Re: The future of Follow Mode - a proposal.

[Alan Mackenzie]

Hello, Eli.

On Thu, Feb 18, 2016 at 10:24:10PM +0200, Eli Zaretskii wrote:
> > Date: Thu, 18 Feb 2016 19:56:30 +0000
> > From: Alan Mackenzie <address@hidden>
> > 
> > I propose moving much of Follow Mode's mechanism into our C code, in
> > particular, into window.c and xdisp.c.

> IMO, moving the code to C will solve only the marginal aspects of
> this.

It would certainly help with the speed, and likely help get a uniform
mode line.

> The main problem -- the fact that the current display engine doesn't
> support windows of unequal width -- cannot be solved without deep
> changes.  We need to at least design these changes first, so that we
> have a clear idea how to solve these issues.  FWIW, I thought about
> this for a while, and didn't see any easy way of doing it.

The display engine currently works on each window as an independent
entity.  It needs to understand "window groups".  Several things it now
does on windows (scrolling, moving point, ...) will need to be extended
to work on window groups.

Where and why do you see the need for deep changes?

> If we abandon the design goal of supporting windows of unequal width,
> the problem becomes much easier.

Yes, but that's not realistic, I think.  Follow Mode windows _are_ of
unequal width.

> I suggest to talk about these main issues first, and only move further
> with any kind of implementation once we've resolved this.  The
> decision of what to keep in Lisp and what to move to C is also
> meaningful only after resolving these main issues.

Again, could you list the issues in somewhat more detail, please?  A
trouble with projects like this one is that they can hover unendlessly
at a very high level of abstraction, too high for much progress to be
made.  This is why I sketched out in some detail an approach to getting
things done.

-- 
Alan Mackenzie (Nuremberg, Germany).