A curious font issue

Toolpost · 04-01-2019, 09:53 AM

Hello, ( Newbie alert! )

I was trying to read an epub file in my Kobo, which is in Malayalam language. The "chillu" letters (That's what those letters are called in Malayalam) were not rendering properly. Then I load the epub in Calibre and ended up in this interesting situation. Please see the attached image. I have marked the respective words in red boxes. Why the letters are rendered different in the xhtml viewer and preview panel? The rendering is perfect in the xhtml viewer, but wrong in file preview. Is there some way to rectify this? BTW, I am using Calibre (v3.29) installed form official repository in Fedora 29.

Any advice/suggestions are greatly appreciated. Thank you.

theducks · 04-01-2019, 11:01 AM

I suspect the (embedded) font has glyph issues. Try embedding another font.

Code view, is again, a different font. I think this one is from your System (and this one is usually Mono-spaced, favored by coders).

BetterRed · 04-01-2019, 05:53 PM

FWIW: the font for the CodeView (CV) panels are set in Edit->Preferences->Editor settings, the font for the Preview (PV) panel is set in Edit->Preferences->Editor settings. They can differ e.g. I use Consolas for CV and Liberation variants for PV

IIRC: the calibre viewer will use the embedded fonts, if they exist; and if they don't, the fonts set in the viewer's Preferences->General->Font options settings are used.

BR

Toolpost · 04-02-2019, 01:20 AM

Quote:

Originally Posted by BetterRed

FWIW: the font for the CodeView (CV) panels are set in Edit->Preferences->Editor settings, the font for the Preview (PV) panel is set in Edit->Preferences->Editor settings. They can differ e.g. I use Consolas for CV and Liberation variants for PV

IIRC: the calibre viewer will use the embedded fonts, if they exist; and if they don't, the fonts set in the viewer's Preferences->General->Font options settings are used. Please see the attached images.

BR

Thanks for your suggestions. I have checked both those settings and changed both to "Noto-sans-malayalam" font, which I installed from the fedora official repository. Now the fonts are seems to be same on both panels, though the same problem persists.

Quote:

Originally Posted by theducks

I suspect the (embedded) font has glyph issues. Try embedding another font.

Thanks for your comments. But in this case, there is no font embedded within the epub and no information is found in the css file.

On the other hand, I am able to open and read the epub in Okular and it renders everything perfectly.

kovidgoyal · 04-02-2019, 01:48 AM

It's likely Qt WebKit (the component used to render the preview panel) does not like that font. This will be fixed in calibre 4 when it migrates to usin a different component. In the meantime, try using a different font for the preview panel, or live with it.

Toolpost · 04-02-2019, 07:18 AM

Quote:

Originally Posted by kovidgoyal

It's likely Qt WebKit (the component used to render the preview panel) does not like that font. This will be fixed in calibre 4 when it migrates to usin a different component. In the meantime, try using a different font for the preview panel, or live with it.

Thanks for the information. But, I believe not only a particular font have this issue, since I have installed and tested most of the available Malayalam unicode fonts (such as AnjaliOldLipi, Meera, Rachana, Reghu etc..). Anyways, I shall wait for the version 4 to get thing solved.

BetterRed · 04-02-2019, 08:51 PM

@Toolpost - did you try the Sigil editor, I think it uses a later version of the Qt libraries.

BR

Toolpost · 04-03-2019, 07:34 AM

Quote:

Originally Posted by BetterRed

@Toolpost - did you try the Sigil editor, I think it uses a later version of the Qt libraries.

BR

Yes BR, Actually I did try on Sigil first. The fonts are rendered incorrect in Sigil too. I am using 0.9.12.

BetterRed · 04-03-2019, 07:57 AM

Quote:

Originally Posted by Toolpost

Yes BR, Actually I did try on Sigil first. The fonts are rendered incorrect in Sigil too. I am using 0.9.12.

Bummer

BR

kovidgoyal · 04-03-2019, 08:33 AM

sigil uses the the same qtwebkit calibre does -- even though the version of qt is newer qt webkit tself is no longer maintained.

