[Bug 1398676] New: Pango sometimes shows a replacement character for space (U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676

            Bug ID: 1398676
           Summary: Pango sometimes shows a replacement character for
                    space (U+0020) when a font lacks a space
           Product: Fedora
           Version: 25
         Component: pango
          Assignee: tagoh(a)redhat.com
          Reporter: mfabian(a)redhat.com
        QA Contact: extras-qa(a)fedoraproject.org
                CC: fonts-bugs(a)lists.fedoraproject.org,
                    i18n-bugs(a)lists.fedoraproject.org, tagoh(a)redhat.com



Created attachment 1224372
  --> https://bugzilla.redhat.com/attachment.cgi?id=1224372&action=edit
pango-bug.png

Tested on the released version of Fedora 25.
pango-1.40.3-1.fc25.x86_64

When using a font which does not have a space, Pango may show a replacement
character for space( U+0020).

I’ll attach the file rovas.txt which has a first line containing only Old
Hungarian
script and a space.

I’ll also attach an old Hungarian font taken from
https://github.com/OldHungarian/old-hungarian-font/releases which lacks a
space.

Display the test file like this:

    pango-view --font="Old Hungarian" ~/rovas.txt


And you get something as in the also attached screenshot which shows
that Pango renders the space as an replacement character.

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676

Mike FABIAN <mfabian(a)redhat.com&gt; changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mfabian(a)redhat.com



--- Comment #1 from Mike FABIAN <mfabian(a)redhat.com&gt; ---
Created attachment 1224373
  --> https://bugzilla.redhat.com/attachment.cgi?id=1224373&action=edit
OldHungarian.ttf

This font lacks a space.

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #2 from Mike FABIAN <mfabian(a)redhat.com&gt; ---
Created attachment 1224374
  --> https://bugzilla.redhat.com/attachment.cgi?id=1224374&action=edit
rovas.txt

Test file. Display it with 

pango-view --font="Old Hungarian" ~/rovas.txt

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #3 from Mike FABIAN <mfabian(a)redhat.com&gt; ---
See also: 

https://github.com/OldHungarian/old-hungarian-font/issues/1

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #4 from Akira TAGOH <tagoh(a)redhat.com&gt; ---
Mike, can you file a bug to upstream bugzilla as well?
Though that looks to me like a bug in font as well as we saw the similar issue
in the Indic fonts and fixed it there. I'm not sure if the en.orth file in
fontconfig should contains U+0020 to avoid the sort of this situation. dunno if
that really helps. not yet tested.

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676

Mike FABIAN <mfabian(a)redhat.com&gt; changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
    External Bug ID|                            |GNOME Desktop 775202



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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #5 from Mike FABIAN <mfabian(a)redhat.com&gt; ---
(In reply to Akira TAGOH from comment #4)
>  Mike, can you file a bug to upstream bugzilla as well? 
Done: https://bugzilla.gnome.org/show_bug.cgi?id=775202

>  Though that looks to me like a bug in font as well as we saw the
> similar
>  issue in the Indic fonts and fixed it there.  
Was a space missing in the Indic fonts? Is there a requirement
in some standard that a font must have a space?

The upstream author of OldHungarian.ttf is reluctant to add
a space, see:

https://github.com/OldHungarian/old-hungarian-font/issues/1

stupy> Meanwhile I saw that adding the space character will most
stupy> likely break web usage for the font, as it will override the
stupy> main space character for the site for normal text as well. I
stupy> might need to create two separate fonts, one with extra glyphs,
stupy> and one without them

He created two different fonts now, one with a space and one without.
This is quite ugly and confusing I think. Therefore, if fonts are not
required to have a space by some standard, this probably should be
fixed in Pango.

A similar problem recently occured for Andreas Schneider
<asn(a)redhat.com&gt; without using OldHungarian.ttf but some other fonts
on a default installation of Fedora.  So this may happen in some
circumstances even on a default installation of Fedora.

>  I'm not sure if the en.orth
>  file in fontconfig should contains U+0020 to avoid the sort of this
>  situation. dunno if that really helps. not yet tested. 
Is en.orth relevant if a line rendered by pango-view contains only
Old Hungarian for example?

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #6 from Akira TAGOH <tagoh(a)redhat.com&gt; ---
This might be related:
https://git.gnome.org/browse/pango/commit/?id=d489ad061d70526fc5f5cdae227...

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #7 from Andreas Schneider <asn(a)redhat.com&gt; ---
The scenario I had was that an application used a BLACK STAR (U+2605). The font
I use is Noto Sans which doesn't include that char. So it is looking for
another font providing it. I have texlive installed which installs several
fonts for texlive. So it picked up the first font it found which included the
BLACK STAR. This font was a chinese font starting with the letter A. And that
font did not have a space.

Creating a ~/.config/fontconfig/fonts.conf with fallbacks to a better font,
worked around that problem.


Maybe it would make sense to define symbolic fallback fonts during the
installation based on the keyboard language you select ...

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #8 from Mike FABIAN <mfabian(a)redhat.com&gt; ---
(In reply to Akira TAGOH from comment #6)
>  This might be related:
>  https://git.gnome.org/browse/pango/commit/
>  ?id=d489ad061d70526fc5f5cdae2273e9deabea6a17 
Yes! That seems to cause the problem.

I think is not reasonable to assume that every font has a the ASCII space.
Can’t the problem for Mongolian be fixed without breaking it for fonts
which don’t have the ASCII space?

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #9 from Akira TAGOH <tagoh(a)redhat.com&gt; ---
Dunno. the original issue for that seems fixed with it at least though.

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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

https://bugzilla.redhat.com/show_bug.cgi?id=1398676



--- Comment #10 from Fedora End Of Life <jkurik(a)fedoraproject.org&gt; ---
This message is a reminder that Fedora 25 is nearing its end of life.
Approximately 4 (four) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 25. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
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[Bug 1398676] Pango sometimes shows a replacement character for space ( U+0020) when a font lacks a space

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Fedora End Of Life <jkurik(a)fedoraproject.org&gt; changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |CLOSED
         Resolution|---                         |EOL
        Last Closed|                            |2017-12-12 05:18:29



--- Comment #11 from Fedora End Of Life <jkurik(a)fedoraproject.org&gt; ---
Fedora 25 changed to end-of-life (EOL) status on 2017-12-12. Fedora 25 is
no longer maintained, which means that it will not receive any further
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