Proper use of `deactivate-mark'?

Proper use of `deactivate-mark'?

[Thorsten Jolitz]

Hi List, 

in a function I switch from buffer A to buffer B, mark the
thing-at-point, do something with it, conditional on

  ,--------------------
  | (and
  |  (use-region-p) ...
  `--------------------


, then call `(deactivate-mark)' at the end of the function and switch
back to buffer A again.

But the next time I switch to buffer B, the mark that was region-end
before seems to be still active - the region between that mark and the
actual point position is highlighted also I did not set any new mark
again. 

Isn't that the appropriate use of `deactivate-mark'?
How can I make sure that no mark is active anymore when I'm done in
buffer B and switch back to buffer A?

-- 
cheers,
Thorsten

Re: Proper use of `deactivate-mark'?

[Stefan Monnier]

> Isn't that the appropriate use of `deactivate-mark'?

Sounds right, yes.

> How can I make sure that no mark is active anymore when I'm done in
> buffer B and switch back to buffer A?

Not sure why the mark is re-activated.  Could be because you call
deactivate-mark from with a save-excursion.


        Stefan

Re: Proper use of `deactivate-mark'?

[Thorsten Jolitz]

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

>> Isn't that the appropriate use of `deactivate-mark'?
>
> Sounds right, yes.
>
>> How can I make sure that no mark is active anymore when I'm done in
>> buffer B and switch back to buffer A?
>
> Not sure why the mark is re-activated.  Could be because you call
> deactivate-mark from with a save-excursion.

Not really, but I found the culprit:

Inside the (and ...) deactivate-mark does not do its work properly (does
copy-to-register return nil?)

  ,-------------------------------------------------------
  | (and
  |  (use-region-p)
  |  (copy-to-register ?s (region-beginning) (region-end))
  |  (deactivate-mark) )
  `-------------------------------------------------------

but refactored like this the mark is actually deactivated:

  ,---------------------------------------------------------
  | (and
  |  (use-region-p)
  |  (copy-to-register ?s (region-beginning) (region-end)) )
  | (deactivate-mark)
  `---------------------------------------------------------

-- 
cheers,
Thorsten

Re: Proper use of `deactivate-mark'?

[Michael Heerdegen]

Thorsten Jolitz <tjolitz@gmail.com> writes:

> Inside the (and ...) deactivate-mark does not do its work properly (does
> copy-to-register return nil?)

The return value is unspecified, which means it can be anything.  And
yes, in your use case it returns nil, which means you should not use
`and' in your example.

Michael.

Re: Proper use of `deactivate-mark'?

[Barry Margolin]

In article <mailman.14992.1392314356.10748.help-gnu-emacs@gnu.org>,
 Thorsten Jolitz <tjolitz@gmail.com> wrote:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
> 
> >> Isn't that the appropriate use of `deactivate-mark'?
> >
> > Sounds right, yes.
> >
> >> How can I make sure that no mark is active anymore when I'm done in
> >> buffer B and switch back to buffer A?
> >
> > Not sure why the mark is re-activated.  Could be because you call
> > deactivate-mark from with a save-excursion.
> 
> Not really, but I found the culprit:
> 
> Inside the (and ...) deactivate-mark does not do its work properly (does
> copy-to-register return nil?)
> 
>   ,-------------------------------------------------------
>   | (and
>   |  (use-region-p)
>   |  (copy-to-register ?s (region-beginning) (region-end))
>   |  (deactivate-mark) )
>   `-------------------------------------------------------
> 
> but refactored like this the mark is actually deactivated:
> 
>   ,---------------------------------------------------------
>   | (and
>   |  (use-region-p)
>   |  (copy-to-register ?s (region-beginning) (region-end)) )
>   | (deactivate-mark)
>   `---------------------------------------------------------

Maybe it should be:

(and 
  (use-region-p)
  (progn
    (copy-to-register ?s (region-beginning) (region0end))
    (deactivate-mark)))

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: Proper use of `deactivate-mark'?

[Thorsten Jolitz]

Barry Margolin <barmar@alum.mit.edu> writes:

> Maybe it should be:
>
> (and 
>   (use-region-p)
>   (progn
>     (copy-to-register ?s (region-beginning) (region0end))
>     (deactivate-mark)))

Yes, that looks like my intention translated into code - thanks.

-- 
cheers,
Thorsten

Re: Proper use of `deactivate-mark'?

[Kevin Rodgers]

On 2/13/14 11:07 AM, Barry Margolin wrote:
> Maybe it should be:
>
> (and
>    (use-region-p)
>    (progn
>      (copy-to-register ?s (region-beginning) (region0end))
>      (deactivate-mark)))

;; http://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node84.html
;; As a matter of style, `when' is normally used to conditionally produce
;; some side effects, and the value of the when form is normally not
;; used. If the value is relevant, then it may be stylistically more
;; appropriate to use `and' or `if'.

(when (use-region-p)
   (copy-to-register ?s (region-beginning) (region0end))
   (deactivate-mark))

-- 
Kevin Rodgers
Denver, Colorado, USA