Feature request: custom link handlers

Feature request: custom link handlers

[Tom Weissmann]

This is basically a request to be able to create custom link handlers. 

For example, my `org-link-abbrev-alist' is this:

`(("wiki"   . org-link-abbrev-wiki)
  ("bmk"    . org-link-abbrev-bookmark)
  ("POA"    . org-link-abbrev-poa))


Only one of these actually returns a link that Org mode can use: wiki returns a
url. "bmk" opens a bookmark and "POA" opens another application; neither return
anything, so using them raises an error message.

One possibility would be to allow the link abbreviations to return two values:
nil and a message. `org-link-abbrev-poa' could then return 
'(nil 
  "Opening POA XYZ")
and Org mode wouldn't fret about not receiving a null link, but simply display
the message.

Another possibility would be to create a door to add custom link handlers with
custom completion - that way one could add bookmark links with minibuffer
completion...

Re: Feature request: custom link handlers

[Bastien]

Tom Weissmann <trmsw@yahoo.co.uk> writes:

> This is basically a request to be able to create custom link handlers. 
>
> For example, my `org-link-abbrev-alist' is this:
>
> `(("wiki"   . org-link-abbrev-wiki)
>   ("bmk"    . org-link-abbrev-bookmark)
>   ("POA"    . org-link-abbrev-poa))
>
>
> Only one of these actually returns a link that Org mode can use: wiki returns a
> url. "bmk" opens a bookmark and "POA" opens another application; neither return
> anything, so using them raises an error message.

I'm not sure to understand.  

For now `org-link-abbrev-alist' looks like:

'(("google" . "http://www.google.com/search?q=%s"))

where the cdr of each cell is a formatting string in which %s stand for
the text after "::" (or ":").  So for example :

  [[google::orgmode]]

is the abbreviated form of

  [[http://www.google.com/search?q=orgmode]]

Are you suggesting to replace "http://www.google.com/search?q=%s" by a
function that would handle the text after "::" in a different way than
`format' is currently doing?

I think a step by step example would be useful here.

-- 
Bastien

Re: Feature request: custom link handlers

[Tom Weissmann]

Bastien <bzg <at> altern.org> writes:

> Are you suggesting to replace "http://www.google.com/search?q=%s" by a
> function that would handle the text after "::" in a different way than
> `format' is currently doing?
No.

Here's an example. I sometimes create links to Emacs bookmarks, eg
"bmk:org-mode-tweaks"


The bmk abbreviation is expanded to a link Org mode understands, by
this function:



(defun org-link-abbrev-bookmark (bookmark)
"Opens a bookmark in another window"
  (bookmark-jump-other-window bookmark))

- which happens to return nil, NOT a link that Org mode understands,
  so even though it opens the bookmark I still get an error -
  essentially because I'm using a function that expands an
  abbreviation simply for its side effects.




If possible I would like Org mode to display a message like "Opening
bookmark org-mode-tweaks" instead of "if: Wrong type argument:
stringp, nil", which is why I suggested the multiple return value.


On the other hand I could return an elisp link and set
`org-confirm-elisp-link-function' to nil, to avoid having to confirm
every time I clicked one of these links


---

The other suggestion I realise doesn't make sense because when you
create a link with C-c C-l, the only minibuffer completion is of the
link type (file, new, mailto, etc.), not what follows.


It would be very cool to do C-c C-l, entry "bmk:" as the bookmark
type, and then have minibuffer completion of all the existing
bookmarks, but `org-store-link' works fine :)

Re: Re: Feature request: custom link handlers

[Bastien]

Tom Weissmann <trmsw@yahoo.co.uk> writes:

> Bastien <bzg <at> altern.org> writes:
>
>> Are you suggesting to replace "http://www.google.com/search?q=%s" by a
>> function that would handle the text after "::" in a different way than
>> `format' is currently doing?
> No.
>
> Here's an example. I sometimes create links to Emacs bookmarks, eg
> "bmk:org-mode-tweaks"

Thanks for the example.  

> It would be very cool to do C-c C-l, entry "bmk:" as the bookmark
> type, and then have minibuffer completion of all the existing
> bookmarks, but `org-store-link' works fine :)

I think what you are trying to achieve is better described as a new
hyperlink mechanism rather than an extension of abbrev links.

Check this:

(info "(org)Adding hyperlink types")

You can have a new hyperlink facility for bookmarked files.  When an a
buffer visiting a file, storing a link to this buffer would really store
a link to a bookmark, and when visiting a link to a bookmark Emacs will
find the bookmark.

What do you think?

-- 
Bastien

Re: Re: Feature request: custom link handlers

[Bastien]

Bastien <bzg@altern.org> writes:

>> type, and then have minibuffer completion of all the existing
>> bookmarks, but `org-store-link' works fine :)
>
> I think what you are trying to achieve is better described as a new
> hyperlink mechanism rather than an extension of abbrev links.

Sorry, should read: "as a new hyperlink type"...

-- 
Bastien

Re: Feature request: custom link handlers

[Tom Weissmann]

Bastien <bzg <at> altern.org> writes:

> > I think what you are trying to achieve is better described as a new
> > hyperlink mechanism rather than an extension of abbrev links.
> 
> Sorry, should read: "as a new hyperlink type"...

Yes. But a cheap alternative is just to let abbrev link functions return nil if
they want to.

Re: Re: Feature request: custom link handlers

[Bastien]

Tom Weissmann <trmsw@yahoo.co.uk> writes:

> Bastien <bzg <at> altern.org> writes:
>
>> > I think what you are trying to achieve is better described as a new
>> > hyperlink mechanism rather than an extension of abbrev links.
>> 
>> Sorry, should read: "as a new hyperlink type"...
>
> Yes. But a cheap alternative is just to let abbrev link functions
> return nil if they want to.

I find this a bit confusing to use a function that expands an
abbreviation only for its side effects.

But maybe you can just tell your function to return a string:

(defun org-link-abbrev-bookmark (bookmark)
  "Opens a bookmark in another window"
  (progn (bookmark-jump-other-window bookmark) ""))

No?

-- 
Bastien

Re: Feature request: custom link handlers

[Tom Weissmann]

Bastien <bzg <at> altern.org> writes:

> I find this a bit confusing to use a function that expands an
> abbreviation only for its side effects.

Yes. It would be nice to be able to add custom link handlers and define
completion functions for them :)

> But maybe you can just tell your function to return a string:
...
> No?

oops! I tried that before and it kept moving me back to the beginning of my org
file, whereas now it, um, doesn't. Can't see for the egg on my face.

Re: Feature request: custom link handlers

[Tom Weissmann]

Tom Weissmann <trmsw <at> yahoo.co.uk> writes:

> oops! I tried that before and it kept moving me back to the beginning of my org
> file, whereas now it, um, doesn't. Can't see for the egg on my face.

In the meantime I discovered `org-add-link-type' which does everything I want
except the completions.

Re: Re: Feature request: custom link handlers

[Bastien]

Tom Weissmann <trmsw@yahoo.co.uk> writes:

> Tom Weissmann <trmsw <at> yahoo.co.uk> writes:
>
>> oops! I tried that before and it kept moving me back to the beginning of my org
>> file, whereas now it, um, doesn't. Can't see for the egg on my face.
>
> In the meantime I discovered `org-add-link-type' which does everything I want
> except the completions.

Yes.  Go and read the example about adding link type in the manual, I'm
pretty sure it will help you doing what you want.

-- 
Bastien