Development/Tutorials/Games/Palapeli Slicers

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Creating a Palapeli pattern
Tutorial Series   Programming with the Palapeli API
Previous   Introduction to KDE4 programming
What's Next   n/a
Further Reading   Palapeli::Pattern, Palapeli::PatternConfiguration
I'm currently creating this tutorial. You should not edit this page in the mean time. -- Majewsky 18:19, 20 July 2008 (CEST)
Warning to editors


This tutorial shows you how to create a pattern for Palapeli, that is: a plugin for the Palapeli libraries that describes an algorithm to split an image into pieces.

The pattern we will be constructing is quite easy: It splits an image into two equally sized pieces.


A pattern plugin consists of two classes. The first one (derived from Palapeli::PatternConfiguration) tells Palapeli what features this pattern plugin has and which configuration values it needs. The second one (derived from Palapeli::Pattern) does the actual slicing.

The code: mypattern.h

  1. ifndef MYPATTERN_H
  2. define MYPATTERN_H
  1. include <Palapeli/Pattern>
  2. include <Palapeli/PatternConfiguration>

class MyPattern : public Palapeli::Pattern { public: MyPattern(); virtual ~MyPattern() {}

virtual int estimatePieceCount() const; protected: virtual void doSlice(const QImage& image); };

class MyPatternConfiguration : public Palapeli::PatternConfiguration { public: MyPatternConfiguration(QObject* parent = 0, const QVariantList& args = QVariantList()); virtual ~MyPatternConfiguration() {} virtual Palapeli::Pattern* createPattern() const; };

  1. endif // MYPATTERN_H

As described above, we have declared two classes deriving from the base classes Palapeli::Pattern and Palapeli::PatternConfiguration. For this simple example, we do only reimplement constructors, destructors and some pure virtual functions.

The code: mypattern.cpp

  1. include "mypattern.h"
  1. include <QImage>
  2. include <KPluginFactory>
  3. include <KPluginLoader>

K_PLUGIN_FACTORY(MyPatternFactory, registerPlugin<MyPatternConfiguration>();) K_EXPORT_PLUGIN(MyPatternFactory("mypattern"))

MyPattern::MyPattern() : Palapeli::Pattern() { }

int MyPattern::estimatePieceCount() const {

   return 2;


void MyPattern::doSlice(const QImage& image) {

   //construct pixmaps for the pieces
   const int pieceWidth = image.width() / 2, pieceHeight = image.height();
   QImage leftPiece = image.copy(QRect(0, 0, pieceWidth, pieceHeight));
   QImage rightPiece = image.copy(QRect(pieceWidth, 0, pieceWidth, pieceHeight));
   //add pieces; define a neighborship relation between them
   addPiece(leftPiece, QRectF(0, 0, pieceWidth, pieceHeight));
   addPiece(rightPiece, QRectF(pieceWidth, 0, pieceWidth, pieceHeight));
   addRelation(0, 1, QPointF(pieceWidth, 0)); //0 and 1 are the consecutive indices of the pieces


MyPatternConfiguration::MyPatternConfiguration(QObject* parent, const QVariantList& args)

   : Palapeli::PatternConfiguration(parent, args)




Palapeli::Pattern* MyPatternConfiguration::createPattern() const {

   return new MyPattern;


We will start with the MyPatternConfiguration class, because this is the logical entry point. The pattern configuration class is created when Palapeli is started. It i

Integrate into Palapeli: mypattern.desktop

[Desktop Entry] X-KDE-Library=mypattern X-KDE-PluginInfo-Author=The best KDE hacker X-KDE-PluginInfo-Name=mypattern X-KDE-PluginInfo-Version=1.0 X-KDE-PluginInfo-Website= X-KDE-PluginInfo-Category= X-KDE-PluginInfo-Depends= X-KDE-PluginInfo-License=GPL X-KDE-PluginInfo-EnabledByDefault=true X-KDE-ParentApp=libpalapelipattern X-KDE-ServiceTypes=Palapeli/PatternPlugin Type=Service Icon=palapeli-pattern-mypattern PatternIdentifier=mypattern Name=My pattern Name[de]=Mein Schnittmuster Comment=The best pattern in the world Comment[de]=Das beste Schnittmuster auf der ganzen Welt

Build everything: CMakeLists.txt


find_package(KDE4 REQUIRED) find_package(Palapeli REQUIRED)

add_definitions(${QT_DEFINITIONS} ${KDE4_DEFINITIONS}) include_directories(${KDE4_INCLUDES} ${PALAPELI_INCLUDE_DIR})

set(mypattern_SRCS mypattern.cpp )

kde4_add_plugin(mypattern ${mypattern_SRCS}) target_link_libraries(mypattern ${KDE4_KDEUI_LIBS} palapelipattern)


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