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fix(multicursor): skip insert live-mirror on conflicting edits #41730

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Problem:
Cursors placed same-line before the primary, or producing multiline
edits on lines above the primary, shift the text in a way that breaks
the insert-mode live-mirroring.

Solution:
Skip live-mirroring under those conditions.

TODO (future): we could support live-mirroring if ins-completion's
internal bookkeeping tracked its regions more precisely.
This commit is contained in:
Justin M. Keyes
2026-09-06 10:04:47 -04:00
committed by GitHub
parent 72bb23e18a
commit bd43394d4e
3 changed files with 151 additions and 59 deletions
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8
runtime/doc/repeat.txt
View File

@@ -444,9 +444,11 @@ cursor, then disables follow-mode again. >lua
LIMITATIONS *mcursor-limitations*
- Extra cursors on the same line can be lost or misplaced by an edit that
shifts columns (e.g. inserting text): the cursors shift each other.
- Undo restores the buffer, not (per-cursor) registers.
- During Insert-mode completion, live mirroring pauses if a preview could
shift or overlap the primary's completion (same-line edits before the
primary, or line insertions/deletions before it).
- Cursors on the same line can be lost or misplaced by an edit that shifts
columns (e.g. inserting text).
- Time-travel undo (|g-|, |g+|, |:earlier|) clears all cursors.
- Reloading/unloading a buffer (|:edit!|, 'autoread') clears its cursors
(extmarks limitation).

