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++ // Copyright (C) 2017 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
++ /*!
++ \page qtqml-cppclasses-topic.html
++ \title Important C++ Classes Provided By The Qt Qml Module
++ \brief Overview of the C++ classes provided by the Qt Qml module.
++
++ The \l{Qt Qml} module provides C++ classes which implement the QML framework.
++ Clients can use these classes to interact with the QML run-time (for example,
++ by injecting data or invoking methods on objects), and to instantiate a
++ hierarchy of objects from a QML document. The Qt Qml module provides more
++ C++ API than just the classes listed here, however the classes listed here
++ provide the foundations of the QML runtime and the core concepts of QML.
++
++ \section1 QML Runtime
++
++ A typical QML application with a C++ entry-point will instantiate a QQmlEngine
++ and then use a QQmlComponent to load a QML document. The engine provides a
++ default QQmlContext which will be the top-level evaluation context used for
++ evaluating functions and expressions defined in the QML document.
++ The object hierarchy defined in the QML document will be instantiated by
++ calling the \l{QQmlComponent::create()}{create()} function of the QQmlComponent
++ instance, assuming that no errors were encountered during document loading.
++
++ The client may wish to modify the QQmlContext provided by the engine, by
++ injecting properties or objects into the context. They can call the
++ \l{QQmlEngine::rootContext()} function to access the top-level context.
++
++ After instantiating the object, the client will usually pass control to the
++ application event loop so that user input events (like mouse-clicks) can be
++ delivered and handled by the application.
++
++ \note The Qt Quick module provides a convenience class, QQuickView, which
++ provides a QML runtime and visual window for displaying a QML application.
++
++ \section2 The QQmlEngine Class
++
++ The QQmlEngine class provides an engine which can manage a hierarchy of objects
++ which is defined in a QML document. It provides a root QML context within
++ which expressions are evaluated, and ensures that properties of objects are
++ updated correctly when required.
++
++ A QQmlEngine allows the configuration of global settings that apply to all of
++ the objects it manages; for example, the QNetworkAccessManager to be used for
++ network communications, and the file path to be used for persistent storage.
++
++ See the \l{QQmlEngine} class documentation for in-depth information about what
++ the QQmlEngine class provides, and how it can be used in an application.
++
++ \section2 The QQmlContext Class
++
++ The QQmlContext class provides a context for object instantiation and
++ expression evaluation. All objects are instantiated in a particular context,
++ and all of the expressions which are evaluated while an application is running
++ are evaluated within a particular context. This context defines how symbols
++ are resolved, and thus which values the expression operates on.
++
++ See the \l{QQmlContext} class documentation for in-depth information about
++ how to modify the evaluation context of an object by adding or removing
++ properties of a QQmlContext, and how to access the context for an object.
++
++ \section1 Dynamic Object Instantiation and Expression Evaluation
++
++ Dynamic object instantiation and dynamic expression evaluation are both core
++ concepts in QML. QML documents define object types which can be instantiated
++ at run-time using a QQmlComponent. An instance of the QQmlComponent class can
++ be created in C++ directly, or via the \l{QtQml::Qt::createComponent()}
++ {Qt.createComponent()} function in imperative QML code. Arbitrary expressions
++ can be calculated in C++ via the QQmlExpression class, and such expressions
++ can interact directly with the QML context.
++
++ \section2 The QQmlComponent Class
++
++ The QQmlComponent class can be used to load a QML document. It requires a
++ QQmlEngine in order to instantiate the hierarchy of objects defined in the QML
++ document.
++
++ See the \l{QQmlComponent} class documentation for in-depth information about
++ how to use QQmlComponent.
++
++ \section2 The QQmlExpression Class
++
++ The QQmlExpression class provides a way for clients to evaluate JavaScript
++ expressions from C++, using a particular QML evaluation context. This allows
++ clients to access QML objects by id, for example. The result of the evaluation
++ is returned as a QVariant, and the conversion rules are defined by the QML
++ engine.
++
++ See the \l{QQmlExpression} class documentation for in depth information about
++ how to use QQmlExpression in an application.
++
++ \section1 Usage of the Classes within QML Applications
++
++ These pages describe how to create QML applications which interact with the
++ C++ classes:
++
++ \list
++ \li \l{Overview - QML and C++ Integration}
++ \list
++ \li \l{qtqml-cppintegration-exposecppattributes.html}{Exposing Attributes of C++ Classes to QML}
++ \li \l{qtqml-cppintegration-definetypes.html}{Defining QML Types from C++}
++ \li \l{qtqml-cppintegration-contextproperties.html}{Embedding C++ Objects into QML with Context Properties}
++ \li \l{qtqml-cppintegration-interactqmlfromcpp.html}{Interacting with QML Objects from C++}
++ \li \l{qtqml-cppintegration-data.html}{Data Type Conversion Between QML and C++}
++ \endlist
++ \endlist
++
++ */