OTF feature

[Guest]

I am designing an Armenian OT font in FontLab, and I want to add some features. I did most of the usual features like liga, clig, ordn, etc. but I am having problems with vkrn.

I want to raise the marks when they are over capitals. When I use vkrn, the OT preview panel raises the mark and all subsequent glyphs. Plus, when I generate the font and install it, all other features work but the vkrn does not.

Is there any way to make this work? Maybe something other than vkrn would be better.

[John_Nolan-ylAnVM]

My understanding is that vkrn is for vertical scripts, like Chinese. Have you tried using the case feature? You would create separate, raised marks to be used for capitals, and implement them with the case feature. I _think_ that's how it works.

[Guest]

John, that would a good method if all I wanted was two positions for the mark, one for lowercase the other for uppercase. But what I need is fine-tuning of the mark above each glyph. Some lowercase glyphs extend above the x-hight so I need to raise the mark to keep enough space between the mark and the glyph. I mentioned capital letters because all of them need raised marks, but there are also lowercase letters.

[John_Nolan-ylAnVM]

You might try posting this on the forums at Typophile.com. There's some knowledge of Armenian there.

[_Read_Roberts_]

The Adobe FDK and features file format do not support what you want.

The OpenType font format does allow what you want to do, which is a a pair positioning statement to adjust the placement of the accent glyph up or down, and then also specify that the y-advance of the accent glyph be adjusted to counteract the placement shift so as to leave the current drawing point on the base-line. You should look at the Mcirosoft VOLT tool, which I hope does allow this kind of adjustment.

The Adobe FDK feature file does specify the necessary syntax (see "Pair Pos format A") but it is not yet implemented. This is supposed to happen in FDK 2.0, currently scheduled for summer 2006.

[Guest]

Thanks Read, but the problem is that VOLT works with TT flavored fonts and I am exporting PS flavored.

I know there is a method to use VOLT for OTF CFF, but the questions now is: is that method efficient or is hand coding faster and easier?

[_Read_Roberts_]

To work with Volt and CFF fonts:
- build the PS font in FontLab. Make sure you can build an OTF font without the glyph order changing;The OTF-building process will force the glyphs with Adobe standard names into a standard order. The easiest way to avoid glyph order changes may be to save the OTF font, and then re-import it.
- use FontLab to convert the font to TrueType, and save it as a TT font
- use VOLT to build all the featurs for this font
- use the OTFTableEditor tool to copy the GSUB and GPOS tables from the TTF font to the OTF font. Note that these tables reference the glyph by glyph index. This is why it is important that the glyph order in the TTF font be exactly the same as in the OTF font.

This is all prety clunky, but I don't know a better way. I would be very interested to know how to hand-code GSUB/GPOS features.

[Guest]

Thanks Read.

I tried VOLT, it is a bit complicated and I would need to work on two different machines, after I buy the PC. I know hand-coding seems much more complicated and you don't see the results as you work, but once you get everything setup it is as fast as copy/paste/type.

There is a program that converts the font TT or CFF to XML and back, it is called TTX you can find it at http://www.letterror.com/code/ttx/

I will need to spend some time learning the syntax and all, but I believe I can do it.