[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

--- Comment #9 from Khaled Hosny  ---
Created attachment 137364
  --> https://bugs.documentfoundation.org/attachment.cgi?id=137364=edit
How the text looks with GPOS table removed fom the font

Here is how the text looks when I remove the GPOS using FontTools Python
library:

$ ttx -x GPOS BukyVede-Regular.ttf
$ ttx BukyVede-Regular.ttx

and then using the BukyVede-Regular#1.ttf instead of the old file.

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

Khaled Hosny  changed:

   What|Removed |Added

 Status|REOPENED|RESOLVED
 Resolution|--- |NOTOURBUG

--- Comment #8 from Khaled Hosny  ---
This is a font bug, LibreOffice does not interfere with mark positioning
provided by the font, however this font does not provide any mark positioning
at all and relies solely on heuristics applied by the text layout system.

We use HarfBuzz which have such heuristics, but it applies them only when the
font does not have GPOS table (glyph positioning table) but this font has one
that does kerning only and no mark positioning.

It is possible that the system text layout libraries that we used before
applied these heuristics more liberally. But font designers should not be
depending on such heuristics since they are neither standardized nor well
documented.

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

--- Comment #7 from Volga  ---
Created attachment 135457
  --> https://bugs.documentfoundation.org/attachment.cgi?id=135457=edit
Screenshot with BukyVede and BabelPad

I tested on both BabelPad and LibreOffice, these fonts performanced the same to
me, so I can sure this font is a bit buggy.

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

--- Comment #6 from Francis Butler  ---
I note that, as Volga remarks, the characters do combine properly in ponomar
ttf but not ponomar otf . However, in light of my previous remarks, it still
seems that the bug is in LibreOffice, and not in the many fonts that have
suddenly become problematic.

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

Francis Butler  changed:

   What|Removed |Added

 Status|RESOLVED|REOPENED
 Resolution|NOTOURBUG   |---

--- Comment #5 from Francis Butler  ---
Volga suggests that the problem is with the font Bukyvede. However, if I
understand Volga correctly, ҇ does not combine with ⷮ above a third letter in
the font Ponomar or  presumably, in any other Slavic font the contains the
combining characters. This would mean that the bug is shared by all such Slavic
fonts. The problem with this response is that the characters combined perfectly
well in OfficeLibre 5, and even in old versions of Microsoft Word. It appears
that some "improvement" in OfficeLibre has, as a side effect, prevented the
combination from working in any font. I would guess that the "improvement" was
intended to prevent large stacks of letters from overlapping with the line
above the stacks. Perhaps the "improvement" is even recommended in some
technical UNIX document. This does not mean that the result is not a bug, since
it ruins the functionality of a large group of fonts that have been functional
(with updates) for decades.

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

Volga  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |NOTOURBUG

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

--- Comment #4 from Volga  ---
Created attachment 135263
  --> https://bugs.documentfoundation.org/attachment.cgi?id=135263=edit
Screenshot with Ponomar Unicode

With PonomarUnicode.otf (NOT .ttf, availabe at
http://sci.ponomar.net/fonts.html) I found all of then except лⷮ҇ have such
problem, and I found the shape of ⷮ (U+2DEE) designed not suitable to combine
with ҇ (U+0435). With BukyVede font I found all Combining Cyrillic letters
overlapped with U+0435 even if U+2DEE looks just like small т, so I can
conclusion this is font issue, and I suggest you can contect designers of
BukyVede font for this.

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

--- Comment #3 from V Stuart Foote  ---
Using BabelPad, a Unicode 9 compliant editor, selecting multiple Cyrillic
combining glyphs stack as OP requires.  

This Unicode.org technical note L2/15-002 seems germane, and has a few more
examples:
http://unicode.org/L2/L2015/15002-double-titli.pdf

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

V Stuart Foote  changed:

   What|Removed |Added

 OS|Mac OS X (All)  |All

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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

V Stuart Foote  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 CC||vstuart.fo...@utsa.edu
 Blocks||71732, 103729
 Ever confirmed|0   |1

--- Comment #2 from V Stuart Foote  ---
Not sure how the script is supposed to handle them but with Segoe UI while they
combine we do seem to have misalignment with multiple combining glyphs. 

Combining characters in these Unicode blocks:
0483-0489
2de0-2dff
a66f-a67d

рⷱ҇е прⷪ҇ркъ лⷮ҇ from attachment 134779

U+0440U+2df1U+0487U+0435  -- рⷱ҇е
U+043fU+0440U+2deaU+0487U+0440U+043aU+044a --  прⷪ҇ркъ
U+043bU+2deeU+0487 -- лⷮ҇

U+a69bU+a67cU+a674  -- ꚛ꙼ꙴ


Referenced Bugs:

https://bugs.documentfoundation.org/show_bug.cgi?id=71732
[Bug 71732] [META] Bugs related to text rendering, typography and font features
in LO
https://bugs.documentfoundation.org/show_bug.cgi?id=103729
[Bug 103729] [META] HarfBuzz-based common text layout regressions
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[Libreoffice-bugs] [Bug 109268] Combining Cyrillic characters overlap when placed above each other e.g. лⷣ҇

[bugzilla-daemon]

https://bugs.documentfoundation.org/show_bug.cgi?id=109268

--- Comment #1 from Francis Butler  ---
Created attachment 134779
  --> https://bugs.documentfoundation.org/attachment.cgi?id=134779=edit
Sample of Cyrillic combining character overlap

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