C-x z is useless after switching frames

C-x z is useless after switching frames

[David Kastrup]

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the emacs-pretest-bug@gnu.org mailing list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

This is on a focus-follows-mouse window manager: After switching
frames, C-x z spews an error message.  See below.

In GNU Emacs 22.1.50.4 (i686-pc-linux-gnu, GTK+ Version 2.10.11)
 of 2007-08-14 on lisa
Windowing system distributor `The X.Org Foundation', version 11.0.70200000
configured using `configure  '--prefix=/usr/local/emacs-21' '--without-toolkit-scroll-bars''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Major mode: Shell-script

Minor modes in effect:
  shell-dirtrack-mode: t
  TeX-PDF-mode: t
  server-mode: t
  desktop-save-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t

Recent input:
<up> <up> <up> <up> <up> C-x z <switch-frame> C-x z 
M-x r e p o r t - e m a c s - b u g <return>

Recent messages:
Repeating command previous-line
Repeating command handle-switch-frame
repeat: handle-switch-frame must be bound to an event with parameters
Loading emacsbug...done

-- 
David Kastrup

Re: C-x z is useless after switching frames

[martin rudalics]

 > repeat: handle-switch-frame must be bound to an event with parameters

`repeat' can also produce things like

   handle-select-window must be bound to an event with parameters

   mouse-popup-menubar-stuff must be bound to an event with parameters

Probably `repeat' should ignore event bound commands.

Re: C-x z is useless after switching frames

[Richard Stallman]

       handle-select-window must be bound to an event with parameters

       mouse-popup-menubar-stuff must be bound to an event with parameters

    Probably `repeat' should ignore event bound commands.

The way to fix this is to prevent those commands
from getting into real-last-command.

Would someone please implement that and ack?

Re: C-x z is useless after switching frames

[Richard Stallman]

[I sent this message a week ago but did not get a response.]

       handle-select-window must be bound to an event with parameters

       mouse-popup-menubar-stuff must be bound to an event with parameters

    Probably `repeat' should ignore event bound commands.

The way to fix this is to prevent those commands
from getting into real-last-command.

Would someone please implement that and ack?

Re: C-x z is useless after switching frames

[martin rudalics]

 > [I sent this message a week ago but did not get a response.]
 >
 >        handle-select-window must be bound to an event with parameters
 >
 >        mouse-popup-menubar-stuff must be bound to an event with parameters
 >
 >     Probably `repeat' should ignore event bound commands.
 >
 > The way to fix this is to prevent those commands
 >>from getting into real-last-command.
 >
 > Would someone please implement that and ack?

Inherently, changing `real-last-command' is not "nice".  There might be
some code around that relies on telling whether `real-last-command' was
trying to handle a window or frame selection.  Suppose also I tried to
compare `last-command' and `real-last-command' to detect whether some
code has deliberately changed `last-command'.  The comparison would not
fail because someone did, but because `real-last-command' was reset
(resetting `last-command' together with `real-last-command' seems hardly
the right solution for this).

Disregarding my scruples, how do I tell whether `real-this-command' was
bound to an input event at the time of executing

	  current_kboard->Vreal_last_command = real_this_command;

Re: C-x z is useless after switching frames

[Richard Stallman]

    Inherently, changing `real-last-command' is not "nice".

I wasn't thinking of changing it; rather, not setting it at all for
those kinds of events.

That probably works in practice, because the only other package
that tests `real-last-command' is table.el, and I think it could
just as well use `last-command'.

But you are right that this isn't entirely clean. 
What could be a cleaner method?

Perhaps to make a new variable and set it at the C level, almost like
`real-last-command' but excluding certain commands, or certain events.

    Disregarding my scruples, how do I tell whether `real-this-command' was
    bound to an input event at the time of executing

	      current_kboard->Vreal_last_command = real_this_command;

My idea was to test last_command_char.

Re: C-x z is useless after switching frames

[martin rudalics]

[-- Attachment #1: Type: text/plain, Size: 1431 bytes --]

 >     Inherently, changing `real-last-command' is not "nice".
 >
 > I wasn't thinking of changing it; rather, not setting it at all for
 > those kinds of events.

I meant "changing the semantics of `real-last-command'".  We'd change
the semantics by _not_ setting it.

 > That probably works in practice, because the only other package
 > that tests `real-last-command' is table.el, and I think it could
 > just as well use `last-command'.

Yes.  But if we were to suggest not testing `real-last-command' in Lisp
code (aside from repeat.el) we probably shouldn't mention that variable
in the manual in the first place.

 > But you are right that this isn't entirely clean.
 > What could be a cleaner method?
 >
 > Perhaps to make a new variable and set it at the C level, almost like
 > `real-last-command' but excluding certain commands, or certain events.

We could call it `last-repeatable-command' and have repeat.el use that
instead of `real-last-command'.  I attached a patch for keyboard.c.

 >     Disregarding my scruples, how do I tell whether `real-this-command' was
 >     bound to an input event at the time of executing
 >
 > 	      current_kboard->Vreal_last_command = real_this_command;
 >
 > My idea was to test last_command_char.

We maybe should say somewhere that it's a bad idea to change
`last-command-char' (and probably `real-last-command' and
`last-repeatable-command' as well) while executing a command.