KevinH · 04-05-2019, 03:35 PM

FWIW, qtwebkit does get some maintenance by Annulen. Bugs reported there are still being responded to. We now build our webkit based on annulen's version 5.212 with the following patches:

See qtwebkit _*.patch at:

https://github.com/Sigil-Ebook/Sigil/tree/master/docs

None of these effect fonts particularly, but Qt (not webkit) has serious issues with fonts especially on Windows machines due to use of the OS2 font tables incorrectly:

See:

https://bugreports.qt.io/browse/QTBUG-73660

and the following font umbrella issue:

https://bugreports.qt.io/browse/QTBUG-74860

So the bug could well be in Qt itself versus QtWebkit.

kovidgoyal · 04-05-2019, 09:28 PM

Yes, the bug is likely in Qt. Qt WebKit uses Qt for its fonts. Qt WebEngine does not (it uses chromium's font backend).

04-01-2019, 09:53 AM	#1
Toolpost Junior Member Posts: 9 Karma: 10 Join Date: Apr 2019 Device: Kobo Glo HD	A curious font issue Hello, ( Newbie alert! ) I was trying to read an epub file in my Kobo, which is in Malayalam language. The "chillu" letters (That's what those letters are called in Malayalam) were not rendering properly. Then I load the epub in Calibre and ended up in this interesting situation. Please see the attached image. I have marked the respective words in red boxes. Why the letters are rendered different in the xhtml viewer and preview panel? The rendering is perfect in the xhtml viewer, but wrong in file preview. Is there some way to rectify this? BTW, I am using Calibre (v3.29) installed form official repository in Fedora 29. Any advice/suggestions are greatly appreciated. Thank you. Attached Thumbnails Last edited by Toolpost; 04-01-2019 at 09:57 AM.

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04-01-2019, 11:01 AM	#2
theducks Well trained by Cats Posts: 31,055 Karma: 60358908 Join Date: Aug 2009 Location: The Central Coast of California Device: Kobo Libra2,Kobo Aura2v1, K4NT(Fixed: New Bat.), Galaxy Tab A	I suspect the (embedded) font has glyph issues. Try embedding another font. Code view, is again, a different font. I think this one is from your System (and this one is usually Mono-spaced, favored by coders).

04-01-2019, 05:53 PM	#3
BetterRed null operator (he/him) Posts: 21,725 Karma: 29711016 Join Date: Mar 2012 Location: Sydney Australia Device: none	FWIW: the font for the CodeView (CV) panels are set in Edit->Preferences->Editor settings, the font for the Preview (PV) panel is set in Edit->Preferences->Editor settings. They can differ e.g. I use Consolas for CV and Liberation variants for PV IIRC: the calibre viewer will use the embedded fonts, if they exist; and if they don't, the fonts set in the viewer's Preferences->General->Font options settings are used. BR

04-02-2019, 01:48 AM	#5
kovidgoyal creator of calibre Posts: 45,349 Karma: 27182818 Join Date: Oct 2006 Location: Mumbai, India Device: Various	It's likely Qt WebKit (the component used to render the preview panel) does not like that font. This will be fixed in calibre 4 when it migrates to usin a different component. In the meantime, try using a different font for the preview panel, or live with it.

04-02-2019, 08:51 PM	#7
BetterRed null operator (he/him) Posts: 21,725 Karma: 29711016 Join Date: Mar 2012 Location: Sydney Australia Device: none	@Toolpost - did you try the Sigil editor, I think it uses a later version of the Qt libraries. BR

04-03-2019, 08:33 AM	#10
kovidgoyal creator of calibre Posts: 45,349 Karma: 27182818 Join Date: Oct 2006 Location: Mumbai, India Device: Various	sigil uses the the same qtwebkit calibre does -- even though the version of qt is newer qt webkit tself is no longer maintained.

04-05-2019, 03:35 PM	#11
KevinH Sigil Developer Posts: 8,763 Karma: 5706256 Join Date: Nov 2009 Device: many	FWIW, qtwebkit does get some maintenance by Annulen. Bugs reported there are still being responded to. We now build our webkit based on annulen's version 5.212 with the following patches: See qtwebkit _*.patch at: https://github.com/Sigil-Ebook/Sigil/tree/master/docs None of these effect fonts particularly, but Qt (not webkit) has serious issues with fonts especially on Windows machines due to use of the OS2 font tables incorrectly: See: https://bugreports.qt.io/browse/QTBUG-73660 and the following font umbrella issue: https://bugreports.qt.io/browse/QTBUG-74860 So the bug could well be in Qt itself versus QtWebkit.

04-05-2019, 09:28 PM	#12
kovidgoyal creator of calibre Posts: 45,349 Karma: 27182818 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Yes, the bug is likely in Qt. Qt WebKit uses Qt for its fonts. Qt WebEngine does not (it uses chromium's font backend).

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