https://bugs.documentfoundation.org/show_bug.cgi?id=173643
Bug ID: 173643
Summary: Combining tilde is incorrectly positioned when ɑ̃ is
entered via XCompose
Product: LibreOffice
Version: 26.2.5.2 release
Hardware: x86-64 (AMD64)
OS: Linux (All)
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: Writer
Assignee: [email protected]
Reporter: [email protected]
Description:
Title: Combining tilde is incorrectly positioned when ɑ̃ is entered via XCompose
Summary
On Linux, the combining tilde is incorrectly positioned when the Unicode
sequence U+0251 U+0303 (ɑ + COMBINING TILDE) is entered through XCompose. The
identical Unicode sequence is rendered correctly when pasted.
Environment
Ubuntu 24.04
LibreOffice Writer (Snap package)
LibreOffice 26.2.5.2
Charis 7.000
XCompose
QT_IM_MODULE=ibus
Firefox and GNOME Text Editor are also available for comparison
XCompose rule
<Multi_key> <a> <n> : "ɑ̃"
This produces the correct Unicode sequence:
U+0251 LATIN SMALL LETTER ALPHA
U+0303 COMBINING TILDE
Steps to reproduce
Select Charis as the font in Writer.
Place the cursor in a text paragraph.
Enter ɑ̃ using the XCompose sequence Multi_key, a, n.
Observe the position of the combining tilde.
Delete the result and paste the exact same string ɑ̃ from another application.
Expected result
The combining tilde should be positioned correctly above the ɑ, just as it is
when the same Unicode sequence is pasted.
Actual result
When entered through XCompose, the tilde is incorrectly positioned to the right
of the ɑ rather than being correctly positioned above it.
When the exact same Unicode sequence is pasted into Writer, it is rendered
correctly.
Additional observations
The problem is not specific to the Charis font. Charis 7 correctly renders the
sequence when it is pasted into Writer.
The same distinction can be observed in GNOME Text Editor:
XCompose input → incorrect positioning
Pasted ɑ̃ → correct positioning
Firefox, however, renders the sequence correctly even when it is entered
through the same XCompose rule.
The resulting ɑ̃ is nevertheless treated as a single grapheme for text editing
purposes: moving the cursor or inserting another character does not treat the
combining tilde as an independent character.
Thus the problem appears to concern glyph shaping/positioning during or
immediately after XCompose input, rather than Unicode composition or
recognition of the combining mark.
Comparison
Input method Writer GNOME Text Editor Firefox
XCompose ɑ̃ incorrect incorrect correct
Paste ɑ̃ correct correct correct
A screenshot showing these three cases is attached.
Notes
There is no precomposed Unicode character for LATIN SMALL LETTER ALPHA +
COMBINING TILDE. The intended representation is therefore necessarily the
two-codepoint sequence U+0251 U+0303; replacing it with ã (U+00E3) is not
equivalent.
Steps to Reproduce:
Select Charis as the font in Writer.
Place the cursor in a text paragraph.
Enter ɑ̃ using the XCompose sequence Multi_key, a, n.
Observe the position of the combining tilde.
Delete the result and paste the exact same string ɑ̃ from another application.
Actual Results:
When entered through XCompose, the tilde is incorrectly positioned to the right
of the ɑ rather than being correctly positioned above it.
When the exact same Unicode sequence is pasted into Writer, it is rendered
correctly.
Expected Results:
The combining tilde should be positioned correctly above the ɑ, just as it is
when the same Unicode sequence is pasted.
Reproducible: Always
User Profile Reset: No
Additional Info:
Additional observations
The problem is not specific to the Charis font. Charis 7 correctly renders the
sequence when it is pasted into Writer.
The same distinction can be observed in GNOME Text Editor:
XCompose input → incorrect positioning
Pasted ɑ̃ → correct positioning
Firefox, however, renders the sequence correctly even when it is entered
through the same XCompose rule.
The resulting ɑ̃ is nevertheless treated as a single grapheme for text editing
purposes: moving the cursor or inserting another character does not treat the
combining tilde as an independent character.
Thus the problem appears to concern glyph shaping/positioning during or
immediately after XCompose input, rather than Unicode composition or
recognition of the combining mark.
Comparison
Input method Writer GNOME Text Editor Firefox
XCompose ɑ̃ incorrect incorrect correct
Paste ɑ̃ correct correct correct
Notes
There is no precomposed Unicode character for LATIN SMALL LETTER ALPHA +
COMBINING TILDE. The intended representation is therefore necessarily the
two-codepoint sequence U+0251 U+0303; replacing it with ã (U+00E3) is not
equivalent.
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