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+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** 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
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+/*!
+\group porting
+\title Porting Guides
+\brief Guides related to porting Qt applications and libraries.
+\ingroup best-practices
+A number of guides and documents are available that cover porting issues,
+from detailed coverage of API differences between Qt 3 and Qt 4 to
+platform and tool-specific documentation.
+\generatelist{related}
+*/
+/*!
+\page porting4.html
+\title Porting to Qt 4
+\contentspage {Porting Guides}{Contents}
+\previouspage Porting Guides
+\nextpage Porting to Qt 4 - Virtual Functions
+\ingroup porting
+\brief An overview of issues and techniques to consider when porting from Qt 3 to Qt 4.
+\omit
+### QFileInfo::PermissionSpec -> QFile::Permission(s?)
+### refer to porting4-renamedfunctions.qdoc
+### QApplication library mutex is gone
+### no integral conversion for containers? strings?
+### QVector etc. are initialized to 0 by default?
+### How to port from Qt 2.3 to Qt 4.
+### missing sort() functions?
+### QToolTipGroup
+### QServerSocket -> Q3ServerSocket
+### remove these when the classes are re-ported
+### QApplication::eventLoop()
+\row \o void QCheckListItem::paintCell(QPainter *, const QColorGroup &, int, int, int)\row \o void Q3CheckListItem::paintCell(QPainter *, const QPalette &, int, int, int)
+\row \o void QCheckListItem::paintFocus(QPainter *, const QColorGroup &, const QRect &) \o void Q3CheckListItem::paintFocus(QPainter *, const QPalette &, const QRect &)
+\row \o QDataTable: a whole bunch of virtual functions have a different signature
+<     Function: void QIconViewItem::paintFocus(QPainter *, const QColorGroup &)
+>     Function: void QIconViewItem::paintFocus(QPainter *, const QPalette &)
+<     Function: void QIconViewItem::paintItem(QPainter *, const QColorGroup &)
+>     Function: void QIconViewItem::paintItem(QPainter *, const QPalette &)
+<     Function: bool QUrlOperator::checkValid()
+<     Function: void QWSInputMethod::setFont(const QFont &)
+### OpenMode or OpenMode
+### QWSDecoration
+\endomit
+This document describes the process of porting applications from
+Qt 3 to Qt 4.
+If you haven't yet made the decision about porting, or are unsure
+about whether it is worth it, take a look at the \l{What's New in
+Qt 4}{key features} offered by Qt 4. See also
+\l{Moving from Qt 3 to Qt 4} for tips on how to write Qt 3 code
+that is easy to port to Qt 4.
+\bold{Other porting guides:}
+\list
+\o \l{Moving from Qt 3 to Qt 4} \mdash covers some high level topics relevant
+to developers porting from Qt 3 to Qt 4.
+\o \l{Porting to Qt 4 - Drag and Drop} \mdash covers differences in the
+way drag and drop is handled between Qt 3 and Qt 4.
+\o \l{Porting UI Files to Qt 4} \mdash describes the new format used to
+describe forms created with \QD.
+\o \l{Porting to Graphics View} \mdash provides a class-by-class overview
+of the differences between Qt 3's canvas API and Qt 4's Graphics
+View framework.
+\o \l{qt3to4 - The Qt 3 to 4 Porting Tool} \mdash provides an overview
+of a tool aimed at helping developers start the process of porting an
+application to Qt 4.
+\endlist
+The Qt 4 series is not binary compatible with the 3 series. This
+means programs compiled for Qt 3 must be recompiled to work with
+Qt 4. Qt 4 is also not completely \e source compatible with 3,
+however nearly all points of incompatibility cause compiler
+errors or run-time messages (rather than mysterious results). Qt
+4 includes many additional features and discards obsolete
+functionality. Porting from Qt 3 to Qt 4 requires some effort,
+but once completed the considerable additional power and
+flexibility of Qt 4 is available for use in your applications.
+To port code from Qt 3 to Qt 4:
+\list 1
+\o Briefly read the porting notes below to get an idea of what to expect.
+\o Be sure that your code compiles and runs well on all your target
+platforms with Qt 3.
+\o Add the line \c{QT += qt3support} to your \c .pro file if you use
+\c qmake; otherwise, edit your makefile or project file to
+link against the Qt3Support library and add \c -DQT3_SUPPORT to your
+compiler flags. (You might also need to specify other
+libraries. See \l{What's New in Qt 4} for details.)
+\o Run the \l qt3to4 porting tool. The tool will go through your
+source code and adapt it to Qt 4.
+\o Follow the instructions in the \l{Porting UI Files to Qt 4}
+page to port Qt Designer files.
+\o Recompile with Qt 4. For each error, search below for related
+identifiers (e.g., function names, class names). This document
+mentions all relevant identifiers to help you get the information
+you need at the cost of being a little verbose.
+\endlist
+The \l qt3to4 porting tool replaces occurrences of Qt 3 classes
+that don't exist anymore in Qt 4 with the corresponding Qt 3
+support class; for example, \c QListBox is turned into \c
+Q3ListBox.
+At some point, you might want to stop linking against the Qt 3
+support library (\l{Qt3Support}) and take advantage of Qt 4's
+new features. The instructions below explain how to do that for
+each compatibility class.
+In addition to the Qt3Support classes (such as \c Q3Action, \c
+Q3ListBox, and \c Q3ValueList), Qt 4 provides compatibility
+functions when it's possible for an old API to cohabit with the
+new one. For example, QString provides a
+QString::simplifyWhiteSpace() compatibility function that's
+implemented inline and that simply calls QString::simplified().
+\bold{The compatibility functions are not documented here; instead,
+they are documented for each class.}
+If you have the line \c{QT += qt3support} in your \c .pro file, \c
+qmake will automatically define the \c QT3_SUPPORT symbol, turning
+on compatibility function support. You can also define the symbol
+manually (e.g., if you don't want to link against the \c
+Qt3Support library), or you can define \c QT3_SUPPORT_WARNINGS
+instead, telling the compiler to emit a warning when a
+compatibility function is called. (This works only with GCC 3.2+
+and MSVC 7.)
+If you get stuck, ask on the
+\l{http://qt.nokia.com/lists/qt-interest/}{qt-interest}
+mailing list. If you are a licensed customer, you can also contact
+Qt's technical support team.
+\omit
+### what to do with slots that aren't slots anymore
+### what to do with virtual functions that aren't virtual anymore
+### what to do with virtual functions that changed signature
+\endomit
+\omit
+### <qtl.h> -- stuff that vanished?
+### implicit sharing
+### uint -> int indexes
+\endomit
+Table of contents:
+\tableofcontents{4}
+\omit
+\section1 Header Files
+### New style of headers
+\table
+\header \o Old header \o New header
+\row \o \c{<qtl.h>} \o \c{<qalgorithms.h>} or \c{<QtAlgorithms>}
+\endtable
+### Some headers don't include each other anymore...
+\endomit
+\section1 Casting and Object Types
+In Qt 3, it was possible to use the \c qt_cast() function to determine
+whether instances of QObject subclasses could be safely cast to derived
+types of those subclasses. For example, if a QFrame instance is passed
+to a function whose signature specifies a QWidget pointer as its argument,
+\c qt_cast() could be used to obtain a QFrame pointer so that the
+instance's functions can be accessed.
+In Qt 4, much of this functionality is provided by the qobject_cast()
+function, and additional functions also provide similar functionality for
+certain non-QObject types:
+\table
+\header \o Qt 3 function \o Qt 4 function
+\row    \o T *qt_cast<T *>(QObject *) \o \l{qobject_cast()}{T *qobject_cast<T *>(QObject *)}
+\row    \o                            \o \l{qgraphicsitem_cast()}{T qgraphicsitem_cast<T>(QGraphicsItem *)}
+\row    \o                            \o \l{qstyleoption_cast()}{T qstyleoption_cast<T>(QStyleOption *)}
+\row    \o                            \o \l{qvariant_cast()}{T qvariant_cast<T>(const QVariant &)}
+\row    \o                            \o \l{qdbus_cast()}{T qdbus_cast(const QDBusArgument &)}
+\endtable
+\omit
+\section1 Global Functions
+\table
+\header \o Qt 3 function \o Qt 4 function
+\row \o cstrcmp() \o strcmp()
+\row \o cstrcpy() \o strcpy()
+\row \o cstrlen() \o strlen()
+\row \o cstrncmp() \o strncmp()
+\row \o qmemmove() \o memmove()
+\endtable
+qGLVersion() ###
+copyBlt() ###
+bitBlt()
+#ifdef compat classes:
+* QLayoutIterator
+* QColorGroup
+* QMenuItem
+QWidget visibleRect property compat
+QWidget::BackgroundOrigin compat
+\endomit
+\section1 Type Names
+The table below lists the classes that have been renamed in Qt 4.
+If you compile your applications with \c QT3_SUPPORT defined, the
+old names will be available.
+Whenever you see an occurrence of the name on the left, you can
+safely replace it with the Qt 4 equivalent in your program. The
+\l qt3to4 tool performs the conversion automatically.
+\table
+\header \o Qt 3 class name \o Qt 4 class name
+\input porting/porting4-renamedclasses.qdocinc
+\endtable
+The table below lists the enums and typedefs that have been
+renamed in Qt 4. If you compile your applications with \c
+QT3_SUPPORT defined, the old names will be available.
+Whenever you see an occurrence of the name on the left, you can
+safely replace it with the Qt 4 equivalent in your program. The
+\l qt3to4 tool performs the conversion
+automatically.
+\table
+\header \o Qt 3 type name \o Qt 4 type name
+\input porting/porting4-renamedtypes.qdocinc
+\endtable
+\omit
+###
+\row \o QButton::ToggleState \o Use QCheckBox::ToggleState instead.
+\endomit
+\section1 Enum Values
+The table below lists the enum values that have been renamed in
+Qt 4. If you compile your applications with \c QT3_SUPPORT defined,
+the old names will be available.
+Whenever you see an occurrence of the name on the left, you can
+safely replace it with the Qt 4 equivalent in your program. The
+\l qt3to4 tool performs the conversion automatically.
+\table
+\header \o Qt 3 enum value name \o Qt 4 enum value name
+\input porting/porting4-renamedenumvalues.qdocinc
+\endtable
+In addition, the following \l{Qt::WindowFlags}{window flags} have
+been either replaced with \l{Qt::WidgetAttribute}{widget
+attributes} or have been deprecated:
+\table
+\header \o Qt 3 type \o Qt 4 equivalent
+\row \o Qt::WDestructiveClose \o Use QWidget::setAttribute(Qt::WA_DeleteOnClose) instead.
+\row \o Qt::WStaticContents \o{1,2} Use QWidget::setAttribute(Qt::WA_StaticContents) instead.
+\row \o Qt::WNorthWestGravity
+\row \o Qt::WNoAutoErase \o{1,3} Use QWidget::setAttribute(Qt::WA_NoBackground) instead.
+\row \o Qt::WResizeNoErase
+\row \o Qt::WRepaintNoErase
+\row \o Qt::WPaintClever \o Unnecessary in Qt 4.
+\omit ### Check with Matthias \endomit
+\row \o Qt::WMacNoSheet \o Unnecessary in Qt 4.
+\omit ### Check with Sam \endomit
+\endtable
+In Qt 4.1, the widget flags used to determine window modality were
+replaced by a single enum that can be used to specify the modal
+behavior of top-level widgets:
+\table
+\header \o Qt 3 type \o Qt 4 equivalent
+\row \o Qt::WShowModal \o Use QWidget::setWindowModality(Qt::ApplicationModal) instead.
+\row \o Qt::WGroupLeader \o Use QWidget::setWindowModality(Qt::WindowModal)
+for each child dialog of the group leader, but do not change the modality
+of the group leader itself.
+\endtable
+\target properties
+\section1 Properties
+Some properties have been renamed in Qt 4, to make Qt's API more
+consistent and more intuitive. For example, QWidget's \c caption
+property has been renamed \c windowTitle to make it clear that it
+refers to the title shown in the window's title bar.
+In addition, the property system has been extended to allow
+properties to be redefined in subclasses with the \l Q_PROPERTY()
+macro, removing the need for a \c Q_OVERRIDE() macro.
+The table below lists the Qt properties that have been renamed in
+Qt 4. Occurrences of these in \e{Qt Designer} UI files are
+automatically converted to the new name by \c uic.
+\table
+\header \o Qt 3 name \o Qt 4 name
+\row \o QButton::accel \o QButton::shortcut
+\row \o QButton::on \o QButton::checked
+\row \o QButton::toggleButton \o QAbstractButton::checkable
+\row \o QDial::lineStep \o QDial::singleStep
+\row \o QDial::maxValue \o QDial::maximum
+\row \o QDial::minValue \o QDial::minimum
+\row \o QDialog::modal \o QDialog::isModal
+\row \o QLineEdit::edited \o QLineEdit::modified
+\row \o QLineEdit::hasMarkedText \o QLineEdit::hasSelectedText
+\row \o QLineEdit::markedText \o QLineEdit::selectedText
+\row \o QObject::name \o QObject::objectName
+\row \o QProgressDialog::progress \o QProgressDialog::value
+\row \o QProgressDialog::totalSteps \o QProgressDialog::maximum
+\row \o QProgressDialog::wasCancelled \o QProgressDialog::wasCanceled
+\row \o QPushButton::iconSet \o QPushButton::icon
+\row \o QScrollBar::draggingSlider \o QScrollBar::sliderDown
+\row \o QScrollBar::lineStep \o QScrollBar::singleStep
+\row \o QScrollBar::maxValue \o QScrollBar::maximum
+\row \o QScrollBar::minValue \o QScrollBar::minimum
+\row \o QSlider::lineStep \o QSlider::singleStep
+\row \o QSlider::maxValue \o QSlider::maximum
+\row \o QSlider::minValue \o QSlider::minimum
+\row \o QSpinBox::lineStep \o QSpinBox::singleStep
+\row \o QSpinBox::maxValue \o QSpinBox::maximum
+\row \o QSpinBox::minValue \o QSpinBox::minimum
+\row \o QTabBar::currentTab \o QTabBar::currentIndex
+\row \o QTabWidget::currentPage \o QTabWidget::currentWidget
+\row \o QToolButton::iconSet \o QToolButton::icon
+\row \o QToolButton::textLabel \o QToolButton::text
+\row \o QWidget::caption \o QWidget::windowTitle
+\row \o QWidget::icon \o QWidget::windowIcon
+\row \o QWidget::iconText \o QWidget::windowIconText
+\endtable
+A handful of properties in Qt 3 are no longer properties in Qt 4,
+but the access functions still exist as part of the Qt 4 API.
+These are not used by \e{Qt Designer}; the only case where you
+need to worry about them is in highly dynamic applications that
+use Qt's meta-object system to access properties. Here's the list
+of these properties with the read and write functions that you
+can use instead:
+\table
+\header \o Qt 3 property \o Qt 4 read function \o Qt 4 write function
+\row \o QSqlDatabase::connectOptions \o QSqlDatabase::connectOptions() \o QSqlDatabase::setConnectOptions()
+\row \o QSqlDatabase::databaseName \o QSqlDatabase::databaseName() \o QSqlDatabase::setDatabaseName()
+\row \o QSqlDatabase::hostName \o QSqlDatabase::hostName() \o QSqlDatabase::setHostName()
+\row \o QSqlDatabase::password \o QSqlDatabase::password() \o QSqlDatabase::setPassword()
+\row \o QSqlDatabase::port \o QSqlDatabase::port() \o QSqlDatabase::setPort()
+\row \o QSqlDatabase::userName \o QSqlDatabase::userName() \o QSqlDatabase::setUserName()
+\endtable
+Some properties have been removed from Qt 4, but the associated
+access functions are provided if \c QT3_SUPPORT is defined to help
+porting to Qt 4. When converting Qt 3 UI files to Qt 4, \c uic
+generates calls to the Qt 3 compatibility functions. Note that
+this only applies to the properties of the Qt3Support library,
+i.e. \c QT3_SUPPORT properties of the other libraries must be
+ported manually when converting Qt 3 UI files to Qt 4.
+The table below lists these properties with the read and write
+functions that you can use instead. The documentation for the
+individual functions explains how to replace them with
+non-compatibility Qt 4 functions.
+\table
+\header \o Qt 3 property \o Qt 4 read function (\c QT3_SUPPORT)\o Qt 4 write function (\c QT3_SUPPORT)
+\row \o QMenuBar::separator \o QMenuBar::separator() \o QMenuBar::setSeparator()
+\row \o QPushButton::menuButton \o QPushButton::isMenuButton() \o N/A
+\row \o QTabWidget::margin \o QTabWidget::margin() \o QTabWidget::setMargin()
+\row \o QTextEdit::textFormat \o QTextEdit::textFormat() \o QTextEdit::setTextFormat()
+\row \o QWidget::backgroundBrush \o QWidget::backgroundBrush() \o N/A
+\row \o QWidget::backgroundMode \o QWidget::backgroundMode() \o QWidget::setBackgroundMode()
+\row \o QWidget::backgroundOrigin \o QWidget::backgroundOrigin() \o QWidget::setBackgroundOrigin()
+\row \o QWidget::colorGroup \o QWidget::colorGroup() \o QWidget::setColorGroup()
+\row \o QWidget::customWhatsThis \o QWidget::customWhatsThis() \o QWidget::setCustomWhatsThis()
+\row \o QWidget::inputMethodEnabled \o QWidget::inputMethodEnabled() \o QWidget::setInputMethodEnabled()
+\row \o QWidget::ownCursor \o QWidget::ownCursor() \o N/A
+\row \o QWidget::ownFont \o QWidget::ownFont() \o N/A
+\row \o QWidget::ownPalette \o QWidget::ownPalette() \o N/A
+\row \o QWidget::paletteBackgroundColor \o QWidget::paletteBackgroundColor() \o QWidget::setPaletteBackgroundColor()
+\row \o QWidget::paletteBackgroundPixmap \o QWidget::paletteBackgroundPixmap() \o QWidget::setPaletteBackgroundPixmap()
+\row \o QWidget::paletteForegroundColor \o QWidget::paletteForegroundColor() \o QWidget::setPaletteForegroundColor()
+\row \o QWidget::underMouse \o QWidget::underMouse() \o N/A
+\endtable
+The following Qt 3 properties and their access functions are no
+longer available in Qt 4. In most cases, Qt 4 provides similar
+functionality.
+\table
+\header \o Qt 3 property \o Qt 4 equivalent
+\row \o QButton::autoRepeat \o N/A
+\row \o QButton::autoResize \o Call QWidget:setFixedSize(QWidget::sizeHint()) whenever you change the contents.
+\row \o QButton::exclusiveToggle \o See \l QAbstractButton::autoExclusive.
+\row \o QButton::pixmap \o Use QAbstractButton::icon instead.
+\row \o QButton::toggleState \o Use QCheckBox::setState() and QCheckBox::state() instead.
+\row \o QButton::toggleType \o Use QCheckBox::setTristate() instead.
+\row \o QComboBox::autoResize \o Call QWidget:setFixedSize(QWidget::sizeHint()) whenever you change the contents.
+\row \o QFrame::contentsRect \o Use Q3Frame::contentsRect() instead.
+\row \o QFrame::margin \o Use QWidget::setContentsMargins() instead.
+\row \o QTabBar::keyboardFocusTab \o N/A
+\row \o QToolButton::offIconSet \o Use the \l{QIcon::Off}{off component} of QAbstractButton::icon instead.
+\row \o QToolButton::onIconSet \o Use the \l{QIcon::On}{on component} of QAbstractButton::icon instead.
+\row \o QWidget::microFocusHint \o N/A
+\row \o QMimeSource::serialNumber () \o N/A
+\endtable
+\omit
+\section1 Inheritance Chain
+### QMenuBar, etc.
