[vim/vim] Fix wide character display with popups (PR #19271)

mattn

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Jan 29, 2026, 3:18:56 AM (10 days ago) Jan 29

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Problem

When a popup window partially overlaps a wide character (e.g., Japanese characters):

Truncated display: If only the right half of a wide character is visible, the character was displayed with its right half cut off, violating Vim's rule that "wide characters with only half visible should not be shown at all."
Garbage display: Old character data remained in the screen buffer and was visible through the popup, appearing as garbage.

Reproduction

call setline(1, 'This is line 1')
call setline(2, 'あいうえお')
call setline(3, '        かきくけこ')
hi MyPopup guibg=darkblue guifg=white
call popup_create(['FOO  BAR'], #{
\ line: 1,
\ col: 2,
\ minwidth: 15,
\ minheight: 3,
\ highlight: 'MyPopup',
\})

Before: The first character "あ" in line 2 shows only its left half (truncated). When adding spaces to line 3, garbage appears where the right half of "け" would be.

After: Characters are completely hidden when partially overlapped, and no garbage appears.

image.png (view on web)

Left half of あ must not be shown.

image.png (view on web)

Right half of "け" must be shown as a space.

Solution

In screen.c, when rendering wide characters that are partially blocked by a popup:

Clear both cells of the wide character in ScreenLines to prevent garbage
Only draw the cells that are not blocked by the popup
Skip drawing the entire wide character (set redraw_this = FALSE)

You can view, comment on, or merge this pull request online at:

https://github.com/vim/vim/pull/19271

Commit Summary

a870436 Fix wide character display with popups

File Changes

(1 file)

M src/screen.c (30)

Patch Links:

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mattn

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Jan 29, 2026, 3:59:02 AM (10 days ago) Jan 29

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@mattn pushed 1 commit.

813da06 Fix wide character display with popups

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vim-dev ML

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Jan 29, 2026, 4:15:30 AM (10 days ago) Jan 29

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vim-ml left a comment (vim/vim#19271)

> **Before**: The first character "あ" in line 2 shows only its left half (truncated). When adding spaces to line 3, garbage appears where the right half of "け" would be.
> **After**: Characters are completely hidden when partially overlapped, and no garbage appears.

ref: https://github.com/vim/vim/issues/9874

--
shane.xb.qian

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mattn

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Jan 30, 2026, 5:32:04 AM (9 days ago) Jan 30

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@mattn pushed 1 commit.

ce5fdd7 Fix wide character display with popups

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mattn

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Jan 30, 2026, 6:24:21 AM (9 days ago) Jan 30

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@mattn pushed 1 commit.

3feed02 Cosmetic changes

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mattn

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Jan 31, 2026, 8:59:13 AM (8 days ago) Jan 31

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mattn left a comment (vim/vim#19271)

This still wrong.

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mattn

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Jan 31, 2026, 12:10:59 PM (8 days ago) Jan 31

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@mattn pushed 3 commits.

330ca5a Fix wide character display with popups
5ea0cef revert
881447a skip redrawing second cell of wide char when blocked by popup

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mattn

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Jan 31, 2026, 12:15:21 PM (8 days ago) Jan 31

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mattn left a comment (vim/vim#19271)

I have identified what is happening and what needs to be fixed.

This issue has two problems.

This pull request fixes only one of them. When the left edge of the popup dialog overlaps the right half of a multibyte character, set the redraw_this flag to TRUE.

And the other issue, where the right side of the pop-up dialog is not rendered correctly,
is fixed in:
#19299

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mattn

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Feb 4, 2026, 3:14:14 AM (4 days ago) Feb 4

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@mattn pushed 3 commits.

a18ca89 Fix wide character display with popups
7120595 revert
d398f4b skip redrawing second cell of wide char when blocked by popup

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Christian Brabandt

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Feb 7, 2026, 4:35:08 PM (19 hours ago) Feb 7

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chrisbra left a comment (vim/vim#19271)