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/*!
    \page qt4-intro.html
    \title What's New in Qt 4

    \startpage index.html Qt Reference Documentation
    \nextpage The Tulip Container Classes

    This document covers the most important differences between Qt 3
    and Qt 4. Although it is not intended to be a comprehensive
    porting guide, it tells you about the most important portability
    issues that you may encounter. It also explains how to turn on Qt
    3 compatibility support.

    \tableofcontents

    \section1 New Technologies in Qt 4

    Qt 4 introduces the following core technologies:

    \list
    \o \l{The Tulip Container Classes}{Tulip}, a new set of template container classes.

    \o \l{The Interview Framework}{Interview}, a model/view architecture for item views.

    \o \l{The Arthur Paint System}{Arthur}, the Qt 4 painting framework.

    \o \l{The Scribe Classes}{Scribe}, the Unicode text renderer with a public API
    for performing low-level text layout.

    \o \l{The Qt 4 Main Window Classes}{Mainwindow}, a modern action-based
    mainwindow, toolbar, menu, and docking architecture.

    \o The new \l{The New Qt Designer}{\QD} user interface design tool.
    \endlist

    \section1 Recent Additions to Qt 4

    The following features have been added to Qt since the first release of Qt 4:

    In Qt 4.5:
    \list
    \o The WebKit browser engine included with Qt has been
       upgraded to the latest upstream (trunk) version of WebKit,
       bringing the latest features and improvements to Qt applications.
    \o Qt for Mac OS X has been substantially rewritten to use
       Apple's Cocoa API, enabling Qt applications to be deployed on
       64-bit Macintosh hardware.
    \o The QtXmlPatterns module has been extended to cover XSLT, a
       transformation language for XML documents.
    \o Qt Script introduced its debugger, 
       providing error reporting for scripts, and to let users track down
       bugs in their own scripts.
    \o Qt 4.5 includes support for writing rich text documents as
       OpenDocument files via the newly-introduced QTextDocumentWriter
       class.
    \o Qt Linguist can load and edit multiple translation
       files simultaneously.
    \o Support for ARGB top-level widgets (i.e., translucent
       windows).
    \endlist

    In Qt 4.4:
    \list
    \o \l{QtWebkit Module}{Qt WebKit integration}, making it possible for developers
    to use a fully-featured Web browser to display documents and access online
    services.
    \o A multimedia API provided by the \l{Phonon Overview}{Phonon Multimedia Framework}.
    \o \l{QtXmlPatterns Module}{XQuery and XPath} support, providing facilities for
    XML processing beyond that supported by the QtXml module.
    \o Support for embedded widgets in \l{Graphics View} scenes.
    \o The \l{Thread Support in Qt}{QtConcurrent framework} for
    concurrent programming using Qt paradigms and threading features.
    \o An \l{QtHelp Module}{improved help system} that can be used in conjunction
    with Qt Assistant or as an independent help resource manager.
    \o Printing system improvements, including the QPrinterInfo, QPrintPreviewWidget
    and QPrintPreviewDialog classes.
    \o Support for \l{Windows CE - Introduction to using Qt}{Qt for Windows CE} as
    a mainstream Qt platform.
    \o Improvements in performance of Qt for Embedded Linux and extended support for
    display hardware.
    \endlist

    In Qt 4.3:
    \list
    \o Support for different \l{The Qt 4 Main Window Classes}{main window paradigms and styles},
       such as those found in Visual Studio or KDevelop.
    \o The \l{QtScript} module, providing support for application scripting with ECMAScript.
    \o Improved graphics features, including an experimental Direct3D paint engine
       and improved provision for hardware accelerated rendering with OpenGL, and
       support for OpenGL ES in Qt for Embedded Linux.
    \o \l{QSvgGenerator}{Scalable Vector Graphics (SVG) export}, allowing SVG drawings to
       be created using the standard QPainter API.
    \o Support for arbitrary matrix transformations and set operations on painter paths.
    \o Native look and feel on Windows Vista; improved look and feel on Mac OS X.
    \o An improved \l{QMdiArea}{Multiple Document Interface (MDI)} implementation.
    \o Continuous improvements to \QD, including support for
       \l{Qt Designer's Widget Editing Mode#The Property Editor}{dynamic properties}.
    \o Support for Secure Socket Layer (SSL) communications via the QSslSocket class.
    \o Support for XML Localization Interchange File Format (XLIFF) files in \QL.
    \o A new font subsystem for Qt for Embedded Linux.
    \endlist

    In Qt 4.2:
    \list
    \o The \l{Graphics View} framework for producing interactive graphics.
    \o \l{Desktop Integration}{Desktop integration} facilities for applications.
    \o \l{Qt Style Sheets} enable easy, yet powerful customization of
       user interfaces.
    \o Support for the \l{intro-to-dbus.html}{D-Bus} Inter-Process Communication (IPC) and Remote Procedure Calling (RPC) mechanism.
    \o An \l{Undo Framework}{Undo framework} based on the
       \l{Books about GUI Design#Design Patterns}{Command pattern}.
    \o Support for model-based \l{QCompleter}{text completion} in standard and
       custom widgets.
    \o New widgets and GUI features, such as QCalendarWidget and
       QGLFramebufferObject.
    \o Classes to provide higher level application infrastructure, such as
       QFileSystemWatcher and QDataWidgetMapper.
    \endlist

