/****************************************************************************
**
** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
**
** This file is part of the Qt GUI Toolkit.
** EDITIONS: FREE, PROFESSIONAL, ENTERPRISE
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

/*!
    \title Grouped Classes
    \group groups
    \ingroup classlists

    This page provides a way of navigating Qt's classes by grouping
    related classes together. Some classes may appear in more than one group.

    \generatelist{related}

    \omit
    \row
    \o \l{Component Model}
    \o Interfaces and helper classes for the Qt Component Model.
    \endomit

*/

/*!
    \group advanced
    \ingroup groups

    \title Advanced Widgets
    \brief Advanced GUI widgets such as tab widgets and progress bars.

    These classes provide more complex user interface widgets (controls).

*/

/*!
    \group abstractwidgets
    \ingroup groups

    \title Abstract Widget Classes
    \brief Abstract widget classes usable through subclassing.

    These classes are abstract widgets; they are generally not usable in
    themselves, but provide functionality that can be used by inheriting
    these classes.

*/

/*!
    \group accessibility
    \ingroup groups
    \ingroup topics

    \title Accessibility Classes
    \brief Classes that provide support for accessibility.

    Accessible applications are able to be used by users who cannot use
    conventional means of interaction. These classes provide support for
    accessible applications.

*/

/*!
    \group appearance
    \ingroup groups

    \title Widget Appearance and Style
    \brief Appearance customization with styles, fonts, colors etc.

    These classes are used to customize an application's appearance and
    style.

*/

/*!
    \group application
    \ingroup groups

    \title Main Window and Related Classes
    \brief Everything you need for a typical modern main application window,
    including menus, toolbars, workspace, etc.

    These classes provide everything you need for a typical modern main
    application window, like the main window itself, menu and tool bars,
    a status bar, etc.

*/


/*!
    \group basicwidgets
    \ingroup groups

    \title Basic Widgets
    \brief Basic GUI widgets such as buttons, comboboxes and scroll bars.

    These basic widgets (controls) are designed for direct use.
    There are also some \l{Abstract Widget Classes} that are designed for
    subclassing, and some more complex \l{Advanced Widgets}.

*/

/* \group componentmodel

    \title Component Model

    These classes and interfaces form the basis of the \l{Qt Component Model}.

*/

/*!
    \group database
    \ingroup groups

    \title Database Classes
    \brief Database related classes, e.g. for SQL databases.

    These classes provide access to SQL databases.
*/


/*!
    \group dialogs
    \ingroup groups

    \title Standard Dialog Classes
    \brief Ready-made dialogs for file, font, color selection and more.

    These classes are complex widgets, composed of simpler widgets; dialog
    boxes, generally.
*/

/*!
    \group desktop
    \ingroup groups

    \title Desktop Environment Classes
    \brief Classes for interacting with the user's desktop environment.

    These classes provide ways to interact with the user's desktop environment and
    take advantage of common services.
*/

/*!
    \group draganddrop
    \ingroup groups

    \title Drag And Drop Classes
    \brief Classes dealing with drag and drop and mime type encoding and decoding.

    These classes deal with drag and drop and the necessary mime type
    encoding and decoding. See also \link dnd.html Drag and Drop with
    Qt. \endlink
*/

/*!
    \group environment
    \ingroup groups

    \title Environment Classes
    \brief Classes providing various global services such as event handling,
    access to system settings and internationalization.

    These classes providing various global services to your application such as
    event handling, access to system settings, internationalization, etc.

*/

/*!
    \group events
    \ingroup groups

    \title Event Classes
    \brief Classes used to create and handle events.

    These classes are used to create and handle events.

    For more information see the \link object.html Object model\endlink
    and \link signalsandslots.html Signals and Slots\endlink.
*/


/*!
    \group geomanagement
    \ingroup groups

    \title Layout Management
    \brief Classes handling automatic resizing and moving of widgets, for
    composing complex dialogs.

    These classes provide automatic geometry (layout) management of widgets.

