[Freetengwar] Telcontar Feature IDs

[<j_m...@sh...>]

Hi all

I think I finally figured out what IDs work in which
applications. Took me long enough.


Graphite Compiler
-----------------

The Graphite Compiler will accept integers or strings of up
to four characters. The following are valid examples:

id=203; #This is an integer.
id=99203 #This is another integer.
id="203"; #This is a string.
id="gr03"; #This is another string.

Invalid:

id=g203; #This should be an integer.
id="gr203"; #This string is too long.


Firefox
-------

Firefox accepts only strings, not integers. If a string has
less than four characters, additional spaces have to be
added after the string name:

font-feature-settings: "203 " 2;
font-feature-settings: "gr03" 2;

Without the additional spaces, a string of less than four
characters will not work:

font-feature-settings: "203" 2;


LibreOffice 5.3
---------------

Like Firefox, LibreOffice 5.3 accepts only strings, not
integers. Unlike Firefox, it easily accepts strings of less
than four characters:

Tengwar Telcontar:203=2
Tengwar Telcontar:gr03=2


Linux LibreOffice 5.2
---------------------

LibreOffice in Linux up to version 5.2 will accept strings
or integers that have four characters or less. This means
that the following code will work no matter whether _203_
has been built into the font as an integer (id=203;) or as a
string (id="203";):

Tengwar Telcontar:203=2


XeLaTeX
-------

Unlike Firefox and LibreOffice, XeLaTeX does not accept
strings, but only integers:

\font\mytelcontar="Tengwar Telcontar/GR:203=2"
\font\mytelcontar="Tengwar Telcontar/GR:123456203=2"

However, it is the only client application that accepts name
strings:

\font\mytelcontar="Tengwar Telcontar/GR:Decorated Tengwar=All"


Consequences
============

The features in the 0.8 release of Tengwar Telcontar have
integer IDs. They can be selected in XeLaTeX or in
LibreOffice 5.2, but not in Firefox or in LibreOffice 5.3.

We must have features with string IDs. Firefox and
LibreOffice are the two most accessible applications that
support SIL Graphite. What strings to choose?

I think it is not a good idea to reuse the original integers
as numerical strings. That is too confusing.

Choosing strings from the OpenType layout tag registry seems
tempting, but it is probably not a good idea. I think we
better use strings that indicate that these features are SIL
Graphite, not OpenType. Therefore, I think that strings like
"gr00", "gr01", "gr03" etc. would be best. There are no such
strings in the OpenType layout tag registry. The "gr" stands
for Graphite.

For backwards compatibility, we can keep a copy of the
features with the original integer IDs. These copies only
add very little to the size of the resulting fonts. They
will ensure that previous TEX files continue to work.


New Telcontar release
=====================

I think a new release is overdue so the Telcontar features
will work in Firefox and continue to work in LibreOffice.

I am only still beginning to understand the additions to the
Telcontar trunk. As far as I understand now, these are
mainly additional shifted tehtar that are optimized for
specific tengwar widths. Weren't these originally intended
for a potential AAT release? I do not know whether an AAT
release is still worth the effort, now that LibreOffice for
Mac is going to support SIL Graphite.

I see the future of Tengwar Telcontar as follows:

0.8.1
fix feature IDs so the font will work on Firefox and
LibreOffice

0.9
complete missing capital/decorated tengwar

-- 
grüess
mach