/**************************************************************************** ** ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). ** All rights reserved. ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:LGPL$ ** No Commercial Usage ** This file contains pre-release code and may not be distributed. ** You may use this file in accordance with the terms and conditions ** contained in the Technology Preview License Agreement accompanying ** this package. ** ** GNU Lesser General Public License Usage ** Alternatively, this file may be used under the terms of the GNU Lesser ** General Public License version 2.1 as published by the Free Software ** Foundation and appearing in the file LICENSE.LGPL included in the ** packaging of this file. Please review the following information to ** ensure the GNU Lesser General Public License version 2.1 requirements ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. ** ** In addition, as a special exception, Nokia gives you certain additional ** rights. These rights are described in the Nokia Qt LGPL Exception ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. ** ** If you have questions regarding the use of this file, please contact ** Nokia at qt-info@nokia.com. ** ** ** ** ** ** ** ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \page qtscriptextensions.html \title Creating QtScript Extensions \brief A guide to creating and using QtScript extensions. QtScript extensions can make additional functionality available to scripts evaluated by a QScriptEngine. Extensions are imported by calling the QScriptEngine::importExtension() function. There are three ways to create an extension: \list \o Subclass QScriptExtensionPlugin and implement the desired functionality. \o Implement the functionality in a script file. \o Use a hybrid approach, where part of the functionality is implemented in a QScriptExtensionPlugin, and part is implemented in a script file. \endlist The (dot-qualified) extension name is used to determine the path (relative to the application's plugin path) where QScriptEngine will look for the script file that will initialize the extension; if a file called \c{__init__.js} (usually located in \c{[application plugin path]/script/foo/}) is found in the corresponding folder, its contents will be evaluated by the engine when the extension is imported. As an example, if the extension is called \c{"foo.bar.baz"}, the engine will look for \c{__init__.js} in \c{foo/bar/baz}. Additionally, before importing \c{"foo.bar.baz"}, the engine will ensure that the extensions \c{"foo"} and \c{"foo.bar"} are imported, locating and evaluating the corresponding \c{__init__.js} in the same manner (in folders \c{foo} and \c{foo/bar}, respectively). The contents of \c{__init__.js} are evaluated in a new QScriptContext, as if it were the body of a function. The engine's Global Object acts as the \c{this} object. The following local variables are initially available to the script: \list \o \bold{__extension__}: The name of the extension (e.g. \c{"foo.bar.baz"}). \o \bold{__setupPackage__}: A convenience function for setting up a "namespace" in the script environment. A typical application is to call \c{__setupPackage__()} with \c{__extension__} as argument; e.g. \c{__setupPackage__("foo.bar.baz")} would ensure that the object chain represented by the expression \c{foo.bar.baz} exists in the script environment. (This function is semantically equivalent to QScriptExtensionPlugin::setupPackage().) \o \bold{__postInit__}: By default, this variable is undefined. If you assign a function to it, that function will be called \bold{after} the C++ plugin's initialize() function has been called. You can use this to perform further initialization that depends on e.g. native functions that the C++ plugin registers. \endlist An example of a simple \c{__init__.js}: \snippet doc/src/snippets/code/doc_src_qtscriptextensions.qdoc 0 QScriptEngine will look for a QScriptExtensionPlugin that provides the relevant extension by querying each plugin for its keys() until a match is found. The plugin's initialize() function will be called \bold{after} the relevant \c{__init__.js} (if any) has been evaluated. Continuining with the example of our imaginary extension \c{"foo.bar.baz"}, the following steps will be performed by QScriptEngine::importExtension(): \list \o If it exists, \c{foo/__init__.js} is evaluated. \o If a plugin with \c{"foo"} in its list of keys is found, its initialize() function is called with \c{"foo"} as key. \o If it exists, \c{foo/bar/__init__.js} is evaluated. \o If a plugin with \c{"foo.bar"} in its list of keys is found, its initialize() function is called with \c{"foo.bar"} as key. \o If it exists, \c{foo/bar/baz/__init__.js} is evaluated. \o If a plugin with "foo.bar.baz" in its list of keys is found, its initialize() function is called with \c{"foo.bar.baz"} as key. \endlist \section1 Static Extensions When an extension is compiled and linked into your application as a static plugin, Qt Script will look for the optional \c{__init__.js} script in a resource, prefixed by \c{:/qtscriptextension}. For example, if the extension key is "foo.bar", Qt Script will evaluate the contents of the file \c{:/qtscriptextension/foo/bar/__init__.js}, if it exists. Note that if the resource is built into the plugin, you may need to use the Q_INIT_RESOURCE() macro to initialize the resource before importing the extension. */