg(it->from).arg(it->to);
+            tmp += QStringLiteral("(%1,%2,%3)").arg(it->string).arg(it->from).arg(it->to);
         }
     }
 }
diff --git a/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/openwnnenginejajp.cpp b/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/openwnnenginejajp.cpp
index dbcb7c37..534e97b6 100644
--- a/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/openwnnenginejajp.cpp
+++ b/src/plugins/openwnn/3rdparty/openwnn/wnnEngine/openwnnenginejajp.cpp
@@ -178,8 +178,8 @@ public:
         }
 
         if (input.length() == 0) {
-            mInputHiragana = "";
-            mInputRomaji = "";
+            mInputHiragana.clear();
+            mInputRomaji.clear();
             return 0;
         }
 
diff --git a/src/plugins/openwnn/plugin/openwnninputmethod.cpp b/src/plugins/openwnn/plugin/openwnninputmethod.cpp
index 4d47a0a5..d6206732 100644
--- a/src/plugins/openwnn/plugin/openwnninputmethod.cpp
+++ b/src/plugins/openwnn/plugin/openwnninputmethod.cpp
@@ -184,7 +184,7 @@ public:
     {
         if (composingText.size(ComposingText::LAYER0) != 0) {
             Q_Q(OpenWnnInputMethod);
-            q->inputContext()->commit("");
+            q->inputContext()->commit(QString());
         }
         composingText.clear();
         exactMatchMode = false;
diff --git a/src/plugins/openwnn/plugin/plugin.pro b/src/plugins/openwnn/plugin/plugin.pro
index 76234f89..7e11d890 100644
--- a/src/plugins/openwnn/plugin/plugin.pro
+++ b/src/plugins/openwnn/plugin/plugin.pro
@@ -10,6 +10,12 @@ SOURCES += \
 OTHER_FILES += \
     openwnn.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 
 LAYOUT_FILES += \
diff --git a/src/plugins/pinyin/3rdparty/pinyin/patches/0005-Fix-string-cast.patch b/src/plugins/pinyin/3rdparty/pinyin/patches/0005-Fix-string-cast.patch
new file mode 100644
index 00000000..63e126d1
--- /dev/null
+++ b/src/plugins/pinyin/3rdparty/pinyin/patches/0005-Fix-string-cast.patch
@@ -0,0 +1,28 @@
+From 821c869ad7af125a7a718093f8d4730108cffe5b Mon Sep 17 00:00:00 2001
+From: Jarkko Koivikko <jarkko.koivikko@code-q.fi>
+Date: Thu, 23 Aug 2018 21:51:19 +0300
+Subject: [PATCH] Fix string cast
+
+Enforce proper string cast using QT_NO_CAST_TO_ASCII and friends.
+
+Change-Id: I039b23144c8d57f12aad1c27f29654b382078222
+---
+ src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp b/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp
+index e7d194f..a084395 100644
+--- a/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp
++++ b/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp
+@@ -245,7 +245,7 @@ bool DictTrie::load_dict(const char *filename, LemmaIdType start_id,
+   if (NULL == filename || end_id <= start_id)
+     return false;
+ 
+-  QFile file(filename);
++  QFile file(QString::fromUtf8(filename));
+   if (!file.open(QIODevice::ReadOnly))
+     return false;
+   QFile *fp = &file;
+-- 
+2.14.1.windows.1
+
diff --git a/src/plugins/pinyin/3rdparty/pinyin/pinyin.pro b/src/plugins/pinyin/3rdparty/pinyin/pinyin.pro
index 0aedbb31..193f571a 100644
--- a/src/plugins/pinyin/3rdparty/pinyin/pinyin.pro
+++ b/src/plugins/pinyin/3rdparty/pinyin/pinyin.pro
@@ -45,6 +45,12 @@ HEADERS += \
     include/utf16char.h \
     include/utf16reader.h
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 OTHER_FILES +=\
     data/rawdict_utf16_65105_freq.txt \
     data/valid_utf16.txt
diff --git a/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp b/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp
index e7d194f6..a084395e 100644
--- a/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp
+++ b/src/plugins/pinyin/3rdparty/pinyin/share/dicttrie.cpp
@@ -245,7 +245,7 @@ bool DictTrie::load_dict(const char *filename, LemmaIdType start_id,
   if (NULL == filename || end_id <= start_id)
     return false;
 
-  QFile file(filename);
+  QFile file(QString::fromUtf8(filename));
   if (!file.open(QIODevice::ReadOnly))
     return false;
   QFile *fp = &file;
diff --git a/src/plugins/pinyin/3rdparty/pinyin/update-patches.sh b/src/plugins/pinyin/3rdparty/pinyin/update-patches.sh
index 98d7af6e..ed67686a 100644
--- a/src/plugins/pinyin/3rdparty/pinyin/update-patches.sh
+++ b/src/plugins/pinyin/3rdparty/pinyin/update-patches.sh
@@ -29,8 +29,8 @@
 #############################################################################
 
