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Posted to fop-dev@xmlgraphics.apache.org by bu...@apache.org on 2010/02/18 15:29:34 UTC
DO NOT REPLY [Bug 48766] New: Support for Font Kerning is Broken
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
Summary: Support for Font Kerning is Broken
Product: Fop
Version: all
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: fonts
AssignedTo: fop-dev@xmlgraphics.apache.org
ReportedBy: vhennebert@gmail.com
The method o.a.f.fonts.Font.getKernValue expects two Unicode code points and
returns the amount of kerning between the two corresponding glyphs. However,
the implementation for Type 1 fonts interprets the two integers as character
codes in the font's internal encoding (see o.a.f.fonts.type1.AFMFile.java).
Those usually have nothing to do with Unicode code points.
Moreover, trying to get kerning between two characters is inherently wrong:
kerning applies to glyphs and not characters. A font may have several glyph
variants for a same character, and kerning is likely to be different for each
variant.
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
Glenn Adams <gl...@skynav.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P2 |P3
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #8 from Glenn Adams <gl...@skynav.com> 2012-04-07 01:44:44 UTC ---
resetting P2 open bugs to P3 pending further review
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #2 from Vincent Hennebert <vh...@gmail.com> 2010-02-18 14:35:42 UTC ---
Created an attachment (id=25017)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=25017)
PDF result; the right borders should be aligned
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #3 from Jeremias Maerki <je...@apache.org> 2010-02-18 15:15:25 UTC ---
Currently, kerning only works for characters within the main single-byte
encoding. The implementation uses character codes, not Unicode values, for
kerning pairs. That feature didn't make the transition from a single
single-byte encoding to multiple single-byte encodings. Type1Loader and
especially AFMFile will probably need to be improved to support kerning for all
available glyphs.
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #6 from Vincent Hennebert <vh...@gmail.com> 2010-02-19 15:23:57 UTC ---
(In reply to comment #5)
> Created an attachment (id=25018)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=25018) [details]
> Screenshot from OpenOffice Writer
>
> I've just tested with Nimbus Sans L (V 1.05) and kerning works just fine for
> those combinations for which there is data in the AFM, with PDF and PS. The AFM
> I have doesn't have kerning info for “YÆ” or “Fø”.
Then please download the font from the link above.
> Maybe you just expect
> characters like "A" and "Æ" to be equivalent, but I don't remember any mention
> in any of the Type1-related specs where it is listed which glyphs are
> interchangeable concerning kerning. Take "AY" and "ÆY": this combination can
> definitely not be the same as the font shapes are quite different.
>
> Not even OpenOffice does this kind of kerning, not even with Arial or any other
> font I've checked. So IMO, it's a bit much to say it "doesn't work at all".
So where is the code that makes the conversion between Unicode code points as
provided by the layout engine and the character codes as stored in the font's
kerning map?
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #1 from Vincent Hennebert <vh...@gmail.com> 2010-02-18 14:34:29 UTC ---
Created an attachment (id=25016)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=25016)
Sample FO file showing the issue
This sample file uses the Nimbus Sans L font available on most Unix systems and
downloadable here:
http://sourceforge.net/projects/gs-fonts/
The AFM file gives the same kerning between 'Y' and all the accented variants
of the 'A' letter. Yet kerning is applied only between 'Y' and non-accented
'A'.
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #4 from Vincent Hennebert <vh...@gmail.com> 2010-02-18 15:41:09 UTC ---
(In reply to comment #3)
> Currently, kerning only works for characters within the main single-byte
> encoding.
No, kerning doesn't work at all. Like I said the layout engine expects Unicode
code points while the font uses character codes. It's only a chance if they are
the same. Basically, for Adobe Standard Encoding, only the characters (and not
even all) from the Basic Latin range (U+0000–U+007F). Try “YA” vs “YÆ”, or “Fo”
vs “Fø” (kerning should be the same). All in Nimbus Sans L's base encoding.
> The implementation uses character codes, not Unicode values, for
> kerning pairs. That feature didn't make the transition from a single
> single-byte encoding to multiple single-byte encodings. Type1Loader and
> especially AFMFile will probably need to be improved to support kerning for all
> available glyphs.
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #7 from Jeremias Maerki <je...@apache.org> 2010-02-19 15:48:02 UTC ---
Ah, I see, they added many more kerning pairs from version 1.05 to 1.06 of
Nimbus Sans L.
The code that builds the kerning map from the AFM file is
AFMFile.createXKerningMapEncoded(). So, as mentioned before, the problem is
that this method is only aware of the primary single-byte encoding. I can't
deal with the supplemental encodings in which characters like "Æ" will be
found. You can see how the character codes are derived from the multiple
encodings in SingleByteFont.mapChar()/mapUnencodedChar(). Maybe it makes sense
to just keep the kerning pairs with their glyph names (rather than building the
map based on character codes) and store the whole map in SingleByteFont. But
that may also be a bit slower. HTH
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DO NOT REPLY [Bug 48766] Support for Font Kerning is Broken
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=48766
--- Comment #5 from Jeremias Maerki <je...@apache.org> 2010-02-18 16:10:06 UTC ---
Created an attachment (id=25018)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=25018)
Screenshot from OpenOffice Writer
I've just tested with Nimbus Sans L (V 1.05) and kerning works just fine for
those combinations for which there is data in the AFM, with PDF and PS. The AFM
I have doesn't have kerning info for “YÆ” or “Fø”. Maybe you just expect
characters like "A" and "Æ" to be equivalent, but I don't remember any mention
in any of the Type1-related specs where it is listed which glyphs are
interchangeable concerning kerning. Take "AY" and "ÆY": this combination can
definitely not be the same as the font shapes are quite different.
Not even OpenOffice does this kind of kerning, not even with Arial or any other
font I've checked. So IMO, it's a bit much to say it "doesn't work at all".
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