bug#70086: Mouse clicks in tab-bar don't call commands bound in keymap properties

[Adam Porter <adam@alphapapa.net>]

> Could you please distill this example into a self-contained test case
> like you did the previous time, that helped a lot.

Ok, the following code seems to demonstrate the problem, with your patch 
applied to tab-bar.el:


     (require 'cl-lib)

     (defvar tab-bar-ecm-keymap
       (let ((map (make-sparse-keymap)))
	(define-key map [tab-bar mouse-1] (lambda (&rest _)
					    (interactive)
					    (message "tab-bar-ecm-lighter clicked with mouse-1")))
	map))

     (defvar tab-bar-ecm-lighter "TAB-BAR-ECM-LIGHTER ")

     (define-minor-mode tab-bar-ecm-mode "DOCSTRING"
       :global t
       (let ((lighter `(tab-bar-ecm-mode
		       (:propertize tab-bar-ecm-lighter keymap ,tab-bar-ecm-keymap))))
	(if tab-bar-ecm-mode
	    (progn
	      (cl-pushnew lighter global-mode-string :test #'equal)
	      (unless (memq 'tab-bar-format-global tab-bar-format)
		(cl-callf append tab-bar-format '(tab-bar-format-global))))
	  (cl-callf2 remove lighter global-mode-string))))

     (defvar tab-bar-ecm-keymap2
       (let ((map (make-sparse-keymap)))
	(define-key map [tab-bar mouse-1] (lambda (&rest _)
					    (interactive)
					    (message "tab-bar-ecm-lighter2 clicked with mouse-1")))
	map))

     (defvar tab-bar-ecm-lighter2 "TAB-BAR-ECM-LIGHTER2 ")

     (define-minor-mode tab-bar-ecm-mode2 "DOCSTRING"
       :global t
       (let ((lighter `(tab-bar-ecm-mode2
		       (:propertize tab-bar-ecm-lighter2 keymap ,tab-bar-ecm-keymap2))))
	(if tab-bar-ecm-mode2
	    (progn
	      (cl-pushnew lighter global-mode-string :test #'equal)
	      (unless (memq 'tab-bar-format-global tab-bar-format)
		(cl-callf append tab-bar-format '(tab-bar-format-global))))
	  (cl-callf2 remove lighter global-mode-string))))


Enable both tab-bar-ecm-mode and tab-bar-ecm-mode2.  Then you'll see 
that, regardless of which lighter is clicked in the tab-bar, the lighter 
for the mode that was activated last catches the mouse clicks for both 
lighters.