Persisting centered cursor with Scroll Lock key

Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

I want to achieve the following: When Scroll Lock is active,
i.e. when the respective keyboard diode is on, the cursor is always
in the centre of the frame.

I think I can do this myself, with something like

(global-set-key [Scroll_Lock] (whatever))

but what is the most elegant/safest way to keep the cursor in the
center of the window, no matter how the position is changed (arrow
keys, control key sequences, mouse wheel etc)?

Thank you!

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[Kai Grossjohann]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> I want to achieve the following: When Scroll Lock is active,
> i.e. when the respective keyboard diode is on, the cursor is always
> in the centre of the frame.

There is scroll-in-place.el by Eric Eide (I think, could be another
member of the Eric conspiracy) which allows you to keep the cursor
where it is.  Maybe that's close enough?

Kai

Re: Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

Kai Grossjohann <kai@emptydomain.de> writes:

> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>
>> I want to achieve the following: When Scroll Lock is active,
>> i.e. when the respective keyboard diode is on, the cursor is
>> always in the centre of the frame.
>
> There is scroll-in-place.el by Eric Eide (I think, could be
> another member of the Eric conspiracy) which allows you to keep
> the cursor where it is.  Maybe that's close enough?

I've installed scroll-in-place.el and added (require
'scroll-in-place) to my .emacs.  This .emacs doesn't contain any
other scroll setting commands except for (setq scroll-step 1) (as
far as I can see), *and* the (require 'scroll-in-place) is almost
the last command in the file.  But there is no effect nevertheless.

scroll-in-place is 1, which means that the fuctions are supposed to
be active.

Any ideas?

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[upro]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> Halloechen!
>
> Kai Grossjohann <kai@emptydomain.de> writes:
>
>> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>>
>>> I want to achieve the following: When Scroll Lock is active,
>>> i.e. when the respective keyboard diode is on, the cursor is
>>> always in the centre of the frame.
>>
>> There is scroll-in-place.el by Eric Eide (I think, could be
>> another member of the Eric conspiracy) which allows you to keep
>> the cursor where it is.  Maybe that's close enough?
>
> I've installed scroll-in-place.el and added (require
> 'scroll-in-place) to my .emacs.  This .emacs doesn't contain any
> other scroll setting commands except for (setq scroll-step 1) (as
> far as I can see), *and* the (require 'scroll-in-place) is almost
> the last command in the file.  But there is no effect nevertheless.
>
> scroll-in-place is 1, which means that the fuctions are supposed to
> be active.
>
> Any ideas?
>
> Tschoe,
> Torsten.

Yeah , I had the same whish and finalle achieved a similar but more
sophisitaced behavior by the following, without using scroll-in-place:

(defun scroll-down-one-line (arg)
  "Scroll down one line, or number of lines specified by prefix arg."
  (interactive "P")
  (let ((scroll-default-lines 1))
    (scroll-down-in-place arg)))
(defun scroll-up-one-line (arg)
  "Scroll down one line, or number of lines specified by prefix arg."
  (interactive "P")
  (let ((scroll-default-lines 1))
    (scroll-up-in-place arg)))

(global-set-key  [(shift up)] 'scroll-down-one-line)
(global-set-key [(shift down)] 'scroll-up-one-line)


Now emacs scrolls as normal when using the arrow keys, but scrolls
with fixed cursir, around the cursor when I use the arrow
keys+shift. You can bind it to arrow keys only, of course...


Nothing to do with your scroll-lock lamp or function or whatsoever,
whatsoever...


Does this help?

-- 
Michael

r-znvy: zvpunry.wryqra  jro.qr (chg gur "@" jurer vg svgf...)
ab fcnz cyrnfr

Re: Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

upro <upro@gmx.net> writes:

> [...]
>
> Now emacs scrolls as normal when using the arrow keys, but scrolls
> with fixed cursir, around the cursor when I use the arrow
> keys+shift. You can bind it to arrow keys only, of course...
>
> Nothing to do with your scroll-lock lamp or function or
> whatsoever, whatsoever...
>
> Does this help?

Not really, because I intend to use this scroll-lock feature as
default behaviour for certain file types.  And usually I use
PgUp/PgDown, the arrow keys, incremental search, and the mouse wheel
for navigating within my files, and the goal is to have the cursor
always in the centre line.