111
src/nvim/mcursor.c
View File

@@ -116,9 +116,8 @@ static struct {
size_t done_len; ///< Bytes of the capture already consumed by replayed spans; tail is pending.
varnumber_T tick; ///< b:changedtick at session start: the session's atoms (spans, the whole
///< session) diff against it for their `changed` field.
uint32_t region; ///< Extmark (pair) tracking the primary's inserted text.
kvec_t(uint32_t) regions; ///< Per-cursor extmarks (pairs, `mc_session_ns()`) tracking each
///< cursor's preview region (anchor .. preview end).
uint32_t region; ///< Primary cursor's inserted text.
kvec_t(uint32_t) regions; ///< Per-cursor preview regions (`mc_session_ns`).
} mc_ins_span;
/// Editor state when the mc session started, which every cursor replays against.
@@ -183,7 +182,7 @@ static uint32_t mc_last_ns(void)
return ns;
}
/// Namespace for session-internal marks (live text region, transient primary-cursor tracker).
/// Namespace for session-internal marks (live text regions, transient primary-cursor tracker).
static uint32_t mc_session_ns(void)
{
static uint32_t ns = 0;
@@ -710,7 +709,8 @@ static void mc_ins_preview_rebase(void)
}
/// First live per-cursor preview region, or `start.id == 0` if none. A live region's buffer
/// content is the applied preview text, and start == end means no preview is applied.
/// content is the applied preview text, and `start == end` means no preview is applied.
/// All live regions hold the same preview, so any one represents the batch.
static MTPair mc_ins_region_first(void)
{
for (size_t i = 0; i < kv_size(mc_ins_span.regions); i++) {
@@ -722,13 +722,25 @@ static MTPair mc_ins_region_first(void)
return (MTPair){ 0 };
}
/// The buffer range of paired region mark `p`.
/// The buffer range (start/end positions) of region mark `p`.
static void mc_region_range(MTPair p, pos_T *start, pos_T *end)
{
*start = (pos_T){ .lnum = p.start.pos.row + 1, .col = p.start.pos.col };
*end = (pos_T){ .lnum = p.end_pos.row + 1, .col = p.end_pos.col };
}
/// Resolves a session extmark to its buffer range (start/end). Returns false if the mark is gone
/// (deleted mid-session by a script?).
static bool mc_region_mark_range(uint32_t mark, pos_T *start, pos_T *end)
{
MTPair p = extmark_from_id(curbuf, mc_session_ns(), mark);
if (p.start.id == 0) {
return false;
}
mc_region_range(p, start, end);
return true;
}
/// Replaces buffer text (end-exclusive) with `text` (multiline), preserving marks and undo.
static void mc_ins_preview_replace(pos_T start, pos_T end, const String *text)
{
@@ -756,7 +768,7 @@ static void mc_ins_preview_replace(pos_T start, pos_T end, const String *text)
arena_mem_free(arena_finish(&arena));
}
/// Sets `text` as the preview at every cursor, replacing the previous one.
/// Sets the preview at every cursor, replacing the previous one.
static void mc_ins_preview_set(const String *new)
{
// The primary's own insert session must not notice the preview edits.
@@ -765,13 +777,12 @@ static void mc_ins_preview_set(const String *new)
uint32_t primary = 0;
mc_track_upd(curbuf, &primary, curwin->w_cursor);
for (size_t i = 0; i < kv_size(mc_ins_span.regions); i++) {
MTPair p = extmark_from_id(curbuf, mc_session_ns(), kv_A(mc_ins_span.regions, i));
if (p.start.id == 0) {
continue; // A script deleted the extmark mid-session.
pos_T rs, re;
// Re-resolve each region, previous loop iterations may have shifted it.
if (!mc_region_mark_range(kv_A(mc_ins_span.regions, i), &rs, &re)) {
continue;
}
// Cursor display mark (right-gravity) is pushed by the replacement to the new preview end.
pos_T rs, re;
mc_region_range(p, &rs, &re);
mc_ins_preview_replace(rs, re, new);
}
pos_T pos = curwin->w_cursor;
@@ -782,13 +793,6 @@ static void mc_ins_preview_set(const String *new)
mc_ins_restore_state(&saved);
}
/// Deletes the preview at every cursor.
static void mc_ins_preview_del(void)