+\section1 Null vs. Empty
+###
+\endomit
+\section1 Explicit Sharing
+Qt 4 is the first version of Qt that contains no \link
+http://qt.nokia.com/doc/3.3/shclass.html explicitly shared
+\endlink classes. All classes that were explicitly shared in Qt 3
+are \e implicitly shared in Qt 4:
+\list
+\o QImage
+\o QBitArray
+\o QByteArray
+\o Q3PointArray
+\endlist
+This means that if you took a copy of an instance of the class
+(using operator=() or the class's copy constructor), any
+modification to the copy would affect the original and vice
+versa. Needless to say, this behavior is rarely desirable.
+Fortunately, nearly all Qt 3 applications don't rely on explicit
+sharing. When porting, you typically only need to remove calls to
+detach() and/or copy(), which aren't necessary anymore.
+If you deliberately rely on explicit sharing in your application,
+you can use pointers or references to achieve the same result in
+Qt 4.
+\oldcode
+void asciify(QByteArray array)
+{
+for (int i = 0; i < (int)array.size(); ++i) {
+if ((uchar)array[i] >= 128)
+array[i] = '?';
+}
+}
+\newcode
+void asciify(QByteArray &array)
+{
+for (int i = 0; i < array.size(); ++i) {
+if ((uchar)array[i] >= 128)
+array[i] = '?';
+}
+}
+\endcode
+(Notice the \c & in the parameter declaration.)
+\omit
+\section1 Qt Designer UI Files
+###
+\endomit
+\section1 Painting and Redrawing Widgets
+When implementing custom widgets in Qt 3, it was possible to use
+QPainter to draw on a widget outside paint events. This made it
+possible to integrate Qt applications with third party libraries
+and tools that impose their own rendering models. For example,
+a widget might be repainted in a slot using data obtained from
+an external source.
+In Qt 4, it is only possible to paint on a widget from within its
+\l{QWidget::}{paintEvent()} handler function. This restriction simplifies
+Qt's interaction with native window systems, improves the performance
+of applications by reducing the number of redraw operations, and
+also enables features to be implemented to improve the appearance of
+widgets, such as a backing store.
+Generally, we recommend redesigning applications to perform all
+painting operations in \l{QWidget::}{paintEvent()} functions, deferring
+actual painting until the next time this function is called.
+Applications can post paint events to trigger repaints, and it may be
+possible to examine your widget's internal state to determine which
+part of the widget needs to be repainted.
+If asynchronous repaints are used extensively by your application,
+and it is not practical to redesign the rendering model to perform
+all painting operations from within a widget's \l{QWidget::}{paintEvent()}
+function, it may be necessary to consider using an intermediate painting
+step. In this approach, one or more images can be updated asynchronously
+and painted on the widget in the paint event. To avoid excessive
+buffering, it may be worthwhile disabling the backing store by setting
+the widget's Qt::WA_PaintOnScreen widget attribute.
+On certain platforms, the Qt::WA_PaintOutsidePaintEvent widget attribute
+can be set to allow a widget to be painted from outside paint events.
+\note Setting widget attributes to disable key features of Qt's widget
+rendering model may also cause other features to be disabled.
+\section1 Compatibility Signals and Slots
+When \c QT3_SUPPORT is defined, the default connection type for signals
+and slots is the Qt::AutoCompatConnection type. This allows so-called
+\e compatibility signals and slots (defined in Qt 3 support mode to provide
+Qt 3 compatibility features) to be connected to other signals and
+slots.
+However, if Qt is compiled with debugging output enabled, and the
+developer uses other connection types to connect to compatibility
+signals and slots (perhaps by building their application without Qt 3
+support enabled), then Qt will output warnings to the console to
+indicate that compatibility connections are being made. This is intended
+to be used as an aid in the process of porting a Qt 3 application to Qt 4.
+\section1 QAccel
+The \c QAccel class has been renamed Q3Accel and moved to the
+Qt3Support module. In new applications, you have three options:
+\list 1
+\o You can use QAction and set a key sequence using QAction::setShortcut().
+\o You can use QShortcut, a class that provides similar
+functionality to Q3Accel.
+\o You can use QWidget::grabShortcut() and process "shortcut"
+events by reimplementing QWidget::event().
+\endlist
+The Q3Accel class also supports multiple accelerators using the
+same object, by calling Q3Accel::insertItem() multiple times. In
+Qt 4, the solution is to create multiple QShortcut objects.
+\section1 QAccessibleInterface
+The QAccessibleInterface class has undergone some API changes in
+Qt 4, to make it more consistent with the rest of the Qt API.
+If you have classes that inherit QAccessibleInterface or one of
+its subclasses (QAccessibleObject, QAccessibleWidget, etc.), you
+must port them the new QAccessibleInterface API.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions}
+for a list of QAccessibleInterface virtual member functions in
+Qt 3 that are no longer virtual in Qt 4.
+\section1 QAccessibleTitleBar
+The \c QAccessibleTitleBar has been renamed Q3AccessibleTitleBar
+and moved to the Qt3Support library.
+\target qaction.section
+\section1 QAction
+The QAction class has been redesigned in Qt 4 to integrate better
+with the rest of the menu system. It unifies the old \c QMenuItem
+class and the old \c QAction class into one class, avoiding
+unnecessary data duplication and the need to learn two different
+APIs.
+The old \c QAction and \c QActionGroup classes have been renamed
+Q3Action and Q3ActionGroup and moved to Qt3Support. In addition,
+the new QAction class has compatibility functions to ease
+transition to Qt 4. Note that when using Q3ToolBar and
+Q3PopupMenu, their actions must be \l {Q3Action}s.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions}
+for a list of QAction virtual member functions in Qt 3 that are
+no longer virtual in Qt 4.
+\section1 QActionGroup
+The QAction class has been completely redesigned in Qt 4 to
+integrate better with the rest of the menu system. See the
+\l{#qaction.section}{section on QAction} for details.
+\section1 QApplication
+The QApplication class has been split into two classes:
+QCoreApplication and QApplication. The new QApplication class
+inherits QCoreApplication and adds GUI-related functionality. In
+practice, this has no consequences for existing Qt applications.
+In addition, the following API changes were made:
+\list 1
+\o  QApplication::allWidgets() and QApplication::topLevelWidgets()
+used to return a pointer to a QWidgetList. Now they return a
+QWidgetList.
+Also, QWidgetList has changed from being a typedef for
+QPtrList<QWidget> to being a typedef for QList<QWidget *>.
+See the \l{#qwidgetlist.section}{section on QWidgetList} below
+for details.
+\oldcode
+QWidgetList *list = QApplication::topLevelWidgets();
+QWidgetListIt it(*list);
+QWidget *widget;
+while ((widget = it.current())) {
+if (widget->inherits("MainWindow"))
+((MainWindow *)widget)->updateRecentFileItems();
+++it;
+}
+delete list;
+\newcode
+QWidgetList list = QApplication::topLevelWidgets();
+for (int i = 0; i < list.size(); ++i) {
+if (MainWindow *mainWin = qobject_cast<MainWindow *>(list.at(i)))
+mainWin->updateRecentFileItems();
+}
+\endcode
+\o QApplication::setMainWidget() is no longer used. When all an application's
+windows are closed, the application will exit normally.
+\endlist
+\section1 QAquaStyle
+The \c QAquaStyle class first appeared in Qt 3.0, when the Qt for
+Mac OS X port was first released. It emulated Apple's "Aqua" theme.
+In Qt 3.1, QAquaStyle was obsoleted by QMacStyle, which uses Appearance
+Manager to perform its drawing.
+The \c QAquaStyle class is no longer provided in Qt 4. Use
+QMacStyle instead.
+\target qasciidict.section
+\section1 QAsciiCache<T>
+\c QAsciiCache<T> has been renamed Q3AsciiCache<T> and moved to
+the Qt3Support library. It has been replaced by
+QCache<QByteArray, T>.
+For details, read the \l{#qcache.section}{section on QCache<T>},
+mentally substituting QByteArray for QString.
+\section1 QAsciiDict<T>
+QAsciiDict<T> and QAsciiDictIterator<T> have been renamed
+Q3AsciiDict<T> and Q3AsciiDictIterator<T> and moved to the
+Qt3Support library. They have been replaced by the
+more modern QHash<Key, T> and QMultiHash<Key, T> classes and
+their associated iterator classes.
+When porting old code that uses Q3AsciiDict<T> to Qt 4, there are
+four classes that you can use:
+\list
+\o QMultiHash<QByteArray, T *>
+\o QMultiHash<QByteArray, T>
+\o QHash<QByteArray, T *>
+\o QHash<QByteArray, T>
+\endlist
+For details, read the \l{#qdict.section}{section on QDict<T>},
+mentally substituting QByteArray for QString.
+\section1 QAsyncIO
+The \c QAsyncIO class was used internally in Qt 2.x in
+conjunction with QImageConsumer. It was obsoleted in Qt 3.0.
+\input porting/porting4-obsoletedmechanism.qdocinc
+\section1 QBackInsertIterator
+The undocumented \c QBackInsertIterator class has been removed
+from the Qt library. If you need it in your application, feel
+free to copy the source code from the Qt 3 \c <qtl.h> header
+file.
+\section1 QBitArray
+In Qt 3, QBitArray inherited from QByteArray. In Qt 4, QBitArray
+is a totally independent class. This makes very little difference
+to the user, except that the new QBitArray doesn't provide any of
+QByteArray's byte-based API anymore. These calls will result in a
+compile-time error, except calls to QBitArray::truncate(), whose
+parameter was a number of \e bytes in Qt 3 and a number of bits
+in Qt 4.
+QBitArray was an explicitly shared class in Qt 3. See \l{Explicit
+Sharing} for more information.
+The \c QBitVal class has been renamed QBitRef.
+\section1 QButton
+The \c QButton class has been replaced by QAbstractButton in Qt
+4. Classes like QPushButton and QRadioButton inherit from
+QAbstractButton. As a help when porting older Qt applications,
+the Qt3Support library contains a Q3Button class
+implemented in terms of the new QAbstractButton.
+If you used the \c QButton class as a base class for your own
+button type and want to port your code to the newer
+QAbstractButton, you need to be aware that QAbstractButton has no
+equivalent for the Q3Button::drawButton(QPainter *) virtual
+function. The solution is to reimplement QWidget::paintEvent() in
+your QAbstractButton subclass as follows:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 0
+\table
+\header \o Q3Button function \o QAbstractButton equivalent
+\row \o Q3Button::autoResize() \o Call QWidget:setFixedSize(QWidget::sizeHint()) whenever you change the contents.
+\row \o Q3Button::isExclusiveToggle() \o Use QAbstractButton::group() or QAbstractButton::autoExclusive() instead.
+\row \o Q3Button::pixmap() const \o QAbstractButton::icon()
+\row \o Q3Button::setAutoResize() \o N/A
+\row \o Q3Button::setPixmap(const QPixmap &) \o QAbstractButton::setIcon(const QIcon &)
+\row \o Q3Button::setState(ToggleState) \o See remark below
+\row \o Q3Button::setToggleType(ToggleType) \o See remark below
+\row \o Q3Button::state() \o See remark below
+\row \o Q3Button::stateChanged(int) \o See remark below
+\row \o Q3Button::toggleType() \o See remark below
+\endtable
+Remarks:
+\list 1
+\o In Qt 3, \c QButton had a "toggle type", which could be
+QButton::SingleShot, QButton::Toggle, or QButton::Tristate.
+The new QAbstractButton class doesn't support "tristate"
+directly; this feature is implemented in QCheckBox instead.
+The two other "toggle types" (\c QButton::SingleShot and \c
+QButton::Toggle) are replaced by a QAbstractButton::checkable
+property.
+\o In Qt 3, QButton had a "toggle state", which could be \c
+QButton::Off, \c QButton::NoChange, or \c QButton::On. In Qt
+4, this mechanism has been moved to QCheckBox.
+\endlist
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of \c QButton virtual member functions in Qt 3 that aren't
+virtual in Qt 4.
+See \l{#properties}{Properties} for a list of \c QButton properties
+in Qt 3 that have changed in Qt 4.
+\section1 QButtonGroup
+The \c QButtonGroup class has been completely redesigned in Qt 4.
+For compatibility, the old \c QButtonGroup class has been renamed
+Q3ButtonGroup and has been moved to Qt3Support.
+Likewise, the \c QHButtonGroup and \c QVButtonGroup convenience
+subclasses have been renamed \c Q3HButtonGroup and \c Q3VButtonGroup and
+moved to the Qt3Support library.
+The old \c QButtonGroup, as well as Q3ButtonGroup, can be used in two ways:
+\list 1
+\o  The button group is the parent widget of a number of buttons,
+i.e. the button group is the parent argument in the button
+constructor. The buttons are assigned identifiers 0, 1, 2, etc.,
+in the order they are created. A Q3ButtonGroup can display a frame
+and a title because it inherits Q3GroupBox.
+\o  The button group is an invisible widget and the contained
+buttons have some other parent widget. In this usage, each
+button must be manually inserted, using
+Q3ButtonGroup::insert(), into the button group and given an
+ID number.
+\endlist
+Unlike Q3ButtonGroup, the new QButtonGroup doesn't inherit
+QWidget. It is very similar to a "hidden Q3ButtonGroup".
+If you use a Q3ButtonGroup, Q3HButtonGroup, or Q3VButtonGroup as
+a widget and want to port to Qt 4, you can replace it with
+QGroupBox. In Qt 4, radio buttons with the same parent are
+automatically part of an exclusive group, so you normally don't
+need to do anything else. See also the
+\l{#qgroupbox.section}{section on QGroupBox} below.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QButtonGroup virtual member functions in Qt 3 that are no
+longer virtual in Qt 4.
+\target qbytearray.section
+\section1 QByteArray
+In Qt 3, QByteArray was simply a typedef for QMemArray<char>. In
+Qt 4, QByteArray is a class in its own right, with a higher-level
+API in the style of QString.
+Here are the main issues to be aware of when porting to Qt 4:
+\list 1
+\o  The QMemArray(int size) constructor has been replaced with
+QByteArray(int size, char ch). The second argument specifies
+which character should be used for initializing the array;
+pass '\\0' if you have no specific needs.
+\oldcode
+QByteArray ba(64);
+\newcode
+QByteArray ba(64, '\0');
+\endcode
+\o  QMemArray::at() returned a non-const reference, whereas the
+new QByteArray::at() returns a const value. Code like
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 1
+will no longer compile. Instead, use QByteArray::operator[]:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 2
+\o  The QMemArray::contains(char) function has been renamed
+QByteArray::count(char). In addition, there now exists a
+QByteArray::contains(char) function that returns a boolean
+value. Replace old calls to contains() with either count() or
+contains(), depending on whether you care about the specific
+number of occurrences of a character in the byte array or
+only care about whether the array contains that character or
+not.
+\o  The new QByteArray has no assign() function. Calls to
+QMemArray::assign(const QMemArray &) can be replaced by calls
+to QByteArray::operator=(). Calls to QMemArray::assign(const
+T *, uint) have no equivalent in Qt 4; if you use it, the
+solution is either to use QByteArray::fromRawData() and to
+call free() yourself to avoid a memory leak, or to use the
+QByteArray(const char *, int) constructor, which will take a
+deep copy of the data.
+\o  QMemArray::bsearch() and QMemArray::sort() have no equivalent
+in the new QByteArray class. Use \l qBinaryFind() and \l qSort()
+if you need that functionality.
+\endlist
+QByteArray was an explicitly shared class in Qt 3. See
+\l{Explicit Sharing} for more information.
+\target qcache.section
+\section1 QCache<T>
+QCache<T> has been renamed Q3Cache<T> and moved to Qt3Support.
+The new QCache class has a different API, and takes different
+template parameters: QCache<Key, T>.
+When porting to Qt 4, QCache<QString, T> is the obvious
+substitute for Q3Cache<T>. The following table summarizes the API
+differences.
+\table
+\header \o Q3Cache<T> function \o QCache<QString, T> equivalent
+\row \o Q3Cache::Q3Cache(int maxCost, int size, bool caseSensitive) \o See remark below
+\row \o Q3Cache::autoDelete() \o N/A
+\row \o Q3Cache::count() \o QCache::count() or QCache::size() (equivalent)
+\row \o Q3Cache::setAutoDelete() \o See remark below
+\row \o Q3Cache::size() \o N/A
+\row \o Q3Cache::statistics() \o N/A
+\row \o Q3Cache::operator=() \o See remark below
+\endtable
+Remarks:
+\list 1
+\o  Q3Cache requires the user to allocate a specific number of
+buckets by passing a prime number (17 by default) to the
+constructor. In contrast, the new QCache's hash table
+automatically grows and shrinks as needed, and the
+constructor doesn't take a prime number.
+\o  Q3Cache supportes case-insensitive lookups by passing false as
+second argument to the constructor. This feature has no
+equivalent in QMultiHash. Instead, call QString::toLower()
+before you insert or lookup a key in the hash.
+\o  The Q3Cache::insert() function returns a \c bool value that
+indicates whether or not the item actually was inserted in
+the cache. If the item wasn't inserted, it was the caller's
+responsibility to delete the item. The new QCache::insert()
+function returns \c void and either adds it to the cache or
+deletes it right away. Old code like
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 3
+becomes
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 4
+\o  The new QCache class \e always takes ownership of the items
+it stores (i.e. auto-delete is always on). If you use Q3Cache
+with auto-delete turned off (the rarely useful default), you
+cannot use QCache as a direct substitute. One unelegant trick
+that works well in practice is to use QCache<QString, T *>
+instead of QCache<QString, T>. In that case, QCache owns the
+pointers, not the objects that the pointers refer to. For
+example,
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 5
+becomes
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 6
+An alternative is to stick to using Q3Cache.
+\endlist
+QCacheIterator<T> has been renamed Q3CacheIterator<T> and moved
+to the Qt3Support library. The new QCache class
+doesn't offer any iterator types.
+\section1 QCanvas
+The canvas module classes have been
+renamed and moved to the Qt3Support library.
+\table
+\header \o Qt 3 class name \o Compatibility class in Qt 4
+\row \o \c QCanvas \o Q3Canvas
+\row \o \c QCanvasEllipse \o Q3CanvasEllipse
+\row \o \c QCanvasItem \o Q3CanvasItem
+\row \o \c QCanvasItemList \o Q3CanvasItemList
+\row \o \c QCanvasLine \o Q3CanvasLine
+\row \o \c QCanvasPixmap \o Q3CanvasPixmap
+\row \o \c QCanvasPixmapArray \o Q3CanvasPixmapArray
+\row \o \c QCanvasPolygon \o Q3CanvasPolygon
+\row \o \c QCanvasPolygonalItem \o Q3CanvasPolygonalItem
+\row \o \c QCanvasRectangle \o Q3CanvasRectangle
+\row \o \c QCanvasSpline \o Q3CanvasSpline
+\row \o \c QCanvasSprite \o Q3CanvasSprite
+\row \o \c QCanvasText \o Q3CanvasText
+\row \o \c QCanvasView \o Q3CanvasView
+\endtable
+\l{The Graphics View Framework} replaces QCanvas. For more on porting to
+Graphics View, see \l{Porting to Graphics View}.
+\section1 QColor
+In Qt 4, QColor is a value type like QPoint or QRect. Graphics
+system-specific code has been implemented in QColormap.
+The \c QColor::maxColors() function has been replaced
+by QColormap::size().
+The \c QColor::numBitPlanes() function has been replaced
+by QColormap::depth().
+The \c QColor::setNamedColor() function no longer supports
+the named color in the same way as Qt 3. Qt 4's
+\l{QColor::}{setNamedColor()} uses the new W3C convention
+as stated
+\l{http://www.w3.org/TR/SVG/types.html#ColorKeywords}{here}.
