Encapsulate QQmlContextData

This class is not a private detail of QQmlContext. And it is incredibly
hard to see who owns what in there. Let's add some civilization ...

We enforce refcounting for QQmlContextData across the code base, with
two exceptions:

1. QQmlContextPrivate may or may not own its QQmlContextData.
2. We may request a QQmlContextData owned by its parent QQmlContextData.

For these two cases we keep flags in QQmlContextData and when the
respective field (m_parent or m_publicContext) is reset, we release()
once.

Furthermore, QQmlContextData and QQmlGuardedContextData are moved to
their own files, in order to de-spaghettify qqmlcontext_p.h and
qqmlcontext.cpp.

When the QQmlEngine is deleted, any QQmlComponents drop their object
creators now, in order to release any context data held by those.
Before, the context data would be deleted, but the object creators would
retain the dangling pointer.

[ChangeLog][QML][Important Behavior Changes] QQmlContext::baseUrl() does
what the documentation says now: It prefers explicitly set baseUrls over
compilation unit URLs. Only if no baseUrl is set, the CU's URL is
returned. It used to prefer the CU's URL.

Change-Id: Ieeb5dcb07b45d891526191321386d5443b8f5738
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 70 insertions, 477 deletions

diff --git a/src/qml/qml/qqmlcontext.cpp b/src/qml/qml/qqmlcontext.cpp
index abd379a320..a67eeeecc9 100644
--- a/src/qml/qml/qqmlcontext.cpp
+++ b/src/qml/qml/qqmlcontext.cpp
@@ -55,11 +55,6 @@
 
 QT_BEGIN_NAMESPACE
 
-QQmlContextPrivate::QQmlContextPrivate()
-: data(nullptr), notifyIndex(-1)
-{
-}
-
 /*!
     \class QQmlContext
     \brief The QQmlContext class defines a context within a QML engine.
@@ -157,13 +152,8 @@ QQmlContextPrivate::QQmlContextPrivate()
 
 /*! \internal */
 QQmlContext::QQmlContext(QQmlEngine *e, bool)
-: QObject(*(new QQmlContextPrivate))
+    : QObject(*(new QQmlContextPrivate(this, nullptr, e)))
 {
-    Q_D(QQmlContext);
-    d->data = new QQmlContextData(this);
-    ++d->data->refCount;
-
-    d->data->engine = e;
 }
 
 /*!
@@ -171,13 +161,10 @@ QQmlContext::QQmlContext(QQmlEngine *e, bool)
     QObject \a parent.
 */
 QQmlContext::QQmlContext(QQmlEngine *engine, QObject *parent)
-: QObject(*(new QQmlContextPrivate), parent)
+    : QObject(*(new QQmlContextPrivate(
+                    this, engine ? QQmlContextData::get(engine->rootContext()).data() : nullptr)),
+              parent)
 {
-    Q_D(QQmlContext);
-    d->data = new QQmlContextData(this);
-    ++d->data->refCount;
-
-    d->data->setParent(engine?QQmlContextData::get(engine->rootContext()):nullptr);
 }
 
 /*!
@@ -185,24 +172,18 @@ QQmlContext::QQmlContext(QQmlEngine *engine, QObject *parent)
     QObject \a parent.
 */
 QQmlContext::QQmlContext(QQmlContext *parentContext, QObject *parent)
-: QObject(*(new QQmlContextPrivate), parent)
+    : QObject(*(new QQmlContextPrivate(
+                    this, parentContext ? QQmlContextData::get(parentContext).data() : nullptr)),
+              parent)
 {
-    Q_D(QQmlContext);
-    d->data = new QQmlContextData(this);
-    ++d->data->refCount;
-
-    d->data->setParent(parentContext?QQmlContextData::get(parentContext):nullptr);
 }
 
 /*!
     \internal
 */
-QQmlContext::QQmlContext(QQmlContextData *data)
-: QObject(*(new QQmlContextPrivate), nullptr)
+QQmlContext::QQmlContext(QQmlContextPrivate &dd, QObject *parent)
+    : QObject(dd, parent)
 {
-    Q_D(QQmlContext);
-    d->data = data;
-    // don't add a refcount here, as the data owns this context
 }
 
