%%% ====================================================================
%%%  @METAFONT-file{
%%%     author          = "Alan Jeffrey",
%%%     version         = "1.1",
%%%     date            = "02 June 1992",
%%%     time            = "13:36:35 BST",
%%%     filename        = "diagramf.mf",
%%%     address         = "School of Cognitive and Computing Sciences
%%%                        University of Sussex
%%%                        Brighton BN1 9QH
%%%                        UK",
%%%     telephone       = "+44 273 606755 x 3238",
%%%     FAX             = "+44 273 678188",
%%%     checksum        = "49217 319 1584 10327",
%%%     email           = "alanje@cogs.sussex.ac.uk",
%%%     codetable       = "ISO/ASCII",
%%%     keywords        = "diagrams, metafont",
%%%     supported       = "yes",
%%%     abstract        = "This is a metafont program which provides
%%%                        commands for setting labels in TeX.",
%%%     docstring       = "This is part of the diagramf package which
%%%                        interfaces TeX and metafont.  It is
%%%                        described in diagramf.tex.
%%%
%%%                        Copyright 1992 Alan Jeffrey.
%%%
%%%                        The checksum field above contains a CRC-16
%%%                        checksum as the first value, followed by the
%%%                        equivalent of the standard UNIX wc (word
%%%                        count) utility output of lines, words, and
%%%                        characters.  This is produced by Robert
%%%                        Solovay's checksum utility.",
%%%     package         = "diagramf",
%%%     dependencies    = "diagramf.sty",
%%%     maintainer      = "Jeremy Gibbons",
%%%     address-maintainer = "Department of Computer Science
%%%                        University of Aukland
%%%                        Private Bag
%%%                        Aukland
%%%                        New Zealand",
%%%     email-maintainer = "jeremy@cs.aukuni.ac.nz",
%%%  }
%%% ====================================================================
%%%
%%% 25 Oct 1990, v1.0: Released version 1.0.
%%%
%%% 2 Jun 1992, v1.1: Added standard headers.

diagramfbaseloaded := 1;

% This is a metafont program for describing diagrams with TeX labels
% on them.  The mf code is of the form:
%
%    begindiagram (NUMBER,WIDTH,HEIGHT,DEPTH);
%       hboxes (LISTOFBOXES);
%       ...
%    enddiagram;
%
% where NUMBER is the diagram number and LISTOFBOXES is a list of the
% labels used in that diagram.  The fancy thing is that characters can
% contain the variables
%
%    hboxSOMETHING[N]
%
% where N is a number and SOMETHING is one of bl, l, tl, br, r, tr, wd,
% ht and dp.  These represent the dimensions of a label which will
% later on be put down by TeX, for example
%
%    hboxbl3 --- the bottom left coordinate of the third label,
%    hboxr7  --- the right-hand baseline of the seventh label,
%    hboxht9 --- the height of the ninth label,
%
% and so on.  You can then specify the contents of a label by saying
%
%    setbox NUMBER "SOME", "TEX", "CODE";
%
% for example
%
%    setbox3 "Fred";
%    setbox7 "$\begin{array}{c}",
%            "a\\b\\c",
%            "\end{array}$";
%
% the comma-separated version is useful for labels more than one line
% long.
%
% NB: Because of the way diagrams are implemented in LaTeX, it's a
% {\em very bad idea\/} for labels to contain \diagramfile's.
%
% Your TeX file then says
%
%    \diagramfile{FILENAME}
%    \diagramf{NUMBER}
%
% where FILENAME is the name of the mf file, and NUMBER is the diagram
% number.  It's a good idea not to have too many diagrams per file
% (like more than about 50 or so) because TeX has to use up one box per
% diagram.
%
% This all works by providing an interface between TeX and MF... MF
% reads in a file JOBNAME.dim containing the dimensions of the TeX
% labels and writes out a file JOBNAME.dia containing the TeX labels
% and where they should be positioned.  TeX then reads in the .dia
% file and writes the .dim file.
%
% So the production cycle for a document containing diagrams is
%
%    1) Create an empty .dim file (because bloody MF can't tell
%       whether a file exists or not grumble grumble grumble...)
%    2) Run MF to create the .dia file containing the labels,
%    3) Run TeX to set the labels and find their dimensions,
%    4) Run MF to create the final version of the diagram, now that we
%       know what size the labels are, and
%    5) Run TeX to produce the document.
%
% A sample .dim file is
%
%    wd#[2][0] := 20.3344pt#;
%    ht#[2][0] := 6.94444pt#;
%    dp#[2][0] := 1.94444pt#;
%
% which defines the size of the zeroth label of the second
% diagram---it's width is 20.3344pt, height 6.94444pt and depth
% 1.94444pt.
%
% A sample .dia file is (almost)
%
%    \newdiagramfont{example}
%    \newdiagram{2}
%    \diagramlabel{0}{4.88908pt}{0pt}
%    $g \circ h$
%    \enddiagramlabel
%    \diagramchar{2}
%    \endnewdiagram
%
% (The `almost' is because actually all the lines end with the comment
% `% diagramf' to flag them.)
%
% This means that the diagram font is called
% example, and diagram 2 contains label 0 at coordiates
% (4.88908pt,0pt) which consists of the text $g \circ h$.
%
% That's enough interfaces, Ed.
%
% To begin with, we need to declare the variables used in the .dim
% file.

numeric wd#[][], ht#[][], dp#[][];

% Then we input the .dim file.

scantokens ("input " & jobname & ".dim");

