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* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
@ 2019-11-01 21:40 Kévin Le Gouguec
  2019-11-01 23:28 ` João Távora
  0 siblings, 1 reply; 8+ messages in thread
From: Kévin Le Gouguec @ 2019-11-01 21:40 UTC (permalink / raw)
  To: 38024; +Cc: João Távora

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Hello,

tl;dr unless I'm mistaken, sometimes `while-no-input' returns t despite
no input having arrived; this prevents `icomplete-exhibit' from
displaying completion candidates.

In more details:

This is a bit of a heisenbug; hopefully someone out there will know what
knobs to tweak to find more information about this.

From emacs -Q:

    M-x icomplete-mode RET
    ;; Find a way to set `default-directory' to some long-ish path,
    ;; e.g. with:
    M-x find-library RET icomplete RET
    C-x C-f
    ;; icomplete should show a bunch of completions.
    M-DEL
    M-DEL
    …

After each `backward-kill-word', icomplete usually displays new
completion candidates with no further user input; sometimes however, no
candidates show up until the user does something (e.g. press TAB or
start typing).

Commit 5860fd3 (Make icomplete-exhibit actually work when navigating up
directories) tried to fix this, but AFAICT it merely reduces the odds of
the bug happening: I can still reproduce it, although less often.  Also,
this new call to `redisplay' causes some noticeable flickering when
typing characters: the completions blink in and out as I fill in the
prompt.

I've tinkered with icomplete.el (commenting out the call to `redisplay'
since it makes the bug harder to trigger); the closest I got to
pin-pointing the cause for this issue was while goofing around in
`icomplete-exhibit', specifically with the `while-no-input' part:

          (let* (…
                 (text (while-no-input
                         (icomplete-completions
                          …)))
                 …)
            ;; Do nothing if while-no-input was aborted.
            (when (stringp text)
              update overlay…))

I replaced (when (stringp text) …) with (if (stringp text) (progn …)
(message "text is %s" text)): it seems that text is t when icomplete
fails to show updated candidates, which according to `while-no-input'
means that some input arrived…

However, when I tried to debug `while-no-input', I got stumped: I tried
to do some more printf-debugging[1], but all I observe is that
sometimes, the code seems to be interrupted between

	 (let ((throw-on-input ',catch-sym)
               val)
and
           (setq val (or (input-pending-p)
	                 (progn ,@body)))

I tried to find where exactly the code gets interrupted, but I could not
get a consistent answer; sometimes it seems to be before executing body,
sometimes it seems to be somewhere inside `icomplete-completions'…

What would be the best way to investigate this further?

Thank you for your time.


[1] With this patch:


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: icomplete-debug.patch --]
[-- Type: text/x-diff, Size: 3410 bytes --]

diff --git a/lisp/icomplete.el b/lisp/icomplete.el
index 02eae55a19..31023d5644 100644
--- a/lisp/icomplete.el
+++ b/lisp/icomplete.el
@@ -399,8 +399,6 @@ icomplete-exhibit
 See `icomplete-mode' and `minibuffer-setup-hook'."
   (when (and icomplete-mode
              (icomplete-simple-completing-p)) ;Shouldn't be necessary.
-    (redisplay)     ; FIXME: why is this sometimes needed when moving
-                    ; up dirs in a file-finding table?
     (save-excursion
       (goto-char (point-max))
                                         ; Insert the match-status information:
@@ -430,13 +428,15 @@ icomplete-exhibit
                  (buffer-undo-list t)
                  deactivate-mark)
 	    ;; Do nothing if while-no-input was aborted.
-            (when (stringp text)
-              (move-overlay icomplete-overlay (point) (point) (current-buffer))
-              ;; The current C cursor code doesn't know to use the overlay's
-              ;; marker's stickiness to figure out whether to place the cursor
-              ;; before or after the string, so let's spoon-feed it the pos.
-              (put-text-property 0 1 'cursor t text)
-              (overlay-put icomplete-overlay 'after-string text)))))))
+            (if (stringp text)
+                (progn
+                  (move-overlay icomplete-overlay (point) (point) (current-buffer))
+                  ;; The current C cursor code doesn't know to use the overlay's
+                  ;; marker's stickiness to figure out whether to place the cursor
+                  ;; before or after the string, so let's spoon-feed it the pos.
+                  (put-text-property 0 1 'cursor t text)
+                  (overlay-put icomplete-overlay 'after-string text))
+              (message "text is %s" text)))))))
 