 /*!
@@ -215,10 +196,7 @@ QQmlContext::QQmlContext(QQmlContextData *data)
 QQmlContext::~QQmlContext()
 {
     Q_D(QQmlContext);
-
-    d->data->publicContext = nullptr;
-    if (!--d->data->refCount)
-        d->data->destroy();
+    d->m_data->clearPublicContext();
 }
 
 /*!
@@ -230,7 +208,7 @@ QQmlContext::~QQmlContext()
 bool QQmlContext::isValid() const
 {
     Q_D(const QQmlContext);
-    return d->data && d->data->isValid();
+    return d->m_data->isValid();
 }
 
 /*!
@@ -240,7 +218,7 @@ bool QQmlContext::isValid() const
 QQmlEngine *QQmlContext::engine() const
 {
     Q_D(const QQmlContext);
-    return d->data->engine;
+    return d->m_data->engine();
 }
 
 /*!
@@ -250,7 +228,10 @@ QQmlEngine *QQmlContext::engine() const
 QQmlContext *QQmlContext::parentContext() const
 {
     Q_D(const QQmlContext);
-    return d->data->parent?d->data->parent->asQQmlContext():nullptr;
+
+    if (QQmlRefPointer<QQmlContextData> parent = d->m_data->parent())
+        return parent->asQQmlContext();
+    return nullptr;
 }
 
 /*!
@@ -259,7 +240,7 @@ QQmlContext *QQmlContext::parentContext() const
 QObject *QQmlContext::contextObject() const
 {
     Q_D(const QQmlContext);
-    return d->data->contextObject;
+    return d->m_data->contextObject();
 }
 
 /*!
@@ -269,19 +250,19 @@ void QQmlContext::setContextObject(QObject *object)
 {
     Q_D(QQmlContext);
 
-    QQmlContextData *data = d->data;
+    QQmlRefPointer<QQmlContextData> data = d->m_data;
 
-    if (data->isInternal) {
+    if (data->isInternal()) {
         qWarning("QQmlContext: Cannot set context object for internal context.");
         return;
     }
 
-    if (!isValid()) {
+    if (!data->isValid()) {
         qWarning("QQmlContext: Cannot set context object on invalid context.");
         return;
     }
 
-    data->contextObject = object;
+    data->setContextObject(object);
     data->refreshExpressions();
 }
 
@@ -291,31 +272,30 @@ void QQmlContext::setContextObject(QObject *object)
 void QQmlContext::setContextProperty(const QString &name, const QVariant &value)
 {
     Q_D(QQmlContext);
-    if (d->notifyIndex == -1)
-        d->notifyIndex = QMetaObjectPrivate::absoluteSignalCount(&QQmlContext::staticMetaObject);
+    if (d->notifyIndex() == -1)
+        d->setNotifyIndex(QMetaObjectPrivate::absoluteSignalCount(&QQmlContext::staticMetaObject));
 
-    QQmlContextData *data = d->data;
+    QQmlRefPointer<QQmlContextData> data = d->m_data;
 
-    if (data->isInternal) {
+    if (data->isInternal()) {
         qWarning("QQmlContext: Cannot set property on internal context.");
         return;
     }
 
-    if (!isValid()) {
+    if (!data->isValid()) {
         qWarning("QQmlContext: Cannot set property on invalid context.");
         return;
     }
 
