Re: Specifying mode in file variables trouble

[Lennart Borgman (gmail)]

Lennart Borgman (gmail) wrote:
> Richard M. Stallman wrote:
>>     Maybe, but I think most oftenly that will create name clashes.
>>
>> It will cause name clashes is you choose names of existing major modes,
>> but you can easily avoid using those.
>>
>> Here's what I suggest:
>>
>> If there is a customary name (say, `foo' for a kind of file which mixes
>> a few ordinary major modes, call the command `foo-mode'.
>>
>> Otherwise, if you want a command for the combination of two modes `a'
>> and `b', call it `a-b-mode'.
>>
>> Or we could use `a+b-mode' for such cases.
> 
> I like the idea of using "+" here, that is a good mnemonic.
> 
> For web template files (like PHP, JSP, Genshi etc) there are however
> often several major mode chunks involved. In for example a php file
> there may be chunks with these major modes
> 
>   - nxhtml-mode / html-mode
>   - php-mode
>   - css-mode
>   - javascript-mode
> 
> I currently use the name nxhtml-mumamo-mode (or html-mumamo-mode) for
> the multi major mode, which is of course not that very descriptive. The
> name begins with "nxhtml-" because that is the main major mode (there
> are only two levels allowed sofar, main major mode and sub chunks major
> modes).
> 
> Along with your suggestion nxhtml+php-mode would be the most natural.
> This name does not tell the whole truth, but is perhaps still less
> cryptic than nxhtml-mumamo-mode. I am not quite sure.
> 
>>     (There are still good reasons to tell
>>     that it is a multi major mode. The most difficult thing is support of
>>     minor modes turn on/off and finding reasonable structures for that. Time
>>     will tell I think.)
>>
>> Let's talk about this problem; maybe I can suggest a general solution
>> for it.
> 
> There might be several problem, but the bug report I just recieved for
> Imenu illustrates one principal problem:
> 
>   https://bugs.launchpad.net/bugs/272526
> 
> I have not looked into the details, but the problem reports says that
> Imenu does not work as expected when moving between chunks (with
> different major modes).
> 
> The principal problem here is probably that Imenu should work across all
> chunks with the same major modes and preserve its chunk specifric values
> when moving between those chunks.
> 
> So I am thinking about saving those values in a variable, something like
> this
> 
>   (make-variable-buffer-local 'mumamo-survive-minor-modes)
>   (put 'mumamo-survive-minor-modes 'permanent-local t)
>   (defvar mumamo-survive-minor-modes nil
>     "Hold local minor mode variables specific major modes.
>   Those values are saved when leaving a chunk with a certain
>   major mode and restored when entering a chunk with the same
>   major mode again.
> 
>   The value of this variable is an associative list where the key
>   is a list with
> 
>     \(MAJOR-MODE MINOR-MODE)
> 
>   and the value is a stored value for the minor mode.")
> 
> For storing the values I am thinking about using the code that does
> something similar for visual-line-mode where state variable values are
> stored in visual-line--saved-state.
> 
> However the drawback is that this has to be implemented for every minor
> mode of this kind, but I can't see any way around it currently.
> 
> ... eh, maybe another way to do it could be to save all buffer local
> variables this way and make exceptions for some ...


Here is something along the line of the last idea just above here:

(defun mumamo-save-buffer-locals (major)
  "Save some local variables for major mode MAJOR.
This should be called before switching to a new chunks major
mode."
  (let ((locals (buffer-local-variables)))
    (setq locals (mapcar (lambda (local)
                           (unless (or
                                    (memq (car local)
mumamo-buffer-locals-dont-set)
                                    (memq (car local) mumamo-survive)
                                    (get (car local) 'permanent-local)
                                    )))
                         locals))
    (setq locals (delq nil locals))
    (setq mumamo-buffer-locals-per-major
          (assq-delete-all major mumamo-buffer-locals-per-major))
    (setq mumamo-buffer-locals-per-major
          (cons (cons major-mode locals)
                mumamo-buffer-locals-per-major))))

;; (benchmark 1000 '(mumamo-save-buffer-locals major-mode))
;; (benchmark 1000 '(mumamo-restore-buffer-locals major-mode))
(defun mumamo-restore-buffer-locals (major)
  "Restore some local variables for major mode MAJOR.
This should be called after switching to a new chunks major
mode."
  (let ((locals (cdr (assq major mumamo-buffer-locals-per-major)))
        var
        perm)
    (dolist (rec locals)
      (setq var (car rec))
      (setq perm (get var 'permanent-local))
      (unless (or perm
                  (memq var mumamo-buffer-locals-dont-set))
        (setq var (cdr rec))))))