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, 25 insertions, 22 deletions

diff --git a/src/qml/qml/qqmlengine.cpp b/src/qml/qml/qqmlengine.cpp
index 0d9326b9a9..eb23b6e256 100644
--- a/src/qml/qml/qqmlengine.cpp
+++ b/src/qml/qml/qqmlengine.cpp
@@ -665,20 +665,21 @@ void QQmlPrivate::qdeclarativeelement_destructor(QObject *o)
 {
     if (QQmlData *d = QQmlData::get(o)) {
         if (d->ownContext) {
-            for (QQmlContextData *lc = d->ownContext->linkedContext; lc; lc = lc->linkedContext) {
+            for (QQmlRefPointer<QQmlContextData> lc = d->ownContext->linkedContext().data(); lc;
+                 lc = lc->linkedContext()) {
                 lc->invalidate();
-                if (lc->contextObject == o)
-                    lc->contextObject = nullptr;
+                if (lc->contextObject() == o)
+                    lc->setContextObject(nullptr);
             }
             d->ownContext->invalidate();
-            if (d->ownContext->contextObject == o)
-                d->ownContext->contextObject = nullptr;
+            if (d->ownContext->contextObject() == o)
+                d->ownContext->setContextObject(nullptr);
             d->ownContext = nullptr;
             d->context = nullptr;
         }
 
-        if (d->outerContext && d->outerContext->contextObject == o)
-            d->outerContext->contextObject = nullptr;
+        if (d->outerContext && d->outerContext->contextObject() == o)
+            d->outerContext->setContextObject(nullptr);
 
         // Mark this object as in the process of deletion to
         // prevent it resolving in bindings
@@ -849,10 +850,10 @@ void QQmlData::setQueuedForDeletion(QObject *object)
     if (object) {
         if (QQmlData *ddata = QQmlData::get(object)) {
             if (ddata->ownContext) {
-                Q_ASSERT(ddata->ownContext == ddata->context);
+                Q_ASSERT(ddata->ownContext.data() == ddata->context);
                 ddata->context->emitDestruction();
-                if (ddata->ownContext->contextObject == object)
-                    ddata->ownContext->contextObject = nullptr;
+                if (ddata->ownContext->contextObject() == object)
+                    ddata->ownContext->setContextObject(nullptr);
                 ddata->ownContext = nullptr;
                 ddata->context = nullptr;
             }
@@ -982,7 +983,7 @@ QQmlEngine::~QQmlEngine()
     // Emit onDestruction signals for the root context before
     // we destroy the contexts, engine, Singleton Types etc. that
     // may be required to handle the destruction signal.
-    QQmlContextData::get(rootContext())->emitDestruction();
+    QQmlContextPrivate::get(rootContext())->emitDestruction();
 
     // clean up all singleton type instances which we own.
     // we do this here and not in the private dtor since otherwise a crash can
@@ -1422,10 +1423,10 @@ QJSValue QQmlEngine::singletonInstance<QJSValue>(int qmlTypeId)
 void QQmlEngine::retranslate()
 {
     Q_D(QQmlEngine);
-    QQmlContextData *context = QQmlContextData::get(d->rootContext)->childContexts;
-    while (context) {
+    for (QQmlRefPointer<QQmlContextData> context
+                = QQmlContextData::get(d->rootContext)->childContexts();
+         context; context = context->nextChild()) {
         context->refreshExpressions();
-        context = context->nextChild;
     }
 }
 
@@ -1469,10 +1470,10 @@ void QQmlEngine::setContextForObject(QObject *object, QQmlContext *context)
         return;
     }
 
-    QQmlContextData *contextData = QQmlContextData::get(context);
+    QQmlRefPointer<QQmlContextData> contextData = QQmlContextData::get(context);
     Q_ASSERT(data->context == nullptr);
-    data->context = contextData;
-    contextData->addObject(data);
+    data->context = contextData.data();
+    contextData->addOwnedObject(data);
 }
 
 /*!
@@ -1576,7 +1577,7 @@ void qmlExecuteDeferred(QObject *object)
     QQmlData *data = QQmlData::get(object);
 
     if (data && !data->deferredData.isEmpty() && !data->wasDeleted(object)) {
-        QQmlEnginePrivate *ep = QQmlEnginePrivate::get(data->context->engine);
+        QQmlEnginePrivate *ep = QQmlEnginePrivate::get(data->context->engine());
 
         QQmlComponentPrivate::DeferredState state;
         QQmlComponentPrivate::beginDeferred(ep, object, &state);
@@ -1598,7 +1599,7 @@ QQmlEngine *qmlEngine(const QObject *obj)
     QQmlData *data = QQmlData::get(obj, false);
     if (!data || !data->context)
         return nullptr;
-    return data->context->engine;
+    return data->context->engine();
 }
 
 static QObject *resolveAttachedProperties(QQmlAttachedPropertiesFunc pf, QQmlData *data,
@@ -1786,7 +1787,9 @@ void QQmlData::NotifyList::layout()
     todo = nullptr;
 }
 
-void QQmlData::deferData(int objectIndex, const QQmlRefPointer<QV4::ExecutableCompilationUnit> &compilationUnit, QQmlContextData *context)
+void QQmlData::deferData(
+        int objectIndex, const QQmlRefPointer<QV4::ExecutableCompilationUnit> &compilationUnit,
+        const QQmlRefPointer<QQmlContextData> &context)
 {
     QQmlData::DeferredData *deferData = new QQmlData::DeferredData;
     deferData->deferredIdx = objectIndex;
@@ -1880,8 +1883,8 @@ void QQmlData::destroyed(QObject *object)
         nextContextObject->prevContextObject = prevContextObject;
     if (prevContextObject)
         *prevContextObject = nextContextObject;
-    else if (outerContext && outerContext->contextObjects == this)
-        outerContext->contextObjects = nextContextObject;
+    else if (outerContext && outerContext->ownedObjects() == this)
+        outerContext->setOwnedObjects(nextContextObject);
 
     QQmlAbstractBinding *binding = bindings;
     while (binding) {