Currently the calculator uses an open grid. It's a matter of taste but
I prefer a closed grid.
Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
Currently the coordindates used for line drawing are "tuned" for a bug in
the line drawing code (and now draw off the edge of the screen). Fix this.
Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
