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/****************************************************************************
**
** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** GNU Free Documentation License
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms
** and conditions contained in a signed written agreement between you
** and Nokia.
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\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.js 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.
*/
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