/****************************************************************************
**
** Copyright (C) 2004-2008 Trolltech ASA. All rights reserved.
**
** This file is part of the documentation of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License versions 2.0 or 3.0 as published by the Free Software
** Foundation and appearing in the files LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file.  Alternatively you may (at
** your option) use any later version of the GNU General Public
** License if such license has been publicly approved by Trolltech ASA
** (or its successors, if any) and the KDE Free Qt Foundation.
**
** Please review the following information to ensure GNU General
** Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/. If
** you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** In addition, as a special exception, Trolltech, as the sole
** copyright holder for Qt Designer, grants users of the Qt/Eclipse
** Integration plug-in the right for the Qt/Eclipse Integration to
** link to functionality provided by Qt Designer and its related
** libraries.
**
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE. Trolltech reserves all rights not expressly
** granted herein.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

/*!
    \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 4.3:
    \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 Qtopia Core (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/Mac}{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 the current release, see
    the \l{http://www.trolltech.com/developer/notes/changes/changes-4.1.4/}
    {detailed list 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
    with \c Qt:: (e.g., \c{Qt::yellow}), or add the directive

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 7

    at the top of your source files, after your \c #include
    directives. If you use the \c{using namespace} syntax you don't
    need the prefix (e.g., \c yellow is sufficient).

    When porting Qt 3 applications, you may run into some source
    compatibility problems with some of these symbols. For example,
    in Qt 3, it was legal to write \c QWidget::yellow instead of \c
    Qt::yellow, because QWidget inherited from Qt. This won't work in
    Qt 4; you must write \c Qt::yellow or add the "using namespace"
    directive and drop the \c Qt:: prefix.

    The \l{qt3to4 - The Qt 3 to 4 Porting Tool}{qt3to4} porting tool
    automates this conversion.

    \section1 QObject/QWidget Constructors

    In Qt 4 we have tried to simplify the constructors of QObject/QWidget
    subclasses. This makes subclassing easier, at the same time as it
    helps make the Qt library more efficient.

    Constructors no longer take a "const char *name" parameter. If
    you want to specify a name for a QObject, you must call
    QObject::setObjectName() after construction. The object name is
    now a QString. The reasons for this change are:

    \list
    \o  Code that used it looked confusing, for example:

        \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 8

        \c label1 is a QLabel that displays the text "Hello"; \c
        label2 is a QLabel with no text, with the object name
        "Hello".

    \o  From surveys we did, most users didn't use the name, although
        they blindly followed Qt's convention and provided a "const
        char *name" in their subclasses's constructors. For example:

        \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 9

    \o  The name parameter was in Qt since version 1, and it always
        was documented as: "It is not very useful in the current
        version of Qt, but it will become increasingly important in
        the future." Ten years later, it still hasn't fulfilled its
        promise.
    \endlist

    QWidget's \c WFlags data type has been split in two:
    Qt::WindowFlags specifies low-level window flags (the type of
    window and the frame style), whereas Qt::WidgetAttribute
    specifies various higher-level attributes about the widget (e.g.,
    WA_StaticContents). Widget attributes can be set at any time
    using QWidget::setAttribute(); low-level window flags can be
    passed to the QWidget constructor or set later using
    QWidget::setParent(). As a consequence, the constructors of most
    QWidget subclasses don't need to provide a \c WFlags parameter.

    The \e parent parameter of all QObject classes in Qt defaults to
    a 0 pointer, as it used to do in Qt 1. This enables a style of
    programming where widgets are created without parents and then
    inserted in a layout, at which point the layout automatically
    reparents them.

    \section1 Dynamic Casts

    Qt 4 provides a qobject_cast<>() function that performs a dynamic cast
    based on the meta-information generated by moc for QObject
    subclasses. Unlike the standard C++ dynamic_cast<>() construct,
    qobject_cast<>() works even when RTTI is disabled, and it works correctly
    across DLL boundaries.

