Re: Should overlays evaporate by default?

[Richard Stallman]

    Perhaps it would be better for overlays to evaporate by default.

I tend to agree this would make things better in most cases, and only
be wrong in a few.  However, it is an incompatible change, and in some
places it WILL break code.

It occur to me that we could make it easier to find those places.
Suppose that by default the `evaporate' property is set to `display-warning'.
Suppose that in this case, when the overlay becomes empty, it evaporates
and displays a warning using `display-warning'.

On seeing the warningm programmers would adapt their programs to set
`evaporate' either to t or nil and thus prevent the warning.

In Emacs 23, we could change the default to t.