path: root/src/declarative/util/qdeclarativepropertychanges.cpp

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#include "private/qdeclarativepropertychanges_p.h"

#include "private/qdeclarativeopenmetaobject_p.h"
#include "private/qdeclarativerewrite_p.h"
#include "private/qdeclarativeengine_p.h"
#include "private/qdeclarativecompiler_p.h"

#include <qdeclarativeinfo.h>
#include <private/qdeclarativecustomparser_p.h>
#include <private/qdeclarativeparser_p.h>
#include <qdeclarativeexpression.h>
#include <private/qdeclarativebinding_p.h>
#include <qdeclarativecontext.h>
#include <private/qdeclarativeguard_p.h>
#include <private/qdeclarativeproperty_p.h>
#include <private/qdeclarativecontext_p.h>
#include <qdeclarativestate_p_p.h>

#include <QtCore/qdebug.h>

#include <private/qobject_p.h>

QT_BEGIN_NAMESPACE

/*!
    \qmltype PropertyChanges
    \instantiates QDeclarativePropertyChanges
    \ingroup qml-state-elements
    \since 4.7
    \brief The PropertyChanges element describes new property bindings or values for a state.

    PropertyChanges is used to define the property values or bindings in a
    \l State. This enables an item's property values to be changed when it
    \l {QML States}{changes between states}.

    To create a PropertyChanges object, specify the \l target item whose
    properties are to be modified, and define the new property values or
    bindings. For example:

    \snippet doc/src/snippets/declarative/propertychanges.qml import
    \codeline
    \snippet doc/src/snippets/declarative/propertychanges.qml 0

    When the mouse is pressed, the \l Rectangle changes to the \e resized
    state. In this state, the PropertyChanges object sets the rectangle's
    color to blue and the \c height value to that of \c container.height.

    Note this automatically binds \c rect.height to \c container.height
    in the \e resized state. If a property binding should not be
    established, and the height should just be set to the value of
    \c container.height at the time of the state change, set the \l explicit
    property to \c true.

    A PropertyChanges object can also override the default signal handler
    for an object to implement a signal handler specific to the new state:

    \qml
    PropertyChanges {
        target: myMouseArea
        onClicked: doSomethingDifferent()
    }
    \endqml

    \note PropertyChanges can be used to change anchor margins, but not other anchor
    values; use AnchorChanges for this instead. Similarly, to change an \l Item's
    \l {Item::}{parent} value, use ParentChanges instead.


    \section2 Resetting property values

    The \c undefined value can be used to reset the property value for a state.
    In the following example, when \c theText changes to the \e widerText
    state, its \c width property is reset, giving the text its natural width
    and displaying the whole string on a single line.

    \snippet doc/src/snippets/declarative/propertychanges.qml reset


    \section2 Immediate property changes in transitions

    When \l{QML Animation and Transitions}{Transitions} are used to animate
    state changes, they animate properties from their values in the current
    state to those defined in the new state (as defined by PropertyChanges
    objects). However, it is sometimes desirable to set a property value
    \e immediately during a \l Transition, without animation; in these cases,
    the PropertyAction element can be used to force an immediate property
    change.

    See the PropertyAction documentation for more details.

    \sa {declarative/animation/states}{states example}, {qmlstate}{States}, QtDeclarative
*/

/*!
    \qmlproperty Object PropertyChanges::target
    This property holds the object which contains the properties to be changed.
*/

class QDeclarativeReplaceSignalHandler : public QDeclarativeActionEvent
{
public:
    QDeclarativeReplaceSignalHandler() : expression(0), reverseExpression(0),
                                rewindExpression(0), ownedExpression(0) {}
    ~QDeclarativeReplaceSignalHandler() {
        delete ownedExpression;
    }

    virtual QString typeName() const { return QLatin1String("ReplaceSignalHandler"); }

