Re: No-change proposals for WebIDL for constraints

I'd like to propose one change for your consideration:

In the "optional" array, we should be able to specify multiple 
constraints per entry.

For example:

optional:
[
   [ {"width": 1920, "height": 720} ],
   [ {"width": 1600, "height": 900} ],
]

as opposed to:

optional:
[
   {"width": 1920},
   {"height": 720},
   {"width": 1600},
   {"height": 900}
]

Gili

On 16/12/2013 12:43 PM, Harald Alvestrand wrote:
> I think we're landing on the basic structure of constraints as 
> retaining the properties it has:
>
> - Mandatory is a set of key/value pairs, where all of them need to be 
> satisfied in order for the allocation to succeed. If the browser does 
> not understand a key, it does not succeed. (I know Jan-Ivar doesn't 
> agree.)
>
> - Optional is a sequence of sets of key/value pairs. (I'm suggesting 
> that we relax the rule of only one key/value pair for each element in 
> the sequence). The browser will try to satisfy as many constraint sets 
> as it can, but will ignore constraint sets that cannot be satisified, 
> these will not cause the call to fail.
>
> The Mandatory set of key/value pairs doesn't have the same semantics 
> as Dictionary. Therefore it is not a Dictionary.
>
> Existing deployed code is expecting this code to be correctly parsed:
>
> getUserMedia(.... { mandatory: { a=b}, optional: [ {c=d} ]})
>
> It would be nice to keep that representation parsing.
>
> The following suggestions are all valid IDL for the Constraints 
> construct in section 10.1.4.4 of the current getusermedia spec (which 
> is currently incomplete):
>
> dictionary Constraints {
>    ConstraintSet? mandatory;
>    sequence<ConstraintSet> _optional;
> };
>
> Alternative 1:
>
> ConstraintSet = object. This will Just Work, with the usual caveats 
> about generated code needing to deal with Object.
>
> Alternative 2:
>
> [MapClass(DOMString, Constraint)] interface ConstraintSet {
>    ... boilerplate may go here ...
> }
>
> Alternative 3:
>
> [Constructor that takes an Object prototype]
> interface ConstraintSet {
>    get Constraint(DOMString)
>    set(DOMString, Constraint)
> }
>
>
> These may or may not parse the constant notation mentioned earlier. I 
> can't read the IDL spec to affirm or deny that.
>
> Constraint can be a Dictionary. No property of Dictionary was harmed 
> in this writing.
> But I think Jan-Ivar's proposal for "valid IDL" may work better at 
> this level.
>
> http://lists.w3.org/Archives/Public/public-media-capture/2013Nov/0084.html
>
>
>
>
>