Qml: optimize string usage

Use QStringBuilder more.
Use QString::asprintf instead of arg()'s chain.
Use += operator to reserve extra capacity for
possible free following append/prepend/+= call.

Change-Id: Ib65398b91566994339d2c4bbfaf94e49806b7471
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

12 files changed, 46 insertions, 55 deletions

diff --git a/src/qml/qml/qqmlbinding.cpp b/src/qml/qml/qqmlbinding.cpp
index 72c7347a68..3b3e23c891 100644
--- a/src/qml/qml/qqmlbinding.cpp
+++ b/src/qml/qml/qqmlbinding.cpp
@@ -378,12 +378,11 @@ Q_NEVER_INLINE bool QQmlBinding::slowWrite(const QQmlPropertyData &core,
                                QJSValue(QV8Engine::getV4(v8engine), result.asReturnedValue())),
                            context(), flags);
     } else if (isUndefined) {
-        QString errorStr = QLatin1String("Unable to assign [undefined] to ");
-        if (!QMetaType::typeName(type))
-            errorStr += QLatin1String("[unknown property type]");
-        else
-            errorStr += QLatin1String(QMetaType::typeName(type));
-        delayedError()->setErrorDescription(errorStr);
+        const QLatin1String typeName(QMetaType::typeName(type)
+                                     ? QMetaType::typeName(type)
+                                     : "[unknown property type]");
+        delayedError()->setErrorDescription(QLatin1String("Unable to assign [undefined] to ")
+                                            + typeName);
         return false;
     } else if (const QV4::FunctionObject *f = result.as<QV4::FunctionObject>()) {
         if (f->isBinding())
@@ -458,8 +457,7 @@ QString QQmlBinding::expressionIdentifier()
     QString url = function->sourceFile();
     quint16 lineNumber = function->compiledFunction->location.line;
     quint16 columnNumber = function->compiledFunction->location.column;
-
-    return url + QLatin1Char(':') + QString::number(lineNumber) + QLatin1Char(':') + QString::number(columnNumber);
+    return url + QString::asprintf(":%u:%u", uint(lineNumber), uint(columnNumber));
 }
 
 void QQmlBinding::expressionChanged()
diff --git a/src/qml/qml/qqmlboundsignal.cpp b/src/qml/qml/qqmlboundsignal.cpp
index ef837183db..4e63790290 100644
--- a/src/qml/qml/qqmlboundsignal.cpp
+++ b/src/qml/qml/qqmlboundsignal.cpp
@@ -80,8 +80,8 @@ QQmlBoundSignalExpression::QQmlBoundSignalExpression(QObject *target, int index,
 
     // Add some leading whitespace to account for the binding's column offset.
     // It's 2 off because a, we start counting at 1 and b, the '(' below is not counted.
-    function.fill(QChar(QChar::Space), qMax(column, (quint16)2) - 2);
-    function += QLatin1String("(function ") + handlerName + QLatin1Char('(');
+    function += QString(qMax(column, (quint16)2) - 2, QChar(QChar::Space))
+              + QLatin1String("(function ") + handlerName + QLatin1Char('(');
 
     if (parameterString.isEmpty()) {
         QString error;
diff --git a/src/qml/qml/qqmlerror.cpp b/src/qml/qml/qqmlerror.cpp
index 74ceeabeb4..b309550ca8 100644
--- a/src/qml/qml/qqmlerror.cpp
+++ b/src/qml/qml/qqmlerror.cpp
@@ -249,9 +249,9 @@ QString QQmlError::toString() const
     int l(line());
 
     if (u.isEmpty() || (u.isLocalFile() && u.path().isEmpty()))
-        rv = QLatin1String("<Unknown File>");
+        rv += QLatin1String("<Unknown File>");
     else
-        rv = u.toString();
+        rv += u.toString();
 