-    QV4::IdentifierHash &properties = data->detachedPropertyNames();
-    int idx = properties.value(name);
+    QV4::IdentifierHash *properties = data->detachedPropertyNames();
+    int idx = properties->value(name);
     if (idx == -1) {
-        properties.add(name, data->idValueCount + d->propertyValues.count());
-        d->propertyValues.append(value);
-
+        properties->add(name, data->numIdValues() + d->numPropertyValues());
+        d->appendPropertyValue(value);
         data->refreshExpressions();
     } else {
-        d->propertyValues[idx] = value;
-        QMetaObject::activate(this, d->notifyIndex, idx, nullptr);
+        d->setPropertyValue(idx, value);
+        QMetaObject::activate(this, d->notifyIndex(), idx, nullptr);
     }
 
     if (auto *obj = qvariant_cast<QObject *>(value)) {
@@ -350,20 +330,15 @@ void QQmlContext::setContextProperties(const QVector<PropertyPair> &properties)
 {
     Q_D(const QQmlContext);
 
-    QQmlContextData *data = d->data;
-
-    QQmlJavaScriptExpression *expressions = data->expressions;
-    QQmlContextData *childContexts = data->childContexts;
-
-    data->expressions = nullptr;
-    data->childContexts = nullptr;
+    QQmlRefPointer<QQmlContextData> data = d->m_data;
+    QQmlJavaScriptExpression *expressions = data->takeExpressions();
+    QQmlRefPointer<QQmlContextData> childContexts = data->takeChildContexts();
 
     for (const auto &property : properties)
         setContextProperty(property.name, property.value);
 
-    data->expressions = expressions;
-    data->childContexts = childContexts;
-
+    data->setExpressions(expressions);
+    data->setChildContexts(childContexts);
     data->refreshExpressions();
 }
 
@@ -389,28 +364,27 @@ QVariant QQmlContext::contextProperty(const QString &name) const
     QVariant value;
     int idx = -1;
 
-    QQmlContextData *data = d->data;
+    QQmlRefPointer<QQmlContextData> data = d->m_data;
 
-    const QV4::IdentifierHash &properties = data->propertyNames();
+    const QV4::IdentifierHash properties = data->propertyNames();
     if (properties.count())
         idx = properties.value(name);
 
     if (idx == -1) {
-        if (data->contextObject) {
-            QObject *obj = data->contextObject;
+        if (QObject *obj = data->contextObject()) {
             QQmlPropertyData local;
             QQmlPropertyData *property =
-                QQmlPropertyCache::property(data->engine, obj, name, data, local);
+                QQmlPropertyCache::property(data->engine(), obj, name, data, local);
 
             if (property) value = obj->metaObject()->property(property->coreIndex()).read(obj);
         }
         if (!value.isValid() && parentContext())
             value = parentContext()->contextProperty(name);
     } else {
-        if (idx >= d->propertyValues.count())
-            value = QVariant::fromValue(data->idValues[idx - d->propertyValues.count()].data());
+        if (idx >= d->numPropertyValues())
+            value = QVariant::fromValue(data->idValue(idx - d->numPropertyValues()));
         else
-            value = d->propertyValues[idx];
+            value = d->propertyValue(idx);
     }
 
     return value;
@@ -427,7 +401,7 @@ QString QQmlContext::nameForObject(QObject *object) const
 {
     Q_D(const QQmlContext);
 
-    return d->data->findObjectId(object);
+    return d->m_data->findObjectId(object);
 }
 
 /*!
@@ -439,37 +413,9 @@ QString QQmlContext::nameForObject(QObject *object) const
 QUrl QQmlContext::resolvedUrl(const QUrl &src)
 {
     Q_D(QQmlContext);
-    return d->data->resolvedUrl(src);
-}
-
-QUrl QQmlContextData::resolvedUrl(const QUrl &src)
-{
-    QUrl resolved;
-    if (src.isRelative() && !src.isEmpty()) {
-        QQmlContextData *ctxt = this;
-        do {
-            if (ctxt->url().isValid())
-                break;
-            else
-                ctxt = ctxt->parent;
-        } while (ctxt);
-
-        if (ctxt)
-            resolved = ctxt->url().resolved(src);
-        else if (engine)
-            resolved = engine->baseUrl().resolved(src);
-    } else {
-        resolved = src;
-    }
-
-    if (resolved.isEmpty()) //relative but no ctxt
-        return resolved;
-
-    return engine ? engine->interceptUrl(resolved, QQmlAbstractUrlInterceptor::UrlString)
-                  : resolved;
+    return d->m_data->resolvedUrl(src);
 }
 
-
 /*!
     Explicitly sets the url resolvedUrl() will use for relative references to \a baseUrl.
 
