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https://issues.apache.org/jira/browse/PDFBOX-4951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18086798#comment-18086798
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Daniel Gredler commented on PDFBOX-4951:
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Please forgive me a couple of drive-by comments from my end :)
> Assuming you know a lot about this part of awt, does it also contain
> something for vertical fonts? We use GSUB for replacement of vertical glyphs.
I'm somewhat familiar with the AWT code, but not with its history (some of it
is ~30 years old). That said, I get the impression from various mentions of
"vertical" in `StandardGlyphVector` and in `ExtendedTextSourceLabel` that there
were plans to support vertical text at some point, but the code that we have
today does not support vertical text.
> Bidi should be handled by a higher level class [...] I did not find an easily
> usable library or a comprehensive description.
My first intuition would also be to look at `java.text.Bidi`. However, I
wouldn't assume that a separate library is needed – have a look at the JDK
classes which use `java.text.Bidi` internally – `TextLine`, `BidiUtils`, etc.
These all seem to get the job done without too much overhead. If
`java.text.Bidi` is fatally flawed in a way which prevents its use outside the
JDK, I'd be interested to know (I occasionally contribute fixes and
enhancements to OpenJDK in this text drawing / font handling area).
> Sequences of DIN SPEC 91379 with combining letters are rendered incorrectly
> ---------------------------------------------------------------------------
>
> Key: PDFBOX-4951
> URL: https://issues.apache.org/jira/browse/PDFBOX-4951
> Project: PDFBox
> Issue Type: Bug
> Components: Rendering
> Affects Versions: 2.0.21
> Reporter: Volker Kunert
> Priority: Major
> Attachments: DIN_SPEC_91379_Sequences-aa.pdf,
> DIN_SPEC_91379_Sequences-ab.pdf, DIN_SPEC_91379_Sequences-ac.pdf,
> DIN_SPEC_91379_Sequences.txt, DefaultScriptProcessor.java, DejaVuSans.ttf,
> DoGlyphLayoutBidi.pdf, DoGlyphLayoutDinSpec91379.pdf,
> DoGlyphLayoutDinSpec91379Form.pdf, DoGlyphPositionBengali.pdf,
> ExamplePdfboxFopPos-By-Tilman.pdf, ExamplePdfboxFopPos.java,
> ExamplePdfboxFopPos.pdf, ExamplePdfboxFopPosForm.java,
> ExamplePdfboxFopPosForm.pdf, FiraCode-Regular.ttf,
> FontForge-Lohit-Bengali.png, TestPdfbox.java, TestPdfboxFop2.java,
> TestPdfboxFop2.pdf, TestPdfboxJava2D.java, TestPdfboxJava2D.pdf, bidi-1.png,
> bidi-2.png, bidi.png, example-PDFBOX-3147-NotoSansThaiLooped-Regular.png,
> image-2026-05-23-16-16-53-442.png, image-2026-05-23-16-17-28-172.png,
> image-2026-05-26-16-49-45-529.png, ligatures-kerning.png,
> patch-2020-10-02.txt, pdfbox.patch, pdfbox.pdf, screenshot-1.png
>
>
> Accented Letters composed of Unicode base letter and combining accent are
> rendered wrong. E.g. with 0041 030B LATIN CAPITAL LETTER A WITH COMBINING
> DOUBLE ACUTE ACCENT the accent appears at the right hand side of the letter
> A, not above the letter A.
> The position is wrong for most of the sequences defined in the following spec:
> DIN SPEC 91379: Characters in Unicode for the electronic processing of names
> and data
> exchange in Europe; with digital attachment
> [https://www.xoev.de/downloads-2316#StringLatin]
> [https://www.din.de/de/wdc-beuth:din21:301228458]
>
> The correct rendering should look like the output of hb-view 2.6.8, see files
> DIN_SPEC_91379_Sequences*.pdf.
> The output of PDFBox is appended in pdfbox.pdf, which is created by running
> TestPdfbox.java. The sequences are read from file
> DIN_SPEC_91379_Sequences.txt.
>
> Font used for testing: NotoSansMono-Regular.ttf, see
> [https://www.google.com/get/noto/]
> download:
> [https://noto-website-2.storage.googleapis.com/pkgs/NotoSansMono-hinted.zip]
> See also FOP-2969
>
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