bug#43756: Fix for TTY menus mouse interaction

[Jared Finder]

On 2020-10-03 12:23 am, Eli Zaretskii wrote:
> > Date: Fri, 02 Oct 2020 12:54:54 -0700
> > From: Jared Finder <jared@finder.org>
> > Cc: larsi@gnus.org, 43756@debbugs.gnu.org
> >
> > > Ah, xterm-mouse-mode.  AFAIR, no one has made TTY menus work with
> > > xterm-mouse-mode.  The first thing to do is to disable tmm-menubar,
> > > and then you need to cause a mouse click call menu-bar-open with the
> > > 2nd argument set to the X coordinate of the click.
> >
> > I think this may be getting mixed up with my feature proposal on
> > emacs-devel? I did find this bug when working on making the TTY menus
> > work with xterm-mouse-mode and they both affect menus. The patches I
> > attached in that thread follow the pattern you described.
> >
> > This bug report is separable from the rest of that feature. It's also
> > much smaller, just two lines. :) This fixes the current behavior of 
> > the
> > command tmm-menubar-mouse, which is bound to <menu-bar> <mouse-1>.
>
> So you are saying that when tmm-menubar-mouse is invoked by mouse
> clicks, it shows incorrect menus after "M-x ielm", but only if you
> click on the menu items specific to IELM?  It sounds like tmm-menubar
> has a bug in its translation of the X coordinate of the click to the
> menu-bar item, perhaps because it considers only the global menu
> keymap.

I think the issue is that the ordering of elements in 
menu-bar-final-items controls the order of the display menu bar, but 
tmm-menubar-keymap does not currently take that into account. It was 
pure luck that my first patch fixed anything. :)

Attached is a new patch and more detailed repro steps.

First, the ordering bug (the changes inside tmm-menubar-keymap):

Environment:

* Emacs repo from git://git.sv.gnu.org/emacs.git, commit 
f6277911eb2c520aec8f0efd80c91999226e3322
* Run on Debian under Windows Subsystem for Linux 2 (the VM version). 
I've also seen this on MacOS and native Win32 builds of Emacs.

Steps to reproduce:

emacs -Q
M-x load-library <RET> tmm <RET>

Defining the following stripped down version of tmm-menubar makes it 
easier to visually compare the displayed menu bar with what tmm-menubar 
would show:

(defun menubar-items ()
  "Simplified version of tmm-menubar."
  (let ((column 0)
        (menu-bar (tmm-menubar-keymap))
        list)
    (catch 'done
      (map-keymap
       (lambda (key binding)
         (pcase binding
           ((or `(,(and (pred stringp) name) . ,_) ;Simple menu item.
                `(menu-item ,name ,_cmd            ;Extended menu item.
                            . ,(and props
                                    (guard (let ((visible
                                                  (plist-get props 
:visible)))
                                             (or (null visible)
                                                 (eval visible)))))))
            (push (cons name column) list)
            (setq column (+ column (length name) 1)))))
       menu-bar)
    (nreverse list))))

M-x ielm

Eval (menubar-items)
--> observe that the ordering of menu items returned is not the same as 
the displayed menu bar.
--> With my patch this is correct.

Eval (setf menu-bar-final-items '(help-menu completion signals inout))
Force redisplay via C-l
--> observe that the ordering of menu items in the displayed menu bar 
has changed.

Eval (menubar-items)
--> observe that the ordering of menu items returned has not changed.
--> With my patch this is correct.

Repeat above steps for other values of menu-bar-final-items. You can add 
'file to the list, set it to nil, etc.


The click bug is a simple fix in tmm-menubar since the lambda passed in 
to map-keymap always checks against the previous menu item (e.g. 
prev-key), therefore missing the last item. Repro steps are same as 
before.

  -- MJF

0001-Fixing-small-bugs-in-tmm.el.patch
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