+\table
+\header \o{4,1} Predefined Qt Colors
+\row \o Qt::color0 \o Qt::color1 \o Qt::black \o Qt::white
+\row \o Qt::darkGray \o Qt::gray \o Qt::lightGray \o Qt::red
+\row \o Qt::green \o Qt::blue \o Qt::cyan \o Qt::magenta
+\row \o Qt::yellow \o Qt::darkRed \o Qt::darkGreen \o Qt::darkBlue
+\row \o Qt::darkCyan \o Qt::darkMagenta \o Qt::darkYellow \o Qt::transparent
+\endtable
+The predefined colors listed in the table above were static
+QColor objects in Qt 3. In Qt 4, they are enum values of type
+Qt::GlobalColor. Thanks to the implicit QColor(Qt::GlobalColor)
+constructor, the enum values are automatically converted to
+\l{QColor}s in most contexts. Occasionally, you might need a
+cast.
+\oldcode
+QColor lightCyan = Qt::cyan.light(180);
+\newcode
+QColor lightCyan = QColor(Qt::cyan).light(180);
+\endcode
+\section1 QColorGroup
+In Qt 3, a QPalette consisted of three QColorGroup objects. In Qt
+4, the (rarely used) QColorGroup abstraction has been eliminated.
+For source compatibility, a QColorGroup class is available when
+\c QT3_SUPPORT is defined.
+The new QPalette still works in terms of color groups, specified
+through enum values (QPalette::Active, QPalette::Disabled, and
+QPalette::Inactive). It also has the concept of a \e current
+color group, which you can set using
+QPalette::setCurrentColorGroup().
+The QPalette object returned by QWidget::palette() returns a
+QPalette initialized with the correct current color group for the
+widget. This means that if you had code like
+\badcode
+painter.setBrush(colorGroup().brush(QColorGroup::Text));
+\endcode
+you can simply replace colorGroup() with palette():
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 7
+\section1 QColorDrag
+The \c QColorDrag class has been renamed Q3ColorDrag and moved to
+the Qt3Support library. In Qt 4, use QMimeData
+instead and call QMimeData::setColor() to set the color.
+\section1 QComboBox
+In Qt 3, the list box used to display the contents of a \c QComboBox
+widget could be accessed by using the \c listBox() function. In Qt 4,
+the standard list box is provided by a QListView widget, and can be
+accessed with the \l{QComboBox::view()}{view()} function.
+\omit ### \endomit
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QComboBox virtual member functions in Qt 3 that are no longer
+virtual in Qt 4.
+\section1 QCString
+In Qt 3, QCString inherited from QByteArray. The main drawback
+of this approach is that the user had the responsibility of
+ensuring that the string is '\\0'-terminated. Another important
+issue was that conversions between \c QCString and QByteArray often
+gave confusing results. (See the
+\l{http://qt.nokia.com/doc/qq/qq05-achtung.html#qcstringisastringofchars}{Achtung!
+Binary and Character Data} article in \e{Qt Quarterly} for an
+overview of the pitfalls.)
+Qt 4 solves that problem by merging the QByteArray and \c QCString
+classes into one class called QByteArray. Most functions that
+were in \c QCString previously have been moved to QByteArray. The
+'\\0' issue is handled by having QByteArray allocate one extra
+byte that it always sets to '\\0'. For example:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 8
+The Qt3Support library contains a class called
+Q3CString that inherits from the new QByteArray class and that
+extends it to provide an API that is as close to the old \c QCString
+class as possible. Note that the following functions aren't
+provided by Q3CString:
+\list
+\o QCString::find(const QRegExp &, int)
+\o QCString::findRev(const QRegExp &, int)
+\o QCString::contains(const QRegExp &)
+\o QCString::replace(const QRegExp &, const char *)
+\endlist
+The following functions have lost their last parameter, which
+specified whether the search was case sensitive or not:
+\list
+\o QByteArray::find(char, int)
+\o QByteArray::find(const char *, int)
+\o QByteArray::findRev(char, int)
+\o QByteArray::findRev(const char *, int)
+\o QByteArray::contains(char)
+\o QByteArray::contains(const char *)
+\endlist
+In both cases, the solution is to convert the \c QCString to a
+QString and use the corresponding QString functions instead.
+Also be aware that \c QCString::size() (inherited from
+QByteArray) used to return the size of the character data \e
+including the '\\0'-terminator, whereas the new
+QByteArray::size() is just a synonym for QByteArray::length().
+This brings QByteArray in line with QString.
+When porting to Qt 4, occurrences of \c QCString should be
+replaced with QByteArray or QString. The following table
+summarizes the API differences between the Q3CString
+class and the Qt 4 QByteArray and QString classes:
+\table
+\header \o Q3CString function \o Qt 4 equivalent
+\row \o Q3CString::Q3CString(const char *, uint) \o See remark below
+\row \o Q3CString::Q3CString(int) \o QByteArray::QByteArray(int, char)
+\row \o Q3CString::leftJustify() \o QString::leftJustified()
+\row \o Q3CString::length() \o QByteArray::length() or QByteArray::size() (equivalent)
+\row \o Q3CString::lower() \o QByteArray::toLower()
+\row \o Q3CString::rightJustify() \o QString::rightJustified()
+\row \o Q3CString::setExpand() \o See remark below
+\row \o Q3CString::simplifyWhiteSpace() \o QByteArray::simplified()
+\row \o Q3CString::sprintf() \o QString::sprintf()
+\row \o Q3CString::stripWhiteSpace() \o QByteArray::trimmed()
+\row \o Q3CString::toDouble() \o QString::toDouble()
+\row \o Q3CString::toFloat() \o QString::toFloat()
+\row \o Q3CString::toInt() \o QString::toInt()
+\row \o Q3CString::toLong() \o QString::toLong()
+\row \o Q3CString::toShort() \o QString::toShort()
+\row \o Q3CString::toUInt() \o QString::toUInt()
+\row \o Q3CString::toULong() \o QString::toULong()
+\row \o Q3CString::toUShort() \o QString::toUShort()
+\row \o Q3CString::upper() \o QByteArray::toUpper()
+\endtable
+Remarks:
+\list 1
+\o  Q3CString(const char *str, uint max) constructs a string of
+length strlen(str) or \e max - 1, whichever is shorter.
+QByteArray(const char *data, int size) constructs a byte
+array containing exactly \e size bytes.
+\oldcode
+QCString str1("Hello", 4);           // "Hel"
+QCString str2("Hello world!", n);
+\newcode
+QByteArray str1("Hello", 3);
+QByteArray str2("Hello world!");
+str2.truncate(n - 1);
+\endcode
+\o  Q3CString::setExpand(uint index, char ch) has no equivalent in
+Qt 4.
+\oldcode
+QCString str("Hello world");
+str.setExpand(16, '\n');            // "Hello world     \n"
+\newcode
+QByteArray str("Hello world");
+while (str.size() < 16)
+str += ' ';
+str += '\n';
+\endcode
+\endlist
+Since the old \c QCString class inherited from QByteArray,
+everything that is said in the \l{#qbytearray.section}{QByteArray
+section} applies for \c QCString as well.
+\section1 QCustomEvent
+In Qt 3, developers could create a custom event by constructing
+a new QCustomEvent, and send relevant data to other components in
+the application by passing a void pointer, either on construction or
+using the setData() function. Objects could receive custom events
+by reimplementing the \l{QObject::customEvent()}{customEvent()}
+function, and access the stored data using the event's data()
+function.
+In Qt 4, custom events are created by subclassing
+QEvent. Event-specific data can be stored in a way that is
+appropriate for your application. Custom events are still
+delivered to each object's
+\l{QObject::customEvent()}{customEvent()} handler function, but as
+QEvent objects rather than as deprecated QCustomEvent objects.
+\section1 QDataBrowser
+The \c QDataBrowser class has been renamed Q3DataBrowser and
+moved to the Qt3Support library. In Qt 4.2, you should use the
+QDataWidgetMapper class to create data-aware forms.
+See \l{QtSql Module} for an overview of the new SQL
+classes.
+\section1 QDataPump
+The \c QDataPump class was used internally in Qt 2.x in
+conjunction with QImageConsumer. It was obsoleted in Qt 3.0.
+\input porting/porting4-obsoletedmechanism.qdocinc
+\section1 QDataSink
+The \c QDataSink class was used internally in Qt 2.x in conjunction
+with QImageConsumer. It was obsoleted in Qt 3.0.
+\input porting/porting4-obsoletedmechanism.qdocinc
+\section1 QDataSource
+The \c QDataSource class was used internally in Qt 2.x in
+conjunction with QImageConsumer. It was obsoleted in Qt 3.0.
+\input porting/porting4-obsoletedmechanism.qdocinc
+\section1 QDataTable
+The \c QDataTable class has been renamed Q3DataTable and moved to
+the Qt3Support library. In Qt 4.2, you should use the
+QDataWidgetMapper class to create data-aware forms.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QDataView
+The \c QDataView class has been renamed Q3DataView and moved to
+the Qt3Support library. In Qt 4.2, you should use the
+QDataWidgetMapper class to create data-aware forms.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QDateEdit
+The QDateEdit class in Qt 4 is a convenience class based on
+QDateTimeEdit. The old class has been renamed Q3DateEdit and moved
+to the Qt3Support library.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of \c QDateEdit virtual member functions in Qt 3 that are
+no longer virtual in Qt 4.
+\section1 QDateTimeEditBase
+The \c QDateTimeEditBase class has been renamed
+Q3DateTimeEditBase and moved to Qt3Support. Use QDateTimeEdit or
+QAbstractSpinBox instead.
+\section1 QDateTimeEdit
+The old \c QDateTimeEdit class has been renamed
+Q3DateTimeEditBase and moved to Qt3Support. The new QDateTimeEdit
+in Qt 4 has been rewritten from scratch to provide a more
+flexible and powerful API.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QDateTimeEdit virtual member functions in Qt 3 that are no
+longer virtual in Qt 4.
+\section1 QDeepCopy<T>
+The \c QDeepCopy<T> class in Qt 3 provided a means of ensuring that
+implicitly shared and explicitly shared classes referenced unique
+data. This was necessary because the reference counting in Qt's
+container classes was done in a thread-unsafe manner.
+With Qt 4, \c QDeepCopy<T> has been renamed Q3DeepCopy<T> and
+moved to the Qt3Support library. Removing it from
+existing code is straightforward.
+\oldcode
+QString str1 = "I am a string";
+QDeepCopy<QString> str2 = str1;
+QString str3 = QDeepCopy<QString>(str2);
+\newcode
+QString str1 = "I am a string";
+QString str2 = str1;
+QString str3 = str2;
+\endcode
+\section1 QDial
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QDial virtual member functions in Qt 3 that are no longer
+virtual in Qt 4.
+See \l{#properties}{Properties} for a list of QDial properties in
+Qt 3 that have changed in Qt 4.
+\target qdict.section
+\section1 QDict<T>
+\c QDict<T> has been renamed Q3Dict<T> and moved to Qt3Support.
+It has been replaced by the more modern QHash<Key, T> and
+QMultiHash<Key, T> classes.
+When porting old code that uses QDict<T> to Qt 4, there are four
+classes that you can use:
+\table
+\header \o Qt 4 class \o When to use it
+\row \o QMultiHash<QString, T *>
+\o Since Q3Dict<T> is pointer-based and allows duplicate
+keys, this is usually the most straightforward conversion.
+\row \o QMultiHash<QString, T>
+\o If type \c T is an \l{assignable data type}, you can use
+\c T as the value type rather than \c{T *}. This often
+leads to nicer code.
+\row \o QHash<QString, T *>
+\o{1,2} If you don't use duplicate keys, you can use QHash
+instead of QMultiHash. QMultiHash inherits from QHash.
+\row \o QHash<QString, T>
+\endtable
+The APIs of Q3Dict<T> and QMultiHash<QString, T *> are quite
+similar. The main issue is that Q3Dict supports auto-delete
+whereas QMultiHash doesn't.
+\omit
+(See \l{What's Wrong with
+Auto-Delete} for an explanation of why the Qt 4 containers don't
+offer that feature.)
+\endomit
+The following table summarizes the API differences between the
+two classes:
+\table
+\header \o Q3Dict function \o QMultiHash equivalent
+\row \o Q3Dict::Q3Dict(int size, bool caseSensitive) \o See remarks below
+\row \o Q3Dict::autoDelete() \o N/A
+\row \o Q3Dict::count() \o QMultiHash::count() or QMultiHash::size() (equivalent)
+\row \o Q3Dict::find(const QString &) \o QMultiHash::value(const QString &)
+\row \o Q3Dict::remove(const QString &) \o QMultiHash::take(const QString &)
+\row \o Q3Dict::resize(uint) \o QMultiHash::reserve(int)
+\row \o Q3Dict::setAutoDelete() \o See discussion below
+\row \o Q3Dict::size() \o QMultiHash::capacity()
+\row \o Q3Dict::statistics() \o N/A
+\row \o Q3Dict::operator[](const QString &) \o See remark below
+\endtable
+Remarks:
+\list 1
+\o  Q3Dict requires the user to allocate a specific number of
+buckets by passing a prime number (17 by default) to the
+constructor and/or calling Q3Dict::resize() later on. In
+contrast, QMultiHash's hash table automatically grows and
+shrinks as needed, and the constructor doesn't take a prime
+number.
+\o  Q3Dict supportes case-insensitive lookups by passing false as
+second argument to the constructor. This feature has no
+equivalent in QMultiHash. Instead, call QString::toLower()
+before you insert or lookup a key in the hash.
+\o  Q3Dict::size() and QMultiHash::size() have different semantics.
+The former returns the number of buckets in the container, whereas
+the latter returns the number of \e items in the container.
+\o  If there are multiple items with the same key,
+Q3Dict::remove() removes only the most recently inserted item,
+whereas QMultiHash::remove() removes all items that share a
+particular key. To remove only the most recently inserted item,
+call QMultiHash::take().
+\o  Q3Dict has only one [] operator (Q3Dict::operator[]()),
+providing const access to an item's value. QMultiHash also
+has a non-const overload that can be used on the left side of
+the assignment operator. If you use the [] operator on a
+non-const QHash with an unexisting item, QHash will created
+an element and initialize it to be a null pointer. For that
+reason, Q3Dict::operator[] should be converted to
+QMultiHash::value(), not QMultiHash::operator[].
+\endlist
+If you use Q3Dict's auto-delete feature (by calling
+Q3Dict::setAutoDelete(true)), you need to do some more work. You
+have two options: Either you call \c delete yourself whenever you
+remove an item from the container, or you use
+QMultiHash<QString, T> instead of QMultiHash<QString, T *> (i.e.
+store values directly instead of pointers to values). Here, we'll
+see when to call \c delete.
+The following table summarizes the idioms that you need to watch
+out for if you want to call \c delete yourself.
+\table
+\header \o Q3Dict idiom \o QMultiHash idiom
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 9
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 10
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 11
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 12
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 13
+(also called from Q3Dict's destructor)
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 14
+In 99% of cases, the following idiom also works:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 15
+However, it may lead to crashes if \c hash is referenced from
+the value type's destructor, because \c hash contains
+dangling pointers until clear() is called.
+\endtable
+Be aware that Q3Dict's destructor automatically calls clear(). If
+you have a Q3Dict data member in a custom class and use the
+auto-delete feature, you will need to call \c delete on all the
+items in the container from your class destructor to avoid a
+memory leak.
+Finally, \c QDictIterator<T> (renamed Q3DictIterator<T>) must
+also be ported. There are no fewer than four iterator classes
+that can be used as a replacement: QHash::const_iterator,
+QHash::iterator, QHashIterator, and QMutableHashIterator. The
+most straightforward class to use when porting is
+QHashIterator<QString, T *>. The following table summarizes the
+API differences:
+\table
+\header \o Q3DictIterator functions \o Qt 4 equivalent
+\row \o Q3DictIterator::count() \o QHash::count() or QHash::size()
+\row \o Q3DictIterator::current() \o QHashIterator::value()
+\row \o Q3DictIterator::currentKey() \o QHashIterator::key()
+\row \o Q3DictIterator::isEmpty() \o QHash::isEmpty()
+\row \o Q3DictIterator::toFirst() \o QHashIterator::toFront()
+\row \o Q3DictIterator::operator()() \o QHashIterator::value()
+\row \o Q3DictIterator::operator*() \o QHashIterator::value()
+\row \o Q3DictIterator::operator++() \o See remark below
+\endtable
+Be aware that QHashIterator has a different way of iterating than
+Q3DictIterator. A typical loop with Q3DictIterator looks like this:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 16
+Here's the equivalent QHashIterator loop:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 17
+See \l{Java-style iterators} for details.
+\section1 QDir
+The following functions used to have a boolean \c{acceptAbsPath}
+parameter that defaulted to true:
+\list
+\i QDir::filePath()
+\i QDir::absFilePath()
+\i QDir::cd()
+\i QDir::mkdir()
+\i QDir::rmdir()
+\i QDir::remove()
+\i QDir::rename()
+\i QDir::exists()
+\endlist
+In Qt 3, if \c acceptAbsPath is true, a file name starting with
+'/' is be returned without change; if \c acceptAbsPath is false,
+an absolute path is prepended to the file name. For example:
+\table
+\header \i Current directory   \i File name        \i \c acceptAbsPath \i File path
+\row    \i{1,2} /home/tsmith   \i{1,2} index.html  \i true             \i /home/tsmith/index.html
+\row                                               \i false            \i /home/tsmith/index.html
+\row    \i{1,2} /home/tsmith   \i{1,2} /index.html \i true             \i /index.html
+\row                                               \i false            \i /home/tsmith/index.html
+\endtable
+In Qt 4, this parameter is no longer available. If you use it
+in your code, you can check that QDir::isRelativePath() returns
+false instead.
+\oldcode
+QDir dir("/home/tsmith");
+QString path = dir.filePath(fileName, false);
+\newcode
+QDir dir("/home/tsmith");
+QString path;
+if (dir.isRelativePath(fileName))
+path = dir.filePath(fileName);
+else
+path = fileName;
+\endcode
+QDir::encodedEntryList() has been removed.
+fileInfoList(), entryInfoList(), and drives() now return a QList<QFileInfo>
+and not a QPtrList<QFileInfo> *. Code using these methods will not work with
+the Qt3Support library and must be adapted instead.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QDir virtual member functions in Qt 3 that are no longer
+virtual in Qt 4.
+QDir::match() now always matches case insensitively.
+QDir::homeDirPath() has been removed. Use QDir::home() instead, and
+extract the path separately.
+\section1 QDns
+Qt 3 used its own implementation of the DNS protocol and provided
+a low-level \c QDns class. Qt 4's QHostInfo class uses the system's \c
+gethostbyname() function from a thread instead.
+The old \c QDns class has been renamed Q3Dns and moved to the
+Qt3Support library. The new QHostInfo class has a
+radically different API: It consists mainly of two static
+functions, one of which is blocking (QHostInfo::fromName()), the
+other non-blocking (QHostInfo::lookupHost()). See the QHostInfo
+class documentation for details.
+\section1 QDockArea
+The \c QDockArea class has been renamed Q3DockArea and moved to
+the Qt3Support library. In Qt 4, QMainWindow handles
+the dock and toolbar areas itself. See the QMainWindow
+documentation for details.
+\section1 QDockWindow
+The old \c QDockWindow class has been renamed Q3DockWindow and
+moved to the Qt3Support library. In Qt 4, there is a
+new QDockWidget class with a different API. See the class
+documentation for details.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QDockWidget virtual member functions in Qt 3 that are no
+longer virtual in Qt 4.
+\note \l{Q3DockWindow}'s
+\l{Q3DockWindow::setHorizontallyStretchable()}{horizontallyStretchable}
+property can be achieved in QDockWidget with
+\l{QWidget#Size Hints and Size Policies}{size policies}.
+\section1 QDragObject
+The \c QDragObject class has been renamed Q3DragObject and
+moved to the Qt3Support library. In Qt 4, it has been
+replaced by the QMimeData class. See the class documentation for
+details.
+Note that the Q3DragObject::DragCopyOrMove drag and drop mode is
+interpreted differently to Qt 3's QDragObject::DragCopyOrMove mode.
