Help with UPM and vertical metrics

I’ve been reading up on vertical metrics and UPM settings and want to make sure I’m understanding things correctly:

The context for this is that I changed the UPM of a font from 1000 to 940 (without scaling) to make the size of everything a little larger by default.

A few questions:

  1. Do the ascender and descender metrics always need to match the UPM? I’ve done some testing with them totaling 940 and having them total the original UPM of 1000. At least in Adobe apps, I’m not seeing any differences between those two. What am I missing?

  2. From what I’ve read and as far as I can tell, there doesn’t seem to be any problem with using a UPM other than 1000 besides maybe some older software / systems having a hard time. Are there any other considerations or issues that may come from having a UPM lower than 1000?

  3. I’ve been using @mekkablue 's type metrics manager script (thank you!). Regardless of the adjusted UPM and even after changing asc/descender heights, the suggested vertical metrics, for example the hheAscender and hheaDescender remain at 970 and -290 respectively. Where are those numbers coming from if the highest point in the font as far as I can tell is on the Aring at 884—is this to accommodate Vietnamese diacritics?

Thanks for any insight anyone has—much appreciated!

Please read the Vertical Metrics tutorial. Most of your questions are answered there. Quick version:

  1. No.
  2. No.
  3. Depends on the settings.

Have read but wanted to confirm these things. Thanks for your quick version! :slight_smile:

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