Re: Functions which are mode dependent

[Heime]

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On Friday, August 23rd, 2024 at 10:07 AM, Heime <heimeborgia@protonmail.com> 
wrote:

> On Friday, August 23rd, 2024 at 6:58 AM, Yuri Khan yuri.v.khan@gmail.com 
> wrote:
> 
> > On Mon, 19 Aug 2024 at 04:15, Heime heimeborgia@protonmail.com wrote:
> > 
> > > I need some help understanding how to automatically enable some 
> > > functionality
> > > when loading a file with some major mode.
> > 
> > The major mode you’re customizing has a hook. As an end user, you add
> > your own function to that hook, and enable the functionality there.
> > 
> > (As a package developer, you’d make your functionality use some
> > buffer-local variables. Your users would add their own functions to
> > mode hooks where they would set their own variable values and then
> > call your function or enable your minor mode.)
> 
> 
> How does one use the buffer local variable ? Is it to save the
> regexp which I sot immediately to imenu-generic-expression ?
> 
> How would one do it ?

There is this possibility. 

(defun tema-expr-elisp ()
  "Set `imenu-generic-expression` to match custom headings in the current 
buffer."
  (make-local-variable 'imenu-generic-expression)
  (setq imenu-generic-expression
        `(("DEFUN"
          ,(concat "^\\s-*"
                   "(\\(defun\\|define-minor-mode\\)\\s-+"
                   "\\(\\(\\sw\\|\\s_\\)+\\)") 2) )))
 
> > > For instance I have a function that sets
> > > 
> > > (defun expr-elisp ()
> > > 
> > > (setq imenu-generic-expression
> > > `( ("defun" ,(concat "^\\s-*"
> > > "(\\(defun\\|define-minor-mode\\)\\s-+"
> > > "\\(\\(\\sw\\|\\s_\\)+\\)") 2) )) )
> > > 
> > > (defun expr-selector ()
> > > 
> > > (cond
> > > ((eq major-mode 'emacs-lisp-mode) (expr-elisp))
> > > (t (expr-generic)) ))
> > 
> > Having to compare ‘major-mode’ against a symbol is a sign you’re doing
> > something wrong, for several reasons.
> 
> 
> This is the first time doing such a thing, and came up with it. I had
> a hunch it was not the proper way, so I asked for some feedback to make
> it good, with this help list.
> 
> > * A major mode can inherit from another major mode. In that case, the
> > right thing is for your customization to work automatically for the
> > derived mode as well as the base mode. However, comparing for equality
> > only handles the base mode.
> 
> 
> What is one to use to handle an elisp derived mode for my case ?
> Still with a mode hook ?
> 
> > * To extend your customization to modes not originally in your list,
> > you’d have to modify your ‘expr-selector’ function.
> > 
> > > I have put the code above in a minor mode.
> > > 
> > > ;;;###autoload
> > > (define-minor-mode tema-minor-mode
> > > 
> > > (if tema-minor-mode
> > > (expr-selector)
> > > (message "Tema Deactivated")))
> > > 
> > > with hooks to load the minor mode automatically for specific major modes.
> > 
> > As told by Stefan, your minor mode is pointless because it does
> > nothing when turned off.
> 
> 
> For now I only want to make the functionality work, and concentrate
> upon that first.
> 
> > > (add-hook emacs-lisp-mode-hook #'tema-minor-mode)
> 
> > If all you want is to set ‘imenu-generic-expression’ to that list for
> > buffers using ‘emacs-lisp-mode’ or any major mode derived from that,
> > and to another list for buffers in ‘sh-mode’ or any major modes
> > derived from that, all you need to do is:
> > 
> > (defun expr-elisp ()
> > (setq imenu-generic-expression
> > `( ("defun" ,(concat "^\\\\\\\\s-*" 
> > "(\\\\\\\\(defun\\\\\\\\|define-minor-mode\\\\\\\\)\\\\\\\\s-+" 
> > "\\\\\\\\(\\\\\\\\(\\\\\\\\sw\\\\\\\\|\\\\\\\\s_\\\\\\\\)+\\\\\\\\)") 2) )) 
> > ) (add-hook emacs-lisp-mode-hook #'expr-elisp) (defun expr-sh () (setq 
> > imenu-generic-expression` ( …something else… )))
> > 
> > (add-hook sh-mode-hook #'expr-sh)
> > 
> > You do not need a minor mode for that.
> 
> 
> I know about using hook with a function such as (add-hook sh-mode-hook 
> #'expr-sh)
> 
> But I want to work on making a minor-mode. Firstly because I have some
> other functionality to add to it. Secondly to see how to do a minor-mode
> that in also major mode dependent.
> 
> > (Also, your private functions should be named starting with a short
> > string reasonably unique to you, so that it does not collide with any
> > public packages you could install.)
> 
> 
> I have no problem with doing so.