Re: Enriched/Org is a colorful Org

[Carsten Dominik <carsten.dominik@gmail.com>]

On 11.4.2013, at 19:30, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Carsten Dominik <carsten.dominik@gmail.com>
>> Date: Thu, 11 Apr 2013 04:58:15 +0200
>> Cc: "emacs-orgmode@gnu.org List" <emacs-orgmode@gnu.org>,
>> Eli Zaretskii <eliz@gnu.org>
>> 
>>> 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:
>> 
>> Yes, but Eli says that Org already severely tests the
>> display engine, and he uses the word "mess", even though
>> we mostly use text properties for faces and other
>> display-related things.
> 
> Well, don't interpret "mess" too literally ;-)

I will add an overlay that displays "mess" as "mix" :D

> 
>> Of course, Org already uses overlays, for example for
>> folding (as does outline.el), and for temporary marking
>> of text like during src block editing.  But as your digging
>> shows, I ave avoided them in the past, and we are also not
>> using them for org-indent.el, for example.
>> 
>> The reason why I said "overlays would be better" is simply
>> that they would allow to add display properties in a
>> persistent way that would not interfere that our
>> font-lock-unfontify-region function removes face and
>> invisibility text properties.  So they are "better" for
>> implementing hand-made faces selection that should overrule
>> font-lock.
> 
> Overlays should be OK as long as they aren't too many, and as long as
> you don't move them around too much, particularly in post-command-hook
> or some such.

This explanation sounds to me as if the display engine is building
some kind of tree of overlays to find properties changes quickly.  Too bad I don't have time to understand this stuff in more detail, it sounds interesting.

- Carsten