20525 2012-12-27 17:12:25 +0000 MIDIAccess methods aren't restricted to instances created by requestMIDIAccess 2013-01-18 15:47:39 +0000 1 1 1 Unclassified AudioWG MIDI API unspecified PC Linux CLOSED INVALID P2 normal TBD 1 jussi.kalliokoski jussi.kalliokoski olivier.thereaux w3c public-audio oldest_to_newest 80639 0 jussi.kalliokoski 2012-12-27 17:12:25 +0000 The current IDL exposes the MIDIAccess interface as a global, but doesn't prohibit calling those methods on objects that aren't MIDIAccess instances created by navigator.requestMIDIAccess(). 80640 1 jussi.kalliokoski 2012-12-27 17:26:28 +0000 Fixed: https://github.com/WebAudio/web-midi-api/commit/16d1d6d61472081cad26282cbd44fd8dccc818e6 80641 2 w3c 2012-12-27 17:38:21 +0000 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. Please revert the changes. 80642 3 jussi.kalliokoski 2012-12-27 17:46:43 +0000 (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 80643 4 jussi.kalliokoski 2012-12-27 17:53:45 +0000 (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. 81562 5 olivier.thereaux 2013-01-18 15:47:39 +0000 Closing.