*/


/*!
    \group helpsystem
    \ingroup groups

    \title Help System
    \brief Classes used to provide online-help for applications.

    \keyword help system

    These classes provide for all forms of online-help in your application,
    with three levels of detail:

    \list 1
        \o Tool Tips and Status Bar message - flyweight help, extremely brief,
            entirely integrated in the user interface, requiring little
            or no user interaction to invoke.
        \o What's This? - lightweight, but can be
            a three-paragraph explanation.
        \o Online Help - can encompass any amount of information,
            but is typically slower to call up, somewhat separated
            from the user's work, and often users feel that using online
            help is a digression from their real task.
    \endlist

*/


/*!
    \group io
    \ingroup groups

    \title Input/Output and Networking
    \brief Classes providing file input and output along with directory and
    network handling.

    These classes are used to handle input and output to and from external
    devices, processes, files etc. as well as manipulating files and directories.
*/

/*!
    \group misc
    \ingroup groups

    \title Miscellaneous Classes
    \brief Various other useful classes.

    These classes are useful classes not fitting into any other category.

*/


/*!
    \group model-view
    \ingroup groups

    \title Model/View Classes
    \brief Classes that use the model/view design pattern.

    These classes use the model/view design pattern in which the
    underlying data (in the model) is kept separate from the way the data
    is presented and manipulated by the user (in the view). See also
    \link model-view-programming.html Model/View Programming\endlink.

*/

/*!
    \group multimedia
    \ingroup groups

    \title Multimedia, Graphics and Printing
    \brief Classes that provide support for graphics (2D, and with OpenGL, 3D),
    image encoding, decoding, and manipulation, sound, animation,
    printing, etc.

    These classes provide support for graphics (2D, and with OpenGL, 3D),
    image encoding, decoding, and manipulation, sound, animation, printing
    etc.

    See also this introduction to the \link coordsys.html Qt
    coordinate system. \endlink

*/

/*!
    \group objectmodel
    \ingroup groups

    \title Object Model
    \brief The Qt GUI toolkit's underlying object model.

    These classes form the basis of the \l{Qt Object Model}.

*/

/*!
    \group organizers
    \ingroup groups

    \title Organizers
    \brief User interface organizers such as splitters, tab bars, button groups, etc.

    These classes are used to organize and group GUI primitives into more
    complex applications or dialogs.

*/


/*!
    \group plugins
    \ingroup groups

    \title Plugin Classes
    \brief Plugin related classes.

    These classes deal with shared libraries, (e.g. .so and DLL files),
    and with Qt plugins.

    See the \link plugins-howto.html plugins documentation\endlink.

    See also the \l{ActiveQt framework} for Windows.

*/

/*!
    \group qws
    \ingroup groups

    \title Qtopia Core Classes
    \ingroup qtopiacore
    \brief Classes that are specific to Qtopia Core (Qt for embedded Linux).

    These classes are relevant to \l{Qtopia Core} users.
*/

/*!
    \group shared
    \ingroup architecture
    \ingroup groups

    \title Implicitly Shared Classes
    \brief Classes that use reference counting for fast copying.

    \keyword implicit data sharing
    \keyword implicit sharing
    \keyword implicitly shared
    \keyword reference counting
    \keyword shared implicitly
    \keyword shared classes

    Many C++ classes in Qt use implicit data sharing to maximize
    resource usage and minimize copying of data. The only important
    effect is that the classes listed here \e can be passed around as
    arguments efficiently, even though they may seem heavyweight.

    \tableofcontents

    \section1 Overview

    A shared class consists of a pointer to a shared data block that
    contains a reference count and the data.

    When a shared object is created, it sets the reference count to 1. The
    reference count is incremented whenever a new object references the
    shared data, and decremented when the object dereferences the shared
    data. The shared data is deleted when the reference count becomes
    zero.