[-- Attachment #2: keyboard.patch --]
[-- Type: text/plain, Size: 2408 bytes --]

*** keyboard.c	Sun Jun 10 17:46:54 2007
--- keyboard.c	Sun Aug 26 11:22:14 2007
***************
*** 1536,1542 ****
    /* Do this after running Vpost_command_hook, for consistency.  */
    current_kboard->Vlast_command = Vthis_command;
    current_kboard->Vreal_last_command = real_this_command;
! 
    while (1)
      {
        if (! FRAME_LIVE_P (XFRAME (selected_frame)))
--- 1536,1544 ----
    /* Do this after running Vpost_command_hook, for consistency.  */
    current_kboard->Vlast_command = Vthis_command;
    current_kboard->Vreal_last_command = real_this_command;
!   if (!CONSP (last_command_char))
!     current_kboard->Vlast_repeatable_command = real_this_command;
!     
    while (1)
      {
        if (! FRAME_LIVE_P (XFRAME (selected_frame)))
***************
*** 1916,1921 ****
--- 1918,1925 ----
  	{
  	  current_kboard->Vlast_command = Vthis_command;
  	  current_kboard->Vreal_last_command = real_this_command;
+ 	  if (!CONSP (last_command_char))
+ 	    current_kboard->Vlast_repeatable_command = real_this_command;
  	  cancel_echoing ();
  	  this_command_key_count = 0;
  	  this_command_key_count_reset = 0;
***************
*** 11053,11058 ****
--- 11057,11063 ----
    kb->Voverriding_terminal_local_map = Qnil;
    kb->Vlast_command = Qnil;
    kb->Vreal_last_command = Qnil;
+   kb->Vlast_repeatable_command = Qnil;
    kb->Vprefix_arg = Qnil;
    kb->Vlast_prefix_arg = Qnil;
    kb->kbd_queue = Qnil;
***************
*** 11540,11545 ****
--- 11545,11555 ----
    DEFVAR_KBOARD ("real-last-command", Vreal_last_command,
  		 doc: /* Same as `last-command', but never altered by Lisp code.  */);
  
+   DEFVAR_KBOARD ("last-repeatable-command", Vlast_repeatable_command,
+ 		 doc: /* Last command that may be repeated.
+ The last command executed that was not bound to an input event.
+ This is the command `repeat' will try to repeat.  */);
+ 
    DEFVAR_LISP ("this-command", &Vthis_command,
  	       doc: /* The command now being executed.
  The command can set this variable; whatever is put here
***************
*** 11938,11943 ****
--- 11948,11954 ----
        mark_object (kb->Voverriding_terminal_local_map);
        mark_object (kb->Vlast_command);
        mark_object (kb->Vreal_last_command);
+       mark_object (kb->Vlast_repeatable_command);
        mark_object (kb->Vprefix_arg);
        mark_object (kb->Vlast_prefix_arg);
        mark_object (kb->kbd_queue);

[-- Attachment #3: Type: text/plain, Size: 142 bytes --]

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Re: C-x z is useless after switching frames

[Richard Stallman]

Please install your patch in Emacs 22, and fix repeat.el too.

    We maybe should say somewhere that it's a bad idea to change
    `last-command-char' (and probably `real-last-command' and
    `last-repeatable-command' as well) while executing a command.

That is a good idea.  Please propose a patch.

Re: C-x z is useless after switching frames

[martin rudalics]

[-- Attachment #1: Type: text/plain, Size: 41 bytes --]

Attached find a patch for commands.texi.

[-- Attachment #2: commands.patch --]
[-- Type: text/plain, Size: 1308 bytes --]

*** commands.texi.~1.105.~	Tue Jun  5 22:41:18 2007
--- commands.texi	Wed Aug 29 14:01:42 2007
***************
*** 716,722 ****
  @section Information from the Command Loop
  
  The editor command loop sets several Lisp variables to keep status
! records for itself and for commands that are run.
  
  @defvar last-command
  This variable records the name of the previous command executed by the
--- 716,724 ----
  @section Information from the Command Loop
  
  The editor command loop sets several Lisp variables to keep status
! records for itself and for commands that are run.  With the exception of
! @code{this-command} and @code{last-command} it's generally a bad idea to
! change any of these variables in a Lisp program.
  
  @defvar last-command
  This variable records the name of the previous command executed by the
***************
*** 736,741 ****
--- 738,749 ----
  but never altered by Lisp programs.
  @end defvar
  
+ @defvar last-repeatable-command
+ This variable stores the most recently executed command that was not
+ part of an input event.  This is the command @code{repeat} will try to
+ repeat, @xref{Repeating,,, emacs, The GNU Emacs Manual}.
+ @end defvar
+ 
  @defvar this-command
  @cindex current command
  This variable records the name of the command now being executed by

[-- Attachment #3: Type: text/plain, Size: 142 bytes --]

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Re: C-x z is useless after switching frames

[Richard Stallman]

The change is good.

    *** commands.texi.~1.105.~	Tue Jun  5 22:41:18 2007
    --- commands.texi	Wed Aug 29 14:01:42 2007

Please install it.