Re: Converting compositions to strings

[Eli Zaretskii <eliz@gnu.org>]

> From: Clément Pit-Claudel <cpitclaudel@gmail.com>
> Date: Mon, 30 Jan 2017 00:13:34 -0500
> 
> Many compositions can be represented as strings: for example, prettify-symbols-mode composes "lambda" into "λ", and nameless prettifies the name of the current package as ":" or "::".
> 
> How can I reconstruct these strings from the value of the 'composition' text property?  Small experiments suggest that for single-character compositions the property has the shape (_ _ [?λ]) and for multi-character compositions (_ _ [?x _ ?y _ …]), but I also found instances of the shape ((_ ?x _ _)), and ((_ . ?x)) (I think).

The information about this can be found in the doc strong of
compose-region, under COMPONENTS.

> Is there a recipe that I can use to construct a string representation of a composition? (I realize that many compositions can't adequately be represented as plain strings; I'm only interested in those that can).

I don't really understand what you mean by "string representation of a
composition".  In general, a composition doesn't represent a string,
and even those that are represented by characters or strings in the
property are many times something other than a string.  The ones that
seem to be relevant to what you are looking for (I'm guessing) are a
small class, and I don't think you can discern them from the others
unless you look at the "rules" parts of a composition.