    QDeclarativeProperty property;
    QDeclarativeExpression *expression;
    QDeclarativeExpression *reverseExpression;
    QDeclarativeExpression *rewindExpression;
    QDeclarativeGuard<QDeclarativeExpression> ownedExpression;

    virtual void execute(Reason) {
        ownedExpression = QDeclarativePropertyPrivate::setSignalExpression(property, expression);
        if (ownedExpression == expression)
            ownedExpression = 0;
    }

    virtual bool isReversable() { return true; }
    virtual void reverse(Reason) {
        ownedExpression = QDeclarativePropertyPrivate::setSignalExpression(property, reverseExpression);
        if (ownedExpression == reverseExpression)
            ownedExpression = 0;
    }

    virtual void saveOriginals() {
        saveCurrentValues();
        reverseExpression = rewindExpression;
    }

    virtual bool needsCopy() { return true; }
    virtual void copyOriginals(QDeclarativeActionEvent *other)
    {
        QDeclarativeReplaceSignalHandler *rsh = static_cast<QDeclarativeReplaceSignalHandler*>(other);
        saveCurrentValues();
        if (rsh == this)
            return;
        reverseExpression = rsh->reverseExpression;
        if (rsh->ownedExpression == reverseExpression) {
            ownedExpression = rsh->ownedExpression;
            rsh->ownedExpression = 0;
        }
    }

    virtual void rewind() {
        ownedExpression = QDeclarativePropertyPrivate::setSignalExpression(property, rewindExpression);
        if (ownedExpression == rewindExpression)
            ownedExpression = 0;
    }
    virtual void saveCurrentValues() {
        rewindExpression = QDeclarativePropertyPrivate::signalExpression(property);
    }

    virtual bool override(QDeclarativeActionEvent*other) {
        if (other == this)
            return true;
        if (other->typeName() != typeName())
            return false;
        if (static_cast<QDeclarativeReplaceSignalHandler*>(other)->property == property)
            return true;
        return false;
    }
};


class QDeclarativePropertyChangesPrivate : public QDeclarativeStateOperationPrivate
{
    Q_DECLARE_PUBLIC(QDeclarativePropertyChanges)
public:
    QDeclarativePropertyChangesPrivate() : decoded(true), restore(true),
                                isExplicit(false) {}

    QDeclarativeGuard<QObject> object;
    QByteArray data;

    bool decoded : 1;
    bool restore : 1;
    bool isExplicit : 1;

    void decode();

    class ExpressionChange {
    public:
        ExpressionChange(const QString &_name,
                         QDeclarativeBinding::Identifier _id,
                         QDeclarativeExpression *_expr)
            : name(_name), id(_id), expression(_expr) {}
        QString name;
        QDeclarativeBinding::Identifier id;
        QDeclarativeExpression *expression;
    };

    QList<QPair<QString, QVariant> > properties;
    QList<ExpressionChange> expressions;
    QList<QDeclarativeReplaceSignalHandler*> signalReplacements;

    QDeclarativeProperty property(const QString &);
};

void
QDeclarativePropertyChangesParser::compileList(QList<QPair<QByteArray, QVariant> > &list,
                                     const QByteArray &pre,
                                     const QDeclarativeCustomParserProperty &prop)
{
    QByteArray propName = pre + prop.name();

    QList<QVariant> values = prop.assignedValues();
    for (int ii = 0; ii < values.count(); ++ii) {
        const QVariant &value = values.at(ii);

        if (value.userType() == qMetaTypeId<QDeclarativeCustomParserNode>()) {
            error(qvariant_cast<QDeclarativeCustomParserNode>(value),
                  QDeclarativePropertyChanges::tr("PropertyChanges does not support creating state-specific objects."));
            continue;
        } else if(value.userType() == qMetaTypeId<QDeclarativeCustomParserProperty>()) {

            QDeclarativeCustomParserProperty prop =
                qvariant_cast<QDeclarativeCustomParserProperty>(value);
            QByteArray pre = propName + '.';
            compileList(list, pre, prop);

        } else {
            list << qMakePair(propName, value);
        }
    }
}

QByteArray
QDeclarativePropertyChangesParser::compile(const QList<QDeclarativeCustomParserProperty> &props)
{
    QList<QPair<QByteArray, QVariant> > data;
    for(int ii = 0; ii < props.count(); ++ii)
        compileList(data, QByteArray(), props.at(ii));

