So far i’ve been setting my projects keeping in mind that:
ascender + absolute value of descender = UPM
The recent Vertical Metrics Tool from Jan Janeček uses the same strategy, and it’s also said on Glyphs Vertical Metrics Tutorial that the span between typoAscender and typoDescender should be as large as the UPM.
I can follow the tutorial but I would like to look at how are those things related, more insightfully.
Are the standard setting for vertical metrics taken into account while exporting if i have custom parameters defined by hand? Or are the standard setting used only inside Glyphs for viewing the metrics box and calculating the line height in edit view?
Would it be ok to have ascender + descender higher or lower than UPM? What would be the reason to do so?