[vim/vim] Enable terminal reflow on resize (PR #19863)
mattn
Enable vterm_screen_enable_reflow() so that long lines in a terminal window reflow (re-wrap) when the terminal is resized. Added tests for both ASCII and multibyte (CJK) characters.
Fixes #2865
You can view, comment on, or merge this pull request online at:
https://github.com/vim/vim/pull/19863
Commit Summary
- 1409a06 Enable terminal reflow on resize
File Changes
(2 files)
- M src/terminal.c (1)
- M src/testdir/test_terminal2.vim (81)
Patch Links:
—
Reply to this email directly, view it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- 0cf96e6 Join continuation lines in Terminal-Normal mode buffer
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- 8604449 Fix reflow tests to not hardcode terminal row numbers
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
Cimbali
Cimbali left a comment (vim/vim#19863)This is nice but still missing the bit that also unwraps lines that have been scrolled out of the current viewport:
image.png (view on web)I am now at line 30 so line 18 reflowed nicely, but line 1 that wasn’t on-screen as the switch happened (already pushed into the scrollback buffer) is broken.
—
Reply to this email directly, view it on GitHub, or unsubscribe.
You are receiving this because you are subscribed to this thread.
mattn
mattn left a comment (vim/vim#19863)@Cimbali Thanks for testing! I just pushed a new commit that also joins continuation lines in the scrollback buffer (lines pushed off the top of the screen). This adds a vterm_screen_sb_pushline_continuation() accessor to libvterm so that handle_pushline can detect and join continuation lines when they're scrolled out of the viewport. Please try again with the latest commit.
—
Reply to this email directly, view it on GitHub, or unsubscribe.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- 9f0ea1a Join continuation lines in scrollback buffer
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
mattn left a comment (vim/vim#19863)I'll be looking for corner case bugs for a while, so it might not work for a short time. but I'll fix this soon.
—
Reply to this email directly, view it on GitHub, or unsubscribe.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- 5a4a6c0 Fix scrollback continuation detection for shifted lineinfo
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- f065b3b Fix unused variable warning in screen.c
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- 34ac747 Fix flaky Test_terminal_eof_arg on FreeBSD
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- 508e6f9 Fix multibyte reflow tests for FreeBSD
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- fe62c57 Fix multibyte reflow tests for macOS
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- febdb03 Remove multibyte reflow tests
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- 94f0775 Remove multibyte reflow tests
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
mattn
@mattn pushed 1 commit.
- b96a594 Use WaitForAssert for terminal output in reflow tests
—
View it on GitHub.
You are receiving this because you are subscribed to this thread.
Christian Brabandt
chrisbra left a comment (vim/vim#19863)How does this differ from #8365 ?
—
Reply to this email directly, view it on GitHub, or unsubscribe.
You are receiving this because you are subscribed to this thread.
mattn
mattn left a comment (vim/vim#19863)@chrisbra
I asked Claude Code about it. I haven’t verified whether the findings are correct.
PR #8365 vs PR #19863 Comparison
Both PRs fix the same issue #2865 — joining soft-wrapped (continuation) lines in the terminal buffer into single lines when switching to Normal mode.
Approach Differences
| #8365 (Cimbali) | #19863 (mattn) | |
|---|---|---|
| Started | June 2021 | March 2026 |
| libvterm changes | New sb_pushline4 callback + premove callback (coordinated with upstream author leonerd) |
New vterm_screen_sb_pushline_continuation() accessor function |
| ABI compatibility | Adds sb_pushline4 while keeping old sb_pushline (ABI-compatible) |
Calls vterm_screen_sb_pushline_continuation() from within existing sb_pushline callback |
| Reflow support | None (explicitly states resize reflow is not handled) | Enables vterm_screen_enable_reflow() (re-wraps on resize) |
| Files changed | 13 files | 6 files |
| Upstream coordination | leonerd implemented in upstream libvterm (rev 843) in July 2024 | No upstream coordination (custom extension) |
| Tests | libvterm tests + Vim tests | Vim tests only |
#8365 Strengths and Weaknesses
Strengths:
- Coordinated with upstream libvterm (leonerd), already merged as rev 843
premovecallback provides accurate continuation info when lines scroll out of the viewport- Includes libvterm-level tests
scrollbackline_pos_in_buf()/bufline_pos_in_scrollback()provide bidirectional mapping soterm_getline(),term_scrape(),term_get_attr()etc. work correctly with joined lines
Weaknesses:
- PR spans 5 years with complex code (large changeset across 13 files)
- Does not support reflow (re-wrapping on terminal resize)
- Must skip tests on Windows because
cmd.exedoes not emit continuation marks
#19863 Strengths and Weaknesses
Strengths:
- Simpler code (6 files, smaller changeset)
- Supports reflow on resize via
vterm_screen_enable_reflow() - Clean, modern implementation
Weaknesses:
- No upstream libvterm coordination — adds a custom
sb_pushline_continuationflag. Since #8365 already has an official upstream API (sb_pushline4) implemented by leonerd, this custom extension will conflict when syncing with upstream libvterm in the future - Scrollback handling may be incomplete — Cimbali pointed out in comments that lines already scrolled out of the viewport were not being joined. A follow-up commit addressed this, but #8365 more comprehensively fixes
term_getline(),term_scrape(),term_get_attr()and other functions that need to account for the line number offset caused by joining term_getline()andterm_scrape()fixes may be missing — #8365 uses scrollback-to-buffer mapping functions throughout multiple call sites, while #19863's coverage of these edge cases appears more limited
Overall Assessment
From a practical standpoint, #19863 is attractive for its simplicity and reflow support. However, from an upstream compatibility standpoint, #8365 has a clear advantage since leonerd already implemented the sb_pushline4 API in upstream libvterm. The custom extension in #19863 will cause issues when syncing Vim's libvterm fork with upstream in the future.
Ideally, the best approach would be to use #8365's upstream-coordinated libvterm changes as the base and combine them with #19863's reflow enablement. chrisbra also asked in #19863 "How does this differ from #8365?", indicating that reconciliation between the two PRs is needed.
—
Reply to this email directly, view it on GitHub, or unsubscribe.
You are receiving this because you are subscribed to this thread.