    QByteArray rv;
    QDataStream ds(&rv, QIODevice::WriteOnly);

    ds << data.count();
    for(int ii = 0; ii < data.count(); ++ii) {
        QDeclarativeParser::Variant v = qvariant_cast<QDeclarativeParser::Variant>(data.at(ii).second);
        QVariant var;
        bool isScript = v.isScript();
        QDeclarativeBinding::Identifier id = 0;
        switch(v.type()) {
        case QDeclarativeParser::Variant::Boolean:
            var = QVariant(v.asBoolean());
            break;
        case QDeclarativeParser::Variant::Number:
            var = QVariant(v.asNumber());
            break;
        case QDeclarativeParser::Variant::String:
            var = QVariant(v.asString());
            break;
        case QDeclarativeParser::Variant::Invalid:
        case QDeclarativeParser::Variant::Script:
            var = QVariant(v.asScript());
            {
                // Pre-rewrite the expression
                QString expression = v.asScript();
                id = rewriteBinding(expression, data.at(ii).first); //### recreates the AST, which is slow
            }
            break;
        }

        ds << QString::fromUtf8(data.at(ii).first) << isScript << var;
        if (isScript)
            ds << id;
    }

    return rv;
}

void QDeclarativePropertyChangesPrivate::decode()
{
    Q_Q(QDeclarativePropertyChanges);
    if (decoded)
        return;

    QDataStream ds(&data, QIODevice::ReadOnly);

    int count;
    ds >> count;
    for (int ii = 0; ii < count; ++ii) {
        QString name;
        bool isScript;
        QVariant data;
        QDeclarativeBinding::Identifier id = QDeclarativeBinding::Invalid;
        ds >> name;
        ds >> isScript;
        ds >> data;
        if (isScript)
            ds >> id;

        QDeclarativeProperty prop = property(name);      //### better way to check for signal property?
        if (prop.type() & QDeclarativeProperty::SignalProperty) {
            QDeclarativeExpression *expression = new QDeclarativeExpression(qmlContext(q), object, data.toString());
            QDeclarativeData *ddata = QDeclarativeData::get(q);
            if (ddata && ddata->outerContext && !ddata->outerContext->url.isEmpty())
                expression->setSourceLocation(ddata->outerContext->url.toString(), ddata->lineNumber);
            QDeclarativeReplaceSignalHandler *handler = new QDeclarativeReplaceSignalHandler;
            handler->property = prop;
            handler->expression = expression;
            signalReplacements << handler;
        } else if (isScript) {
            QDeclarativeExpression *expression = new QDeclarativeExpression(qmlContext(q), object, data.toString());
            QDeclarativeData *ddata = QDeclarativeData::get(q);
            if (ddata && ddata->outerContext && !ddata->outerContext->url.isEmpty())
                expression->setSourceLocation(ddata->outerContext->url.toString(), ddata->lineNumber);
            expressions << ExpressionChange(name, id, expression);
        } else {
            properties << qMakePair(name, data);
        }
    }

    decoded = true;
    data.clear();
}

void QDeclarativePropertyChangesParser::setCustomData(QObject *object,
                                            const QByteArray &data)
{
    QDeclarativePropertyChangesPrivate *p =
        static_cast<QDeclarativePropertyChangesPrivate *>(QObjectPrivate::get(object));
    p->data = data;
    p->decoded = false;
}

QDeclarativePropertyChanges::QDeclarativePropertyChanges()
: QDeclarativeStateOperation(*(new QDeclarativePropertyChangesPrivate))
{
}

QDeclarativePropertyChanges::~QDeclarativePropertyChanges()
{
    Q_D(QDeclarativePropertyChanges);
    for(int ii = 0; ii < d->expressions.count(); ++ii)
        delete d->expressions.at(ii).expression;
    for(int ii = 0; ii < d->signalReplacements.count(); ++ii)
        delete d->signalReplacements.at(ii);
}

QObject *QDeclarativePropertyChanges::object() const
{
    Q_D(const QDeclarativePropertyChanges);
    return d->object;
}

void QDeclarativePropertyChanges::setObject(QObject *o)
{
    Q_D(QDeclarativePropertyChanges);
    d->object = o;
}

/*!
    \qmlproperty bool PropertyChanges::restoreEntryValues

    This property holds whether the previous values should be restored when
    leaving the state.

    The default value is \c true. Setting this value to \c false creates a
    temporary state that has permanent effects on property values.
*/
bool QDeclarativePropertyChanges::restoreEntryValues() const
{
    Q_D(const QDeclarativePropertyChanges);
    return d->restore;
}

void QDeclarativePropertyChanges::setRestoreEntryValues(bool v)
{
    Q_D(QDeclarativePropertyChanges);
    d->restore = v;
}

