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[css3-conditional] Where () are ok inside @supports?

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 9 Aug 2011 17:28:51 -0700
To: www-style@w3.org
Cc: Vitor Menezes <vmenezes@mozilla.com>
Message-ID: <20110810002851.GA16052@pickering.dbaron.org>
I asked Vitor Menezes, an intern this summer at Mozilla, to work on
implementing @supports (as @-moz-supports).  He pointed out the
following problem with the grammar: The grammar currently *attempts*
to avoid allowing nesting extra sets of parentheses, e.g., to allow
  @supports (display:block) and (display:inline)
but disallow:
  @supports (display:block) and ((display:inline))
but it fails to do that in one case, which is that it allows double
(but not more) parentheses around the argument to "not".

On reflection, I think forbidding doubling of parentheses is a bad
idea because it makes it harder for people to test things by
commenting them out.  In other words, since an author may want to
experiment with:
  @supports not ((display:block) and (display:inline))
by changing it to:
  @supports not ((display:block) /*and (display:inline)*/)
it should be legal to write:
  @supports not ((display:block))

Now, the one other thing I'm reconsidering is my idea of forbidding
the declaration not being in parentheses.  In other words, my
current grammar attempts to allow these:
  @supports (display:block) {}
  @supports (display:block) and (display:inline) {}
  @supports not (display:block) {}
but it disallows:
  @supports display:block {}
I'm inclined to remove that restriction as well and allow the last
of the above as well.

Does this seem reasonable?  If so, I'll attempt to restructure the
grammar along these lines.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla Corporation               http://www.mozilla.com/   𝄂
Received on Wednesday, 10 August 2011 00:29:35 GMT

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