C++ QQmlEnginePrivate::referenceScarceResources方法代码示例

QVariant QQmlBinding::evaluate()
{
    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context()->engine);
    QV4::Scope scope(ep->v4engine());
    ep->referenceScarceResources();

    bool isUndefined = false;

    QV4::ScopedValue f(scope, v4function.value());
    QV4::ScopedValue result(scope, QQmlJavaScriptExpression::evaluate(context(), f, &isUndefined));

    ep->dereferenceScarceResources();

    return ep->v8engine()->toVariant(result, qMetaTypeId<QList<QObject*> >());
}

QVariant QQmlBinding::evaluate()
{
    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context()->engine);
    ep->referenceScarceResources();

    bool isUndefined = false;

    v8::HandleScope handle_scope;
    v8::Context::Scope scope(ep->v8engine()->context());
    v8::Local<v8::Value> result =
        QQmlJavaScriptExpression::evaluate(context(), v8function, &isUndefined);

    ep->dereferenceScarceResources();

    return ep->v8engine()->toVariant(result, qMetaTypeId<QList<QObject*> >());
}

// Parts of this function mirror code in QQmlExpressionPrivate::value() and v8value().
// Changes made here may need to be made there and vice versa.
void QQmlBoundSignalExpression::evaluate(void **a)
{
    Q_ASSERT (context() && engine());

    if (!expressionFunctionValid())
        return;

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(engine());
    QV4::Scope scope(ep->v4engine());

    ep->referenceScarceResources(); // "hold" scarce resources in memory during evaluation.

    QVarLengthArray<int, 9> dummy;
    //TODO: lookup via signal index rather than method index as an optimization
    int methodIndex = QMetaObjectPrivate::signal(m_target->metaObject(), m_index).methodIndex();
    int *argsTypes = QQmlMetaObject(m_target).methodParameterTypes(methodIndex, dummy, 0);
    int argCount = argsTypes ? *argsTypes : 0;

    QV4::ScopedCallData callData(scope, argCount);
    for (int ii = 0; ii < argCount; ++ii) {
        int type = argsTypes[ii + 1];
        //### ideally we would use metaTypeToJS, however it currently gives different results
        //    for several cases (such as QVariant type and QObject-derived types)
        //args[ii] = engine->metaTypeToJS(type, a[ii + 1]);
        if (type == QMetaType::QVariant) {
            callData->args[ii] = scope.engine->fromVariant(*((QVariant *)a[ii + 1]));
        } else if (type == QMetaType::Int) {
            //### optimization. Can go away if we switch to metaTypeToJS, or be expanded otherwise
            callData->args[ii] = QV4::Primitive::fromInt32(*reinterpret_cast<const int*>(a[ii + 1]));
        } else if (type == qMetaTypeId<QQmlV4Handle>()) {
            callData->args[ii] = *reinterpret_cast<QQmlV4Handle *>(a[ii + 1]);
        } else if (ep->isQObject(type)) {
            if (!*reinterpret_cast<void* const *>(a[ii + 1]))
                callData->args[ii] = QV4::Primitive::nullValue();
            else
                callData->args[ii] = QV4::QObjectWrapper::wrap(ep->v4engine(), *reinterpret_cast<QObject* const *>(a[ii + 1]));
        } else {
            callData->args[ii] = scope.engine->fromVariant(QVariant(type, a[ii + 1]));
        }
    }

    QQmlJavaScriptExpression::evaluate(callData, 0);

    ep->dereferenceScarceResources(); // "release" scarce resources if top-level expression evaluation is complete.
}

QVariant QQmlExpressionPrivate::value(bool *isUndefined)
{
    Q_Q(QQmlExpression);

    if (!context() || !context()->isValid()) {
        qWarning("QQmlExpression: Attempted to evaluate an expression in an invalid context");
        return QVariant();
    }

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(q->engine());
    QVariant rv;

    ep->referenceScarceResources(); // "hold" scarce resources in memory during evaluation.

