mfpic-doc.pdf.

4.7 LABELS AND CAPTIONS. 52
is implemented by an equivalent \tlabel command and is only kept for backward compatibility.
It differs from \tlabel when the optional argument is absent: the default justification is [cc]
regardless of the setting of \tlabeljustify.
\mfpverbtex{〈TEX-cmds〉}
This writes a verbatimtex block to the .mp file. It makes sense only if the mplabels option
is used and so only for METAPOST. The 〈TEX-cmds〉 in the argument are written to the .mp file,
preceded by the METAPOST command verbatimtex and followed by etex. Line breaks within the
〈TEX-cmd〉 are preserved. There is also a linebreak between the end of 〈TEX-cmds〉 and the etex. The
\mfpverbtex command must come before any \tlabel that is to be affected by it. Any settings
common to all mfpic environments should be in a \mfpverbtex command preceding all such
environments.
It may be issued at any point after MFPIC is loaded, and any number of times. If it is issued
after \opengraphsfile, its contents are immediately written to the .mp file. If it is issued before
\opengraphsfile, its contents are saved and written when the file is opened (successive uses being
cummulative). In this case its contents will precede the boilerplate TEX code that MFPIC writes. If
you wish to redefine some of that code, you need to use \mfpverbtex after \opengraphsfile.
Because of the way METAPOST handles verbatimtex material, the effects cannot be constrained
by any grouping unless one places TEX grouping commands within 〈TEX-cmds〉. However,
MFPIC itself places grouping commands into the output file at the beginning and end of each picture,
so definitions written by a \mfpverbtex are local to any picture in which it occurs. Prior to version
0.8, MFPIC did not write comments that occured within the 〈TEX-cmds〉. Now they will be preserved,
and can be used to place the ‘%&latex’ line that some TEX distributions permit as a signal that latex
should be run to produce the labels.
This command attempts a near-verbatim writing of the 〈TEX-cmds〉 and, as with all verbatim-like
commands, it should not be used in the argument of another command.
\startbacktext . . . \stopbacktext
When TEX adds labels (\nomplabels) they have to be positioned either on top of a complete
figure, or placed under a complete figure. The most reasonable choice (and happily the easiest to
implement) is to put them on top. When METAPOST is placing labels (option mplabel) the same
can be forced with the option overlaylabels, but otherwise they are placed as they occur, with later
drawing commands perhaps putting their results on top of the labels or clipping parts of them off.
Sometimes it is useful to place some label as a background (not on top), and yet not have it
clipped by later commands. The effect of the command \startbacktext is that \tlabel commands
are saved in a special place until the command \stopbacktext. Then, at \endmfpic the
rest of the figure is simply place on top of them. Since labels in METAPOST files can only consist
of characters from some font, if one wants to include a graphic in the background (for example, via
\includegraphics), one needs to switch off mplabels:
\nomplabels
\startbacktext
\tlabel[cc](0,0){\includegraphics{mygraph}}
\stopbacktext
\usemplabels
As with other labels, it is permitted to switch mplabels off and on while creating background text.
If there are both kinds of labels within the background text area the ones handled by TEX will be
further back than the ones handled by METAPOST. Within a given type, earlier ones are further back
than later ones.