Instead of a host of virtual functions, let the base class
(DiveCartesianAxis) do the formatting of the axis labels.
To do so, it needs to know how to convert the internal
representation (e.g. mm) into the displayed value (e.g. feet).
Moreover, this transformation has to be adapted when changing
the locale-setting, therefore do it for every plot() call.
The transformation itself cannot be a simple linear translation,
because we have non-absolute display units, namely °C and °F.
Thankfully affine transformations are enough though.
Only one custom formatter remains: the time axis. It might
be a good idea to remove the virtual function and do this
via a flag.
This is all done not so much for code simplification, but
because for a general layout of the axis labels, the
axis has to understand the values of the labels and not
only handle them as opaque texts.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
177df72d33