Re: [O] Enriched/Org is a colorful Org

[Sebastien Vauban]

Hi Carsten,

Carsten Dominik wrote:
> On 10.4.2013, at 18:21, Eli Zaretskii <address@hidden> wrote:
>>> From: Carsten Dominik <address@hidden>
>>> On 10 apr. 2013, at 11:54, Suvayu Ali <address@hidden> wrote:
>>>> This request is common enough; every time it comes up overlays are
>>>> proposed as a solution.  It would be good if this is available even as a
>>>> library outside of Org.
>>> 
>>> Yes, overlays are better.
>> 
>> I beg the Org developers to please be very careful when introducing
>> expensive display features such as overlays into Org.  Org already
>> puts the Emacs display engine to its limits in many of its popular
>> features;
>
> this is interesting input, I was not aware of this. Has this been discussed
> before, can you point me to relevant threads, and what are the symptoms of the
> display engine being at its limits?
>
>> adding overlays to this mess might be too much.

I guess Eli simply means, in a general way, that overlays do negatively impact
display performance, as you said as well a couple of times:

  ╭────
  │ From: Carsten Dominik <address@hidden>
  │ Subject: Re: performance problems with drawers
  │ Newsgroups: gmane.emacs.orgmode
  │ To: Al <address@hidden>
  │ Cc: address@hidden
  │ Date: Wed, 8 Jul 2009 07:05:53 +0200 (3 years, 39 weeks, 3 days ago)
  │ 
  │ Hi Al,
  │ 
  │ first of all, I cannot reproduce the fact that drawers have such
  │ a major influence on time, wit a test file that I created to
  │ be similar to what you describe.
  │ 
  │ There is a way to speed up drawer handling, by using text properties
  │ instead of overlays.  How have some vague plans to do this, but nothing
  │ concrete or soon.
  │ 
  │ - Carsten
  ╰────

and

  ╭────
  │ From: Carsten Dominik <address@hidden>
  │ Subject: Re: fontification and icon issues
  │ Newsgroups: gmane.emacs.orgmode
  │ To: David O'Toole <address@hidden>
  │ Cc: address@hidden
  │ Date: Thu, 24 Sep 2009 10:46:24 +0100 (3 years, 28 weeks, 2 days ago)
  │ 
  │ On Sep 22, 2009, at 4:11 PM, David O'Toole wrote:
  │ > [...]
  │ >
  │ > 2. using add-text-properties to specify a display property (or even just
  │ > a face) for any part of an org headline text kills the fontification of
  │ > the rest of the text (TODO keyword and leading stars unaffected.) I'm
  │ > trying to use font-lock-add-keywords to display the images.
  │ 
  │ Can you make an example file, and maybe a small function that does set these
  │ properties, so that I can see what you mean?
  │ 
  │ - Carsten
  │ 
  │ > Maybe I should use overlays instead?
  │ 
  │ This can be done, but if every line in a very large file gets
  │ an overlay, performance is severely degraded.
  │ 
  │ - Carsten
  ╰────

>> I don't know enough about Org to understand why overlays are being
>> considered instead of text properties, but feel free to describe the
>> issues (preferably on emacs-devel) and start a discussion about the
>> possible alternatives.

Best regards,
  Seb

-- 
Sebastien Vauban