 REV_FILTER=". :!./patches :!./update-patches.sh :!./pinyin.pro :!./qt_attribution.json"
-REV_LIST=$(git rev-list --reverse HEAD -- $REV_FILTER)
-N=0
+REV_LIST=$(git rev-list --reverse 59208edaaf40be982904a6c8cad4eab2d14f938e..HEAD -- $REV_FILTER)
+N=5
 
 for REV in $REV_LIST; do
     if [ $N -gt 0 ]; then
diff --git a/src/plugins/pinyin/plugin/pinyindecoderservice.cpp b/src/plugins/pinyin/plugin/pinyindecoderservice.cpp
index e01f7e63..4d9890f4 100644
--- a/src/plugins/pinyin/plugin/pinyindecoderservice.cpp
+++ b/src/plugins/pinyin/plugin/pinyindecoderservice.cpp
@@ -82,11 +82,11 @@ bool PinyinDecoderService::init()
     if (!QFileInfo::exists(sysDict)) {
         sysDict = QLatin1String(":///QtQuick/VirtualKeyboard/3rdparty/pinyin/data/dict_pinyin.dat");
         if (!QFileInfo::exists(sysDict))
-            sysDict = QLibraryInfo::location(QLibraryInfo::DataPath) + "/qtvirtualkeyboard/pinyin/dict_pinyin.dat";
+            sysDict = QLibraryInfo::location(QLibraryInfo::DataPath) + QLatin1String("/qtvirtualkeyboard/pinyin/dict_pinyin.dat");
     }
 
     QString usrDictPath = QStandardPaths::writableLocation(QStandardPaths::ConfigLocation);
-    QFileInfo usrDictInfo(usrDictPath + "/qtvirtualkeyboard/pinyin/usr_dict.dat");
+    QFileInfo usrDictInfo(usrDictPath + QLatin1String("/qtvirtualkeyboard/pinyin/usr_dict.dat"));
     if (!usrDictInfo.exists()) {
         qCWarning(lcPinyin) << "PinyinDecoderService::init(): creating directory for user dictionary" << usrDictInfo.absolutePath();
         QDir().mkpath(usrDictInfo.absolutePath());
@@ -105,7 +105,7 @@ void PinyinDecoderService::setUserDictionary(bool enabled)
         return;
     if (enabled) {
         QString usrDictPath = QStandardPaths::writableLocation(QStandardPaths::ConfigLocation);
-        QFileInfo usrDictInfo(usrDictPath + "/qtvirtualkeyboard/pinyin/usr_dict.dat");
+        QFileInfo usrDictInfo(usrDictPath + QLatin1String("/qtvirtualkeyboard/pinyin/usr_dict.dat"));
         im_init_user_dictionary(usrDictInfo.absoluteFilePath().toUtf8().constData());
     } else {
         im_init_user_dictionary(nullptr);
diff --git a/src/plugins/pinyin/plugin/pinyininputmethod.cpp b/src/plugins/pinyin/plugin/pinyininputmethod.cpp
index 8cc13c79..35d481c8 100644
--- a/src/plugins/pinyin/plugin/pinyininputmethod.cpp
+++ b/src/plugins/pinyin/plugin/pinyininputmethod.cpp
@@ -88,7 +88,7 @@ public:
         finishSelection = true;
         composingStr.clear();
         if (inputContext)
-            inputContext->setPreeditText("");
+            inputContext->setPreeditText(QString());
         activeCmpsLen = 0;
         posDelSpl = -1;
         isPosInSpl = false;
@@ -231,7 +231,7 @@ public:
             for (int pos = fixedLen + 1; pos < splStart.size() - 1; pos++) {
                 composingStrDisplay += surface.mid(splStart[pos], splStart[pos + 1] - splStart[pos]).toUpper();
                 if (splStart[pos + 1] < surfaceDecodedLen)
-                    composingStrDisplay += " ";
+                    composingStrDisplay += QLatin1String(" ");
             }
             if (surfaceDecodedLen < surface.length())
                 composingStrDisplay += surface.mid(surfaceDecodedLen).toLower();
diff --git a/src/plugins/pinyin/plugin/plugin.pro b/src/plugins/pinyin/plugin/plugin.pro
index 980862b4..f66c887e 100644
--- a/src/plugins/pinyin/plugin/plugin.pro
+++ b/src/plugins/pinyin/plugin/plugin.pro
@@ -12,6 +12,12 @@ SOURCES += \
 OTHER_FILES += \
     pinyin.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 
 LAYOUT_FILES += \
diff --git a/src/plugins/t9write/plugin/plugin.pro b/src/plugins/t9write/plugin/plugin.pro
index 1c6393cf..0f68f8c4 100644
--- a/src/plugins/t9write/plugin/plugin.pro
+++ b/src/plugins/t9write/plugin/plugin.pro
@@ -15,6 +15,12 @@ SOURCES += \
 OTHER_FILES += \
     t9write.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 include(../3rdparty/t9write/t9write-build.pri)
 
