bug? scroll-lock-mode and searching

bug? scroll-lock-mode and searching

[Werner LEMBERG]

[GNU Emacs 23.0.50.2 (i686-pc-linux-gnu, GTK+ Version 2.10.6) of
 2008-01-31]

Searching with C-s while scroll-lock-mode is active doesn't center the
search results.  I consider this a bug.  In case you decide this is a
`feature' I strongly ask for an option to configure scroll-lock-mode
so that isearch always centers its results.


    Werner

Re: bug? scroll-lock-mode and searching

[Ralf Angeli]

* Werner LEMBERG (2008-03-28) writes:

> Searching with C-s while scroll-lock-mode is active doesn't center the
> search results.  I consider this a bug.  In case you decide this is a
> `feature' I strongly ask for an option to configure scroll-lock-mode
> so that isearch always centers its results.

I'd consider it neither a bug nor a feature.  Scroll Lock mode is simply
not aware of Isearch mode and it probably doesn't need to be because a
search is not an explicit scrolling command.

For me the current behavior is fine, but if other people think it would
be a good idea for Scroll Lock mode to center search results, I would
not mind adding an option for it.

The only problem is that I could not find an appropriate hook in Isearch
mode which provides a means to recenter the view.  One could perhaps
abuse `isearch-message-function' for that but I don't consider this a
good idea.  Another bad idea would be to advise `isearch-update' like
this:

(defadvice isearch-update (after scroll-lock-isearch-update activate)
  "Recenter view after `isearch-update'."
  (recenter '(4)))

-- 
Ralf

Re: bug? scroll-lock-mode and searching

[Stefan Monnier]

>> Searching with C-s while scroll-lock-mode is active doesn't center the
>> search results.  I consider this a bug.  In case you decide this is a
>> `feature' I strongly ask for an option to configure scroll-lock-mode
>> so that isearch always centers its results.

> I'd consider it neither a bug nor a feature.  Scroll Lock mode is simply
> not aware of Isearch mode and it probably doesn't need to be because a
> search is not an explicit scrolling command.

> For me the current behavior is fine, but if other people think it would
> be a good idea for Scroll Lock mode to center search results, I would
> not mind adding an option for it.

> The only problem is that I could not find an appropriate hook in Isearch
> mode which provides a means to recenter the view.  One could perhaps
> abuse `isearch-message-function' for that but I don't consider this a
> good idea.  Another bad idea would be to advise `isearch-update' like
> this:

> (defadvice isearch-update (after scroll-lock-isearch-update activate)
>   "Recenter view after `isearch-update'."
>   (recenter '(4)))

I think the right fix is to introduce a new hook `before-redisplay-hook'
and scroll-lock-mode should use it.


        Stefan

Re: bug? scroll-lock-mode and searching

[Richard Stallman]

    I think the right fix is to introduce a new hook `before-redisplay-hook'
    and scroll-lock-mode should use it.

My experience suggests to me that hooks to run before or after
whateveritis are not quite the right thing for any complex feature.
I think that if you study what this feature is trying to do,
you'll probably find a different design that suits it better.

Re: bug? scroll-lock-mode and searching

[Stefan Monnier]

>     I think the right fix is to introduce a new hook `before-redisplay-hook'
>     and scroll-lock-mode should use it.

> My experience suggests to me that hooks to run before or after
> whateveritis are not quite the right thing for any complex feature.

Indeed.  But, for example, fontification-functions is just the right
thing for lazy font-lock.

> I think that if you study what this feature is trying to do,
> you'll probably find a different design that suits it better.

Could be.  The way I see it "scroll-lock-mode" is basically a mode where
the buffer should always be scrolled such that the cursor is always
maintained at the same (vertical) screen position.  So it very much has
to do with redisplay and `before-redisplay-hook' might be just the
right thing.  Then again, it's not clear what `before-redisplay-hook'
really is, so it may very well be that it won't work.  Especially since
auto-scrolling in response to point-motion seems to be
wickedly complex.


        Stefan