bug#10348: 24.0.92; Save and load window states

[Stefan Monnier <monnier@IRO.UMontreal.CA>]

>> And of course the parameters preserved intra-session is a superset of
>> the parameters preserved inter-sessions.
> I'm not so sure.  Maybe a parameter is useful intra-session but not
> readable from disk.

I don't understand: you first seem to say you disagree with me, but then
what you say afterwards seems to agree with me.

>> Using window-state-ignored-parameters to specify the difference between
>> the two sets seems OK.
> You mean that any value present in `window-state-ignored-parameters'
> would have to be a member of the `window-persistent-parameters' I used
> in my patch?

Not necessarily, but an element in window-state-ignored-parameters which
is not in window-persistent-parameters would have no effect.

> I'd rather not care about `window-state-ignored-parameters' in
> `current-window-configuration' or `set-window-configuration'.

That's OK, window-configurations are intra-session objects anyway, so if
window-state-ignored-parameters specifies the difference between the two
sets, it indeed can be ignored by  `current-window-configuration' and
`set-window-configuration'.

> (BTW, I use `window-persistent-parameters' instead of
> `window-state-saved-parameters' because they apply to both,
> `current-window-configuration` and `window-state-get'.)

Yes, the name sounds fine.

>> An alternative would be to ignore window-state-saved-parameters (and
>> window-state-ignored-parameters)
> So far, I didn't care about `window-state-ignored-parameters' when
> restoring a state in `window-state-put'.

Fine.

>> upon restore.  Instead, we'd save the parameters in a list where each
>> element is either (PARM . VAL) or just PARM where the second form
>> indicates that PARM was not set and should hence be unset upon restore.
> Fine with me.  Obviously, this makes saved states a bit larger.

Indeed, but otherwise, as you pointed out, it makes the semantics rather
tricky if window-persistent-parameters is changed between the save and
the restore (which is something that is very likely to happen sometimes
since the restore may happen years after the save).


        Stefan