Kerning .isol forms in RTL preview

How would I preview isolated forms in RTL preview? Selecting the isol OT feature does not seem to work. I even tried to explicitly enter only .isol forms in the text field. I am trying to kern my isolated forms for a non-Arabic connected RTL script.

What script are you talking about? And why would you need to kern isolated shapes if the script is connected?

The script is N’ko and it gets used in connected and unconnected forms in different applications.

The only work around I can think of here is to change the suffix of my isolated forms from .isol to something random. This prevents the preview from applying positional forms automatically. I can then get my kerning values in. I suppose I’ll have to manually generate the isol feature and maybe change the production names back to using the .isol suffix.

I disabled the joining of .isol glyphs. This should work for you then.

I added the N’Ko letters to the GlyphData and adjusted some things to make it behave better. Please check the latest cutting edge version. And if you have comments about the name in the database…

Great, thanks! I’ll try it out. Does installing the cutting edge version overwrite the existing version?

As I recall, updating will put the old version in the Trash.

You could also install the version manually. Download it via:
and unzip where you want to be installed, making sure it’s not in the same spot as your current version (or rename the current version, first).

Thanks, Jeff.

@GeorgSeifert I have been playing with the beta version and the disabling the joining of the .isol glyphs is working out well. I have also checked the glyph names in GlyphData and that looks good as well. I do need to scrub through the combining mark definitions in more detail.

I am still encountering an issue though. When I export the fonts the RTL kerning is not being applied correctly when tested InDesign. I have made sure to set classes and kern values up in RTL mode in Glyphs. I have noticed that the kern feature definition in the .otf does not have the same syntax as RTL kerning I get if I run FDK manually with a kern.fea file that I make in FontLab. Are there some extra provisions made for the Arabic that aren’t being applied to Nko.

e.g. Glyphs output

lookup kern {
pos @a-nko.medi @fa-nko.medi -20;
. . .

vs. manual FDK run
lookup kern {
lookupflag IgnoreMarks RightToLeft;
pos @a-nko.medi @fa-nko.medi <-20 0 -20 0>;
. . .

Also, it the auto generated positional form features don’t include “lookupflag IgnoreMarks RightToLeft;” in the definition.


I fixed this.