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patch 9.1.1812: completion: flicker with slow LSPs

Problem:  completion: flicker with slow LSPs
Solution: Disable flushing the changed text (Girish Palya).

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

There are two possible fixes:

1. Suppress flushing while a user function (e.g. LSP client) is waiting.
2. Reinsert the deleted text before invoking the user function.

This Commit implements (1), which is the simpler solution, though somewhat
heavy-handed. If you think this may introduce unwanted side effects, I
can rework it to use (2).

closes: #18439

Signed-off-by: Girish Palya <girishji@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
This commit is contained in:
Girish Palya
2025-09-29 20:56:06 +00:00
committed by Christian Brabandt
parent 8f214168bd
commit 71b97f2905
5 changed files with 19 additions and 5 deletions

View File

@@ -1133,6 +1133,9 @@ EXTERN int secure INIT(= FALSE);
// allowed, e.g. when sourcing .exrc or .vimrc
// in current directory
EXTERN int no_flush INIT(= 0);
// non-zero to prevent flushing output buffer
EXTERN int textlock INIT(= 0);
// non-zero when changing text and jumping to
// another window or editing another buffer is

View File

@@ -3601,8 +3601,18 @@ expand_by_function(int type, char_u *base, callback_T *cb)
// Insert mode in another buffer.
++textlock;
// Suppress flushing of the output buffer. Without this, text removed
// temporarily by ins_compl_delete() is flushed to the terminal and shown
// as deleted, only to be redrawn later. This causes visible flicker (typed
// chars disappear and reappear) when a user func (e.g. an LSP server)
// responds slowly. Such funcs may call sleep(), which indirectly triggers
// out_flush(). We want deleted text to remain visible.
++no_flush;
retval = call_callback(cb, 0, &rettv, 2, args);
--no_flush;
// Call a function, which returns a list or dict.
if (retval == OK)
{
@@ -6093,7 +6103,6 @@ find_next_completion_match(
int compl_fuzzy_match = (cur_cot_flags & COT_FUZZY) != 0;
string_T *leader;
while (--todo >= 0)
{
if (compl_shows_dir_forward() && compl_shown_match->cp_next != NULL)
@@ -6203,7 +6212,7 @@ find_next_completion_match(
*
* Note that this function may be called recursively once only. First with
* "allow_get_expansion" TRUE, which calls ins_compl_get_exp(), which in turn
* calls this function with "allow_get_expansion" FALSE.
* calls this with "allow_get_expansion" FALSE (via ins_compl_check_keys()).
*/
static int
ins_compl_next(

View File

@@ -2772,7 +2772,7 @@ out_flush(void)
{
int len;
if (out_pos == 0)
if (no_flush > 0 || out_pos == 0)
return;
// set out_pos to 0 before ui_write, to avoid recursiveness

View File

@@ -420,7 +420,7 @@ func Test_CompleteDoneDict()
au CompleteDone * :call <SID>CompleteDone_CheckCompletedItemDict(0)
set complete=.,F<SID>CompleteDone_CompleteFuncDict
execute "normal a\<C-N>\<C-Y>"
execute "normal dda\<C-N>\<C-Y>"
set complete&
call assert_equal(['one', 'two'], v:completed_item[ 'user_data' ])
@@ -473,7 +473,7 @@ func Test_CompleteDoneDictNoUserData()
let s:called_completedone = 0
set complete=.,F<SID>CompleteDone_CompleteFuncDictNoUserData
execute "normal a\<C-N>\<C-Y>"
execute "normal dda\<C-N>\<C-Y>"
set complete&
call assert_equal('', v:completed_item[ 'user_data' ])

View File

@@ -729,6 +729,8 @@ static char *(features[]) =
static int included_patches[] =
{ /* Add new patch number below this line */
/**/
1812,
/**/
1811,
/**/