Testing a plasmoid with local installation

[Gregor Mi]

Hi,

I would like to install a (KDE4) plasmoid locally to test it with
plasmoidviewer.

As example I use kdeplasma-addons/applets/showdesktop/ from
https://projects.kde.org/projects/kde/kdeplasma-addons

I did the following setup
$ cd src/kdeplasma-addons
$ mkdir build
$ cd build
$ . home-kde4-env-setup # which sets DEVUSR, XDG_DATA_DIRS, PATH,
                        # LD_LIBRARY_PATH, CMAKE_PREFIX_PATH
  # DEVUSR is my local usr directory
$ cmake .. -DCMAKE_INSTALL_PREFIX=$DEVUSR
$ make install

$ plasmapkg --list | grep desktop
lists showdesktop. This is the original (system installed) one, because
kbuildsycoca4 was not called yet.

To make sure that the original plasmoid is not found by the next command
I moved the file
/usr/share/kde4/services/plasma-applet-showdesktop.desktop away.

Now:
$ kbuildsycoca4
$ plasmapkg --list | grep desktop
This does NOT show the locally installed plasmoid.

So I am a little lost here. What conditions must hold so that
kbuildsycoca4 finds the locally installed files (.desktop and .so) to
make them available for plasmapkg?

Thanks for any hint.

Gregor