Issues with using GPOS for stylistic set features?

John Hudson
John Hudson Posts: 3,230
edited May 2017 in Font Technology
Has anyone run into any software issues with using GPOS rather than GSUB in stylistic set <ssXX> features? In theory, there should be no issues, but, well, you know....

The context I'm looking at is using a stylistic set feature to implement a specific style of spacing.

Comments

  • Mike Wenzloff
    Mike Wenzloff Posts: 106
    Using a pair adjustment inside a stylistic set works in Word (Windows at least), ID, QXP, Affinity Designer, and everything else I tried that can see pair adjustments. It merely overrides the kern feature for the selected text.

    There are several applications that I use form time to time I didn't try, like LO's Writer for instance.

    WOFF format also works in the browsers I have tried in the past.

    Mike
  • John Hudson
    John Hudson Posts: 3,230
    Thanks, Mike. In this case, I'll be using GPOS single adjustments involving both dx position adjustments and width adjustments.

    It merely overrides the kern feature for the selected text.
    Overrides, or is additive? In my experience, GPOS adjustments are applied additively.
  • Kent Lew
    Kent Lew Posts: 944
    I should think additional GPOS would be additive with kerning. That’s been my experience. (And how the spec reads.)

    I've run into bugs with dy adjustments, but I don’t think I’ve seen any dx or advance width bugs. Haven’t done this often nor tested widely, however.
  • Mike Wenzloff
    Mike Wenzloff Posts: 106
    Oops, yep, additive. I didn't have enough differences to see the differences.
  • Georg Seifert
    Georg Seifert Posts: 674
    One problem with moving glyphs vertically (like shifting up parentheses in the 'case' feature) is that it shifts the underline in Indesign, too. 
  • Adam Twardoch
    Adam Twardoch Posts: 515
    John,

    https://sites.google.com/a/twardoch.com/typography/font-tech/gpos-stylistic-sets
  • John Hudson
    John Hudson Posts: 3,230
    Thanks, Adam.

    I wouldn't be doing any vertical GPOS adjustments of base glyphs in what I have in mind.
  • Adam Twardoch
    Adam Twardoch Posts: 515
    edited May 2017
    Back when I tested this, Uniscribe in Word for Mac completely ignored GPOS ssXX (i.e. expected ssXX only in GSUB). I wrote about this to the OT list but there was no response, so I let it be. Could you check how my font (you can download it there) works in DirectWrite/Word 2016/Edge? I currently don't have a Windows installation handy.
  • John Hudson
    John Hudson Posts: 3,230
    Back when I tested this, Uniscribe in Word for Mac completely ignored GPOS ssXX
    So far as I'm aware, Mac Office does not use Uniscribe. Recent versions of Mac Word seem to do some GSUB, and to get some shaping for complex scripts, but still have trouble with GPOS. I've no idea how they're doing this.

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