bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[N. Jackson]

0. $ src/emacs -Q
1. C-h k C-mouse-3

Expected behaviour:

A help buffer describes whatever command it is that is bound to
C-mouse-3.

Observed behaviour:

A context menu pops up and in the echo area, "Describe the following
key, mouse click, or menu item: C-down-mouse-3-" is displayed. But then
one is stuck:

- If one hits ESC, the context menu disappears, "Quit" appears in the
  echo area, and no help buffer is displayed.

- If one hits RET to accept the value in the prompt in the echo area,
  annoyingly nothing happens at all, and one stays in the same stuck
  state.

- If one clicks in the echo area to try to change "C-down-mouse-3-" to
  "C-down-mouse-3", or just to be sure the RET goes to the minibuffer
  not to the context menu, "Quit" appears in the echo area, and no help
  buffer is displayed.


In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.26)
 of 2018-10-24 built on moondust.localdomain
Repository revision: 00027ff9d0f646662458bdb47cc7e2214f439698
Windowing system distributor 'Fedora Project', version 11.0.11906000
System Description: Fedora 27 (Workstation Edition)

Configured using:
 'configure 'CFLAGS=-O3 -g3 -gdwarf-4''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS GLIB NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS LCMS2 GMP

Important settings:
  value of $LANG: en_CA.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: Info

Minor modes in effect:
  TeX-PDF-mode: t
  diff-auto-refine-mode: t
  pdf-occur-global-minor-mode: t
  shell-dirtrack-mode: t
  recentf-mode: t
  display-battery-mode: t
  display-time-mode: t
  show-paren-mode: t
  savehist-mode: t
  save-place-mode: t
  electric-pair-mode: t
  desktop-save-mode: t
  delete-selection-mode: t
  cua-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-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
  temp-buffer-resize-mode: t
  buffer-read-only: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  global-visual-line-mode: t
  visual-line-mode: t
  transient-mark-mode: t

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bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Eli Zaretskii]

> From: "N. Jackson" <nljlistbox2@gmail.com>
> Date: Thu, 08 Nov 2018 16:49:24 -0500
> 
> 0. $ src/emacs -Q
> 1. C-h k C-mouse-3
> 
> Expected behaviour:
> 
> A help buffer describes whatever command it is that is bound to
> C-mouse-3.

I don't think we can do that with all toolkits, because once Emacs
pops up the menu, the toolkit has control.

In any case, C-mouse-3 is a kind of prefix key, and we never display
help for prefix keys, we always wait for the user to type the complete
key sequence, which in this case includes menu selection.

> Observed behaviour:
> 
> A context menu pops up and in the echo area, "Describe the following
> key, mouse click, or menu item: C-down-mouse-3-" is displayed. But then
> one is stuck:
> 
> - If one hits ESC, the context menu disappears, "Quit" appears in the
>   echo area, and no help buffer is displayed.
> 
> - If one hits RET to accept the value in the prompt in the echo area,
>   annoyingly nothing happens at all, and one stays in the same stuck
>   state.
> 
> - If one clicks in the echo area to try to change "C-down-mouse-3-" to
>   "C-down-mouse-3", or just to be sure the RET goes to the minibuffer
>   not to the context menu, "Quit" appears in the echo area, and no help
>   buffer is displayed.

You need to select one of the menu items by clicking on it, then you
will see the help for that item.

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[N. Jackson]

At 09:57 +0200 on Friday 2018-11-09, Eli Zaretskii wrote:
>
> C-mouse-3 is a kind of prefix key, and we never display
> help for prefix keys, we always wait for the user to type the complete
> key sequence, which in this case includes menu selection.

Oh, I see. That makes sense, now that you say it!

Perhaps the documentation for `describe-key' should mention that? It
might say something about it displaying that final hyphen while it is
waiting for more input, when a complete key command has not yet been
entered for it to display help on.

> You need to select one of the menu items by clicking on it, then you
> will see the help for that item.

Right. I understand that now. [Although in this case I wasn't looking
for the documentation of one of the menu items, I was looking for the
documentation for whatever function pops up the menu itself.]

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Drew Adams]

> in this case I wasn't looking for the documentation of one
> of the menu items, I was looking for the
> documentation for whatever function pops up the menu itself.

I know of no good answer for that.  Maybe it should be an
enhancement request.

