source: trunk/src/declarative/qml/qdeclarativebinding.cpp

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**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtDeclarative module of the Qt Toolkit.
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** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
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** General Public License version 3.0 as published by the Free Software
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** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
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#include "private/qdeclarativebinding_p.h"
#include "private/qdeclarativebinding_p_p.h"

#include "qdeclarative.h"
#include "qdeclarativecontext.h"
#include "qdeclarativeinfo.h"
#include "private/qdeclarativecontext_p.h"
#include "private/qdeclarativedata_p.h"
#include "private/qdeclarativestringconverters_p.h"
#include "private/qdeclarativestate_p_p.h"

#include <QVariant>
#include <QtCore/qdebug.h>

QT_BEGIN_NAMESPACE

QDeclarativeAbstractBinding::QDeclarativeAbstractBinding()
: m_object(0), m_propertyIndex(-1), m_mePtr(0), m_prevBinding(0), m_nextBinding(0)
{
}

QDeclarativeAbstractBinding::~QDeclarativeAbstractBinding()
{
    Q_ASSERT(m_prevBinding == 0);
    Q_ASSERT(m_mePtr == 0);
}

/*!
Destroy the binding.  Use this instead of calling delete.

Bindings are free to implement their own memory management, so the delete operator is not 
necessarily safe.  The default implementation clears the binding, removes it from the object
and calls delete.
*/
void QDeclarativeAbstractBinding::destroy()
{
    removeFromObject();
    clear();

    delete this;
}

/*!
Add this binding to \a object.

This transfers ownership of the binding to the object, marks the object's property as
being bound.  

However, it does not enable the binding itself or call update() on it.
*/
void QDeclarativeAbstractBinding::addToObject(QObject *object, int index)
{
    Q_ASSERT(object);

    if (m_object == object && m_propertyIndex == index)
        return;

    removeFromObject();

    Q_ASSERT(!m_prevBinding);

    m_object = object;
    m_propertyIndex = index;

    QDeclarativeData *data = QDeclarativeData::get(object, true);

    if (index & 0xFF000000) {
        // Value type

        int coreIndex = index & 0xFFFFFF;

        // Find the value type proxy (if there is one)
        QDeclarativeValueTypeProxyBinding *proxy = 0;
        if (data->hasBindingBit(coreIndex)) {
            QDeclarativeAbstractBinding *b = data->bindings;
            while (b && b->propertyIndex() != coreIndex)
                b = b->m_nextBinding;
            Q_ASSERT(b && b->bindingType() == QDeclarativeAbstractBinding::ValueTypeProxy);
            proxy = static_cast<QDeclarativeValueTypeProxyBinding *>(b);
        }

        if (!proxy) {
            proxy = new QDeclarativeValueTypeProxyBinding(object, coreIndex);
            proxy->addToObject(object, coreIndex);
        }

        m_nextBinding = proxy->m_bindings;
        if (m_nextBinding) m_nextBinding->m_prevBinding = &m_nextBinding;
        m_prevBinding = &proxy->m_bindings;
        proxy->m_bindings = this;

    } else {
        m_nextBinding = data->bindings;
        if (m_nextBinding) m_nextBinding->m_prevBinding = &m_nextBinding;
        m_prevBinding = &data->bindings;
        data->bindings = this;

        data->setBindingBit(m_object, index);
    }
}

/*!
Remove the binding from the object.
*/
void QDeclarativeAbstractBinding::removeFromObject()
{
    if (m_prevBinding) {
        int index = propertyIndex();

        *m_prevBinding = m_nextBinding;
        if (m_nextBinding) m_nextBinding->m_prevBinding = m_prevBinding;
        m_prevBinding = 0;
        m_nextBinding = 0;

        if (index & 0xFF000000) {
            // Value type - we don't remove the proxy from the object.  It will sit their happily
            // doing nothing until it is removed by a write, a binding change or it is reused
            // to hold more sub-bindings.
        } else if (m_object) {
            QDeclarativeData *data = QDeclarativeData::get(m_object, false);
            if (data) data->clearBindingBit(index);
        }

        m_object = 0;
        m_propertyIndex = -1;
    }
}

static void bindingDummyDeleter(QDeclarativeAbstractBinding *)
{
}

QDeclarativeAbstractBinding::Pointer QDeclarativeAbstractBinding::weakPointer()
{
    if (m_selfPointer.isNull())
        m_selfPointer = QSharedPointer<QDeclarativeAbstractBinding>(this, bindingDummyDeleter);

    return m_selfPointer.toWeakRef();
}

void QDeclarativeAbstractBinding::clear()
{
    if (m_mePtr) {
        *m_mePtr = 0;
        m_mePtr = 0;
    }
}

QString QDeclarativeAbstractBinding::expression() const
{
    return QLatin1String("<Unknown>");
}

