Confusion with Fonts

[PeterT]

I'm a tad confised here on the usage of the Kobo Font preferences menu.

I have Atkinson Hyperlegible Next set as my font face, and Charis as the supplemental. Using EPUB Font Tester v3.0g I see the missing symbol indicator in variois places (for instance the 3rd, 7th and 8th symbol in the Macron listing).

If I change the font selection to Charis I correctly regardless of the setting for supplemental font, I see symbols in those positions.

I *thought* that the idea of the supplemental font was to use that for characters that do not exist in the main font.

Can anyone explain this for me?

[Quoth]

Does the supplementary font thing work other than in kepub format ebooks?

I've only used epub, not kepub, for years.

[Aleron Ives]

IIRC the supplemental font option only works with KEPUB.

[PeterT]

I failed to mention that it IS in kepub format.

[DNSB]

I've noticed that the missing font replacement seems to be a bit odd at times. Just for coverage, I set Arial Unicode MS as the font and Code2000 as the supplementary font. When if I opened the Hindi, Arabic and Hebrew pages, Noto Serif Devanagari, Noto Sans Arabic and Noto Serif Hebrew were downloaded and set as supplementary fonts.

[fogice]

I was communicating with Kobo about a similar issue recently; for me, it was the "thin space" character, which is used in some books between a single and double quote mark in a nested quotation. I found that the thin space character was present in the built in font Rakuten Serif, but not in Kobo Nickel. If I set RS as primary and KN as secondary, it displayed correctly. However, if I set KN as primary and RS as secondary, I get a box symbol instead.

Here was the conclusion to my chat:

The “Supplemental font” is meant to provide glyph fallback when your chosen font doesn’t include certain characters (for example, mixing Latin text with occasional CJK or symbols). In the current firmware, however, that fallback doesn’t consistently apply to certain Unicode space characters like THIN SPACE (U+2009). Those spaces are handled differently by the layout engine, so when the primary font lacks the glyph, the device can show a missing‑glyph box instead of drawing it from the supplemental font. That’s why Nickel as primary + Rakuten Serif as supplemental still shows the box.

It is not a bug but its something definitely we can take feedback to improve in the future,

I don't know which characters you were missing, but maybe they fall into the same hole.

[Quoth]

French needs a thin space for inside « and », which is their quotes.

I'd call it a bug to not properly do thin space all the time on any setting, epub or kepub. Also they are based in Canada, where you have to support French and English, though I've no idea how different Canadian French is from French French, or how the Canadian "language laws" work.

[JSWolf]

Originally Posted by PeterT

I'm a tad confised here on the usage of the Kobo Font preferences menu.

I have Atkinson Hyperlegible Next set as my font face, and Charis as the supplemental. Using EPUB Font Tester v3.0g I see the missing symbol indicator in variois places (for instance the 3rd, 7th and 8th symbol in the Macron listing).

If I change the font selection to Charis I correctly regardless of the setting for supplemental font, I see symbols in those positions.

I *thought* that the idea of the supplemental font was to use that for characters that do not exist in the main font.

Can anyone explain this for me?

Give ChareInk7SP a go. It's even better then the version 6 of Charis. Smaller space/NBSP and smaller line height. You can still increase the line height if you desire. Plus is has Kerning and hinting (from the author(s)).

[PeterT]

Jon; I'm fully aware of the your Chare fonts. My goal here was to make use of the increased legibility fonts created by the Braille institute, and I'd just wanted to see what there symbol coverage was like.

[JSWolf]

Originally Posted by PeterT

Jon; I'm fully aware of the your Chare fonts. My goal here was to make use of the increased legibility fonts created by the Braille institute, and I'd just wanted to see what there symbol coverage was like.

What you could try is to take the fonts you want as your main font and using a font editor, delete the characters that don't work and then see what happens. I don't know if this will work or not. But you could give it a try.

[PeterT]

I don't see the need. This was just a "Hmm... I wonder" type thing; and rest assured that both DNSB and I have raised questions with Kobo on how Alternative Fonts work.

[JSWolf]

Originally Posted by PeterT

I don't see the need. This was just a "Hmm... I wonder" type thing; and rest assured that both DNSB and I have raised questions with Kobo on how Alternative Fonts work.

I did a quick test and deleted the notdef character in case that was the problem. Didn't work.