    In Qt 4.1:
    \list
    \o Integrated support for rendering
    \l{The Arthur Paint System#SVG Rendering Support}{Scalable Vector Graphics}
    (SVG) drawings and animations.
    \o Support for
       \l{QWidget#Transparency and Double Buffering}{child widget transparency}
       on all platforms.
    \o A Portable Document Format (PDF) backend for Qt's printing system.
    \o A \l{QTestLib Manual}{unit testing framework} for Qt applications and
       libraries.
    \o Modules for \l{QtDesigner}{extending \QD} and
       \l{QtUiTools}{dynamic user interface building}.
    \o New \l{Proxy Models}{proxy models} to enable view-specific sorting and
       filtering of data displayed using item views.
    \o Support for \l{Installing Qt on Mac OS X}{universal binaries} on Mac OS X.
    \o Additional features for developers using \l{QtOpenGL}{OpenGL}, such as
    support for pixel and sample buffers.
    \o A flexible \l{QSyntaxHighlighter}{syntax highlighting class} based on the
       \l{Scribe} rich text framework.
    \o Support for \l{QNetworkProxy}{network proxy} servers using the SOCKS5
       protocol.
    \o Support for OLE verbs and MIME data handling in \l{ActiveQt}.
    \endlist

    For more information about improvements in each Qt release, see
    the \l{http://qt.nokia.com/developer/changes/}
    {detailed lists of changes}.

    \section1 Significant Improvements

    The following modules have been significantly improved for Qt 4:

    \list
    \o A fully cross-platform \l{accessibility}
    module, with support for the emerging SP-API Unix standard in
    addition to Microsoft and Mac Accessibility.
    \o The \l{qt4-sql.html}{SQL module}, which is now based on the
    Interview model/view framework.
    \o The \l{qt4-network.html}{network module}, with better support
    for UDP and synchronous sockets.
    \o The \l{qt4-styles.html}{style API}, which is now decoupled from
    the widgets, meaning that you can draw any user interface element on
    any device (widget, pixmap, etc.).
    \o Enhanced \l{qt4-threads.html}{thread support}, with signal-slot
    connections across threads and per-thread event loops.
    \o A new \l{resource system} for embedding images
    and other resource files into the application executable.
    \endlist

    \section1 Build System

    Unlike previous Qt releases, Qt 4 is a collection of smaller
    libraries:

    \table
    \header \o Library          \o Description
    \row    \o \l{QtCore}       \o Core non-GUI functionality
    \row    \o \l{QtGui}        \o Core GUI functionality
    \row    \o \l{QtNetwork}    \o Network module
    \row    \o \l{QtOpenGL}     \o OpenGL module
    \row    \o \l{QtSql}        \o SQL module
    \row    \o \l{QtSvg}        \o SVG rendering classes
    \row    \o \l{QtXml}        \o XML module
    \row    \o \l{Qt3Support}   \o Qt 3 support classes
    \row    \o \l{QAxContainer} \o ActiveQt client extension
    \row    \o \l{QAxServer}    \o ActiveQt server extension
    \row    \o \l{QtAssistant}  \o Classes for launching Qt Assistant
    \row    \o \l{QtDesigner}   \o Classes for extending and embedding Qt Designer
    \row    \o \l{QtUiTools}       \o Classes for dynamic GUI generation
    \row    \o \l{QtTest}       \o Tool classes for unit testing
    \endtable

    QtCore contains tool classes like QString, QList, and QFile, as
    well as kernel classes like QObject and QTimer. The QApplication
    class has been refactored so that it can be used in non-GUI
    applications. It is split into QCoreApplication (in \l QtCore)
    and QApplication (in \l QtGui).

    This split makes it possible to develop server applications using Qt
    without linking in any unnecessary GUI-related code and without
    requiring GUI-related system libraries to be present on the target
    machine (e.g. Xlib on X11, Carbon on Mac OS X).

    If you use qmake to generate your makefiles, qmake will by default
    link your application against QtCore and QtGui. To remove the
    dependency upon QtGui, add the line

    \snippet doc/src/snippets/code/doc_src_qt4-intro.qdoc 0

    to your .pro file. To enable the other libraries, add the line

    \snippet doc/src/snippets/code/doc_src_qt4-intro.qdoc 1

    Another change to the build system is that moc now understands
    preprocessor directives. qmake automatically passes the defines set
    for your project (using "DEFINES +=") on to moc, which has its own
    built-in C++ preprocessor.

    To compile code that uses UI files, you will also need this line in
    the .pro file:

    \snippet doc/src/snippets/code/doc_src_qt4-intro.qdoc 2

    \section1 Include Syntax

    The syntax for including Qt class definitions has become

    \snippet doc/src/snippets/code/doc_src_qt4-intro.qdoc 3

    For example:

    \snippet doc/src/snippets/code/doc_src_qt4-intro.qdoc 4

    This is guaranteed to work for any public Qt class. The old syntax,

    \snippet doc/src/snippets/code/doc_src_qt4-intro.qdoc 5

    still works, but we encourage you to switch to the new syntax.

    If you attempt to include a header file from a library that isn't
    linked against the application, this will result in a
    compile-time warning (e.g., "QSqlQuery: No such file or
    directory"). You can remedy to this problem either by removing
    the offending include or by specifying the missing library in the
    QT entry of your \c .pro file (see \l{Build System} above).

    To include the definitions for all the classes in a library, simply
    specify the name of that library. For example:

    \snippet doc/src/snippets/code/doc_src_qt4-intro.qdoc 6

    \section1 Namespaces

    Qt 2 introduced a class called Qt for global-like constants
    (e.g., \c{Qt::yellow}). The C++ namespace construct was not used
    because not all compilers understood it when it was released.

    With Qt 4, the Qt class has become the Qt namespace. If you want
    to access a constant that is part of the Qt namespace, prefix it