W3C home > Mailing lists > Public > www-style@w3.org > March 2004

Re: Useragent Rules in CSS

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Wed, 31 Mar 2004 08:44:11 -0600
Message-ID: <406AD93B.1050904@mit.edu>
To: Ian Hickson <ian@hixie.ch>
Cc: www-style@w3.org

Ian Hickson wrote:
>>Especially when the recommendations keep mutating
>
> You say this as if the working group changes things on a whim.

No, I just say this as a fact.  Quite a few non-compliance issues in 
modern browsers are the result of having been compliant at some point 
and then the specification changing.  This includes some IE/Windows 
"bugs", as Tantek pointed out, as well as several Mozilla issues.  My 
post was in response to a particularly nasty post that was claiming that 
UA authors are purposefully shipping software with buggy implementations 
of properties instead of just not parsing the properties they know they 
have bugs in.  The point is that in some cases when they implemented 
that property they did NOT in fact have a bug in it.

I realize that most of the changes that were made were in fact resolving 
serious consistency issues and that there is even good reasoning behind 
the "out of touch with reality" changes, but that doesn't change the 
fact that if "reality" and a particular UA don't agree that UA suddenly 
becomes non-compliant.

> What exactly is it you think "keeps" mutating? What features have you
> implemented in a fully spec-compliant way before seeing the group make it
> non-compliant, requiring the old implementation to be scrapped?

Me personally?  None, I think.  I've had to do or witnessed some of the 
scrapping, though.  Some things that come to mind immediately are:

1) the status of '_' in identifiers (no scrapping here, really, it was
    not a huge change).
2) the parsing of background-position (this _did_ have to be pretty much
    scrapped, since the hard part was the error-checking logic).
3) the cascade level at which presentational hints live in XML (making
    all sorts of UAs non-compliant at a go).
4) Handling of "inherit" (this totally changed).
5) The treatment of inset and outset in the collapsed border model (this
    is not noted in the http://www.w3.org/TR/CSS21/changes.html document,
    by the way; it probably should be).

There were a few more but I can't recall them right now.

-Boris
Received on Wednesday, 31 March 2004 09:46:14 GMT

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