bug#17453: Framework extending window functions for Follow Mode (etc.).

[Alan Mackenzie]

Hello, Juri.

On Wed, Nov 18, 2015 at 02:38:49AM +0200, Juri Linkov wrote:
> > ...., I now think the best name would be the last of these three,
> > window-group-start.  It is not too long, and the phrase "window_group"
> > fits in with all the primitives apart from `recenter'.  So we'd need some
> > different naming ideas, perhaps "recenter-group" or "group-recenter".

> For consistency with other related names it could have the same prefix, e.g.
> "window-group-recenter".

Or even "recenter-window-group", since "window-group" isn't strictly a
prefix in a lot of the other cases anyway.

> > By the way, have you had the chance to look at the changes I made to
> > isearch.el in the scratch/follow branch?

> One thing in the isearch-related part of your patch that I'm not excited about
> is the macro isearch-call-message.  With Stefan's request there is no need in 
> it
> since it becomes one-liner: (funcall isearch-message-function).

A minor thing, which I will amend this evening.

> Another thing that disturbs me is moving lazy-highlighting checks
> to a new function isearch-lazy-highlight-maybe-new-loop.

What disturbs you about this change in particular?

> What do you think about moving only window-checking into new function
> i.e. only checks for window-start/window-end/etc that need (sit-for 0)
> and leaving other checks in isearch-lazy-highlight-new-loop?

Actually, I think that "(sit-for 0)" isn't needed - I left it in to deal
with isearch-lazy-highlight-initial-delay being set to 0, thinking that
Follow Mode's post-command-hook might "not have had time" to run.  But
surely post-command-hook will be called before checking timers.  I'll
need to look at the source code (probably keyboard.c) to be absolutely
sure of this.

I don't think splitting the checks between
isearch-lazy-highlight-new-loop (in the command loop) and a function
triggered by a timer is a good idea.  I tried it out, and it kind of
jars when the lazy highlighting sometimes stays 0.25s, sometimes goes
instantly.  How about maybe ...

How about maybe putting the test for new highlighting in Isearch's
post-command-hook (and using the APPEND argument of `add-hook' to make
sure Isearch's post-hook-function comes after Follow Modes's)?  That
way, all the lazy h. would be removed immediately after the command, as
at present.

> Would this help to avoid new problems such as un-highlighting
> postponed until the timer fires?

Is this actually a problem?  I played with Emacs a little with that
un-highlighting strategy, and didn't find it any more disturbing than
the 0.25s gap between old highlighting going and new highlighting
arriving.

-- 
Alan Mackenzie (Nuremberg, Germany).