Re: Re: Callbacks?

> Date: Thu, 01 Dec 2005 20:35:42 +0900
> From: Martin Duerst <duerst <at> it.aoyama.ac.jp>
> Cc: emacs-bidi <at> gnu.org
> 
> There is definitely a need for some
> code that does the actual reordering, even if the directionality
> can be defined as some text property. Same for colors; there
> needs to be some C code that actually takes the color property
> and produces the color on the screen.

If you are thinking about using text properties to store the
character's directional properties, the ones specified in the Unicode
database, then that sounds like a waste of resources: the Unicode
version of Emacs already reads that database, so why repeating the
data in another data structure?

>  >> Now the interesting possibility presents itself, which is to add
>  >> Unicode-related "special" (ie. built-in) text properties.  In
>  >> particular, directional class.
>  >
>  >Not a good idea: text properties are considered part of the text, so
>  >they are, e.g., copied together with the characters when you
>  >copy/paste text.
> 
> If this is used with a mode, this should not be a problem:
> The mode reanalyzes the pasted text and fixes things up.

That's not how text properties are handled now in Emacs.  It would
slow down Emacs, for one thing.  In any case, this is using text
properties for something they were not designed to do.  (There are