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From: Carsten Dominik <carsten.dominik@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-orgmode@gnu.org
Subject: Re: Enriched/Org is a colorful Org
Date: Fri, 12 Apr 2013 12:56:11 +0200	[thread overview]
Message-ID: <FFA190FA-6F2E-4983-AD4E-7D0F60378AE4@gmail.com> (raw)
In-Reply-To: <83fvyw9mkh.fsf@gnu.org>


On 12 apr. 2013, at 10:31, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Carsten Dominik <carsten.dominik@gmail.com>
>> Date: Fri, 12 Apr 2013 09:13:47 +0200
>> Cc: emacs-orgmode@gnu.org
>> 
>>> Just search xdisp.c for "overlay", you will see the story quite
>>> clearly, I think.
>> 
>> My Sunday pleasure reading project.
> 
> Good luck, and let me know if you need something explained.  The
> commentary at the beginning of the file might serve as an
> introduction, although it doesn't really touch the issue at hand.
> 
>> So the reason that the combination with hi-line is slow is because
>> hl-line is using post-command-hook to move its overlay, and redisplay
>> of a full window with org-mode is slow because so much stuff is
>> hidden and Emacs makes a full re-evaluation of what needs
>> to be displayed?
> 
> Right.  If hi-line (or any similar mode) is off, then at least
> horizontal cursor motion should be fast, because then Emacs knows that
> nothing changed, and finding the place where to put the cursor on the
> same line it was before is relatively easy.
> 
> But even C-n and C-p is quite another story in an Org buffer: Emacs
> needs to determine where that puts point, and doing so generally means
> traversing all of the hidden parts of the buffer between the line
> which was current and the new current line.  In a complex Org buffer,
> that could easily be many thousands of buffer positions.

I guess outline mode does have the exact same problem in this case, in
fact any mode with large amount of hidden text.

> 
> Also, recall that, under line-move-visual, which is nowadays on by
> default,

Not in my setup, but since it the default, yes, this causes more
issues.  Another important point to be aware of.


> Emacs moves by _screen_ lines, not by physical lines.  So a
> simple C-n must internally emulate display to find the next line
> visible on the screen by traversing the buffer one character at a time
> and taking note of each and every text property and overlay in
> between, until it finds the buffer position whose screen coordinates
> are [X,Y+N], where [X,Y] are the coordinates of the previous cursor
> position and N is the line height in pixels.  And this is just to find
> where point will be; then the screen must actually be redisplayed,
> which might mean more work, if the new position of point requires
> scrolling, e.g. if cursor went off the scroll margins or whatever.
> 
> We only get reasonably fast performance with all this complexity
> because our machines are incredibly fast.  But we are many times on
> the edge, as the bug I cited and similar ones show.

Thanks again.

- Carsten

  reply	other threads:[~2013-04-12 10:56 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-10  4:02 Enriched/Org is a colorful Org Jambunathan K
2013-04-10  9:54 ` Suvayu Ali
2013-04-10 10:16   ` Carsten Dominik
2013-04-10 10:39     ` Torsten Wagner
2013-04-10 10:48     ` Suvayu Ali
2013-04-10 10:53       ` Carsten Dominik
2013-04-10 11:20         ` Sebastien Vauban
2013-04-10 11:26           ` Carsten Dominik
2013-04-10 12:15           ` Jambunathan K
2013-04-10 11:57     ` Jambunathan K
2013-04-10 16:21     ` Eli Zaretskii
2013-04-10 16:43       ` Jambunathan K
2013-04-10 17:13         ` Eli Zaretskii
2013-04-10 19:58       ` Carsten Dominik
2013-04-10 20:16         ` Sebastien Vauban
2013-04-11  2:58           ` Carsten Dominik
2013-04-11 17:30             ` Eli Zaretskii
2013-04-11 22:49               ` Carsten Dominik
2013-04-12  6:41                 ` Eli Zaretskii
2013-04-12  7:13                   ` Carsten Dominik
2013-04-12  8:31                     ` Eli Zaretskii
2013-04-12 10:56                       ` Carsten Dominik [this message]
2013-04-12 11:49                         ` Torsten Wagner
2013-04-12 13:03                           ` Eli Zaretskii
2013-04-12 18:00                             ` Suvayu Ali
2013-04-12 18:38                               ` Eli Zaretskii
2013-04-13 10:50                                 ` Suvayu Ali
2013-04-12 12:36                         ` Eli Zaretskii
2013-04-13 12:24                           ` Sean O'Halpin
2013-04-13 14:38                             ` Jambunathan K
2013-04-13 15:01                             ` Eli Zaretskii
2013-04-12  8:35                     ` Bastien
2013-04-12 14:45                       ` François Pinard
2013-04-18 20:37                         ` Samuel Wales
2013-04-11 17:27         ` Eli Zaretskii
2013-04-11 22:46           ` Carsten Dominik
2013-04-10 12:12   ` Jambunathan K

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