When changing from relative to absolute scaling of the char
elements, positioning of the picture thumbnails was broken.
To emulate the old behavior, add a function to DiveCartesianAxis,
that allows positioning with respect to the axis on the screen.
To simplify tuning of the poctuire positions, name a few
constants explicitly.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>