Difference between revisions of "User:Dipesh/Kross-Tutorial"

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* [[Development/Tutorials/KSpread Scripting|KSpread Scripting]]
 
* [[Development/Tutorials/KSpread Scripting|KSpread Scripting]]
 
* [[Development/Tutorials/Krita Scripting|Krita Scripting]]
 
* [[Development/Tutorials/Krita Scripting|Krita Scripting]]
 
<!-- ################################################################################ //-->
 
 
==Kross==
 
 
The [http://kross.dipe.org Kross] scripting framework provides full
 
[http://www.python.org/ Python], [http://www.ruby-lang.org/ Ruby] and
 
[http://xmelegance.org/kjsembed KDE JavaScript] scripting support. The goal was
 
to limit the work needed on applications to have them fully scriptable and to provide a modular
 
way to transparently integrate additional interpreters and in that way extend your application
 
with a new scripting-backend without any new line of code and even without any recompile. To
 
achieve this internally Qt's introspection-functionality like signals, slots, properties,
 
enums, QVariant, QObject, QMetaObject, QMetaType, etc. are used to deal with functionality
 
at runtime.
 
 
===The Interpreter plugins===
 
 
Kross offers a plugin-interface to integrate interpreter backends like Python, Ruby and
 
KDE-Javascript. They are loaded on demand at runtime. Neither the application nor Kross
 
needs to know any details about the backends. This clear separation between the application
 
and scripting details enables at the one hand, to deal with scripting at an abstract level without
 
being bound to only one backend, and at the other hand makes it easy to integrate scripting
 
into an already existing application.
 
 
Currently Kross comes with support for 3 scripting backends;
 
<ul>
 
  <li>The [http://websvn.kde.org/trunk/koffice/libs/kross/python/ Python plugin]
 
    implements access to the Python
 
    ([http://www.python.org/ home]
 
    [http://www.python.org/doc/ docs]) language.</li>
 
  <li>The [http://websvn.kde.org/trunk/koffice/libs/kross/ruby/ Ruby plugin]
 
    implements access to the Ruby
 
    ([http://www.ruby-lang.org/ home]
 
    [http://www.ruby-lang.org/en/documentation/ docs]) language.</li>
 
  <li>The [http://websvn.kde.org/trunk/KDE/kdelibs/kross/kjs KDE JavaScript plugin]
 
    uses the in kdelibs4 included Kjs
 
    ([http://websvn.kde.org/trunk/KDE/kdelibs/kjs/README?view=markup readme]
 
    [http://websvn.kde.org/trunk/KDE/kdelibs/kjs/ svn]) and KjsEmbed4
 
    ([http://xmelegance.org/kjsembed home]
 
    [https://mail.kde.org/mailman/listinfo/kjsembed mailinglist]
 
    [http://websvn.kde.org/trunk/KDE/kdelibs/kjsembed/ svn])
 
  frameworks to provide access to the JavaScript language.</li>
 
</ul>
 
Each interpreter plugin needs to implement two abstract classes;
 
<ul>
 
  <li>The [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/interpreter.h?view=markup Kross::Interpreter]
 
    class is a singleton controlled by the
 
    [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/manager.h?view=markup Kross::Manager]
 
    and could be used to setup the interpreter or do other things to share functionality between
 
    instances of the Script class.</li>
 
  <li>The [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/script.h?view=markup Kross::Script]
 
    class handles exactly one script instance. An application is able to deal with multiple
 
    scripts at the same time where each of them has it's own instance of the Kross::Script
 
    class controlled by an instance of the more abstract
 
    [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/action.h?view=markup Kross::Action] class.</li>
 
</ul>
 
 
===The Module plugins===
 
 
Modules are plugins loaded on demand at runtime to provide additional functionality. They are
 
somewhat wrappers/bindings/adaptors to offer access to functionality your application or
 
a library of your application likes to expose to scripting backends. '''TODO: this parag doesn't parse for me'''
 
 
Since Qt's introspection functionality is used, we are able to throw in just QObject's
 
and have them act as classes/objects within a scripting backend. Slots are membermethods
 
while properties and enumerations are membervariables. If your application also likes
 
to offer [http://hal.freedesktop.org/wiki/Software/dbus DBus] support it may be
 
an idea to reuse the
 
[http://doc.trolltech.com/4.2/qdbusabstractadaptor.html QDBusAbstractAdaptor]
 
implementations your application has also for scripting, like for example
 
[http://wiki.koffice.org/index.php?title=KSpread/Scripting KSpread] did.
 
