bug#45292: 28.0.50; first key typed ignores current input method (in magit commit buffer)

bug#45292: 28.0.50; first key typed ignores current input method (in magit commit buffer)

[Platon Pronko]

Minimal init.el for problem reproduction:

(define-minor-mode dvorak-minor-mode "Use english-dvorak input method." :lighter nil
   (if dvorak-minor-mode (activate-input-method "english-dvorak")))
(define-global-minor-mode global-dvorak-mode dvorak-minor-mode dvorak-minor-mode)
(global-dvorak-mode t)

(require 'magit)
(global-set-key (kbd "C-x g") 'magit-status)

I do not know how to make elpa packages load under -Q, unfortunately.

Steps to reproduce:
1. Set up a git repository with a staged change (mkdir test-repo; cd test-repo; git init; touch a; git add a);
2. Launch emacs (GUI) in this directory;
3. Type "C-x g" (or execute magit-status);
4. Type "c c" to open commit buffer;
5. Type "j j" (or any two characters that are different between english and english-dvorak input methods);
6. Observe that inserted characters are different - first one uses the default input method ("j") and second one uses the configured one ("h").

I bisected the problem and found that it was introduced in commit adbb4eacc (on 2020-12-12, by Stefan Monnier).

I'll try looking into the cause now, but will appreciate any pointers (it seems to be touching keyboard.c, and I remember it to be very complex).



In GNU Emacs 28.0.50 (build 14, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo version 1.17.4)
  of 2020-12-17 built on the-big-maker
Repository revision: adbb4eacc2a984c0fc0b65ec761368fd9067d6c5
Repository branch: HEAD
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Arch Linux

Configured using:
  'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
  --localstatedir=/var --mandir=/usr/share/man --with-gameuser=:games
  --with-sound=alsa --with-modules --without-gconf --without-gsettings
  --with-x-toolkit=gtk3 --without-xaw3d'

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

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

Major mode: SQL[ANSI]

Minor modes in effect:
   magit-auto-revert-mode: t
   auto-revert-mode: t
   global-git-commit-mode: t
   async-bytecomp-package-mode: t
   shell-dirtrack-mode: t
   global-dvorak-mode: t
   dvorak-minor-mode: t
   tooltip-mode: t
   global-eldoc-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   line-number-mode: t
   transient-mark-mode: t

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/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-format hides /usr/share/emacs/site-lisp/cider-format
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/home/platon/.emacs.d/elpa/a-20201203.1927/a hides /usr/share/emacs/site-lisp/a
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-profile hides /usr/share/emacs/site-lisp/cider-profile
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-selector hides /usr/share/emacs/site-lisp/cider-selector
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-client hides /usr/share/emacs/site-lisp/cider-client
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-scratch hides /usr/share/emacs/site-lisp/cider-scratch
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-repl-history hides /usr/share/emacs/site-lisp/cider-repl-history
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-find hides /usr/share/emacs/site-lisp/cider-find
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/home/platon/.emacs.d/elpa/cider-20201210.1748/nrepl-dict hides /usr/share/emacs/site-lisp/nrepl-dict
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/home/platon/.emacs.d/elpa/protobuf-mode-20200619.1742/protobuf-mode hides /usr/share/emacs/site-lisp/protobuf-mode
/home/platon/.emacs.d/elpa/parseclj-20201012.712/parseclj-lex hides /usr/share/emacs/site-lisp/parseclj-lex
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-mode hides /usr/share/emacs/site-lisp/cider-mode
/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-xref hides /usr/share/emacs/site-lisp/cider-xref
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/home/platon/.emacs.d/elpa/cider-20201210.1748/cider-browse-spec hides /usr/share/emacs/site-lisp/cider-browse-spec
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dynamic-setting font-render-setting cairo move-toolbar gtk x-toolkit x
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Memory information:
((conses 16 142677 11960)
  (symbols 48 14644 1)
  (strings 32 51220 3154)
  (string-bytes 1 1720184)
  (vectors 16 28209)
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bug#45292: Acknowledgement (28.0.50; first key typed ignores current input method (in magit commit buffer))

[Platon Pronko]

Seems that removal of record_asynch_buffer_change() at the end of read_and_dispose_of_process_output() causes the issue.

bug#45292: Acknowledgement (28.0.50; first key typed ignores current input method (in magit commit buffer))

[Platon Pronko]

Digged into it further. Here's what I found:

1. quail-input-method is used to translate keys according current keymap.