     if (l != -1) {
         rv += QLatin1Char(':') + QString::number(l);
diff --git a/src/qml/qml/qqmlimport.cpp b/src/qml/qml/qqmlimport.cpp
index 6396ad0bab..63e8da3aa8 100644
--- a/src/qml/qml/qqmlimport.cpp
+++ b/src/qml/qml/qqmlimport.cpp
@@ -538,10 +538,10 @@ QString QQmlImports::versionString(int vmaj, int vmin, ImportVersion version)
 {
     if (version == QQmlImports::FullyVersioned) {
         // extension with fully encoded version number (eg. MyModule.3.2)
-        return QString(QLatin1String(".%1.%2")).arg(vmaj).arg(vmin);
+        return QString::asprintf(".%d.%d", vmaj, vmin);
     } else if (version == QQmlImports::PartiallyVersioned) {
         // extension with encoded version major (eg. MyModule.3)
-        return QString(QLatin1String(".%1")).arg(vmaj);
+        return QString::asprintf(".%d", vmaj);
     } // else extension without version number (eg. MyModule)
     return QString();
 }
@@ -1393,15 +1393,9 @@ bool QQmlImportsPrivate::addFileImport(const QString& uri, const QString &prefix
     // The uri for this import.  For library imports this is the same as uri
     // specified by the user, but it may be different in the case of file imports.
     QString importUri = uri;
-
-    QString qmldirPath = importUri;
-    if (importUri.endsWith(Slash))
-        qmldirPath += String_qmldir;
-    else
-        qmldirPath += Slash_qmldir;
-
-    QString qmldirUrl = resolveLocalUrl(base, qmldirPath);
-
+    QString qmldirUrl = resolveLocalUrl(base, importUri + (importUri.endsWith(Slash)
+                                                           ? String_qmldir
+                                                           : Slash_qmldir));
     QString qmldirIdentifier;
 
     if (QQmlFile::isLocalFile(qmldirUrl)) {
@@ -1699,10 +1693,9 @@ QString QQmlImportDatabase::resolvePlugin(QQmlTypeLoader *typeLoader,
         if (!resolvedPath.endsWith(Slash))
             resolvedPath += Slash;
 
+        resolvedPath += prefix + baseName;
         foreach (const QString &suffix, suffixes) {
-            QString pluginFileName = prefix + baseName + suffix;
-
-            QString absolutePath = typeLoader->absoluteFilePath(resolvedPath + pluginFileName);
+            const QString absolutePath = typeLoader->absoluteFilePath(resolvedPath + suffix);
             if (!absolutePath.isEmpty())
                 return absolutePath;
         }
@@ -1955,7 +1948,7 @@ bool QQmlImportDatabase::importStaticPlugin(QObject *instance, const QString &ba
 #ifndef QT_NO_LIBRARY
     // Dynamic plugins are differentiated by their filepath. For static plugins we
     // don't have that information so we use their address as key instead.
-    QString uniquePluginID = QString().sprintf("%p", instance);
+    const QString uniquePluginID = QString::asprintf("%p", instance);
     StringRegisteredPluginMap *plugins = qmlEnginePluginsWithRegisteredTypes();
     QMutexLocker lock(&plugins->mutex);
 
diff --git a/src/qml/qml/qqmlproperty.cpp b/src/qml/qml/qqmlproperty.cpp
index ffa9bfa3a7..e287b68385 100644
--- a/src/qml/qml/qqmlproperty.cpp
+++ b/src/qml/qml/qqmlproperty.cpp
@@ -644,15 +644,11 @@ QString QQmlProperty::name() const
         // ###
         if (!d->object) {
         } else if (d->isValueType()) {
-            QString rv = d->core.name(d->object) + QLatin1Char('.');
-
             const QMetaObject *valueTypeMetaObject = QQmlValueTypeFactory::metaObjectForMetaType(d->core.propType);
             Q_ASSERT(valueTypeMetaObject);
 
             const char *vtName = valueTypeMetaObject->property(d->valueTypeData.coreIndex).name();
-            rv += QString::fromUtf8(vtName);
-
-            d->nameCache = rv;
+            d->nameCache = d->core.name(d->object) + QLatin1Char('.') + QString::fromUtf8(vtName);
         } else if (type() & SignalProperty) {
             QString name = QLatin1String("on") + d->core.name(d->object);
             name[2] = name.at(2).toUpper();
diff --git a/src/qml/qml/qqmlpropertycache.cpp b/src/qml/qml/qqmlpropertycache.cpp
index 71b3fd8309..38fddc8253 100644
--- a/src/qml/qml/qqmlpropertycache.cpp
+++ b/src/qml/qml/qqmlpropertycache.cpp
@@ -1195,7 +1195,9 @@ void QQmlPropertyCache::toMetaObjectBuilder(QMetaObjectBuilder &builder)
         if (data->propType != 0)
             returnType = QMetaType::typeName(data->propType);
 