 
Let's take a look at the following code that implements such a module;
 
<pre>
 
class MyObject : public QObject {
 
  Q_OBJECT
 
  Q_PROPERTY(QString name READ name WRITE setName)
 
  public:
 
    MyObject(QObject* parent = 0) : QObject(parent) {}
 
    virtual ~MyObject() {}
 
    QString name() const { return objectName(); }
 
    void setName(const QString& name) {
 
      return setObjectName(name);
 
    }
 
  public slots:
 
    QObject* create(const QString& name,
 
                    QObject* parent=0) {
 
      MyObject* obj = new MyObject(parent);
 
      obj->setObjectName(name);
 
      return obj;
 
    }
 
    QObject* parent() const { return QObject::parent(); }
 
    void setParent(QObject* parent) {
 
      QObject::setParent(parent);
 
      emit parentChanged();
 
    }
 
  signals:
 
    void parentChanged();
 
};
 
extern "C" {
 
  QObject* krossmodule() {
 
    return new MyObject();
 
  }
 
}
 
</pre>
 
Then we just need to have our myobject.h and myobject.cpp files, filled with the content
 
above, defined in the CMakeLists.txt file. The library needs to be named "krossmodule..." where
 
the "..." is then the name the module is accessible as. For our example we use
 
"krossmodulemyobjectmod" and therefore we are able to access the module if installed
 
as "myobjectmod". The example does not depend on Kross, so you may like to replace
 
${KROSS_INCLUDES} with whatever else your module depends on.
 
<pre>
 
include_directories(${CMAKE_SOURCE_DIR}
 
  ${KROSS_INCLUDES})
 
set(krossmodulemyobjectmod_PART_SRCS
 
  myobject.cpp)
 
kde4_automoc(${krossmodulemyobjectmod_PART_SRCS})
 
kde4_add_plugin(krossmodulemyobjectmod
 
  ${krossmodulemyobjectmod_PART_SRCS})
 
target_link_libraries(krossmodulemyobjectmod
 
  ${KDE4_KDECORE_LIBS} ${KDE4_KROSSCORE_LIBS})
 
install(TARGETS krossmodulemyobjectmod
 
  DESTINATION ${PLUGIN_INSTALL_DIR})
 
</pre>
 
The following Python sample code accesses then the module at runtime and uses the QObject,
 
calls it's slots and properties and connects a signal with a python function (e.g. save as
 
file named "myobjecttest.py" and execute with "kross ./myobjecttest.py");
 
<pre>
 
#!/usr/bin/env kross
 
import Kross
 
m = Kross.module("myobjectmod")
 
m.name = "MyObjectModuleName"
 
obj1 = m.create("OtherObjectName")
 
def myCallbackFunc(args):
 
    print "The parent of obj1 changed"
 
obj1.connect("parentChanged()",myCallbackFunc)
 
obj1.setParent(m)
 
print "%s %s" % (obj1.name,obj1.parent().name)
 
</pre>
 
 
===Manager, GuiClient, Action===
 
 
The [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/manager.h?view=markup Kross::Manager]
 
class is a singleton that provides access to the interpreters, to actions and to the modules.
 
The Kross::Manager is available within scripting code as module named "Kross". Following Python
 
script uses the Kross module to create a new Kross::Action instance, fills it with JavaScript
 
code and executes that JavaScript code.
 
<pre>
 
#!/usr/bin/env kross
 
import Kross
 
a = Kross.action("MyKjsScript")
 
a.setInterpreter("javascript")
 
a.setCode("println(\"Hello world from Kjs\");")
 
a.trigger()
 
</pre>
 
 
The [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/guiclient.h?view=markup Kross::GuiClient]
 
class implements KXMLGUIClient to provide GUI functionality, handling of XML configuration files
 
on a more abstract level and offers some predefined actions that could be optionally used in
 
your application.
 
 
The [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/action.h?view=markup Kross::Action]
 
class offers an abstract container to deal with scripts like a single standalone scriptfile.
 
Each action holds a reference to the by the matching
 
[http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/interpreter.h?view=markup Kross::Interpreter]
 
instance created by [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/script.h?view=markup Kross::Script]
 
instance. Following Python script accesses the Kross module and the self variable which is
 
our Kross::Action instance that provides the context for the running Python script.
 
<pre>
 
#!/usr/bin/env kross
 
import Kross
 
print "objectName=%s" % Kross.objectName()
 
print "interpreters=%s" % Kross.interpreters()
 
print "objectName=%s" % self.objectName()
 
print "text=%s" % self.text
 
print "enabled=%s" % self.enabled
 
print "currentPath=%s" % self.currentPath()
 
print "interpreter=%s" % self.interpreter()
 
print "description=%s" % self.description()
 
print "code=%s" % self.code()
 
</pre>
 
 
===DBus and Kross===
 
 
With the [http://doc.trolltech.com/4.2/qtdbus.html QtDBus module] Qt provides a library that a Qt/KDE application is able to use to make Inter-Process Communication using the [http://dbus.freedesktop.org D-BUS protocol].
 