+In Qt 3, a move operation was performed by default, and the user had
+to hold down the \key{Ctrl} key to perform a copy operation.
+In Qt 4, a copy operation is performed by default; the user has to
+hold down the \key{Shift} key to perform a move operation.
+See \l{Porting to Qt 4 - Drag and Drop} for a comparison between
+the drag and drop APIs in Qt 3 and Qt 4.
+\section1 QDropSite
+The \c QDropSite class has been renamed Q3DropSite and moved to
+the Qt3Support library.
+The QDropSite class has been obsolete ever since Qt 2.0. The only
+thing it does is call QWidget::setAcceptDrops(true).
+\oldcode
+class MyWidget : public QWidget, public QDropSite
+{
+public:
+MyWidget(const QWidget *parent)
+: QWidget(parent), QDropSite(this)
+{
+}
+...
+}
+\newcode
+class MyWidget : public QWidget
+{
+public:
+MyWidget(const QWidget *parent)
+: QWidget(parent)
+{
+setAcceptDrops(true);
+}
+...
+}
+\endcode
+See \l{Porting to Qt 4 - Drag and Drop} for a comparison between
+the drag and drop APIs in Qt 3 and Qt 4.
+\section1 QEditorFactory
+The \c QEditorFactory class has been renamed Q3EditorFactory and
+moved to the Qt3Support library.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QEventLoop
+In Qt 3, \c QEventLoop combined the Qt event loop and the event
+dispatching. In Qt 4, these tasks are now assigned to two
+distinct classes: QEventLoop and QAbstractEventDispatcher.
+If you subclassed QEventLoop to integrate with another library's
+event loop, you must subclass QAbstractEventDispatcher instead. See
+the class documentation for details.
+Developers using \c{QEventLoop::loopLevel()} in Qt 3 should use
+QCoreApplication::loopLevel() instead. Note that this function is
+marked as obsolete, but it is expected to be available for the
+lifetime of Qt 4.
+\omit ### mention virtual functions that aren't virtual anymore \endomit
+\omit
+\section1 QFile
+The QFile::readLine(QString&, Q_ULONG) method from qt3 has been removed
+in qt4, but this change in the QFile interface is not documented in the
+porting documentation as of qt-4.0.0-b1.
+\endomit
+\section1 QFileDialog
+The QFileDialog class in Qt 4 has been totally rewritten. It
+provides most of the functionality of the old \c QFileDialog
+class, but with a different API. Some functionality, such as the
+ability to preview files, is expected to be added in a later Qt 4
+release.
+The old \c QFileDialog, \c QFileIconProvider, and \c QFilePreview
+classes has been renamed Q3FileDialog, Q3FileIconProvider, and
+Q3FilePreview and have been moved to Qt3Support. You can use them
+if you need some functionality not provided yet by the new
+QFileDialog class.
+The following table lists which functions have been renamed or
+removed in Qt 4.
+\table
+\header \o Old function \o Qt 4 equivalent
+\row \o Q3FileDialog::addFilter(const QString &) \o See remark below
+\row \o Q3FileDialog::addLeftWidget(QWidget *) \o N/A
+\row \o Q3FileDialog::addRightWidget(QWidget *) \o N/A
+\row \o Q3FileDialog::addToolButton(QAbstractButton *, bool separator) \o N/A
+\row \o Q3FileDialog::addWidgets(QLabel *, QWidget *, QPushButton *) \o N/A
+\row \o Q3FileDialog::dir() \o QFileDialog::directory()
+\row \o Q3FileDialog::dirPath() \o QFileDialog::directory().path()
+\row \o Q3FileDialog::iconProvider() \o N/A
+\row \o Q3FileDialog::isContentsPreviewEnabled() \o N/A
+\row \o Q3FileDialog::isInfoPreviewEnabled() \o N/A
+\row \o Q3FileDialog::previewMode() \o N/A
+\row \o Q3FileDialog::rereadDir() \o N/A
+\row \o Q3FileDialog::resortDir() \o N/A
+\row \o Q3FileDialog::selectAll(bool) \o N/A
+\row \o Q3FileDialog::setContentsPreview(QWidget *, Q3FilePreview *) \o N/A
+\row \o Q3FileDialog::setContentsPreviewEnabled(bool) \o N/A
+\row \o Q3FileDialog::setDir(const QString &) \o QFileDialog::setDirectory(const QString &)
+\row \o Q3FileDialog::setFilters(const char **) \o Q3FileDialog::setFilters(const QStringList &)
+\row \o Q3FileDialog::setIconProvider(Q3FileIconProvider *) \o N/A
+\row \o Q3FileDialog::setInfoPreview(QWidget *, Q3FilePreview *) \o N/A
+\row \o Q3FileDialog::setInfoPreviewEnabled(bool) \o N/A
+\row \o Q3FileDialog::setPreviewMode(PreviewMode) \o N/A
+\row \o Q3FileDialog::setSelectedFilter(const QString &) \o QFileDialog::selectFilter(const QString &)
+\row \o Q3FileDialog::setSelectedFilter(int) \o See remark below
+\row \o Q3FileDialog::setSelection(const QString &) \o QFileDialog::selectFile(const QString &)
+\row \o Q3FileDialog::setShowHiddenFiles(bool) \o showHidden()
+\row \o Q3FileDialog::setUrl(const QUrlOperator &) \o N/A
+\row \o Q3FileDialog::showHiddenFiles() \o N/A
+\row \o Q3FileDialog::url() \o QUrl::fromLocalFile(QFileDialog::directory())
+\header \o Old signals \o Qt 4 equivalent
+\row \o Q3FileDialog::fileHighlighted(const QString &) \o N/A
+\row \o Q3FileDialog::fileSelected(const QString &) \o QFileDialog::filesSelected(const QStringList &)
+\row \o Q3FileDialog::dirEntered(const QString &) \o N/A
+\row \o Q3FileDialog::filterSelected(const QString &) \o N/A
+\endtable
+Remarks:
+\list 1
+\o  The Q3FileDialog::addFilter(const QString &) function has no
+direct equivalent in the new QFileDialog. Use
+QFileDialog::setFilters() instead.
+\oldcode
+fileDialog->addFilter(tr("JPEG files (*.jpg *.jpeg)"));
+\newcode
+QStringList filters = fileDialog->filters();
+filters << tr("JPEG files (*.jpg *.jpeg)");
+fileDialog->setFilters(filters);
+\endcode
+\o  The Q3FileDialog::setSelectedFilter(int) overload has no direct
+equivalent in the new QFileDialog. Use
+QFileDialog::selectFilter(const QString &) instead.
+\oldcode
+fileDialog->setSelectedFilter(3);
+\newcode
+fileDialog->selectFilter(fileDialog->filters().at(3));
+\endcode
+\endlist
+There are no equivalent virtual functions to the two
+Q3FileDialog::setSelectedFilter() virtual functions in the QFileDialog
+API. In addition, these functions have been renamed or removed, as
+described above.
+\section1 QFocusData
+The QFocusData class is not available in Qt 4. Some of its
+functionality is available via the QWidget::nextInFocusChain()
+and QWidget::focusNextPrevChild() functions.
+\section1 QFocusEvent
+The setReason() function is no longer present in Qt 4. It is
+necessary to define the reason when constructing a focus event.
+\section1 QFont
+\c QFont::Script has been moved to QFontDatabase::WritingSystem.
+\section1 QFrame
+The QFrame class has been made more lightweight in Qt 4, by
+reducing the number of properties and virtual functions. The
+reduction in the number of virtual functions is significant
+because QFrame is the base class of many Qt classes.
+Here's an overview of the changes:
+\list
+\o  QFrame no longer has a \c margin property (which wasn't
+honored by Qt's layout managers anyway).
+\o  QFrame no longer has a frameChanged() function, reimplement
+QFrame::resizeEvent() instead.
+\o  QFrame used to have drawFrame(QPainter *) and
+drawContents(QPainter *) virtual functions. These are now
+gone. In Qt 4, the frame is drawn by the QFrame::paintEvent()
+function. If you want to change the way QFrame paints itself,
+reimplement this function. To draw the contents of the frame,
+reimplement QFrame:paintEvent() and call the base class
+implementation of the function before you use the
+\l {QWidget::}{contentsRect()} function inherited from QWidget,
+to retrieve the rectangle to paint on.
+\endlist
+To help with porting, the Qt3Support library contains a Q3Frame
+class that inherits QFrame and provides a similar API to the old
+QFrame class. If you derived from QFrame in your application, you
+might want to use Q3Frame as a base class as a first step in the
+porting process, and later move on to the new QFrame class.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QFrame virtual member functions in Qt 3 that are no longer
+virtual in Qt 4.
+\section1 QFtp
+QFtp no longer inherits from QNetworkProtocol. See the
+\l{#qnetworkprotocol.section}{section on QNetworkProtocol} for
+details.
+The old \c QFtp class has been renamed Q3Ftp and moved to the
+Qt3Support library.
+\target qglayoutiterator.section
+\section1 QGLayoutIterator
+The QGLayoutIterator class no longer exists in Qt 4. This makes
+only a difference if you implemented custom layout managers
+(i.e., QLayout subclasses).
+The new approach is much simpler: It consists in reimplementing
+QLayout::itemAt() and QLayout::takeAt(). These functions operate
+on indexes, eliminating the need for a layout iterator class.
+\section1 QGrid
+The \c QGrid class is now only available as Q3Grid in Qt 4. You
+can achieve the same result as \c QGrid by creating a QWidget
+with a grid layout:
+\oldcode
+QGrid *grid = new QGrid(2, Qt::Horizontal);
+QPushButton *child1 = new QPushButton(grid);
+QPushButton *child2 = new QPushButton(grid);
+QPushButton *child3 = new QPushButton(grid);
+QPushButton *child4 = new QPushButton(grid);
+\newcode
+QWidget *grid = new QWidget;
+QPushButton *child1 = new QPushButton(grid);
+QPushButton *child2 = new QPushButton(grid);
+QPushButton *child3 = new QPushButton(grid);
+QPushButton *child4 = new QPushButton(grid);
+QVBoxLayout *layout = new QVBoxLayout;
+layout->addWidget(child1, 0, 0);
+layout->addWidget(child2, 0, 1);
+layout->addWidget(child3, 1, 0);
+layout->addWidget(child4, 1, 1);
+grid->setLayout(layout);
+\endcode
+\section1 QGridLayout
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QGridLayout virtual member functions in Qt 3 that are no
+longer virtual in Qt 4.
+\section1 QGridView
+The \c QGridView class has been renamed Q3GridView and moved to
+the Qt3Support library. In Qt 4, we recommend that
+you use QTableView or QAbstractItemView for presenting tabular
+data.
+See \l{Model/View Programming} for an overview of the new item
+view classes.
+\target qgroupbox.section
+\section1 QGroupBox
+The QGroupBox class has been redesigned in Qt 4. Many of the
+features of the old \c QGroupBox class can be obtained by using
+the Q3GroupBox class from the Qt3Support library.
+The new QGroupBox is more lightweight. It doesn't attempt to
+duplicate functionality already provided by QGridLayout, and it
+does not inherit from QFrame. As a result, the following members
+have been removed:
+\list
+\o Q3GroupBox::setColumns(), Q3GroupBox::columns()
+\o Q3GroupBox::setOrientation(), Q3GroupBox::orientation()
+\o Q3GroupBox::setInsideMargin(), Q3GroupBox::insideMargin()
+\o Q3GroupBox::addSpace()
+\endlist
+Naturally, the \c columns and \c orientation properties have also
+been removed.
+If you rely on some of the missing functionality in your
+application, you can use Q3GroupBox instead of QGroupBox as a
+help to porting.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of QGroupBox virtual member functions in Qt 3 that are no
+longer virtual in Qt 4.
+\section1 QHBox
+The \c QHBox class is now only available as Q3HBox in Qt 4. You
+can achieve the same result as \c QHBox by creating a QWidget
+with an horizontal layout:
+\oldcode
+QHBox *hbox = new QHBox;
+QPushButton *child1 = new QPushButton(hbox);
+QPushButton *child2 = new QPushButton(hbox);
+\newcode
+QWidget *hbox = new QWidget;
+QPushButton *child1 = new QPushButton;
+QPushButton *child2 = new QPushButton;
+QHBoxLayout *layout = new QHBoxLayout;
+layout->addWidget(child1);
+layout->addWidget(child2);
+hbox->setLayout(layout);
+\endcode
+Note that child widgets are not automatically placed into the widget's
+layout; you will need to manually add each widget to the QHBoxLayout.
+\section1 QHeader
+The \c QHeader class has been renamed Q3Header and moved to
+the Qt3Support library. In Qt 4, it is replaced
+by the QHeaderView class.
+See \l{Model/View Programming} for an overview of the new item
+view classes.
+\section1 QHGroupBox
+The \c QHGroupBox class has been renamed Q3HGroupBox and moved to
+the Qt3Support library.
+Qt 4 does not provide a specific replacement class for \c QHGroupBox
+since QGroupBox is designed to be a generic container widget. As a
+result, you need to supply your own layout for any child widgets.
+See \l{#QGroupBox} for more information about porting code that uses
+group boxes.
+\section1 QHttp
+QHttp no longer inherits from QNetworkProtocol. See the See the
+\l{#qnetworkprotocol.section}{section on QNetworkProtocol} for
+details.
+The old \c QHttp, \c QHttpHeader, \c QHttpRequestHeader, and \c
+QHttpResponseHeader classes have been renamed Q3Http,
+Q3HttpHeader, Q3HttpRequestHeader, and Q3HttpResponseHeader  and
+have been moved to the Qt3Support library.
+\section1 QIconFactory
+The QIconFactory class is no longer part of Qt. It has been replaced by
+the QIconEngine class.
+\section1 QIconSet
+The QIconSet class is no longer part of Qt. It has been replaced by
+the QIcon class.
+\section1 QIconView
+The \c QIconView, \c QIconViewItem, \c QIconDrag, and \c
+QIconDragItem classes has been renamed Q3IconView,
+Q3IconViewItem, Q3IconDrag, and Q3IconDragItem and moved to the
+Qt3Support library. New Qt applications should use
+QListWidget or its base class QListView instead, and call
+QListView::setViewMode(QListView::IconMode) to obtain an "icon
+view" look.
+See \l{Model/View Programming} for an overview of the new item
+view classes.
+\omit
+###
+\section1 QImage
+QImage::fromMimeSource(const QString &) -> qImageFromMimeSource(const QString &)
+\endomit
+\section1 QImageDrag
+The \c QImageDrag class has been renamed Q3ImageDrag and moved to
+the Qt3Support library. In Qt 4, use QMimeData
+instead and call QMimeData::setImage() to set the image.
+See \l{Porting to Qt 4 - Drag and Drop} for a comparison between
+the drag and drop APIs in Qt 3 and Qt 4.
+\section1 QImageIO
+The \c QImageIO class has been split into two classes:
+QImageReader and QImageWriter. The table below shows the
+correspondance between the two APIs:
+\table
+\header \o Qt 3 function              \o Qt 4 equivalents
+\row    \o QImageIO::description()    \o QImageWriter::text()
+\row    \o QImageIO::fileName()       \o QImageReader::fileName() and QImageWriter::fileName()
+\row    \o QImageIO::format()         \o QImageReader::format() and QImageWriter::format()
+\row    \o QImageIO::gamma()          \o QImageWriter::gamma()
+\row    \o QImageIO::image()          \o Return value of QImageReader::read()
+\row    \o QImageIO::inputFormats()   \o QImageReader::supportedImageFormats()
+\row    \o QImageIO::ioDevice()       \o QImageReader::device() and QImageWriter::device()
+\row    \o QImageIO::outputFormats()  \o QImageWriter::supportedImageFormats()
+\row    \o QImageIO::parameters()     \o N/A
+\row    \o QImageIO::quality()        \o QImageWriter::quality()
+\row    \o QImageIO::read()           \o QImageReader::read()
+\row    \o QImageIO::setDescription() \o QImageWriter::setText()
+\row    \o QImageIO::setFileName()    \o QImageReader::setFileName() and QImageWriter::setFileName()
+\row    \o QImageIO::setFormat()      \o QImageReader::setFormat() and QImageWriter::setFormat()
+\row    \o QImageIO::setGamma()       \o QImageWriter::setGamma()
+\row    \o QImageIO::setIODevice()    \o QImageReader::setDevice() and QImageWriter::setDevice()
+\row    \o QImageIO::setImage()       \o Argument to QImageWriter::write()
+\row    \o QImageIO::setParameters()  \o N/A
+\row    \o QImageIO::setQuality()     \o QImageWriter::setQuality()
+\row    \o QImageIO::setStatus()      \o N/A
+\row    \o QImageIO::status()         \o QImageReader::error() and QImageWriter::error()
+\row    \o QImageIO::write()          \o QImageWriter::write()
+\endtable
+\section1 QIntCache<T>
+QIntCache<T> has been moved to Qt3Support. It has been replaced
+by QCache<int, T>.
+For details, read the \l{#qcache.section}{section on QCache<T>},
+mentally substituting \c int for QString.
+\section1 QIntDict<T>
+QIntDict<T> and QIntDictIterator<T> have been moved to
+Qt3Support. They have been replaced by the more modern QHash<Key,
+T> and QMultiHash<Key, T> classes and their associated iterator
+classes.
+When porting old code that uses QIntDict<T> to Qt 4, there are
+four classes that you can use:
+\list
+\o QMultiHash<int, T *>
+\o QMultiHash<int, T>
+\o QHash<int, T *>
+\o QHash<int, T>
+\endlist
+For details, read the \l{#qdict.section}{section on QDict<T>},
+mentally substituting \c int for QString.
+\target qiodevice.section
+\section1 QIODevice
+The QIODevice class's API has been simplified to make it easier
+to subclass and to make it work more smoothly with asynchronous
+devices such as QTcpSocket and QProcess.
+The following virtual functions have changed name or signature:
+\table
+\header \o Qt 3 function \o Comment
+\row \o QIODevice::at() const \o Renamed QIODevice::pos().
+\row \o QIODevice::at(Offset) \o Renamed QIODevice::seek().
+\row \o QIODevice::open(int) \o The parameter is now of type QIODevice::OpenMode.
+\row \o QIODevice::readBlock(char *, Q_ULONG) \o QIODevice::read(char *, qint64)
+\row \o QIODevice::writeBlock(const char *, Q_ULONG) \o QIODevice::write(const char *, qint64)
+\endtable
+\note QIODevice::open(QIODevice::OpenMode) is no longer pure virtual.
+The following functions are no longer virtual or don't exist anymore:
+\table
+\row \o QIODevice::getch() \o Renamed QIODevice::getChar() and implemented in terms of QIODevice::readData().
+\row \o QIODevice::putch(int) \o Renamed QIODevice::putChar() and implemented in terms of QIODevice::writeData().
+\row \o QIODevice::readAll() \o Implemented in terms of QIODevice::readData().
+\row \o QIODevice::readLine(char *, Q_ULONG) \o Implemented in terms of QIODevice::readData()
+\row \o QIODevice::ungetch(int) \o Renamed QIODevice::ungetChar() and simulated using an internal unget buffer.
+\endtable
+The \c IO_xxx flags have been revised, and the protected setFlags()
+function removed. Most of the flags have been
+eliminated because errors are best handled by implementing certain
+functions in QIODevice subclasses rather than through the base classes.
+The file access flags, such as \c IO_ReadOnly and \c IO_WriteOnly, have
+been moved to the QIODevice class to avoid polluting the global
+namespace. The table below shows the correspondence between the
+Qt 3 \c IO_xxx flags and the Qt 4 API:
+\table
+\header \o Qt 3 constant \o Qt 4 equivalent
+\row \o IO_Direct \o Use !QIODevice::isSequential() instead (notice the \e not).
+\row \o IO_Sequential \o Use QIODevice::isSequential() instead.
