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https://issues.apache.org/jira/browse/PDFBOX-4106?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16367651#comment-16367651
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Tilman Hausherr commented on PDFBOX-4106:
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{quote}
If you have an idea for a better solution please let me know.
{quote}
No, I don't have a better solution. I've created a test that fails if somebody
in the future isn't carefully enough.
Can you explain the "Trying to un-substitute a never-before-seen gid" message
one gets when using mode 3 in the example, i.e. disabling the two features? Why
is this a "bad" thing / is it a bad thing?
>From what I see, this comes up because in the getSubstitution() call nothing
>is cached, because featureRecords.isEmpty(). The getUnsubstitution() method
>depends on having a previous call of getSubstitution().
Here's some possible solutions (can be several) because I want to avoid tickets
about this.
- remove the message
- make it debug instead of warning
- add a comment like above, i.e. document this sequential dependency
- keep all as is but make a comment in the sample code
- cache even if langSysTables or featureRecords are empty
- make it stateless (you probably didn't do that because you wanted to save
memory)
Any thoughts?
> Vertical text creation
> ----------------------
>
> Key: PDFBOX-4106
> URL: https://issues.apache.org/jira/browse/PDFBOX-4106
> Project: PDFBox
> Issue Type: New Feature
> Components: FontBox, Parsing, Writing
> Reporter: Aaron Madlon-Kay
> Priority: Major
> Labels: embed, gsub, parsing, vertical
> Attachments:
> 0001-Add-OpenTypeScript-class-to-get-OT-script-tags-for-c.patch,
> 0002-Optimize-Unicode-script-storage-and-lookup.patch,
> 0003-Parse-GSUB-table.patch,
> 0004-Abstract-cmap-lookup-into-an-interface.patch,
> 0005-Implement-GSUB-substitution-on-TrueTypeFont.patch,
> 0006-Use-vhea-vmtx-to-fix-vertical-displacements-in-PCIDF.patch,
> 0007-Add-factory-methods-for-loading-TTF-as-vertical-font.patch,
> 0008-Implement-vertical-metrics-support-when-embedding-subsetting.patch,
> sample_code.txt, vertical.pdf
>
>
> I needed to output vertical Japanese text, but was stymied by several
> limitations:
> * No API to load a TTF as Identity-V encoding
> * No support for 'vert' glyph substitution
> * No support for vertical metrics ('vhea' and 'vmtx' tables are parsed but
> not used at all)
> I have attached a series of patches that implement the above features.
> Highlights:
> * The GSUB glyph substitution table is parsed (limitation: type 1 lookups
> only; this is sufficient for many features including 'vert'/'vrt2' vertical
> glyph substitution)
> * Cmap lookup makes use of GSUB when features are enabled on a TTF
> * 'vhea' and 'vmtx' metrics are applied to PDCIDFont when appropriate, and
> are embedded/subsetted correctly through the DW2/W2 CIDFont dictionary
> * An API has been added for loading a TTF as a vertical font, setting
> Identity-V encoding and enabling 'vert'/'vrt2' substitution
> Each patch could approximately be split out into a separate ticket, if
> desired.
> Also attached is some sample code that exercises these patches and
> illustrates the effect of vertical glyph positioning. The sample output PDF
> is also attached.
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