Gábor Stefanik created PDFBOX-5126:
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Summary: Complex Unicode glyphs (surrogate pairs, combining
diacritics, zero-width join, etc.) in a RTL context get reversed incorrectly on
text extraction
Key: PDFBOX-5126
URL: https://issues.apache.org/jira/browse/PDFBOX-5126
Project: PDFBox
Issue Type: Bug
Components: Text extraction
Affects Versions: 2.0.22
Reporter: Gábor Stefanik
Attachments: rovasvegyes.pdf
The attached PDF contains old Hungarian runic script, which is both
right-to-left and outside Unicode's Basic Multilingual Plane (and thus encoded
as surrogate pairs in Java's internal UTF-16-like representation). When this
text is extracted, the surrogate pairs are reversed due to an overly naive use
of "char"-level reversal, leading to malformed Unicode output.
Likewise, when combining diacritics/modifiers occur in a right-to-left context,
their position relative to the "parent" character is reversed, and so they
appear on the wrong glyph, as demonstrated by the Hebrew sample in the same
PDF. I imagine the same thing would also happen to emoji using the "zero-width
joiner" in an RTL context.
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