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[upro]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> Halloechen!
>
> upro <upro@gmx.net> writes:
>
>> [...]
>>
>> Now emacs scrolls as normal when using the arrow keys, but scrolls
>> with fixed cursir, around the cursor when I use the arrow
>> keys+shift. You can bind it to arrow keys only, of course...
>>
>> Nothing to do with your scroll-lock lamp or function or
>> whatsoever, whatsoever...
>>
>> Does this help?
>
> Not really, because I intend to use this scroll-lock feature as
> default behaviour for certain file types.  And usually I use
> PgUp/PgDown, the arrow keys, incremental search, and the mouse wheel
> for navigating within my files, and the goal is to have the cursor
> always in the centre line.
>
> Tschoe,
> Torsten.


You would probably have to edit the respective modes to modify the
scroll behaviour then...

Or one of the gurus gives you, well, us a hint...

Tschüßle!
-- 
Michael

r-znvy: zvpunry.wryqra  jro.qr (chg gur "@" jurer vg svgf...)
ab fcnz cyrnfr

Re: Persisting centered cursor with Scroll Lock key

[Kai Grossjohann]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> I've installed scroll-in-place.el and added (require
> 'scroll-in-place) to my .emacs.  This .emacs doesn't contain any
> other scroll setting commands except for (setq scroll-step 1) (as
> far as I can see), *and* the (require 'scroll-in-place) is almost
> the last command in the file.  But there is no effect nevertheless.

Hm.  This is bad.

(Btw, I think you can see the effect by doing C-u 1 C-v and then
repeatedly hitting C-v -- did you try that and what happens?  Just
moving point with C-n and its ilk behaves as before, I think.)

Kai

Re: Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

Kai Grossjohann <kai@emptydomain.de> writes:

> [...]
>
> (Btw, I think you can see the effect by doing C-u 1 C-v and then
> repeatedly hitting C-v -- did you try that and what happens?  Just
> moving point with C-n and its ilk behaves as before, I think.)

Yes, C-u 1 and then PgUp/PgDn is what I want to see.

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[Kai Grossjohann]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> Yes, C-u 1 and then PgUp/PgDn is what I want to see.

Does this mean that scroll-in-place works after all?

So what you now need is to define single-line scrolling commands.
Then you need to rebind keys C-n, C-p and so on to use the scrolling
commands instead of previous-line and next-line, and so on.

Then you need to write a function which does this and another which
undoes it, and then bind a command to the scroll-lock key which calls
one or the other function.

Hm.  CVS Emacs has a feature where you can rebind commands instead of
keys.  This means you could rebind the previous-line command and thus
simultaneously change all keys that invoke previous-line.  Maybe this
helps?

Kai

Re: Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

Kai Grossjohann <kai@emptydomain.de> writes:

> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>
>> Yes, C-u 1 and then PgUp/PgDn is what I want to see.
>
> Does this mean that scroll-in-place works after all?

Well, I can see the effect, but C-u 1 PgUp is not my usual way to
scroll.  ;)

The point is that scroll *lock* means to me that whatever I do,
whatever I try, the cursor sticks to the centred position, and only
the file moves.

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[Eric Eide]

"Kai" == Kai Grossjohann <kai@emptydomain.de> writes:

	Kai> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
	>> Yes, C-u 1 and then PgUp/PgDn is what I want to see.

	Kai> Does this mean that scroll-in-place works after all?

Probably.

	Kai> So what you now need is to define single-line scrolling commands.

The comments in the `scroll-in-place.el' file talk about doing this, and give
some sample code.

	Kai> Then you need to rebind keys C-n, C-p and so on to use the
	Kai> scrolling commands instead of previous-line and next-line, and so
	Kai> on.
	Kai> 
	Kai> Then you need to write a function which does this and another
	Kai> which undoes it, and then bind a command to the scroll-lock key
	Kai> which calls one or the other function.

"This is left as an exercise for the reader." :-).

Eric.

-- 
-------------------------------------------------------------------------------
Eric Eide <eeide@cs.utah.edu>  .         University of Utah School of Computing
http://www.cs.utah.edu/~eeide/ . +1 (801) 585-5512 voice, +1 (801) 581-5843 FAX

Re: Persisting centered cursor with Scroll Lock key

[Thien-Thi Nguyen]

Eric Eide <eeide@cs.utah.edu> writes:

> "This is left as an exercise for the reader." :-).

i use scroll-in-place wrapped to work w/ M-n and M-p:

 http://www.glug.org/people/ttn/software/ttn-pers-elisp/
        dist/lisp/editing/tucky-holdcursor.el

also, to make C-l respect and be able to set a "recenter
gravity", i use an anonymous lambda defined in:

 http://www.glug.org/people/ttn/software/ttn-pers-elisp/
        dist/lisp/core/keys.el

(two urls, both split.  look for the slow banjo joke for
the latter functionality.)  actually, on second look, the
C-l does a lot of other stuff, too -- i must have been
extremely twisted at the time.  emacs is a trip...

thi

Re: Persisting centered cursor with Scroll Lock key

[Eric Eide]

"Torsten" == Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

	Torsten> I've installed scroll-in-place.el and added (require
	Torsten> 'scroll-in-place) to my .emacs.  This .emacs doesn't contain
	Torsten> any other scroll setting commands except for (setq scroll-step
	Torsten> 1) (as far as I can see), *and* the (require 'scroll-in-place)
	Torsten> is almost the last command in the file.  But there is no
	Torsten> effect nevertheless.  [...]
	Torsten> 
	Torsten> Any ideas?

