fix: preserve multi-byte UTF-8 in text preprocessing (fixes #1705)#1820
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krystophny merged 1 commit intomainfrom Apr 25, 2026
Merged
fix: preserve multi-byte UTF-8 in text preprocessing (fixes #1705)#1820krystophny merged 1 commit intomainfrom
krystophny merged 1 commit intomainfrom
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The preprocess_math_text and process_latex_in_text functions processed text byte-by-byte, breaking multi-byte UTF-8 sequences (e.g. superscript ² U+00B2 encoded as bytes C2 B2). Orphaned continuation bytes were misinterpreted as new character starts, producing spurious glyphs in rendered output. Fix makes both functions UTF-8 aware: multi-byte characters are now detected via utf8_char_length and copied as intact sequences rather than processed byte-by-byte. Adds test_utf8_text_preprocessing with coverage for: - preprocess_math_text with superscripts, Greek letters, mixed ASCII/UTF-8 - process_latex_in_text with Unicode pass-through - prepare_text_for_raster full pipeline - 1x3 subplot rendering with Unicode ylabel + ASCII suptitle
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Summary
preprocess_math_textandprocess_latex_in_textUTF-8 aware so multi-byte characters (superscripts, Greek letters, etc.) are copied as intact byte sequences rather than being processed byte-by-byteChanges
src/text/fortplot_text_layout.f90:preprocess_math_textusesutf8_char_lengthto detect and copy multi-byte sequences intactsrc/utilities/text/fortplot_latex_parser.f90:process_latex_in_textusesutf8_char_lengthto detect and copy multi-byte sequences intacttest/test_utf8_text_preprocessing.f90: new test covering UTF-8 preservation through the full preprocessing pipeline plus the exact issue scenarioVerification
Requirement: suptitle renders without spurious glyph
Command:
pdftotext output/example/fortran/subplot_demo/subplot_1x3_demo.pdf -Output excerpt:
Polynomial Growth Comparison— clean text, no extra characters between "Growth" and "Comparison"Requirement: Unicode superscripts in labels preserved
Command:
fpm test --target test_utf8_text_preprocessingOutput:
Requirement: artifact verification passes
Command:
make verify-artifactsOutput:
Artifact verification passed.(all checks green, including unicode_demo α and ω assertions)Artifact paths
output/example/fortran/subplot_demo/subplot_1x3_demo.pdf— suptitle cleanoutput/example/fortran/subplot_demo/subplot_1x3_demo.png— suptitle cleanbuild/test/output/test_utf8_suptitle.png— test-generated artifact with Unicode ylabel + ASCII suptitle