Re: Unexpected hiding of identical images

[Richard M. Stallman]

    The problem is that text-properties are not really adapted for such uses.
    After all, they apply to chars, not to text.

They apply to text.  Text is made up of characters.

Perhaps what you mean is that text properties belong to the text
rather than to defined extents in the text.  This is intentional and
necessary; it is the only way to get consistent behavior as text
is killed, copied, and yanked.

    So by convention we consider
    that contiguous properties that are `eq' make up a region/area/extent, which
    works 99%.

Again, it is the only way to get consistent behavior as text is
killed, copied, and yanked.  But you have to know the convention
and arrange to follow it.

    Another alternative is to use overlays.  Except that overlays are not
    duplicable and don't apply to strings.  That's where XEmacs's extents
    make sense.

They only appear to make sense, in that they prevent this
easily-avoided pitfall.  However, it is impossible to make killing and
yanking work correctly with them in general.