My first thought is that `scroll-in-place' is working, but that it's not doing
what you expect it to do.

In your original post, you asked for a way to keep the cursor (a.k.a. point) in
the middle of the window, no matter how point is caused to move within the
buffer.  That's not quite what `scroll-in-place' does.

The `scroll-in-place' package tries to keep point at its current visual
position --- whatever that happens to be --- across scrolling commands, and
*only* across scrolling commands (i.e., keys like PageUp, PageDown, C-v, and
M-v).  This is different than staying in the *middle* for *any* command.  For
instance, with `scroll-in-place' loaded, commands like `next-line' and
`previous-line' (keys like C-n, down-arrow, C-p, and up-arrow) still cause the
visual position of point to move.

(As an aside, I'll point out that even for scrolling commands, the "in-place"
behavior is subject to certain boundary conditions, e.g., at the ends of a
buffer, on short lines, etc.)

Here's a test to see if the package is working at all.  Load a large file
(several windows-full) and go to the beginning, so that the cursor is on the
first line of the window.  Now hit PageDown (or C-v) a few times, then hit
PageUp (or M-v) the same number of times.  If the package is loaded and
working, then the cursor should be back at the beginning of the window.  If the
package isn't loaded or isn't working, then point should be somewhere near the
bottom of the window.

My second thought is that there might be some other error in your `.emacs'
file, so the command that loads `scroll-in-place' isn't being executed.  (You
said that the `scroll-in-place' stuff is near the end of your `.emacs'.  If
Emacs finds an error in your `.emacs' file, then it stop processing at that
point --- and so the stuff at the end might not be run.)

You can check to see if the package is loaded in a number of ways.  Perhaps the
most straightforward way is to ask for the documentation of function
`scroll-window': type `M-x describe-function RET scroll-window RET'.  If the
documentation mentions `scroll-in-place', then the package is loaded.  If it
doesn't, or if the function isn't defined at all, then the package is not
loaded.

Finally, it's certainly possible that the package isn't working in your Emacs
for some reason, but I would need more details to figure out why.  What version
of Emacs are you using?  Does it work if you run Emacs without your `.emacs'
file (run `emacs -q' and then load the package manually (e.g., via `M-x
load-library')?

Thanks, and good luck! ---

Eric.

-- 
-------------------------------------------------------------------------------
Eric Eide <eeide@cs.utah.edu>  .         University of Utah School of Computing
http://www.cs.utah.edu/~eeide/ . +1 (801) 585-5512 voice, +1 (801) 581-5843 FAX

Re: Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

Eric Eide <eeide@cs.utah.edu> writes:

> "Torsten" == Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>
> 	Torsten> I've installed scroll-in-place.el and added
> 	Torsten> (require 'scroll-in-place) to my .emacs.  This
> 	Torsten> .emacs doesn't contain any other scroll setting
> 	Torsten> commands except for (setq scroll-step 1) (as far as
> 	Torsten> I can see), *and* the (require 'scroll-in-place) is
> 	Torsten> almost the last command in the file.  But there is
> 	Torsten> no effect nevertheless.  [...]
> 	Torsten> 
> 	Torsten> Any ideas?
>
> My first thought is that `scroll-in-place' is working, but that
> it's not doing what you expect it to do.
>
> [...]
>
> The `scroll-in-place' package tries to keep point at its current
> visual position --- whatever that happens to be --- across
> scrolling commands, and *only* across scrolling commands (i.e.,
> keys like PageUp, PageDown, C-v, and M-v).  [...]

Yes, the package is apparently working with my Emacs, but I can have
the same behaviour with (setq scroll-preserve-screen-position t),
can't I?

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[Eric Eide]

"Torsten" == Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

	Torsten> Yes, the [`scroll-in-place'] package is apparently working
	Torsten> with my Emacs, but I can have the same behaviour with (setq
	Torsten> scroll-preserve-screen-position t), can't I?

I believe that the behaviors are similar but not the same.  Unfortunately, I
don't remember the exact differences in the behaviors of the two systems.

