- From: Jan-Ivar Bruaroey <jib@mozilla.com>
- Date: Thu, 05 Dec 2013 23:30:48 -0500
- To: cowwoc <cowwoc@bbs.darktech.org>, public-media-capture@w3.org
On 11/28/13 12:37 PM, cowwoc wrote: > On 28/11/2013 2:51 AM, bugzilla@jessica.w3.org wrote: >> https://www.w3.org/Bugs/Public/show_bug.cgi?id=23933 >> >> Stefan Hakansson LK <stefan.lk.hakansson@ericsson.com> changed: >> >> What |Removed |Added >> ---------------------------------------------------------------------------- >> >> Summary|Change constraints to use |Proposal: Change >> |WebIDL dictionaries |constraints to use >> WebIDL >> | |dictionaries >> >> --- Comment #2 from Stefan Hakansson LK >> <stefan.lk.hakansson@ericsson.com> --- >> (In reply to Gili from comment #1) >>> Just to be clear: the implication of this proposal is that users >>> will need >>> to ask for a set of constraints, but then they will have to check >>> that the >>> returned device meets those constraints (because some of them may >>> have been >>> omitted as "unknown"). >> That is not true really. Since the proposal also includes a method >> that allows >> the app to probe for what constraints that the UA understands, it can >> first >> check, and if one or more constraints the app wants to use as >> mandatory are not >> known by the UA the app can at that stage decide to not go ahead and >> call gUM. >> > > In light of that fact, I don't understand the benefit of ignoring > unknown constraints. If the user has the ability to detect unknown > constraints and *still* insists on passing them into getUserMedia() > shouldn't we fire the error listener? Please understand that Webidl dictionaries ignore unknown keys. From http://heycam.github.io/webidl/#idl-dictionaries : > "A dictionary value of type D can have key–value pairs corresponding > to the dictionary members defined on D and on any of D’s inherited > dictionaries." This is on purpose for future-proofing, and all other web APIs (that use dictionaries at least) are on-board with this. AFAIK it is only our freaky mandatory constraints that fly in the face of this. Our spec is not implementable as it stands, because it speaks about mandatory constraints being dictionaries. Our spec sorely needs review by the webidl experts group. This bug is about fixing our API to use plain webidl dictionaries instead of reinventing webidl. It doesn't take much and we can live with it. With this fix, the error listener will only fire when the browser knows what it is doing and it knows that all cameras are wrong. If I truly want nothing to work unless the browser supports constraint x (like gUM() works today) then I just bail early. No need to involve gUM() at all. If on the other hand, I choose not to bail and I proceed, the new gUM() behavior errs on the side of working, giving me positives, negatives and false positives, instead of just all negatives when constraint x is involved. This has merit, because it avoids sweeping false negatives until browsers catch up. See footgun-relief example: https://bugzilla.mozilla.org/show_bug.cgi?id=927358 > Gili .: Jan-Ivar :.
Received on Friday, 6 December 2013 04:31:16 UTC