[10 mod] Built-in superscript/subscript characters don't match OpenType subs and sups

[Denis Moyogo Jacquerye]

Superscript characters and subscript characters don't match semantically equivalent characters with OpenType 'sups' and 'subs' features.
Shouldn't they be identical. Shouldn't "¹⁹" be the same as "<sups>19</sups>"?

[Matthew Paul Thomas (mpt)]

Denis, thanks for the well-illustrated report -- and sorry for the multi-year delay!

As far as I can tell, when an app is not using the sups/subs tables, the position and size of superscript/subscript characters is up to the app. For example, this screenshot shows the same superscript characters in Firefox (data:text/html;charset=UTF-8,<p style="font-family:Ubuntu;font-size:70;">19¹⁹¹⁹</p>), LibreOffice, and AbiWord. They have different position and size in all three.

So unless there's something I'm missing, this is not a problem in the font itself. If you want a particular app to use sups/subs characters automatically when available, ask the developers of that app. (I doubt they would, though, because for any glyph that wasn't in the table, the app would have to fall back to algorithmic superscript/subscript, and the mixture would look bad.)

[Denis Moyogo Jacquerye (moyogo)]

Hi Matthew. No worries :-).

I shouldn’t have used <sups>19</sups> as it’s too close to the HTML ¹⁹, which is not what I meant.
I meant to say that the glyphs of the characters ¹⁹ U+00B9, U+2079 are at different height than the glyphs of 19 with the OpenType 'sups' feature applied.

<div style="font-family: Ubuntu; font-size: 70;">
<span>19</span>
<span>¹⁹₁₉</span>
<span style="font-feature-settings: 'sups' on; -webkit-font-feature-settings: 'sups' on; -moz-font-feature-settings: 'sups' on">19</span><span style="font-feature-settings: 'subs' on; -webkit-font-feature-settings: 'subs' on; -moz-font-feature-settings: 'subs' on">19</span>
<span>¹⁹₁₉</span>
</div>

As you say, it is expected that the HTML ¹⁹ would look different.

One might consider this a non-issue as both the superscript characters and the superscript OpenType glyphs are probably not going to appear next to each other.

[Paul Sladen (sladen)]

Ah ha! Thank you for that clarification Dennis!

[Kevin Godby (godbyk)]

The Unicode characters align with the numerators and denominators, though (see attached.)