#Ligatures fontforge how to
#Ligatures fontforge software
#Ligatures fontforge professional

Instead, what you want to edit is a format called a 'feature file.' Feature files are a human-readable representation, at a higher level of abstraction than the substitution table entries. The glyph substitution tables in their native format are effectively impossible (at the very least, painful) to understand. Other GUI font editors probably do as well.įorget that. FontForge allows you to edit the glyph substitution tables directly in its GUI.

#Ligatures fontforge software

I believe that in a mathematical sense they are equivalent to a finite state transducer's state-transition tables, in that we could write a piece of software to convert between the two in either direction. The font stores its glyph substitution program internally in a set of 'tables.' These are similar but not identical to the state transition tables of a finite state transducer, if you know what one of those is. So even if I were capable of understanding all the details, I couldn't, because the information just was not there. All the instructional materials I could find on the Net attempted to simplify the language by giving a bunch of examples but not actually specifying the exact behaviour of the system.

I myself have a PhD in computer science and am currently employed doing research in declarative programming languages specifically, dammit, and it still took me all night.

#Ligatures fontforge professional

It's quite different from the imperative languages more commonly used for computer programming, so even if you happen to be a professional computer programmer, you will probably find it very difficult to understand. Font designers often are not trained as computer programmers at all, and to make matters worse, the OpenType glyph substitution language is declarative and weird. The designer of a font is faced with the task of writing the substitution program. When you typeset with an OpenType font, your software (word processor, typesetting, even potentially the printer firmware, maybe) is supposed to interpret the substitution program and use that to determine what glyphs should be set. These programs are written in a declarative language designed for the purpose, and they can be edited with font-editing software. Each OpenType font includes a computer program that explains what replacements to perform. What replacements must be performed, depend on the font. (Note that that isn't the standard name for that particular ligature glyph - this is only an example of the need for replacement, and the standard name of 'f_f_l' would be less clear.) So the input stream of symbols 'a f f l i c t e d' must be converted into a new stream that might look like 'a FFL.ligature i c t e d' - that is seven symbols - where 'FFL.ligature' is the name of the special replacement glyph. For instance, in traditional English-language typesetting the sequence of symbols 'f f l' is usually replaced by a single glyph called a 'ligature,' which combines the three letters into a shape that looks nicer than just setting them separately side by side. However, in some fonts, to make it look right on the page, there need to be translations applied. Usually, each of the intangible symbols in the text corresponds to a tangible symbol called a glyph, which is a pattern of ink on the printed page. For instance, to typeset the word 'afflicted' your stream of symbols might be 'a f f l i c t e d' that is nine symbols. By 'font' I mean the computer program that lives in an OpenType font file (usual extension '.otf') that may in some cases correspond to what traditionalists would call a 'typeface.' Your text consists of a stream of symbols (in the computer-science sense).

The situation is that you're going to typeset text using a font. I'll be using the terms that make sense to me, rather than the 'easy' but uselessly vague simplified style used by all existing documentation I found.

There is one important point I call the Terrible Secret, which makes all the difference to getting it to work but rather than jump to that immediately I'm going to give the needed background first.

The purpose of this entry is to provide the important information that I wasn't able to find on the Net and wish I had had. What is unusual, though, is that I not only succeeded, but also figured out the undocumented underlying principle so that I can predictably succeed in the future as far as I can tell, the more usual practice is to just try things at random until one eventually either gets it working by accident, or gives up, without having learned anything useful either way. Anyone who has tried to write substitution rules for OpenType fonts has probably gone through something similar.

#Ligatures fontforge how to

I was up until 3 this morning trying to figure out how to make OpenType glyph substitution work. Tags used: programming, software, typography The Terrible Secret of OpenType Glyph Substitution « Animated romance day | Home | Electric kerning »