Difference between revisions of "Development/Tutorials/Write a Flake Plugin"

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(Copy paste from koffice wiki.)
 
(Minor cleanup)
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This tutorial will guide you step by step through the creation of a flake shape. At the end you will be able to write a shape that is loadable by any KOffice application.
+
This tutorial will guide you step by step through the creation of a [http://wiki.koffice.org/index.php?title=Flake Flake] shape. At the end you will be able to write a shape that is loadable by any KOffice application.
  
 
=Do the groundwork - create a shape=
 
=Do the groundwork - create a shape=
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The only method you '''have''' to reimplement is the [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#027c57ec3dc4360294c5bb7330c768d7 paint()] method which is responsible for painting your shape.
 
The only method you '''have''' to reimplement is the [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#027c57ec3dc4360294c5bb7330c768d7 paint()] method which is responsible for painting your shape.
  
You should also implement the [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#8df944b51caa617049593bfa2ff4de49 boundingRect()] method to return the rectangle around your shape. What you might be interested in is the [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#09a45358ef20c372675790531989d5b6 resize()] and [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#5bc408a6f4d7f0bd0ea832002b96ac83 size()] method which set the available size to the shape. Some shapes define the size they need on their own so they reimplement size() to return the size they have.
+
What you might be interested in is the [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#09a45358ef20c372675790531989d5b6 resize()] and [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#5bc408a6f4d7f0bd0ea832002b96ac83 size()] method which set the available size to the shape. Some shapes define the size they need on their own so they reimplement size() to return the size they have.  
 
+
Note from TZ: the boundingRect does not have to be reimplemented
+
if the shape properly returns a size().
+
  
 
An example for this is the KoFormulaShape. A formula has a fixed size due to its contents and so KoFormulaShape reimplements the size() method.
 
An example for this is the KoFormulaShape. A formula has a fixed size due to its contents and so KoFormulaShape reimplements the size() method.
 
If your shape has a special outline, reimplement [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#71ac11dbac93b5bff2f91fb768fa17e5 outline()] to return your shape's outline correctly.
 
If your shape has a special outline, reimplement [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html#71ac11dbac93b5bff2f91fb768fa17e5 outline()] to return your shape's outline correctly.
  
The rotation, scaling and scewing is done through a matrix and so you don't need to care about it.
+
The rotation, scaling and skewing is done through a matrix and so you don't need to care about it.
  
 
So here is an example how your code might look like:
 
So here is an example how your code might look like:
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     // absolutly necessary:
 
     // absolutly necessary:
 
     void paint( QPainter &painter, const KoViewConverter &converter );
 
     void paint( QPainter &painter, const KoViewConverter &converter );
 
    // not strictly necessary:
 
    void resize( const QSizeF &size );
 
    QSizeF size();
 
    QRectF boundingRect() const;
 
    const QPainterPath outline();
 
  
 
private:
 
private:
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=Make your shape loadable - create a factory and a plugin=
 
=Make your shape loadable - create a factory and a plugin=
  
Now when you have created your shape class and implemented all the necessary things you can think about the loading of your shape.
+
Now when you have created your shape class and implemented all the necessary things to make it at least compile you can think about the loading of your shape.
  
 
The KOffice apps use [http://koffice.org/developer/apidocs/libs-flake/classKoShapeFactory.html KoShapeFactory] to get instances of shapes in a generic way. This way of obtaining shape instances is designed after [http://en.wikipedia.org/wiki/Abstract_factory_pattern the factory pattern]. So you should also implement a KoShapeFactory derived class that makes creating new instances of your shape possible. The factory class has to implement two methods:  
 
The KOffice apps use [http://koffice.org/developer/apidocs/libs-flake/classKoShapeFactory.html KoShapeFactory] to get instances of shapes in a generic way. This way of obtaining shape instances is designed after [http://en.wikipedia.org/wiki/Abstract_factory_pattern the factory pattern]. So you should also implement a KoShapeFactory derived class that makes creating new instances of your shape possible. The factory class has to implement two methods:  
  
* KoShape* createDefaultShape();
+
* KoShape* createDefaultShape() const;
 
