[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: [e-mail]
          Reporter: [e-mail]
        QA Contact: [e-mail]
                CC: [e-mail],
                    [e-mail], [e-mail]

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.

[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  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |[e-mail]

--- Comment #1 from Mike FABIAN  ---
Created attachment 1224373
  --> https://bugzilla.redhat.com/attachment.cgi?id=1224373&action=edit
OldHungarian.ttf

This font lacks a space.

[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  ---
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

[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  ---
See also:

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

[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  ---
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.

[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  changed:

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

[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  ---
(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
 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?

[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  ---
This might be related:
https://git.gnome.org/browse/pango/commit/?id=d489ad061d70526fc5f5cdae2273e9...

[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  ---
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 ...

[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  ---
(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?

[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  ---
Dunno. the original issue for that seems fixed with it at least though.

[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

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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

Fedora End Of Life  changed:

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

--- Comment #11 from Fedora End Of Life  ---
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