diff --git a/src/plugins/t9write/plugin/t9writeinputmethod.cpp b/src/plugins/t9write/plugin/t9writeinputmethod.cpp
index 2ec9d073..63647e85 100644
--- a/src/plugins/t9write/plugin/t9writeinputmethod.cpp
+++ b/src/plugins/t9write/plugin/t9writeinputmethod.cpp
@@ -346,7 +346,7 @@ public:
     {
         srcType = numberOfSrcDictionaryTypes;
 
-        QStringList languageCountry = locale.name().split("_");
+        QStringList languageCountry = locale.name().split(QLatin1String("_"));
         if (languageCountry.length() != 2)
             return QString();
 
@@ -355,7 +355,7 @@ public:
         while (it.hasNext()) {
             QString fileEntry = it.next();
 
-            if (!fileEntry.contains("_" + languageCountry[0].toUpper()))
+            if (!fileEntry.contains(QLatin1String("_") + languageCountry[0].toUpper()))
                 continue;
 
             if (fileEntry.endsWith(QLatin1String(".ldb"))) {
@@ -1007,7 +1007,7 @@ public:
             return;
         currentContext = context;
 
-        qCDebug(lcT9Write) << "T9WriteInputMethodPrivate::setContext():" << QString(context.toHex());
+        qCDebug(lcT9Write) << "T9WriteInputMethodPrivate::setContext():" << QLatin1String((context.toHex()));
 
         // Finish recognition, but preserve current input
         Q_Q(T9WriteInputMethod);
@@ -1027,7 +1027,7 @@ public:
             emit q->selectionListActiveItemChanged(QVirtualKeyboardSelectionListModel::Type::WordCandidateList, activeWordIndex);
         }
 
-        const int dpi = traceCaptureDeviceInfo.value("dpi", 96).toInt();
+        const int dpi = traceCaptureDeviceInfo.value(QLatin1String("dpi"), 96).toInt();
         static const int INSTANT_GESTURE_WIDTH_THRESHOLD_MM = 25;
         static const int INSTANT_GESTURE_HEIGHT_THRESHOLD_MM = 25;
         instantGestureSettings.widthThreshold = INSTANT_GESTURE_WIDTH_THRESHOLD_MM / 25.4 * dpi;
@@ -1035,7 +1035,7 @@ public:
 
         gestureRecognizer.setDpi(dpi);
 
-        QVariantList horizontalRulers(traceScreenInfo.value("horizontalRulers", QVariantList()).toList());
+        QVariantList horizontalRulers(traceScreenInfo.value(QLatin1String("horizontalRulers"), QVariantList()).toList());
         if (horizontalRulers.count() >= 2) {
             sessionSettings.baseline = horizontalRulers.last().toInt();
             sessionSettings.helpline = 0;
@@ -1343,8 +1343,8 @@ public:
             if (resultList.isEmpty())
                 return;
 
-            if (resultList.first().toMap()["resultId"] != resultId) {
-                qCDebug(lcT9Write) << "T9WriteInputMethodPrivate::processResult(): resultId mismatch" << resultList.first().toMap()["resultId"] << "(" << resultId << ")";
+            if (resultList.first().toMap()[QLatin1String("resultId")] != resultId) {
+                qCDebug(lcT9Write) << "T9WriteInputMethodPrivate::processResult(): resultId mismatch" << resultList.first().toMap()[QLatin1String("resultId")] << "(" << resultId << ")";
                 resultList.clear();
                 return;
             }
@@ -1352,7 +1352,7 @@ public:
 
