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https://issues.apache.org/jira/browse/FOP-2213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13581630#comment-13581630
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Vincent Hennebert commented on FOP-2213:
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If a font provides a kern table but no 'kern' feature in the GPOS table, then
the kern table should be used as a fallback, as indicated at
http://www.microsoft.com/typography/otspec/recom.htm:
"When a kern table and GPOS table are both present in a font, and an OFF layout
engine is requested to apply kerning to a run of text of a particular script
and language system: (a) If the number of kern feature lookups in the resolved
language system in the GPOS table is zero, then the kern table should be
applied, followed by any remaining GPOS features requested."
Also, the original font I used was DejaVu Sans [1], that does have a 'kern'
feature in its GPOS table. But because FOP finds no match for the script
('latn') and language ('dflt') that it computes from the FO file, it doesn't
apply it. Actually, it will apply it only if I specify one of the languages
listed under the 'latn' table, for example, 'ROM' for Romanian. Except that the
'language' XSL-FO property does not accept an OpenType language system tag, but
a language tag that conforms to ISO 639-1 (2-letter tag) or ISO 639-2 (3-letter
tag). And the ISO 639-2 tag for Romanian is 'ron' or 'rum', not 'ROM'. So it
seems that the code is lacking the lookup tables that will match an ISO 639
country tag to an OpenType language system tag. Also, IIUC a script table may
reference a default language system that should be used if no language is
specified, or if the particular language is not listed.
[1] http://dejavu-fonts.org/wiki/Main_Page
> Kerning is no longer applied
> ----------------------------
>
> Key: FOP-2213
> URL: https://issues.apache.org/jira/browse/FOP-2213
> Project: Fop
> Issue Type: Bug
> Components: fonts
> Affects Versions: 1.1, trunk
> Reporter: Vincent Hennebert
> Attachments: fop.xconf, kerning_1.0.pdf, kerning_1.1.pdf, kerning.fo,
> kerning-v2_1.1-cs.pdf, kerning-v2_1.1-nocs.pdf, kerning-v2.fo
>
>
> See attached example. With FOP 1.0 the dot can be seen 'inside' the Y glyph
> as expected, while it's not the case with FOP 1.1.
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