From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel@gnu.org
Subject: Re: The future of Follow Mode - a proposal.
Date: Sat, 20 Feb 2016 12:44:15 +0000 [thread overview]
Message-ID: <20160220124415.GA1758@acm.fritz.box> (raw)
In-Reply-To: <83io1kr12k.fsf@gnu.org>
Hello, Eli.
On Fri, Feb 19, 2016 at 08:45:39PM +0200, Eli Zaretskii wrote:
> > Date: Fri, 19 Feb 2016 18:18:34 +0000
> > Cc: emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>
> > > I already explained this above: "the fact that the current display
> > > engine doesn't support windows of unequal width". If you want to lift
> > > this limitation, the move_it_* family of functions, which simulate
> > > redisplay, and are the workhorse of every decision Emacs makes that
> > > concerns layout, cannot switch windows in their inner loops.
> > I envisage reinitialising the iterator structure as necessary when
> > passing bewteen windows. The change in width would be handled at a
> > relatively high level.
Or, maybe not, se below.
> > The window start position is known, the window end position could be
> > calculated as we progress.
> The functions we talk about currently don't know what they are invoked
> for. Your envisioned changes imply that they should behave
> differently depending on whether the results will be used for layout
> of the current window or the next/previous window in a group. That's
> part of the changes I had in mind. They are not trivial. But without
> them, what you want to do will not work reliably.
How about adding an extra boolean parameter to the move_it_* functions,
perhaps called `physical', which when set would mean the function would
have to adjust its iterator when crossing a window boundary, when not set
would work the same way as it currently does? `vertical-motion' would
also need this extra &optional parameter, possibly a few other defuns,
too.
There are around 150 calls to move_it_*. I'm guessing that most of these
would set `physical' to false, perhaps more of the ones in window.c would
use true.
> > As an example, `compute_window_start_on_continuation_line' would have to
> > use the dimensions of the previous window to determine the window-start.
> > Jiggling the various windows around after text changes or scrolling is
> > going to be the hard part of the coding.
> Yes, and the result will be non-trivial changes in the overall logic,
> because redisplaying a window will no longer be independent of other
> windows.
Yes. This is what is currently implemented in Follow Mode.
> It's all doable, of course, but I suggest taking a good look at the
> use cases for each of these functions, before you design the way they
> should work to support windows of unequal width.
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2016-02-20 12:44 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-18 19:56 The future of Follow Mode - a proposal Alan Mackenzie
2016-02-18 20:24 ` Eli Zaretskii
2016-02-19 14:25 ` Alan Mackenzie
2016-02-19 14:34 ` martin rudalics
2016-02-19 16:12 ` Eli Zaretskii
2016-02-19 16:08 ` Eli Zaretskii
2016-02-19 18:18 ` Alan Mackenzie
2016-02-19 18:45 ` Eli Zaretskii
2016-02-20 12:44 ` Alan Mackenzie [this message]
2016-02-20 13:05 ` Eli Zaretskii
2016-02-23 23:11 ` Alan Mackenzie
2016-02-24 3:57 ` Stefan Monnier
2016-02-24 17:14 ` Eli Zaretskii
2016-02-24 18:57 ` Stefan Monnier
2016-02-24 19:19 ` Eli Zaretskii
2016-02-24 20:10 ` Stefan Monnier
2016-02-24 20:21 ` Eli Zaretskii
2016-02-25 0:30 ` Stefan Monnier
2016-02-25 16:28 ` Eli Zaretskii
2016-02-25 16:46 ` Stefan Monnier
2016-02-25 17:29 ` Eli Zaretskii
2016-02-25 20:30 ` Alan Mackenzie
2016-02-25 20:57 ` Alan Mackenzie
2016-02-25 21:10 ` Stefan Monnier
2016-02-25 22:17 ` Alan Mackenzie
2016-02-28 16:40 ` Stefan Monnier
2016-02-24 18:34 ` Eli Zaretskii
2016-02-25 20:18 ` Alan Mackenzie
2016-02-19 14:56 ` Anders Lindgren
2016-02-19 16:30 ` Eli Zaretskii
2016-02-19 18:45 ` Alan Mackenzie
2016-02-18 20:41 ` John Yates
2016-02-19 16:21 ` Alan Mackenzie
2016-02-19 16:32 ` Eli Zaretskii
2016-02-19 19:25 ` John Yates
2016-02-19 20:27 ` Eli Zaretskii
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