1002256 - Implement CompositionEvent() constructor

Status: RESOLVED FIXED

(Core :: DOM: Events, defect)

Description

[Arkadiusz Michalski (Spirit)]

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:28.0) Gecko/20100101 Firefox/28.0 (Beta/Release)
Build ID: 20140314220517

Steps to reproduce:

At now document.createEvent("CompositionEvent") and CompositionEvent.initCompositionEvent() working properly, but for some reason still missing CompositionEvent() constructor. Only Chrome support it (of course with lack some properties).

Comment 1

[Rick Byers]

Strange, CompositionEvent appears to have a constructor but it doesn't work (on Firefox 38 for Linux):

> CompositionEvent
function augmentEventConstructor/global[constructorName](type, initDict)
> CompositionEvent.length
2
> new CompositionEvent("compositionStart")
TypeError: Illegal constructor.
>new CompositionEvent("compositionStart", {})
TypeError: Illegal constructor.

I don't see any way to feature detect for this behavior.  It's causing a problem for me in my InputDevice polyfill: https://github.com/RByers/InputDevice/issues/10.

Comment 2

[Olli Pettay [:smaug][[e-mail]]]

CompositionEvent doesn't have a constructor.
http://mxr.mozilla.org/mozilla-central/source/dom/webidl/CompositionEvent.webidl

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Hmm, we have .locale in CompositionEvent, but the spec doesn't. Yet the spec has .locale
as a param for initCompositionEvent. 
And looks like https://dvcs.w3.org/hg/d4e/raw-file/tip/source_respec.htm has .locale for 
KeyboardEvent.

Ok, the specs are in totally unreadable and unimplementable state, so I'll just add support for
locale also in Constructor case.

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

No, the spec is in such a mess state now that I don't dare to implement anything.

Comment 5

[Rick Byers]

Would it make sense to fix CompositionEvent so that clients can tell there is no real constructor?  Eg. I'd expect CompositionEvent.length to be 0, not 2.  In IE 'typeof CompositionEvent == "object"' since they don't support event constructors at all.

Comment 6

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

(In reply to Olli Pettay [:smaug] from comment #3)
> Hmm, we have .locale in CompositionEvent, but the spec doesn't. Yet the spec
> has .locale
> as a param for initCompositionEvent. 
> And looks like https://dvcs.w3.org/hg/d4e/raw-file/tip/source_respec.htm has
> .locale for 
> KeyboardEvent.

.locale has some issues:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=21830
https://lists.w3.org/Archives/Public/www-dom/2013OctDec/0051.html

So, I'm not sure if it will be standardized. Some people of Google really want it, though.

Comment 7

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

Failing test: http://w3c-test.org/dom/events/Event-subclasses-constructors.html

Chrome, Edge, and Safari 7.1 all pass the CompositionEvent tests there.  Edge has a .locale property, but seems not to support it in the constructor.  Chrome has no .locale at all.  Spec bug: https://github.com/w3c/uievents/issues/48

I don't think the .locale situation needs to block implementing the constructor -- we can just leave out .locale for now and follow the spec (which seems to be what Edge did).  If we later decide to standardize .locale, we can add it to the constructor later.

(In reply to Rick Byers from comment #5)
> Would it make sense to fix CompositionEvent so that clients can tell there
> is no real constructor?  Eg. I'd expect CompositionEvent.length to be 0, not
> 2.

I get 0 here, FWIW.  If you wanted to feature-test without that, you could try calling it and see if it throws.

Comment 8

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

Attachment: Bug 1002256 - Support CompositionEvent constructor;

All other browsers support a constructor here.  Per current spec, the
constructor does not support .locale, although initCompositionEvent
does.  If we ever decide to standardize .locale, the constructor can be
updated at that point.  (Edge also supports .locale in
initCompositionEvent but not the constructor.  Chrome doesn't support
.locale at all.)

Review commit: https://reviewboard.mozilla.org/r/89816/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/89816/

Comment 9

[Ben Kelly [:bkelly, not reviewing]]

Comment on attachment 8806358 [details] [diff] [review]
Bug 1002256 - Support CompositionEvent constructor;

https://reviewboard.mozilla.org/r/89816/#review90456

Looks reasonable.  r=me

::: dom/webidl/CompositionEvent.webidl:6
(Diff revision 1)
>  /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
>  /* This Source Code Form is subject to the terms of the Mozilla Public
>   * License, v. 2.0. If a copy of the MPL was not distributed with this file,
>   * You can obtain one at http://mozilla.org/MPL/2.0/.
>   *
>   * http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html#events-CompositionEvent

Please update the spec link to:

https://w3c.github.io/uievents/#interface-compositionevent

::: dom/webidl/CompositionEvent.webidl:16
(Diff revision 1)
>  
> +[Constructor(DOMString type, optional CompositionEventInit eventInitDict)]
>  interface CompositionEvent : UIEvent
>  {
>    readonly attribute DOMString? data;
>    readonly attribute DOMString  locale;

While you are here, can you add a comment that this is a non-standard extension at the moment?

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/6626c876b087
Support CompositionEvent constructor; r=bkelly

Comment 11

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/6626c876b087

Comment 12

[Chris Mills [:cmills]]

I have created a reference page for the constructor:

https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent/CompositionEvent

I've also updated/created pages for the other parts of the API, as the MDN docs were rather old and clunky. Here:

https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent
https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent/data
https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent/locale
https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent/initCompositionEvent

Finally, I've added a not about this to the Fx53 release notes:

https://developer.mozilla.org/en-US/Firefox/Releases/53#DOM_HTML_DOM

Let me know if any of this looks wrong and needs updating. Also, Could anyone provide me with a simple code example showing how you'd actually use this? I've not filled in any examples, as I'm not familiar with this API.

Comment 13

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

Unfortunately, I can't help you, because I have no idea what this API even does.  I was just fixing some failing tests.