    {
        QV4::Scope scope(QV8Engine::getV4(ep->v8engine()));
        QV4::ScopedValue result(scope, v4value(isUndefined));
        rv = ep->v8engine()->toVariant(result, -1);
    }

    ep->dereferenceScarceResources(); // "release" scarce resources if top-level expression evaluation is complete.

    return rv;
}

// Parts of this function mirror code in QQmlExpressionPrivate::value() and v8value().
// Changes made here may need to be made there and vice versa.
void QQmlBoundSignalExpression::evaluate(void **a)
{
    Q_ASSERT (context() && engine());

    if (invalidParameterName())
        return;

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(engine());
    QV4::Scope scope(ep->v4engine());

    ep->referenceScarceResources(); // "hold" scarce resources in memory during evaluation.
    {
        if (!expressionFunctionValid()) {
            Q_ASSERT(!m_extra.isNull());
            QString expression;

            // 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.
            expression.fill(QChar(QChar::Space), qMax(m_extra->m_sourceLocation.column, (quint16)2) - 2);
            expression += QStringLiteral("(function ");
            expression += m_extra->m_handlerName;
            expression += QLatin1Char('(');

            if (m_extra->m_parameterString.isEmpty()) {
                QString error;
                //TODO: look at using the property cache here (as in the compiler)
                //      for further optimization
                QMetaMethod signal = QMetaObjectPrivate::signal(m_target->metaObject(), m_index);
                expression += QQmlPropertyCache::signalParameterStringForJS(engine(), signal.parameterNames(), &error);

                if (!error.isEmpty()) {
                    qmlInfo(scopeObject()) << error;
                    setInvalidParameterName(true);
                    ep->dereferenceScarceResources();
                    return;
                }
            } else
                expression += m_extra->m_parameterString;

            expression += QStringLiteral(") { ");
            expression += m_extra->m_expression;
            expression += QStringLiteral(" })");

            m_extra->m_expression.clear();
            m_extra->m_handlerName.clear();
            m_extra->m_parameterString.clear();

            m_v8function = evalFunction(context(), scopeObject(), expression,
                                        m_extra->m_sourceLocation.sourceFile, m_extra->m_sourceLocation.line, &m_extra->m_v8qmlscope);

            if (m_v8function.isNullOrUndefined()) {
                ep->dereferenceScarceResources();
                return; // could not evaluate function.  Not valid.
            }

            setExpressionFunctionValid(true);
        }

        QV8Engine *engine = ep->v8engine();
        QVarLengthArray<int, 9> dummy;
        //TODO: lookup via signal index rather than method index as an optimization
        int methodIndex = QMetaObjectPrivate::signal(m_target->metaObject(), m_index).methodIndex();
        int *argsTypes = QQmlPropertyCache::methodParameterTypes(m_target, methodIndex, dummy, 0);
        int argCount = argsTypes ? *argsTypes : 0;

        QV4::ScopedValue f(scope, m_v8function.value());
        QV4::ScopedCallData callData(scope, argCount);
        for (int ii = 0; ii < argCount; ++ii) {
            int type = argsTypes[ii + 1];
            //### ideally we would use metaTypeToJS, however it currently gives different results
            //    for several cases (such as QVariant type and QObject-derived types)
            //args[ii] = engine->metaTypeToJS(type, a[ii + 1]);
            if (type == QMetaType::QVariant) {
                callData->args[ii] = engine->fromVariant(*((QVariant *)a[ii + 1]));
            } else if (type == QMetaType::Int) {
                //### optimization. Can go away if we switch to metaTypeToJS, or be expanded otherwise
                callData->args[ii] = QV4::Primitive::fromInt32(*reinterpret_cast<const int*>(a[ii + 1]));
            } else if (type == qMetaTypeId<QQmlV4Handle>()) {
                callData->args[ii] = *reinterpret_cast<QQmlV4Handle *>(a[ii + 1]);
            } else if (ep->isQObject(type)) {
                if (!*reinterpret_cast<void* const *>(a[ii + 1]))
                    callData->args[ii] = QV4::Primitive::nullValue();
                else
                    callData->args[ii] = QV4::QObjectWrapper::wrap(ep->v4engine(), *reinterpret_cast<QObject* const *>(a[ii + 1]));
            } else {
                callData->args[ii] = engine->fromVariant(QVariant(type, a[ii + 1]));
            }
        }

