web2c: Modes

 
 6.3 Modes: Device definitions for Metafont
 ==========================================
 
 Running Metafont and creating Metafont base files requires information
 that TeX and MetaPost do not: "mode" definitions which specify device
 characteristics, so Metafont can properly rasterize the shapes.
 
    When making a base file, a file containing modes for
 locally-available devices should be input after 'plain.mf'.  One
 commonly used file is <ftp://ftp.tug.org/tex/modes.mf>; it includes all
 known definitions.
 
    If, however, for some reason you have decreased the memory available
 in your Metafont, you may need to copy 'modes.mf' and remove the
 definitions irrelevant to you (probably most of them) instead of using
 it directly.  (Or, if you're a Metafont hacker, maybe you can suggest a
 way to redefine 'mode_def' and/or 'mode_setup'; right now, the amount of
 memory used is approximately four times the total length of the
 'mode_def' names, and that's a lot.)
 
    If you have a device not included in 'modes.mf', please see comments
 in that file for how to create the new definition, and please send the
 definition to <tex-fonts@math.utah.edu> to get it included in the next
 release of 'modes.mf'.
 
    Usually, when you run Metafont you must supply the name of a mode
 that was dumped in the base file.  But you can also define the mode
 characteristics dynamically, by invoking Metafont with an assignment to
 'smode' instead of 'mode', like this:
      mf '\smode:="newmode.mf"; mag:=MAGNIFICATION; input MFNAME'
 This is most useful when you are working on the definition of a new
 mode.
 
    The MAGNIFICATION and MFNAME arguments are explained in ⇒mf
 invocation.  In the file 'newmode.mf', you should have the following
 (with no 'mode_def' or 'enddef'), if you are using 'modes.mf'
 conventions:
      mode_param (pixels_per_inch, DPI);
      mode_param (blacker, B);
      mode_param (fillin, F);
      mode_param (o_correction, O);
      mode_common_setup_;
 (Of course, you should use real numbers for DPI, B, F, and O.)
 
    For more information on the use of 'smode', or if you are not using
 'modes.mf', see page 269 of 'The Metafontbook'.