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/*!
\page qtqml-typereference-topic.html
\title QML Types Provided By The Qt QML Module
\brief List of QML types provided by the Qt QML module

The Qt QML module provides the definition and implementation of the QML
language, and it also provides some elementary QML types which provide the
basis for further extensions to the QML language.



The Qt QML module also provides the \c QtObject and \c Component types which
may be used in QML documents, by default.  These types are non-visual and
provide building-blocks for extensions to QML.



\section1 The QtQml Import

The types provided by the Qt QML module are only available in a QML document
if that document imports the QtQml namespace (or if the document imports the
QtQuick namespace, as noted below).

The current version of the import provided by the Qt QML module is version 2.0,
and thus it may be imported via the following statement:

\tt{import QtQml 2.0}

Most clients will never need to use the QtQml import, as all of the types and
functionality provided by the QtQml namespace are also provided by the QtQuick
namespace which may be imported as follows:

\tt{import QtQuick 2.0}

See the \l{Qt Quick} module documentation for more information about the
QtQuick namespace and what it provides to QML application developers.

The documentation for the types below applies equally to the types of the same
name provided by the Qt Quick module, as they are in fact identical.

\section1 QtObject

The \c QtObject type provides a basic instantiable object which can be used in
QML applications.  It is non-visual, but may have properties, methods, signals
and signal handlers.

For example, the following QtObject has several properties, one of which has
been assigned a \l{Property Binding}
{binding}, and a \l{Signal and Handler Event System}{signal handler} for
the default change signal which exists for one of its properties:

\code
    import QtQuick 2.0

    QtObject {
        property int a: 15
        property int b: a + 22
        property int changeCount: 0

        onAChanged: {
            changeCount += 1;
        }
    }
\endcode

\section1 Component

The \c Component type provides a basic re-usable component which allows
instances of another type to be instantiated on-demand.  It may be given an
\c id and it has a default property which is the object type to instantiate,
but no other properties may be added to it.

For example, the following QtObject has two different Component properties,
and it uses those components to dynamically construct objects at run-time:

\code
    import QtQuick 2.0

    QtObject {
        id: root
        property bool which: true

        property Component a: Component {
            id: firstComponent
            QtObject {
                property int answer: 42
                function activate() {
                    console.log("The answer is: " + answer);
                }
            }
        }

        property Component b: Component {
            id: secondComponent
            QtObject {
                property string message: "Hello, World!"
                function activate() {
                    console.log(message);
                }
            }
        }

        function activateDynamicObject() {
            var o = {};
            if (which) {
                which = false;
                o = a.createObject(null); // no parent
            } else {
                which = true;
                o = b.createObject(null); // no parent
            }
            o.activate();
        }
    }
\endcode

*/