My comment at #145 (comment) details several issues in the vertical metrics of Inter.

This PR solves these, plus another issue I uncovered along the way.

The approach that ended up working well:

• Setting descender, winDescent, hheaDescender, typoDescender all at the same value – a bit past the lowest descender
• Setting ascender, winAscent, hheaAscender, typoAscender all the same – the same amount past cap height that descender values go below baseline
• Add alignment zones at those two values (thanks for the idea, GlyphsApp tutorial!)
• Bit 7 (use typo values) is set to true (not sure how critical this is, but it probably doesn’t hurt, because Google Fonts checks for this)

Results

Text is nicely vertically-aligned in containers:

Default line height is within the range of comparable fonts:

All bounding boxes are consistent height between styles in the variable font:

Caveat

I'm not 100% sure how this will render in Windows. As far as I know, some double-stacking accents will be partially cutoff, some of the time on Windows. It's possible we can fix this by increasing the winAscent value, but I think we should prioritize how this impacts general UI usage above how Windows displays certain accents.

Another issue that this avoids

As I was experimenting, I found that bounding boxes were different, depending on the content of the text (at least in Sketch – I didn't do comprehensive tests). Not good! This was solved by the overshooting ascender & descender values, plus by setting alignment zones at these values.