             for (int i = 0; i < resultList.size(); i++) {
                 QVariantMap result = resultList.at(i).toMap();
-                QString resultChars = result["chars"].toString();
+                QString resultChars = result[QLatin1String("chars")].toString();
                 if (i == 0) {
                     if (ic->shift()) {
                         caseFormatter.ensureLength(1, textCase);
@@ -1370,16 +1370,16 @@ public:
                 }
                 if (i == 0) {
                     resultString = resultChars;
-                    if (result.contains("gesture"))
-                        gesture = result["gesture"].toString();
-                    if (sessionSettings.recognitionMode != scrMode && result.contains("symbolStrokes"))
-                        symbolStrokes = result["symbolStrokes"].toList();
+                    if (result.contains(QLatin1String("gesture")))
+                        gesture = result[QLatin1String("gesture")].toString();
+                    if (sessionSettings.recognitionMode != scrMode && result.contains(QLatin1String("symbolStrokes")))
+                        symbolStrokes = result[QLatin1String("symbolStrokes")].toList();
                     if (sessionSettings.recognitionMode == scrMode)
                         break;
                 } else {
                     // Add a gesture symbol to the secondary candidate
-                    if (sessionSettings.recognitionMode != scrMode && result.contains("gesture")) {
-                        QString gesture2 = result["gesture"].toString();
+                    if (sessionSettings.recognitionMode != scrMode && result.contains(QLatin1String("gesture"))) {
+                        QString gesture2 = result[QLatin1String("gesture")].toString();
                         if (gesture2.length() == 1) {
                             QChar symbol = T9WriteInputMethodPrivate::mapGestureToSymbol(gesture2.at(0).unicode());
                             if (!symbol.isNull()) {
@@ -1485,9 +1485,9 @@ public:
     {
         switch (symbol.unicode()) {
         case 0x23CE:
-            return QChar('\r');
+            return QLatin1Char('\r');
         case 0x2423:
-            return QChar(' ');
+            return QLatin1Char(' ');
         default:
             return QChar();
         }
@@ -1553,7 +1553,7 @@ public:
                     if (swipeAngle <= SWIPE_ANGLE_THRESHOLD || swipeAngle >= 360 - SWIPE_ANGLE_THRESHOLD) {
                         if (swipeTouchCount == 1) {
                             // Single swipe: space
-                            ic->inputEngine()->virtualKeyClick(Qt::Key_Space, QString(" "), Qt::NoModifier);
+                            ic->inputEngine()->virtualKeyClick(Qt::Key_Space, QLatin1String(" "), Qt::NoModifier);
                             return true;
                         }
                         return false;
@@ -2089,15 +2089,18 @@ void T9WriteInputMethod::resultsAvailable(const QVariantList &resultList)
         qCDebug(lcT9Write) << "T9WriteInputMethod::resultsAvailable():";
         for (int i = 0; i < resultList.size(); i++) {
             QVariantMap result = resultList.at(i).toMap();
-            QString resultPrint = QString("%1: ").arg(i + 1);
-            QString resultChars = result.value("chars").toString();
+            QString resultPrint = QStringLiteral("%1: ").arg(i + 1);
+            QString resultChars = result.value(QLatin1String("chars")).toString();
             if (!resultChars.isEmpty())
                 resultPrint.append(resultChars);
-            if (result.contains("gesture")) {
+            if (result.contains(QLatin1String("gesture"))) {
                 if (!resultChars.isEmpty())
-                    resultPrint.append(", ");
-                resultPrint.append("gesture = 0x");
-                resultPrint.append(result["gesture"].toString().toUtf8().toHex());
+                    resultPrint.append(QLatin1String(", "));
+                QString gesture = result[QLatin1String("gesture")].toString();
+                resultPrint.append(QLatin1String("gesture ="));
+                for (const QChar &chr : gesture) {
+                    resultPrint.append(QString::fromLatin1(" 0x%1").arg(chr.unicode(), 0, 16));
+                }
             }
             qCDebug(lcT9Write) << resultPrint.toUtf8().constData();
         }
diff --git a/src/plugins/t9write/plugin/t9writeworker.cpp b/src/plugins/t9write/plugin/t9writeworker.cpp
index 68fadf27..be9b4d9e 100644
--- a/src/plugins/t9write/plugin/t9writeworker.cpp
+++ b/src/plugins/t9write/plugin/t9writeworker.cpp
@@ -288,11 +288,11 @@ void T9WriteRecognitionResultsTask::run()
                 symbolStrokes.append(QVariant((int)hwrResult.pSymbolStrokes[symbolIndex]));
         }
 
-        resultMap["resultId"] = result->id;
-        resultMap["chars"] = resultString;
-        resultMap["symbolStrokes"] = symbolStrokes;
+        resultMap[QLatin1String("resultId")] = result->id;
+        resultMap[QLatin1String("chars")] = resultString;
+        resultMap[QLatin1String("symbolStrokes")] = symbolStrokes;
         if (!gesture.isEmpty())
-            resultMap["gesture"] = gesture;
+            resultMap[QLatin1String("gesture")] = gesture;
 
         resultList.append(resultMap);
     }
diff --git a/src/plugins/tcime/3rdparty/tcime/cangjiedictionary.cpp b/src/plugins/tcime/3rdparty/tcime/cangjiedictionary.cpp
index 1a50d371..7326b839 100644
--- a/src/plugins/tcime/3rdparty/tcime/cangjiedictionary.cpp
+++ b/src/plugins/tcime/3rdparty/tcime/cangjiedictionary.cpp
@@ -28,7 +28,7 @@ bool CangjieDictionary::_simplified = false;
 