@@ -481,9 +427,8 @@ QUrl QQmlContextData::resolvedUrl(const QUrl &src)
 void QQmlContext::setBaseUrl(const QUrl &baseUrl)
 {
     Q_D(QQmlContext);
-
-    d->data->baseUrl = baseUrl;
-    d->data->baseUrlString = baseUrl.toString();
+    d->m_data->setBaseUrl(baseUrl);
+    d->m_data->setBaseUrlString(baseUrl.toString());
 }
 
 /*!
@@ -493,14 +438,7 @@ void QQmlContext::setBaseUrl(const QUrl &baseUrl)
 QUrl QQmlContext::baseUrl() const
 {
     Q_D(const QQmlContext);
-    const QQmlContextData* data = d->data;
-    while (data && data->url().isEmpty())
-        data = data->parent;
-
-    if (data)
-        return data->url();
-    else
-        return QUrl();
+    return d->m_data->baseUrl();
 }
 
 int QQmlContextPrivate::context_count(QQmlListProperty<QObject> *prop)
@@ -509,11 +447,10 @@ int QQmlContextPrivate::context_count(QQmlListProperty<QObject> *prop)
     QQmlContextPrivate *d = QQmlContextPrivate::get(context);
     int contextProperty = (int)(quintptr)prop->data;
 
-    if (d->propertyValues.at(contextProperty).userType() != qMetaTypeId<QList<QObject*> >()) {
+    if (d->propertyValue(contextProperty).userType() != qMetaTypeId<QList<QObject*> >())
         return 0;
-    } else {
-        return ((const QList<QObject> *)d->propertyValues.at(contextProperty).constData())->count();
-    }
+    else
+        return ((const QList<QObject> *)d->propertyValue(contextProperty).constData())->count();
 }
 
 QObject *QQmlContextPrivate::context_at(QQmlListProperty<QObject> *prop, int index)
@@ -522,384 +459,40 @@ QObject *QQmlContextPrivate::context_at(QQmlListProperty<QObject> *prop, int ind
     QQmlContextPrivate *d = QQmlContextPrivate::get(context);
     int contextProperty = (int)(quintptr)prop->data;
 
-    if (d->propertyValues.at(contextProperty).userType() != qMetaTypeId<QList<QObject*> >()) {
+    if (d->propertyValue(contextProperty).userType() != qMetaTypeId<QList<QObject*> >())
         return nullptr;
-    } else {
-        return ((const QList<QObject*> *)d->propertyValues.at(contextProperty).constData())->at(index);
-    }
+    else
+        return ((const QList<QObject*> *)d->propertyValue(contextProperty).constData())->at(index);
 }
 
 void QQmlContextPrivate::dropDestroyedQObject(const QString &name, QObject *destroyed)
 {
-    if (!data->isValid())
+    if (!m_data->isValid())
         return;
 
-    const int idx = data->propertyNames().value(name);
+    const int idx = m_data->propertyNames().value(name);
     Q_ASSERT(idx >= 0);
-    if (qvariant_cast<QObject *>(propertyValues[idx]) != destroyed)
+    if (qvariant_cast<QObject *>(propertyValue(idx)) != destroyed)
         return;
 
