Special Fonts

We propose the use of a special pseudofont as an enhancement (in a sense) of the \special instruction. The examples of the implementation show that the technique applied here would prove to be extremely useful, especially with METAPOST. keywords: cmdfont, special commands, MetaPost, fonts, PostScript Keen users of TEX, METAFONT, or METAPOST might find the instructions called “special” very mighty helpers. However, METAPOST imposes serious limit on them: their content is placed at the very beginning of a PostScript file that METAPOST produces, just after the %%Page comment, before the very first real PostScript statement. It means that METAPOST, unlike TEX and METAFONT, is not able to intersperse drawing commands (draw, fill) or typesetting commands (infont, btex ... etex) with a special user-defined content. This behaviour embitters the life of METAPOST users and leads to neck-breaking solutions. Even worse, TEX \special instructions are ignored by dvitomp, making oodles of TEX packages unusable inside a btex ... etex construct. The solution is to replace each \special instruction with a string typeset with a special-ly crafted font (pseudofont). We propose a natural name for it: cmdfont, command font. The text typeset with cmdfont has a special meaning when a TEXgenerated dvi or a METAPOST-generated eps file is processed—it is treated as a sequence of commands to be interpreted. The current article is the result of very preliminary thoughts—the idea is still very fresh. We are far from understanding all the consequences of this approach. Therefore, instead of developing a “general theory of specials,” we decided to present just a few examples illustrating various possible applications of special \special instructions. We have concentrated on using cmdfont with METAPOST. The use of pseudofonts with TEX, METAFONT, html or even major office editors is another thing. The reader may wish to evaluate the possibilities of special fonts. We perceive them as quite promising. ∗[email protected] †Polish Linux Users’ Group, [email protected] 96 b. jackowski and k. leszczyński What is the special font? Our special font can be defined with a short METAPOST program, cmdfont.mp: designsize:=10bp/pt epsilon; fontdimen 2: designsize; % font normal space fontmaking:=1; for i:=0 upto 255: beginfig(i-256); charwd:=charht:=chardp:=charic:=0; endfig; endfor end. The result of interpreting this program by METAPOST is cmdfont.tfm, i.e., a metric file which should be put somewhere where all tfm files reside. It contains 256 characters with all dimensions equal to zero. Most other font parameters are also set to zero. It is obvious that the font design size cannot be zero, but it is not obvious why the width of a space (fontdimen2) should be set to the design size. In fact, the actual size is not essential, any non-zero will do. Also, the actual design size value is not important as long as everybody who uses cmdfont takes the same designsize value. Please note that the beginfig parameter is negative. Negative arguments instruct the METAPOST interpreter to output all the eps files under the same name: cmdfont.ps. If we used a seemingly natural form, beginfig(i), our directory would be infested by cmdfont.0, cmdfont.1, . . . , cmdfont.255 files. We don’t need those files and it is easier to throw away one file than 256 files. Special font in a METAPOST program Let’s trace how the instructions referring to cmdfont are parsed by METAPOST. Consider the file named, say, infont.mp: beginfig(100); draw "META FONT" infont "cmdfont"; draw "META POST" infont "cmdfont" scaled 2; endfig; end. The resulting file, infont.100, reads: 1 %!PS 2 %%BoundingBox: 0 0 0 0 3 %%Creator: MetaPost 4 %%CreationDate: 2001.04.13:1950 5 %%Pages: 1 6 %*Font: cmdfont 10 10 20:80000000460708 7 %*Font: cmdfont 20 10 20:80000000440598 8 %%EndProlog