2. At the time of the first keystroke ("j" in my example) quail-input-method sees incorrect buffer (verified this by calling and printing buffer-name from inside quail-input-method). It sees "magit: test-repo" on the first keystroke, and "COMMIT_EDITMSG" on subsequent keystrokes. And since "magit: test-repo" is read-only, no translation is done and key is returned as-is.

3. So apparently record_asynch_buffer_change() was crucial to update the current buffer.

bug#45292: Acknowledgement (28.0.50; first key typed ignores current input method (in magit commit buffer))

[Stefan Monnier]

> Digged into it further. Here's what I found:
>
> 1. quail-input-method is used to translate keys according current keymap.
>
> 2. At the time of the first keystroke ("j" in my example) quail-input-method
> sees incorrect buffer (verified this by calling and printing buffer-name
> from inside quail-input-method). It sees "magit: test-repo" on the first
> keystroke, and "COMMIT_EDITMSG" on subsequent keystrokes. And since "magit:
> test-repo" is read-only, no translation is done and key is returned as-is.
>
> 3. So apparently record_asynch_buffer_change() was crucial to update the current buffer.

Here's what's happening:
1- after hitting `c c`, Magit launches `git` in the background
2- at this point we're entering `read_char` and the current buffer is the
   Magit buffer.
3- soon after, git launches the editor, which Magit has set to emacsclient
4- emacsclient contacts us
5- while still in `read_char` is waiting in `sit_for`, we process
   emacsclient which sets up the git-commit buffer,
   displays it and select it as the main window.
6- `sit_for` carefully preserves the current buffer so after step 5,
   we're still in the Magit buffer even though the selected windows is
   not the git-commit one.
7- we hit `j` in the git-commit buffer/window but it's read while in
   cvs-commit
8- boom!

I installed the patch below which fixes this problem.


        Stefan


diff --git a/src/dispnew.c b/src/dispnew.c
index bcea26a66a..534002584e 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -6062,6 +6062,8 @@ sit_for (Lisp_Object timeout, bool reading, int display_option)
   intmax_t sec;
   int nsec;
   bool do_display = display_option > 0;
+  bool curbuf_eq_winbuf
+    = (current_buffer == XBUFFER (XWINDOW (selected_window)->contents));
 
   swallow_events (do_display);
 
@@ -6116,6 +6118,13 @@ sit_for (Lisp_Object timeout, bool reading, int display_option)
   wait_reading_process_output (sec, nsec, reading ? -1 : 1, do_display,
 			       Qnil, NULL, 0);
 
+  if (reading && curbuf_eq_winbuf)
+    /* Timers and process filters/sentinels may have changed the selected
+       window (e.g. in response to a connection from emacsclient), in which
+       case we should follow it (unless we weren't in the selected-window's
+       buffer to start with).  */
+    set_buffer_internal (XBUFFER (XWINDOW (selected_window)->contents));
+
   return detect_input_pending () ? Qnil : Qt;
 }
 

bug#45292: Acknowledgement (28.0.50; first key typed ignores current input method (in magit commit buffer))

[Platon Pronko]

Thank you! Tested the version with the patch - the problem doesn't appear anymore on my machine.

bug#45292: 28.0.50; first key typed ignores current input method (in magit commit buffer)

[Stefan Kangas]

Platon Pronko <platon7pronko@gmail.com> writes:

> Thank you! Tested the version with the patch - the problem doesn't appear anymore on my machine.

I'm therefore closing this bug report.