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[Bug 20525] MIDIAccess methods aren't restricted to instances created by requestMIDIAccess

From: <bugzilla@jessica.w3.org>
Date: Thu, 27 Dec 2012 17:53:45 +0000
To: public-audio@w3.org
Message-ID: <bug-20525-5429-j5oIXBvAmE@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=20525

Jussi Kalliokoski <jussi.kalliokoski@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Jussi Kalliokoski <jussi.kalliokoski@gmail.com> ---
(In reply to comment #3)
> (In reply to comment #2)
> > The object on the global scope is a different object :) This is where WebIDL
> > gets funky. That's called the "interface object" and it does not expose the
> > methods. 
> > 
> > See: 
> > http://www.w3.org/TR/WebIDL/#es-interfaces 
> > 
> > (yes, it's freeken complicated and I've been trying to grok that for about a
> > year) 
> > 
> > you basically end up with this:
> > //This one holds constants and statics
> > var interfaceObject=  function MidiAccess(){
> >   if(this instanceof MidiAccess){
> >      var msg="DOM object constructor cannot be called as a function."   
> >      throw new TypeError(msg);
> >   }
> > }
> > //This one makes actual instances
> > var interfacePrototypeObj = function MIDIAccess(){}   
> > window.MIDIAccess = interfaceObject; 
> > 
> > 
> > You can confirm this in the browser by querying any object. For example: 
> > 
> > >> Event
> > function Event() { [native code] }
> > >>Event()
> > TypeError: DOM object constructor cannot be called as a function.
> > 
> > Note that Event does not expose preventDefault() or any other instance
> > method. Only the constants are exposed.  
> 
> Event doesn't, but Event.prototype does:
> 
> typeof Event.prototype.preventDefault === 'function' // true

But actually, yeah, WebIDL prevents calling the interface methods with a
non-platform-object "this" value, so I'll revert this.

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Received on Thursday, 27 December 2012 17:53:47 UTC

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