+\row \o IO_Combined \o N/A
+\row \o IO_TypeMask \o N/A
+\row \o IO_Raw \o QIODevice::Unbuffered
+\row \o IO_Async \o N/A
+\row \o IO_ReadOnly \o QIODevice::ReadOnly
+\row \o IO_WriteOnly \o QIODevice::WriteOnly
+\row \o IO_ReadWrite \o QIODevice::ReadWrite
+\row \o IO_Append \o QIODevice::Append
+\row \o IO_Truncate \o QIODevice::Truncate
+\row \o IO_Translate \o QIODevice::Text
+\row \o IO_ModeMask \o N/A
+\row \o IO_Open \o Use QIODevice::isOpen() instead.
+\row \o IO_StateMask \o N/A
+\row \o IO_Ok \o N/A
+\row \o IO_ReadError \o N/A
+\row \o IO_WriteError \o N/A
+\row \o IO_FatalError \o N/A
+\row \o IO_ResourceError \o N/A
+\row \o IO_OpenError \o N/A
+\row \o IO_ConnectError \o N/A
+\row \o IO_AbortError \o N/A
+\row \o IO_TimeOutError \o N/A
+\row \o IO_UnspecifiedError \o N/A
+\endtable
+\section1 QIODeviceSource
+The QIODeviceSource class was used internally in Qt 2.x in
+conjunction with QImageConsumer. It was obsoleted in Qt 3.0.
+\input porting/porting4-obsoletedmechanism.qdocinc
+\section1 QLabel
+QLabel doesn't enable word-wrap automatically anymore when rich
+text is used. You can enable it by calling
+QLabel::setWordWrap() or by setting the
+\l{QLabel::wordWrap}{wordWrap} property. The reason for this
+change is that the old behavior was confusing to many users.
+Also, QLabel no longer offers an \c autoResize property. Instead,
+you can call QWidget::setFixedSize() on the label, with
+QLabel::sizeHint() as the argument, whenever you change the
+contents of the QLabel.
+See also \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions}
+for a list of QLabel virtual member functions in Qt 3 that are no
+longer virtual in Qt 4.
+\section1 QLayout
+In Qt 4, margins are always handled by layouts; there is no
+QLayout::setSupportsMargin() function anymore.
+The deleteAllItems() function is now only available if
+\c QT3_SUPPORT is defined. If you maintain a QList of layout
+items, you can use qDeleteAll() to remove all the items in one
+go.
+In Qt 3, it was possible to change the resizing behavior for layouts
+in top-level widgets by adjusting the layout's \c resizeMode property.
+In Qt 4, this property has been replaced by the QLayout::sizeConstraint
+property which provides more control over how the layout behaves when
+resized.
+See also the \l{#qlayoutiterator.section}{section on
+QLayoutIterator} and the \l{#qglayoutiterator.section}{section on
+QGLayoutIterator}.
+\target qlayoutiterator.section
+\section1 QLayoutIterator
+The QLayoutIterator class is obsoleted in Qt 4. It is available
+only if \c QT3_SUPPORT is defined. It can be replaced by the
+QLayout::itemAt() and QLayout::takeAt() functions, which operate
+on indexes.
+\oldcode
+QLayoutIterator it = layout()->iterator();
+QLayoutItem *child;
+while ((child = it.current()) != 0) {
+if (child->widget() == myWidget) {
+it.takeCurrent();
+return;
+++it;
+}
+\newcode
+int i = 0;
+QLayoutItem *child;
+while ((child = layout()->itemAt(i)) != 0) {
+if (child->widget() == myWidget) {
+layout()->takeAt(i);
+return;
+}
+++i;
+}
+\endcode
+\section1 QLineEdit
+See \l{#properties}{Properties} for a list of QLineEdit
+properties in Qt 3 that have changed in Qt 4.
+The default value of QLineEdit's \l{QLineEdit::dragEnabled()}{dragEnabled}
+property was \c true in Qt 3. In Qt 4, the default value is \c false.
+Note that QLineEdit in Qt 4 is no longer a subclass of QFrame.
+If you need to visually style a line edit with a frame, we recommend
+either using a QFrame as a container for a QLineEdit or customizing
+the line edit with a \l{Qt Style Sheets}{style sheet}.
+\section1 QListBox
+The \c QListBox, \c QListBoxItem, \c QListBoxText, and \c
+QListBoxPixmap classes have been renamed Q3ListBox,
+Q3ListBoxItem, Q3ListBoxText, and Q3ListBoxPixmap and have been
+moved to the Qt3Support library. New Qt applications
+should use QListWidget or its base class QListView instead.
+See \l{Model/View Programming} for an overview of the new item
+view classes.
+\section1 QListView
+The \c QListView, \c QListViewItem, \c QCheckListItem, and \c
+QListViewItemIterator classes have been renamed Q3ListView,
+Q3ListViewItem, Q3CheckListItem, and Q3ListViewItemIterator, and
+have been moved to the Qt3Support library. New Qt
+applications should use one of the following four classes
+instead: QTreeView or QTreeWidget for tree-like structures;
+QListWidget or the new QListView class for one-dimensional lists.
+See \l{Model/View Programming} for an overview of the new item
+view classes.
+\section1 QLocalFs
+The \c QLocalFs class is no longer part of the public Qt API. It
+has been renamed Q3LocalFs and moved to Qt3Support. Use QDir,
+QFileInfo, or QFile instead.
+\section1 QMainWindow
+The QMainWindow class has been redesigned in Qt 4 to provide a
+more modern look and feel and more flexibility. The API has
+changed to reflect that. The old \c QMainWindow class has been
+renamed Q3MainWindow and moved to Qt3Support. See the QMainWindow
+class documentation for details.
+\omit ### More detail \endomit
+\target qmemarray.section
+\section1 QMemArray<T>
+QMemArray<T> has been moved to Qt3Support. It has been replaced
+by the QVector<T> class.
+The following table summarizes the API differences between the
+two classes.
+\table
+\row \o QMemArray::assign(const QMemArray<T> &) \o QVector::operator=()
+\row \o QMemArray::assign(const T *, uint) \o See remark below
+\row \o QMemArray::duplicate(const QMemArray &) \o QVector::operator=()
+\row \o QMemArray::duplicate(const T *, uint) \o See remark below
+\row \o QMemArray::setRawData(const T *, uint) \o N/A
+\row \o QMemArray::resetRawData(const T *, uint) \o N/A
+\row \o QMemArray::find(const T &, uint) \o QVector::indexOf(const T &, int)
+\row \o QMemArray::contains(const T &) \o QVector::count(const T &)
+\row \o QMemArray::sort() \o \l qSort()
+\row \o QMemArray::bsearch(const T &d) \o \l qBinaryFind()
+\row \o QMemArray::at(uint) \o QVector::operator[]()
+\row \o QMemArray::operator const T *() \o QVector::constData()
+\endtable
+Remarks:
+\list 1
+\o  QMemArray::assign(const T *, uint) and QMemArray::duplicate(const T *, uint)
+can be replaced by QVector::resize() and qCopy().
+\oldcode
+QMemArray<QSize> array;
+...
+array.assign(data, size);
+\newcode
+QVector<QSize> vector;
+...
+vector.resize(size);
+qCopy(data, data + size, vector.begin());
+\endcode
+\o  QMemArray is an explicitly shared class, whereas QVector is
+implicitly shared. See \l{Explicit Sharing} for more
+information.
+\endlist
+\section1 QMenuBar
+In Qt 3, QMenuBar inherited from QFrame and QMenuData; in Qt 4, it is
+a direct subclass of QWidget. Applications that provided customized
+menu bars will need to take advantage of the styling features described
+in the \l{Qt Style Sheets} document.
+It is not possible to add widgets to menu bars in Qt 4.
+\section1 QMenuData
+In Qt 4, the QMenu class provides a menu widget that can be used in all
+the places where menus are used in an application. Unlike \c QMenuData,
+QMenu is designed around the concept of actions, provided by the QAction
+class, instead of the identifiers used in Qt 3.
+In Qt 3, it was possible to insert widgets directly into menus by using
+a specific \c QMenuData::insertItem() overload. In Qt 4.2 and later,
+the QWidgetAction class can be used to wrap widgets for use in Qt 4's
+action-based APIs.
+\section1 QMessageBox
+The QMessageBox::iconPixmap() function used to return a "const
+QPixmap *". In Qt 4, it returns a QPixmap.
+\section1 QMimeSourceFactory
+The \c QMimeSourceFactory has been renamed Q3MimeSourceFactory
+and moved to the Qt3Support library. New Qt applications should
+use Qt 4's \l{Resource System} instead.
+\section1 QMovie
+The QMovie API has been revised in Qt 4 to make it more
+consistent with the other Qt classes (notably QImageReader). The
+table below summarizes the changes.
+\table
+\header \o Qt 3 function \o Qt 4 equivalent
+\row \o QMovie::connectResize() \o Connect to QMovie::resized()
+\row \o QMovie::connectStatus() \o Connect to QMovie::stateChanged()
+\row \o QMovie::connectUpdate() \o Connect to QMovie::updated()
+\row \o QMovie::disconnectResize() \o Disconnect from QMovie::resized()
+\row \o QMovie::disconnectStatus() \o Disconnect from QMovie::stateChanged()
+\row \o QMovie::disconnectUpdate() \o Disconnect from QMovie::updated()
+\row \o QMovie::finished() \o Use QMovie::state() instead
+\row \o QMovie::frameImage() \o Use QMovie::currentImage() instead
+\row \o QMovie::frameNumber() \o Use QMovie::currentFrameNumber() instead
+\row \o QMovie::framePixmap() \o Use QMovie::currentPixmap() instead
+\row \o QMovie::getValidRect() \o Use frameRect() instead
+\row \o QMovie::isNull() \o Use QMovie::isValid() instead
+\row \o QMovie::pause() \o Use QMovie::setPaused(true) instead
+\row \o QMovie::paused() \o Use QMovie::state() instead
+\row \o QMovie::pushData() \o N/A
+\row \o QMovie::pushSpace() \o N/A
+\row \o QMovie::restart() \o Use QMovie::jumpToFrame(0) instead
+\row \o QMovie::running() \o Use QMovie::state() instead
+\row \o QMovie::step() \o Use QMovie::jumpToFrame() and QMovie::setPaused() instead
+\row \o QMovie::step() \o Use QMovie::jumpToNextFrame() instead
+\row \o QMovie::steps() \o Use QMovie::currentFrameNumber() and QMovie::frameCount() instead
+\row \o QMovie::unpause() \o Use QMovie::setPaused(false) instead
+\endtable
+\section1 QMultiLineEdit
+The \c QMultiLineEdit class in Qt 3 was a convenience QTextEdit
+subclass that provided an interface compatible with Qt 2's
+QMultiLineEdit class. In Qt 4, it is called Q3MultiLineEdit, it
+inherits Q3TextEdit, and it is part of Qt3Support. Use QTextEdit
+in new code.
+\target qnetworkprotocol.section
+\section1 QNetworkProtocol
+The QNetworkProtocol, QNetworkProtocolFactoryBase,
+QNetworkProtocolFactory<T>, and QNetworkOperation classes are no
+longer part of the public Qt API. They have been renamed
+Q3NetworkProtocol, Q3NetworkProtocolFactoryBase,
+Q3NetworkProtocolFactory<T>, and Q3NetworkOperation and have been
+moved to the Qt3Support library.
+In Qt 4 applications, you can use classes like QFtp and
+QNetworkAccessManager directly to perform file-related actions on
+a remote host.
+\section1 QObject
+QObject::children() now returns a QObjectList instead of a
+pointer to a QObjectList. See also the comments on QObjectList
+below.
+Use QObject::findChildren() (or qFindChildren() if you need MSVC 6
+compatibility) instead of QObject::queryList(). For example:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 18
+QObject::killTimers() has been removed because it was unsafe to
+use in subclass. (A subclass normally doesn't know whether the
+base class uses timers or not.)
+The \c QObject::name property has been renamed
+QObject::objectName.
+\c QObject::objectTrees() has been removed. If you are primarly
+interested in widgets, use QApplication::allWidgets() or
+QApplication::topLevelWidgets().
+\section1 QObjectDictionary
+The QObjectDictionary class is a synonym for
+QAsciiDict<QMetaObject>. See the \l{#qasciidict.section}{section
+on QAsciiDict<T>}.
+\section1 QObjectList
+In Qt 3, the QObjectList class was a typedef for
+QPtrList<QObject>. In Qt 4, it is a typedef for QList<QObject *>.
+See the \l{#qptrlist.section}{section on QPtrList<T>}.
+\section1 QPaintDevice
+To reimplement painter backends one previously needed to reimplement
+the virtual function QPaintDevice::cmd(). This function is taken out
+and should is replaced with the function QPaintDevice::paintEngine()
+and the abstract class QPaintEngine. QPaintEngine provides virtual
+functions for all drawing operations that can be performed on a
+painter backend.
+bitBlt() and copyBlt() are now only compatibility functions. Use
+QPainter::drawPixmap() instead.
+\section1 QPaintDeviceMetrics
+All functions that used to be provided by the \c
+QPaintDeviceMetrics class have now been moved to QPaintDevice.
+\oldcode
+QPaintDeviceMetrics metrics(widget);
+int deviceDepth = metrics.depth();
+\newcode
+int deviceDepth = widget->depth();
+\endcode
+For compatibility, the old \c QPaintDeviceMetrics class has been
+renamed Q3PaintDeviceMetrics and moved to Qt3Support.
+\section1 QPainter
+The QPainter class has undergone some changes in Qt 4 because of
+the way rectangles are drawn. In Qt 4, the result of drawing a
+QRect with a pen width of 1 pixel is 1 pixel wider and 1 pixel
+taller than in Qt 3.
+For compatibility, we provide a Q3Painter class in Qt3Support
+that provides the old semantics. See the Q3Painter documentation
+for details and for the reasons why we had to make this change.
+The \l{http://qt.nokia.com/doc/3.3/qpainter.html#CoordinateMode-enum}{QPainter::CoordinateMode}
+enum has been removed in Qt 4. All clipping
+operations are now defined using logical coordinates and are subject
+to transformation operations.
+The
+\l{http://qt.nokia.com/doc/3.3/qpainter.html#RasterOP-enum}{QPainter::RasterOP}
+enum has been replaced with QPainter::CompositionMode.
+\section1 QPicture
+In Qt 3, a QPicture could be saved in the SVG file format. In Qt
+4, the SVG support is provided by the QtSvg module, which
+includes classes for \e displaying the contents of SVG files.
+If you would like to generate SVG files, you can use the Q3Picture
+compatibility class or the QSvgGenerator class introduced in Qt 4.3.
+\section1 QPixmap
+The mask() function has been changed to return a reference to a QBitmap
+rather than a pointer. As a result, it is no longer possible simply to
+test for a null pointer when determining whether a pixmap has a mask.
+Instead, you need to explicitly test whether the mask bitmap is null or
+not.
+\oldcode
+if (pixmap.mask())
+widget->setMask(*pixmap.mask());
+\newcode
+if (!pixmap.mask().isNull())
+widget->setMask(pixmap.mask());
+\endcode
+The \c QPixmap::setOptimization() and \c QPixmap::setDefaultOptimization()
+mechanism is no longer available in Qt 4.
+\omit
+QPixmap::fromMimeSource(const QString &) -> qPixmapFromMimeSource(const QString &)
+\endomit
+\section1 QPointArray
+The \c QPointArray class has been renamed QPolygon in Qt 4 and
+has undergone significant changes. In Qt 3, \c QPointArray
+inherited from QMemArray<QPoint>. In Qt 4, QPolygon inherits from
+QVector<QPoint>. Everything mentioned in the
+\l{#qmemarray.section}{section on QMemArray<T>} apply for
+QPointArray as well.
+The Qt3Support library contains a Q3PointArray class
+that inherits from QPolygon and provides a few functions that
+existed in \c QPointArray but no longer exist in QPolygon. These
+functions include Q3PointArray::makeArc(),
+Q3PointArray::makeEllipse(), and Q3PointArray::cubicBezier().
+In Qt 4, we recommend that you use QPainterPath for representing
+arcs, ellipses, and Bezier curves, rather than QPolygon.
+The QPolygon::setPoints() and QPolygon::putPoints() functions
+return \c void in Qt 4. The corresponding Qt 3 functions returned
+a \c bool indicating whether the array was successfully resized
+or not. This can now be checked by checking QPolygon::size()
+after the call.
+\omit
+X11 Specific:
+::appDisplay() -> QX11Info::display()
+QPaintDevice::x11Display() -> QX11Info::display()
+QPaintDevice::x11AppDisplay() -> QX11Info::display()
+QPaintDevice::x11Screen() -> QX11Info::appScreen()
+QPaintDevice::x11AppScreen() -> ???
+QPaintDevice::x11Depth() -> QX11Info::appDepth()
+QPaintDevice::x11ColorMap() -> QX11Info::appColorMap()
+QPaintDevice::x11DefaultColorMap() -> ???
+QPaintDevice::x11Visual() -> QX11Info::appVisual()
+QPaintDevice::x11DefaultVisual() -> ???
+QPaintDevice::x11AppDpiX() -> QX11Info::appDpiX()
+QPaintDevice::x11AppDpiY() -> QX11Info::appDpiY()
+QPaintDevice::x11SetAppDpiX() -> QX11Info::setAppDpiX()
+QPaintDevice::x11SetAppDpiY() -> QX11Info::setAppDpiY()
+QPaintDevice::x11AppDepth() -> ???
+QPaintDevice::x11AppCells() -> ???
+QPaintDevice::x11AppRootWindow() -> ???
+QPaintDevice::x11AppColorMap() -> ???
+QPaintDevice::x11AppDefaultColorMap() -> ???
+QPaintDevice::x11AppVisual() -> ???
+QPaintDevice::x11AppDefaultVisual() -> ???
+End of X11 Specific
+\endomit
+\section1 QPopupMenu
+For most purposes, QPopupMenu has been replaced by QMenu in Qt
+4. For compatibility with older applications, Q3PopupMenu provides
+the old API and features that are specific to pop-up menus. Note
+that, when using Q3PopupMenu, the menu's actions must be \l
+{Q3Action}s.
+In Qt 3, it was common practice to add entries to pop-up menus using the
+insertItem() function, maintaining identifiers for future use; for
+example, to dynamically change menu items.
+In Qt 4, menu entries are completely represented
+by actions for consistency with other user interface components, such as
+toolbar buttons. Create new menus with the QMenu class, and use the
+overloaded QMenu::addAction() functions to insert new entries.
+If you need to manage a set of actions created for a particular menu,
+we suggest that you construct a QActionGroup and add them to that.
+The \l{Main Window Examples} provided
+show how to use Qt's action system to construct menus, toolbars, and other
+common user interface elements.
+\section1 QPrinter
+The QPrinter class now expects printing to be set up from a
+QPrintDialog.
+\section1 QProcess
+The QProcess class has undergone major improvements in Qt 4. It
+now inherits QIODevice, which makes it possible to combine
+QProcess with a QTextStream or a QDataStream.
+The old \c QProcess class has been renamed Q3Process and moved to
+the Qt3Support library.
+\section1 QProgressBar
+The QProgressBar API has been significantly improved in Qt 4. The
+old \c QProgressBar API is available as Q3ProgressBar in the
+Qt3Support library.
+\section1 QProgressDialog
+The QProgressDialog API has been significantly improved in Qt 4.
+The old \c QProgressDialog API is available as Q3ProgressDialog
+in the Qt3Support library.
+See \l{#properties}{Properties} for a list of QProgressDialog
+properties in Qt 3 that have changed in Qt 4.
+\section1 QPtrCollection<T>
+The \c QPtrCollection<T> abstract base class has been renamed
+Q3PtrCollection<T> moved to the Qt3Support library.
+There is no direct equivalent in Qt 4.
+\omit
+###
+The QPtrCollection entry is unsatisfactory. The xref is missing
+its list and saying "no direct equivalent" with so suggestions
+seems feeble.