    Here's the Qt 3 idiom to cast a type to a subtype:

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 10

    The Qt 4 idiom is both cleaner and safer, because typos will always
    result in compiler errors:

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 11

    \section1 QPointer<T>

    The QPointer<T> class provides a pointer to type T (where T inherits
    from QObject) that is automatically set to 0 when the referenced
    object is destroyed. Guarded pointers are useful whenever you want to
    store a pointer to an object you do not own.

    Example:

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 12

    QPointer<T> is more or less the same as the old QGuardedPtr<T> class,
    except that it is now implemented in a much more lightweight manner
    than before. The cost of one QPointer<T> object is now approximately
    the same as that of a signal--slot connection.

    \section1 Paint Events

    Qt 4 supports double buffering transparently on all platforms. This
    feature can be turned off on a per-widget basis by calling
    QWidget::setAttribute(Qt::WA_PaintOnScreen).

    A consequence of this is that all painting must now be done from the
    paintEvent() function. This is also required by the HIView API on Mac
    OS X. In practice, this is seldom a problem, since you can call
    update() from anywhere in your code to create a paint event, with the
    region to update as the argument.

    To help porting, QWidget supports a Qt::WA_PaintOutsidePaintEvent
    attribute that can be set to make it possible to paint outside
    \l{QWidget::paintEvent()}{paintEvent()} on Windows and X11.

    \section1 Qt 3 Support Layer

    Qt 4 provides an extension library that applications based on Qt 3,
    called Qt3Support, that Qt applications can link against. This allows
    for more compatibility than ever before, without bloating Qt.

    \list
    \o  Classes that have been replaced by a different class with the
        same name, such as QListView, and classes that no longer exist in Qt 4
        are available with a \c 3 in their name (e.g., Q3ListView, Q3Accel).

    \o  Other classes provide compatibility functions. Most of these are
        implemented inline, so that they don't bloat the Qt libraries.
    \endlist

    To enable the Qt 3 support classes and functions, add the line

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 13

    to your \c .pro file.

    On Visual C++ 7 and GCC 3.2+, using compatibility functions often results
    in a compiler warning (e.g., "'find' is deprecated"). If you want to turn
    off that warning, add the line

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 14

    to your \c .pro file.

    If you want to use compatibility functions but don't want to link
    against the Qt3Support library, add the line

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 15

    or

    \snippet doc/src/snippets/code/doc.src.qt4-intro.qdoc 16

    to your \c .pro file, depending on whether you want compatibility
    function calls to generate compiler warnings or not.
*/

/*!
  \page qt4-4-intro.html
  \title What's New in Qt 4.4

  Qt 4.4 provides many improvements and enhancements over the previous releases
  in the Qt 4 series. This documents covers the most important features in this
  release, separated by category.

  A comprehensive list of changes between Qt 4.3 and Qt 4.4 is included
  in the \c changes-4.4.0 file
  \l{http://www.trolltech.com/developer/resources/notes/changes/changes-4.4.0}{available
  online}.
  \omit
  Changes between this release and the previous release are provided
  in the \c{changes-4.4.1} file (also
  \l{http://www.trolltech.com/developer/notes/changes/changes-4.4.1}{available online}).
  \endomit

  A list of other Qt 4 features can be found on the
  \bold{\l{What's New in Qt 4}} page.

  \bold{Highlights}

  \tableofcontents

  \section1 Qt WebKit Integration

  As Web-based technologies and services become more important to users, access
  to an integrated browser component has become a requirement for application
  developers.

  Qt 4.4 includes the QtWebKit module which provides a Qt-style API for the open
  source WebKit browser engine, making it possible for developers to use a fully-featured
  Web browser to display documents and access online services. The module also
  provides a level of integration beyond support for simple Web browsing tasks,
  enabling other application components to communicate with the browser via
  Qt's \l{signals and slots} inter-object communication mechanism.

  \image browser-demo.png

  A \l{Browser}{Web browser demo application} is provided as a proof of concept
  to show what can be achieved with Qt and WebKit.