    \keyword deep copy
    \keyword shallow copy

    When dealing with shared objects, there are two ways of copying an
    object. We usually speak about \e deep and \e shallow copies. A deep
    copy implies duplicating an object. A shallow copy is a reference
    copy, i.e. just a pointer to a shared data block. Making a deep copy
    can be expensive in terms of memory and CPU. Making a shallow copy is
    very fast, because it only involves setting a pointer and incrementing
    the reference count.

    Object assignment (with operator=()) for implicitly shared objects is
    implemented using shallow copies.

    The benefit of sharing is that a program does not need to duplicate
    data unnecessarily, which results in lower memory use and less copying
    of data. Objects can easily be assigned, sent as function arguments,
    and returned from functions.

    Implicit sharing takes place behind the scenes; the programmer
    does not need to worry about it. Even in multithreaded
    applications, implicit sharing takes place, as explained in
    \l{Threads and Implicit Sharing}.

    \section1 Implicit Sharing in Detail

    Implicit sharing automatically detaches the object from a shared block
    if the object is about to change and the reference count is greater
    than one. (This is often called "copy-on-write" or "value semantics".)

    An implicitly shared class has total control of its internal data. In
    any member functions that modify its data, it automatically detaches
    before modifying the data.

    The QPen class, which uses implicit sharing, detaches from the shared
    data in all member functions that change the internal data.

    Code fragment:
    \code
        void QPen::setStyle(Qt::PenStyle style)
        {
            detach();           // detach from common data
            d->style = style;   // set the style member
        }

        void QPen::detach()
        {
            if (d->ref != 1) {
                ...             // perform a deep copy
            }
        }
    \endcode

    \section1 List of Classes

    The classes listed below automatically detach from common data if
    an object is about to be changed. The programmer will not even
    notice that the objects are shared. Thus you should treat
    separate instances of them as separate objects. They will always
    behave as separate objects but with the added benefit of sharing
    data whenever possible. For this reason, you can pass instances
    of these classes as arguments to functions by value without
    concern for the copying overhead.

    Example:
    \code
        QPixmap p1, p2;
        p1.load("image.bmp");
        p2 = p1;                        // p1 and p2 share data

        QPainter paint;
        paint.begin(&p2);               // cuts p2 loose from p1
        paint.drawText(0,50, "Hi");
        paint.end();
    \endcode

    In this example, \c p1 and \c p2 share data until QPainter::begin()
    is called for \c p2, because painting a pixmap will modify it.

    \warning Do not copy an implicitly shared container (QMap,
    QVector, etc.) while you are iterating over it using an non-const
    \l{STL-style iterator}.
*/

/*!
    \group text
    \ingroup groups
    \ingroup text-processing

    \title Text Processing Classes
    \brief Classes for text processing. (See also \l{XML Classes}.)

    These classes are relevant to text processing. See also the
    \l{Rich Text Processing} overview and the
    \l{XML classes}.
*/

/*!
    \group thread
    \ingroup groups

    \title Threading Classes
    \brief Classes that provide threading support.

    These classes are relevant to threaded applications. See
    \l{Thread Support in Qt} for an overview of the features
    Qt provides to help with multithreaded programming.
*/


/*!
    \group time
    \ingroup groups

    \title Date and Time Classes
    \brief Classes for handling date and time.

    These classes provide system-independent date and time abstractions.

*/

/*!
    \group tools
    \ingroup groups

    \title Non-GUI Classes
    \brief Collection classes such as list, queue, stack and string, along
    with other classes that can be used without needing QApplication.

    The non-GUI classes are general-purpose collection and string classes
    that may be used independently of the GUI classes.

    In particular, these classes do not depend on QApplication at all,
    and so can be used in non-GUI programs.

*/

/*!
    \group xml-tools
    \ingroup groups

    \title XML Classes
    \brief Classes that support XML, via, for example DOM and SAX.

    These classes are relevant to XML users.
*/

/*!
    \group script
    \ingroup groups
    \ingroup scripting

    \title Scripting Classes
    \brief Qt Script-related classes and overviews.

    These classes are relevant to Qt Script users.
*/
