[Device Plugin] Kobo Touch Extended Driver

[hengyu]

Hi all,

I've noticed that KEPUBs converted by Calibre 8 onwards have badly broken justification (see comparison shot).

I raised a Calibre bug here:
https://bugs.launchpad.net/calibre/+bug/2107778

It was discovered that the output is different apparently in how the spaces are placed in or around the span tags. This apparently breaks justified text on the Kobo.

Was informed by Kovid that this was necessary to fix highlighting without ugly gaps, which was more important, since justified text was not an important part of reading, and that I was the only one complaining. And that his recommended solution would be to simply not use justified text. :shrug

Which is fair enough, but I'd love to see if anyone's discovered a workaround for those who use text justification?

Is there also some possibility of some config on the device causing this and potentially approaching a fix from that angle?

[JSWolf]

Originally Posted by Patrick Faret

Bonjour, à propos de KobotouchExtended,
je veins d'apprendre qu'il est devenu natif dans Calibre.
Comment accéder à ses paramètres
Merci

What operating system and what version of calibre are you using? If you use calibre 8, then you'll configure the KoboTouch driver to do what you want when sending to your Kobo.

[JSWolf]

Originally Posted by hengyu

Hi all,

I've noticed that KEPUBs converted by Calibre 8 onwards have badly broken justification (see comparison shot).

I raised a Calibre bug here:
https://bugs.launchpad.net/calibre/+bug/2107778

It was discovered that the output is different apparently in how the spaces are placed in or around the span tags. This apparently breaks justified text on the Kobo.

Was informed by Kovid that this was necessary to fix highlighting without ugly gaps, which was more important, since justified text was not an important part of reading, and that I was the only one complaining. And that his recommended solution would be to simply not use justified text. :shrug

Which is fair enough, but I'd love to see if anyone's discovered a workaround for those who use text justification?

Is there also some possibility of some config on the device causing this and potentially approaching a fix from that angle?

In Kobo eReader.conf (in .kobo/kobo) on your Kobo, under [Reader], add

webkitTextRendering=geometricPrecision

and see if that fixes the problem.

Also, there is a patch that will reduce the space in KePub. I do not know if it works with the current Libra Colour firmware. You can try the previous firmware's patches and see if it works with the current firmware. You will have to edit it for the new firmware and then try it.

https://www.mobileread.com/forums/sh...d.php?t=366569

[hengyu]

I've already got webkitTextRendering=geometricPrecision set, unfortunately!

The problem is not so much that the spaces are all too big. Sometimes they are also too small, like the one that's after the period here.

From what I understand from the bug report's comments, the KEPUB conversion in native Calibre 8 was fixed to solve some highlighting related issue by putting the whitespaces inside the spans, but in so doing this causes Kobo to not properly render them in justified text.

It's quite a shame that something so basic was broken in order to fix gaps in highlighting (which admittedly is also a very basic thing).

Are there KEPUB books that are directly purchased officially instead of converted from EPUB? I wonder if this issue also happens in that context?

[DNSB]

Originally Posted by hengyu

Are there KEPUB books that are directly purchased officially instead of converted from EPUB? I wonder if this issue also happens in that context?

Books that are synced directly from Kobo are in kepub. And yes, they will show many of the same issues, spaces inside words, varying gaps between words, etc.

That is one reason that I personally only use kepub for books where the images are worth zooming which isn't all that many. I accept the oddities on Kobo Plus books since the authors will not be paid if I don't read the original.

I also prefer using left justification (AKA ragged right) since that removes the justification oddities from the equation. Until an ereader has decent support for micro-typography AKA micro-justification, justified text on my ereader screen is never going to look the way I want it to look.

[Terisa de morgan]

Originally Posted by hengyu

I've already got webkitTextRendering=geometricPrecision set, unfortunately!

The problem is not so much that the spaces are all too big. Sometimes they are also too small, like the one that's after the period here.

From what I understand from the bug report's comments, the KEPUB conversion in native Calibre 8 was fixed to solve some highlighting related issue by putting the whitespaces inside the spans, but in so doing this causes Kobo to not properly render them in justified text.

It's quite a shame that something so basic was broken in order to fix gaps in highlighting (which admittedly is also a very basic thing).