QDeclarativeProperty
QDeclarativePropertyChangesPrivate::property(const QString &property)
{
    Q_Q(QDeclarativePropertyChanges);
    QDeclarativeProperty prop(object, property, qmlContext(q));
    if (!prop.isValid()) {
        qmlInfo(q) << QDeclarativePropertyChanges::tr("Cannot assign to non-existent property \"%1\"").arg(property);
        return QDeclarativeProperty();
    } else if (!(prop.type() & QDeclarativeProperty::SignalProperty) && !prop.isWritable()) {
        qmlInfo(q) << QDeclarativePropertyChanges::tr("Cannot assign to read-only property \"%1\"").arg(property);
        return QDeclarativeProperty();
    }
    return prop;
}

QDeclarativePropertyChanges::ActionList QDeclarativePropertyChanges::actions()
{
    Q_D(QDeclarativePropertyChanges);

    d->decode();

    ActionList list;

    for (int ii = 0; ii < d->properties.count(); ++ii) {

        QDeclarativeAction a(d->object, d->properties.at(ii).first,
                 qmlContext(this), d->properties.at(ii).second);

        if (a.property.isValid()) {
            a.restore = restoreEntryValues();
            list << a;
        }
    }

    for (int ii = 0; ii < d->signalReplacements.count(); ++ii) {

        QDeclarativeReplaceSignalHandler *handler = d->signalReplacements.at(ii);

        if (handler->property.isValid()) {
            QDeclarativeAction a;
            a.event = handler;
            list << a;
        }
    }

    for (int ii = 0; ii < d->expressions.count(); ++ii) {

        const QString &property = d->expressions.at(ii).name;
        QDeclarativeProperty prop = d->property(property);

        if (prop.isValid()) {
            QDeclarativeAction a;
            a.restore = restoreEntryValues();
            a.property = prop;
            a.fromValue = a.property.read();
            a.specifiedObject = d->object;
            a.specifiedProperty = property;

            if (d->isExplicit) {
                a.toValue = d->expressions.at(ii).expression->evaluate();
            } else {
                QDeclarativeExpression *e = d->expressions.at(ii).expression;

                QDeclarativeBinding::Identifier id = d->expressions.at(ii).id;
                QDeclarativeBinding *newBinding = id != QDeclarativeBinding::Invalid ? QDeclarativeBinding::createBinding(id, object(), qmlContext(this), e->sourceFile(), e->lineNumber()) : 0;
                if (!newBinding) {
                    newBinding = new QDeclarativeBinding(e->expression(), object(), qmlContext(this));
                    newBinding->setSourceLocation(e->sourceFile(), e->lineNumber());
                }
                newBinding->setTarget(prop);
                a.toBinding = QDeclarativeAbstractBinding::getPointer(newBinding);
                a.deletableToBinding = true;
            }

            list << a;
        }
    }

    return list;
}

/*!
    \qmlproperty bool PropertyChanges::explicit

    If explicit is set to true, any potential bindings will be interpreted as
    once-off assignments that occur when the state is entered.

    In the following example, the addition of explicit prevents \c myItem.width from
    being bound to \c parent.width. Instead, it is assigned the value of \c parent.width
    at the time of the state change.
    \qml
    PropertyChanges {
        target: myItem
        explicit: true
        width: parent.width
    }
    \endqml

    By default, explicit is false.
*/
bool QDeclarativePropertyChanges::isExplicit() const
{
    Q_D(const QDeclarativePropertyChanges);
    return d->isExplicit;
}

void QDeclarativePropertyChanges::setIsExplicit(bool e)
{
    Q_D(QDeclarativePropertyChanges);
    d->isExplicit = e;
}

bool QDeclarativePropertyChanges::containsValue(const QString &name) const
{
    Q_D(const QDeclarativePropertyChanges);
    typedef QPair<QString, QVariant> PropertyEntry;

    QListIterator<PropertyEntry> propertyIterator(d->properties);
    while (propertyIterator.hasNext()) {
        const PropertyEntry &entry = propertyIterator.next();
        if (entry.first == name) {
            return true;
        }
    }

    return false;
}

bool QDeclarativePropertyChanges::containsExpression(const QString &name) const
{
    Q_D(const QDeclarativePropertyChanges);
    typedef QDeclarativePropertyChangesPrivate::ExpressionChange ExpressionEntry;

    QListIterator<ExpressionEntry> expressionIterator(d->expressions);
    while (expressionIterator.hasNext()) {
        const ExpressionEntry &entry = expressionIterator.next();
        if (entry.name == name) {
            return true;
        }
    }

    return false;
}

bool QDeclarativePropertyChanges::containsProperty(const QString &name) const
{
    return containsValue(name) || containsExpression(name);
}

void QDeclarativePropertyChanges::changeValue(const QString &name, const QVariant &value)
{
    Q_D(QDeclarativePropertyChanges);
    typedef QPair<QString, QVariant> PropertyEntry;
    typedef QDeclarativePropertyChangesPrivate::ExpressionChange ExpressionEntry;

