New special-mode parent

New special-mode parent

[Stefan Monnier]

While thinking about the key-binding problems we have in vc-annotate it
occurred to me that it should use a view-mode minor mode, but rather it
should inherit from a sort of view-mode major mode, so it can override
its key-bindings.  And it occurred to me that it should be called
`special-mode' and should probably be used by most "special" major modes
(those that set the mode-class property to `special').

So I'm considering adding to subr.el a simple parent major mode:

   (defvar special-mode-map
     (let ((map (make-sparse-keymap)))
       (suppress-keymap map)
       (define-key map "q" 'quit-window)
       (define-key map " " 'scroll-up)
       (define-key map "\C-?" 'scroll-down)
       (define-key map "?" 'describe-mode)
       (define-key map ">" 'end-of-buffer)
       (define-key map "<" 'beginning-of-buffer)
       (define-key map "g" 'revert-buffer)
       map))
   
   (put 'special-mode 'mode-class 'special)
   (define-derived-mode special-mode nil "Special"
     "Parent major mode from which special major modes should inherit."
     (setq buffer-read-only t))

The above is 100% guaranteed thoroughly untested (written directly in
this *mail* buffer), so it's just a rough approximation, but should give
you some idea of where I'm going.

Any comment?


        Stefan

Re: New special-mode parent

[Lennart Borgman (gmail)]

Stefan Monnier wrote:
> While thinking about the key-binding problems we have in vc-annotate it
> occurred to me that it should use a view-mode minor mode, but rather it
> should inherit from a sort of view-mode major mode, so it can override
> its key-bindings.  And it occurred to me that it should be called
> `special-mode' and should probably be used by most "special" major modes
> (those that set the mode-class property to `special').
> 
> So I'm considering adding to subr.el a simple parent major mode:
> 
>    (defvar special-mode-map
>      (let ((map (make-sparse-keymap)))
>        (suppress-keymap map)
>        (define-key map "q" 'quit-window)
>        (define-key map " " 'scroll-up)
>        (define-key map "\C-?" 'scroll-down)
>        (define-key map "?" 'describe-mode)
>        (define-key map ">" 'end-of-buffer)
>        (define-key map "<" 'beginning-of-buffer)
>        (define-key map "g" 'revert-buffer)
>        map))
>    
>    (put 'special-mode 'mode-class 'special)
>    (define-derived-mode special-mode nil "Special"
>      "Parent major mode from which special major modes should inherit."
>      (setq buffer-read-only t))
> 
> The above is 100% guaranteed thoroughly untested (written directly in
> this *mail* buffer), so it's just a rough approximation, but should give
> you some idea of where I'm going.
> 
> Any comment?


I did not follow the vc discussion, but I like the idea of inherited 
general key binding sets. Though I am not sure they have to be in the 
form of a major mode. (Maybe sometimes multiple keymap parents would be 
useful, but that is another question.)

To me your suggestion here looks good. I would however prefer 
`special-view-mode'.

Re: New special-mode parent

[Tom Tromey]

>>>>> "Stefan" == Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

Stefan>    (put 'special-mode 'mode-class 'special)

I think it would be nice is define-derived-mode automatically did this
for modes derived from special-mode.

Tom

Re: New special-mode parent

[Stefan Monnier]

Stefan> (put 'special-mode 'mode-class 'special)
> I think it would be nice is define-derived-mode automatically did this
> for modes derived from special-mode.

Your wish was granted several years ago already,


        Stefan

Re: New special-mode parent

[Dan Nicolaescu]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

  > While thinking about the key-binding problems we have in vc-annotate it
  > occurred to me that it should use a view-mode minor mode, but rather it
  > should inherit from a sort of view-mode major mode, so it can override
  > its key-bindings.  And it occurred to me that it should be called
  > `special-mode' and should probably be used by most "special" major modes
  > (those that set the mode-class property to `special').
  > 
  > So I'm considering adding to subr.el a simple parent major mode:

  >    (defvar special-mode-map
  >      (let ((map (make-sparse-keymap)))
  >        (suppress-keymap map)
  >        (define-key map "q" 'quit-window)
  >        (define-key map " " 'scroll-up)
  >        (define-key map "\C-?" 'scroll-down)
  >        (define-key map "?" 'describe-mode)

This one does not seem that useful

  >        (define-key map ">" 'end-of-buffer)
  >        (define-key map "<" 'beginning-of-buffer)
  >        (define-key map "g" 'revert-buffer)

or this one

  > Any comment?

IMO, good idea in genearal.

How about having an even more minimalistic version of this turned on
even for read-only files?

Re: New special-mode parent

[Stefan Monnier]

>> (defvar special-mode-map
>> (let ((map (make-sparse-keymap)))
>> (suppress-keymap map)
>> (define-key map "q" 'quit-window)
>> (define-key map " " 'scroll-up)
>> (define-key map "\C-?" 'scroll-down)
>> (define-key map "?" 'describe-mode)

> This one does not seem that useful

view-mode provides it and it seemed like it wouldn't hurt.  But I don't
really care about it.

>> (define-key map ">" 'end-of-buffer)
>> (define-key map "<" 'beginning-of-buffer)
>> (define-key map "g" 'revert-buffer)
> or this one

You mean the "g" one?  That's actually one I find important: all/most
special modes provide it.

> How about having an even more minimalistic version of this turned on
> even for read-only files?

It'd be kind of incompatible with the idea of a major mode.


        Stefan

Re: New special-mode parent

[Juanma Barranquero]

On Fri, Jun 13, 2008 at 23:52, Stefan Monnier <monnier@iro.umontreal.ca> wrote:

>> This one does not seem that useful
>
> view-mode provides it and it seemed like it wouldn't hurt.  But I don't
> really care about it.

I do find it useful.

   Juanma

Re: New special-mode parent

[Tom Tromey]

>>>>> "Stefan" == Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>> I think it would be nice is define-derived-mode automatically did this
>> for modes derived from special-mode.

Stefan> Your wish was granted several years ago already,

Thanks, I did not realize that.

Here's a patch to update the documentation.

Tom

2008-06-14  Tom Tromey  <tromey@redhat.com>

	* modes.texi (Derived Modes): Document mode-class.

*** modes.texi	30 Jan 2008 09:40:10 -0700	1.4
--- modes.texi	14 Jun 2008 14:02:24 -0600	
***************
*** 779,784 ****
--- 779,787 ----
  the end of this docstring.  If you omit @var{docstring},
  @code{define-derived-mode} generates a documentation string.
  
+ If the parent mode has a @code{mode-class} property, the new mode's
+ @code{mode-class} property is given the same value.
+ 
  The @var{keyword-args} are pairs of keywords and values.  The values
  are evaluated.  The following keywords are currently supported:
  

Re: New special-mode parent

[Stefan Monnier]

>>> I think it would be nice is define-derived-mode automatically did this
>>> for modes derived from special-mode.

Stefan> Your wish was granted several years ago already,

> Thanks, I did not realize that.
> Here's a patch to update the documentation.

Feel free to install it,


        Stefan