QObject *QDeclarativeAbstractBinding::object() const
{
    return m_object;
}

int QDeclarativeAbstractBinding::propertyIndex() const
{
    return m_propertyIndex;
}

void QDeclarativeAbstractBinding::setEnabled(bool enabled, QDeclarativePropertyPrivate::WriteFlags flags)
{
    if (enabled) update(flags);
}

void QDeclarativeBindingPrivate::refresh()
{
    Q_Q(QDeclarativeBinding);
    q->update();
}

QDeclarativeBindingPrivate::QDeclarativeBindingPrivate()
: updating(false), enabled(false), deleted(0)
{
}

QDeclarativeBindingPrivate::~QDeclarativeBindingPrivate()
{
    if (deleted) *deleted = true;
}

QDeclarativeBinding::QDeclarativeBinding(void *data, QDeclarativeRefCount *rc, QObject *obj, 
                                         QDeclarativeContextData *ctxt, const QString &url, int lineNumber, 
                                         QObject *parent)
: QDeclarativeExpression(ctxt, data, rc, obj, url, lineNumber, *new QDeclarativeBindingPrivate)
{
    setParent(parent);
    setNotifyOnValueChanged(true);
}

QDeclarativeBinding::QDeclarativeBinding(const QString &str, QObject *obj, QDeclarativeContext *ctxt, 
                                         QObject *parent)
: QDeclarativeExpression(QDeclarativeContextData::get(ctxt), obj, str, *new QDeclarativeBindingPrivate)
{
    setParent(parent);
    setNotifyOnValueChanged(true);
}

QDeclarativeBinding::QDeclarativeBinding(const QString &str, QObject *obj, QDeclarativeContextData *ctxt, 
                                         QObject *parent)
: QDeclarativeExpression(ctxt, obj, str, *new QDeclarativeBindingPrivate)
{
    setParent(parent);
    setNotifyOnValueChanged(true);
}

QDeclarativeBinding::~QDeclarativeBinding()
{
}

void QDeclarativeBinding::setTarget(const QDeclarativeProperty &prop)
{
    Q_D(QDeclarativeBinding);
    d->property = prop;

    update();
}

QDeclarativeProperty QDeclarativeBinding::property() const 
{
   Q_D(const QDeclarativeBinding);
   return d->property; 
}

void QDeclarativeBinding::update(QDeclarativePropertyPrivate::WriteFlags flags)
{
    Q_D(QDeclarativeBinding);

    if (!d->enabled || !d->context() || !d->context()->isValid()) 
        return;

    if (!d->updating) {
        d->updating = true;
        bool wasDeleted = false;
        d->deleted = &wasDeleted;

        if (d->property.propertyType() == qMetaTypeId<QDeclarativeBinding *>()) {

            int idx = d->property.index();
            Q_ASSERT(idx != -1);

            QDeclarativeBinding *t = this;
            int status = -1;
            void *a[] = { &t, 0, &status, &flags };
            QMetaObject::metacall(d->property.object(),
                                  QMetaObject::WriteProperty,
                                  idx, a);

            if (wasDeleted)
                return;

        } else {
            QDeclarativeEnginePrivate *ep = QDeclarativeEnginePrivate::get(d->context()->engine);

            bool isUndefined = false;
            QVariant value;

            QScriptValue scriptValue = d->scriptValue(0, &isUndefined);
            if (wasDeleted)
                return;

            if (d->property.propertyTypeCategory() == QDeclarativeProperty::List) {
                value = ep->scriptValueToVariant(scriptValue, qMetaTypeId<QList<QObject *> >());
            } else if (scriptValue.isNull() && 
                       d->property.propertyTypeCategory() == QDeclarativeProperty::Object) {
                value = QVariant::fromValue((QObject *)0);
            } else {
                value = ep->scriptValueToVariant(scriptValue, d->property.propertyType());
                if (value.userType() == QMetaType::QObjectStar && !qvariant_cast<QObject*>(value)) {
                    // If the object is null, we extract the predicted type.  While this isn't
                    // 100% reliable, in many cases it gives us better error messages if we
                    // assign this null-object to an incompatible property
                    int type = ep->objectClass->objectType(scriptValue);
                    QObject *o = 0;
                    value = QVariant(type, (void *)&o);
                }
            }


            if (d->error.isValid()) {

            } else if (isUndefined && d->property.isResettable()) {

                d->property.reset();

            } else if (isUndefined && d->property.propertyType() == qMetaTypeId<QVariant>()) {

                QDeclarativePropertyPrivate::write(d->property, QVariant(), flags);

            } else if (isUndefined) {

                QUrl url = QUrl(d->url);
                int line = d->line;
                if (url.isEmpty()) url = QUrl(QLatin1String("<Unknown File>"));

                d->error.setUrl(url);
                d->error.setLine(line);
                d->error.setColumn(-1);
                d->error.setDescription(QLatin1String("Unable to assign [undefined] to ") +
                                        QLatin1String(QMetaType::typeName(d->property.propertyType())) +
                                        QLatin1String(" ") + d->property.name());