+\endomit
+See \l{Generic Containers} for a list of Qt 4 containers.
+\section1 QPtrDict<T>
+\c QPtrDict<T> and \c QPtrDictIterator<T> have been renamed
+Q3PtrDict<T> and Q3PtrDictIterator<T> and have been moved to the
+Qt3Support library. They have been replaced by the
+more modern QHash<Key, T> and QMultiHash<Key, T> classes and
+their associated iterator classes.
+When porting old code that uses Q3PtrDict<T> to Qt 4, there are
+four classes that you can use:
+\list
+\o QMultiHash<void *, T *>
+\o QMultiHash<void *, T>
+\o QHash<void *, T *>
+\o QHash<void *, T>
+\endlist
+(You can naturally use other types than \c{void *} for the key
+type, e.g. \c{QWidget *}.)
+To port Q3PtrDict<T> to Qt 4, read the \l{#qdict.section}{section
+on QDict<T>}, mentally substituting \c{void *} for QString.
+\target qptrlist.section
+\section1 QPtrList<T>
+QPtrList<T>, QPtrListIterator<T>, and QPtrListStdIterator<T> have
+been moved to the Qt3Support library. They have been
+replaced by the more modern QList and QLinkedList classes and
+their associated iterator classes.
+When porting to Qt 4, you have the choice of using QList<T> or
+QLinkedList<T> as alternatives to QValueList<T>. QList<T> has an
+index-based API and provides very fast random access
+(QList::operator[]), whereas QLinkedList<T> has an iterator-based
+API.
+The following table summarizes the API differences between
+QPtrList<T> and QList<T *>:
+\table
+\header \o QPtrList function \o QList equivalent
+\row \o QPtrList::contains(const T *) \o QList::count(T *)
+\row \o QPtrList::containsRef(const T *) \o QList::count(T *)
+\row \o QPtrList::find(const T *) \o See remark below
+\row \o QPtrList::findRef(const T *) \o See remark below
+\row \o QPtrList::getFirst() \o QList::first()
+\row \o QPtrList::getLast() \o QList::last()
+\row \o QPtrList::inSort(const T *) \o N/A
+\row \o QPtrList::remove(const T *) \o QList::removeAll(T *)
+\row \o QPtrList::remove(uint) \o QList::removeAt(int)
+\row \o QPtrList::removeNode(QLNode *) \o N/A
+\row \o QPtrList::removeRef(const T *) \o QList::removeAll(T *)
+\row \o QPtrList::sort() \o See remark below
+\row \o QPtrList::takeNode(QLNode *) \o N/A
+\row \o QPtrList::toVector(QGVector *) \o See remark below
+\endtable
+Remarks:
+\list 1
+\o  QPtrList::toVector(QGVector *) can be replaced by
+QVector::resize() and qCopy().
+\oldcode
+QPtrList<QWidget> list;
+...
+QPtrVector<QWidget> vector;
+list.toVector(&vector);
+\newcode
+QList<QWidget *> list;
+...
+QVector<QWidget *> vector;
+vector.resize(list.size());
+qCopy(list.begin(), list.end(), vector.begin());
+\endcode
+\o  QPtrList::sort() relied on the virtual compareItems() to
+sort items. In Qt 4, you can use \l qSort() instead and pass
+your "compare item" function as an argument.
+\o  QPtrList::find(const T *) returns an iterator, whereas
+QList::indexOf(T *) returns an index. To convert an index
+into an iterator, add the index to QList::begin().
+\o  QPtrList::removeFirst() and QPtrList::removeLast() return a \c
+bool that indicates whether the element was removed or not.
+The corresponding QList functions return \c void. You can
+achieve the same result by calling QList::isEmpty() before
+attempting to remove an item.
+\endlist
+If you use QPtrList's auto-delete feature (by calling
+QPtrList::setAutoDelete(true)), you need to do some more work.
+You have two options: Either you call \c delete yourself whenever
+you remove an item from the container, or you can use QList<T>
+instead of QList<T *> (i.e. store values directly instead of
+pointers to values). Here, we'll see when to call \c delete.
+\omit
+(See \l{What's Wrong with Auto-Delete} for an explanation of why
+the Qt 4 containers don't offer that feature.)
+\endomit
+The following table summarizes the idioms that you need to watch
+out for if you want to call \c delete yourself.
+\table
+\header \o QPtrList idiom \o QList idiom
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 19
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 20
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 21
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 22
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 23
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 24
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 25
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 26
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 27
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 28
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 29
+(removes the current item)
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 30
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 31
+(also called from QPtrList's destructor)
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 32
+In 99% of cases, the following idiom also works:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 33
+However, it may lead to crashes if \c list is referenced from
+the value type's destructor, because \c list contains
+dangling pointers until clear() is called.
+\endtable
+Be aware that QPtrList's destructor automatically calls clear().
+If you have a QPtrList data member in a custom class and use the
+auto-delete feature, you will need to call \c delete on all the
+items in the container from your class destructor to avoid a
+memory leak.
+QPtrList had the concept of a "current item", which could be used
+for traversing the list without using an iterator. When porting
+to Qt 4, you can use the Java-style QListIterator<T *> (or
+QMutableListIterator<T *>) class instead. The following table
+summarizes the API differences:
+\table
+\header \o QPtrList function \o QListIterator equivalent
+\row \o QPtrList::at() \o N/A
+\row \o QPtrList::current() \o QMutableListIterator::value()
+\row \o QPtrList::currentNode() \o N/A
+\row \o QPtrList::findNext(const T *) \o QListIterator::findNext(const T *)
+\row \o QPtrList::findNextRef(const T *) \o QListIterator::findNext(const T *)
+\row \o QPtrList::first() \o QPtrList::toFront()
+\row \o QPtrList::last() \o QPtrList::toBack()
+\row \o QPtrList::next() \o QPtrList::next()
+\row \o QPtrList::prev() \o QPtrList::previous()
+\row \o QPtrList::remove() \o QMutableListIterator::remove()
+\row \o QPtrList::take() \o QMutableListIterator::remove()
+\endtable
+Be aware that QListIterator has a different way of iterating than
+QPtrList. A typical loop with QPtrList looks like this:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 34
+Here's the equivalent QListIterator loop:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 35
+Finally, QPtrListIterator<T> must also be ported. There are no
+fewer than four iterator classes that can be used as a
+replacement: QList::const_iterator, QList::iterator,
+QListIterator, and QMutableListIterator. The most straightforward
+class to use when porting is QMutableListIterator<T *> (if you
+modify the list through the iterator) or QListIterator<T *> (if
+you don't). The following table summarizes the API differences:
+\table
+\header \o QPtrListIterator function \o Qt 4 equivalent
+\row \o QPtrListIterator::atFirst() \o !QListIterator::hasPrevious() (notice the \c{!})
+\row \o QPtrListIterator::atLast() \o !QListIterator::hasNext() (notice the \c{!})
+\row \o QPtrListIterator::count() \o QList::count() or QList::size()
+\row \o QPtrListIterator::current() \o QMutableListIterator::value()
+\row \o QPtrListIterator::isEmpty() \o QList::isEmpty()
+\row \o QPtrListIterator::toFirst() \o QListIterator::toFront()
+\row \o QPtrListIterator::toLast() \o QListIterator::toBack()
+\row \o QPtrListIterator::operator() \o QMutableListIterator::value()
+\row \o QPtrListIterator::operator*() \o QMutableListIterator::value()
+\endtable
+Again, be aware that QListIterator has a different way of
+iterating than QPtrList. A typical loop with QPtrList looks like
+this:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 36
+Here's the equivalent QListIterator loop:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 37
+Finally, QPtrListStdIterator<T> must also be ported. This is
+easy, because QList also provides STL-style iterators
+(QList::iterator and QList::const_iterator).
+\section1 QPtrQueue<T>
+QPtrQueue has been moved to the Qt3Support library.
+It has been replaced by the more modern QQueue class.
+The following table summarizes the differences between
+QPtrQueue<T> and QQueue<T *>:
+\table
+\header \o QPtrQueue function \o QQueue equivalent
+\row \o QPtrQueue::autoDelete() \o See discussion below
+\row \o QPtrQueue::count() \o QQueue::count() or QQueue::size() (equivalent)
+\row \o QPtrQueue::current() \o QQueue::head()
+\row \o QPtrQueue::remove() \o QQueue::dequeue()
+\row \o QPtrQueue::setAutoDelete() \o See discussion below
+\endtable
+If you use QPtrQueue's auto-delete feature (by calling
+QPtrQueue::setAutoDelete(true)), you need to do some more work.
+You have two options: Either you call \c delete yourself whenever
+you remove an item from the container, or you can use QQueue<T>
+instead of QQueue<T *> (i.e. store values directly instead of
+pointers to values). Here, we will show when to call \c delete.
+\omit
+(See \l{What's Wrong with Auto-Delete} for an explanation of why
+the Qt 4 containers don't offer that feature.)
+\endomit
+\table
+\header \o QPtrQueue idiom \o QQueue idiom
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 38
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 39
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 40
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 41
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 42
+(also called from QPtrQueue's destructor)
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 43
+In 99% of cases, the following idiom also works:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 44
+However, it may lead to crashes if \c queue is referenced
+from the value type's destructor, because \c queue contains
+dangling pointers until clear() is called.
+\endtable
+\section1 QPtrStack<T>
+QPtrStack has been moved to the Qt3Support library.
+It has been replaced by the more modern QStack class.
+The following table summarizes the differences between
+QPtrStack<T> and QStack<T *>:
+\table
+\header \o QPtrStack function \o QStack equivalent
+\row \o QPtrStack::autoDelete() \o See discussion below
+\row \o QPtrStack::count() \o QStack::count() or QStack::size() (equivalent)
+\row \o QPtrStack::current() \o QStack::top()
+\row \o QPtrStack::remove() \o QStack::pop()
+\row \o QPtrStack::setAutoDelete() \o See discussion below
+\endtable
+If you use QPtrStack's auto-delete feature (by calling
+QPtrStack::setAutoDelete(true)), you need to do some more work.
+You have two options: Either you call \c delete yourself whenever
+you remove an item from the container, or you can use QStack<T>
+instead of QStack<T *> (i.e. store values directly instead of
+pointers to values). Here, we will show when to call \c delete.
+\omit
+(See \l{What's Wrong with Auto-Delete} for an explanation of why
+the Qt 4 containers don't offer that feature.)
+\endomit
+\table
+\header \o QPtrStack idiom \o QStack idiom
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 45
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 46
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 47
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 48
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 49
+(also called from QPtrStack's destructor)
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 50
+In 99% of cases, the following idiom also works:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 51
+However, it may lead to crashes if \c stack is referenced
+from the value type's destructor, because \c stack contains
+dangling pointers until clear() is called.
+\endtable
+\section1 QPtrVector<T>
+QPtrVector<T> has been moved to Qt3Support. It has been replaced
+by the more modern QVector class.
+When porting to Qt 4, you can use QVector<T *> as an alternative
+to QPtrVector<T>. The APIs of QPtrVector<T> and QVector<T *> are
+somewhat similar. The main issue is that QPtrVector supports
+auto-delete whereas QVector doesn't.
+\omit
+(See \l{What's Wrong with Auto-Delete} for an explanation of why
+the Qt 4 containers don't offer that feature.)
+\endomit
+The following table summarizes the API differences between the
+two classes:
+\table
+\header \o QPtrVector function \o QVector equivalent
+\row \o QPtrVector::autoDelete() \o See discussion below
+\row \o QPtrVector::bsearch(const T *) \o \l qBinaryFind()
+\row \o QPtrVector::contains(const T *) \o QVector::count(T *)
+\row \o QPtrVector::containsRef(const T *) \o QVector::count(T *)
+\row \o QPtrVector::count() \o See remark below
+\row \o QPtrVector::insert(uint, T *) \o See remark below
+\row \o QPtrVector::isNull() \o N/A
+\row \o QPtrVector::remove(uint) \o See remark below
+\row \o QPtrVector::setAutoDelete() \o See discussion below
+\row \o QPtrVector::sort() \o \l qSort()
+\row \o QPtrVector::take(uint) \o See remark below
+\row \o QPtrVector::toList(QGList *) \o QList::QList(const QVector &)
+\endtable
+Remarks:
+\list 1
+\o  QPtrVector::insert(uint, T *) sets an item to store a certain
+pointer value. This is \e not the same as QVector::insert(int, T *),
+which creates space for the item by moving following items by
+one position. Use \c{vect[i] = ptr} to set a QVector item to
+a particular value.
+\o  QPtrVector::remove(uint) sets an item to be 0. This is \e not
+the same as QVector::removeAt(int), which entirely erases the
+item, reducing the size of the vector. Use \c{vect[i] = 0} to
+set a QVector item to 0.
+\o  Likewise, QPtrVector::take(uint) sets an item to be 0 and
+returns the previous value of the item. Again, this is easy to
+achieve using QVector::operator[]().
+\o  QPtrVector::count() returns the number of non-null items in
+the vector, whereas QVector::count() (like QVector::size())
+returns the number of items (null or non-null) in the vector.
+Fortunately, it's not too hard to simulate QPtrVector::count().
+\oldcode
+int numValidItems = vect.count();
+\newcode
+int numValidItems = vect.size() - vect.count(0);
+\endcode
+\endlist
+If you use QVector's auto-delete feature (by calling
+QVector::setAutoDelete(true)), you need to do some more work. You
+have two options: Either you call \c delete yourself whenever you
+remove an item from the container, or you use QVector<T> instead
+of QVector<T *> (i.e. store values directly instead of pointers
+to values). Here, we'll see when to call \c delete.
+The following table summarizes the idioms that you need to watch
+out for if you want to call \c delete yourself.
+\table
+\header \o QPtrVector idiom \o QVector idiom
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 52
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 53
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 54
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 55
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 56
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 57
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 58
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 59
+\row
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 60
+(also called from QPtrVector's destructor)
+\o
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 61
+In 99% of cases, the following idiom also works:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 62
+However, it may lead to crashes if \c vect is referenced from
+the value type's destructor, because \c vect contains
+dangling pointers until clear() is called.
+\endtable
+Be aware that QPtrVector's destructor automatically calls
+clear(). If you have a QPtrVector data member in a custom class
+and use the auto-delete feature, you will need to call \c delete
+on all the items in the container from your class destructor to
+avoid a memory leak.
+\section1 QPushButton
+See \l{#properties}{Properties} for a list of QPushButton
+properties in Qt 3 that have changed in Qt 4.
+\section1 QRangeControl
+In Qt 3, various "range control" widgets (QDial, QScrollBar,
+QSlider, and QSpin) inherited from both QWidget and
+\c QRangeControl.
+In Qt 4, \c QRangeControl has been replaced with the new
+QAbstractSlider and QAbstractSpinBox classes, which inherit from
+QWidget and provides similar functionality. Apart from eliminating
+unnecessary multiple inheritance, the new design allows
+QAbstractSlider to provide signals, slots, and properties.
+The old \c QRangeControl class has been renamed Q3RangeControl
+and moved to the Qt3Support library, together with
+the (undocumented) \c QSpinWidget class.
+If you use \c QRangeControl as a base class in your application,
+you can switch to use QAbstractSlider or QAbstractSpinBox instead.
+\oldcode
+class VolumeControl : public QWidget, public QRangeControl
+{
+...
+protected:
+void valueChange() {
+update();
+emit valueChanged(value());
+}
+void rangeChange() {
+update();
+}
+void stepChange() {
+update();
+}
+};
+\newcode
+class VolumeControl : public QAbstractSlider
+{
+...
+protected:
+void sliderChange(SliderChange change) {
+update();
+if (change == SliderValueChange)
+emit valueChanged(value());
+}
+};
+\endcode
+\section1 QRegExp
+The search() and searchRev() functions have been renamed to indexIn()
+and lastIndexIn() respectively.
+\section1 QRegion
+The following changes have been made to QRegion in Qt 4:
+\list
+\o  There is no longer any difference between a \e null region and
+an \e empty region. Use isEmpty() in most places where you
+would have used a null QRegion.
+\o  QRegion::rects() used to return a QMemArray<QRect>. It now returns
+a QVector<QRect>.
+\endlist
+\section1 QScrollBar
+See \l{#properties}{Properties} for a list of QScrollBar
+properties in Qt 3 that have changed in Qt 4.
+\section1 QScrollView
+The \c QScrollView class has been renamed Q3ScrollView and moved
+to the Qt3Support library. It has been replaced by
+the QAbstractScrollArea and QScrollArea classes.
+Note that Qt 4 in general uses the QScrollArea::widget() function
+where Qt 3 used QScrollView::viewport(). The rationale for this is
+that it is no longer possible to draw directly on a scroll
+area. The QScrollArea::widget() function returns the widget set on
+the scroll area.
+\c QScrollView was designed to work around the 16-bit limitation
+on widget coordinates found on most window systems. In Qt 4, this
+is done transparently for \e all widgets, so there is no longer a
+need for such functionality in \c QScrollView. For that reason,
+the new QAbstractScrollArea and QScrollArea classes are much more
+lightweight, and concentrate on handling scroll bars.
+\section1 QServerSocket
+The \c QServerSocket class has been renamed Q3ServerSocket and
+moved to the Qt3Support library. In Qt 4, it has been
+replaced by QTcpServer.
+With Q3ServerSocket, connections are accepted by reimplementing a
+virtual function (Q3ServerSocket::newConnection()). With
+QTcpServer, on the other hand, you don't need to subclass.
+Instead, simply connect to the QTcpServer::newConnection()
+signal.
+\section1 QSettings
+The QSettings class has been rewritten to be more robust and to
+respect existing standards (e.g., the INI file format). The API
+has also been extensively revised. The old API is still provided
+when Qt 3 support is enabled.
+Since the format and location of settings have changed between Qt
+3 and Qt 4, the Qt 4 version of your application won't recognize
+settings written using Qt 3.
+\section1 QShared
+The \c QShared class has been obsoleted by the more powerful
+QSharedData and QSharedDataPointer as a means of creating custom
+implicitly shared classes. It has been renamed Q3Shared moved to
+the Qt3Support library.
+An easy way of porting to Qt 4 is to include this class into your
+project and to use it instead of \c QShared:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 63
+If possible, we recommend that you use QSharedData and
+QSharedDataPointer instead. They provide thread-safe reference
+counting and handle all the reference counting behind the scenes,
+eliminating the risks of forgetting to increment or decrement the
+reference count.
+\section1 QSignal
+The QSignal class has been renamed to Q3Signal and moved to the
+Qt3Support library. The preferred approach is to create your own
+QObject subclass with a signal that has the desired signature.
+Alternatively, you can call QMetaObject::invokeMethod() if you
+want to invoke a slot.
+\section1 QSimpleRichText
+QSimpleRichText has been obsoleted by QTextDocument. It has
+bene renamed Q3SimpleRichText and moved to the Qt3Support
+library.
+Previously, you would do the following with Q3SimpleRichText:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 63a
+However, with QTextDocument, you use the following code instead:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 63b
+See \l{Rich Text Processing} for an overview of the Qt 4 rich
+text classes.
+\section1 QSlider
+The QSlider::sliderStart() and QSlider::sliderRect() functions
+have been removed.
+The slider's rect can now be retrieved using the code snippet below:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 63c
+In addition, the direction of a vertical QSlider has changed,
+i.e. the bottom is now the minimum, and the top the maximum. You
+can use the QAbstractSlider::invertedAppearance property to
+control this behavior.
+See \l{#properties}{Properties} for a list of QSlider properties
+in Qt 3 that have changed in Qt 4.
+\section1 QSocket
+The \c QSocket class has been renamed Q3Socket and moved to the
+Qt3Support library. In Qt 4, it has been replaced by
+the QTcpSocket class, which inherits most of its functionality
+from QAbstractSocket.