You can find out which keymap the prefix key is bound to by
doing this:

M-x pp-eval-expression
(lookup-key (current-global-map) (kbd "C-<down-mouse-3>"))

But you have to know whether it is <down-mouse-3> or <mouse-3>
that has the binding.  And that evaluation does not tell you
the name of a variable that might be bound to the keymap.  It
just shows you the keymap itself.

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > I don't think we can do that with all toolkits, because once Emacs
  > pops up the menu, the toolkit has control.

Are any of the supported display methods not worth supporting any more?
In principle, we could drop any that users don't care about any more.

-- 
Dr Richard Stallman
President, Free Software Foundation (https://gnu.org, https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Cc: nljlistbox2@gmail.com, 33320@debbugs.gnu.org
> Date: Fri, 09 Nov 2018 18:02:11 -0500
> 
>   > I don't think we can do that with all toolkits, because once Emacs
>   > pops up the menu, the toolkit has control.
> 
> Are any of the supported display methods not worth supporting any more?
> In principle, we could drop any that users don't care about any more.

I'm not aware of any we want to drop, and the question was about GTK,
which we definitely don't want to drop.

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Glenn Morris]

Richard Stallman wrote:

>   > I don't think we can do that with all toolkits, because once Emacs
>   > pops up the menu, the toolkit has control.
>
> Are any of the supported display methods not worth supporting any more?
> In principle, we could drop any that users don't care about any more.

This has been discussed before, see eg https://debbugs.gnu.org/26180 .
The Motif and "no toolkit" toolkits are very little used
(see eg https://debbugs.gnu.org/stats/emacs.html).
The Lucid/Athena toolkit is a bit more popular. I use and like it
myself, but would be willing to see it go if it made life substantially
easier for the people maintaining these areas of Emacs.
I also think GTK+ v2 could go, frankly, though that could be a bit contentious.
That would leave only GTK+ v3 (ie, support only the current stable GTK+).

But that's all irrelevant since the people working on these areas feel
differently, see bug#26180 again.

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Robert Pluim]

Glenn Morris <rgm@gnu.org> writes:

> Richard Stallman wrote:
>
>>   > I don't think we can do that with all toolkits, because once Emacs
>>   > pops up the menu, the toolkit has control.
>>
>> Are any of the supported display methods not worth supporting any more?
>> In principle, we could drop any that users don't care about any more.
>
> This has been discussed before, see eg https://debbugs.gnu.org/26180 .
> The Motif and "no toolkit" toolkits are very little used
> (see eg https://debbugs.gnu.org/stats/emacs.html).

As mentioned in that bug, the other toolkits are useful for sanity
checking.

> The Lucid/Athena toolkit is a bit more popular. I use and like it
> myself, but would be willing to see it go if it made life substantially
> easier for the people maintaining these areas of Emacs.
> I also think GTK+ v2 could go, frankly, though that could be a bit contentious.
> That would leave only GTK+ v3 (ie, support only the current stable GTK+).
>

GTK+ v2 could go I guess, but I donʼt think it causes too many
problems. The problems I have stem mostly from the mixing of GTK and
X11 calls, so the goal there should be to remove the direct calls into
X11 (especially since at some point X11 will disappear to be replaced
by Wayland).

Robert

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[martin rudalics]

 > The problems I have stem mostly from the mixing of GTK and
 > X11 calls, so the goal there should be to remove the direct calls into
 > X11 (especially since at some point X11 will disappear to be replaced
 > by Wayland).

Maybe we could convince Glenn to set things up for us: provide gtk
equivalents of xterm.h, xterm.c, xfns.c and whatever else we would
need and the facilities for making a "pure" gtk build - one that does
not rely on xterm.h, xfns.c,...  Then people could (1) eliminate the
Lucid, Motif, non-toolkit stuff from there (2) optionally merge
gtkutil there and (3) eventually remove the X11 dependent parts.
Otherwise, this will remain a pipe dream till the end of time.

martin

bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Lars Ingebrigtsen]

"N. Jackson" <nljlistbox2@gmail.com> writes:

> Perhaps the documentation for `describe-key' should mention that? It
> might say something about it displaying that final hyphen while it is
> waiting for more input, when a complete key command has not yet been
> entered for it to display help on.

I've now done this in Emacs 29.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no