Development/Tutorials/Write a Flake Plugin: Difference between revisions

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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.
{{Review|Port to KF5}}


For an introduction of KOffice plugins, see [[Development/Tutorials/KOffice Overview]] and for a technical introduction to plugins in KOffice see [[Development/Tutorials/Generic KOffice Plugin Creation|Generic KOffice Plugin Creation]]
This tutorial will guide you step by step through the creation of a [http://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/index.html Flake] shape. At the end you will be able to write a shape that is loadable by any Calligra application.
 
For an introduction of Calligra plugins, see [[Development/Tutorials/Calligra Overview]] and for a technical introduction to plugins in Calligra see [[Development/Tutorials/Generic Calligra Plugin Creation|Generic Calligra Plugin Creation]]


=Do the groundwork - create a shape=
=Do the groundwork - create a shape=


First of all you need a class derived from the [http://koffice.org/developer/apidocs/libs-flake/classKoShape.html 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.
First of all you need a class derived from the [http://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/classKoShape.html 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 [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://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/classKoShape.html#aa8c0b86021fd00d28b08e3002c68e4bf paint()] method which is responsible for painting 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://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/classKoShape.html#aa8c0b86021fd00d28b08e3002c68e4bf setSize()] and [http://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/classKoShape.html#aa9b12b2086f3bcaab2958a9a79f4636d 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.
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://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/classKoShape.html#a2910817b9efac8cb464d70d3c3e52262 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.
The rotation, scaling and skewing is done through a matrix and so you don't need to care about it.
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     SomeDataClass* m_dataClass;
     SomeDataClass* m_dataClass;
};
};
</code>
</syntaxhighlight>


=Make your shape loadable - create a factory and a plugin=
=Make your shape loadable - create a factory and a plugin=
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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.
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 Calligra apps use [http://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/classKoShapeFactoryBase.html KoShapeFactoryBase] 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 KoShapeFactoryBase derived class that makes creating new instances of your shape possible. The factory class has to implement two methods:  


* KoShape* createDefaultShape() const;
* KoShape* createDefaultShape() const;
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     KoShape* createShape(const KoProperties* params) const;
     KoShape* createShape(const KoProperties* params) const;
};
};
</code>
</syntaxhighlight>
The according implementation:
The according implementation:
<syntaxhighlight lang="cpp-qt">
<syntaxhighlight lang="cpp-qt">
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     return fooShape;
     return fooShape;
}
}
</code>
</syntaxhighlight>


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.
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 Calligra application know that there is a plugin to load. Therefore the flake library provides the [http://api.kde.org/bundled-apps-api/calligra-apidocs/libs/flake/html/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:
<syntaxhighlight lang="cpp-qt">
<syntaxhighlight lang="cpp-qt">
KoShapeRegistry::instance()->add( new FooShapeFactory( parent ) );
KoShapeRegistry::instance()->add( new FooShapeFactory( parent ) );
</code>
</syntaxhighlight>
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.
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 Calligra 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.
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     FooShapePlugin(QObject *parent, const QStringList&);
     FooShapePlugin(QObject *parent, const QStringList&);
};
};
</code>
</syntaxhighlight>


Example plugin class implementation:
Example plugin class implementation:
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}
}
#include "FooShapePlugin.moc"
#include "FooShapePlugin.moc"
</code>
</syntaxhighlight>
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 {{path|kgenericfactory.h}}
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 {{path|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 {{path|.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().
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 {{path|.desktop}} file that describes your plugin and makes it findable by Calligra. For "X-KDE-Library" you have to set the library name you have already specified within K_EXPORT_COMPONENT_FACTORY().


Example {{path|fooshape.desktop}} file:
Example {{path|fooshape.desktop}} file:
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Encoding=UTF-8
Encoding=UTF-8
Name=Foo Shape
Name=Foo Shape
ServiceTypes=KOffice/Flake
ServiceTypes=Calligra/Flake
Type=Service
Type=Service
X-KDE-Library=fooshapelibrary
X-KDE-Library=fooshapelibrary
X-Flake-Version=1
X-Flake-Version=1
</code>
</syntaxhighlight>


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.
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 Calligra.


TODO; add example CMake file.
TODO; add example CMake file.

Latest revision as of 08:39, 31 May 2019

Warning
This page needs a review and probably holds information that needs to be fixed.

Parts to be reviewed:

Port to KF5

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 Calligra application.

For an introduction of Calligra plugins, see Development/Tutorials/Calligra Overview and for a technical introduction to plugins in Calligra see Generic Calligra Plugin Creation

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 setSize() 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 );
    virtual bool loadOdf(const KoXmlElement & element, KoShapeLoadingContext &context);
    virtual void saveOdf(KoShapeSavingContext & context) const;

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 Calligra apps use KoShapeFactoryBase 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 KoShapeFactoryBase 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 Calligra 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 Calligra 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 Calligra. 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=Calligra/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 Calligra.

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.