1
/****************************************************************************
3
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
4
** Contact: Nokia Corporation (qt-info@nokia.com)
6
** This file is part of the documentation of the Qt Toolkit.
8
** $QT_BEGIN_LICENSE:LGPL$
10
** Licensees holding valid Qt Commercial licenses may use this file in
11
** accordance with the Qt Commercial License Agreement provided with the
12
** Software or, alternatively, in accordance with the terms contained in
13
** a written agreement between you and Nokia.
15
** GNU Lesser General Public License Usage
16
** Alternatively, this file may be used under the terms of the GNU Lesser
17
** General Public License version 2.1 as published by the Free Software
18
** Foundation and appearing in the file LICENSE.LGPL included in the
19
** packaging of this file. Please review the following information to
20
** ensure the GNU Lesser General Public License version 2.1 requirements
21
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
23
** In addition, as a special exception, Nokia gives you certain
24
** additional rights. These rights are described in the Nokia Qt LGPL
25
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
28
** GNU General Public License Usage
29
** Alternatively, this file may be used under the terms of the GNU
30
** General Public License version 3.0 as published by the Free Software
31
** Foundation and appearing in the file LICENSE.GPL included in the
32
** packaging of this file. Please review the following information to
33
** ensure the GNU General Public License version 3.0 requirements will be
34
** met: http://www.gnu.org/copyleft/gpl.html.
36
** If you are unsure which license is appropriate for your use, please
37
** contact the sales department at http://www.qtsoftware.com/contact.
40
****************************************************************************/
42
/****************************************************************************
44
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
45
** Contact: Nokia Corporation (qt-info@nokia.com)
47
** This file is part of the Qt GUI Toolkit.
48
** EDITIONS: FREE, PROFESSIONAL, ENTERPRISE
50
****************************************************************************/
53
\page qtscriptextensions.html
54
\title Creating QtScript Extensions
56
\brief A guide to creating and using QtScript extensions.
58
QtScript extensions can make additional functionality available to scripts
59
evaluated by a QScriptEngine. Extensions are imported by calling
60
the QScriptEngine::importExtension() function.
62
There are three ways to create an extension:
65
\o Subclass QScriptExtensionPlugin and implement the desired functionality.
66
\o Implement the functionality in a script file.
67
\o Use a hybrid approach, where part of the functionality is implemented in a
68
QScriptExtensionPlugin, and part is implemented in a script file.
71
The (dot-qualified) extension name is used to determine the path (relative to
72
the application's plugin path) where QScriptEngine will look for the script
73
file that will initialize the extension; if a file called \c{__init__.js}
74
(usually located in \c{[application plugin path]/script/foo/}) is
75
found in the corresponding folder, its contents will be evaluated by the engine
76
when the extension is imported.
77
As an example, if the extension is called \c{"foo.bar.baz"}, the engine will look
78
for \c{__init__.js} in \c{foo/bar/baz}. Additionally, before importing
79
\c{"foo.bar.baz"}, the engine will ensure that the extensions \c{"foo"} and \c{"foo.bar"}
80
are imported, locating and evaluating the corresponding \c{__init__.js}
81
in the same manner (in folders \c{foo} and \c{foo/bar}, respectively).
83
The contents of \c{__init__.js} are evaluated in a new QScriptContext,
84
as if it were the body of a function. The engine's Global Object acts as
85
the \c{this} object. The following local variables are initially available
89
\o \bold{__extension__}: The name of the extension (e.g. \c{"foo.bar.baz"}).
90
\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().)
91
\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.
94
An example of a simple \c{__init__.js}:
96
\snippet doc/src/snippets/code/doc_src_qtscriptextensions.qdoc 0
98
QScriptEngine will look for a QScriptExtensionPlugin that provides
99
the relevant extension by querying each plugin for its keys()
100
until a match is found. The plugin's initialize() function will be
101
called \bold{after} the relevant \c{__init__.js} (if any) has been
104
Continuining with the example of our imaginary extension \c{"foo.bar.baz"},
105
the following steps will be performed by QScriptEngine::importExtension():
108
\o If it exists, \c{foo/__init__.js} is evaluated.
109
\o If a plugin with \c{"foo"} in its list of keys is found, its initialize() function is called with \c{"foo"} as key.
110
\o If it exists, \c{foo/bar/__init__.js} is evaluated.
111
\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.
112
\o If it exists, \c{foo/bar/baz/__init__.js} is evaluated.
113
\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.
116
\section1 Static Extensions
118
When an extension is compiled and linked into your application as a
119
static plugin, Qt Script will look for the optional \c{__init__.js}
120
script in a resource, prefixed by \c{:/qtscriptextension}. For example,
121
if the extension key is "foo.bar", Qt Script will evaluate the contents
122
of the file \c{:/qtscriptextension/foo/bar/__init__.js}, if it
123
exists. Note that if the resource is built into the plugin, you may
124
need to use the Q_INIT_RESOURCE() macro to initialize the resource
125
before importing the extension.