 ;;;_ > icomplete-completions (name candidates predicate require-match)
 (defun icomplete-completions (name candidates predicate require-match)
diff --git a/lisp/subr.el b/lisp/subr.el
index b408ef0931..3610fe30f2 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3727,11 +3727,14 @@ while-no-input
   (declare (debug t) (indent 0))
   (let ((catch-sym (make-symbol "input")))
     `(with-local-quit
+       (message "after with-local-quit")
        (catch ',catch-sym
 	 (let ((throw-on-input ',catch-sym)
                val)
+           (message "after catch and let")
            (setq val (or (input-pending-p)
 	                 (progn ,@body)))
+           (message "after setq val")
            (cond
             ;; When input arrives while throw-on-input is non-nil,
             ;; kbd_buffer_store_buffered_event sets quit-flag to the
@@ -3746,13 +3749,17 @@ while-no-input
             ;; such as discarding input etc.  We return t in that case
             ;; because input did arrive during execution of BODY.
             ((eq quit-flag throw-on-input)
+             (message "cond: got input")
              (setq quit-flag nil)
              t)
             ;; This is for when the user actually QUITs during
             ;; execution of BODY.
             (quit-flag
+             (message "cond: got quit-flag %s" quit-flag)
              nil)
-            (t val)))))))
+            (t
+             (message "cond: return val")
+             val)))))))
 
 (defmacro condition-case-unless-debug (var bodyform &rest handlers)
   "Like `condition-case' except that it does not prevent debugging.

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When the bug happens, I get the following messages:

    after with-local-quit
    after catch and let
    text is t


PS: It just occured to me that I should search debbugs for
    "while-no-input" in addition to "icomplete".  I just did that;
    bug#15042 looks like it could maybe be related?


In GNU Emacs 27.0.50 (build 6, i686-pc-linux-gnu, GTK+ Version 3.24.5, cairo version 1.16.0)
 of 2019-10-21 built on little-buster
Repository revision: 61fb5214816ef3d57e676d900e499ffcd079a1f9
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)

Configured using:
 'configure --with-xwidgets --with-cairo'

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS XWIDGETS
LIBSYSTEMD JSON PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

^ permalink raw reply	[flat|nested] 8+ messages in thread

* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
  2019-11-01 21:40 bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words Kévin Le Gouguec
@ 2019-11-01 23:28 ` João Távora
  2019-11-02  3:05   ` João Távora
  0 siblings, 1 reply; 8+ messages in thread
From: João Távora @ 2019-11-01 23:28 UTC (permalink / raw)
  To: Kévin Le Gouguec; +Cc: 38024, monnier

[-- Attachment #1: Type: text/plain, Size: 4376 bytes --]

Kevin, you're on the right track. The redisplay thing is not the right fix,
indeed. Stefan has a fix for this, which he sent me, but I can't find it
now.

Anyway, it has to do with avoiding the 'select' event in while-no-input.

In case you want to try that before Stefan drops by.

João

On Fri, Nov 1, 2019, 21:40 Kévin Le Gouguec <kevin.legouguec@gmail.com>
wrote:

