bug#45820: menu-bar-mode: show drop-down menu instead of tmm-menubar in terminal Emacs

[Tim Lee]

The problem: In terminal Emacs, clicking on an item in the menu bar will open "tmm-menubar".

Expected behavior: "menu-bar-open" should be run instead (i.e. a drop-down menu should appear instead of tmm-menubar).

For example, if I left-click on the "Edit" menu item in the menu bar, I expect the "Edit" drop-down to appear. Currently however, a left-click on a menu item will open tmm-menubar in a *Completions* window. This is surprising behavior.

By default, in terminal Emacs, "<menu-bar> <mouse-1>" is bound to "tmm-menubar-mouse". There doesn't seem to be an easy way to change this to the drop-down menu instead.

There exist a question about this issue on Emacs Stack Exchange site: https://emacs.stackexchange.com/questions/50478/replace-clicking-a-menu-bar-option-from-m-to-f10-behavior The proposed "solution" there is similar to this:

(define-key global-map [menu-bar mouse-1]
            (lambda (event)
              (interactive "e")
              ;; Adapted from the implementation of "menu-bar-open" in Emacs 25.2.2.
              (let* ((x (car (posn-x-y (event-start event))))
                     (menu (menu-bar-menu-at-x-y x 0)))
                (popup-menu (or (lookup-key-ignore-too-long global-map (vector 'menu-bar menu))
                                (lookup-key-ignore-too-long (current-local-map) (vector 'menu-bar menu))
                                (cdar (minor-mode-key-binding (vector 'menu-bar menu)))
                                (mouse-menu-bar-map))
                            (posn-at-x-y x 0 nil t)
                            nil
                            t))))

However, there are serious flaws with this "solution":

• Clicking on a menu bar item (e.g. "Help"), followed immediately by clicking outside the menus and drop-downs (e.g. clicking in the window) will not cancel the selected action. Instead, the highlighted action will actually run.
• Clicking on a particular menu bar item (e.g. "Help") and immediately clicking on it again will not close the drop-down menu.

(Emacs version: 25.2.2, Terminal: GNOME Terminal 3.28.2, OS: Ubuntu 18.04)

[Eli Zaretskii]

> From: Tim Lee <[hidden email]>
> Date: Tue, 12 Jan 2021 23:30:31 +0800
>
> The problem: In terminal Emacs, clicking on an item in the menu bar will open "tmm-menubar".

Which terminal is that, and what kind of mouse support does it use?
If you are using xt-mouse, then what you want is already implemented
in what will become the next major release, Emacs 28.

If you are using some other mouse support, please describe that.

> However, there are serious flaws with this "solution":

Yes, they were all recently fixed for xt-mouse.

[Tim Lee]

> Which terminal is that, and what kind of mouse support does it use?

Terminal: GNOME Terminal 3.28.2 on Ubuntu 18.04.

Mouse support: (xterm-mouse-mode t)

> If you are using xt-mouse, then what you want is already implemented
> in what will become the next major release, Emacs 28.

Yes, I am using xt-mouse. Thank you for the information about Emacs 28.

By "what you want is already implemented", do you mean that Emacs 28's
menu bar will show the drop-down menu when clicked, or would I still
need to add "(define-key global-map [menu-bar mouse-1] ...)" to my Emacs
configuration file?

[Eli Zaretskii]

> From: Tim Lee <[hidden email]>
> Cc: [hidden email]
> Date: Wed, 13 Jan 2021 13:11:02 +0800
>
> Yes, I am using xt-mouse. Thank you for the information about Emacs 28.
>
> By "what you want is already implemented", do you mean that Emacs 28's
> menu bar will show the drop-down menu when clicked, or would I still
> need to add "(define-key global-map [menu-bar mouse-1] ...)" to my Emacs
> configuration file?

The former: it works as you expect without any need to tinker.