-        QByteArray signature = methods.at(ii).first.toUtf8() + '(';
+        QByteArray signature;
+        // '+=' reserves extra capacity. Follow-up appending will be probably free.
+        signature += methods.at(ii).first.toUtf8() + '(';
 
         QQmlPropertyCacheMethodArguments *arguments = 0;
         if (data->hasArguments()) {
diff --git a/src/qml/qml/qqmltypeloader.cpp b/src/qml/qml/qqmltypeloader.cpp
index b7154625ee..a151f50a00 100644
--- a/src/qml/qml/qqmltypeloader.cpp
+++ b/src/qml/qml/qqmltypeloader.cpp
@@ -2534,13 +2534,13 @@ void QQmlTypeData::resolveTypes()
 
         ScriptReference ref;
         //ref.location = ...
-        ref.qualifier = script.nameSpace;
         if (!script.qualifier.isEmpty())
         {
-            ref.qualifier.prepend(script.qualifier + QLatin1Char('.'));
-
+            ref.qualifier = script.qualifier + QLatin1Char('.') + script.nameSpace;
             // Add a reference to the enclosing namespace
             m_namespaces.insert(script.qualifier);
+        } else {
+            ref.qualifier = script.nameSpace;
         }
 
         ref.script = blob;
@@ -2550,12 +2550,13 @@ void QQmlTypeData::resolveTypes()
     // Lets handle resolved composite singleton types
     foreach (const QQmlImports::CompositeSingletonReference &csRef, m_importCache.resolvedCompositeSingletons()) {
         TypeReference ref;
-        QString typeName = csRef.typeName;
-
+        QString typeName;
         if (!csRef.prefix.isEmpty()) {
-            typeName.prepend(csRef.prefix + QLatin1Char('.'));
+            typeName = csRef.prefix + QLatin1Char('.') + csRef.typeName;
             // Add a reference to the enclosing namespace
             m_namespaces.insert(csRef.prefix);
+        } else {
+            typeName = csRef.typeName;
         }
 
         int majorVersion = csRef.majorVersion > -1 ? csRef.majorVersion : -1;
diff --git a/src/qml/qml/qqmlvaluetype.cpp b/src/qml/qml/qqmlvaluetype.cpp
index eefe7a5fb8..bcefad0ee3 100644
--- a/src/qml/qml/qqmlvaluetype.cpp
+++ b/src/qml/qml/qqmlvaluetype.cpp
@@ -260,7 +260,7 @@ int QQmlValueType::metaCall(QObject *, QMetaObject::Call type, int _id, void **a
 
 QString QQmlPointFValueType::toString() const
 {
-    return QString(QLatin1String("QPointF(%1, %2)")).arg(v.x()).arg(v.y());
+    return QString::asprintf("QPointF(%g, %g)", v.x(), v.y());
 }
 
 qreal QQmlPointFValueType::x() const
@@ -307,7 +307,7 @@ void QQmlPointValueType::setY(int y)
 
 QString QQmlSizeFValueType::toString() const
 {
-    return QString(QLatin1String("QSizeF(%1, %2)")).arg(v.width()).arg(v.height());
+    return QString::asprintf("QSizeF(%g, %g)", v.width(), v.height());
 }
 
 qreal QQmlSizeFValueType::width() const
@@ -353,7 +353,7 @@ void QQmlSizeValueType::setHeight(int h)
 
 QString QQmlRectFValueType::toString() const
 {
-    return QString(QLatin1String("QRectF(%1, %2, %3, %4)")).arg(v.x()).arg(v.y()).arg(v.width()).arg(v.height());
+    return QString::asprintf("QRectF(%g, %g, %g, %g)", v.x(), v.y(), v.width(), v.height());
 }
 
