A long reply from Beat...
My apologies if I happened to be too technical. The problem is, though, that this area of TrueType is probably the most technical, but I’ll try. If anybody in the community happens to have a simpler explanation, or a more typographic explanation, please feel free to chime in.
First, the good news is that as of VTT 4.2 there is no more need to manually edit the "Pre-Program" ("prep" for short). It is indeed generated automatically when you compile the "Control Program." I always felt that having to edit the prep was too technical, and it unnecessarily complicated the problem. This would answer questions 5 and 6.
The updated template files should have come with VTT 4.2. The control program template (CvtTmpl.TXT) is a plain text file. To double check whether you have the right one, open it up; the first couple of lines should say something like
/*****
Visual TrueType 4.2 Control Program
The new control program allows…
If you don’t have it, Simon Daniels will be happy to help you. This would answer question 4. The template gives a lot of comments, but is mostly geared towards users of previous versions of VTT, having a fairly good understanding of TrueType and how the business with CVTs and "inheritance" works. Therefore it focuses how this works with 4.2, how this (hopefully) simplifies work, and what kind of features it adds.
So I’ll try a more 'hands-on’ explanation of how things are done in TrueType. Let’s assume we’re doing a link across a stem, and for the sake of the argument, lets assume this link is from point #1 to point #2 in x-(or horizontal) direction (normally, with the visual interface, you wouldn’t worry about point numbers, but it’s hard to write about things if we cannot point at what we mean). Essentially, this link will bring both edges of the stem to the nearest pixel boundary (or gridline). In detail, it will do the following. I’ll assume that we’re looking at the problem at some type size and resolution, say 12 pt and 96 dpi (or 16 pixels-per-em for short, written as 16 ppem). You can "throw" VTT into "ppem mode" by turning on "Pixels" and "Grid-fitting" in the Display options (keyboard short-cuts are Ctrl+B and Ctrl+G respectively):
· Measure the distance between points #1 and #2. This may be some fractional value, say 1.6 pixels.
