Bug 168613 - Overlapping ligature glyphs involving font fallback in certain languages
Summary: Overlapping ligature glyphs involving font fallback in certain languages
Status: UNCONFIRMED
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: graphics stack (show other bugs)
Version:
(earliest affected)
unspecified
Hardware: All All
: medium normal
Assignee: Not Assigned
URL:
Whiteboard:
Keywords:
Depends on:
Blocks: Font-Fallback CTL
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Reported: 2025-09-29 15:27 UTC by Jonathan Clark
Modified: 2025-09-29 15:27 UTC (History)
2 users (show)

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Description Jonathan Clark 2025-09-29 15:27:14 UTC 
Description:
In certain cases and with certain fonts, CTL text subject to font fallback can still produce overlapping glyphs. These appear to be ligatures.

Important notes:

- The results are sensitive to the specific font used for fallback. You may see large differences by changing the text language or the base font.

- This may not reproduce consistently on Windows due to font linking.

Steps to Reproduce:
1. Open attachment 202926 [details], a text file containing the endonyms of various languages from Wikipedia.
2. Paste the contents without formatting into Writer.
3. Make sure the Western, Asian, and Complex fonts are all set to something like Noto Sans (not the language-specific subfonts).
4. Note that some of the CTL endonyms are formatted incorrectly (for example, Burmese).
5. Change the font to a language-specific font. For example, change the Burmese text to use Noto Sans Myanmar.
6. Note that the text is now rendered correctly.

Actual Results:
Certain CTL text is rendered incorrectly due to font fallback.

Expected Results:
Text should be rendered correctly, even if we have to use font fallback.


Reproducible: Always


User Profile Reset: No

Additional Info:
Version: 25.8.1.1 (X86_64)
Build ID: 54047653041915e595ad4e45cccea684809c77b5
CPU threads: 12; OS: Linux 6.2; UI render: default; VCL: gtk3
Locale: en-US (en_US.UTF-8); UI: en-US
Calc: threaded