{
static const String empty = STRING_INIT;
mc_ins_preview_set(&empty);
}
/// True if `keys` has a non-literal key (kKeyInsFlush): a literal preview cannot represent it.
static bool mc_ins_keys_nonliteral(const char *keys, size_t len)
{
@@ -819,7 +823,7 @@ void mc_ins_cascade_restart(void)
mc_ins_preview_rebase();
}
/// Insert-cascades the session. Called after each key in insert-mode; extends the preview or
/// Cascades the insert-session. Called after each key in insert-mode. Updates the preview or
/// flushes a span and cascades it.
void mc_ins_cascade(void)
{
@@ -827,8 +831,11 @@ void mc_ins_cascade(void)
|| !mc_buf_has_cursors(curbuf)) {
return;
}
pos_T start, end; // The primary cursor's insert-span region.
String ins = redo_keys(NULL);
assert(ins.data != NULL || ins.size == 0); // Coverity: NULL only when empty.
if (mc_ins_span.first) {
// Not with a pending autoindent ("o" + 'autoindent'): the entry span's replay ends in <Esc>,
// which would delete the indent.
@@ -853,28 +860,47 @@ void mc_ins_cascade(void)
if (!ins_compl_active() && !pum_visible()) {
mc_ins_span_flush(&ins, false);
}
} else {
MTPair p = extmark_from_id(curbuf, mc_session_ns(), mc_ins_span.region);
if (p.start.id != 0) {
pos_T rs, re;
mc_region_range(p, &rs, &re);
String text = ml_region_text(curbuf, rs, re);
// Skip the re-apply if the previews already hold this text (first live region == primary's).
bool applied = false;
MTPair fp = mc_ins_region_first();
if (fp.start.id != 0) {
pos_T frs, fre;
mc_region_range(fp, &frs, &fre);
String cur = ml_region_text(curbuf, frs, fre);
applied = cur.size == text.size
&& (text.size == 0 || memcmp(cur.data, text.data, text.size) == 0);
api_free_string(cur);
}
if (!applied) {
mc_ins_preview_set(&text);
}
api_free_string(text);
} else if (mc_region_mark_range(mc_ins_span.region, &start, &end)) {
// Live preview: mirror the primary's inserted text, without replay.
// Skip if unchanged, or if completion-preview could shift/overlap the primary's span.
String text = ml_region_text(curbuf, start, end);
bool update = true;
MTPair fp = mc_ins_region_first();
if (fp.start.id != 0) {
pos_T frs, fre;
mc_region_range(fp, &frs, &fre);
String cur = ml_region_text(curbuf, frs, fre);
// Preview-text changed?
update = cur.size != text.size
|| (text.size > 0 && memcmp(cur.data, text.data, text.size) != 0);
api_free_string(cur);
}
if (update && (ins_compl_active() || pum_visible())) {
// Completion active. check all cursor-preview regions; if one would disturb completion, defer
// (skip) the entire preview update (all-or-none: mc_ins_region_first() assumes all previews
// have the same text).
//
// TODO(justinmk): if completion positions (e.g. `compl_col`) followed extmarks, we wouldn't
// have this problem, and live-preview could allow (non-conflicting) text-shifts. #41719
for (size_t i = 0; i < kv_size(mc_ins_span.regions); i++) {
pos_T rs, re;
if (!mc_region_mark_range(kv_A(mc_ins_span.regions, i), &rs, &re)) {
continue;
}
// A preview after `end` is safe. Otherwise, multiline old or new preview text could shift
// the primary's rows.
if (!lt(end, rs) && (re.lnum >= start.lnum || rs.lnum != re.lnum
|| start.lnum != end.lnum)) {
update = false;
break;
}
}
}
if (update) {
mc_ins_preview_set(&text);
}
api_free_string(text);
}
api_free_string(ins);
}
@@ -887,10 +913,11 @@ void mc_ins_cascade(void)
/// session, and rebase for the continuing preview.
static void mc_ins_span_flush(const String *ins, bool commit)
{
static const String empty = STRING_INIT;
MTPair fp = mc_ins_region_first();
if (fp.start.id != 0
&& (fp.start.pos.row != fp.end_pos.row || fp.start.pos.col != fp.end_pos.col)) {
mc_ins_preview_del();
mc_ins_preview_set(&empty); // Delete the preview at every cursor.
}
size_t dlen = ins->size - mc_ins_span.done_len;
StringBuilder keys = KV_INITIAL_VALUE;