    QMutableListIterator<ExpressionEntry> expressionIterator(d->expressions);
    while (expressionIterator.hasNext()) {
        const ExpressionEntry &entry = expressionIterator.next();
        if (entry.name == name) {
            expressionIterator.remove();
            if (state() && state()->isStateActive()) {
                QDeclarativeAbstractBinding *oldBinding = QDeclarativePropertyPrivate::binding(d->property(name));
                if (oldBinding) {
                    QDeclarativePropertyPrivate::setBinding(d->property(name), 0);
                    oldBinding->destroy();
                }
                d->property(name).write(value);
            }

            d->properties.append(PropertyEntry(name, value));
            return;
        }
    }

    QMutableListIterator<PropertyEntry> propertyIterator(d->properties);
    while (propertyIterator.hasNext()) {
        PropertyEntry &entry = propertyIterator.next();
        if (entry.first == name) {
            entry.second = value;
            if (state() && state()->isStateActive())
                d->property(name).write(value);
            return;
        }
    }

    QDeclarativeAction action;
    action.restore = restoreEntryValues();
    action.property = d->property(name);
    action.fromValue = action.property.read();
    action.specifiedObject = object();
    action.specifiedProperty = name;
    action.toValue = value;

    propertyIterator.insert(PropertyEntry(name, value));
    if (state() && state()->isStateActive()) {
        state()->addEntryToRevertList(action);
        QDeclarativeAbstractBinding *oldBinding = QDeclarativePropertyPrivate::binding(action.property);
        if (oldBinding)
            oldBinding->setEnabled(false, QDeclarativePropertyPrivate::DontRemoveBinding | QDeclarativePropertyPrivate::BypassInterceptor);
        d->property(name).write(value);
    }
}

void QDeclarativePropertyChanges::changeExpression(const QString &name, const QString &expression)
{
    Q_D(QDeclarativePropertyChanges);
    typedef QPair<QString, QVariant> PropertyEntry;
    typedef QDeclarativePropertyChangesPrivate::ExpressionChange ExpressionEntry;

    bool hadValue = false;

    QMutableListIterator<PropertyEntry> propertyIterator(d->properties);
    while (propertyIterator.hasNext()) {
        PropertyEntry &entry = propertyIterator.next();
        if (entry.first == name) {
            propertyIterator.remove();
            hadValue = true;
            break;
        }
    }

    QMutableListIterator<ExpressionEntry> expressionIterator(d->expressions);
    while (expressionIterator.hasNext()) {
        const ExpressionEntry &entry = expressionIterator.next();
        if (entry.name == name) {
            entry.expression->setExpression(expression);
            if (state() && state()->isStateActive()) {
                QDeclarativeAbstractBinding *oldBinding = QDeclarativePropertyPrivate::binding(d->property(name));
                if (oldBinding) {
                       QDeclarativePropertyPrivate::setBinding(d->property(name), 0);
                       oldBinding->destroy();
                }

                QDeclarativeBinding *newBinding = new QDeclarativeBinding(expression, object(), qmlContext(this));
                newBinding->setTarget(d->property(name));
                QDeclarativePropertyPrivate::setBinding(d->property(name), newBinding, QDeclarativePropertyPrivate::DontRemoveBinding | QDeclarativePropertyPrivate::BypassInterceptor);
            }
            return;
        }
    }

    QDeclarativeExpression *newExpression = new QDeclarativeExpression(qmlContext(this), d->object, expression);
    expressionIterator.insert(ExpressionEntry(name, QDeclarativeBinding::Invalid, newExpression));

    if (state() && state()->isStateActive()) {
        if (hadValue) {
            QDeclarativeAbstractBinding *oldBinding = QDeclarativePropertyPrivate::binding(d->property(name));
            if (oldBinding) {
                oldBinding->setEnabled(false, QDeclarativePropertyPrivate::DontRemoveBinding | QDeclarativePropertyPrivate::BypassInterceptor);
                state()->changeBindingInRevertList(object(), name, oldBinding);
            }