> Hello,
>
> tl;dr unless I'm mistaken, sometimes `while-no-input' returns t despite
> no input having arrived; this prevents `icomplete-exhibit' from
> displaying completion candidates.
>
> In more details:
>
> This is a bit of a heisenbug; hopefully someone out there will know what
> knobs to tweak to find more information about this.
>
> From emacs -Q:
>
>     M-x icomplete-mode RET
>     ;; Find a way to set `default-directory' to some long-ish path,
>     ;; e.g. with:
>     M-x find-library RET icomplete RET
>     C-x C-f
>     ;; icomplete should show a bunch of completions.
>     M-DEL
>     M-DEL
>     …
>
> After each `backward-kill-word', icomplete usually displays new
> completion candidates with no further user input; sometimes however, no
> candidates show up until the user does something (e.g. press TAB or
> start typing).
>
> Commit 5860fd3 (Make icomplete-exhibit actually work when navigating up
> directories) tried to fix this, but AFAICT it merely reduces the odds of
> the bug happening: I can still reproduce it, although less often.  Also,
> this new call to `redisplay' causes some noticeable flickering when
> typing characters: the completions blink in and out as I fill in the
> prompt.
>
> I've tinkered with icomplete.el (commenting out the call to `redisplay'
> since it makes the bug harder to trigger); the closest I got to
> pin-pointing the cause for this issue was while goofing around in
> `icomplete-exhibit', specifically with the `while-no-input' part:
>
>           (let* (…
>                  (text (while-no-input
>                          (icomplete-completions
>                           …)))
>                  …)
>             ;; Do nothing if while-no-input was aborted.
>             (when (stringp text)
>               update overlay…))
>
> I replaced (when (stringp text) …) with (if (stringp text) (progn …)
> (message "text is %s" text)): it seems that text is t when icomplete
> fails to show updated candidates, which according to `while-no-input'
> means that some input arrived…
>
> However, when I tried to debug `while-no-input', I got stumped: I tried
> to do some more printf-debugging[1], but all I observe is that
> sometimes, the code seems to be interrupted between
>
>          (let ((throw-on-input ',catch-sym)
>                val)
> and
>            (setq val (or (input-pending-p)
>                          (progn ,@body)))
>
> I tried to find where exactly the code gets interrupted, but I could not
> get a consistent answer; sometimes it seems to be before executing body,
> sometimes it seems to be somewhere inside `icomplete-completions'…
>
> What would be the best way to investigate this further?
>
> Thank you for your time.
>
>
> [1] With this patch:
>
>
> When the bug happens, I get the following messages:
>
>     after with-local-quit
>     after catch and let
>     text is t
>
>
> PS: It just occured to me that I should search debbugs for
>     "while-no-input" in addition to "icomplete".  I just did that;
>     bug#15042 looks like it could maybe be related?
>
>
> In GNU Emacs 27.0.50 (build 6, i686-pc-linux-gnu, GTK+ Version 3.24.5,
> cairo version 1.16.0)
>  of 2019-10-21 built on little-buster
> Repository revision: 61fb5214816ef3d57e676d900e499ffcd079a1f9
> Repository branch: master
> Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
> System Description: Debian GNU/Linux 10 (buster)
>
> Configured using:
>  'configure --with-xwidgets --with-cairo'
>
> Configured features:
> XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB NOTIFY
> INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
> ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS XWIDGETS
> LIBSYSTEMD JSON PDUMPER LCMS2 GMP
>
> Important settings:
>   value of $LANG: en_US.UTF-8
>   locale-coding-system: utf-8-unix
>

[-- Attachment #2: Type: text/html, Size: 5290 bytes --]

^ permalink raw reply	[flat|nested] 8+ messages in thread

* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
  2019-11-01 23:28 ` João Távora
@ 2019-11-02  3:05   ` João Távora
  2019-11-02  7:37     ` Eli Zaretskii
  0 siblings, 1 reply; 8+ messages in thread
From: João Távora @ 2019-11-02  3:05 UTC (permalink / raw)
  To: Kévin Le Gouguec; +Cc: 38024, Stefan Monnier

João Távora <joaotavora@gmail.com> writes:

> Kevin, you're on the right track. The redisplay thing is not the right
> fix, indeed. Stefan has a fix for this, which he sent me, but I can't
> find it now.
>
> Anyway, it has to do with avoiding the 'select' event in
> while-no-input.

Hi Kévin,

In the meantime, I found the patch and pushed it right away.  It worked
better than the redisplay hack I had pushed before.

