bug#10348: 24.0.92; Save and load window states

[martin rudalics]

> I must be missing something: set-window-parameter does "modify a window
> parameter's value destructively".
>
>>> so it makes the semantics rather irregular.
>> It's precisely the same as for the dedicated status of a window.
>
> Is it?
> The irregularity I'm referring to, is that set-window-configuration will
> remove parameters that were added since the save, but will not undo the
> changes to the parameters that were modified since the save.

You're right.  This makes window parameters useless for applications
where a window excursion can temporarily store some other value for that
parameter.  In particular, side windows can be broken very easily.

So we'd either have to copy the parameter list when creating a window
configuration, not use `setcdr' in `set-window-parameter', or make a new
slot for parameters that must not be modified destructively.  Neither
solution seems attractive to me.

martin