Instead of calculating the label sizes of the axes when
relayouting the chart, calculate them at construction time.
To do so, pass the digits before and after the decimal comma
to the constructor.
This is not so much an optimization thing, but rather an
first stab at more general label rendering. Time, of course,
will always be an exception. But hopefully the remaining
values can be done more generally.
Note that currently this code is a total mess. For example,
the labels for the temperature axes are not converted to
F if needed. And therefore also not shown. This will need
some major rethinking.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
322e2baa8d