[whatwg] Specification unclear about how HTMLElement.prototype.onscroll's getter/setter should behave for "body" elements

Ian Hickson ian at hixie.ch
Mon Dec 3 16:33:23 PST 2012

On Mon, 3 Dec 2012, Boris Zbarsky wrote:
> You have IDL like this:
>   interface Foo {
>     attribute EventHandler onscroll;
>   };
>   interface Bar : Foo {
>     attribute EventHandler onscroll;
>   };
> WebIDL already defines how this behaves: there are getters/setters on 
> both Foo.prototype and Bar.prototype, and it's up to the spec prose to 
> decribe how those getters/setters actually behave.  That's really what's 
> missing here, no? Again, there are several possible behaviors; the 
> question is which one we want for this particular case.

I'd really like to have WebIDL define the behaviour rather than HTML, 

Note that onerror has a different type on HTMLElement and HTMLBodyElement.

> > It relatess also to:
> > 
> >     https://www.w3.org/Bugs/Public/show_bug.cgi?id=17201
> It's a similar situation, yes.  But in this case I don't see why you'd 
> need an IDL annotation of any sort at all.  If you want the behavior to 
> be the same, just don't define onscroll on Bar at all and define the one 
> on Foo to special case the two Foo subclasses you care about here.  If 
> you don't want it to be the same, the IDL annotation doesn't help you.

onscroll is a case where there's really no reason to use a different 
setter, agreed. So I've commented that out (and it's similar friends). 
That still leaves onerror though.

On Tue, 4 Dec 2012, Cameron McCormack wrote:
> I agree.  But if we really do need a separate namedItem (for bug 17201) 
> on HTMLPropertiesCollection, then there is no harm in having it too, but 
> I would have it not work on other HTMLCollection objects.

And vice versa.

Per our IRC discussion just now, I think I would propose that when a 
method/setter/getter from a prototype of interface A is called against an 
object that is of an interface B (or one of B's descendants), where B is a 
subclass of A, and B defines its own method/getter/setter with the same 
name, then it should throw.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

More information about the whatwg mailing list