bug#17453: Isearch doesn't work properly with Follow Mode.

[Alan Mackenzie]

Hello, Artur.

On Mon, Nov 02, 2015 at 11:00:21PM +0000, Artur Malabarba wrote:
> On 2 Nov 2015 10:09 pm, "Alan Mackenzie" <acm@muc.de> wrote:
> > Of course, nothing is ever that simple.  ;-).  I've got a working
> > version which doesn't use "(sit-for 0)", thus allowing point to move
> > properly over Follow Mode windows.

> > However, this meant the "old" highlighting not being erased until the
> > 0.25 seconds had passed.  So I tried testing the conditions for a new
> > lazy-highlight loop (apart from window-start/end changing) in the
> > command loop bit.
> > It struck me that instead of all this rigmarole, and instead of the
> > "(sit-for 0)", we could test whether or not a scroll is about to take
> > place.

> Or we can cleanup the lazy highlighting _when_ scrolling takes place.

> > What we could do with is an interface which will tell us whether or not
> > redisplay would scroll if invoked immediately, with the current value of
> > point, window-start, etc.

> I don't think that's necessary. What if isearch just added
>  (lazy-highlight-cleanup t) to window-scroll-functions?

Now that's a good idea.  :-)

So stale lazy highlighting could be erased by the multitude of existing
tests for most cases, and by that hook function for when we scroll.  I'm
going to try it.

> I want to be very cautious about not increasing the complexity of isearch
> code here, but so far these sound like good refactorings to me.

I agree on both counts.

-- 
Alan Mackenzie (Nuremberg, Germany).