The commit you want to test with is
730e7da7ba6a4b545176ea246653928edb10cff4

Let me know how it works for you,
João





^ permalink raw reply	[flat|nested] 8+ messages in thread

* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
  2019-11-02  3:05   ` João Távora
@ 2019-11-02  7:37     ` Eli Zaretskii
  2019-11-02 11:12       ` João Távora
  0 siblings, 1 reply; 8+ messages in thread
From: Eli Zaretskii @ 2019-11-02  7:37 UTC (permalink / raw)
  To: João Távora; +Cc: 38024, monnier, kevin.legouguec

> From: João Távora <joaotavora@gmail.com>
> Date: Sat, 02 Nov 2019 03:05:17 +0000
> Cc: 38024@debbugs.gnu.org, Stefan Monnier <monnier@iro.umontreal.ca>
> 
> João Távora <joaotavora@gmail.com> writes:
> 
> > Kevin, you're on the right track. The redisplay thing is not the right
> > fix, indeed. Stefan has a fix for this, which he sent me, but I can't
> > find it now.
> >
> > Anyway, it has to do with avoiding the 'select' event in
> > while-no-input.
> 
> Hi Kévin,
> 
> In the meantime, I found the patch and pushed it right away.  It worked
> better than the redisplay hack I had pushed before.
> 
> The commit you want to test with is
> 730e7da7ba6a4b545176ea246653928edb10cff4

The current master displays this warning when byte-compiling
icomplete.el:

    ELC      icomplete.elc

  In end of data:
  icomplete.el:669:1:Warning: the function `while-no-input-ignore-events' is not
      known to be defined.

while-no-input-ignore-events is not a function, it's a variable.





^ permalink raw reply	[flat|nested] 8+ messages in thread

* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
  2019-11-02  7:37     ` Eli Zaretskii
@ 2019-11-02 11:12       ` João Távora
  2019-11-02 13:07         ` Eli Zaretskii
  2021-04-05 20:59         ` Stefan Monnier
  0 siblings, 2 replies; 8+ messages in thread
From: João Távora @ 2019-11-02 11:12 UTC (permalink / raw)
  To: Eli Zaretskii; +Cc: 38024, monnier, kevin.legouguec

Eli Zaretskii <eliz@gnu.org> writes:

>   In end of data:
>   icomplete.el:669:1:Warning: the function `while-no-input-ignore-events' is not
>       known to be defined.
>
> while-no-input-ignore-events is not a function, it's a variable.

Sorry,

This was a merge blunder when reordering commits. The reference appears
again in the corrct variable form below.  I've now fixed the problem in
6911ef3da69333cb7adc1a7fb0a0fc001220a0c4.

João





^ permalink raw reply	[flat|nested] 8+ messages in thread

* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
  2019-11-02 11:12       ` João Távora
@ 2019-11-02 13:07         ` Eli Zaretskii
  2019-11-03 10:25           ` Kévin Le Gouguec
  2021-04-05 20:59         ` Stefan Monnier
  1 sibling, 1 reply; 8+ messages in thread
From: Eli Zaretskii @ 2019-11-02 13:07 UTC (permalink / raw)
  To: João Távora; +Cc: 38024, monnier, kevin.legouguec

> From: João Távora <joaotavora@gmail.com>
> Cc: kevin.legouguec@gmail.com,  38024@debbugs.gnu.org,
>   monnier@iro.umontreal.ca
> Date: Sat, 02 Nov 2019 11:12:07 +0000
> 
> > while-no-input-ignore-events is not a function, it's a variable.
> 
> Sorry,
> 
> This was a merge blunder when reordering commits. The reference appears
> again in the corrct variable form below.  I've now fixed the problem in
> 6911ef3da69333cb7adc1a7fb0a0fc001220a0c4.

Thanks, compiles cleanly now.





^ permalink raw reply	[flat|nested] 8+ messages in thread

* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
  2019-11-02 13:07         ` Eli Zaretskii
@ 2019-11-03 10:25           ` Kévin Le Gouguec
  0 siblings, 0 replies; 8+ messages in thread
From: Kévin Le Gouguec @ 2019-11-03 10:25 UTC (permalink / raw)
  To: Eli Zaretskii; +Cc: 38024-done, João Távora, monnier

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks, compiles cleanly now.

