[whatwg] IDL attribute reflecting enumerated attributes not limited to only know values

Mounir Lamouri mounir.lamouri at gmail.com
Tue Jun 8 07:26:17 PDT 2010


According to the HTML5 specification, an IDL attribute reflecting an
enumerated attribute will have the default reflecting behavior (ie.
return the content attribute on getting and setting it on setting)
except if the attribute is "limited to only known values" [1]. There are
three attributes limited to only known values in the current state of
the specs: @dir, @shape (area element) and @keytype (keygen element).

In other words, that means if @toto is an enumerated attribute with
"foo" and "bar" states/keywords and "foo" as a default missing value, if
@toto is set to "foobar", .toto will return "foobar". To have .toto
returning "foo", the attribute has to be limited to only known value.
Having .toto returning "foo" in this situation seems to be what we
should expect because the content attribute is already accessible with

An example where this behavior seems buggy:
- input.type and button.type: every browser makes it return "text" if
@type isn't set to a known value. If we follow the specifications, .type
should return the current value of @type.

Examples where having another behavior would help:
- method, formmethod, enctype and formenctype have a list of
keywords/states with a default missing value. It would be great to have
the IDL attribute returning the current state instead of the content.
So, scripts wouldn't have to look at the content, checking for values
they know and falling-back to the default value to know the current state.
- input.autocomplete: at the moment, it is returning the content but it
could return the resulting autocompletion state which is maybe a bit
more than just being limited to only known values but still in the same

Maybe, instead of having some attributes "limited to only known values"
we could have some attributes "not limited to only known values", thus
inverting the default reflecting behavior for enumerated attriutes ?

[1] http://dev.w3.org/html5/spec/Overview.html#limited-to-only-known-values


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