bug#12406: 24.2.50; frame parameter `menu-bar-lines' and `menu-bar-mode'

[martin rudalics]

>> IMHO it should update a frame iff that frame has no `menu-bar-lines'
>> frame parameter.'
>
> Why?  Why shouldn't a user be ABLE to turn on/off showing the menu bar in all
> existing frames?

Because this way we'd have a consistent interface: The presence of a
frame parameter would signal "leave this frame alone".

> One way or the other, we should find ways for users to alternatively easily do
> that (affecting all existing frames) OR protect some frames from that 
toggling.

Do you have a practical use case where my proposal harms?

martin