bug#754: Can't cancel dabbrev-expand (M-/) with C-g

[David Caldwell <david@porkrind.org>]

David Caldwell wrote:
> Chong Yidong wrote:
>>> If I have many buffers open (284 at the moment) and if I run
>>> dabbrev-expand (M-/) to expand the word under my buffers then it
>>> searches through every buffer and takes an understandably long
>>> time. If I mispelled the word fragment then it never has a hope of
>>> finding it and I'd like to cancel the operation. But C-g does not work
>>> for some reason and so I have to wait a good 5 to 10 seconds for it to
>>> finish scanning all my buffers. This gets very frustrating after the
>>> third or fourth time.
>>
>> I don't see why C-g wouldn't work here.

After further testing, I believe this is not really a bug in dabbrev.
C-g *does* cancel the operation, it's just that sometimes there is a
large lag before it cancels (though in my current tests I've never had
it go beyond 2 seconds). I have a ton of buffers open right this moment
and fulling scan them takes 15 to 20 seconds, so I can definitely tell
that it's canceling.

The 1 to 2 second lag is still a little frustrating, but it's much
better than the originally reported 5 to 10 second lag. I wonder if it
has to do with how the Mac handles the quit signal in windowed mode...

-David