Replace clicking a menu bar option from M-` to f10 behavior

Question

When I click on File I want to see and not

What can I change to provide this functionality? This question didn't really get the right answer.

Answer 1

f1 c (describe-key-briefly) works for mouse clicks and menu items too. So hit f1 c, click on the menu bar, and you'll see <menu-bar> <mouse-1> at that spot runs the command tmm-menubar-mouse. Whereas f1 c f10 says <f10> runs the command menu-bar-open. So to rebind:

(define-key global-map (kbd "<menu-bar> <mouse-1>") 'menu-bar-open)

Clicking on a different option than File will still open the file menu

Right, menu-bar-open doesn't check xy location of the mouse click. Looking at the code of menu-bar-open I came up with this:

(defun menu-bar-open-xy (mouse-event)
  (interactive "e")
  (pcase mouse-event
    (`(mouse-1 (,_ menu-bar (,x . ,y) . ,_))
     (let ((menu (menu-bar-menu-at-x-y x y)))
       (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 y nil t) nil t)))
    (_ (error "unexpected event %S" mouse-event))))

(define-key global-map (kbd "<menu-bar> <mouse-1>") 'menu-bar-open-xy)

The X co-ordinate is a bit off though, not clear why.

Clicking on File once file is open doesn't close the menu, just reopens it

Yeah, I'm not sure how to fix that. I guess that explains why this isn't the default in Emacs yet...