 qreal QQmlRectFValueType::x() const
diff --git a/src/qml/qml/qqmlvaluetypewrapper.cpp b/src/qml/qml/qqmlvaluetypewrapper.cpp
index 3ad53aa3fc..c4008d2a05 100644
--- a/src/qml/qml/qqmlvaluetypewrapper.cpp
+++ b/src/qml/qml/qqmlvaluetypewrapper.cpp
@@ -332,7 +332,8 @@ ReturnedValue QQmlValueTypeWrapper::method_toString(CallContext *ctx)
     if (QMetaType::convert(w->d()->gadgetPtr, w->d()->valueType->typeId, &convertResult, QMetaType::QString)) {
         result = convertResult;
     } else {
-        result = QString::fromUtf8(QMetaType::typeName(w->d()->valueType->typeId)) + QLatin1Char('(');
+        result += QString::fromUtf8(QMetaType::typeName(w->d()->valueType->typeId))
+                + QLatin1Char('(');
         const QMetaObject *mo = w->d()->propertyCache->metaObject();
         const int propCount = mo->propertyCount();
         for (int i = 0; i < propCount; ++i) {
diff --git a/src/qml/qml/qqmlvmemetaobject.cpp b/src/qml/qml/qqmlvmemetaobject.cpp
index 81bc6846e6..47c125355b 100644
--- a/src/qml/qml/qqmlvmemetaobject.cpp
+++ b/src/qml/qml/qqmlvmemetaobject.cpp
@@ -932,10 +932,10 @@ int QQmlVMEMetaObject::metaCall(QObject *o, QMetaObject::Call c, int _id, void *
                     // are not rewritten correctly but this bug is deemed out-of-scope to fix for
                     // performance reasons; see QTBUG-24064) and thus compilation will have failed.
                     QQmlError e;
-                    e.setDescription(QString::fromLatin1("Exception occurred during compilation of "
-                                                         "function: %1")
-                                     .arg(QString::fromUtf8(QMetaObject::method(_id)
-                                                            .methodSignature())));
+                    e.setDescription(QLatin1String("Exception occurred during compilation of "
+                                                         "function: ")
+                                     + QString::fromUtf8(QMetaObject::method(_id)
+                                                         .methodSignature()));
                     ep->warning(e);
                     return -1; // The dynamic method with that id is not available.
                 }
diff --git a/src/qml/qml/qqmlxmlhttprequest.cpp b/src/qml/qml/qqmlxmlhttprequest.cpp
index 14c12c2542..58ffab9ec9 100644
--- a/src/qml/qml/qqmlxmlhttprequest.cpp
+++ b/src/qml/qml/qqmlxmlhttprequest.cpp
@@ -1162,8 +1162,8 @@ QString QQmlXMLHttpRequest::headers() const
     foreach (const HeaderPair &header, m_headersList) {
         if (ret.length())
             ret.append(QLatin1String("\r\n"));
-        ret = ret % QString::fromUtf8(header.first) % QLatin1String(": ")
-                % QString::fromUtf8(header.second);
+        ret += QString::fromUtf8(header.first) + QLatin1String(": ")
+             + QString::fromUtf8(header.second);
     }
     return ret;
 }
diff --git a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
index db0439ab9e..fd36f76d0e 100644
--- a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
+++ b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
@@ -1057,7 +1057,9 @@ ReturnedValue QtObject::method_createQmlObject(CallContext *ctx)
     struct Error {
         static ReturnedValue create(QV4::ExecutionEngine *v4, const QList<QQmlError> &errors) {
             Scope scope(v4);
-            QString errorstr = QLatin1String("Qt.createQmlObject(): failed to create object: ");
+            QString errorstr;
+            // '+=' reserves extra capacity. Follow-up appending will be probably free.
+            errorstr += QLatin1String("Qt.createQmlObject(): failed to create object: ");
 
             QV4::ScopedArrayObject qmlerrors(scope, v4->newArrayObject());
             QV4::ScopedObject qmlerror(scope);
@@ -1497,15 +1499,13 @@ static QV4::ReturnedValue writeToConsole(ConsoleLogTypes logType, CallContext *c
             result.append(QLatin1Char(' '));
 
         if (ctx->args()[i].as<ArrayObject>())
-            result.append(QLatin1Char('[') + ctx->args()[i].toQStringNoThrow() + QLatin1Char(']'));
+            result += QLatin1Char('[') + ctx->args()[i].toQStringNoThrow() + QLatin1Char(']');
         else
             result.append(ctx->args()[i].toQStringNoThrow());
     }
 
-    if (printStack) {
-        result.append(QLatin1Char('\n'));
-        result.append(jsStack(v4));
-    }
+    if (printStack)
+        result += QLatin1Char('\n') + jsStack(v4);
 
     static QLoggingCategory qmlLoggingCategory("qml");
     static QLoggingCategory jsLoggingCategory("js");