        QQmlJavaScriptExpression::evaluate(context(), f, callData, 0);
    }
    ep->dereferenceScarceResources(); // "release" scarce resources if top-level expression evaluation is complete.
}

void QQmlBinding::update(QQmlPropertyPrivate::WriteFlags flags)
{
    if (!enabledFlag() || !context() || !context()->isValid())
        return;

    // Check that the target has not been deleted
    if (QQmlData::wasDeleted(object()))
        return;

    QString url;
    quint16 lineNumber;
    quint16 columnNumber;

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context()->engine);
    QV4::Scope scope(ep->v4engine());
    QV4::ScopedFunctionObject f(scope, v4function.value());
    Q_ASSERT(f);
    if (f->bindingKeyFlag()) {
        Q_ASSERT(f->as<QV4::QQmlBindingFunction>());
        QQmlSourceLocation loc = static_cast<QV4::QQmlBindingFunction *>(f.getPointer())->d()->bindingLocation;
        url = loc.sourceFile;
        lineNumber = loc.line;
        columnNumber = loc.column;
    } else {
        QV4::Function *function = f->asFunctionObject()->function();
        Q_ASSERT(function);

        url = function->sourceFile();
        lineNumber = function->compiledFunction->location.line;
        columnNumber = function->compiledFunction->location.column;
    }

    int lineNo = qmlSourceCoordinate(lineNumber);
    int columnNo = qmlSourceCoordinate(columnNumber);

    QQmlTrace trace("General Binding Update");
    trace.addDetail("URL", url);
    trace.addDetail("Line", lineNo);
    trace.addDetail("Column", columnNo);

    if (!updatingFlag()) {
        QQmlBindingProfiler prof(ep->profiler, url, lineNo, columnNo);
        setUpdatingFlag(true);

        QQmlAbstractExpression::DeleteWatcher watcher(this);

        if (m_core.propType == qMetaTypeId<QQmlBinding *>()) {

            int idx = m_core.coreIndex;
            Q_ASSERT(idx != -1);

            QQmlBinding *t = this;
            int status = -1;
            void *a[] = { &t, 0, &status, &flags };
            QMetaObject::metacall(*m_coreObject, QMetaObject::WriteProperty, idx, a);

        } else {
            ep->referenceScarceResources();

            bool isUndefined = false;

            QV4::ScopedValue result(scope, QQmlJavaScriptExpression::evaluate(context(), f, &isUndefined));

            trace.event("writing binding result");

            bool needsErrorLocationData = false;
            if (!watcher.wasDeleted() && !hasError())
                needsErrorLocationData = !QQmlPropertyPrivate::writeBinding(*m_coreObject, m_core, context(),
                                                                    this, result, isUndefined, flags);

            if (!watcher.wasDeleted()) {

                if (needsErrorLocationData)
                    delayedError()->setErrorLocation(QUrl(url), lineNumber, columnNumber);

                if (hasError()) {
                    if (!delayedError()->addError(ep)) ep->warning(this->error(context()->engine));
                } else {
                    clearError();
                }

            }

            ep->dereferenceScarceResources();
        }

        if (!watcher.wasDeleted())
            setUpdatingFlag(false);
    } else {
        QQmlProperty p = property();
        QQmlAbstractBinding::printBindingLoopError(p);
    }
}

void QQmlBinding::update(QQmlPropertyPrivate::WriteFlags flags)
{
    if (!enabledFlag() || !context() || !context()->isValid())
        return;

    // Check that the target has not been deleted
    if (QQmlData::wasDeleted(object()))
        return;

    int lineNo = qmlSourceCoordinate(m_lineNumber);
    int columnNo = qmlSourceCoordinate(m_columnNumber);

    QQmlTrace trace("General Binding Update");
    trace.addDetail("URL", m_url);
    trace.addDetail("Line", lineNo);
    trace.addDetail("Column", columnNo);

    if (!updatingFlag()) {
        QQmlBindingProfiler prof(m_url, lineNo, columnNo, QQmlProfilerService::QmlBinding);
        setUpdatingFlag(true);

        QQmlAbstractExpression::DeleteWatcher watcher(this);

        if (m_core.propType == qMetaTypeId<QQmlBinding *>()) {

            int idx = m_core.coreIndex;
            Q_ASSERT(idx != -1);