 CangjieDictionary::CangjieDictionary() :
     WordDictionary(),
-    _collator(QLocale("zh_TW"))
+    _collator(QLocale(QLatin1String("zh_TW")))
 {
 }
 
diff --git a/src/plugins/tcime/3rdparty/tcime/tcime.pro b/src/plugins/tcime/3rdparty/tcime/tcime.pro
index 55ce8f81..d9fc4f2e 100644
--- a/src/plugins/tcime/3rdparty/tcime/tcime.pro
+++ b/src/plugins/tcime/3rdparty/tcime/tcime.pro
@@ -22,6 +22,12 @@ OTHER_FILES += \
     data/dict_cangjie.dat \
     data/dict_phrases.dat
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 MODULE_INCLUDEPATH = $$PWD
 MODULE_DEFINES = HAVE_TCIME
 
diff --git a/src/plugins/tcime/3rdparty/tcime/zhuyintable.cpp b/src/plugins/tcime/3rdparty/tcime/zhuyintable.cpp
index c405b1e3..8198122a 100644
--- a/src/plugins/tcime/3rdparty/tcime/zhuyintable.cpp
+++ b/src/plugins/tcime/3rdparty/tcime/zhuyintable.cpp
@@ -41,7 +41,7 @@ const QChar ZhuyinTable::WU_FINALS = 0x3128;
 const QChar ZhuyinTable::YU_FINALS = 0x3129;
 const QList<QChar> ZhuyinTable::tones = QList<QChar>()
         << ZhuyinTable::DEFAULT_TONE << 0x02d9 << 0x02ca << 0x02c7 << 0x02cb;
-const QChar ZhuyinTable::DEFAULT_TONE = QChar(' ');
+const QChar ZhuyinTable::DEFAULT_TONE = QLatin1Char(' ');
 
 int ZhuyinTable::getInitials(const QChar &initials)
 {
diff --git a/src/plugins/tcime/plugin/plugin.pro b/src/plugins/tcime/plugin/plugin.pro
index b50b8402..9ac49798 100644
--- a/src/plugins/tcime/plugin/plugin.pro
+++ b/src/plugins/tcime/plugin/plugin.pro
@@ -10,6 +10,12 @@ SOURCES += \
 OTHER_FILES += \
     tcime.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 
 LAYOUT_FILES += \
diff --git a/src/plugins/tcime/plugin/tcinputmethod.cpp b/src/plugins/tcime/plugin/tcinputmethod.cpp
index e347979a..abbbdd36 100644
--- a/src/plugins/tcime/plugin/tcinputmethod.cpp
+++ b/src/plugins/tcime/plugin/tcinputmethod.cpp
@@ -378,7 +378,7 @@ bool TCInputMethod::setInputMode(const QString &locale, QVirtualKeyboardInputEng
             if (!QFileInfo::exists(cangjieDictionary)) {
                 cangjieDictionary = QLatin1String(":///QtQuick/VirtualKeyboard/3rdparty/tcime/data/qt/dict_cangjie.dat");
                 if (!QFileInfo::exists(cangjieDictionary))
-                    cangjieDictionary = QLibraryInfo::location(QLibraryInfo::DataPath) + "/qtvirtualkeyboard/tcime/dict_cangjie.dat";
+                    cangjieDictionary = QLibraryInfo::location(QLibraryInfo::DataPath) + QLatin1String("/qtvirtualkeyboard/tcime/dict_cangjie.dat");
             }
             d->cangjieDictionary.load(cangjieDictionary);
         }
@@ -392,7 +392,7 @@ bool TCInputMethod::setInputMode(const QString &locale, QVirtualKeyboardInputEng
             if (!QFileInfo::exists(zhuyinDictionary)) {
                 zhuyinDictionary = QLatin1String(":///QtQuick/VirtualKeyboard/3rdparty/tcime/data/qt/dict_zhuyin.dat");
                 if (!QFileInfo::exists(zhuyinDictionary))
-                    zhuyinDictionary = QLibraryInfo::location(QLibraryInfo::DataPath) + "/qtvirtualkeyboard/tcime/dict_zhuyin.dat";
+                    zhuyinDictionary = QLibraryInfo::location(QLibraryInfo::DataPath) + QLatin1String("/qtvirtualkeyboard/tcime/dict_zhuyin.dat");
             }
             d->zhuyinDictionary.load(zhuyinDictionary);
         }
@@ -405,7 +405,7 @@ bool TCInputMethod::setInputMode(const QString &locale, QVirtualKeyboardInputEng
         if (!QFileInfo::exists(phraseDictionary)) {
             phraseDictionary = QLatin1String(":///QtQuick/VirtualKeyboard/3rdparty/tcime/data/qt/dict_phrases.dat");
             if (!QFileInfo::exists(phraseDictionary))
-                phraseDictionary = QLibraryInfo::location(QLibraryInfo::DataPath) + "/qtvirtualkeyboard/tcime/dict_phrases.dat";
+                phraseDictionary = QLibraryInfo::location(QLibraryInfo::DataPath) + QLatin1String("/qtvirtualkeyboard/tcime/dict_phrases.dat");
         }
         d->phraseDictionary.load(phraseDictionary);
     }
diff --git a/src/plugins/thai/plugin/plugin.pro b/src/plugins/thai/plugin/plugin.pro
index 65d61709..81f05b4b 100644
--- a/src/plugins/thai/plugin/plugin.pro
+++ b/src/plugins/thai/plugin/plugin.pro
@@ -10,6 +10,12 @@ SOURCES += \
 OTHER_FILES += \
     thai.json
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 include(../../../config.pri)
 
