bug#10222: 24.0.92; Sentence movement commands make emacs hang

[Tassilo Horn <tassilo@member.fsf.org>]

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>>       (overlay-put ol 'invisible t)
>>       (overlay-put ol 'intangible t))))
>
> While we probably can and maybe should make your test case work
> better, the use of `intangible' is strongly discouraged,

Then it would be good if the docs stated that.

> specifically because it's pretty much impossible to make all other
> commands work "right" in the presence of intangible properties.

Yes, probably.  I've experimented a bit more, and it gets even worse
with line-editing commands like kill-line, especially if the intangible
overlay starts or ends in the middle of a line...

But it seems that there's no sense in making an invisible overlay
intangible, anyway, at least I can't find any difference in behavior
between invisible and invisible + intangible (except that the problem
doesn't appear).

The mode that creates those overlays (iedit-mode) seems to do that in
order to protect the invisible regions, but you can still accidentally
kill an intangible & invisible region as a whole.  `read-only' would be
the right property to use here, but it seems it's not supported for
overlays...

Bye,
Tassilo