* KoShape* createShape( const KoProperties* params ) const;
 
* KoShape* createShape( const KoProperties* params ) const;
  
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public:
 
public:
 
     FooShapeFactory( QObject *parent );
 
     FooShapeFactory( QObject *parent );
    ~FooShapeFactory();
 
  
 
     KoShape* createDefaultShape() const;
 
     KoShape* createDefaultShape() const;
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{
 
{
 
     KoFooShape* fooShape = new KoFooShape();
 
     KoFooShape* fooShape = new KoFooShape();
     // set the defaults
+
     // set defaults
 
     return fooShape;
 
     return fooShape;
 
}
 
}
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KoShape* FooShapeFactory::createShape( const KoProperties* params ) const
 
KoShape* FooShapeFactory::createShape( const KoProperties* params ) const
 
{
 
{
 +
    KoFooShape* fooShape = new KoFooShape();
 
     // use the params
 
     // use the params
     return new KoFooShape();
+
     return fooShape;
 
}
 
}
 
</pre>
 
</pre>
  
With the factory there is now a generic way to obtain an instance of your shape. But somehow you have to publish your shape as a plugin to let the KOffice application know that there is a plugin to load. Therefore the flake library provides the [http://koffice.org/developer/apidocs/libs-flake/classKoShapeRegistry.html KoShapeRegistry] class. Each application has access to the registry and to let the app know about your shape you have to register it within the registry.
+
With the factory there is now a generic way to obtain an instance of your shape. But somehow you have to publish your shape as a plugin to let the KOffice application know that there is a plugin to load. Therefore the flake library provides the [http://koffice.org/developer/apidocs/libs-flake/classKoShapeRegistry.html KoShapeRegistry] class. Each application has access to the registry and to let the application know about your shape you have to register it within the registry.
  
 
To register we would have to make a call like this:
 
To register we would have to make a call like this:
 
  KoShapeRegistry::instance()->add( new FooShapeFactory( parent ) );
 
  KoShapeRegistry::instance()->add( new FooShapeFactory( parent ) );
In order to make that call, we will create a plugin class which is special in that it will be automatically loaded and created by KOffice when an application starts.  This means that the constructor of our plugin class will be the perfect place to actually register our shape.
+
In order to make that call, we will create a plugin class which is special in that it will be automatically loaded and created by KOffice when an application starts.  This means that the constructor of our plugin class will be the perfect place to actually register our shape using the above line.
  
 
The registration is done within the constructor of the FooShapePlugin class. This is a very simple class that represents the plugin and does registration.
 
The registration is done within the constructor of the FooShapePlugin class. This is a very simple class that represents the plugin and does registration.
Line 97: Line 88:
 
public:
 
public:
 
     FooShapePlugin(QObject *parent, const QStringList & );
 
     FooShapePlugin(QObject *parent, const QStringList & );
    ~FooShapePlugin() {}
 
 
};
 
};
 
</pre>
 
</pre>

Revision as of 14:32, 15 March 2007

This tutorial will guide you step by step through the creation of a Flake shape. At the end you will be able to write a shape that is loadable by any KOffice application.

Do the groundwork - create a shape

First of all you need a class derived from the KoShape class. This will be the actual shape class so you have to ensure that all the data you need for painting is accessable for this KoShape derived class. The only method you have to reimplement is the paint() method which is responsible for painting your shape.

What you might be interested in is the resize() and size() method which set the available size to the shape. Some shapes define the size they need on their own so they reimplement size() to return the size they have.

An example for this is the KoFormulaShape. A formula has a fixed size due to its contents and so KoFormulaShape reimplements the size() method. If your shape has a special outline, reimplement outline() to return your shape's outline correctly.

The rotation, scaling and skewing is done through a matrix and so you don't need to care about it.

So here is an example how your code might look like:

#include <KoShape.h>

class KoFooShape : public KoShape {
public:
    KoFooShape();
    ~KoFooShape();

    // absolutly necessary:
    void paint( QPainter &painter, const KoViewConverter &converter );

private:
    SomeDataClass* m_dataClass;
};

Make your shape loadable - create a factory and a plugin

Now when you have created your shape class and implemented all the necessary things to make it at least compile you can think about the loading of your shape.

