How to execute code on cursor move

How to execute code on cursor move

[Suvayu Ali]

Hi,

I want to check a text property and display in the minibuffer depending
on context (in my case, on an org-link).

This is what I have so far (working):

(add-hook 'post-command-hook
	  (lambda()
	    (if (eq (get-text-property (point) 'face) 'org-link)
		(display-message-or-buffer
		 (get-text-property (point) 'help-echo)))))

Is using the post-command-hook a good idea?  Is there something better?
As you can see, I'm trying to get the link target; are there better ways
to do this?

Thanks for any ideas.

-- 
Suvayu

Open source is the future. It sets us free.

Re: How to execute code on cursor move

[Eli Zaretskii]

> Date: Sat, 13 Jul 2013 12:39:03 +0200
> From: Suvayu Ali <fatkasuvayu+linux@gmail.com>
> 
> I want to check a text property and display in the minibuffer depending
> on context (in my case, on an org-link).
> 
> This is what I have so far (working):
> 
> (add-hook 'post-command-hook
> 	  (lambda()
> 	    (if (eq (get-text-property (point) 'face) 'org-link)
> 		(display-message-or-buffer
> 		 (get-text-property (point) 'help-echo)))))
> 
> Is using the post-command-hook a good idea?

No, because it slows down Emacs's _every_ command.

> Is there something better?

There are the 'point-entered' and 'point-left' text properties.  Make
sure they cover the buffer positions where you want to display the
message in the echo area, and the rest should be easy.

RE: How to execute code on cursor move

[Drew Adams]

> > I want to check a text property and display in the minibuffer depending
> > on context (in my case, on an org-link).
> >
> > (add-hook 'post-command-hook
> > 	  (lambda()
> > 	    (if (eq (get-text-property (point) 'face) 'org-link)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > Is using the post-command-hook a good idea?
> 
> No, because it slows down Emacs's _every_ command.
> 
> > Is there something better?
> 
> There are the 'point-entered' and 'point-left' text properties.  Make
> sure they cover the buffer positions where you want to display the
> message in the echo area, and the rest should be easy.

Remember too that the `face' property can be a cons of faces or face
attributes.  So you might not want to test for `org-link' using only `eq'.
IOW, you might want something like this, to check for the presence of
face `org-link':

(let ((face  (get-text-property (point) 'face)))
  (or (eq 'org-link face)
      (and (consp face)  (memq 'org-link face))))

Re: How to execute code on cursor move

[Suvayu Ali]

Hi Eli,

On Sat, Jul 13, 2013 at 02:03:33PM +0300, Eli Zaretskii wrote:
> > Date: Sat, 13 Jul 2013 12:39:03 +0200
> > From: Suvayu Ali <fatkasuvayu+linux@gmail.com>
> > 
> > I want to check a text property and display in the minibuffer depending
> > on context (in my case, on an org-link).

 [...chomp...chomp...chomp...]

> > Is using the post-command-hook a good idea?
> 
> No, because it slows down Emacs's _every_ command.

Thank you, I had a feeling that is the case.

> > Is there something better?
> 
> There are the 'point-entered' and 'point-left' text properties.  Make
> sure they cover the buffer positions where you want to display the
> message in the echo area, and the rest should be easy.

I have the following snippet based on what you say above:

----------8<--------------------8<----------
;; Text for testing
;; some text description some more

;; setup: add tooltip
(add-text-properties 34 45
		     '(help-echo "tooltip"))

;; test above setup: tooltip b/w 34-45
(get-text-property 40 'help-echo)

;; add special properties
(defun sa-echo-tooltip (old new)
  (display-message-or-buffer (or (get-text-property new 'help-echo) "")))

(add-text-properties
 34 45 '(point-left sa-echo-tooltip point-entered sa-echo-tooltip))
----------8<--------------------8<----------

Now to convert this to something workable I guess I would have to add
the point-left and point-entered properties to all org-links.  I'm not
sure how I can do that, but I guess asking on the Org mode list will be
best.

Thanks a lot!

-- 
Suvayu

Open source is the future. It sets us free.

Re: How to execute code on cursor move

[Suvayu Ali]

Hi Drew,

On Sat, Jul 13, 2013 at 06:26:24AM -0700, Drew Adams wrote:
> > > I want to check a text property and display in the minibuffer depending
> > > on context (in my case, on an org-link).
> > >
> > > (add-hook 'post-command-hook
> > > 	  (lambda()
> > > 	    (if (eq (get-text-property (point) 'face) 'org-link)
>                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > Is using the post-command-hook a good idea?
> > 
> > No, because it slows down Emacs's _every_ command.
> > 
> > > Is there something better?
> > 
> > There are the 'point-entered' and 'point-left' text properties.  Make
> > sure they cover the buffer positions where you want to display the
> > message in the echo area, and the rest should be easy.
> 
> Remember too that the `face' property can be a cons of faces or face
> attributes.  So you might not want to test for `org-link' using only `eq'.
> IOW, you might want something like this, to check for the presence of
> face `org-link':
> 
> (let ((face  (get-text-property (point) 'face)))
>   (or (eq 'org-link face)
>       (and (consp face)  (memq 'org-link face))))
> 

I actually saw something very similar in Org mode source but didn't
quite follow everything, so I "simplified" it to what you see
above.  :-p

Thank you very much for the pointer.  Now I understand :).  

Cheers,

-- 
Suvayu

Open source is the future. It sets us free.