bug#41343: tab-bar-mode: Close tab on mouse-2 click

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: stefankangas@gmail.com,  41343@debbugs.gnu.org
> Date: Fri, 06 Aug 2021 03:41:17 +0300
> 
> >>   (defvar tab-line-tab-map
> >>     (let ((map (make-sparse-keymap)))
> >>       (define-key map [tab-line mouse-1] 'tab-line-select-tab)
> >>       (define-key map [tab-line mouse-2] 'tab-line-close-tab)
> >>
> >> But it's impossible to do the same for the menu-bar and the tool-bar
> >> and so in the tab-bar too.
> >
> > Why not?  What prevents that?
> 
> It's too late to change how keys are implemented for tab-bar.
> The tab-bar keymap contains such keys as 'tab-1' and 'C-tab-2',
> and clicking mouse-1 on tabs emits such events.  It doesn't emit
> 'mouse-1' and 'mouse-2'.

How do we translate mouse clicks into the likes of C-tab-2?  And what
prevents us from emitting something like tab-close-2 when mouse-2 is
clicked?

> >> Or do you mean adding an integer variable that holds
> >> a number of the mouse button used to close the tab?
> >> For example, tab-bar-close-tab-mouse-button = 2.
> >
> > I think we should explore such possibilities only after we understand
> > why normal key bindings don't work.
> 
> It should be possible to implement normal key bindings mouse-1/mouse-2,
> but such change will not be backward-compatible.

In what way will it be incompatible?