Re: [Fontforge-users] how to use substitutions in opentype

[George W. <gw...@si...>]

On Sun, 2005-03-20 at 08:29, Grim S wrote:
> I am trying to create and opentype font with
> substitutions and ligatures. I understand that the
> 'Glyph Info' dialog has three tabs for handling this -
> 'Subs', 'Alt Subs' and 'Mult Subs'. In the case of
> 'Mult Subs', how do I determine what tag i should put?
Well it depends on what your substitution does. The tags have meanings
that are defined in the opentype standard.
   http://partners.adobe.com/public/developer/opentype/index_tag3.html
Generally it is better to think of the feature you are providing (the
tag) as determining the substitution type rather than the other way
round.

Multiple substitutions are not very common, are you sure that's what you
want to use?

Of course you can also create your own tags, but no word processor will
use them.

A description of the dialog is found at
	http://fontforge.sourceforge.net/charinfo.html

Examples may be found at:
	http://fontforge.sourceforge.net/editexample6.html#Variants
or on Page 10 of
	http://fontforge.sf.net/fontforge-tutorial.pdf

> Is there any place where I can find the various
> options and how to use them? 
A description of these options may be found at:
	http://fontforge.sourceforge.net/charinfo.html#Feature-Tag
   As I see it there are 4 options:
	Components of the substitution
	   Presumably this one is obvious. These are the names of the
	   glyphs you want to substitute for the current one
	Tag
	   The feature tag tells opentype engines (like Uniscribe and
	   pango) when the substitution is to happen.
	Script & Language
	   Generally this will be given a reasonable default value. And
	   you won't really need to worry about it. It determines for
	   what scripts (and for what languages within those scripts)
	   the feature will be active.
	Flags
	   Again these will be defaulted. In a latin font you probably
	   won't need any of them.
> Is it defined in the opentype font standard? 
Obviously.
http://partners.adobe.com/public/developer/opentype/index_table_formats1.html

> I would be thankful if you could provide more details
> of how one can fill in these to get
> alternate/multiple/contextual substitutions working.
That's an extremely broad question. As I've already pointed out I've
written pages of documentation on this subject. I suggest you read my
docs. And Adobe's docs.

The Glyph Info dialog is not directly related to contextual
substitutions (it is indirectly). Contextual substitutions are defined
with Element->Font Info.

An example of creating a contextual substitution is given in:
	http://fontforge.sourceforge.net/contextchain.html
or in
	http://fontforge.sf.net/fontforge-tutorial.pdf