RE: context around incremental search

[Drew Adams]

> > Yes, set option `isearch-allow-scroll' to non-nil.
> 
> I don't think that's sufficient. I have this variable set to `t' and
> I saw found texts sticking to the bottom. Michael's hint needs to be
> follwed. Then there are few lines kept to the bottom.

Sufficient for what?  And what does your last sentence mean?
Please give a recipe or description, to explain what you mean.

The point of the option is to _allow_ scrolling commands/keys.  It
should be sufficient to set the option to non-nil, in order to let
you use `C-l', `C-v', etc. without exiting Isearch.  Is that not what
you see?

What Michael mentioned was something different, which has to do
with when the window is automatically recentered, based on how close
point is to the window top or bottom.  He was right to mention it,
in addition to `isearch-allow-scroll'.

The OP was a bit ambiguous.  Both things were hinted at:

* "I can't tell what's below it (using arrow keys or Ctrl-L to center
  the line)."  IOW, allow scrolling commands (i.e., on demand).

* "such that a selected item is always centered"  IOW, presumably
  _automatic_ scrolling to keep point in the center.

Two different behaviors.  Depends what one wants.

 - Drew, who toggles allowing scrolling on/off during Isearch, and
   who sets `scroll-margin' to 0