Use QStringBuilder more to optimize memory allocations

Change-Id: I2939ffa10496fdc59e0402a9cb54458565ccd657
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qlibraryinfo.cpp

@@ -616,10 +616,10 @@ QStringList QLibraryInfo::platformPluginArguments(const QString &platformName)
 #if !defined(QT_BUILD_QMAKE) && !defined(QT_NO_SETTINGS)
     QScopedPointer<const QSettings> settings(QLibraryInfoPrivate::findConfiguration());
     if (!settings.isNull()) {
-        QString key = QLatin1String(platformsSection);
-        key += QLatin1Char('/');
-        key += platformName;
-        key += QLatin1String("Arguments");
+        const QString key = QLatin1String(platformsSection)
+                + QLatin1Char('/')
+                + platformName
+                + QLatin1String("Arguments");
         return settings->value(key).toStringList();
     }
 #endif // !QT_BUILD_QMAKE && !QT_NO_SETTINGS

src/gui/text/qfontdatabase.cpp

@@ -663,11 +663,8 @@ struct QtFontDesc
 static void initFontDef(const QtFontDesc &desc, const QFontDef &request, QFontDef *fontDef, bool multi)
 {
     fontDef->family = desc.family->name;
-    if (! desc.foundry->name.isEmpty() && desc.family->count > 1) {
-        fontDef->family += QString::fromLatin1(" [");
-        fontDef->family += desc.foundry->name;
-        fontDef->family += QLatin1Char(']');
-    }
+    if (! desc.foundry->name.isEmpty() && desc.family->count > 1)
+        fontDef->family += QLatin1String(" [") + desc.foundry->name + QLatin1Char(']');
 
     if (desc.style->smoothScalable
         || QGuiApplicationPrivate::platformIntegration()->fontDatabase()->fontsAlwaysScalable()

src/gui/text/qplatformfontdatabase.cpp

@@ -395,10 +395,8 @@ void QPlatformFontDatabase::releaseHandle(void *handle)
 QString QPlatformFontDatabase::fontDir() const
 {
     QString fontpath = QString::fromLocal8Bit(qgetenv("QT_QPA_FONTDIR"));
-    if (fontpath.isEmpty()) {
-        fontpath = QLibraryInfo::location(QLibraryInfo::LibrariesPath);
-        fontpath += QLatin1String("/fonts");
-    }
+    if (fontpath.isEmpty())
+        fontpath = QLibraryInfo::location(QLibraryInfo::LibrariesPath) + QLatin1String("/fonts");
 
     return fontpath;
 }

src/platformsupport/themes/qabstractfileiconengine.cpp

@@ -73,8 +73,7 @@ QPixmap QAbstractFileIconEngine::pixmap(const QSize &size, QIcon::Mode mode,
     if (key.isEmpty())
         return filePixmap(size, mode, state);
 
-    key += QLatin1Char('_');
-    key += QString::number(size.width());
+    key += QLatin1Char('_') + QString::number(size.width());
 
     QPixmap result;
     if (!QPixmapCache::find(key, result)) {

src/plugins/platforms/xcb/qxcbmime.cpp

@@ -121,9 +121,7 @@ bool QXcbMime::mimeDataForAtom(QXcbConnection *connection, xcb_atom_t a, QMimeDa
         // so QXcbConnection::atomName() has to be used.
         if (atomName == QLatin1String("text/uri-list")
             && connection->atomName(a) == "text/x-moz-url") {
-            const QByteArray uri = data->split('\n').first();
-            QString mozUri = QString::fromLatin1(uri, uri.size());
-            mozUri += QLatin1Char('\n');
+            const QString mozUri = QLatin1String(data->split('\n').constFirst()) + QLatin1Char('\n');
             *data = QByteArray(reinterpret_cast<const char *>(mozUri.utf16()),
                                mozUri.length() * 2);
         } else if (atomName == QLatin1String("application/x-color"))

src/plugins/platforms/xcb/qxcbscreen.cpp

@@ -61,8 +61,7 @@ QXcbVirtualDesktop::QXcbVirtualDesktop(QXcbConnection *connection, xcb_screen_t
     , m_number(number)
     , m_xSettings(Q_NULLPTR)
 {
-    QByteArray cmAtomName("_NET_WM_CM_S");
-    cmAtomName += QByteArray::number(m_number);
+    const QByteArray cmAtomName =  "_NET_WM_CM_S" + QByteArray::number(m_number);
     m_net_wm_cm_atom = connection->internAtom(cmAtomName.constData());
     m_compositingActive = connection->getSelectionOwner(m_net_wm_cm_atom);
 

src/tools/rcc/rcc.cpp

@@ -705,9 +705,7 @@ static void resourceDataFileMapRecursion(const RCCFileInfo *m_root, const QStrin
     const ChildConstIterator cend = m_root->m_children.constEnd();
     for (ChildConstIterator it = m_root->m_children.constBegin(); it != cend; ++it) {
         const RCCFileInfo *child = it.value();
-        QString childName = path;
-        childName += slash;
-        childName += child->m_name;
+        const QString childName = path + slash + child->m_name;
         if (child->m_flags & RCCFileInfo::Directory) {
             resourceDataFileMapRecursion(child, childName, m);
         } else {