Re: A couple of emacs lisp questions

[Daniel Dalton]

Hi Drew, 

Thanks so much for the detailed response. Please see my comments below. 
On Tue, Dec 21, 2010 at 10:12:03AM -0800, Drew Adams wrote:
> > 1. I need to make 5 or 6 key bindings. I presume the way to do this is
> > to create a prefix and then put my bindings under this. So perhaps the
> > prefix could be c-c c-l and then I can create key bindings to trigger
> > certain functions i.e.e c-c c-l t toggles the functionality on/off.
> > How would I implement something like this?
> 
> C-h r i  prefix key RET takes you to the Emacs manual node `Prefix Keys', 
> which
> provides some help.
> 

I shall take a look.

> ;; Define a keymap variable for your prefix-key commands:
> (defvar my-map () "My prefix key.")
> 
> ;; Define the keymap as a prefix-key command:
> (define-prefix-command 'my-map)
> 
> That defines `my-map' as a command whose function definition and whose value 
> are
> the same, new (empty) keymap.  More info:
> 
> C-h f define-prefix-command
> C-h v my-map
> C-h f my-map
> 
> ;; Bind command `my-map' to a key - the prefix key:
> (global-set-key "\C-c\C-l" 'my-map)
> 
> ;; Bind cmds `foo' & `bar' to `a' & `b' following the prefix key:
> (define-key my-map "a" 'foo)
> (define-key my-map "b" 'bar)

Oh, that all seems to be fairly logical and make sense.

> > How could I record the current key bindings which use c-c c-l as a
> > prefix, and then restore them upon exit of the latex-access
> > stuff. I.e. when it is disabled.
> > Note, that I haven't created a minor or major mode, I'm just 
> > using hooks
> > and advice as well as interactive functions to make my work available
> > under emacs.
> 
> OK, let's start over from a clean slate (new Emacs session, to get rid of
> bindings etc. we created).
> 
> You don't want the prefix key defined globally, but just in your (minor) mode.

Are you suggesting I should make my code into a minor mode? What work is
involved to do this? Perhaps I should look at the docs. Currently I just
have about a dozen different functions, most interactive which are
called when necessary. I use hooks and advice to make my code
execute... How different would my implementation have to be if I built a
minor mode? Would I have to change much? And what benefits would there
 be in doing this?

> ;; Create a keymap for your minor mode, and define the mode.
> (defvar latax-mode-map (make-sparse-keymap)
>   "LaTeX access minor mode keymap.")
> 
> (define-minor-mode latax-mode "LaTeX access mode."
>   nil " LaTax" latax-mode-map)
> 

What is the Latax-mode stuff for? I thought we are creating a minor mode
for latex-access?

> ;; Create the prefix-key keymap.
> (defvar latax-prefix-map nil
>   "LaTeX access mode prefix keymap.")
> 
> ;; Bind command `latax-prefix-map' to `C-c C-l' in `latex-mode-map':
> (define-key latax-mode-map "\C-c\C-l" 'latax-prefix-map)
> 
> ;; Bind other commands in the prefix map:
> (define-key latax-prefix-map "a" 'forward-char)
> (define-key latax-prefix-map "b" 'emacs-version)
> 
> Turn on/off the minor mode: `M-x latax-mode'.

Oh I think I understand now. So where should this code go? In a
particular function definition? Or just straight in the .el
file. Currently I have 3 or 4 toggling functions, to change different
behaviour of the mode, could I still use these? When the mode is
disabled, I suppose all my interactive latex-access functions would
still be available though through m-x?

> Dunno. Sounds like you should just display another buffer (always), and send 
> the
> output you want there.  See `with-current-buffer' and the like.

I think that sounds like a good idea.

> 
> For fitting the window to the buffer, see `resize-temp-buffer-window' and
> `fit-window-to-buffer'.
> 
> You can also use a separate frame for the buffer - see 
> `special-display-regexps'

I had a play, only thing that was a bit annoying, which I wouldn't mind
removing is the header and mode lines from the output buffer... I was
just using a standard buffer, is this different for temp buffer? If I
use a temp buffer, won't it get destroyed or have I misunderstood the
temp buffer setup? 

> and `special-display-buffer-names'.  If you do that, you can use `fit-frame' 
> in
> library `fit-frame.el' to fit the frame to the buffer.
> http://www.emacswiki.org/emacs/FrameModes#ShrinkWrappedFrames

That's something else I will checkout for sure. 

I'm probably going to have a go at implementing this in the next week or
so (after Christmas), may I contact you directly if I run into problems? 

Once again thanks very much for your comprehensive response!

Kind regards,
Daniel Dalton