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#1 2017-04-09 22:53:15

JonnyRobbie
Member
Registered: 2015-04-28
Posts: 170

Konsole font rendering issue

The problem is that Konsole fails to render some unicode characters in GohuFont:

Here's some pangram demonstrating the issue:

http://i.imgur.com/Ipkk4WT.png

Those missing characters are however rendered when requesting bold variant, but weirdly, Konsole renders their regular variant:

http://i.imgur.com/bRCiXoL.png

You can see that st renders all correctly:

http://i.imgur.com/E5rh7zP.png
It seems that it only affect characters above unicode codepoint 255 however.

The same happens with Qt app like Kate editor too.

I've tried looking at locale, fontconfig, FC_DEBUG, etc, but I couldn't figure anything out. Anyone had similar issue, or any idea what might be wrong?

$ uname -roms
Linux 4.10.6-1-ARCH x86_64 GNU/Linux
$ pacman -Qi fontconfig | grep Version
Version         : 2.12.1-4
$ konsole -v
konsole 16.12.3
$ qtdiag-qt5 | head -1
Qt 5.8.0 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 6.3.1 20170109) on "xcb"

Last edited by JonnyRobbie (2017-04-09 22:54:17)

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#2 2017-04-11 12:52:54

imdn
Member
Registered: 2016-04-12
Posts: 40

Re: Konsole font rendering issue

Assuming you installed Gohu from AUR, I looked at the PKGBUILD and it seems to use the PCF format https://en.wikipedia.org/wiki/Portable_Compiled_Format which is not scalable. The  default available sizes are 11 and 14. Try installing the TTF version from the gohu font website and see if it makes a difference.

It's also worth examining /etc/fonts/conf.d to see if there are any settings that are dependent on font size. E.g features like sub-pixel rendering can be disabled below a specified font size.

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#3 2017-04-11 13:16:04

JonnyRobbie
Member
Registered: 2015-04-28
Posts: 170

Re: Konsole font rendering issue

Yes, it's the AUR `gohufont` version. But it's a bitmap font. I don't need it to scale. I want it hinted to my monitor pixel grid as bitmap fonts can be. Besides, as I've shown, the console can actually render those glyphs, just with a pretty strange behaviour. I'll try the ttf version, but I wonder why the pcf one doesn't work - alsi I'd like to know if it is reproducible. Anyone else has this issue?

Last edited by JonnyRobbie (2017-04-11 13:16:45)

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#4 2017-05-10 08:51:53

pav.rez@centrum.cz
Member
Registered: 2017-05-10
Posts: 2

Re: Konsole font rendering issue

I have exactly the same problem with Terminus font v4.40 (and czech characters...). There is one observation, though I don't know if it can help in tracking the issue - the characters are displayed correctly with older version of the Terminus font v4.39. I was playing with the pcf files (actually just the only one I use - unicode of size 12). The only difference in the pcf files is the number of characters - 894 vs 1212. Sequentially cutting down the number of characters from 1212 down to 894, the font started to work when I reduced it to 895. But it does not seem to depend of which additional character is left. So it seems there are two possibilities for the cause:

a) Either the KDE font rendering is not able to cope with large number of characters - but it would be strange the limit is by chance so close to the old terminus font "size" of 895,

b) or there is somewhere caching of the fonts in KDE, which does not update correctly with new fonts installed/updated. I actually tried to regenerate system and local-user font-caches as well as delete KDE caches, but nothing helped (but I am not an expert and thus I might have missed some of them).

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#5 2017-05-10 09:32:00

pav.rez@centrum.cz
Member
Registered: 2017-05-10
Posts: 2

Re: Konsole font rendering issue

Actually the problem seems more complicated - the wrong rendering happens kind of randomly for regular and bold characters at different font sizes (for some sizes the bold characters do not work, for some the regular ones) and it also depends on DPI settings. It may be somewhat related to, but not exactly the same as, the "scaling problem" e.g. mentioned here: https://bugs.kde.org/show_bug.cgi?id=373232 (which is supposed to be fixed...).

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