[Freefont-bugs] Placement of khirik-yud for Yiddish in FreeSans

[Ze'ev Clementson]

Hello,

I have been using the FreeSans font in an application that displays
Yiddish text using Unicode combining characters. In Yiddish, for the
"pasekh tsvey yudn" and "khirik yud" character combinations, the
convention is to "raise" the vowel. This is done for Yiddish only, not
Hebrew. With FreeSans, "pasekh tsvey yudn" is displayed properly;
however, "khirik yud" is not. I looked through the source code of
FreeSans.sfd to try to determine why this was happening and saw that
there was a yodhiriqhebrew ("khirik yud") definition set up; however,
it was not being displayed. The yodyodpatahhebrew ("pasekh tsvey
yudn") definition was being displayed properly so I looked through the
source to see why it was being displayed and the yodhiriqhebrew
combination was not.

First, since "pasekh tsvey yudn" is displaying with a raised vowel, I
looked at the definition for it in the font source:

StartChar: yodyodpatahhebrew
Encoding: 64287 64287 1299
Width: 400
Flags: HMW
LayerCount: 2
Fore
Refer: 853 1463 S 1 0 0 1 -99 280 2
Refer: 2821 1522 S 1 0 0 1 0 0 2
Validated: 32769
Ligature2: "'ccmp' Glyph Composition/Decomposition in Yiddish"
yodyodhebrew patahhebrew
LCarets2: 1 0
Ligature2: "'liga' Standard Ligatures in Hebrew subtable" yodyodhebrew
patahhebrew
EndChar

I noted that the "Ligature2" element has two separate definitions for
ccmp & liga.

Then, I looked for the definition of "khirik yud" in the source:

StartChar: yodhiriqhebrew
Encoding: 64285 64285 1297
Width: 200
Flags: HMW
LayerCount: 2
Fore
Refer: 875 1497 N 1 0 0 1 0 0 2
Refer: 850 1460 N 1 0 0 1 -203 278 2
Validated: 32769
Ligature2: "'ccmp' Glyph Composition/Decomposition in Yiddish"
yodhebrew hiriqhebrew
EndChar

The "Ligature2" element had only one definition for ccmp.

So, I used FontForge to add the Ligature2 liga reference:

StartChar: yodhiriqhebrew
Encoding: 64285 64285 1297
Width: 200
Flags: HMW
LayerCount: 2
Fore
Refer: 875 1497 N 1 0 0 1 0 0 2
Refer: 850 1460 N 1 0 0 1 -203 278 2
Validated: 32769
Ligature2: "'liga' Standard Ligatures in Hebrew subtable" yodhebrew hiriqhebrew
Ligature2: "'ccmp' Glyph Composition/Decomposition in Yiddish"
yodhebrew hiriqhebrew
EndChar

Now, for both "pasekh tsvey yudn" and "khirik yud" combinations, the
vowels are raised. So, for Yiddish-only, this modification works fine
and the mod could potentially be incorporated into the font.
Unfortunately, the vowels are raised regardless of whether I display
Hebrew text (the vowels shouldn't be raised for Hebrew) with an HTML
xml:lang="he" lang="he" or Yiddish text (the vowels should be raised
for Yiddish) with an HTML  xml:lang="yi" lang="yi".

So, my question is: how is it possible to specify that the "pasekh
tsvey yudn" and "khirik yud" combinations will be used with raised
vowels for Yiddish but without raised vowels for Hebrew? Is this a bug
in the font definition or do I need to do something else in my HTML
code to correctly indicate whether the font should use the 'liga'
lookup definitions?

- Ze'ev