            QDeclarativeBinding *newBinding = new QDeclarativeBinding(expression, object(), qmlContext(this));
            newBinding->setTarget(d->property(name));
            QDeclarativePropertyPrivate::setBinding(d->property(name), newBinding, QDeclarativePropertyPrivate::DontRemoveBinding | QDeclarativePropertyPrivate::BypassInterceptor);
        } else {
            QDeclarativeAction action;
            action.restore = restoreEntryValues();
            action.property = d->property(name);
            action.fromValue = action.property.read();
            action.specifiedObject = object();
            action.specifiedProperty = name;


            if (d->isExplicit) {
                action.toValue = newExpression->evaluate();
            } else {
                QDeclarativeBinding *newBinding = new QDeclarativeBinding(newExpression->expression(), object(), qmlContext(this));
                newBinding->setTarget(d->property(name));
                action.toBinding = QDeclarativeAbstractBinding::getPointer(newBinding);
                action.deletableToBinding = true;

                state()->addEntryToRevertList(action);
                QDeclarativeAbstractBinding *oldBinding = QDeclarativePropertyPrivate::binding(action.property);
                if (oldBinding)
                    oldBinding->setEnabled(false, QDeclarativePropertyPrivate::DontRemoveBinding | QDeclarativePropertyPrivate::BypassInterceptor);

                QDeclarativePropertyPrivate::setBinding(action.property, newBinding, QDeclarativePropertyPrivate::DontRemoveBinding | QDeclarativePropertyPrivate::BypassInterceptor);
            }
        }
    }
    // what about the signal handler?
}

QVariant QDeclarativePropertyChanges::property(const QString &name) const
{
    Q_D(const QDeclarativePropertyChanges);
    typedef QPair<QString, QVariant> PropertyEntry;
    typedef QDeclarativePropertyChangesPrivate::ExpressionChange ExpressionEntry;

    QListIterator<PropertyEntry> propertyIterator(d->properties);
    while (propertyIterator.hasNext()) {
        const PropertyEntry &entry = propertyIterator.next();
        if (entry.first == name) {
            return entry.second;
        }
    }

    QListIterator<ExpressionEntry> expressionIterator(d->expressions);
    while (expressionIterator.hasNext()) {
        const ExpressionEntry &entry = expressionIterator.next();
        if (entry.name == name) {
            return QVariant(entry.expression->expression());
        }
    }

    return QVariant();
}

void QDeclarativePropertyChanges::removeProperty(const QString &name)
{
    Q_D(QDeclarativePropertyChanges);
    typedef QPair<QString, QVariant> PropertyEntry;
    typedef QDeclarativePropertyChangesPrivate::ExpressionChange ExpressionEntry;

    QMutableListIterator<ExpressionEntry> expressionIterator(d->expressions);
    while (expressionIterator.hasNext()) {
        const ExpressionEntry &entry = expressionIterator.next();
        if (entry.name == name) {
            expressionIterator.remove();
            state()->removeEntryFromRevertList(object(), name);
            return;
        }
    }

    QMutableListIterator<PropertyEntry> propertyIterator(d->properties);
    while (propertyIterator.hasNext()) {
        const PropertyEntry &entry = propertyIterator.next();
        if (entry.first == name) {
            propertyIterator.remove();
            state()->removeEntryFromRevertList(object(), name);
            return;
        }
    }
}

QVariant QDeclarativePropertyChanges::value(const QString &name) const
{
    Q_D(const QDeclarativePropertyChanges);
    typedef QPair<QString, QVariant> PropertyEntry;

    QListIterator<PropertyEntry> propertyIterator(d->properties);
    while (propertyIterator.hasNext()) {
        const PropertyEntry &entry = propertyIterator.next();
        if (entry.first == name) {
            return entry.second;
        }
    }

    return QVariant();
}

QString QDeclarativePropertyChanges::expression(const QString &name) const
{
    Q_D(const QDeclarativePropertyChanges);
    typedef QDeclarativePropertyChangesPrivate::ExpressionChange ExpressionEntry;

    QListIterator<ExpressionEntry> expressionIterator(d->expressions);
    while (expressionIterator.hasNext()) {
        const ExpressionEntry &entry = expressionIterator.next();
        if (entry.name == name) {
            return entry.expression->expression();
        }
    }

    return QString();
}

void QDeclarativePropertyChanges::detachFromState()
{
    if (state())
        state()->removeAllEntriesFromRevertList(object());
}

void QDeclarativePropertyChanges::attachToState()
{
    if (state())
        state()->addEntriesToRevertList(actions());
}

QT_END_NAMESPACE