91
test/functional/editor/mcursor_spec.lua
View File

@@ -1031,7 +1031,7 @@ describe('multicursor', function()
end)
end)
describe('insert-mode cascade', function()
describe('insert-mode', function()
it('CTRL-U cascades before <Esc> (deletion crossing the session anchor)', function()
-- Deleting typed text cascades live (the region shrinks). But CTRL-U here eats the "o"
-- autoindent, which precedes the tracked region, invisible to the preview diff.
@@ -1265,12 +1265,10 @@ describe('multicursor', function()
end
eq({ { 'motion', '^' }, { 'insert', k('1i<Esc>') }, { 'insert', k('iX<Esc>') } }, children)
end)
end)
describe('insert-mode depth', function()
it('session survives all cursors deduping away mid-session', function()
-- A cursor at the primary's position: the "A" entry replay lands it on the primary and
-- dedupe removes it mid-session; the <Esc> commit must not cascade into the empty set.
-- "A" entry replay lands on the primary and dedupe removes it mid-session; the ESC commit
-- must not cascade into the empty set.
fn.setline(1, { 'x' })
feed('Q')
feed('Ahi<Esc>')
@@ -1278,7 +1276,7 @@ describe('multicursor', function()
eq({ 'xhi' }, get_lines())
end)
it('insert sessions cascade at each cursor', function()
it('sessions cascade at each cursor', function()
assert_rows({
-- iZ: after <Esc> the cursors sit ON the last inserted char (like the primary cursor).
{
@@ -1390,7 +1388,7 @@ describe('multicursor', function()
})
end)
it('ea appends at word end at each cursor (with q=)', function()
it('ea (with q=)', function()
cursors({ 'one two', 'three four' }, 'Qj')
feed('q=')
feed('ea!<Esc>')
@@ -1398,14 +1396,80 @@ describe('multicursor', function()
eq({ 'one! two', 'three! four' }, get_lines())
end)
it('i_CTRL-N completion result appears at each cursor', function()
fn.setline(1, { 'wombat', 'wo', 'wo' })
feed('2gg')
feed('Q')
feed('j')
it('completion: i_CTRL-N completes existing text at each cursor', function()
command('set completeopt=menuone')
cursors({ 'wombat', 'wo', 'wo' }, 'jQj')
feed('A<C-n><Esc>')
eq({ 'wombat', 'wombat', 'wombat' }, get_lines())
end)
it('completion: live-mirrors cursors on separate lines', function()
command('set completeopt=menuone')
cursors({ 'wombat', '', '' }, 'jQj')
feed('iwo<C-n>')
eq(1, fn.pumvisible())
eq({ 'wombat', 'wombat', 'wombat' }, get_lines())
feed('<Esc>')
eq({ 'wombat', 'wombat', 'wombat' }, get_lines())
end)
it('completion: ESC commits with stale previews #41719', function()
command('set completeopt=menuone,noselect')
cursors({ 'aa', 'bb cc dd', 'ee' }, 'GQkQww')
feed('ciwa<C-n>a')
eq(1, fn.pumvisible())
eq({ 'aa', 'a cc aa', 'a' }, get_lines())
feed('<Esc>')
eq({ 'aa', 'aa cc aa', 'aa' }, get_lines())
end)
it('completion: live-mirrors same-line cursor AFTER the primary', function()
command('set completeopt=menuone,noselect')
cursors({ 'aa', 'bb cc dd' }, 'jwwQ0')
feed('ciw<C-n>a')
eq(1, fn.pumvisible())
eq({ 'aa', 'a cc a' }, get_lines())
feed('<C-e>x<Esc>')
eq({ 'aa', 'ax cc ax' }, get_lines())
end)
it('completion: defers preview of multiline edit BEFORE primary #41719', function()
command('set completeopt=menuone')
cursors({ '', '' }, 'Qj')
feed('ia')
fn.complete(1, { 'aa\nbb', 'ac' })
eq(1, fn.pumvisible())
eq({ 'a', 'aa', 'bb' }, get_lines())
feed('<C-c>')
end)
it('completion: defers preview of same-line cursor BEFORE primary #41719', function()
command('set completeopt=menu,noselect')
-- Place cursor1 on its own line, to exercise whole-batch deferral.
-- Place cursor2 on same line as the primary, to test same-line handling.
for _, case in ipairs({
{ 'aa', 'aa', '' },
{ 'a<C-e>', 'a', 'a' },
{ 'a<C-n><C-y>', 'aa', 'aa' },
{ 'a<BS>a', 'a', 'a' },
}) do
local keys, text, preview = unpack(case)
clear_cursors()
cursors({ 'aa', 'bb cc dd', 'ee' }, 'GQkQww')
eq({ { 1, 0 }, { 2, 0 } }, anchors())
eq({ 2, 6 }, api.nvim_win_get_cursor(0))
feed('ciw<C-n>')
eq(1, fn.pumvisible())
feed(keys)
eq({ 'aa', ('%s cc %s'):format(preview, text), preview }, get_lines())
feed('aa')
eq(0, fn.pumvisible())
feed(' ')
eq({ 'aa', ('%saa cc %saa '):format(text, text), ('%saa '):format(text) }, get_lines())
feed('x<Esc>')
eq({ 'aa', ('%saa x cc %saa x'):format(text, text), ('%saa x'):format(text) }, get_lines())
end
end)
end)
describe('navigation state (primary-only)', function()
@@ -1438,8 +1502,7 @@ describe('multicursor', function()
describe('completion', function()
-- While a completion is active, the cascade pauses: redobuff is frozen, and spans cannot replay
-- into a busy completion (edit() refuses recursive insert). The other cursors catch up when the
-- completion ends.
-- into a busy completion (edit() refuses nesting). The cursors catch up when completion ends.
--- Three empty lines under "foo*" completion candidates; cursors on lines 4-5, primary on 6.
local function ac_setup()