- From: Tab Atkins Jr. <jackalmage@gmail.com>
- Date: Wed, 27 Feb 2013 11:07:10 -0800
- To: John Daggett <jdaggett@mozilla.com>
- Cc: www-style list <www-style@w3.org>
On Wed, Feb 27, 2013 at 5:19 AM, John Daggett <jdaggett@mozilla.com> wrote: > Tab Atkins wrote: >> > The current ED of CSS Variables defines syntax for a fallback value [1]. >> > It defines the use of the fallback value this way: >> > >> > If the variable named by the first argument is valid, the >> > variable's value is substituted as normal. If it's invalid, and >> > a <fallback> was provided, the <fallback> is substituted >> > instead. Otherwise, the variable is an invalid variable. >> > >> > Does this mean that undefined variables cause the <fallback> to be substituted? >> >> Other text in that section defines that undefined variables are >> invalid. (Or rather, that all variables implicitly have an invalid >> value unless they're specified otherwise.) > > Ok, I see the problem. The second sentence in the spec quote is > unclear, the problem is what "If it's invalid" refers to. You intend > it to mean "If the variable is invalid.." but I read that as "If the > variable's value is invalid...". The last sentence is sort of odd too, > since the paragraph is really defining the return value of var() that > uses a variable and not the variable itself. > > Simple fix: > > If the variable named by the first argument is valid, the > variable's value is substituted as normal. If the variable is > invalid, and a <fallback> was provided, the <fallback> is > substituted instead. Otherwise, the result of evaluating the > var() function will mean that the containing declaration is > invalid at computed-value time. Cool, thanks. I tried writing it some other ways, but couldn't get it to come out right, so I just used your text. > Also, the line above this paragraph reads: > > The <fallback> value is identical to the syntax of a custom property. > > I think you mean "custom property *value*" instead of custom property. Indeed. Fixed. > So what is the use case that benefits from having a fallback value, > since it's basically only a fallback for undefined variables? Seems > like unnecessary complexity for level 1. Nope, quite useful for the theming use-case, where you use some variables in your component that may or may not be defined by the final author of the page. ~TJ
Received on Wednesday, 27 February 2013 19:07:57 UTC