-    propertyValues[idx] = QVariant::fromValue<QObject *>(nullptr);
-    QMetaObject::activate(q_func(), notifyIndex, idx, nullptr);
-}
-
-
-QQmlContextData::QQmlContextData()
-    : QQmlContextData(nullptr)
-{
-}
-
-QQmlContextData::QQmlContextData(QQmlContext *ctxt)
-    : engine(nullptr), isInternal(false), isJSContext(false),
-      isPragmaLibraryContext(false), unresolvedNames(false), hasEmittedDestruction(false), isRootObjectInCreation(false),
-      stronglyReferencedByParent(false), hasExtraObject(false), publicContext(ctxt), incubator(nullptr), componentObjectIndex(-1),
-      contextObject(nullptr), nextChild(nullptr), prevChild(nullptr),
-      expressions(nullptr), contextObjects(nullptr), idValues(nullptr), idValueCount(0),
-      componentAttached(nullptr)
-{
-}
-
-void QQmlContextData::emitDestruction()
-{
-    if (!hasEmittedDestruction) {
-        hasEmittedDestruction = true;
-
-        // Emit the destruction signal - must be emitted before invalidate so that the
-        // context is still valid if bindings or resultant expression evaluation requires it
-        if (engine) {
-            while (componentAttached) {
-                QQmlComponentAttached *a = componentAttached;
-                componentAttached = a->next;
-                if (componentAttached) componentAttached->prev = &componentAttached;
-
-                a->next = nullptr;
-                a->prev = nullptr;
-
-                emit a->destruction();
-            }
-
-            QQmlContextData * child = childContexts;
-            while (child) {
-                child->emitDestruction();
-                child = child->nextChild;
-            }
-        }
-    }
-}
-
-void QQmlContextData::invalidate()
-{
-    emitDestruction();
-
-    while (childContexts) {
-        Q_ASSERT(childContexts != this);
-        if (childContexts->stronglyReferencedByParent && !--childContexts->refCount)
-            childContexts->destroy();
-        else
-            childContexts->invalidate();
-    }
-
-    if (prevChild) {
-        *prevChild = nextChild;
-        if (nextChild) nextChild->prevChild = prevChild;
-        nextChild = nullptr;
-        prevChild = nullptr;
-    }
-
-    importedScripts.clear();
-
-    engine = nullptr;
-    parent = nullptr;
-}
-
-void QQmlContextData::clearContextRecursively()
-{
-    clearContext();
-
-    for (auto ctxIt = childContexts; ctxIt; ctxIt = ctxIt->nextChild)
-        ctxIt->clearContextRecursively();
-}
-
-void QQmlContextData::clearContext()
-{
-    emitDestruction();
-
-    QQmlJavaScriptExpression *expression = expressions;
-    while (expression) {
-        QQmlJavaScriptExpression *nextExpression = expression->m_nextExpression;
-
-        expression->m_prevExpression = nullptr;
-        expression->m_nextExpression = nullptr;
-
-        expression->setContext(nullptr);
-
-        expression = nextExpression;
-    }
-    expressions = nullptr;
-}
-
-void QQmlContextData::destroy()
-{
-    Q_ASSERT(refCount == 0);
-    linkedContext = nullptr;
-
-    // avoid recursion
-    ++refCount;
-    if (engine)
-        invalidate();
-
-    Q_ASSERT(refCount == 1);
-    clearContext();
-    Q_ASSERT(refCount == 1);
-
-    while (contextObjects) {
-        QQmlData *co = contextObjects;
-        contextObjects = contextObjects->nextContextObject;
-
-        if (co->context == this)
-            co->context = nullptr;
-        co->outerContext = nullptr;
-        co->nextContextObject = nullptr;
-        co->prevContextObject = nullptr;
-    }
-    Q_ASSERT(refCount == 1);
-
-    QQmlGuardedContextData *contextGuard = contextGuards;
-    while (contextGuard) {
-        QQmlGuardedContextData *next = contextGuard->m_next;
-        contextGuard->m_next = nullptr;
-        contextGuard->m_prev = nullptr;
-        contextGuard->m_contextData = nullptr;
