qqmlmetaobject_p.h

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// Copyright (C) 2019 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
 
#ifndef QQMLMETAOBJECT_P_H
#define QQMLMETAOBJECT_P_H
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
 
#include <private/qqmlpropertycache_p.h>
 
#include <QtQml/qtqmlglobal.h>
#include <QtCore/qvarlengtharray.h>
#include <QtCore/qmetaobject.h>
 
QT_BEGIN_NAMESPACE
 
// QQmlMetaObject serves as a wrapper around either QMetaObject or QQmlPropertyCache.
// This is necessary as we delay creation of QMetaObject for synthesized QObjects, but
// we don't want to needlessly generate QQmlPropertyCaches every time we encounter a
// QObject type used in assignment or when we don't have a QQmlEngine etc.
//
// This class does NOT reference the propertycache.
class QQmlEnginePrivate;
class QQmlPropertyData;
class Q_QML_EXPORT QQmlMetaObject
{
public:
    template<qsizetype Prealloc>
    using ArgTypeStorage = QVarLengthArray<QMetaType, Prealloc>;
 
    inline QQmlMetaObject() = default;
    inline QQmlMetaObject(const QObject *);
    inline QQmlMetaObject(const QMetaObject *);
    inline QQmlMetaObject(const QQmlPropertyCache::ConstPtr &);
    inline QQmlMetaObject(const QQmlMetaObject &);
 
    inline QQmlMetaObject &operator=(const QQmlMetaObject &);
 
    inline bool isNull() const;
 
    inline const char *className() const;
    inline int propertyCount() const;
 
    inline const QMetaObject *metaObject() const;
 
    QMetaType methodReturnType(const QQmlPropertyData &data, QByteArray *unknownTypeError) const;
 
    template<typename ArgTypeStorage>
    bool methodParameterTypes(
            int index, ArgTypeStorage *argStorage, QByteArray *unknownTypeError) const
    {
        Q_ASSERT(_m && index >= 0);
 
        QMetaMethod m = _m->method(index);
        return methodParameterTypes(m, argStorage, unknownTypeError);
    }
 
    template<typename ArgTypeStorage>
    bool constructorParameterTypes(
            int index, ArgTypeStorage *dummy, QByteArray *unknownTypeError) const
    {
        QMetaMethod m = _m->constructor(index);
        return methodParameterTypes(m, dummy, unknownTypeError);
    }
 
 
    static bool canConvert(const QQmlMetaObject &from, const QQmlMetaObject &to)
    {
        Q_ASSERT(!from.isNull() && !to.isNull());
        return from.metaObject()->inherits(to.metaObject());
    }
 
    // static_metacall (on Gadgets) doesn't call the base implementation and therefore
    // we need a helper to find the correct meta object and property/method index.
    static void resolveGadgetMethodOrPropertyIndex(
            QMetaObject::Call type, const QMetaObject **metaObject, int *index);
 
    template<typename ArgTypeStorage>
    static bool methodParameterTypes(
            const QMetaMethod &method, ArgTypeStorage *argStorage, QByteArray *unknownTypeError)
    {
        Q_ASSERT(argStorage);
 
        const int argc = method.parameterCount();
        argStorage->resize(argc);
        for (int ii = 0; ii < argc; ++ii) {
            if (!parameterType(method, ii, unknownTypeError, [argStorage](int ii, QMetaType &&type) {
                    argStorage->operator[](ii) = std::forward<QMetaType>(type);
                })) {
                return false;
            }
        }
        return true;
    }
 
    template<typename ArgTypeStorage>
    static bool methodReturnAndParameterTypes(
            const QMetaMethod &method, ArgTypeStorage *argStorage, QByteArray *unknownTypeError)
    {
        Q_ASSERT(argStorage);
 
        const int argc = method.parameterCount();
        argStorage->resize(argc + 1);
 
        QMetaType type = method.returnMetaType();
        if (type.flags().testFlag(QMetaType::IsEnumeration))
            type = type.underlyingType();
 
        if (!type.isValid()) {
            if (unknownTypeError)
                *unknownTypeError = "return type";
            return false;
        }
 
        argStorage->operator[](0) = type;
 
        for (int ii = 0; ii < argc; ++ii) {
            if (!parameterType(
                        method, ii, unknownTypeError, [argStorage](int ii, QMetaType &&type) {
                    argStorage->operator[](ii + 1) = std::forward<QMetaType>(type);
                })) {
                return false;
            }
        }
 
        return true;
    }
 
protected:
    template<typename Store>
    static bool parameterType(
            const QMetaMethod &method, int ii, QByteArray *unknownTypeError, const Store &store)
    {
        QMetaType type = method.parameterMetaType(ii);
 
               // we treat enumerations as their underlying type
        if (type.flags().testFlag(QMetaType::IsEnumeration))
            type = type.underlyingType();
 
        if (!type.isValid()) {
            if (unknownTypeError)
                *unknownTypeError =  method.parameterTypeName(ii);
            return false;
        }
 
        store(ii, std::move(type));
        return true;
    }
 
 
    const QMetaObject *_m = nullptr;
 
};
 
QQmlMetaObject::QQmlMetaObject(const QObject *o)
{
    if (o)
        _m = o->metaObject();
}
 
QQmlMetaObject::QQmlMetaObject(const QMetaObject *m)
    : _m(m)
{
}
 
QQmlMetaObject::QQmlMetaObject(const QQmlPropertyCache::ConstPtr &m)
{
    if (m)
        _m = m->createMetaObject();
}
 
QQmlMetaObject::QQmlMetaObject(const QQmlMetaObject &o)
    : _m(o._m)
{
}
 
QQmlMetaObject &QQmlMetaObject::operator=(const QQmlMetaObject &o)
{
    _m = o._m;
    return *this;
}
 
bool QQmlMetaObject::isNull() const
{
    return !_m;
}
 
const char *QQmlMetaObject::className() const
{
    if (!_m)
        return nullptr;
    return metaObject()->className();
}
 
int QQmlMetaObject::propertyCount() const
{
    if (!_m)
        return 0;
    return metaObject()->propertyCount();
}
 
const QMetaObject *QQmlMetaObject::metaObject() const
{
    return _m;
}
 
QT_END_NAMESPACE
 
#endif // QQMLMETAOBJECT_P_H