5814 2008-06-27 08:34:38 +0000 WebIDL: Resolve the callback issue 2010-10-04 13:59:46 +0000 1 1 1 Unclassified HTML WG pre-LC1 HTML5 spec (editor: Ian Hickson) unspecified All All VERIFIED FIXED NoReply P4 normal --- 1 ian ian cam mike public-html-admin public-html-wg-issue-tracking public-html-bugzilla oldest_to_newest 20955 0 ian 2008-06-27 08:34:38 +0000 Right now callbacks are defined in terms of heavy interfaces first, and then turned into functions for JS. We should make the function form primary, and make the interface get generated from rules in WebIDL for those languages that need it. We need some sort of syntax in WebIDL to define callbacks, including the signature of the callback. 21185 1 ian 2008-07-15 11:11:56 +0000 also make sure TimeoutHandler can be handled by this mechanism 22527 2 cam 2008-11-24 23:58:20 +0000 (In reply to comment #0) > Right now callbacks are defined in terms of heavy interfaces first, and then > turned into functions for JS. We should make the function form primary, and > make the interface get generated from rules in WebIDL for those languages that > need it. Why? Not all languages support freestanding functions, but languages that Web IDL can target are already required to support interfaces in some form. It makes sense to me to have the interface be the primary means of specifying callbacks. If there were Web IDL syntax to specify the handler function outside of an interface, there would still need to be something to give the name of the interface (and operation name) for non-ECMAScript language bindings, so you may as well just use the interface syntax. > We need some sort of syntax in WebIDL to define callbacks, including the > signature of the callback. What you can do now is: [Callback, NoInterfaceObject] interface MyHandler { void handleEvent(in DOMString something); }; If you specifically want to disallow { handleEvent: function() ... } from being a callback, you can use [Callback=FunctionOnly]. I was considering removing the FunctionOnly (and PropertyOnly) arguments to [Callback] so that callbacks can be implemented in script uniformly, though. (In reply to comment #1) > also make sure TimeoutHandler can be handled by this mechanism [Callback=FunctionOnly, NoInterfaceObject] interface TimeoutHandler { void handleEvent([Variadic] in any args); }; That would handle the current behaviour of most browsers not treating the object's handleEvent property as the implementation of the callback. I think it would be good if implementations did allow this, though, for consistency. 22528 3 ian 2008-11-25 00:03:04 +0000 I guess I can live with that, but it still seems heavy-duty to me. I'd prefer something like: callback TimeoutHandler ([Variadic] in any args); ...at the top level, i.e. introducing a new type, followed by just using it as if it was a defined type. I don't mind it being turned into an interface for languages that have no function types, but it is first and foremost a callback, not an interface, IMHO. The { handleEvent: function() ... } thing seems like an accident to me, not something we should encourage. 22529 4 cam 2008-11-25 00:23:42 +0000 (In reply to comment #3) > I guess I can live with that, but it still seems heavy-duty to me. It's really only heavy duty in the sense that it takes a few more characters to type. > I'd prefer something like: > > callback TimeoutHandler ([Variadic] in any args); > > ...at the top level, i.e. introducing a new type, followed by just using it as > if it was a defined type. I've been reluctant so far to introduce features that are syntactically incompatible with OMG IDL. > I don't mind it being turned into an interface for languages that have no > function types, but it is first and foremost a callback, not an interface, > IMHO. It's an interface that user code needs to implement to be called back, no? :) > The { handleEvent: function() ... } thing seems like an accident to me, not > something we should encourage. But that is how DataGridProvider is expected to be implemented. I'd prefer that regardless of the number of operations on a callback interface it be implementable using properties, for consistency. 22530 5 ian 2008-11-25 01:10:39 +0000 DataGridProvider isn't a callback, so... :-) Anyway, I can live with the current syntax. 32965 6 mjs 2010-03-14 13:14:43 +0000 This bug predates the HTML Working Group Decision Policy. If you are satisfied with the resolution of this bug, please change the state of this bug to CLOSED. If you have additional information and would like the editor to reconsider, please reopen this bug. 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