 !disable-hunspell {
diff --git a/src/plugins/thai/plugin/thaiinputmethod.cpp b/src/plugins/thai/plugin/thaiinputmethod.cpp
index 02e7603a..57dc8a67 100644
--- a/src/plugins/thai/plugin/thaiinputmethod.cpp
+++ b/src/plugins/thai/plugin/thaiinputmethod.cpp
@@ -71,7 +71,7 @@ bool ThaiInputMethod::keyEvent(Qt::Key key,
                                const QString &text,
                                Qt::KeyboardModifiers modifiers)
 {
-    const bool isMark = text.length() == 2 && text.at(0) == QChar(' ');
+    const bool isMark = text.length() == 2 && text.at(0) == QLatin1Char(' ');
 #ifdef QT_HUNSPELLINPUTMETHOD_LIB
     if (isMark) {
         const QString mark(text.right(1));
diff --git a/src/styles/styles.pro b/src/styles/styles.pro
index 85c99f05..aa7280e2 100644
--- a/src/styles/styles.pro
+++ b/src/styles/styles.pro
@@ -20,6 +20,12 @@ OTHER_FILES += \
     plugins.qmltypes \
     qmldir
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 win32 {
     QMAKE_TARGET_PRODUCT = "Qt Virtual Keyboard (Qt $$QT_VERSION)"
     QMAKE_TARGET_DESCRIPTION = "Virtual Keyboard for Qt."
diff --git a/src/styles/svgimageprovider.cpp b/src/styles/svgimageprovider.cpp
index 1dd2930f..d4e16d80 100644
--- a/src/styles/svgimageprovider.cpp
+++ b/src/styles/svgimageprovider.cpp
@@ -46,24 +46,24 @@ QPixmap SvgImageProvider::requestPixmap(const QString &id, QSize *size, const QS
 {
     QSize imageSize(-1, -1);
     QUrl request(id);
-    QString imagePath = ":/" + request.path();
+    QString imagePath = QLatin1String(":/") + request.path();
     if (request.hasQuery()) {
         const QString query = request.query();
-        const QStringList paramList = query.split(QChar('&'), QString::SkipEmptyParts);
+        const QStringList paramList = query.split(QLatin1Char('&'), QString::SkipEmptyParts);
         QVariantMap params;
         for (const QString &param : paramList) {
-            QStringList keyValue = param.split(QChar('='), QString::SkipEmptyParts);
+            QStringList keyValue = param.split(QLatin1Char('='), QString::SkipEmptyParts);
             if (keyValue.length() == 2)
                 params[keyValue[0]] = keyValue[1];
         }
-        const auto widthIt = params.constFind("width");
+        const auto widthIt = params.constFind(QLatin1String("width"));
         if (widthIt != params.cend()) {
             bool ok = false;
             int value = widthIt.value().toInt(&ok);
             if (ok)
                 imageSize.setWidth(value);
         }
-        const auto heightIt = params.constFind("height");
+        const auto heightIt = params.constFind(QLatin1String("height"));
         if (heightIt != params.cend()) {
             bool ok = false;
             int value = heightIt.value().toInt(&ok);
@@ -75,7 +75,7 @@ QPixmap SvgImageProvider::requestPixmap(const QString &id, QSize *size, const QS
     }
 