% Right, now we define the macros for writing the .dia file.  Metafont
% contains no (count 'em---none) primitives for file handling, except
% for writing information out on the .log file.  So we'll write the
% .dia file to the .log file with tags saying `% diagramf'.  You can then
% use an incantation like
%
%    grep "% diagramf" blah.log > blah.dia
%
% to recover the .dia file.  This is a right pain!  But there's no
% other real way to do it---see Section 7 of Appendix D of the MFbook
% for a similar hack by DEK.
%
% So to produce the TeX output
%
%    blah% diagramf
%    waffle% diagramf
%
% you say
%
%    texoutput "blah", "waffle";
%
% which just produces the right messages.

def texoutput text t =
    for s = t: message s & "% diagramf"; endfor
    message ""
enddef;

% So to begin with, we'll produce a header message which contains the
% filename, the date, and the name of the font we're producing.

string monthname[];
monthname[1]  = "Jan"; monthname[2]  = "Feb"; monthname[3]  = "Mar";
monthname[4]  = "Apr"; monthname[5]  = "May"; monthname[6]  = "Jun";
monthname[7]  = "Jul"; monthname[8]  = "Aug"; monthname[9]  = "Sep";
monthname[10] = "Oct"; monthname[11] = "Nov"; monthname[12] = "Dec";

string today;
today = decimal day & " " & monthname[month] & " " & decimal year;

texoutput "% Filename: " & jobname & ".dia ",
          "% Generated by: diagramf.mf ",
          "% Date: " & today & " ",
          "\newdiagramfont{" & jobname & "}";

% To convert a coordinate (36pt,5.2pt) into a string "{36pt}{5.2pt}"
% you use coordinate:

def coordinate expr z =
    "{" & decimal (xpart z/hppp) & "pt}{" & decimal (ypart z/hppp) & "pt}"
enddef;

% We can now define the macros used in preparing diagrams.  To begin
% with, begindiagram... enddiagram.
%
% This sets variables
%
%    diagram --- the number of the diagram,
%    character --- the number of the character produced (at the moment
%       this is just the same as the diagram number, but this may
%       change soon...)
%    hboxwd[], hboxht[], hboxdp[] --- the dimensions of the box, and
%    hboxl[] --- the left end of the box.
%
% It also produces the output \newdiagram{DIAGRAM} and does a
% beginchar.
%
% We read in the dimensions of the character as a text parameter to
% make sure they aren't evaluated until {\em after\/} diagram has been
% set.  This means you can use hboxwd#, hboxht# and hboxdp# in a
% begindiagram and all will be well.

def begindiagram (expr n) (text t) =
    begingroup;
       diagram:=n;
       character:=n;
       numeric hboxwd[], hboxht[], hboxdp[];
       pair hboxl[];
       texoutput "\newdiagram{" & decimal diagram & "}";
       beginchar (character) (t)
enddef;

% enddiagram just closes down all the groups and outputs the
% \diagramchar and \endnewdiagram TeX macros.

def enddiagram =
       endchar;
       texoutput "\diagramchar{" & decimal character & "}";
       texoutput "\endnewdiagram";
    endgroup
enddef;

% Then the other coordinates of the box are vardefs based on hboxl@#,

vardef hboxtl@# = hboxl@# + (0, hboxht@#) enddef;
vardef hboxtr@# = hboxl@# + (hboxwd@#, hboxht@#) enddef;
vardef hboxr@#  = hboxl@# + (hboxwd@#, 0) enddef;
vardef hboxbr@# = hboxl@# + (hboxwd@#, -hboxdp@#) enddef;
vardef hboxbl@# = hboxl@# + (0, -hboxdp@#) enddef;

% and the sharp dimensions of the boxes.

vardef hboxwd#.@# =
    if unknown wd#[diagram]@#: eps
    else: wd#[diagram]@#
    fi
enddef;

vardef hboxht#.@# =
    if unknown ht#[diagram]@#: eps
    else: ht#[diagram]@#
    fi
enddef;

vardef hboxdp#.@# =
    if unknown dp#[diagram]@#: eps
    else: dp#[diagram]@#
    fi
enddef;

% Then hboxes (sigma) sets the constraints on all the hboxes from
% sigma.  For example, hboxes (1,2,3) sets up hbox1, hbox2 and hbox3.

def hboxes (text t) =
    for n = t:
        hboxwd[n] = hboxwd#[n] * hppp;
        hboxht[n] = hboxht#[n] * hppp;
        hboxdp[n] = hboxdp#[n] * hppp;
    endfor
enddef;

% We can then set a box by outputting the TeX code for it.  If
% proofing is set, we draw a box to show where the label goes.

vardef setbox@# text t =
    texoutput "\diagramlabel{" & decimal @# & "}" & coordinate hboxl@#,
              t,
              "\enddiagramlabel";
    if proofing=2: prooflabel@# fi
enddef;

% If we're in a proofing mode, we'll draw the label with a .25pt
% pen.

vardef prooflabel@# =
    begingroup;
       localpen;
       pickup pencircle scaled .25pt;
       draw hboxbl@# -- hboxtl@# -- hboxtr@# -- hboxbr@# -- cycle;
       draw hboxl@# -- hboxr@#;
    endgroup
enddef;

% Where localpen provides local variables for all the pen values.

def localpen =
    interim pen_lft:=0;
    interim pen_rt:=0;
    interim pen_top:=0;
    interim pen_bot:=0;
    if known currentbreadth: interim currentbreadth:=0; fi
    save currentpen, currentpen_path;
    pen currentpen;
    path currentpen_path;
enddef;