C++ QQmlEnginePrivate类代码示例

QV4::ReturnedValue QQmlJavaScriptExpression::evaluate(QQmlContextData *context,
                                   const QV4::ValueRef function,
                                   QV4::CallData *callData,
                                   bool *isUndefined)
{
    Q_ASSERT(context && context->engine);

    if (function->isUndefined()) {
        if (isUndefined)
            *isUndefined = true;
        return QV4::Encode::undefined();
    }

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context->engine);

    // All code that follows must check with watcher before it accesses data members
    // incase we have been deleted.
    DeleteWatcher watcher(this);

    Q_ASSERT(notifyOnValueChanged() || activeGuards.isEmpty());
    GuardCapture capture(context->engine, this, &watcher);

    QQmlEnginePrivate::PropertyCapture *lastPropertyCapture = ep->propertyCapture;
    ep->propertyCapture = notifyOnValueChanged()?&capture:0;


    if (notifyOnValueChanged())
        capture.guards.copyAndClearPrepend(activeGuards);

    QV4::ExecutionEngine *v4 = QV8Engine::getV4(ep->v8engine());
    QV4::Scope scope(v4);
    QV4::ScopedValue result(scope, QV4::Primitive::undefinedValue());
    QV4::ExecutionContext *ctx = v4->currentContext();
    callData->thisObject = v4->globalObject;
    if (scopeObject()) {
        QV4::ScopedValue value(scope, QV4::QObjectWrapper::wrap(ctx->d()->engine, scopeObject()));
        if (value->isObject())
            callData->thisObject = value;
    }

    result = function->asFunctionObject()->call(callData);
    if (scope.hasException()) {
        if (watcher.wasDeleted())
            ctx->catchException(); // ignore exception
        else
            delayedError()->catchJavaScriptException(ctx);
        if (isUndefined)
            *isUndefined = true;
    } else {
        if (isUndefined)
            *isUndefined = result->isUndefined();

        if (!watcher.wasDeleted() && hasDelayedError())
            delayedError()->clearError();
    }

    if (capture.errorString) {
        for (int ii = 0; ii < capture.errorString->count(); ++ii)
            qWarning("%s", qPrintable(capture.errorString->at(ii)));
        delete capture.errorString;
        capture.errorString = 0;
    }

    while (Guard *g = capture.guards.takeFirst())
        g->Delete();

    ep->propertyCapture = lastPropertyCapture;

    return result.asReturnedValue();
}

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);
    }
}

// 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;

    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 QQuickAnimationController::classBegin()
{
    QQmlEnginePrivate *engPriv = QQmlEnginePrivate::get(qmlEngine(this));
    engPriv->registerFinalizeCallback(this, this->metaObject()->indexOfSlot("componentFinalized()"));
}

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.........

v8::Handle<v8::Value> QV8ContextWrapper::Getter(v8::Local<v8::String> property, 
                                                const v8::AccessorInfo &info)
{
    QV8ContextResource *resource = v8_resource_check<QV8ContextResource>(info.This());

    // Its possible we could delay the calculation of the "actual" context (in the case
    // of sub contexts) until it is definately needed.
    QQmlContextData *context = resource->getContext();
    QQmlContextData *expressionContext = context;

    if (!context)
        return v8::Undefined();

    if (v8::Context::GetCallingQmlGlobal() != info.This())
        return v8::Handle<v8::Value>();

    // Search type (attached property/enum/imported scripts) names
    // while (context) {
    //     Search context properties
    //     Search scope object
    //     Search context object
    //     context = context->parent
    // }

    QV8Engine *engine = resource->engine;

    QObject *scopeObject = resource->getScopeObject();

    QHashedV8String propertystring(property);

    if (context->imports && QV8Engine::startsWithUpper(property)) {
        // Search for attached properties, enums and imported scripts
        QQmlTypeNameCache::Result r = context->imports->query(propertystring);
        
        if (r.isValid()) { 
            if (r.scriptIndex != -1) {
                int index = r.scriptIndex;
                if (index < context->importedScripts.count())
                    return context->importedScripts.at(index);
                else
                    return v8::Undefined();
            } else if (r.type) {
                return engine->typeWrapper()->newObject(scopeObject, r.type);
            } else if (r.importNamespace) {
                return engine->typeWrapper()->newObject(scopeObject, context->imports, r.importNamespace);
            }
            Q_ASSERT(!"Unreachable");
        }

