qquickdeferredexecute.cpp

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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qquickdeferredexecute_p_p.h"
 
#include <QtCore/qhash.h>
#include <QtQml/qqmlengine.h>
#include <QtQml/private/qqmldata_p.h>
#include <QtQml/private/qqmlcomponent_p.h>
#include <QtQml/private/qqmlobjectcreator_p.h>
 
#include <deque>
 
QT_BEGIN_NAMESPACE
 
namespace QtQuickPrivate {
 
static void cancelDeferred(QQmlData *ddata, int propertyIndex)
{
    auto dit = ddata->deferredData.rbegin();
    while (dit != ddata->deferredData.rend()) {
        (*dit)->bindings.remove(propertyIndex);
        ++dit;
    }
}
 
static bool beginDeferred(QQmlEnginePrivate *enginePriv, const QQmlProperty &property, QQmlComponentPrivate::DeferredState *deferredState)
{
    QObject *object = property.object();
    QQmlData *ddata = QQmlData::get(object);
    Q_ASSERT(!ddata->deferredData.isEmpty());
 
    int propertyIndex = property.index();
    int wasInProgress = enginePriv->inProgressCreations;
 
    /* we don't want deferred properties to suddenly depend on arbitrary
       other properties which might have trigerred the construction of
       objects as a consequence of a read.
     */
    auto bindingStatus = QtPrivate::suspendCurrentBindingStatus();
    auto cleanup = qScopeGuard([&](){
        QtPrivate::restoreBindingStatus(bindingStatus);
    });
 
    for (auto dit = ddata->deferredData.rbegin(); dit != ddata->deferredData.rend(); ++dit) {
        QQmlData::DeferredData *deferData = *dit;
 
        auto bindings = deferData->bindings;
        auto range = bindings.equal_range(propertyIndex);
        if (range.first == bindings.end())
            continue;
 
        QQmlComponentPrivate::ConstructionState state;
        state.setCompletePending(true);
 
        QQmlContextData *creationContext = nullptr;
        state.initCreator(deferData->context->parent(), deferData->compilationUnit, creationContext);
 
        enginePriv->inProgressCreations++;
 
        std::deque<const QV4::CompiledData::Binding *> reversedBindings;
        std::copy(range.first, range.second, std::front_inserter(reversedBindings));
        state.creator()->beginPopulateDeferred(deferData->context);
        for (const QV4::CompiledData::Binding *binding : reversedBindings)
            state.creator()->populateDeferredBinding(property, deferData->deferredIdx, binding);
        state.creator()->finalizePopulateDeferred();
        state.appendCreatorErrors();
 
        deferredState->push_back(std::move(state));
 
        // Cleanup any remaining deferred bindings for this property, also in inner contexts,
        // to avoid executing them later and overriding the property that was just populated.
        cancelDeferred(ddata, propertyIndex);
        break;
    }
 
    return enginePriv->inProgressCreations > wasInProgress;
}
 
void beginDeferred(QObject *object, const QString &property,
                   QQuickUntypedDeferredPointer *delegate, bool isOwnState)
{
    QQmlData *data = QQmlData::get(object);
    if (data && !data->deferredData.isEmpty() && !data->wasDeleted(object) && data->context) {
        QQmlEnginePrivate *ep = QQmlEnginePrivate::get(data->context->engine());
 
        QQmlComponentPrivate::DeferredState state;
        if (beginDeferred(ep, QQmlProperty(object, property), &state)) {
            if (QQmlComponentPrivate::DeferredState *delegateState = delegate->deferredState())
                delegateState->swap(state);
        } else if (isOwnState) {
            delegate->clearDeferredState();
        }
 
        // Release deferred data for those compilation units that no longer have deferred bindings
        data->releaseDeferredData();
    } else if (isOwnState) {
        delegate->clearDeferredState();
    }
}
 
void cancelDeferred(QObject *object, const QString &property)
{
    QQmlData *data = QQmlData::get(object);
    if (data)
        cancelDeferred(data, QQmlProperty(object, property).index());
}
 
void completeDeferred(QObject *object, const QString &property, QQuickUntypedDeferredPointer *delegate)
{
    Q_UNUSED(property);
    QQmlComponentPrivate::DeferredState *state = delegate->deferredState();
    if (!state)
        return;
 
    QQmlData *data = QQmlData::get(object);
    if (data && !data->wasDeleted(object)) {
        /* we don't want deferred properties to suddenly depend on arbitrary
           other properties which might have trigerred the construction of
           objects as a consequence of a read.
         */
        auto bindingStatus = QtPrivate::suspendCurrentBindingStatus();
        auto cleanup = qScopeGuard([&](){
            QtPrivate::restoreBindingStatus(bindingStatus);
        });
 
        QQmlComponentPrivate::DeferredState localState = std::move(*state);
        delegate->clearDeferredState();
        QQmlEnginePrivate *ep = QQmlEnginePrivate::get(data->context->engine());
        QQmlComponentPrivate::completeDeferred(ep, &localState);
    } else {
        delegate->clearDeferredState();
    }
}
 
} // QtQuickPrivate
 
QT_END_NAMESPACE