W3C home > Mailing lists > Public > www-style@w3.org > November 2012

[selectors] Case-sensitivity of type and attribute selectors

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 28 Nov 2012 16:58:58 -0800
Message-ID: <CAAWBYDD5VVAoVrr-SwpMONEd4eZ8i-ujATuFsPWRHgAShyQQyA@mail.gmail.com>
To: www-style list <www-style@w3.org>
HTML defines that its tagnames and attribute names are
case-insensitive.  The interaction of this with CSS type and attribute
selectors, though, appears to be underdefined (or at least, browsers
do different things).

In particular, it appears that FF's behavior is to do a
case-insensitive comparison if the element is in the HTML namespace,
and case-sensitive otherwise.  (I think IE does the same thing, but am
not sure if it does in all circumstances.)  WebKit just lowercases the
selector, and then does a case-sensitive comparison against the DOM
name.  Opera is always case-insensitive.

WK's behavior is broken in the case of SVG elements, since some of
them have canonical names with uppercase in them.  That means that,
right now, we're completely unable to target mixed-case XML element
names or attributes with selectors.

What should the correct behavior be?  We obviously have to maintain
the HTML case-insensitivity, as there's tons and tons of content
relying on that.  What should we do, though, about SVG elements (and
in general, all non-HTML host languages)?  The choices seem to be:

1. Everything but HTML is case-sensitive.
2. Everything is case-insensitive.
3. Host languages define whether they're case-sensitive (defaulting to
case-sensitive in the absence of any other information).


Received on Thursday, 29 November 2012 00:59:45 UTC

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