And AFAICT, everything's fine now!  (Completions show up no matter how
many M-DELs I hit; no more flickering when typing.)

Thank you all for working on this; closing (if I'm reading
admin/notes/bugtracker correctly).






^ permalink raw reply	[flat|nested] 8+ messages in thread

* bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words
  2019-11-02 11:12       ` João Távora
  2019-11-02 13:07         ` Eli Zaretskii
@ 2021-04-05 20:59         ` Stefan Monnier
  1 sibling, 0 replies; 8+ messages in thread
From: Stefan Monnier @ 2021-04-05 20:59 UTC (permalink / raw)
  To: João Távora; +Cc: Daniel Mendler, 38024, kevin.legouguec

[ Resending, as usual, since the bug was archived.  Sorry.  ]

João Távora [2019-11-02 11:12:07] wrote:
> Eli Zaretskii <eliz@gnu.org> writes:
>>   In end of data:
>>   icomplete.el:669:1:Warning: the function `while-no-input-ignore-events' is not
>>       known to be defined.
>> while-no-input-ignore-events is not a function, it's a variable.
> Sorry,
> This was a merge blunder when reordering commits. The reference appears
> again in the corrct variable form below.  I've now fixed the problem in
> 6911ef3da69333cb7adc1a7fb0a0fc001220a0c4.

Hmm... so the patch installed was basically:

    commit 88f193ed05649b8c622867b8b2623b8cb08fdc96
    Author: João Távora <joaotavora@gmail.com>
    Date:   Sat Nov 2 02:29:56 2019 +0000
    
        Improve fix for icomplete's backward-kill-word bug#38024
        
        * lisp/icomplete.el (icomplete-exhibit): Use
        while-no-input-ignore-events, not redisplay.
        
        Co-authored-by: Stefan Monnier <j.schmoe@example.org>
    
    diff --git a/lisp/icomplete.el b/lisp/icomplete.el
    index 02eae55a19..89318ca4c7 100644
    --- a/lisp/icomplete.el
    +++ b/lisp/icomplete.el
    @@ -399,8 +399,6 @@ icomplete-exhibit
     See `icomplete-mode' and `minibuffer-setup-hook'."
       (when (and icomplete-mode
                  (icomplete-simple-completing-p)) ;Shouldn't be necessary.
    -    (redisplay)     ; FIXME: why is this sometimes needed when moving
    -                    ; up dirs in a file-finding table?
         (save-excursion
           (goto-char (point-max))
                                             ; Insert the match-status information:
    @@ -420,6 +418,11 @@ icomplete-exhibit
                    ;; embarking on computing completions:
                    (sit-for icomplete-compute-delay)))
              (let* ((field-string (icomplete--field-string))
    +                 ;; Not sure why, but such requests seem to come
    +                 ;; every once in a while.  It's not fully
    +                 ;; deterministic but `C-x C-f M-DEL M-DEL ...'
    +                 ;; seems to trigger it fairly often!
    +                 (while-no-input-ignore-events '(selection-request))
                      (text (while-no-input
                              (icomplete-completions
                               field-string

but I don't understand why that would help and/or be needed:
`selection-request` is (and has been for many years) in the default
value of `while-no-input-ignore-events` (as set in `subr.el`), so what
this patch ends up doing is forcing `while-no-input` to exit with value
t in more cases (i.e. whenever one of the events in (focus-in focus-out
help-echo iconify-frame make-frame-visible) comes in) rather than
the opposite.

What am I missing?


        Stefan






^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2021-04-05 20:59 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-01 21:40 bug#38024: 27.0.50; icomplete sometimes fails to show completions after backward-killing words Kévin Le Gouguec
2019-11-01 23:28 ` João Távora
2019-11-02  3:05   ` João Távora
2019-11-02  7:37     ` Eli Zaretskii
2019-11-02 11:12       ` João Távora
2019-11-02 13:07         ` Eli Zaretskii
2019-11-03 10:25           ` Kévin Le Gouguec
2021-04-05 20:59         ` Stefan Monnier

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