            QQmlBinding *t = this;
            int status = -1;
            void *a[] = { &t, 0, &status, &flags };
            QMetaObject::metacall(*m_coreObject, QMetaObject::WriteProperty, idx, a);

        } else {
            QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context()->engine);
            ep->referenceScarceResources();

            bool isUndefined = false;

            v8::HandleScope handle_scope;
            v8::Context::Scope scope(ep->v8engine()->context());
            v8::Local<v8::Value> result =
                QQmlJavaScriptExpression::evaluate(context(), v8function, &isUndefined);

            trace.event("writing binding result");

            bool needsErrorLocationData = false;
            if (!watcher.wasDeleted() && !hasError())
                needsErrorLocationData = !QQmlPropertyPrivate::writeBinding(*m_coreObject, m_core, context(),
                                                                    this, result, isUndefined, flags);

            if (!watcher.wasDeleted()) {

                if (needsErrorLocationData)
                    delayedError()->setErrorLocation(QUrl(m_url), m_lineNumber, m_columnNumber);

                if (hasError()) {
                    if (!delayedError()->addError(ep)) ep->warning(this->error(context()->engine));
                } else {
                    clearError();
                }

            }

            ep->dereferenceScarceResources();
        }

        if (!watcher.wasDeleted())
            setUpdatingFlag(false);
    } else {
        QQmlProperty p = property();
        QQmlAbstractBinding::printBindingLoopError(p);
    }
}

void QQmlIncubatorPrivate::incubate(QQmlInstantiationInterrupt &i)
{
    if (!compiledData)
        return;

    QML_MEMORY_SCOPE_URL(compiledData->url());

    QExplicitlySharedDataPointer<QQmlIncubatorPrivate> protectThis(this);

    QRecursionWatcher<QQmlIncubatorPrivate, &QQmlIncubatorPrivate::recursion> watcher(this);

    QQmlEngine *engine = compiledData->engine;
    QQmlEnginePrivate *enginePriv = QQmlEnginePrivate::get(engine);

    if (!vmeGuard.isOK()) {
        QQmlError error;
        error.setUrl(compiledData->url());
        error.setDescription(QQmlComponent::tr("Object destroyed during incubation"));
        errors << error;
        progress = QQmlIncubatorPrivate::Completed;

        goto finishIncubate;
    }

    vmeGuard.clear();

    if (progress == QQmlIncubatorPrivate::Execute) {
        enginePriv->referenceScarceResources();
        QObject *tresult = 0;
        tresult = creator->create(subComponentToCreate, /*parent*/0, &i);
        if (!tresult)
            errors = creator->errors;
        enginePriv->dereferenceScarceResources();

        if (watcher.hasRecursed())
            return;

        result = tresult;
        if (errors.isEmpty() && result == 0)
            goto finishIncubate;

        if (result) {
            QQmlData *ddata = QQmlData::get(result);
            Q_ASSERT(ddata);
            //see QQmlComponent::beginCreate for explanation of indestructible
            ddata->indestructible = true;
            ddata->explicitIndestructibleSet = true;
            ddata->rootObjectInCreation = false;
            if (q)
                q->setInitialState(result);
        }

        if (watcher.hasRecursed())
            return;

        if (errors.isEmpty())
            progress = QQmlIncubatorPrivate::Completing;
        else
            progress = QQmlIncubatorPrivate::Completed;

        changeStatus(calculateStatus());

        if (watcher.hasRecursed())
            return;

        if (i.shouldInterrupt())
            goto finishIncubate;
    }

    if (progress == QQmlIncubatorPrivate::Completing) {
        do {
            if (watcher.hasRecursed())
                return;

            QQmlContextData *ctxt = 0;
            ctxt = creator->finalize(i);
            if (ctxt) {
                rootContext = ctxt;
                progress = QQmlIncubatorPrivate::Completed;
                goto finishIncubate;
            }
        } while (!i.shouldInterrupt());
    }

finishIncubate:
    if (progress == QQmlIncubatorPrivate::Completed && waitingFor.isEmpty()) {
        QExplicitlySharedDataPointer<QQmlIncubatorPrivate> isWaiting = waitingOnMe;
        clear();

        if (isWaiting) {
            QRecursionWatcher<QQmlIncubatorPrivate, &QQmlIncubatorPrivate::recursion> watcher(isWaiting.data());
            changeStatus(calculateStatus());
            if (!watcher.hasRecursed())
                isWaiting->incubate(i);
        } else {
            changeStatus(calculateStatus());
        }

        enginePriv->inProgressCreations--;

//.........这里部分代码省略.........