  \section1 Multimedia API

  Long-awaited multimedia support for Qt applications has arrived in the form of
  the \l{Phonon Overview}{Phonon Multimedia Framework}, created in partnership
  with the KDE community. This allows developers to write cross-platform code
  for playing audio and video streams from files or over the network.

  A graph-based architecture provides an intuitive, extensible way to configure
  Phonon for playback. The use of native multimedia backends for each platform
  enables applications to support platform-specific media formats in addition to
  those commonly used on multiple platforms.

  \image mediaplayer-demo.png

  \l{Qt Examples#Phonon Multimedia Framework}{Examples and demonstrations}
  provided with Qt show how to use Phonon for your multimedia applications.

  \section1 XQuery and XPath Support

  The new QtXmlPatterns module provides facilities for XML processing beyond that
  supported by the QtXml module. Support for XQuery 1.0 and XPath 2.0 are provided
  in a way that integrates use of the query language and its data types with
  standard features in Qt, such as \l{QAbstractXmlNodeModel}{data models} and
  \l{signals and slots}.

  \section1 Widgets in Graphics View

  Many applications that use the interactive features provided by the \l{Graphics View}
  framework also use separate Qt widgets to control the way scenes are displayed to the
  user, often providing controls to allow zooming and rotation. Other specialized
  applications need to provide standard Qt widgets alongside graphics items within
  graphics scenes themselves.

  \image embeddeddialogs-demo.png

  Qt 4.4 provides a set of classes to allow standard Qt widgets to be added to
  graphics scenes, augmenting the collection of
  \l{Graphics View Classes}{Graphics View classes}. Widgets used in this way
  remain just as functional and responsive as normal widgets

  \section1 Concurrent Programming

  The QtConcurrent framework builds on Qt's threading features to make it easier to
  write certain kinds of multi-threaded application by integrating implementations
  of the well-known map-reduce and filter-reduce algorithms with Qt's container
  classes and object model.

  A synchonous (blocking) API is supplemented with an asynchronous (non-blocking)
  API which uses the concept of \l{QFuture}{futures} to handle synchronization
  between a main thread and several worker threads, simplifying the delivery of
  results.

  \section1 Improved Help System

  Qt Assistant has been redesigned to use a self-contained help format for documentation
  packages that makes it easier to maintain collections of documents. The indexing
  facilities provided by Qt Assistant have been improved to allow multiple co-existing
  collections of documents to be searched, and results from advanced searches are
  presented in a familiar webpage-style result page.

  With the arrival of the new help formats, the way Qt applications provide online
  help has also been updated. Qt Assistant has been improved to support automation
  as a child process of any Qt application, allowing applications to request specific
  items of documentation, perform searches, and even customize the user interface of
  Qt Assistant itself.

  \section1 Printing System Improvements

  Improvements to printing in Qt 4.4 include support for custom page sizes and
  custom margins, as well as the ability to programatically enumerate printers via
  the new QPrinterInfo class.

  \image qprintpreviewdialog.png

  A couple of new classes, QPrintPreviewWidget and QPrintPreviewDialog, have been
  added to make it easy to add a print preview to an application. The QPrintDialog
  and QPageSetupDialog classes for X11 have been redesigned to be easier to use.

  \section1 Qt for Windows CE

  Qt 4.4 is the first release to include provision for Windows CE as
  a supported platform. Qt for Windows CE contains all functions
  necessary to develop end-to-end applications, as well as integrated
  developer tools, such as powerful graphical user interface (GUI) and
  forms builder and robust features for translation of applications
  into new languages.

  \image qt-for-wince-landscape.png

  \section1 Qt for Embedded Linux

  Qt 4.4 contains a number of improvements specifically for the Embedded Linux platform,
  many of which are related to performance and extending the range of supported display
  hardware. These include a screen driver DirectFB and a driver that uses the ATI Handheld
  Interface library.

  \image embedded-demo-launcher.png

  In addition, a new selection of demonstrations and examples has been included to
  showcase the graphical features of Qt for Embedded Linux.
*/