     QPixmap image;
-    if ((imageSize.width() > 0 || imageSize.height() > 0) && imagePath.endsWith(".svg")) {
+    if ((imageSize.width() > 0 || imageSize.height() > 0) && imagePath.endsWith(QLatin1String(".svg"))) {
         QSvgRenderer renderer(imagePath);
         QSize defaultSize(renderer.defaultSize());
         if (defaultSize.isEmpty())
diff --git a/src/virtualkeyboard/desktopinputpanel.cpp b/src/virtualkeyboard/desktopinputpanel.cpp
index 5b5e52d3..aee0f100 100644
--- a/src/virtualkeyboard/desktopinputpanel.cpp
+++ b/src/virtualkeyboard/desktopinputpanel.cpp
@@ -154,7 +154,7 @@ void DesktopInputPanel::createView()
             break;
         }
         d->view->setColor(QColor(Qt::transparent));
-        d->view->setSource(QUrl("qrc:///QtQuick/VirtualKeyboard/content/InputPanel.qml"));
+        d->view->setSource(QUrl(QLatin1String("qrc:///QtQuick/VirtualKeyboard/content/InputPanel.qml")));
         if (QGuiApplication *app = qGuiApp)
             connect(app, SIGNAL(aboutToQuit()), SLOT(destroyView()));
     }
diff --git a/src/virtualkeyboard/qvirtualkeyboardabstractinputmethod.cpp b/src/virtualkeyboard/qvirtualkeyboardabstractinputmethod.cpp
index e4cca1b1..8ca0cdba 100644
--- a/src/virtualkeyboard/qvirtualkeyboardabstractinputmethod.cpp
+++ b/src/virtualkeyboard/qvirtualkeyboardabstractinputmethod.cpp
@@ -151,7 +151,7 @@ QVariant QVirtualKeyboardAbstractInputMethod::selectionListData(QVirtualKeyboard
     Q_UNUSED(index)
     switch (role) {
     case QVirtualKeyboardSelectionListModel::Role::Display:
-        return QVariant("");
+        return QVariant(QString());
     case QVirtualKeyboardSelectionListModel::Role::WordCompletionLength:
         return QVariant(0);
     case QVirtualKeyboardSelectionListModel::Role::Dictionary:
diff --git a/src/virtualkeyboard/unipentrace.cpp b/src/virtualkeyboard/unipentrace.cpp
index 1ced292d..eca531c2 100644
--- a/src/virtualkeyboard/unipentrace.cpp
+++ b/src/virtualkeyboard/unipentrace.cpp
@@ -45,19 +45,19 @@ UnipenTrace::UnipenTrace(const QVariantMap &traceCaptureDeviceInfo,
     m_lines.append(QLatin1String(".HIERARCHY CHARACTER"));
     m_lines.append(QLatin1String(".COORD X Y T"));
     m_lines.append(QLatin1String(".SEGMENT CHARACTER"));
-    const QRectF boundingBox = traceScreenInfo["boundingBox"].toRectF();
+    const QRectF boundingBox = traceScreenInfo[QLatin1String("boundingBox")].toRectF();
     if (!boundingBox.isEmpty()) {
         m_lines.append(QStringLiteral(".X_DIM %1").arg(qRound(boundingBox.right())));
         m_lines.append(QStringLiteral(".Y_DIM %1").arg(qRound(boundingBox.bottom())));
     }
     bool ok = false;
-    int dpi = traceCaptureDeviceInfo["dpi"].toInt(&ok);
+    int dpi = traceCaptureDeviceInfo[QLatin1String("dpi")].toInt(&ok);
     if (ok) {
         m_lines.append(QStringLiteral(".X_POINTS_PER_INCH %1").arg(dpi));
         m_lines.append(QStringLiteral(".Y_POINTS_PER_INCH %1").arg(dpi));
     }
     ok = false;
-    int sampleRate = traceCaptureDeviceInfo["sampleRate"].toInt(&ok);
+    int sampleRate = traceCaptureDeviceInfo[QLatin1String("sampleRate")].toInt(&ok);
     if (ok)
         m_lines.append(QStringLiteral(".POINTS_PER_SECOND %1").arg(sampleRate));
 }
@@ -67,8 +67,8 @@ void UnipenTrace::record(const QList<QVirtualKeyboardTrace *> &traceList)
     qlonglong t0 = 0;
     for (const QVirtualKeyboardTrace *trace : qAsConst(traceList)) {
         const QVariantList &points = trace->points();
-        const bool hasTime = trace->channels().contains("t");
-        const QVariantList timeData = hasTime ? trace->channelData("t") : QVariantList();
+        const bool hasTime = trace->channels().contains(QLatin1String("t"));
+        const QVariantList timeData = hasTime ? trace->channelData(QLatin1String("t")) : QVariantList();
         QVariantList::ConstIterator t = timeData.constBegin();
         if (t0 == 0 && hasTime)
             t0 = t->toLongLong();
@@ -107,8 +107,8 @@ void UnipenTrace::save(uint unicode, uint confidence)
         } while (QFileInfo::exists(fileName));
     }
 
-    QString dataStr(m_lines.join('\n'));
-    dataStr.append('\n');
+    QString dataStr(m_lines.join(QLatin1Char('\n')));
+    dataStr.append(QLatin1Char('\n'));
     QFile file(fileName);
     if (file.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Truncate)) {
         file.write(dataStr.toUtf8().constData());
diff --git a/src/virtualkeyboard/virtualkeyboard.pro b/src/virtualkeyboard/virtualkeyboard.pro
index 92cdab88..cb28d6a1 100644
--- a/src/virtualkeyboard/virtualkeyboard.pro
+++ b/src/virtualkeyboard/virtualkeyboard.pro
@@ -387,6 +387,12 @@ no-builtin-style {
 