        // Fall through
    }

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(engine->engine());
    QV8QObjectWrapper *qobjectWrapper = engine->qobjectWrapper();

    while (context) {
        // Search context properties
        if (context->propertyNames) {
            int propertyIdx = context->propertyNames->value(propertystring);

            if (propertyIdx != -1) {

                if (propertyIdx < context->idValueCount) {

                    ep->captureProperty(&context->idValues[propertyIdx].bindings);
                    return engine->newQObject(context->idValues[propertyIdx]);
                } else {

                    QQmlContextPrivate *cp = context->asQQmlContextPrivate();

                    ep->captureProperty(context->asQQmlContext(), -1,
                                        propertyIdx + cp->notifyIndex);

                    const QVariant &value = cp->propertyValues.at(propertyIdx);
                    if (value.userType() == qMetaTypeId<QList<QObject*> >()) {
                        QQmlListProperty<QObject> prop(context->asQQmlContext(), (void*) qintptr(propertyIdx),
                                                               QQmlContextPrivate::context_count,
                                                               QQmlContextPrivate::context_at);
                        return engine->listWrapper()->newList(prop, qMetaTypeId<QQmlListProperty<QObject> >());
                    } else {
                        return engine->fromVariant(cp->propertyValues.at(propertyIdx));
                    }
                }
            }
        }

        // Search scope object
        if (scopeObject) {
            v8::Handle<v8::Value> result = qobjectWrapper->getProperty(scopeObject, propertystring,
                                                                       context, QV8QObjectWrapper::CheckRevision);
            if (!result.IsEmpty()) return result;
        }
        scopeObject = 0;


        // Search context object
        if (context->contextObject) {
            v8::Handle<v8::Value> result = qobjectWrapper->getProperty(context->contextObject, propertystring,
                                                                       context, QV8QObjectWrapper::CheckRevision);
            if (!result.IsEmpty()) return result;
//.........这里部分代码省略.........

//.........这里部分代码省略.........
        if (lastDotIndex != -1) {
            enclosingNamespace = qualifier.left(lastDotIndex);
            qualifier = qualifier.mid(lastDotIndex+1);
        }

        compiledData->importCache->add(qualifier, scriptIndex, enclosingNamespace);
#if 0
        QQmlScriptData *scriptData = script.script->scriptData();
        scriptData->addref();
        compiledData->scripts << scriptData;
#endif
    }

    // resolve component boundaries and aliases
    if (!resolveComponentBoundariesAndAliases())
        return false;

    // Compile JS binding expressions and signal handlers
    if (!compilation->document->javaScriptCompilationUnit) {
        // We can compile script strings ahead of time, but they must be compiled
        // without type optimizations as their scope is always entirely dynamic.
        scanScriptStrings();

        // TBD: check how it uses importCache
        // TBD: check how links with other scripts
        QmlIR::JSCodeGen v4CodeGenerator(compilation->urlString, compilation->document->code, &compilation->document->jsModule,
                                         &compilation->document->jsParserEngine, compilation->document->program,
                                         compiledData->importCache, &compilation->document->jsGenerator.stringTable);
        JSCodeGenerator jsCodeGen(this, &v4CodeGenerator);
        if (!jsCodeGen.generateCodeForComponents())
            return false;

        simplifyJavaScriptBindingExpressions();

        QQmlEnginePrivate *enginePrivate = QQmlEnginePrivate::get(compilation->engine);
        QV4::ExecutionEngine *v4 = enginePrivate->v4engine();
        // TBD: store unlinked binaries
#if 0
        QScopedPointer<QV4::EvalInstructionSelection> isel(
                    v4->iselFactory->create(enginePrivate, v4->executableAllocator,
                                            &compilation->document->jsModule, &compilation->document->jsGenerator));
#endif
        QScopedPointer<QmcInstructionSelection> isel(
                    new QmcInstructionSelection(enginePrivate, v4->executableAllocator,
                                            &compilation->document->jsModule, &compilation->document->jsGenerator));
        isel->setUseFastLookups(false);
        compilation->document->javaScriptCompilationUnit = isel->compile(/*generated unit data*/false);
        compilation->linkData = isel->linkData();
        compilation->exceptionReturnLabels = isel->exceptionReturnLabelsData();
        compilation->exceptionPropagationJumps = isel->exceptionPropagationJumpsData();
#if CPU(ARM_THUMB2)
        compilation->jumpsToLinkData = isel->linkRecordData();
        compilation->unlinkedCodeData = isel->unlinkedCodeData();
#endif
    }

    // Generate QML compiled type data structures

    QmlIR::QmlUnitGenerator qmlGenerator;
    QV4::CompiledData::QmlUnit *qmlUnit = qmlGenerator.generate(*compilation->document);