            } else if (!scriptValue.isRegExp() && scriptValue.isFunction()) {

                QUrl url = QUrl(d->url);
                int line = d->line;
                if (url.isEmpty()) url = QUrl(QLatin1String("<Unknown File>"));

                d->error.setUrl(url);
                d->error.setLine(line);
                d->error.setColumn(-1);
                d->error.setDescription(QLatin1String("Unable to assign a function to a property."));

            } else if (d->property.object() &&
                       !QDeclarativePropertyPrivate::write(d->property, value, flags)) {

                if (wasDeleted)
                    return;

                QUrl url = QUrl(d->url);
                int line = d->line;
                if (url.isEmpty()) url = QUrl(QLatin1String("<Unknown File>"));

                const char *valueType = 0;
                if (value.userType() == QVariant::Invalid) valueType = "null";
                else valueType = QMetaType::typeName(value.userType());

                d->error.setUrl(url);
                d->error.setLine(line);
                d->error.setColumn(-1);
                d->error.setDescription(QLatin1String("Unable to assign ") +
                                        QLatin1String(valueType) +
                                        QLatin1String(" to ") +
                                        QLatin1String(QMetaType::typeName(d->property.propertyType())));
            }

            if (wasDeleted)
                return;

            if (d->error.isValid()) {
               if (!d->addError(ep)) ep->warning(this->error());
            } else {
                d->removeError();
            }
        }

        d->updating = false;
        d->deleted = 0;
    } else {
        qmlInfo(d->property.object()) << tr("Binding loop detected for property \"%1\"").arg(d->property.name());
    }
}

void QDeclarativeBindingPrivate::emitValueChanged()
{
    Q_Q(QDeclarativeBinding);
    q->update();
}

void QDeclarativeBinding::setEnabled(bool e, QDeclarativePropertyPrivate::WriteFlags flags)
{
    Q_D(QDeclarativeBinding);
    d->enabled = e;
    setNotifyOnValueChanged(e);

    if (e) 
        update(flags);
}

bool QDeclarativeBinding::enabled() const
{
    Q_D(const QDeclarativeBinding);

    return d->enabled;
}

QString QDeclarativeBinding::expression() const
{
    return QDeclarativeExpression::expression();
}

QDeclarativeValueTypeProxyBinding::QDeclarativeValueTypeProxyBinding(QObject *o, int index)
: m_object(o), m_index(index), m_bindings(0)
{
}

QDeclarativeValueTypeProxyBinding::~QDeclarativeValueTypeProxyBinding()
{
    while (m_bindings) {
        QDeclarativeAbstractBinding *binding = m_bindings;
        binding->setEnabled(false, 0);
        binding->destroy();
    }
}

void QDeclarativeValueTypeProxyBinding::setEnabled(bool e, QDeclarativePropertyPrivate::WriteFlags flags)
{
    if (e) {
        QDeclarativeAbstractBinding *bindings = m_bindings;
        recursiveEnable(bindings, flags);
    } else {
        QDeclarativeAbstractBinding *bindings = m_bindings;
        recursiveDisable(bindings);
    }
}

void QDeclarativeValueTypeProxyBinding::recursiveEnable(QDeclarativeAbstractBinding *b, QDeclarativePropertyPrivate::WriteFlags flags)
{
    if (!b)
        return;

    recursiveEnable(b->m_nextBinding, flags);

    if (b)
        b->setEnabled(true, flags);
}

void QDeclarativeValueTypeProxyBinding::recursiveDisable(QDeclarativeAbstractBinding *b)
{
    if (!b)
        return;

    recursiveDisable(b->m_nextBinding);

    if (b)
        b->setEnabled(false, 0);
}

void QDeclarativeValueTypeProxyBinding::update(QDeclarativePropertyPrivate::WriteFlags)
{
}

QDeclarativeAbstractBinding *QDeclarativeValueTypeProxyBinding::binding(int propertyIndex)
{
    QDeclarativeAbstractBinding *binding = m_bindings;
    
    while (binding && binding->propertyIndex() != propertyIndex) 
        binding = binding->m_nextBinding;

    return binding;
}

/*!
Removes a collection of bindings, corresponding to the set bits in \a mask.
*/
void QDeclarativeValueTypeProxyBinding::removeBindings(quint32 mask)
{
    QDeclarativeAbstractBinding *binding = m_bindings;
    while (binding) {
        if (mask & (1 << (binding->propertyIndex() >> 24))) {
            QDeclarativeAbstractBinding *remove = binding;
            binding = remove->m_nextBinding;
            *remove->m_prevBinding = remove->m_nextBinding;
            if (remove->m_nextBinding) remove->m_nextBinding->m_prevBinding = remove->m_prevBinding;
            remove->m_prevBinding = 0;
            remove->m_nextBinding = 0;
            remove->destroy();
        } else {
            binding = binding->m_nextBinding;
        }
    }
}

QT_END_NAMESPACE