+\section1 QSocketDevice
+The \c QSocketDevice class has been renamed Q3SocketDevice and
+moved to the Qt3Support library. In Qt 4, there is no
+direct equivalent to Q3SocketDevice:
+\list \o If you use Q3SocketDevice in a thread to perform blocking
+network I/O (a technique encouraged by the \e{Qt Quarterly}
+article \l{http://qt.nokia.com/doc/qq/qq09-networkthread.html}
+{Unblocking Networking}), you can now use QTcpSocket, QFtp, or
+QNetworkAccessManager, which can be used from non-GUI threads.
+\o If you use Q3SocketDevice for UDP, you can now use QUdpSocket instead.
+\o If you use Q3SocketDevice for other uses, Qt 4 offers no
+alternative right now. However, there is a \c QAbstractSocketEngine
+internal class that offers a low-level socket API similar to
+Q3SocketDevice. Should the need for such functionality arise in
+Qt 4 applications, we will consider making this class public in a
+future release.
+\endlist
+\section1 QSortedList
+The QSortedList<T> class has been deprecated since Qt 3.0. In Qt
+4, it has been moved to the Qt3Support library.
+In new code, we recommend that you use QList<T> instead and use
+\l qSort() to sort the items.
+\section1 QSplitter
+The function setResizeMode() has been moved into Qt3Support. Set
+the stretch factor in the widget's size policy to get equivalent
+functionality.
+The obsolete function drawSplitter() has been removed. Use
+QStyle::drawPrimitive() to acheive similar functionality.
+\section1 QSpinBox
+See \l{#properties}{Properties} for a list of QSpinBox properties
+in Qt 3 that have changed in Qt 4.
+\section1 QSqlCursor
+The \c QSqlCursor class has been renamed Q3SqlCursor and moved to
+the Qt3Support library. In Qt 4, you can use
+QSqlQuery, QSqlQueryModel, or QSqlTableModel, depending on
+whether you want a low-level or a high-level interface for
+accessing databases.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QSqlDatabase
+QSqlDatabase is now a smart pointer that is passed around by
+value. Simply replace all QSqlDatabase pointers by QSqlDatabase
+objects.
+\section1 QSqlEditorFactory
+The \c QSqlEditorFactory class has been renamed
+Q3SqlEditorFactory and moved to Qt3Support.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QSqlError
+The enum \c{Type} was renamed to \c{ErrorType}, The values were renamed as well:
+\list
+\o None - use NoError instead
+\o Connection - use ConnectionError instead
+\o Statement - use StatementError instead
+\o Transaction - use TransactionError instead
+\o Unknown - use UnknownError instead
+\endlist
+\section1 QSqlFieldInfo
+The QSqlFieldInfo class has been moved to Qt3Support. Its
+functionality is now provided by the QSqlField class.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QSqlForm
+The \c QSqlForm class has been renamed Q3SqlForm and moved to the
+Qt3Support library.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QSqlPropertyMap
+The \c QSqlPropertyMap class has been renamed Q3SqlPropertyMap
+moved to the Qt3Support library.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QSqlQuery
+QSqlQuery::prev() was renamed to QSqlQuery::previous().
+QSqlQuery::prev() remains, but it just calls previous().
+QSqlQuery no longer has any virtual methods, i.e., exec(),
+value(), seek(), next(), prev(), first(), last(), and the
+destructor are no longer virtual.
+\section1 QSqlRecord
+QSqlRecord behaves like a vector now, QSqlRecord::insert() will
+actually insert a new field instead of replacing the existing
+one.
+\section1 QSqlRecordInfo
+The QSqlRecordInfo class has been moved to Qt3Support. Its
+functionality is now provided by the QSqlRecord class.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QSqlSelectCursor
+The \c QSqlSelectCursor class has been renamed Q3SqlSelectCursor
+and moved to the Qt3Support library.
+See \l{QtSql Module} for an overview of the new SQL classes.
+\section1 QStoredDrag
+The \c QStoredDrag class has been renamed Q3StoredDrag and moved
+to the Qt3Support library. In Qt 4, use QMimeData
+instead and call QMimeData::setData() to set the data.
+See \l{Porting to Qt 4 - Drag and Drop} for a comparison between
+the drag and drop APIs in Qt 3 and Qt 4.
+\section1 QStr(I)List
+The QStrList and QStrIList convenience classes have been
+deprecated since Qt 2.0. In Qt 4, they have been moved to the
+Qt3Support library. If you used any of these, we
+recommend that you use QStringList or QList<QByteArray> instead.
+\section1 QStr(I)Vec
+The QStrVec and QStrIVec convenience classes have been deprecated
+since Qt 2.0. In Qt 4, they have been moved to Qt3Support. If you
+used any of these, we recommend that you use QStringList or
+QList<QByteArray> instead.
+\section1 QString
+Here are the main issues to be aware of when porting QString to
+Qt 4:
+\list 1
+\o  The QString::QString(QChar) constructor performed implicit
+conversion in Qt 3. Now, you will need a cast to convert a
+QChar to a QString.
+\o  The QString::QString(const QByteArray &) constructor used to
+stop at the first '\\0' it encountered, for compatibility
+with Qt 1. This quirk has now been fixed; in Qt 4, the
+resulting QString always has the same length as the
+QByteArray that was passed to the constructor.
+\o  The QString::null static constant has been deprecated in Qt
+4. For compatibility, Qt 4 provides a QString::null symbol
+that behaves more or less the same as the old constant. The
+new idiom is to write QString() instead of QString::null, or
+to call clear().
+\oldcode
+str1 = QString::null;
+if (str2 == QString::null)
+do_something(QString::null);
+\newcode
+str1.clear();
+if (str2.isNull())
+do_something(QString());
+\endcode
+In new code, we recommend that you don't rely on the
+distinction between a null string and a (non-null) empty
+string. See \l{Distinction Between Null and Empty Strings}
+for details.
+\o  QString::latin1() and QString::ascii() have been replaced
+with QString::toLatin1() and QString::toAscii(), which return
+a QByteArray instead of a (non-reentrant) \c{const char *}.
+For consistency, QString::utf8() and QString::local8Bit(),
+which already returned a QByteArray (actually a \c QCString),
+have been renamed QString::toUtf8() and
+QString::toLocal8Bit().
+To obtain a \c{const char *} pointer to ASCII or Latin-1 data,
+use QString::toAscii() or QString::toLatin1() to obtain a
+QByteArray containing the data, then call QByteArray::constData()
+to access the character data directly. Note that the pointer
+returned by this function is only valid for the lifetime of the
+byte array; you should avoid taking a pointer to the data
+contained in temporary objects.
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 64
+In the above example, the \c goodData pointer is valid for the lifetime
+of the \c asciiData byte array. If you need to keep a copy of the data
+in a non-Qt data structure, use standard C memory allocation and string
+copying functions to do so \e before destroying the byte array.
+\o  QString::at() returned a non-const reference, whereas the
+new QString::at() returns a const value. Code like
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 65
+will no longer compile. Instead, use QString::operator[]:
+\snippet doc/src/snippets/code/doc_src_porting4.qdoc 66
+\o  The QString::contains(\e x) function (where \e x is a
+character or a string) has been renamed QString::count(\e x).
+In addition, there now exists a set of QString::contains()
+functions that returns a boolean value. Replace old calls to
+contains() with either count() or contains(), depending on
+whether you care about the specific number of occurrences of
+a character in the string or only care about whether the
+string contains that character or not.
+\o  Many functions in QString had a \c bool parameter that
+specified case sensitivity. In Qt 4, in the interest of code
+readability and maintainability, the \c bool parameters have
+been replaced by the Qt::CaseSensitivity enum, which can take
+the values Qt::CaseSensitive and Qt::CaseInsensitive.
+\oldcode
+if (url.startsWith("http:", false))
+...
+\newcode
+if (url.startsWith("http:", Qt::CaseInsensitive))
+...
+\endcode
+\o  The QString::setExpand(uint, QChar) function, which already
+was obsolete in Qt 3, is no longer available. Use
+QString::operator[] instead.
+\oldcode
+str.setExpand(32, '$');
+\newcode
+str[32] = '$';
+\endcode
+\o  The \c QT_NO_ASCII_CAST and \c QT_NO_CAST_ASCII macros have
+been renamed \c QT_NO_CAST_TO_ASCII and \c
+QT_NO_CAST_FROM_ASCII, respectively.
+\o  The QString::data() used to return the same as
+QString::ascii(). It now returns a pointer to the Unicode
+data stored in the QString object. Call QString::ascii() if
+you want the old behavior.
+\o  QString::arg() now converts two-digit place markers, allowing
+up to 99 place markers to be used in any given string.
+\o  Comparisons between QStrings and \c NULL in order to determine
+whether strings are empty are no longer allowed.
+Use \l{QString::}{isEmpty()} instead.
+\endlist
+\section1 QStringList
+QStringList now inherits from QList<QString> and can no longer be
+converted to a QValueList<QString>. Since QValueList inherits QList a
+cast will work as expected.
+This change implies some API incompatibilities for QStringList.
+For example, at() returns the string, not an iterator. See the
+\l{#qvaluelist.section}{section on QValueList} for details.
+The static QStringList::split() function for splitting strings into
+lists of smaller strings has been replaced by QString::split(),
+which returns a QStringList.
+\section1 QStyle
+The QStyle API has been overhauled and improved. Most of the information on
+why this change was done is described in \l{The Qt 4 Style API}{the QStyle overview}.
+Since QStyle is mostly used internally by Qt's widgets and styles and since
+it is not essential to the good functioning of an application, there is no
+compatibility path. This means that we have changed many enums and
+functions and the qt3to4 porting tool will not change much in your qstyle
+code. To ease the pain, we list some of the major changes here.
+QStyleOption has taken on a more central role and is no longer an optional
+argument, please see the QStyleOption documentation for more information.
+The QStyle::StyleFlags have been renamed QStyle::StateFlags and are now prefixed State_
+instead of Style_, in addition the Style_ButtonDefault flag has moved to
+QStyleOptionButton.
+The QStyle::PrimitiveElement enumeration has undergone extensive change.
+Some of the enums were moved to QStyle::ControlElement, some were removed
+and all were renamed. This renaming is not done by the qt3to4 porting tool,
+so you must do it yourself. The table below shows how things look
+now.
+\table
+\header \o Old name \o New name \o Remark
+\row \o \c PE_ButtonCommand             \o QStyle::PE_PanelButtonCommand
+\row \o \c PE_ButtonDefault             \o QStyle::PE_FrameDefaultButton
+\row \o \c PE_ButtonBevel               \o QStyle::PE_PanelButtonBevel
+\row \o \c PE_ButtonTool                \o QStyle::PE_PanelButtonTool
+\row \o \c PE_ButtonDropDown            \o QStyle::PE_IndicatorButtonDropDown
+\row \o \c PE_FocusRect                 \o QStyle::PE_FrameFocusRect
+\row \o \c PE_ArrowUp                   \o QStyle::PE_IndicatorArrowUp
+\row \o \c PE_ArrowDown                 \o QStyle::PE_IndicatorArrowDown
+\row \o \c PE_ArrowRight                \o QStyle::PE_IndicatorArrowRight
+\row \o \c PE_ArrowLeft                 \o QStyle::PE_IndicatorArrowLeft
+\row \o \c PE_SpinBoxUp                 \o QStyle::PE_IndicatorSpinUp
+\row \o \c PE_SpinBoxDown               \o QStyle::PE_IndicatorSpinDown
+\row \o \c PE_SpinBoxPlus               \o QStyle::PE_IndicatorSpinPlus
+\row \o \c PE_SpinBoxMinus              \o QStyle::PE_IndicatorSpinMinus
+\row \o \c PE_SpinBoxSlider             \o QStyle::CE_SpinBoxSlider \o uses QStyle::drawControl()
+\row \o \c PE_Indicator                 \o QStyle::PE_IndicatorCheckBox
+\row \o \c PE_IndicatorMask             \o N/A \o use QStyle::styleHint() to retrieve mask
+\row \o \c PE_ExclusiveIndicator        \o QStyle::PE_IndicatorRadioButton
+\row \o \c PE_ExclusiveIndicatorMask    \o N/A \o use QStyle::styleHint() to retrieve mask
+\row \o \c PE_DockWindowHandle          \o QStyle::PE_IndicatorToolBarHandle
+\row \o \c PE_DockWindowSeparator       \o QStyle::PE_Q3DockWindowSeparator
+\row \o \c PE_DockWindowResizeHandle    \o QStyle::PE_IndicatorDockWindowResizeHandle
+\row \o \c PE_DockWindowTitle           \o QStyle::CE_DockWindowTitle \o uses QStyle::drawControl()
+\row \o \c PE_Splitter                  \o QStyle::CE_Splitter \o uses QStyle::drawControl()
+\row \o \c PE_Panel                     \o QStyle::PE_Frame
+\row \o \c PE_PanelMenu                 \o QStyle::PE_FrameMenu
+\row \o \c PE_PanelMenuBar              \o QStyle::PE_PanelMenuBar
+\row \o \c PE_PanelDockWindow           \o QStyle::PE_FrameDockWindow
+\row \o \c PE_TabBarBase                \o QStyle::PE_FrameTabBarBase
+\row \o \c PE_HeaderSection             \o QStyle::CE_HeaderSection \o uses QStyle::drawControl()
+\row \o \c PE_HeaderArrow               \o QStyle::PE_IndicatorHeaderArrow
+\row \o \c PE_StatusBarSection          \o QStyle::PE_FrameStatusBar
+\row \o \c PE_Separator                 \o QStyle::PE_Q3Separator
+\row \o \c PE_SizeGrip                  \o QStyle::CE_SizeGrip \o uses QStyle::drawControl()
+\row \o \c PE_CheckMark                 \o QStyle::PE_IndicatorMenuCheckMark
+\row \o \c PE_ScrollBarAddLine          \o QStyle::CE_ScrollBarAddLine \o uses QStyle::drawControl()
+\row \o \c PE_ScrollBarSubLine          \o QStyle::CE_ScrollBarSubLine \o uses QStyle::drawControl()
+\row \o \c PE_ScrollBarAddPage          \o QStyle::CE_ScrollBarAddPage \o uses QStyle::drawControl()
+\row \o \c PE_ScrollBarSubPage          \o QStyle::CE_ScrollBarSubPage \o uses QStyle::drawControl()
+\row \o \c PE_ScrollBarSlider           \o QStyle::CE_ScrollBarSlider  \o uses QStyle::drawControl()
+\row \o \c PE_ScrollBarFirst            \o QStyle::CE_ScrollBarFirst   \o uses QStyle::drawControl()
+\row \o \c PE_ScrollBarLast             \o QStyle::CE_ScrollBarLast    \o uses QStyle::drawControl()
+\row \o \c PE_ProgressBarChunk          \o QStyle::PE_IndicatorProgressChunk
+\row \o \c PE_PanelLineEdit             \o QStyle::PE_FrameLineEdit
+\row \o \c PE_PanelTabWidget            \o QStyle::PE_FrameTabWidget
+\row \o \c PE_WindowFrame               \o QStyle::PE_FrameWindow
+\row \o \c PE_CheckListController       \o QStyle::PE_Q3CheckListController
+\row \o \c PE_CheckListIndicator        \o QStyle::PE_Q3CheckListIndicator
+\row \o \c PE_CheckListExclusiveIndicato\o QStyle::PE_Q3CheckListExclusiveIndicator
+\row \o \c PE_PanelGroupBox             \o QStyle::PE_FrameGroupBox
+\row \o \c PE_TreeBranch                \o QStyle::PE_IndicatorBranch
+\row \o \c PE_RubberBand                \o QStyle::CE_RubberBand \o uses QStyle::drawControl()
+\row \o \c PE_PanelToolBar              \o QStyle::PE_PanelToolBar
+\row \o \c PE_ToolBarHandle             \o QStyle::PE_IndicatorToolBarHandle
+\row \o \c PE_ToolBarSeparator          \o QStyle::PE_IndicatorToolBarSeparator
+\endtable
+The QStyle::drawControlMask() and QStyle::drawComplexControlMask()
+functions have been removed. They are replaced with a style hint.
+The QStyle::drawItem() overloads that took both a pixmap and a string have
+been removed. Use QStyle::drawItemText() and QStyle::drawItemPixmap() directly.
+The QStyle::itemRect() overload that took both a pixmap and a string is also removed, use
+either QStyle::itemTextRect() or QStyle::itemPixmapRect() instead.
+\section1 QStyleSheet
+The QStyleSheet and QStyleSheetItem classes have been renamed
+Q3StyleSheet and Q3StyleSheetItem, and have been moved to the
+Qt3Support library.
+See \l{Rich Text Processing} for an overview of the Qt 4 rich
+text classes, and \l{Qt Style Sheets} for a description of
+CSS-like style sheet support in Qt 4.2 and above.
+\section1 QSyntaxHighlighter
+The \c QSyntaxHighlighter class from Qt 3 has been renamed
+Q3SyntaxHighlighter and moved to the Qt3Support library. Since Qt
+4.1, it has been replaced by a new QSyntaxHighlighter class based
+on Qt 4's new rich text engine.
+\section1 QTabBar
+See \l{#properties}{Properties} for a list of QTabBar properties
+in Qt 3 that have changed in Qt 4.
+\section1 QTabDialog
+The \c QTabDialog class is no longer part of the public Qt API.
+It has been renamed Q3TabDialog and moved to Qt3Support. In Qt 4
+applications, you can easily obtain the same result by combining
+a QTabWidget with a QDialog and provide \l{QPushButton}s
+yourself.
+See also the \l{dialogs/tabdialog} example, which shows how to
+implement tab dialogs in Qt 4.
+\section1 QTabWidget
+See \l{#properties}{Properties} for a list of QTabWidget
+properties in Qt 3 that have changed in Qt 4.
+\section1 QTable
+The \c QTable, \c QTableItem, \c QComboTableItem, \c
+QCheckTableItem, and \c QTableSelection classes have been renamed
+Q3Table, Q3TableItem, Q3ComboTableItem, Q3CheckTableItem, and
+Q3TableSelection and moved to the Qt3Support library.
+New Qt applications should use the new QTableWidget or QTableView
+class instead.
+Some of these classes behave differently with respect to the way
+they handle \c NULL pointers. For example, Q3TableItem::setPixmap()
+no longer accepts \c NULL or 0 to indicate that the item should
+contain a null pixmap; in this case, a null pixmap should be
+constructed and passed explicitly to the function.
+See \l{Model/View Programming} for an overview of the new item
+view classes.
+\section1 QTextCodec
+The loadCharmap() and loadCharmapFromFile() functions are no longer
+available in Qt 4. You need to create your own codec if you want to
+create a codec based on a POSIX2 charmap definition.
+\section1 QTextDrag
+The \c QTextDrag class has been renamed Q3TextDrag and moved to
+the Qt3Support library. In Qt 4, use QMimeData
+instead and call QMimeData::setText() to set the data.
+See \l{Porting to Qt 4 - Drag and Drop} for a comparison between
+the drag and drop APIs in Qt 3 and Qt 4.
+\section1 QTextEdit
+The old QTextEdit and QTextBrowser classes have been renamed
+Q3TextEdit and Q3TextBrowser, and have been moved to Qt3Support.
+The new QTextEdit and QTextBrowser have a somewhat different API.
+The \c QTextEdit::setWrapPolicy() function has been renamed to \l{QTextEdit::setWordWrapMode()}{setWordWrapMode()} and the
+\c QTextEdit::setWrapColumnOrWidth() function has been renamed to \l{QTextEdit::setLineWrapColumnOrWidth()}
+{setLineWrapColumnOrWidth()}. The Q3TextEdit::setWrapPolicy() and Q3TextEdit::setWrapColumnOrWidth() still provide this
+functionality in the Q3TextEdit class.
+See \l{Rich Text Processing} for an overview of the Qt 4 rich
+text classes.
+\section1 QTextIStream
+The QTextIStream convenience class is no longer provided in Qt 4. Use
+QTextStream directly instead.