 DEFINES += QT_VIRTUALKEYBOARD_DEFAULT_LAYOUTS_DIR=\\\"qrc:/QtQuick/VirtualKeyboard/content/layouts\\\"
 
+DEFINES += \
+    QT_NO_CAST_TO_ASCII \
+    QT_ASCII_CAST_WARNINGS \
+    QT_NO_CAST_FROM_ASCII \
+    QT_NO_CAST_FROM_BYTEARRAY
+
 OTHER_FILES += \
     content/styles/default/*.qml \
     content/styles/retro/*.qml \
diff --git a/src/virtualkeyboard/virtualkeyboardsettings.cpp b/src/virtualkeyboard/virtualkeyboardsettings.cpp
index b5c1a339..5f9e82f0 100644
--- a/src/virtualkeyboard/virtualkeyboardsettings.cpp
+++ b/src/virtualkeyboard/virtualkeyboardsettings.cpp
@@ -49,8 +49,8 @@ public:
 
     QString buildStyleImportPath(const QString &path, const QString &name) const
     {
-        QString importPath(path + name + "/style.qml");
-        if (!importPath.startsWith("qrc:")) {
+        QString importPath(path + name + QLatin1String("/style.qml"));
+        if (!importPath.startsWith(QLatin1String("qrc:"))) {
             QUrl url = QUrl::fromLocalFile(importPath);
             importPath = url.toString();
         }
@@ -60,9 +60,9 @@ public:
     QString buildStyleFilePath(const QString &path, const QString &name) const
     {
         QString filePath(path);
-        if (filePath.startsWith("qrc:"))
+        if (filePath.startsWith(QLatin1String("qrc:")))
             filePath.remove(0, 3);
-        return filePath + name + "/style.qml";
+        return filePath + name + QLatin1String("/style.qml");
     }
 
     QString styleImportPath(const QString &name) const
@@ -71,12 +71,12 @@ public:
             return QString();
 
         QStringList styleImportPathList;
-        styleImportPathList << "qrc:/QtQuick/VirtualKeyboard/content/styles/";
+        styleImportPathList << QLatin1String("qrc:/QtQuick/VirtualKeyboard/content/styles/");
         const QStringList importPathList = engine->importPathList();
         // Add QML import path (Note: the QML base dir is usually the last entry in the list)
         for (int i = importPathList.size() - 1; i >= 0; --i) {
             const QString stylesPath = importPathList.at(i)
-                + QStringLiteral("/QtQuick/VirtualKeyboard/Styles/");
+                + QLatin1String("/QtQuick/VirtualKeyboard/Styles/");
             styleImportPathList += stylesPath;
         }
 
@@ -226,7 +226,7 @@ void VirtualKeyboardSettings::setLayoutPath(const QUrl &layoutPath)
 void VirtualKeyboardSettings::resetLayoutPath()
 {
     Settings *settings = Settings::instance();
-    QUrl layoutPath(QT_VIRTUALKEYBOARD_DEFAULT_LAYOUTS_DIR);
+    QUrl layoutPath(QLatin1String(QT_VIRTUALKEYBOARD_DEFAULT_LAYOUTS_DIR));
     const QString customLayoutPath(QDir::fromNativeSeparators(qEnvironmentVariable("QT_VIRTUALKEYBOARD_LAYOUT_PATH")));
     if (!customLayoutPath.isEmpty()) {
         bool found = false;
@@ -293,12 +293,12 @@ void VirtualKeyboardSettings::resetStyle()
 {
     Q_D(VirtualKeyboardSettings);
     Settings *settings = Settings::instance();
-    QString styleName = QT_VIRTUALKEYBOARD_DEFAULT_STYLE;
+    QString styleName = QLatin1String(QT_VIRTUALKEYBOARD_DEFAULT_STYLE);
     QString style = d->styleImportPath(styleName);
-    QString customStyleName = qgetenv("QT_VIRTUALKEYBOARD_STYLE");
+    QString customStyleName = QString::fromLatin1(qgetenv("QT_VIRTUALKEYBOARD_STYLE"));
     if (!customStyleName.isEmpty()) {
         bool found = false;
-        QRegularExpression styleNameValidator("\\A(?:\\w+)\\z");
+        QRegularExpression styleNameValidator(QLatin1String("\\A(?:\\w+)\\z"));
         QRegularExpressionMatch match = styleNameValidator.match(customStyleName);
         if (match.hasMatch()) {
             QString customStyle = d->styleImportPath(customStyleName);