Re: `overlay-arrow-position' should be automatically buffer-local

[Kim F. Storm]

Daniel Brockman <address@hidden> writes:

> I believe the variable `overlay-arrow-position' should
> automatically become buffer-local whenever it is set.
>
> It appears that Gnus fails to do this manually, instead
> ending up setting the global value to a marker that refers
> to the Gnus summary buffer, which doesn't make sense.
>
> In fact, I see no reason to ever set the global value of
> this variable.  In any case, it should not be the default.

In principle, there is only one overlay-arrow-position variable,
and since its value is a marker, its value includes the buffer
in which it occurs.

This is how e.g. gdb can easily move the overlay arrow between buffers
-- just modify the global variable.  

If the variable was buffer local, you would have to be sure to clear
out the old buffer-local value whenever the arrow was moved to another
source buffer.

Besides, having buffer-local overlay arrow variables may confuse the
redisplay engine in some obsure cases (or at least it used to do that
-- can't remember if I managed to fix that).

GNU probably doesn't have this problem, so it would be ok to make it
buffer local in the summary buffer.  

In emacs 22, GNU may use its own overlay arrow variable and add it to
the overlay-arrow-variable-list.

-- 
Kim F. Storm <address@hidden> http://www.cua.dk