// Parts of this function mirror code in QQmlExpressionPrivate::value() and v8value().
// Changes made here may need to be made there and vice versa.
void QQmlBoundSignalExpression::evaluate(void **a)
{
    Q_ASSERT (context() && engine());

    if (m_invalidParameterName)
        return;

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(engine());

    ep->referenceScarceResources(); // "hold" scarce resources in memory during evaluation.
    {
        v8::HandleScope handle_scope;
        v8::Context::Scope context_scope(ep->v8engine()->context());
        if (!m_expressionFunctionValid) {

            //TODO: look at using the property cache here (as in the compiler)
            //      for further optimization
            QMetaMethod signal = QMetaObjectPrivate::signal(m_target->metaObject(), m_index);
            QQmlRewrite::RewriteSignalHandler rewriter;

            QString expression;
            bool ok = true;

            if (m_expressionFunctionRewritten) {
                expression = QString::fromUtf8(m_expressionUtf8);

                //if we need parameters, and the rewrite doesn't include them,
                //create and insert the parameter string now
                if (m_parameterCountForJS == -1 && signal.parameterCount()) {
                    const QString &parameters = rewriter.createParameterString(signal.parameterNames(),
                                                ep->v8engine()->illegalNames());
                    int index = expression.indexOf(QLatin1Char('('), 1);
                    Q_ASSERT(index > -1);
                    expression.insert(index + 1, parameters);

                    setParameterCountForJS(rewriter.parameterCountForJS());
                }

                m_expressionUtf8.clear();
            } else {
                //expression is still in its original form, so perform a full rewrite
                expression = rewriter(m_expression, QString()/*no name hint available*/, &ok,
                                      signal.parameterNames(),
                                      ep->v8engine()->illegalNames());
                setParameterCountForJS(rewriter.parameterCountForJS());
                m_expression.clear();
            }

            if (rewriter.hasParameterError()) {
                qmlInfo(scopeObject()) << rewriter.parameterError();
                m_invalidParameterName = true;
                ep->dereferenceScarceResources();
                return;
            }

            if (ok) {
                m_v8function = evalFunction(context(), scopeObject(), expression,
                                            m_fileName, m_line, &m_v8qmlscope);
            }

            if (m_v8function.IsEmpty() || m_v8function->IsNull()) {
                ep->dereferenceScarceResources();
                return; // could not evaluate function.  Not valid.
            }

            setUseSharedContext(false);
            m_expressionFunctionValid = true;
        }

        if (!hasParameterInfo()) {
            QQmlJavaScriptExpression::evaluate(context(), m_v8function, 0);
        } else {
            QV8Engine *engine = ep->v8engine();
            QVarLengthArray<int, 9> dummy;
            //TODO: lookup via signal index rather than method index as an optimization
            int methodIndex = QMetaObjectPrivate::signal(m_target->metaObject(), m_index).methodIndex();
            int *argsTypes = QQmlPropertyCache::methodParameterTypes(m_target, methodIndex, dummy, 0);
            int argCount = argsTypes ? m_parameterCountForJS : 0;

            QVarLengthArray<v8::Handle<v8::Value>, 9> args(argCount);

            for (int ii = 0; ii < argCount; ++ii) {
                int type = argsTypes[ii + 1];
                //### ideally we would use metaTypeToJS, however it currently gives different results
                //    for several cases (such as QVariant type and QObject-derived types)
                //args[ii] = engine->metaTypeToJS(type, a[ii + 1]);
                if (type == QMetaType::QVariant) {
                    args[ii] = engine->fromVariant(*((QVariant *)a[ii + 1]));
                } else if (type == QMetaType::Int) {
                    //### optimization. Can go away if we switch to metaTypeToJS, or be expanded otherwise
                    args[ii] = v8::Integer::New(*reinterpret_cast<const int*>(a[ii + 1]));
                } else if (type == qMetaTypeId<QQmlV8Handle>()) {
                    args[ii] = reinterpret_cast<QQmlV8Handle *>(a[ii + 1])->toHandle();
                } else if (ep->isQObject(type)) {
                    if (!*reinterpret_cast<void* const *>(a[ii + 1]))
                        args[ii] = v8::Null();
                    else
                        args[ii] = engine->newQObject(*reinterpret_cast<QObject* const *>(a[ii + 1]));
//.........这里部分代码省略.........