Are there KEPUB books that are directly purchased officially instead of converted from EPUB? I wonder if this issue also happens in that context?

Just a question. Did the highlighting issue exist with this driver before the change to calibre 8.0?

[DNSB]

Originally Posted by Terisa de morgan

Just a question. Did the highlighting issue exist with this driver before the change to calibre 8.0?

Yes, there were several complaints about highlighting along with spaces disappearing.

[jackie_w]

Originally Posted by Terisa de morgan

Just a question. Did the highlighting issue exist with this driver before the change to calibre 8.0?

Originally Posted by DNSB

Yes, there were several complaints about highlighting along with spaces disappearing.

I think you may be talking at cross purposes here.

The "disappearing spaces" problem occurred due to accidental coding errors introduced to the old KTE plugin during a few fairly recent updates (pre-calibrev8), which made some slight changes to the regex it used during koboSpan creation. The missing spaces were actual "lost spaces" accidentally removed during kepubify-ing.

OTOH, the "highlight gaps", referenced by @hengyu, occur because an early version of calibre v8's kepubify allowed some (not all) body text space chars to remain outside of the 2 koboSpans on either side of the space char. Highlighting is only applied to text within a koboSpan - hence the visible gaps.

Someone complained about the aesthetic of these gaps so I think Kovid changed the calibre code so that all text, including spaces, was always contained within a koboSpan. The result is no highlight gaps. This is what the old KTE plugin always did because it aimed to reproduce what Kobo do in their purchased OTA kepubs. AFAIK calibrev8 has never "lost" any spaces.

I know from my own experimentation with kepubify-ing epubs (in 2016) that, ironically, leading and trailing spaces inside koboSpans are one of the main contributing factors to uneven spacing seen in kepubs which are both full-justified and have font kerning/ligatures enabled.

[JSWolf]

Originally Posted by hengyu

I've already got webkitTextRendering=geometricPrecision set, unfortunately!

The problem is not so much that the spaces are all too big. Sometimes they are also too small, like the one that's after the period here.

From what I understand from the bug report's comments, the KEPUB conversion in native Calibre 8 was fixed to solve some highlighting related issue by putting the whitespaces inside the spans, but in so doing this causes Kobo to not properly render them in justified text.

It's quite a shame that something so basic was broken in order to fix gaps in highlighting (which admittedly is also a very basic thing).

Are there KEPUB books that are directly purchased officially instead of converted from EPUB? I wonder if this issue also happens in that context?

Can you please try the version of calibre 8 prior to the fix for the highlighting to see what you get? If the page is rendered correctly, then you can put in a bug report.

[ownedbycats]

Originally Posted by JSWolf

Can you please try the version of calibre 8 prior to the fix for the highlighting to see what you get? If the page is rendered correctly, then you can put in a bug report.

Can use portable version (Windows) to avoid having to uninstall.

[chaley]

Originally Posted by JSWolf

Can you please try the version of calibre 8 prior to the fix for the highlighting to see what you get? If the page is rendered correctly, then you can put in a bug report.

Kovid has already said he isn't going to change this. You get continuous highlighting or better justification, but not both. He chose highlighting.

[JSWolf]

Originally Posted by chaley

Kovid has already said he isn't going to change this. You get continuous highlighting or better justification, but not both. He chose highlighting.

I'd prefer justification. The highlighting wasn't an issue at all.

[hengyu]

Originally Posted by JSWolf

I'd prefer justification. The highlighting wasn't an issue at all.

Please let him know that. He was rather cross with me in our exchange on the bug report for being "the only person in millions" complaining about his choice and insisted that justification wasn't a fundamental functionality :shrug

[compurandom]

Originally Posted by hengyu

Please let him know that. He was rather cross with me in our exchange on the bug report for being "the only person in millions" complaining about his choice and insisted that justification wasn't a fundamental functionality :shrug

This really sounds like a bug or misfeature in the kobo kepub renderer.

However, considering we can optimize it in one of two ways, maybe this needs to be an option in the converter?

[icallaci]

Originally Posted by compurandom

However, considering we can optimize it in one of two ways, maybe this needs to be an option in the converter?

That would be really helpful, if it can be done. I don't care about highlighting, but the terrible spacing in kepubs drives me crazy (and I've tweaked and configured until it sorta kinda works, but not very well).