|Because GraphiC supports variable output page sizes, GraphiC needs
to know how to map the internal pixel coordinate system to your output
device. You are free to specify this scaling, but we recommend that it
match the plot length of an L printer dump that you specified when
you set up your printer for use with GraphiC. If you make any other choice,
the sizes on your printer output will not match the specifications in your
This function must be called before page()
or the scaling will not be correct.
You may call PlotLength() instead
of PixPerUnit() to specify the scaling in terms of plot length.