mfpic-doc.pdf.

4.2 COMMON OBJECTS. 13
this command should come before \opengraphsfile, as that command checks for the existence of
the first numbered figure to determine if there are figures to be included.
\everymfpic{〈commands〉}
\everyendmfpic{〈commands〉}
These commands store the 〈commands〉. The first arranges for these commands to be issued
at the start of every mfpic environment and the second arranges for its commands to be issued
at the end of every such environment. These could be any commands that make sense inside that
environment. The purpose of these commands is to save typing if there is identical setup being
performed in every picture.
\begin{mfpic}...\end{mfpic}
In LATEX you may prefer to use \begin{mfpic} and \end{mfpic} (instead of \mfpic and
\endmfpic). This is by no means required. The sample file lapictures.tex provided with MFPIC
illustrates this use of an mfpic environment in LATEX.
One should be careful using TEX groups inside mfpic environments. These can be useful to limit
the scope of declarations or of changes to some variables. However, they do not limit the scope of
changes to the figure file that is being written, so there is a danger that TEX and METAFONT will
have different values. There are also some MFPIC commands that need to be at the outermost level.
Thus, grouping should generally be avoided except for those groups provided by MFPIC commands.
For the remainder of the macros, the numerical parameters are expressed in graph units, the units
of the local coordinate system specified by \mfpic, unless otherwise indicated.
4.2 Common objects.
The MFPIC macros that draw things can be roughly divided into two classes.
1. Those that simply cause something to be drawn. Examples of these are the \point command,
which places a dot at a list of coordinates, and \gridlines, which draw coordinate lines with
specified separation.
2. Those that both define and draw a path. The macros \circle, \rect, and \polyline are
examples of these.
Macros of type 2 are referred to hereafter as figure macros, for lack of a better term. With them
one can use prefix macros to modify various aspects of the path and how it is drawn. For example,
\polyline{(1,2),(3,4)}
draws a line from (1,2) to (3,4), but
\dotted\polyline{(1,2),(3,4)}
produces a dotted version, and
\arrow\polyline{(1,2),(3,4)}
draws it with an arrowhead at the tip. This is not possible with \gridlines, for example. As MFPIC
and the accompanying METAFONT package GRAFBASE are currently written, prefix macros can only
be applied to single paths, and \gridlines produces a whole set of lines. In this manual, as each
macro is introduced, if it is a figure macro, this will be explicitly stated.
Some commands depend on the value of separately defined parameters. all these parameters
are initialized when MFPIC is loaded. In the following descriptions we give the initial value of
all the relevant parameters. MFPIC provides commands to change any of these parameters. When
METAPOST output is selected, figures can be drawn in any color and several of the above mentioned
parameters are colors. For example, drawcolor is the name of the default color used to draw curves,
headcolor is used when drawing arrowheads, etc. To save repetition: all special colors for figures
are initialized to black except background, which is white.