1 /****************************************************************************
3 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
4 ** Contact: http://www.qt-project.org/
6 ** This file is part of the QtQml module of the Qt Toolkit.
8 ** $QT_BEGIN_LICENSE:LGPL$
9 ** GNU Lesser General Public License Usage
10 ** This file may be used under the terms of the GNU Lesser General Public
11 ** License version 2.1 as published by the Free Software Foundation and
12 ** appearing in the file LICENSE.LGPL included in the packaging of this
13 ** file. Please review the following information to ensure the GNU Lesser
14 ** General Public License version 2.1 requirements will be met:
15 ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
17 ** In addition, as a special exception, Nokia gives you certain additional
18 ** rights. These rights are described in the Nokia Qt LGPL Exception
19 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
21 ** GNU General Public License Usage
22 ** Alternatively, this file may be used under the terms of the GNU General
23 ** Public License version 3.0 as published by the Free Software Foundation
24 ** and appearing in the file LICENSE.GPL included in the packaging of this
25 ** file. Please review the following information to ensure the GNU General
26 ** Public License version 3.0 requirements will be met:
27 ** http://www.gnu.org/copyleft/gpl.html.
30 ** Alternatively, this file may be used in accordance with the terms and
31 ** conditions contained in a signed written agreement between you and Nokia.
40 ****************************************************************************/
42 #include "qqmlparserstatus.h"
47 \class QQmlParserStatus
50 \brief The QQmlParserStatus class provides updates on the QML parser state.
52 QQmlParserStatus provides a mechanism for classes instantiated by
53 a QQmlEngine to receive notification at key points in their creation.
55 This class is often used for optimization purposes, as it allows you to defer an
56 expensive operation until after all the properties have been set on an
57 object. For example, QML's \l {Text} element uses the parser status
58 to defer text layout until all of its properties have been set (we
59 don't want to layout when the \c text is assigned, and then relayout
60 when the \c font is assigned, and relayout again when the \c width is assigned,
63 Be aware that QQmlParserStatus methods are only called when a class is instantiated
64 by a QQmlEngine. If you create the same class directly from C++, these methods will
65 not be called automatically. To avoid this problem, it is recommended that you start
66 deferring operations from classBegin instead of from the initial creation of your class.
67 This will still prevent multiple revaluations during initial binding assignment in QML,
68 but will not defer operations invoked from C++.
70 To use QQmlParserStatus, you must inherit both a QObject-derived class
71 and QQmlParserStatus, and use the Q_INTERFACES() macro.
74 class MyObject : public QObject, public QQmlParserStatus
77 Q_INTERFACES(QQmlParserStatus)
80 MyObject(QObject *parent = 0);
83 void componentComplete();
87 The QtQuick 1.0 version of this class is named QDeclarativeParserStatus.
91 QQmlParserStatus::QQmlParserStatus()
97 QQmlParserStatus::~QQmlParserStatus()
104 \fn void QQmlParserStatus::classBegin()
106 Invoked after class creation, but before any properties have been set.
110 \fn void QQmlParserStatus::componentComplete()
112 Invoked after the root component that caused this instantiation has
113 completed construction. At this point all static values and binding values
114 have been assigned to the class.