S.P.Q.Rahtz@ecs.soton.ac.uk (Sebastian Rahtz) (10/14/90)
I asked recently whether anyone could see a reason why virtual fonts could not be used to simulate the invisible fonts used in SLiTeX (presumably they have other applications too). The argument was that one would simply take any .pl file, extract the character widths, and rewrite the information as a virtual font (.vpl format) with each character simply mapping to a MOVERIGHT of the character width. Since no-one directly contradicted me, I conducted a brief test, and can confirm that the concept does seem to work. I expect there are complicated things I know not wot of. My personal use for this facility is pretty minimal, since a) I have never used overlays in SLiTeX, and b) it is easier for me with a PostScript printer to get invisibility by setting the characters in white. In addition, I have some doubts about this being the correct approach, since it means loading a complete new set of fonts into TeX, thereby taking up memory, when the information is simply a duplicate of what we have already loaded for visible fonts. And lastly, it relies on the use of virtual fonts, and I only know of two drivers (dvips and the emTeX dvidrv family) which support these as yet. Luckily they are both excellent products! But if anyone is interested, they are welcome to my quick hack; the bad news is that its just a program I wrote in Icon. None of this WEB or C stuff for us impatient people! The procedure is essentially trivial, so you can write it for yourself in some more portable form. A real version would no doubt read .tfm and write .vf and .tfm format. Sebastian Rahtz