On the left is an example master page from Font Info on my main .glyphspackage file. Ascender height is 732 for all masters.
On the right is the Font Info from an .otf generated from the main file. Why is the ascender height blown up (and its zone collapsed)?
EDITED TO ADD: Now I see where that ascender (and descender) number is coming from: the ascender or descender vertical metrics numbers set by custom parameters. But is that correct?
I used the Vertical Metrics Manager script to set the parameters for the whole family.
There are several field for vertical metrics in the font. They are used to define line spacing. But are not describing the actual metrics of the outlines. It has to be domes like this because if the way different software using those values differently.
On import Glyphs picks the values that are most likely the best fit.
Yes, a one-to-one roundtrip conversion cannot be expected. The values you add in Font Info are supposed to relate to your design; whereas the derived OS/2 and hhea values have other purposes. The latter are the only values that survive in an OpenType font.
Okay, thanks for the clarification. Does the overshoot suppression triggered by the ascender/descender alignment zones get built into the exported font before those metric numbers get reset?
