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+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
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+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** GNU Lesser General Public License Usage
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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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+** additional rights. These rights are described in the Nokia Qt LGPL
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+** GNU General Public License Usage
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+****************************************************************************/
+
+/*!
+\page objecttrees.html
+\title Object Trees and Object Ownership
+\ingroup architecture
+\brief Information about the parent-child pattern used to describe
+object ownership in Qt.
+
+\section1 Overview
+
+\link QObject QObjects\endlink organize themselves in object trees.
+When you create a QObject with another object as parent, it's added to
+the parent's \link QObject::children() children() \endlink list, and
+is deleted when the parent is. It turns out that this approach fits
+the needs of GUI objects very well. For example, a \l QShortcut
+(keyboard shortcut) is a child of the relevant window, so when the
+user closes that window, the shorcut is deleted too.
+
+\l QWidget, the base class of everything that appears on the screen,
+extends the parent-child relationship. A child normally also becomes a
+child widget, i.e. it is displayed in its parent's coordinate system
+and is graphically clipped by its parent's boundaries. For example,
+when the application deletes a message box after it has been
+closed, the message box's buttons and label are also deleted, just as
+we'd want, because the buttons and label are children of the message
+box.
+
+You can also delete child objects yourself, and they will remove
+themselves from their parents. For example, when the user removes a
+toolbar it may lead to the application deleting one of its \l QToolBar
+objects, in which case the tool bar's \l QMainWindow parent would
+detect the change and reconfigure its screen space accordingly.
+
+The debugging functions \l QObject::dumpObjectTree() and \l
+QObject::dumpObjectInfo() are often useful when an application looks or
+acts strangely.
+
+\target note on the order of construction/destruction of QObjects
+\section1 Construction/Destruction Order of QObjects
+
+When \l {QObject} {QObjects} are created on the heap (i.e., created
+with \e new), a tree can be constructed from them in any order, and
+later, the objects in the tree can be destroyed in any order. When any
+QObject in the tree is deleted, if the object has a parent, the
+destructor automatically removes the object from its parent. If the
+object has children, the destructor automatically deletes each
+child. No QObject is deleted twice, regardless of the order of
+destruction.
+
+When \l {QObject} {QObjects} are created on the stack, the same
+behavior applies. Normally, the order of destruction still doesn't
+present a problem. Consider the following snippet:
+
+\snippet doc/src/snippets/code/doc_src_objecttrees.qdoc 0
+
+The parent, \c window, and the child, \c quit, are both \l {QObject}
+{QObjects} because QPushButton inherits QWidget, and QWidget inherits
+QObject. This code is correct: the destructor of \c quit is \e not
+called twice because the C++ language standard \e {(ISO/IEC 14882:2003)}
+specifies that destructors of local objects are called in the reverse
+order of their constructors. Therefore, the destructor of
+the child, \c quit, is called first, and it removes itself from its
+parent, \c window, before the destructor of \c window is called.
+
+But now consider what happens if we swap the order of construction, as
+shown in this second snippet:
+
+\snippet doc/src/snippets/code/doc_src_objecttrees.qdoc 1
+
+In this case, the order of destruction causes a problem. The parent's
+destructor is called first because it was created last. It then calls
+the destructor of its child, \c quit, which is incorrect because \c
+quit is a local variable. When \c quit subsequently goes out of scope,
+its destructor is called again, this time correctly, but the damage has
+already been done.
+
+*/