The `scroll-in-place' package predates `scroll-preserve-screen-position', and
since I've always been an avid user of `scroll-in-place' :-), I haven't spent
much time figuring out the policy was later implemented by `scroll-preserve-
screen-position'.

I suppose I should figure it out, though!

Eric.

-- 
-------------------------------------------------------------------------------
Eric Eide <eeide@cs.utah.edu>  .         University of Utah School of Computing
http://www.cs.utah.edu/~eeide/ . +1 (801) 585-5512 voice, +1 (801) 581-5843 FAX

Re: Persisting centered cursor with Scroll Lock key

[Stefan Monnier]

Torsten> with my Emacs, but I can have the same behaviour with (setq
Torsten> scroll-preserve-screen-position t), can't I?
> I believe that the behaviors are similar but not the same.

Indeed.  I think it was one of those "5% of the work for 70% of the
behavior".  As for the original poster, he might also want to take a look
at scroll-margin.

In any case determining if scroll-lock is pressed or not doesn't seem to be
easy from elisp.


        Stefan

Re: Persisting centered cursor with Scroll Lock key

[Kai Grossjohann]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> In any case determining if scroll-lock is pressed or not doesn't seem to be
> easy from elisp.

I get <key-20> when I hit scroll-lock.  Or <Scroll_Lock>.

Kai

Re: Persisting centered cursor with Scroll Lock key

[Stefan Monnier]

>> In any case determining if scroll-lock is pressed or not doesn't seem to be
>> easy from elisp.
> I get <key-20> when I hit scroll-lock.  Or <Scroll_Lock>.

Is that when you turn it ON or OFF ?


        Stefan

Re: Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>> In any case determining if scroll-lock is pressed or not doesn't seem to be
>>> easy from elisp.
>>
>> I get <key-20> when I hit scroll-lock.  Or <Scroll_Lock>.
>
> Is that when you turn it ON or OFF ?

My OS configuration keeps it off anyway.  ;)

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[Kai Grossjohann]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>> In any case determining if scroll-lock is pressed or not doesn't seem to be
>>> easy from elisp.
>> I get <key-20> when I hit scroll-lock.  Or <Scroll_Lock>.
>
> Is that when you turn it ON or OFF ?

;-)  In both cases.  But it's off initially...

Kai

Re: Persisting centered cursor with Scroll Lock key

[Torsten Bronger]

Halloechen!

Kai Grossjohann <kai@emptydomain.de> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>>>> In any case determining if scroll-lock is pressed or not
>>>> doesn't seem to be easy from elisp.
>>>
>>> I get <key-20> when I hit scroll-lock.  Or <Scroll_Lock>.
>>
>> Is that when you turn it ON or OFF ?
>
> ;-)  In both cases.  But it's off initially...

But then you musn't press it while Emacs has not the focus.?

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus

Re: Persisting centered cursor with Scroll Lock key

[Kai Grossjohann]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> Halloechen!
>
> Kai Grossjohann <kai@emptydomain.de> writes:
>
>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>
>>>>> In any case determining if scroll-lock is pressed or not
>>>>> doesn't seem to be easy from elisp.
>>>>
>>>> I get <key-20> when I hit scroll-lock.  Or <Scroll_Lock>.
>>>
>>> Is that when you turn it ON or OFF ?
>>
>> ;-)  In both cases.  But it's off initially...
>
> But then you musn't press it while Emacs has not the focus.?

Shhh!  Don't tell anyone!

Kai

Re: Persisting centered cursor with Scroll Lock key

[Eric Eide]

"Kai" == Kai Grossjohann <kai@emptydomain.de> writes:

	Kai> There is scroll-in-place.el by Eric Eide (I think, could be
	Kai> another member of the Eric conspiracy) [...]

Yes, by me, but I can neither confirm or deny any involvement with this alleged
Eric Conspiracy <http://www.catb.org/~esr/ecsl/>.  Just trust us.  No comment.

-- 
-------------------------------------------------------------------------------
Eric Eide <eeide@cs.utah.edu>  .         University of Utah School of Computing
http://www.cs.utah.edu/~eeide/ . +1 (801) 585-5512 voice, +1 (801) 581-5843 FAX

Re: Persisting centered cursor with Scroll Lock key

[Johan Bockgård]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> but what is the most elegant/safest way to keep the cursor in the
> center of the window, no matter how the position is changed (arrow
> keys, control key sequences, mouse wheel etc)?

This might work:

(defun my-recenter ()
  (recenter '(4)))

;; buffer local hook, excute in the buffers where you want it to be
;; active
(add-hook 'post-command-hook 'my-recenter t t)

-- 
Johan Bockgård