Development/Tutorials/KDE4 Porting Guide (de)

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Diese Anleitung richtet sich an Entwickler, die ihre Qt3/KDE3 basierten Applikationen nach Qt4/KDE4 portieren wollen. Das muß nämlich kein komplizierter Prozess sein. Es gibt bereits viele Skripte und Dokumentationen, die dabei helfen.


Für die Anweisungen dieser Anleitung gelten folgende Konventionen:

  • program bezeichnet ein ausführbares Programm
  • path bezeichnet einen Pfad
  • file bezeichnet eine Datei
  • $SVN ist der vollständige Pfad zu Ihrem KDE subversion depot.


Anders als KDE4 werden KDE4 Applikationen mit der Hilfe von CMake erstellt. Der einfachste Weg die autotools Dateien nach CMake zu portieren ist, das Script am2cmake zu benutzen, welches im Verzeichnis cmake/scripts des kdesdk Modules zu finden ist. Das erzeugt eine Reihe von CMakeLists.txt Dateien neben den alten autotools Dateien.

Ist Ihr Code zum Beispiel unter /path/to/src gespeichert, dann: % cd /path/to/src % $SVN/trunk/KDE/kdesdk/cmake/scripts/am2cmake --kde4 Führen Sie am2cmake --help aus, um zu prüfen, ob Sie das --kde4 Flag benötigen.

Weiterhin gibt es ein Werkzeug, welches in den erzeugten CMakeList.txt Dateien nach möglichen Problemen sucht. Dieses Werkzeugt heißt und ist unter$SVN/trunk/kde/kdesdk/scripts gespeichert. Benutzen Sie es folgendermaßen: % cd /path/to/src % $SVN/trunk/KDE/kdesdk/scripts/ CMakeLists.txt Oder wenden Sie es auf das gesamte Quellcodevrzeichnis an: % cd /path/to/src % find . -name CMakeLists.txt | \

 xargs $SVN/trunk/KDE/kdesdk/scripts/


An overview of the Qt3 to Qt4 transition is provided in Trolltech's "Moving from Qt 3 to Qt 4" paper. This document provides an excellent overview into the major functionality changes with Qt4 and is highly recommended.

The follow-on "Porting to Qt 4" page gives an amazingly detailed description of the porting process, along with a list of the changes in the classes and functions.

These documents describe a tool provided by Trolltech called qt3to4 that can help port the Qt parts of your code from Qt3 to Qt4, using compatibility functions. Run qt3to4 as follows: % $SVN/trunk/qt-copy/bin/qt3to4 [options] <Infile>, [Infile], ... Infile can be a source file or a project file. If you specify a project file, ending with '.pro' or '.pri', qt3to4 will port all files specified in that project.

For more information, run qt3to4 with the "--help" option or visit the "qt3to4-The Qt 3 to 4 Porting Tool" page.

Additionally, there is a program called in the kdesdk module that will search and replace lots of deprecated Qt3 stuff for you. Simply run this program without any options in the source directory. % $SVN/trunk/KDE/kdesdk/scripts/qt4/


Much of the porting effort consists of simply renaming class names and header files. Since it would be rather tedious to change all these by hand, there is a handy script in the scripts/qt4 directory of kdesdk called This will scan all your files and create a diff output which can then be used to patch your code.

Once that simple code substitution has been done, you will still have to go through your code to port to, for example, the new KAction API. Documentation about all API changes is kept in the KDE4PORTING.html file in the kdelibs module.

Qt Designer UI Dateien

Qt designer ".ui" files created using Qt3 must be converted to the new Qt4 format. This can be done using the uic3 program available from your Qt4 installation.

% $SVN/trunk/qt-copy/bin/uic3 -convert file.ui > foo.ui % mv foo.ui file.ui

Or, if you prefer a graphical tool, you can use Qt4's designer program

% $SVN/trunk/qt-copy/bin/designer file.ui (you can save file.ui over top itself, or save to a new file)

Beware, the conversion process loses any custom slots, table columns, etc. So, you may need to put some stuff back by hand.

You should also run the fixuifiles program from the kdesdk module, it performs cleanups and sanify checks: % $SVN/trunk/KDE/kdesdk/scripts/fixuifiles


Instead of DCOP in KDE3, KDE4 now uses D-Bus for its interprocess communication. Porting from DCOP to D-Bus is a large topic that is covered in great detail in the Porting to D-Bus tutorial.

For more information, please see all our D-Bus tutorials.


KDE4 uses the icon naming specification as the basis for icon names. This means that both the icons that ship with KDE4 (Oxygen) as well as components in kdelibs that use icons follow this specification.

Porting your app from the icon names used in KDE3 to the ones used in KDE4 is as easy as running the script from the root directory of your project and follow the instructions on screen.

The script automatically converts confirmable positives (e.g. uses of KIcon or KIconLoader), skips confirmable negatives and prompts for what to do with possible positives. It shows the latter with additonal context if desired and makes it a simple matter of pressing 'y' or 'n' for the possible hits to complete the porting.


To create your ".pot" file, copy the commands from the 'messages' rule in your projects to a shell script called You may assume the same variables ($PREPARETIPS, $XGETTEXT, $podir, etc.) still exist, but keep in mind the differences between Makefile and shell script syntax.

Also be careful that if you use the -k parameter with $XGETTEXT, you will need to explicitely list all variants that you use.

For example, the 'messages' creation rule: messages: rc.cpp

       rm -f tips.cpp
       $(PREPARETIPS) > tips.cpp
       $(XGETTEXT) -ktranslate *.cpp *.h -o $(podir)/kmail.pot
       rm -f tips.cpp

becomes the following script:

  1. ! /usr/bin/env bash

$PREPARETIPS > tips.cpp $XGETTEXT -ktranslate:1,1t -ktranslate:1c,2,2t *.cpp *.h -o $podir/kmail.pot rm -f tips.cpp

Do's und Don'ts

  • Do NOT use the old-style socket classes.
  • Do NOT use QPtrList, and in general, setAutoDelete()
  • Do NOT make use of raster operations.
  • Do NOT do code painting on widgets outside paint events.
  • Try not to use QHBox, QVBox, QGrid. Prefer layouts instead.
  • Do NOT play with frames of groupboxes, labels, or lineedits to fake a different widget. Use the appropriate widget instead. e.g., instead of setting a label to have a sunken lineedit border, how about using a readonly KLineEdit instead? And instead of using a KLineEdit without a border for a copyable widget, use KActiveLabel.
  • Do NOT use a groupbox without border to group widgets! Just use a layout.

Mehr Informationen


Weitere Hilfe

  • #kde4-devel on

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