buffer-local variables and state information

buffer-local variables and state information

[Le Wang]

Is it considered generally acceptable to store state information, for
example, from a minor-mode in a buffer-local variable?  This seemed
like a clean way of doing it, because when the buffer gets killed, the
variables go away, and the GC will clean up at some later stage.

However, recently, I discovered that changing major-modes would
actually kill all buffer-local variables, which would leave my
minor-mode in an invalid state.  So I've been doing it wrong?

-- 
Le

Re: buffer-local variables and state information

[Štěpán Němec]

On Sun, 11 Sep 2011 18:25:26 +0200
Le Wang wrote:

> Is it considered generally acceptable to store state information, for
> example, from a minor-mode in a buffer-local variable?

Yes.

> However, recently, I discovered that changing major-modes would
> actually kill all buffer-local variables, which would leave my
> minor-mode in an invalid state.  So I've been doing it wrong?

Not necessarily.

If the variable in question should persist across major mode changes,
you can set its `permanent-local' property, e.g.

  (put 'variable 'permanent-local t)

That will make it exempt from the buffer-local variable slaughter.

-- 
Štěpán