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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). |
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16 ** GNU Lesser General Public License Usage |
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24 ** In addition, as a special exception, Nokia gives you certain additional |
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36 ** |
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37 ** |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \page qtscriptextensions.html |
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44 \title Creating QtScript Extensions |
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45 \brief A guide to creating and using QtScript extensions. |
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46 |
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47 QtScript extensions can make additional functionality available to scripts |
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48 evaluated by a QScriptEngine. Extensions are imported by calling |
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49 the QScriptEngine::importExtension() function. |
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50 |
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51 There are three ways to create an extension: |
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52 |
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53 \list |
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54 \o Subclass QScriptExtensionPlugin and implement the desired functionality. |
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55 \o Implement the functionality in a script file. |
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56 \o Use a hybrid approach, where part of the functionality is implemented in a |
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57 QScriptExtensionPlugin, and part is implemented in a script file. |
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58 \endlist |
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59 |
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60 The (dot-qualified) extension name is used to determine the path (relative to |
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61 the application's plugin path) where QScriptEngine will look for the script |
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62 file that will initialize the extension; if a file called \c{__init__.js} |
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63 (usually located in \c{[application plugin path]/script/foo/}) is |
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64 found in the corresponding folder, its contents will be evaluated by the engine |
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65 when the extension is imported. |
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66 As an example, if the extension is called \c{"foo.bar.baz"}, the engine will look |
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67 for \c{__init__.js} in \c{foo/bar/baz}. Additionally, before importing |
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68 \c{"foo.bar.baz"}, the engine will ensure that the extensions \c{"foo"} and \c{"foo.bar"} |
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69 are imported, locating and evaluating the corresponding \c{__init__.js} |
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70 in the same manner (in folders \c{foo} and \c{foo/bar}, respectively). |
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71 |
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72 The contents of \c{__init__.js} are evaluated in a new QScriptContext, |
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73 as if it were the body of a function. The engine's Global Object acts as |
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74 the \c{this} object. The following local variables are initially available |
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75 to the script: |
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76 |
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77 \list |
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78 \o \bold{__extension__}: The name of the extension (e.g. \c{"foo.bar.baz"}). |
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79 \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().) |
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80 \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. |
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81 \endlist |
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82 |
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83 An example of a simple \c{__init__.js}: |
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84 |
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85 \snippet doc/src/snippets/code/doc_src_qtscriptextensions.qdoc 0 |
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86 |
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87 QScriptEngine will look for a QScriptExtensionPlugin that provides |
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88 the relevant extension by querying each plugin for its keys() |
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89 until a match is found. The plugin's initialize() function will be |
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90 called \bold{after} the relevant \c{__init__.js} (if any) has been |
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91 evaluated. |
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92 |
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93 Continuining with the example of our imaginary extension \c{"foo.bar.baz"}, |
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94 the following steps will be performed by QScriptEngine::importExtension(): |
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95 |
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96 \list |
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97 \o If it exists, \c{foo/__init__.js} is evaluated. |
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98 \o If a plugin with \c{"foo"} in its list of keys is found, its initialize() function is called with \c{"foo"} as key. |
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99 \o If it exists, \c{foo/bar/__init__.js} is evaluated. |
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100 \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. |
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101 \o If it exists, \c{foo/bar/baz/__init__.js} is evaluated. |
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102 \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. |
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103 \endlist |
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104 |
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105 \section1 Static Extensions |
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106 |
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107 When an extension is compiled and linked into your application as a |
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108 static plugin, Qt Script will look for the optional \c{__init__.js} |
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109 script in a resource, prefixed by \c{:/qtscriptextension}. For example, |
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110 if the extension key is "foo.bar", Qt Script will evaluate the contents |
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111 of the file \c{:/qtscriptextension/foo/bar/__init__.js}, if it |
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112 exists. Note that if the resource is built into the plugin, you may |
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113 need to use the Q_INIT_RESOURCE() macro to initialize the resource |
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114 before importing the extension. |
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115 */ |