[whatwg] Fullscreen Update

[João Eiras]

>>> 2) Chris brought forward the case of nesting. You have a fullscreen
>>> presentation (lets assume API-based activated for now) and in that
>>> presentation there's some video that the presenter wants to display
>>> fullscreen (lets assume the video player is a custom widget with  
>>> API-based
>>> fullscreen activation for now). Once the presenter exits displaying the
>>> video fullscreen, the presentation should still be fullscreen.
>>>
>>> Initially this was brought up with the video being hosted in a separate
>>> descendant document, but the video could be in the same document as  
>>> well.
>>> roc suggested a model that works when you have separate documents and  
>>> it
>>> could be made to work for the single document case too, as long as the  
>>> level
>>> of nesting remains is no larger than required for the presentation  
>>> scenario
>>> mentioned above.
>>>
>>> Is that an acceptable limitation? Alternatively we could postpone the
>>> nested fullscreen scenario for now (i.e. make requestFullscreen fail if
>>> already fullscreen).
>>>
>>
>> +1 for punting on the nested case.
>
>
> I think you'd ever only want to have one thing fullscreen at a time.  
> Thus, if you go from a fullscreen to another, the previous one should  
> naturally leave fullscreen. I think that's how presentation  
> functionality works on ppt and similar tools, too.
>
> Silvia.

I can see the use case when Document is fullscreen, and then an element is  
fullscreened.

So if another element goes fullscreen it replaces the previous, if any,  
but the document keeps its state.

Another alternative would be to have a stack, but I think that's overkill.