The plugin allows to create a KDecoration2::DecorationButton by
registering the keyword "button". If such a button is created the
rendering is slightly adjusted to always have the normal background,
so that it works as in a Preview.
This new decoration plugin requires the new API which needs to
be built from:
kde:kdecoration
To view the decoration use the tool available in
kde:kdecoration-viewer
It is not yet integrated into KWin. One cannot use the decoration yet.