Do the Kobo firmwares support ligatures?

[Jellby]

I was wondering if the Kobo rendering engine supports font ligatures. And by support I mean that if the source text contains just the normal individual characters but a font contains proper ligature definitions, the ligature is displayed. Like this (http://www.impallari.com/lobster/):



where the text is simply "venezuela fixture exitoso". The bottom row shows the ligatures for "ez", "fix", "ex", "os" (it also shows terminal letters, but that's a different feature).

[DNSB]

Originally Posted by Jellby

I was wondering if the Kobo rendering engine supports font ligatures. And by support I mean that if the source text contains just the normal individual characters but a font contains proper ligature definitions, the ligature is displayed. Like this (http://www.impallari.com/lobster/):

where the text is simply "venezuela fixture exitoso". The bottom row shows the ligatures for "ez", "fix", "ex", "os" (it also shows terminal letters, but that's a different feature).

Not sure if I would call those ligatures other than the fi pair. To me, they look more like kerning. However, the Kobo ereaders have some kerning support if the font supports it. Some fonts have excellent kerning support, others have minimal support.

BTW, the link you posted gives me a 404 error unless I manually add the .gif file name to the URL manually.

Regards,
David

[Jellby]

It's true that the "ez" is not a ligature in its original sense, but "ex" and "os" are definitely ligatures. Technically, if "ez" is defined in the font as a single glyph, then it's a ligature too.
Kerning affects only the spacing.

The main point here is that the text contains only "e" and "x", not a special character for the combination "ex". And the font has the information to know that whenever "e" and "x" are together, it shouldn't draw the normal shapes (top line), but instead use a special glyph that contains the "ex" combination.

So, if a book contains the word "office", do the Kobos, with any font, display an "ffi" ligature?

[PeterT]

The link gets messed up due to the ): at the end... Try http://www.impallari.com/lobster/

[DNSB]

Originally Posted by Jellby

It's true that the "ez" is not a ligature in its original sense, but "ex" and "os" are definitely ligatures. Technically, if "ez" is defined in the font as a single glyph, then it's a ligature too.
Kerning affects only the spacing.

The main point here is that the text contains only "e" and "x", not a special character for the combination "ex". And the font has the information to know that whenever "e" and "x" are together, it shouldn't draw the normal shapes (top line), but instead use a special glyph that contains the "ex" combination.

So, if a book contains the word "office", do the Kobos, with any font, display an "ffi" ligature?

Looking at the Lobster font, those conjoined characters seem to be in the 65537 (0x10001) to 65634 (0x10062) range which would mean that you would need to use that glyph to replace the standard character pair and use the Lobster font to display that character.

I do wonder why they didn't place those characters in the 0xE000 to 0x0F8FF which is the Private Use Area.

With your example of "office", you would need to specify the "ffi' ligature though quite a few fonts come close to the appearance of the ligature using kerning and/or GPOS.

Regards,
David

[Jellby]

Originally Posted by DNSB

With your example of "office", you would need to specify the "ffi' ligature though quite a few fonts come close to the appearance of the ligature using kerning and/or GPOS.

That means it doesn't support ligatures then, at least not in the way I'd like.

[doubleshuffle]

I just did a very quick test and created test files with the three words from the example above: a regular epub, and a kepub. On my Aura HD, the regular epub displays the ligatures correctly, the kepub doesn't.

EDIT: Added a few words. Other ligatures, like ffi, working beautifully in the regular epub. The end letters too. No luck with the kepub.

[Anak]

Originally Posted by doubleshuffle

I just did a very quick test and created test files with the three words from the example above: a regular epub, and a kepub. On my Aura HD, the regular epub displays the ligatures correctly, the kepub doesn't.

EDIT: Added a few words. Other ligatures, like ffi, working beautifully in the regular epub. The end letters too. No luck with the kepub.

Correct, epub does support the use of ligatures, kepub don't.
Ligatures only work, offcourse if the font contains the OpenType typographic features for ligatures.
Note: ligature support for standard Ligatures (liga) only. Other forms of ligatures don't work. E.g. contextual ligatures (clig), discretionary ligatures (dlig).

To force the render engine not to use ligatures add this code to the CSS

adobe-text-layout: optimizeSpeed;

Turn on (which is the default setting; there is no need to add this line of code)

adobe-text-layout:optimizeQuality;

[DNSB]

Originally Posted by Jellby

That means it doesn't support ligatures then, at least not in the way I'd like.

Unfortunately, that mind reading software is still a few years away. There are some ligatures that are more or less standard such as the Æ entity, others can be accessed by using the &#xYYYY; entity where YYYY is a hex number. Then there is the CSS contextual support which makes use of the OpenType calt property. You could try using font-variant-ligatures: contextual which would come the closest to what you appear to want. Again this requires support baked into the font.

Please note that the calt feature is intended for use by script typefaces which are intended to have their glyphs joined. For my part, I find that script typefaces are not enjoyable for reading for any length of time. A short paragraph is about my limit.

You can check the Microsoft tag registry for more on various OpenType features. Check https://www.microsoft.com/typography...eatures_ae.htm for example.

Regards,
David

[Alastair_S]

Originally Posted by Anak

Ligatures only work, of course if the font contains the OpenType typographic features for ligatures.

Is a list of Kobo compatible fonts that contain ligatures available anywhere?

[Jellby]

Originally Posted by DNSB

Unfortunately, that mind reading software is still a few years away. There are some ligatures that are more or less standard such as the Æ entity, others can be accessed by using the &#xYYYY; entity where YYYY is a hex number. Then there is the CSS contextual support which makes use of the OpenType calt property. You could try using font-variant-ligatures: contextual which would come the closest to what you appear to want. Again this requires support baked into the font.

No mind-reading for me. I probably explained myself wrong, or we are talking about different things. What I wish is just support for the "liga" feature of OpenType (of course, support por "dlig", "calt", etc. would be a bonus). Displaying a glyph by using the &#xYYYY; code for it is not "ligature support" in my book.

Sure, it requires support in the font, my question was whether the Kobo can make use of what the font has to offer.

[doubleshuffle]

Originally Posted by Jellby

Sure, it requires support in the font, my question was whether the Kobo can make use of what the font has to offer.

This question has been answered in posts #7 and #8 of this thread...

[Jellby]

Originally Posted by doubleshuffle

This question has been answered in posts #7 and #8 of this thread...

Yes, I saw that, and thank you. This was just post-answer discussion

[doubleshuffle]

Originally Posted by Jellby

Yes, I saw that, and thank you. This was just post-answer discussion

Ah, I see. I'll try to optimize my mind-reading wetware...