next-single-char-property-change on xemacs vs emacs

[David Kastrup]

Marcus Harnisch <marcus.harnisch at xemacs.org> writes:

> Raymond Toy <toy.raymond at gmail.com> writes:
>
>> When there is no next-single-char-property-change, XEmacs returns nil.
>> But Emacs (according the docstring) returns the end of the object.
>
> Not sure if I fully understood the mechanics behind extents and
> text-properties, but wouldn't it make sense to be able to tell the
> difference between a text-property whose proper end-position happens to
> be the end of an object, and a text-property that was cut off? In a
> narrowed region for instance?

Well, the Emacs equivalents are different here: text properties are
(surprise, surprise) properties of the individual characters, not of the
enclosing object.  So this "difference" between "end-position" and "cut
off" does not make sense here.  In contrast, overlays are properties of
the enclosing object (supported only for buffers and, in some limited
sense, windows).

There is some limited approximation of that "difference" available by
looking at the question "would inserting a character here inherit the
text properties from the preceding character?".

But it is an approximation.

-- 
David Kastrup