    Q_ASSERT(compilation->document->javaScriptCompilationUnit);
    Q_ASSERT((void*)qmlUnit == (void*)&qmlUnit->header);
    // The js unit owns the data and will free the qml unit.
    compilation->document->javaScriptCompilationUnit->data = &qmlUnit->header;

    compiledData->compilationUnit = compilation->document->javaScriptCompilationUnit;
    if (compiledData->compilationUnit)
        compiledData->compilationUnit->ref();
    compiledData->qmlUnit = qmlUnit; // ownership transferred to m_compiledData

    // add to type registry
    // qqmltypecompiler.cpp:248
    if (compiledData->isCompositeType()) {
        if (compilation->singleton)
            qmlUnit->header.flags |= QV4::CompiledData::Unit::IsSingleton;
        QQmlEnginePrivate::get(compilation->engine)->registerInternalCompositeType(compiledData);
    } else {
        if (compilation->singleton) {
             qmlUnit->header.flags = qmlUnit->header.flags | QV4::CompiledData::Unit::IsSingleton;
        }

        const QV4::CompiledData::Object *obj = qmlUnit->objectAt(qmlUnit->indexOfRootObject);
        QQmlCompiledData::TypeReference *typeRef = compiledData->resolvedTypes.value(obj->inheritedTypeNameIndex);
        Q_ASSERT(typeRef);
        if (typeRef->component) {
            compiledData->metaTypeId = typeRef->component->metaTypeId;
            compiledData->listMetaTypeId = typeRef->component->listMetaTypeId;
        } else {
            compiledData->metaTypeId = typeRef->type->typeId();
            compiledData->listMetaTypeId = typeRef->type->qListTypeId();
        }
    }

    // Sanity check property bindings and compile custom parsers
    if (!validateProperties())
        return false;

    return true;
}

// 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.........

int QQmlVMEMetaObject::metaCall(QMetaObject::Call c, int _id, void **a)
{
    int id = _id;
    if (c == QMetaObject::WriteProperty && interceptors &&
       !(*reinterpret_cast<int*>(a[3]) & QQmlPropertyPrivate::BypassInterceptor)) {

        for (QQmlPropertyValueInterceptor *vi = interceptors; vi; vi = vi->m_next) {
            if (vi->m_coreIndex != id)
                continue;

            int valueIndex = vi->m_valueTypeCoreIndex;
            int type = QQmlData::get(object)->propertyCache->property(id)->propType;

            if (type != QVariant::Invalid) {
                if (valueIndex != -1) {
                    QQmlValueType *valueType = QQmlValueTypeFactory::valueType(type);
                    Q_ASSERT(valueType);

                    //
                    // Consider the following case:
                    //  color c = { 0.1, 0.2, 0.3 }
                    //  interceptor exists on c.r
                    //  write { 0.2, 0.4, 0.6 }
                    //
                    // The interceptor may choose not to update the r component at this
                    // point (for example, a behavior that creates an animation). But we
                    // need to ensure that the g and b components are updated correctly.
                    //
                    // So we need to perform a full write where the value type is:
                    //    r = old value, g = new value, b = new value
                    //
                    // And then call the interceptor which may or may not write the
                    // new value to the r component.
                    //
                    // This will ensure that the other components don't contain stale data
                    // and any relevant signals are emitted.
                    //
                    // To achieve this:
                    //   (1) Store the new value type as a whole (needed due to
                    //       aliasing between a[0] and static storage in value type).
                    //   (2) Read the entire existing value type from object -> valueType temp.
                    //   (3) Read the previous value of the component being changed
                    //       from the valueType temp.
                    //   (4) Write the entire new value type into the temp.
                    //   (5) Overwrite the component being changed with the old value.
                    //   (6) Perform a full write to the value type (which may emit signals etc).
                    //   (7) Issue the interceptor call with the new component value.
                    //

                    QMetaProperty valueProp = valueType->metaObject()->property(valueIndex);
                    QVariant newValue(type, a[0]);

                    valueType->read(object, id);
                    QVariant prevComponentValue = valueProp.read(valueType);

                    valueType->setValue(newValue);
                    QVariant newComponentValue = valueProp.read(valueType);

                    // Don't apply the interceptor if the intercepted value has not changed
                    bool updated = false;
                    if (newComponentValue != prevComponentValue) {
                        valueProp.write(valueType, prevComponentValue);
                        valueType->write(object, id, QQmlPropertyPrivate::DontRemoveBinding | QQmlPropertyPrivate::BypassInterceptor);

