You should not need to set QTDIR because it should already been automatically
configured (in '/etc/profile.d/@QT@dir.sh' and '/etc/profile.d/@QT@dir.csh').

To check if it is the case, do 'echo $QTDIR'. Answer should be '@QTDIR@'.

If it is not the case, do 'export QTDIR=@QTDIR@' if you use bash or
'setenv QTDIR @QTDIR@/' if you use csh.

Qt documentation is in /usr/share/doc/qt-@QtVersion@/ (you need to
install package @QT@-doc-@PackageVersion@ if it is not already
done).

Other Qt things are in @QTDIR@/ (which contains needed symlinks
to create a fake QTDIR).

Examples and tutorials are compressed to save space. If you want to use them,
you need to uncompress them somewhere in your home directory using:
'cd your_directory; tar xvfj /usr/share/doc/qt-@QtVersion@/examples.tar.bz2'.

You may override placement of @QTHOME@ directory with settings files
by exporting XDG_CONFIG_HOME variable before start Qt-based application.