From: Kang-Hao (Kenny) Lu <kennyluck@csail.mit.edu>

Date: Wed, 04 Jul 2012 15:09:42 +0800

Message-ID: <4FF3EC36.1070005@csail.mit.edu>

To: "Tab Atkins Jr." <jackalmage@gmail.com>

CC: WWW Style <www-style@w3.org>

Date: Wed, 04 Jul 2012 15:09:42 +0800

Message-ID: <4FF3EC36.1070005@csail.mit.edu>

To: "Tab Atkins Jr." <jackalmage@gmail.com>

CC: WWW Style <www-style@w3.org>

(12/04/24 3:55), Tab Atkins Jr. wrote: > Issue 2: calc() and attr() need to resolve values that are normally > changed at computed-value time > Closed as Accepted - the spec now says "The computed value of a calc() > expression is the expression with all components computed, with all > multiplication/division subexpressions resolved, and with all > addition/subtraction subexpressions resolved where both sides are the > same type." > > Let us know if this is acceptable! Sorry but I just realized the current wording is sort of vague when talking about a corner case: 'height: calc(0*0%)'. It is treated as 'height: auto' in IE9, Firefox13 and a Chrome version with '-webkit-calc', similar to 'height: 0%', not 'height: 0'. Therefore, the note # Thus, the computed value of a ‘calc()’ expression can be # represented as either a number or a tuple of a dimension and a # percentage. is sort of inexact in that it doesn't say '0' and 'undefined' are different. The spec should provide a hint to css3-flexbox too. calc(0*0%) should probably be treated as indefinite if resolved against an indefinite length. Also, I think "same type" in the quoted prose here should be elaborated a little bit. The rest of the description of 'calc()' talks about "resolved type", but both <percentage> and <length> have the same "resolved type" for the cases we care. Proposed wording (just a try): | The computed value of a calc() expression is the expression with | all components computed with all multiplication/division | subexpressions resolved, and with all addition/subtraction | subexpressions resolved where both sides are the the same type, | unless one of which is <percentage> (which doesn't compute to an | absolute unit) and the other isn't. User agents must track whether | a <percentage> is contained a calc() with a flag. | | If 'height' is specified with calc() containing a <percentage> | , the value must be treated as 'auto'. A length specified with | calc() containing a <percentage> when the <percentage> is resolved | against an indefinite length is an indefinite length. Otherwise, | it's definite. A somewhat irrelevant nit picking: # At ‘,’, ‘+’, or ‘-’, check that both sides have the same # type, or that one side is a <number> and the other is an <integer>. ',' is no longer relevant since we dropped max() and min(). Cheers, KennyReceived on Wednesday, 4 July 2012 07:10:09 GMT

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