-        contextGuard = next;
-    }
-    contextGuards = nullptr;
-    Q_ASSERT(refCount == 1);
-
-    delete [] idValues;
-    idValues = nullptr;
-
-    Q_ASSERT(refCount == 1);
-    if (publicContext) {
-        // the QQmlContext destructor will remove one ref again
-        ++refCount;
-        delete publicContext;
-    }
-
-    Q_ASSERT(refCount == 1);
-    --refCount;
-    Q_ASSERT(refCount == 0);
-
-    delete this;
-}
-
-void QQmlContextData::setParent(QQmlContextData *p, bool stronglyReferencedByParent)
-{
-    if (p == parent)
-        return;
-    if (p) {
-        Q_ASSERT(!parent);
-        parent = p;
-        this->stronglyReferencedByParent = stronglyReferencedByParent;
-        if (stronglyReferencedByParent)
-            ++refCount; // balanced in QQmlContextData::invalidate()
-        engine = p->engine;
-        nextChild = p->childContexts;
-        if (nextChild) nextChild->prevChild = &nextChild;
-        prevChild = &p->childContexts;
-        p->childContexts = this;
-    }
-}
-
-void QQmlContextData::refreshExpressionsRecursive(QQmlJavaScriptExpression *expression)
-{
-    QQmlJavaScriptExpression::DeleteWatcher w(expression);
-
-    if (expression->m_nextExpression)
-        refreshExpressionsRecursive(expression->m_nextExpression);
-
-    if (!w.wasDeleted())
-        expression->refresh();
-}
-
-QQmlContextData::~QQmlContextData()
-{
-}
-
-static inline bool expressions_to_run(QQmlContextData *ctxt, bool isGlobalRefresh)
-{
-    return ctxt->expressions && (!isGlobalRefresh || ctxt->unresolvedNames);
-}
-
-void QQmlContextData::refreshExpressionsRecursive(bool isGlobal)
-{
-    // For efficiency, we try and minimize the number of guards we have to create
-    if (expressions_to_run(this, isGlobal) && (nextChild || childContexts)) {
-        QQmlGuardedContextData guard(this);
-
-        if (childContexts)
-            childContexts->refreshExpressionsRecursive(isGlobal);
-
-        if (guard.isNull()) return;
-
-        if (nextChild)
-            nextChild->refreshExpressionsRecursive(isGlobal);
-
-        if (guard.isNull()) return;
-
-        if (expressions_to_run(this, isGlobal))
-            refreshExpressionsRecursive(expressions);
-
-    } else if (expressions_to_run(this, isGlobal)) {
-
-        refreshExpressionsRecursive(expressions);
-
-    } else if (nextChild && childContexts) {
-
-        QQmlGuardedContextData guard(this);
-
-        childContexts->refreshExpressionsRecursive(isGlobal);
-
-        if (!guard.isNull() && nextChild)
-            nextChild->refreshExpressionsRecursive(isGlobal);
-
-    } else if (nextChild) {
-
-        nextChild->refreshExpressionsRecursive(isGlobal);
-
-    } else if (childContexts) {
-
-        childContexts->refreshExpressionsRecursive(isGlobal);
-
-    }
-}
-
-// Refreshes all expressions that could possibly depend on this context.  Refreshing flushes all
-// context-tree dependent caches in the expressions, and should occur every time the context tree
-// *structure* (not values) changes.
-void QQmlContextData::refreshExpressions()
-{
-    bool isGlobal = (parent == nullptr);
-
-    // For efficiency, we try and minimize the number of guards we have to create
-    if (expressions_to_run(this, isGlobal) && childContexts) {
-        QQmlGuardedContextData guard(this);
-
-        childContexts->refreshExpressionsRecursive(isGlobal);
-
-        if (!guard.isNull() && expressions_to_run(this, isGlobal))
-            refreshExpressionsRecursive(expressions);
-
-    } else if (expressions_to_run(this, isGlobal)) {
-
-        refreshExpressionsRecursive(expressions);
-
-    } else if (childContexts) {
-
-        childContexts->refreshExpressionsRecursive(isGlobal);
-
-    }
-}
-
-void QQmlContextData::addObject(QQmlData *data)
-{
-    if (data->outerContext) {