                        vi->write(newComponentValue);
                        updated = true;
                    }

                    if (updated)
                        return -1;
                } else {
                    vi->write(QVariant(type, a[0]));
                    return -1;
                }
            }
        }
    }
    if (c == QMetaObject::ReadProperty || c == QMetaObject::WriteProperty || c == QMetaObject::ResetProperty) {
        if (id >= propOffset()) {
            id -= propOffset();

            if (id < metaData->propertyCount) {
               int t = (metaData->propertyData() + id)->propertyType;
                bool needActivate = false;

                if (id >= firstVarPropertyIndex) {
                    Q_ASSERT(t == QMetaType::QVariant);
                    // the context can be null if accessing var properties from cpp after re-parenting an item.
                    QQmlEnginePrivate *ep = (ctxt == 0 || ctxt->engine == 0) ? 0 : QQmlEnginePrivate::get(ctxt->engine);
                    QV8Engine *v8e = (ep == 0) ? 0 : ep->v8engine();
                    if (v8e) {
                        if (c == QMetaObject::ReadProperty) {
                            *reinterpret_cast<QVariant *>(a[0]) = readPropertyAsVariant(id);
                        } else if (c == QMetaObject::WriteProperty) {
                            writeProperty(id, *reinterpret_cast<QVariant *>(a[0]));
                        }
                    } else if (c == QMetaObject::ReadProperty) {
                        // if the context was disposed, we just return an invalid variant from read.
                        *reinterpret_cast<QVariant *>(a[0]) = QVariant();
                    }
//.........这里部分代码省略.........

void QQmlVMEMetaObject::ensureQObjectWrapper()
{
    QQmlEnginePrivate *ep = (ctxt == 0 || ctxt->engine == 0) ? 0 : QQmlEnginePrivate::get(ctxt->engine);
    QV4::ExecutionEngine *v4 = (ep == 0) ? 0 : ep->v4engine();
    QV4::QObjectWrapper::wrap(v4, object);
}

v8::Local<v8::Value>
QQmlJavaScriptExpression::evaluate(QQmlContextData *context,
                                   v8::Handle<v8::Function> function,
                                   int argc, v8::Handle<v8::Value> args[],
                                   bool *isUndefined)
{
    Q_ASSERT(context && context->engine);

    if (function.IsEmpty() || function->IsUndefined()) {
        if (isUndefined) *isUndefined = true;
        return v8::Local<v8::Value>();
    }

    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(context->engine);

    Q_ASSERT(notifyOnValueChanged() || activeGuards.isEmpty());
    GuardCapture capture(context->engine, this);

    QQmlEnginePrivate::PropertyCapture *lastPropertyCapture = ep->propertyCapture;
    ep->propertyCapture = notifyOnValueChanged()?&capture:0;


    if (notifyOnValueChanged())
        capture.guards.copyAndClearPrepend(activeGuards);

    QQmlContextData *lastSharedContext = 0;
    QObject *lastSharedScope = 0;

    bool sharedContext = useSharedContext();

    // All code that follows must check with watcher before it accesses data members
    // incase we have been deleted.
    DeleteWatcher watcher(this);

    if (sharedContext) {
        lastSharedContext = ep->sharedContext;
        lastSharedScope = ep->sharedScope;
        ep->sharedContext = context;
        ep->sharedScope = scopeObject();
    }

    v8::Local<v8::Value> result;
    {
        v8::TryCatch try_catch;
        v8::Handle<v8::Object> This = ep->v8engine()->global();
        if (scopeObject() && requiresThisObject()) {
            v8::Handle<v8::Value> value = ep->v8engine()->newQObject(scopeObject());
            if (value->IsObject()) This = v8::Handle<v8::Object>::Cast(value);
        }

        result = function->Call(This, argc, args);

        if (isUndefined)
            *isUndefined = try_catch.HasCaught() || result->IsUndefined();

        if (watcher.wasDeleted()) {
        } else if (try_catch.HasCaught()) {
            v8::Context::Scope scope(ep->v8engine()->context());
            v8::Local<v8::Message> message = try_catch.Message();
            if (!message.IsEmpty()) {
                delayedError()->setMessage(message);
            } else {
                if (hasDelayedError()) delayedError()->clearError();
            }
        } else {
            if (hasDelayedError()) delayedError()->clearError();
        }
    }

    if (sharedContext) {
        ep->sharedContext = lastSharedContext;
        ep->sharedScope = lastSharedScope;
    }

    if (capture.errorString) {
        for (int ii = 0; ii < capture.errorString->count(); ++ii)
            qWarning("%s", qPrintable(capture.errorString->at(ii)));
        delete capture.errorString;
        capture.errorString = 0;
    }

    while (Guard *g = capture.guards.takeFirst())
        g->Delete();

    ep->propertyCapture = lastPropertyCapture;

    return result;
}