neovim

commit f8b50bf3b0f68af98f5012fa73f7d2425137310b
parent 0fca343d641c25f631a5125801d5cb3996e29f7c
Author: zeertzjq <zeertzjq@outlook.com>
Date:   Sat,  4 Oct 2025 20:08:28 +0800

vim-patch:9.1.1825: completion: flicker when LSP server is slow (#36020)

Problem:  completion: flicker when LSP server is slow
Solution: reinsert leader text before invoking user function
          (Girish Palya)

Reference:
https://github.com/girishji/vimcomplete/issues/101#issuecomment-3343063245

In insert-mode completion, the leader text is temporarily removed while
searching for candidates. When the LSP server responds slowly, the
client may call `:sleep` to wait, which triggers `out_flush()`. This
causes the deleted text to disappear briefly before being redrawn,
resulting in visible flicker.

This commit reinserts the leader text before invoking the user function,
and removes it again afterward to eliminate flicker.

closes: vim/vim#18468

https://github.com/vim/vim/commit/c51d1cc578da32939ee458e98d78b180e1235b4b

Co-authored-by: Girish Palya <girishji@gmail.com>
Diffstat:
M
src/nvim/insexpand.c
 | 
17
+++++++++++++++--
M
test/old/testdir/test_ins_complete.vim
 | 
27
+++++++++++++--------------

2 files changed, 28 insertions(+), 16 deletions(-)
diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
@@ -6544,16 +6544,29 @@ static void remove_old_matches(void)
 /// 'refresh:always' flag.
 static void get_cpt_func_completion_matches(Callback *cb)
 {
-  int startcol = cpt_sources_array[cpt_sources_index].cs_startcol;
+  cpt_source_T *cpt_src = &cpt_sources_array[cpt_sources_index];
+  int startcol = cpt_src->cs_startcol;
 
   if (startcol == -2 || startcol == -3) {
     return;
   }
 
   set_compl_globals(startcol, curwin->w_cursor.col, true);
+
+  // Insert the leader string (previously removed) before expansion.
+  // This prevents flicker when `func` (e.g. an LSP client) is slow and
+  // calls 'sleep', which triggers ui_flush().
+  if (!cpt_src->cs_refresh_always) {
+    ins_compl_insert_bytes(ins_compl_leader(), -1);
+  }
+
   expand_by_function(0, cpt_compl_pattern.data, cb);
 
-  cpt_sources_array[cpt_sources_index].cs_refresh_always = compl_opt_refresh_always;
+  if (!cpt_src->cs_refresh_always) {
+    ins_compl_delete(false);
+  }
+
+  cpt_src->cs_refresh_always = compl_opt_refresh_always;
   compl_opt_refresh_always = false;
 }
 
diff --git a/test/old/testdir/test_ins_complete.vim b/test/old/testdir/test_ins_complete.vim
@@ -591,15 +591,19 @@ func Test_completefunc_info()
   set completefunc&
 endfunc
 
-func Test_cpt_func_cursorcol()
+" For ^N completion, `completefunc` receives the same leader string in both the
+" 'info' and 'expansion' phases (the leader is not removed before expansion).
+" This avoids flicker when `completefunc` (e.g. an LSP client) is slow and calls
+" 'sleep', which triggers out_flush().
+func Test_completefunc_leader()
   func CptColTest(findstart, query)
     if a:findstart
-      call assert_equal(b:info_compl_line, getline(1))
-      call assert_equal(b:info_cursor_col, col('.'))
+      call assert_equal(b:compl_line, getline(1))
+      call assert_equal(b:cursor_col, col('.'))
       return col('.')
     endif
-    call assert_equal(b:expn_compl_line, getline(1))
-    call assert_equal(b:expn_cursor_col, col('.'))
+    call assert_equal(b:compl_line, getline(1))
+    call assert_equal(b:cursor_col, col('.'))
     " return v:none
     return []
   endfunc
@@ -608,17 +612,13 @@ func Test_cpt_func_cursorcol()
   new
 
   " Replace mode
-  let b:info_compl_line = "foo barxyz"
-  let b:expn_compl_line = "foo barbaz"
-  let b:info_cursor_col = 10
-  let b:expn_cursor_col = 5
+  let b:compl_line = "foo barxyz"
+  let b:cursor_col = 10
   call feedkeys("ifoo barbaz\<Esc>2hRxy\<C-N>", "tx")
 
   " Insert mode
-  let b:info_compl_line = "foo bar"
-  let b:expn_compl_line = "foo "
-  let b:info_cursor_col = 8
-  let b:expn_cursor_col = 5
+  let b:compl_line = "foo bar"
+  let b:cursor_col = 8
   call feedkeys("Sfoo bar\<C-N>", "tx")
 
   set completeopt=longest
@@ -4239,7 +4239,6 @@ func Test_autocomplete_completeopt_preinsert()
   endfunc
   set omnifunc=Omni_test complete+=o
   set completeopt=preinsert autocomplete
-  " set completeopt=preinsert,menuone autocomplete
   func GetLine()
     let g:line = getline('.')
     let g:col = col('.')