> Resolving bug report 892 includes important patches to reduce potential
> conflict with KDE4 and to make our own *.desktop files XDG compliant
> (recently Trinity/TDE was added to the list of registered environments:
> http://standards.freedesktop.org/menu-spec/latest/apb.html).
>
> Resolving this bug report is important to release R14.
<snip>

I am fairly certain that what you are looking for is in the file
cmake/modules/TDESetupPaths.cmake, specifically the line which sets
XDG_APPS_INSTALL_DIR

tde-config is generate from tdecore/tde-config.cpp.cmake, which uses
XDG_APPS_INSTALL_DIR as defined during the build process.

Tim