KConfigXT for KWin Effects
To port the configuration of an Effect to KConfigXT no programming skills are required, though can be helpful. The task is to move the configuration from being hard coded values in the source code into an XML definition from which source code get's generated. This improves the maintenance of the source code and makes it more difficult to have errors caused by typos. Furthermore the business logic to update and track the user interface can be managed automatically limiting the risk of errors there.
Last but not least it allows to move the configuration interfaces in future to new technologies like QML.
Performing a Port
Best first read the tutorial on KConfigXT, then pick an effect of those listed below. The source code for the effects can be found here, each effect is in an own sub directory. Locate the file effectname_config.cpp, that's the most important one to look at. In there you find some code starting with void EffectNameConfig::load(), there you find many readEntry() lines. Each readEntry contains the name of the config option, the default value and the data type. Each of these config options becomes an entry in the kcfg file.
Now start creating the kcfg file. As a name use effectname.kcfg. For the name attribute of "kcfgfile" use kwinrc. The kcfg file should have exactly one group. The name of this you can find in the source code in a method call EffectsHandler::effectConfig("Foo") which gets appended to a Effect-, e.g. Effect-Foo. This should be enough to define the complete kcfg file for the effect.
The next step is to update the ui file in the same directory. Best do that in Qt designer and for each widget update the object name to be kcfg_ConfigOption as explained in the tutorial.
Now all that is needed is defining the kcfgc file:
File=foo.kcfg ClassName=FooConfig NameSpace=KWin Singleton=true Mutators=true
If you have some developer experience, please also update the CMakeLists.txt and the source code of the effect and the configuration. Though this is no requirement.
A complete example for such a port can be found in Review Request for Translucency Effect.
Publish the Result
Best is to upload a Review Request on Review Board for group KWin. Alternative is to send your changes to KWin's mailing list. Bonus for being a git format-patched diff as that allows that the change in the repository will be addressed to the correct author. (see Techbase - Git/Create a patch)