+\section1 QTextOStream
+The QTextOStream convenience class is no longer provided in Qt 4. Use
+QTextStream directly instead.
+\section1 QTextOStreamIterator
+The undocumented \c QTextOStreamIterator class has been removed
+from the Qt library. If you need it in your application, feel
+free to copy the source code from the Qt 3 \c <qtl.h> header
+file.
+\section1 QTextStream
+QTextStream has undergone a number of API and implementation enhancements,
+and some of the changes affect QTextStream's behavior:
+\list
+\o QTextStream now uses buffered writing, which means that you need to
+call QTextStream::flush(), or use the streaming manipulators \c endl or
+\c flush if you need QTextStream to flush its write buffer. The stream is
+flushed automatically if QTextStream is deleted or when the device is
+closed.
+\o QTextStream now uses buffered reading, so if you read a line from the
+stream, QTextStream will read as much as it can from the device to
+fill up its internal read buffer. This speeds up reading significantly,
+but Qt 3 code that mixed QTextStream access and direct device access
+may need to be updated.
+\o While QTextStream in Qt 3 always translated end-of-line characters from
+Windows style ("\\r\\n") to Unix style ("\\n") on Windows, QTextStream in
+Qt 4 only does this on devices opened with the \c{QIODevice::Text} mode
+(formerly \c{IO_Translate}).
+\endlist
+Note that when using a QTextStream on a QFile in Qt 4, calling
+QIODevice::reset() on the QFile will not have the expected result
+because QTextStream now buffers the file. Use the
+QTextStream::seek() function instead.
+\section1 QTextView
+The \c QTextView class has been renamed Q3TextView and moved to the
+Qt3Support library.
+\section1 QTimeEdit
+The QTimeEdit class in Qt 4 is a convenience class based on
+QDateTimeEdit. The old class has been renamed Q3TimeEdit and moved
+to the Qt3Support library.
+See \l{Porting to Qt 4 - Virtual Functions}{Virtual Functions} for
+a list of \c QTimeEdit virtual member functions in Qt 3 that are no
+longer virtual in Qt 4.
+\section1 QTimer
+Windows restricts the granularity of timers, but starting with Qt 4,
+we emulate a finer time resolution. On Windows XP we use the
+multimedia timer API, which gives us 1 millisecond resolution for
+QTimer.
+Note that other versions of Windows have a lower timer resolution,
+and that code relying on underlying system timer restrictions
+encounters no such limitations using Qt 4 (e.g., setting an
+interval of 0 millisecond results in Qt occupying all of the
+processor time when no GUI events need processing).
+\section1 QToolBar
+The old \c QToolBar class, which worked with the old \c
+QMainWindow and \c QDockArea classes and inherited from \c
+QDockWindow, has been renamed Q3ToolBar and moved to
+Qt3Support. Note that, when using Q3ToolBar, the toolbar's actions
+must be \l {Q3Action}s.
+Use the new QToolBar class in new applications.
+\note \l{Q3ToolBar}'s
+\l{Q3DockWindow::setHorizontallyStretchable()}{horizontallyStretchable}
+property can be achieved in QToolBar with
+\l{QWidget#Size Hints and Size Policies}{size policies}.
+\section1 QToolButton
+See \l{#properties}{Properties} for a list of QToolButton properties
+in Qt 3 that have changed in Qt 4.
+Note that many of the properties that could previously be set in
+the constructor must now be set separately.
+\section1 QToolTip
+The QToolTip::setGloballyEnabled() function no longer exists.
+Tooltips can be disabled by \l{QObject::installEventFilter()}{installing
+an event filter} on qApp (the unique QApplication object) to block events
+of type QEvent::ToolTip.
+\section1 QUriDrag
+The \c QUriDrag class has been renamed Q3UriDrag and moved to the
+Qt3Support library. In Qt 4, use QMimeData instead
+and call QMimeData::setUrl() to set the URL.
+See \l{Porting to Qt 4 - Drag and Drop} for a comparison between
+the drag and drop APIs in Qt 3 and Qt 4.
+\section1 QUrl
+The QUrl class has been rewritten from scratch in Qt 4 to be more
+standard-compliant. The old QUrl class has been renamed Q3Url and
+moved to the Qt3Support library.
+The new QUrl class provides an extensive list of compatibility
+functions to ease porting from Q3Url to QUrl. A few functions
+require you to change your code:
+\list
+\o Q3Url::Q3Url(const Q3Url &, const QString &, bool) can be
+simulated by combining the URLs manually (using
+QString::operator+(), for example).
+\o Q3Url::setEncodedPathAndQuery(const QString &) is replaced by
+QUrl::setPath() and QUrl::setEncodedQuery().
+\o Q3Url::encodedPathAndQuery() is replaced by QUrl::path() and
+QUrl::encodedQuery().
+\o Q3Url::isLocalFile() can be simulated by checking that
+QUrl::protocol() is "file".
+\o Q3Url::toString(bool, bool) is replaced by
+QUrl::toString(int), where the \c int parameter specifies a
+combination of \l{QUrl::FormattingOptions}{formatting
+options}.
+\endlist
+\section1 QUrlOperator
+The \c QUrlOperator class is no longer part of the public Qt API.
+It has been renamed Q3UrlOperator and moved to Qt3Support.
+From Qt 4.4, the Network Access API provides a subset of the features
+provided by \c QUrlOperator that are mostly intended for use with
+applications that use the HTTP and FTP protocols. See the
+QNetworkRequest, QNetworkReply, and QNetworkAccessManager documentation
+for further details.
+\target qvaluelist.section
+\section1 QValueList<T>
+The QValueList<T> class has been replaced by QList<T> and
+QLinkedList<T> in Qt 4. As a help when porting older Qt
+applications, the Qt3Support library contains a
+QValueList<T> class implemented in terms of the new
+QLinkedList<T>. Similarly, it contains QValueListIterator<T> and
+QValueListConstIterator<T> classes implemented in terms of
+QLinkedList<T>::iterator and QLinkedList<T>::const_iterator.
+When porting to Qt 4, you have the choice of using QList<T> or
+QLinkedList<T> as alternatives to QValueList<T>. QList<T> has an
+index-based API and provides very fast random access
+(QList::operator[]), whereas QLinkedList<T> has an iterator-based
+API.
+Here's a list of problem functions:
+\list
+\o  QValueList(const std::list<T> &) doesn't exist in QList or
+QLinkedList. You can simulate it by calling
+\l{QLinkedList::append()}{append()} in a loop.
+\o  QValueList::insert(iterator, size_type, const T& x) doesn't
+exist in QList or QLinkedList. Call
+\l{QLinkedList::insert()}{insert()} repeatedly instead.
+\o  QValueList::fromLast() doesn't exist in QList or QLinkedList. Use
+QValueList::end() instead.
+\oldcode
+for (QValueList<T>::iterator i = list.fromLast(); i != list.begin(); --i)
+do_something(*i);
+\newcode
+QLinkedList<T>::iterator i = list.end();
+while (i != list.begin()) {
+--i; // decrement i before using it
+do_something(*i);
+}
+\endcode
+\o  QValueList::append() and QValueList::prepend() return an
+iterator to the inserted item. QList's and QLinkedList's
+corresponding functions don't, but it's not a problem because
+QValueList::prepend() always returns begin() and append()
+always returns QValueList::end() - 1.
+\o  QValueList::at(\e i) return an iterator to the item at index
+\e i. This corresponds to QList::begin() + \e i.
+\o  QValueList::contains(const T &) corresponds to
+QList::count(const T &) and QLinkedList::count(const T &).
+\endlist
+\section1 QValueVector<T>
+The QValueVector<T> class has been replaced by QVector<T> in Qt
+4. As a help when porting older Qt applications, the Qt3Support
+library contains a Q3ValueVector<T> class implemented in terms of
+the new QVector<T>.
+When porting from QValueVector<T> to QVector<T>, you might run
+into the following incompatibilities:
+\list
+\o QValueVector(const std::vector<T> &) doesn't exist in QVector.
+You can simulate it by calling QVector::append()} in a loop.
+\o QValueVector::resize(int, const T &) doesn't exist in QVector.
+If you want the new items to be initialized with a particular
+value, use QVector::insert() instead.
+\o QValueVector::at() on a non-const vector returns a non-const
+reference. This corresponds to QVector::operator[]().
+\o Both QValueVector::at() functions have an \e ok parameter of
+type \c{bool *} that is set to true if the index is within
+bounds. This functionality doesn't exist in QVector; instead,
+check the index against QVector::size() yourself.
+\endlist
+See \l{Generic Containers} for an overview of the Qt 4 container
+classes.
+\section1 QVariant
+Some changes to the rest of the Qt library have
+implications on QVariant:
+\list 1
+\o The \c QVariant::ColorGroup enum value is defined only
+if \c QT3_SUPPORT is defined.
+\o The \c QVariant::IconSet enum value has been renamed
+QVariant::Icon.
+\o The \c QVariant::CString enum value is now a synonym for
+QVariant::ByteArray.
+\endlist
+Also, the QVariant(bool, int) constructor has been replaced by QVariant(bool).
+Old code like QVariant(true, 0) should be replaced with QVariant(true); otherwise,
+the QVariant(int, void *) overload might accidentally be triggered.
+Many of QVariant's convenience functions in Qt 3, such as toColor() and
+toKeySequence(), have been removed to enable QVariant to be part of the
+QtCore module. QVariant is still able to hold values of these types.
+Types which are not supported by any of the QVariant constructors can be
+stored as variants with the QVariant::fromValue() function. Types with no
+suitable convenience function for unpacking can be retrieved with the
+QVariant::value() function or passed directly to classes that implement
+the QVariant() operator.
+\table
+\header \o Qt 3 function \o Qt 4 function
+\input porting/porting4-removedvariantfunctions.qdocinc
+\endtable
+See the QVariant::Type enum for a list of types supported by QVariant.
+\section1 QVBox
+The \c QVBox class is now only available as Q3VBox in Qt 4. You
+can achieve the same result as \c QVBox by creating a QWidget
+with a vertical layout:
+\oldcode
+QVBox *vbox = new QVBox;
+QPushButton *child1 = new QPushButton(vbox);
+QPushButton *child2 = new QPushButton(vbox);
+\newcode
+QWidget *vbox = new QWidget;
+QPushButton *child1 = new QPushButton;
+QPushButton *child2 = new QPushButton;
+QVBoxLayout *layout = new QVBoxLayout;
+layout->addWidget(child1);
+layout->addWidget(child2);
+vbox->setLayout(layout);
+\endcode
+Note that child widgets are not automatically placed into the widget's
+layout; you will need to manually add each widget to the QVBoxLayout.
+\section1 QVGroupBox
+The \c QVGroupBox class has been renamed Q3VGroupBox and moved to
+the Qt3Support library.
+Qt 4 does not provide a specific replacement class for \c QVGroupBox
+since QGroupBox is designed to be a generic container widget. As a
+result, you need to supply your own layout for any child widgets.
+See \l{#QGroupBox} for more information about porting code that uses
+group boxes.
+\section1 QWhatsThis
+The QWhatsThis class has been redesigned in Qt 4. The old \c
+QWhatsThis class is available as Q3WhatsThis in Qt3Support.
+\section1 QWidget
+Widget background painting has been greatly improved, supporting
+flicker-free updates and making it possible to have
+semi-transparent widgets. This renders the following background
+handling functions obsolete:
+\list
+\o QWidget::repaint(bool noErase) - the \c noErase boolean parameter is gone
+\o QWidget::setBackgroundMode(BackgroundMode m)
+\o QWidget::backgroundBrush() const
+\o QWidget::setBackgroundPixmap(const QPixmap &pm)
+\o QWidget::backgroundPixmap() const
+\o QWidget::setBackgroundColor(const QColor &c)
+\o QWidget::backgroundColor() const
+\o QWidget::foregroundColor() const
+\o QWidget::eraseColor() const
+\o QWidget::setEraseColor(const QColor &c)
+\o QWidget::erasePixmap() const
+\o QWidget::setErasePixmap(const QPixmap &p)
+\o QWidget::paletteForegroundColor()
+\o QWidget::setPaletteForegroundColor(const QColor &c)
+\o QWidget::paletteBackgroundColor()
+\o QWidget::setPaletteBackgroundColor(const QColor &c)
+\o QWidget::paletteBackgroundPixmap() const
+\o QWidget::setPaletteBackgroundPixmap(const QPixmap &p)
+\o QWidget::erase()
+\o QWidget::erase(const QRect &r)
+\o QWidget::setBackgroundOrigin( BackgroundOrigin )
+\o QWidget::BackgroundOrigin backgroundOrigin() const
+\o QWidget::backgroundOffset()
+\endlist
+Sample code on how to do obtain similar behavior from Qt 4, previously
+handled by some of the above functions can be found in the
+\l{http://qt.nokia.com/doc/qwidget-qt3.html}{Qt 3 Support Members for QWidget}
+page.
+A widget now receives change events in its QWidget::changeEvent()
+handler. This makes the following virtual change handlers obsolete:
+\list
+\o QWidget::styleChange - use QEvent::StyleChange
+\o QWidget::enabledChange - use QEvent::EnabledChange
+\o QWidget::paletteChange - use QEvent::PaletteChange
+\o QWidget::fontChange - use QEvent::FontChange
+\o QWidget::windowActivationChange - use QEvent::ActivationChange
+\o QWidget::languageChange - use QEvent::LanguageChange
+\endlist
+The following functions were slots, but are no more:
+\list
+\o QWidget::clearFocus()
+\o QWidget::setMouseTracking()
+\o QWidget::stackUnder(QWidget*)
+\o QWidget::move(int x, int y)
+\o QWidget::move(const QPoint &)
+\o QWidget::resize(int w, int h)
+\o QWidget::resize(const QSize &)
+\o QWidget::setGeometry(int x, int y, int w, int h)
+\o QWidget::setGeometry(const QRect &)
+\o QWidget::adjustSize()
+\o QWidget::update(int x, int y, int w, int h)
+\o QWidget::update(const QRect&)
+\o QWidget::repaint(bool erase)
+\o QWidget::repaint(int x, int y, int w, int h, bool erase)
+\o QWidget::repaint(const QRect &, bool erase)
+\o QWidget::repaint(const QRegion &, bool erase)
+\o QWidget::setCaption(const QString &)
+\o QWidget::setIcon(const QPixmap &)
+\o QWidget::setIconText(const QString &)
+\endlist
+The following functions were incorrectly marked as virtual:
+\list
+\o QWidget::close(bool alsoDelete)
+\o QWidget::create(WId, bool, bool)
+\o QWidget::destroy(bool)
+\o QWidget::move(int x, int y)
+\o QWidget::reparent(QWidget *parent, WFlags, const QPoint &, bool)
+\o QWidget::resize(int w, int h)
+\o QWidget::setAcceptDrops(bool on)
+\o QWidget::setActiveWindow()
+\o QWidget::setAutoMask(bool)
+\o QWidget::setBackgroundColor(const QColor &)
+\o QWidget::setBackgroundMode(BackgroundMode)
+\o QWidget::setBackgroundOrigin(BackgroundOrigin)
+\o QWidget::setBackgroundPixmap(const QPixmap &)
+\o QWidget::setCaption(const QString &)
+\o QWidget::setCursor(const QCursor &)
+\o QWidget::setEnabled(bool)
+\o QWidget::setEraseColor(const QColor &)
+\o QWidget::setErasePixmap(const QPixmap &)
+\o QWidget::setFocus()
+\o QWidget::setFocusPolicy(FocusPolicy)
+\o QWidget::setFocusProxy(QWidget *)
+\o QWidget::setFont(const QFont &)
+\o QWidget::setGeometry(const QRect &)
+\o QWidget::setGeometry(int x, int y, int w, int h)
+\o QWidget::setIcon(const QPixmap &)
+\o QWidget::setIconText(const QString &)
+\o QWidget::setKeyCompression(bool)
+\o QWidget::setMask(const QBitmap &)
+\o QWidget::setMask(const QRegion &)
+\o QWidget::setMaximumSize(int maxw, int maxh)
+\o QWidget::setMicroFocusHint(int x, int y, int w, int h, bool, QFont *f)
+\o QWidget::setMinimumSize(int minw, int minh)
+\o QWidget::setMouseTracking(bool enable)
+\o QWidget::setPalette(const QPalette &)
+\o QWidget::setPaletteBackgroundColor(const QColor &)
+\o QWidget::setPaletteBackgroundPixmap(const QPixmap &)
+\o QWidget::setSizeIncrement(int w, int h)
+\o QWidget::setSizePolicy(QSizePolicy)
+\o QWidget::setUpdatesEnabled(bool enable)
+\o QWidget::setWState(uint)
+\o QWidget::show()
+\o QWidget::showFullScreen()
+\o QWidget::showMaximized()
+\o QWidget::showMinimized()
+\o QWidget::showNormal()
+\o QWidget::sizePolicy()
+\o QWidget::unsetCursor()
+\endlist
+The internal clearWState() function was removed. Use
+QWidget::setAttribute() instead.
+setWFlags() was renamed QWidget::setWindowFlags().
+clearWFlags() has no direct replacement. You can use
+QWidget::setAttribute() instead. For example,
+\c{setAttribute(..., false)} to clear an attribute. More information
+is available \l{http://qt.nokia.com/doc/qwidget.html#setAttribute}{here}.
+testWFlags() was renamed to \l{QWidget::testAttribute()}{testAttribute()}.
+See \l{#properties}{Properties} for a list of QWidget properties
+in Qt 3 that have changed in Qt 4.
+\section1 QWidgetFactory
+The \c QWidgetFactory class has been replaced by QFormBuilder in Qt 4.
+\section1 QWidgetIntDict
+The QWidgetIntDict class was a synonym for QIntDict<QWidget>. It
+is no longer available in Qt 4. If you link against Qt3Support,
+you can use Q3IntDict<QWidget> instead; otherwise, see the
+\l{#qdict.section}{section on QDict<T>}.
+\target qwidgetlist.section
+\section1 QWidgetList
+In Qt 3, the QWidgetList class was a typedef for
+QPtrList<QWidget>. In Qt 4, it is a typedef for QList<QWidget *>.
+See the \l{#qptrlist.section}{section on QPtrList<T>}.
+\section1 QWidgetPlugin
+The QWidgetPlugin class is no longer available in Qt 4. To create
+custom widget plugins, subclass QDesignerCustomWidgetInterface to
+provide information about the custom widget, and build a plugin in
+the way described in the \l{designer/customwidgetplugin}{Custom
+Widget Plugin} example.
+\section1 QWidgetStack
+The QWidgetStack class is no longer part of the Qt public API. It
+has been renamed Q3WidgetStack and moved to Qt3Support. In Qt 4
+applications, you can use QStackedWidget instead to obtain the
+same results.
+\section1 QWizard
+The \c QWizard class was reintroduced in Qt 4.3. See the
+\l{Trivial Wizard Example}, \l{License Wizard Example} and
+\l{Class Wizard Example} for more details.
+\section1 QWorkspace
+The \c QWorkspace in Qt 4 class requires explicit adding of MDI
+windows with QWorkspace::addWindow().
+*/
+/*!
+\page porting4-virtual-functions.html
+\title Porting to Qt 4 - Virtual Functions
+\contentspage {Porting Guides}{Contents}
+\previouspage Porting to Qt 4
+\nextpage Porting to Qt 4 - Drag and Drop
+\ingroup porting
+\brief An overview of changes to virtual functions in Qt 4.
+\section1 Virtual Functions
+Virtual functions that changed their signature in Qt 4:
+\table
+\header \o Qt 3 function signature \o Qt 4 function signature
+\input porting/porting4-modifiedvirtual.qdocinc
+\endtable
+Virtual functions that are not virtual in Qt 4:
+\table
+\header \o Qt 3 function \o Comment
+\input porting/porting4-removedvirtual.qdocinc
+\endtable
+*/