 
The QtDBus module uses the Qt Signals and Slots mechanism. Applications that like to provide parts of there functionality to the DBus world are able to do so by implementing classes that inherit from the [http://doc.trolltech.com/4.2/qdbusabstractadaptor.html QDBusAbstractAdaptor] class.
 
 
Kross is able to reuse such by an application provided bindings. So, once your application supports dbus, Kross is able to reuse those already existing code and offers transparent access to the scripting-backends to them. How does this differ from e.g. the python-dbus package? Well, first method-calls don't go through the dbus-socket and then it's not dbus-related at all except, that we are able to reuse what your application offers anyway: a clean interface to the outside world. But that's not all, we are not limited to what's possible with dbus. We are also able to exchange instance-pointers to QObject or QWidget instances.
 
 
For an example you may like to take a look at how it was done in the KSpread [http://websvn.kde.org/trunk/koffice/kspread/plugins/scripting/ScriptingModule.cpp?view=markup ScriptingModule] class.
 
  
 
<!-- ################################################################################ //-->
 
<!-- ################################################################################ //-->

Revision as of 03:53, 6 May 2007

noframe
 
This section needs improvements: Please help us to

cleanup confusing sections and fix sections which contain a todo


Contents

Intro

The purpose of this tutorial is to offer a step-by-step introduction how to integrate Kross into your application. While you can integrate Kross also in non-kpartified applications, it's easier to do with the KPart system. This tutorial will assume that you have a kpart application and what we will do is to go step by step through the process of creating a KPart plugin that integrates into your application and provides all the scripting. The scripting functionality is strictly separated from the application. The plugin that implements scripting is optional and the application does not need to know any details about what the plugin does.

This tutorial needs kdelibs4 based on Qt 4.2. While Kross and the KDE Javascript backend are included in kdelibs4, it is needed to compile the KOffice2 libraries to install the Ruby and Python support (will be moved to kdebindings soon).

The whole sourcecode we will produce within this tutorial could also be downloaded as kross2tutorial.tar.gz and contains all files needed to build a simple example that demonstrates how Kross could be used. Download and extract the tarball. Compile, install and run the kross2tutorialapp application and its kross2tutorial KPart plugin now with;

cd src && mkdir _build && cd _build
cmake -DCMAKE_INSTALL_PREFIX=`kde4-config --prefix` ..
make
sudo make install
./kross2tutorialapp

For additional examples where Kross is used you may also like to look at;


The application

This section deals with the question how to integrate Kross into a KPart-application to be able to extend your application with scripting.

For testing purposes we first create a simple KPart application. If you already have an application you may like to skip this section and continue with the KPart Plugin.

Relevant files within the kross2tutorial.tar.gz are;

The CMake build system

The src/CMakeLists.txt file;

project(kross2tutorial)

find_package(KDE4 REQUIRED)
include(KDE4Defaults)
find_package(Perl REQUIRED)
add_definitions(${QT_DEFINITIONS}
  ${KDE4_DEFINITIONS} -DHAVE_CONFIG_H=1)
link_directories(${KDE4_LIB_DIR})
set(CMAKE_REQUIRED_DEFINITIONS
  ${_KDE4_PLATFORM_DEFINITIONS})
include_directories(${CMAKE_SOURCE_DIR}
  ${KDE4_KDECORE_INCLUDES} ${KDE4_INCLUDES}
  ${KDE4_KDEUI_INCLUDES}
  ${KDE4_KPARTS_INCLUDES})

add_subdirectory( plugin )

set(kross2tutorialapp_SRCS
  mainwindow.cpp main.cpp)
kde4_automoc(${kross2tutorialapp_SRCS})
kde4_add_executable(kross2tutorialapp
  ${kross2tutorialapp_SRCS})
target_link_libraries(kross2tutorialapp
  ${KDE4_KDECORE_LIBS} ${KDE4_KDEUI_LIBS}
  kparts krosscore )

The src/plugin/CMakeLists.txt file;

include_directories(${CMAKE_SOURCE_DIR}
  ${KROSS_INCLUDES})
set(krossmoduletutorial_PART_SRCS
  module.cpp part.cpp)
kde4_automoc(${krossmoduletutorial_PART_SRCS})
kde4_add_plugin(krossmoduletutorial
  ${krossmoduletutorial_PART_SRCS})
target_link_libraries(krossmoduletutorial
  ${KDE4_KDECORE_LIBS} ${KDE4_KROSSCORE_LIBS}
  kparts )
install(TARGETS krossmoduletutorial
  DESTINATION ${PLUGIN_INSTALL_DIR})
install(FILES krossmoduletutorial.desktop
  DESTINATION ${SERVICES_INSTALL_DIR})

