Sigh, I just
had to get to the bottom of it once and for all. Grit your teeth and read on if you're interested ...
Final conclusion:
If you want a sideloaded font to work correctly with
both epub and kepub for all regular/bold/italic/bolditalic sub-families. Do 2 things.
- Using Bookerly as the example, use the suffix naming convention
Bookerly-Regular.ttf (or just Bookerly.ttf)
Bookerly-Italic.ttf
Bookerly-Bold.ttf
Bookerly-BoldItalic.ttf
- If it's faulty, fix the internal Panose Weight metric using some kind of font editor. @Flaviocc provided a link above to my old instructions for how to do it in FontForge
Other findings:
If the font's internal Panose Weight is faulty but it isn't something you're able/prepared to fix then you may still get regular/bold/italic/bolditalic sub-families to work in
either kepub or epub, but not both simultaneously.
- Kepub only: use one of the 3 following suffix naming conventions.
Either (as per Claude_C post)regular: Bookerly-a.ttf
italic: Bookerly-b.ttf
bold: Bookerly-c.ttf
bolditalic: Bookerly-d.ttf
or (ancient Windows convention)regular: Bookerly.ttf
italic: Bookerlyi.ttf
bold: Bookerlyb.ttf
bolditalic: Bookerlyz.ttf
or (as per DNSB post)regular: Bookerly.ttf
italic: Bookerly-i.ttf
bold: Bookerly-b.ttf
bolditalic: Bookerly-z.ttf
- Epub only: use this suffix naming convention
regular: Bookerly-Regular.ttf (or just Bookerly.ttf)
italic: Bookerly-Italic.ttf
bold: Bookerly-Bold.ttf
bolditalic: Bookerly-BoldItalic.ttf
... and finally ...
Whatever method you use, don't forget to reboot the Kobo after updating any sideloaded font files in the
fonts subdirectory.
ETA: All info correct at time of going to press, firmware 4.21.15015. No future performance guarantees