//.........这里部分代码省略.........
                    int flags = *reinterpret_cast<int*>(a[3]);
                    if (flags & QQmlPropertyPrivate::RemoveBindingOnAliasWrite) {
                        QQmlData *targetData = QQmlData::get(target);
                        if (targetData && targetData->hasBindingBit(d->propertyIndex())) {
                            QQmlAbstractBinding *binding = QQmlPropertyPrivate::setBinding(target, d->propertyIndex(), d->isValueTypeAlias()?d->valueTypeIndex():-1, 0);
                            if (binding) binding->destroy();
                        }
                    }
                }

                if (d->isValueTypeAlias()) {
                    // Value type property
                    QQmlValueType *valueType = QQmlValueTypeFactory::valueType(d->valueType());
                    Q_ASSERT(valueType);

                    valueType->read(target, d->propertyIndex());
                    int rv = QMetaObject::metacall(valueType, c, d->valueTypeIndex(), a);

                    if (c == QMetaObject::WriteProperty)
                        valueType->write(target, d->propertyIndex(), 0x00);

                    return rv;

                } else {
                    return QMetaObject::metacall(target, c, d->propertyIndex(), a);
                }

            }
            return -1;

        }

    } else if(c == QMetaObject::InvokeMetaMethod) {

        if (id >= methodOffset()) {

            id -= methodOffset();
            int plainSignals = metaData->signalCount + metaData->propertyCount +
                               metaData->aliasCount;
            if (id < plainSignals) {
                activate(object, _id, a);
                return -1;
            }

            id -= plainSignals;

            if (id < metaData->methodCount) {
                if (!ctxt->engine)
                    return -1; // We can't run the method

                QQmlEnginePrivate *ep = QQmlEnginePrivate::get(ctxt->engine);
                ep->referenceScarceResources(); // "hold" scarce resources in memory during evaluation.
                QV4::Scope scope(ep->v4engine());


                QV4::Scoped<QV4::FunctionObject> function(scope, method(id));
                if (!function) {
                    // The function was not compiled.  There are some exceptional cases which the
                    // expression rewriter does not rewrite properly (e.g., \r-terminated lines
                    // 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(QLatin1String("Exception occurred during compilation of function: %1")).
                                     arg(QLatin1String(QMetaObject::method(_id).methodSignature().constData())));
                    ep->warning(e);
                    return -1; // The dynamic method with that id is not available.
                }

                QQmlVMEMetaData::MethodData *data = metaData->methodData() + id;

                QV4::ScopedCallData callData(scope, data->parameterCount);
                callData->thisObject = ep->v8engine()->global();

                for (int ii = 0; ii < data->parameterCount; ++ii)
                    callData->args[ii] = ep->v8engine()->fromVariant(*(QVariant *)a[ii + 1]);

                QV4::ScopedValue result(scope);
                QV4::ExecutionContext *ctx = function->engine()->currentContext();
                result = function->call(callData);
                if (scope.hasException()) {
                    QQmlError error = QV4::ExecutionEngine::catchExceptionAsQmlError(ctx);
                    if (error.isValid())
                        ep->warning(error);
                    if (a[0]) *(QVariant *)a[0] = QVariant();
                } else {
                    if (a[0]) *(QVariant *)a[0] = ep->v8engine()->toVariant(result, 0);
                }

                ep->dereferenceScarceResources(); // "release" scarce resources if top-level expression evaluation is complete.
                return -1;
            }
            return -1;
        }
    }

    if (parent.isT1())
        return parent.asT1()->metaCall(object, c, _id, a);
    else
        return object->qt_metacall(c, _id, a);
}