The KApplication

The main function (main.cpp) creates the KApplication and shows the MainWindow.

int main(int argc, char **argv) {
  KAboutData about();
  KCmdLineArgs::init(argc,argv,&about);
  KApplication app();
  MainWindow *mainWin = new MainWindow();
  mainWin->show();
  return app.exec();
}

The KPart main window

The MainWindow class (mainwindow.h mainwindow.cpp) contains the top-level KParts::MainWindow implementation.

class MainWindow
    : public KParts::MainWindow
{
  public:
    MainWindow()
      : KParts::MainWindow()
    {
      KLibFactory* factory =
        KLibLoader::self()->factory(
          "krossmoduletutorial");
      KParts::ReadWritePart* part =
        dynamic_cast<KParts::ReadWritePart*>
          ( factory->create(this) );
      part->openUrl(
        KUrl("file:///path/myscript.py"));
    }
    virtual ~MainWindow() {}
};


The plugin

The KPart plugin

The Part class (part.h part.cpp) implements a KParts::ReadWritePart.

class Part
  : public KParts::ReadWritePart
{
  public:
    Part(QWidget*, QObject* parent,
      const QStringList&)
      : KParts::ReadWritePart(parent)
      , m_guiclient(
          new Kross::GUIClient(this,this))
      , m_action(0) {}
    virtual ~Part() { delete m_action; }
    virtual bool openFile() {
      delete m_action;
      m_action = new Kross::Action(m_file);
      m_action->trigger();
    }
    virtual bool saveFile() {return false;}
  private:
    Kross::GUIClient* m_guiclient;
    Kross::Action* m_action;
};

The Module

The Module class (module.h module.cpp) implements the "KrossModuleTutorial" module.

class Module : public QObject {
  Q_OBJECT
  public:
    Module(Part* part=0)
      : QObject(part), m_widget(0) {}
    virtual ~Module() {}
  public slots:
    QWidget* widget() {
      if(m_widget) return m_widget;
      Part* part = 
        dynamic_cast<Part*>(parent());
      m_widget = new QWidget(
        part ? part->widget() : 0 );
      m_widget->setLayout(
        new QVBoxLayout(m_widget) );
      QWidget* w = 
        part ? part->widget() : 0;
      if(w && w->layout())
        w->layout()->addWidget(m_widget);
      m_widget->show();
      return m_widget;
    }
  private:
    QWidget* m_widget;
};


Samples

Following sample scripts are also included in the kross2tutorial.tar.gz and should be executed using the "kross2tutorialapp" application.

Python forms script

The sample_forms.py Python script demonstrates usage of into an application embedded Kross forms.

#!/usr/bin/env kross
import Kross
import KrossModuleTutorial
forms = Kross.module("forms")
w = KrossModuleTutorial.widget()
l = forms.createWidget(w,"QLabel")
l.wordWrap = True
l.text = "The labels text."
b = forms.createWidget(w,"QPushButton")
def buttonClicked():
  global forms
  forms.showMessageBox("Information",
    "Caption", "the message text")
b.connect("clicked()", buttonClicked)
b.text = "Show messagebox"

Python Tkinter script

The sample_tkinter.py Python script uses the Tkinter to show a modal dialog.

#!/usr/bin/env kross
class TkTest:
  def __init__(self):
    import Tkinter
    self.root = Tkinter.Tk()
    self.root.title("TkTest")
    self.root.deiconify()
    self.mainframe =
      Tkinter.Frame(self.root)
    self.mainframe.pack()
    self.button1 = Tkinter.Button(
      self.mainframe,
      text="Button1",
      command=self.callback1)
    self.button1.pack(side=Tkinter.LEFT)
    self.root.mainloop()
  def callback1(self):
    import tkMessageBox
    tkMessageBox.showinfo(
      "Callback1", "Callback1 called.")
TkTest()

Ruby forms script

The sample_forms.rb Ruby script uses the Kross forms module to create and embedded a QLabel instance.

#!/usr/bin/env kross
require 'Kross'
require 'KrossModuleTutorial'
forms = Kross.module("forms")
w = KrossModuleTutorial.widget()
l = forms.createWidget(w,"QLabel")
l.wordWrap = true
l.text = "Some labels text"

JavaScript with KjsEmbed script

The sample_kjsembed.js JavaScript script creates and embeddes a QFrame using KjsEmbed.

#!/usr/bin/env kross
w = KrossModuleTutorial.widget()
var f = new Widget("QFrame", w);
f.frameShape = f.StyledPanel;
f.frameShadow = f.Sunken;
f.lineWidth = 4;
f.show();

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