-        if (data->nextContextObject)
-            data->nextContextObject->prevContextObject = data->prevContextObject;
-        if (data->prevContextObject)
-            *data->prevContextObject = data->nextContextObject;
-        else if (data->outerContext->contextObjects == data)
-            data->outerContext->contextObjects = data->nextContextObject;
-    }
-
-    data->outerContext = this;
-
-    data->nextContextObject = contextObjects;
-    if (data->nextContextObject)
-        data->nextContextObject->prevContextObject = &data->nextContextObject;
-    data->prevContextObject = &contextObjects;
-    contextObjects = data;
-}
-
-void QQmlContextData::setIdProperty(int idx, QObject *obj)
-{
-    idValues[idx] = obj;
-    idValues[idx].context = this;
-}
-
-QString QQmlContextData::findObjectId(const QObject *obj) const
-{
-    const QV4::IdentifierHash &properties = propertyNames();
-    if (propertyNameCache.isEmpty())
-        return QString();
-
-    for (int ii = 0; ii < idValueCount; ii++) {
-        if (idValues[ii] == obj)
-            return properties.findId(ii);
-    }
-
-    if (publicContext) {
-        QQmlContextPrivate *p = QQmlContextPrivate::get(publicContext);
-        for (int ii = 0; ii < p->propertyValues.count(); ++ii)
-            if (p->propertyValues.at(ii) == QVariant::fromValue(const_cast<QObject *>(obj)))
-                return properties.findId(ii);
-    }
-
-    if (linkedContext)
-        return linkedContext->findObjectId(obj);
-    return QString();
-}
-
-QQmlContext *QQmlContextData::asQQmlContext()
-{
-    if (!publicContext)
-        publicContext = new QQmlContext(this);
-    return publicContext;
-}
-
-QQmlContextPrivate *QQmlContextData::asQQmlContextPrivate()
-{
-    return QQmlContextPrivate::get(asQQmlContext());
-}
-
-void QQmlContextData::initFromTypeCompilationUnit(const QQmlRefPointer<QV4::ExecutableCompilationUnit> &unit, int subComponentIndex)
-{
-    typeCompilationUnit = unit;
-    componentObjectIndex = subComponentIndex == -1 ? /*root object*/0 : subComponentIndex;
-    Q_ASSERT(!idValues);
-    idValueCount = typeCompilationUnit->objectAt(componentObjectIndex)->nNamedObjectsInComponent;
-    idValues = new ContextGuard[idValueCount];
-}
-
-const QV4::IdentifierHash &QQmlContextData::propertyNames() const
-{
-    if (propertyNameCache.isEmpty()) {
-        if (typeCompilationUnit)
-            propertyNameCache = typeCompilationUnit->namedObjectsPerComponent(componentObjectIndex);
-        else
-            propertyNameCache = QV4::IdentifierHash(engine->handle());
-    }
-    return propertyNameCache;
-}
-
-QV4::IdentifierHash &QQmlContextData::detachedPropertyNames()
-{
-    propertyNames();
-    propertyNameCache.detach();
-    return propertyNameCache;
+    setPropertyValue(idx, QVariant::fromValue<QObject *>(nullptr));
+    QMetaObject::activate(q_func(), notifyIndex(), idx, nullptr);
 }
 
-QUrl QQmlContextData::url() const
+void QQmlContextPrivate::emitDestruction()
 {
-    if (typeCompilationUnit)
-        return typeCompilationUnit->finalUrl();
-    return baseUrl;
+    m_data->emitDestruction();
 }
 
-QString QQmlContextData::urlString() const
+// m_data is owned by the public context. When the public context is reset to nullptr, it will be
+// deref'd. It's OK to pass a half-created publicContext here. We will not dereference it during
+// construction.
+QQmlContextPrivate::QQmlContextPrivate(
+        QQmlContext *publicContext, QQmlContextData *parent, QQmlEngine *engine) :
+    m_data(new QQmlContextData(QQmlContextData::OwnedByPublicContext, publicContext,
+                               parent, engine))
 {
-    if (typeCompilationUnit)
-        return typeCompilationUnit->finalUrlString();
-    return baseUrlString;
+    Q_ASSERT(publicContext != nullptr);
 }
 
 QT_END_NAMESPACE