The KOffice apps use KoShapeFactory to get instances of shapes in a generic way. This way of obtaining shape instances is designed after the factory pattern. So you should also implement a KoShapeFactory derived class that makes creating new instances of your shape possible. The factory class has to implement two methods:

  • KoShape* createDefaultShape() const;
  • KoShape* createShape( const KoProperties* params ) const;

An example factory class definition:

class FooShapeFactory : public KoShapeFactory {
public:
    FooShapeFactory( QObject *parent );

    KoShape* createDefaultShape() const;
    KoShape* createShape( const KoProperties* params ) const;
};

The according implementation:

FooShapeFactory::FooShapeFactory( QObject* parent) 
   : KoShapeFactory( parent, "FooShape", i18n("Foo Shape") )
{
    setToolTip( i18n("A foo shape") );
}

KoShape* FooShapeFactory::createDefaultShape() const
{
    KoFooShape* fooShape = new KoFooShape();
    // set defaults
    return fooShape;
}

KoShape* FooShapeFactory::createShape( const KoProperties* params ) const
{
    KoFooShape* fooShape = new KoFooShape();
    // use the params
    return fooShape;
}

With the factory there is now a generic way to obtain an instance of your shape. But somehow you have to publish your shape as a plugin to let the KOffice application know that there is a plugin to load. Therefore the flake library provides the KoShapeRegistry class. Each application has access to the registry and to let the application know about your shape you have to register it within the registry.

To register we would have to make a call like this:

KoShapeRegistry::instance()->add( new FooShapeFactory( parent ) );

In order to make that call, we will create a plugin class which is special in that it will be automatically loaded and created by KOffice when an application starts. This means that the constructor of our plugin class will be the perfect place to actually register our shape using the above line.

The registration is done within the constructor of the FooShapePlugin class. This is a very simple class that represents the plugin and does registration.

Example plugin class definition:

#include <QObject>

class FooShapePlugin : public QObject {
    Q_OBJECT
public:
    FooShapePlugin(QObject *parent, const QStringList & );
};

Example plugin class implementation:

#include "FooShapePlugin.h"
#include <kgenericfactory.h>

K_EXPORT_COMPONENT_FACTORY(fooshapelibrary, KGenericFactory<FooShapePlugin>( "FooPlugin" ) )

FooShapePlugin::FooShapePlugin( QObject *parent, const QStringList& ) 
   : QObject(parent)
{
    // register the shape's factory
    KoShapeRegistry::instance()->add( new KoFooShapeFactory( parent ) );
    // we could register more things here in this same plugin.
}
#include "FooShapePlugin.moc"

This demonstrates how for the plugin related tasks KDE provides services which are dynamic loaded libraries. The secret ingredient that makes this class the plugin of that library is the call to the K_EXPORT_COMPONENT_FACTORY macro defined in kgenericfactory.h

We now have a way to create instances of your shape (FooShapeFactory), a way to register them for the apps (KoShapeRegistry) and a plugin that can dynamically be loaded (FooShapePlugin). The last step is to create a .desktop file that describes your plugin and makes it findable by KOffice. For "X-KDE-Library" you have to set the library name you have already specified within K_EXPORT_COMPONENT_FACTORY().

Example fooshape.desktop file:

[Desktop Entry]
Encoding=UTF-8
Name=Foo Shape
ServiceTypes=KOffice/Flake
Type=Service
X-KDE-Library=fooshapelibrary
X-Flake-Version=1

After installing that file in the kde services directory and installing your plugin where the application can open it, your plugin is system wide known and can be loaded by KOffice.

TODO; add example CMake file.

Make your shape editable - create a tool

To edit your shape in the GUI the user wants to select a tool and alter your shape. Therefore you have to provide a KoTool derived class. This class implements all edit actions that can be done on your shape but it is also possible to have more than one tool per shape.

Note from TZ:  I suggest creating a koffice/shapes/example dir in svn 
which you can refer to from this tutorial.

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