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[css3-variables] custom properties and cascading variables

From: John Daggett <jdaggett@mozilla.com>
Date: Tue, 26 Feb 2013 19:42:38 -0800 (PST)
To: www-style list <www-style@w3.org>
Message-ID: <293272184.5396349.1361936558440.JavaMail.root@mozilla.com>

The current ED of the CSS Variables spec uses different terms to
describe the definition and use of variables.  I understand that
there's a need to distinguish what is being defined here from what
programmers or web authors typically think of as "variables" but I
think the use of these separate terms is confusing and isn't the best
way to describe the concepts being discussed.

When referring to the cascading variable definition, the term "custom
property" is used:

  A custom property is any property whose name is composed of
  "var-" followed by an <ident> [CSS3VAL] Custom properties are
  solely for use by authors and users; CSS will never give them a
  meaning beyond what is presented here. 

When referring to the variable usage, the term "cascading variable" is used

  The primary purpose of custom properties is to define cascading
  variables. In CSS, a cascading variable is a value that can be
  substituted into other properties, allowing authors to
  "abstract" parts of their page's CSS out and reuse it in
  several places. Every custom property defines a corresponding
  variable with the same name, minus the "var-" prefix. For
  example, the custom property ‘var-foo’ defines a variable named
  ‘foo’. See the next chapter for details on how to use
  variables. The module name is now:

Even the name of the module reflects this dichotomy:

  "CSS Custom Properties for Cascading Variables"

I think using different terms simply to describe use versus defintion
is poor word choice.  Historically the term "custom attribute" in HTML
meant the ability to stick arbitrary attributes into HTML elements, so
I think the term "custom property" implies something similar; in the
general sense it connotes properties with completely arbitrary names
that behave something like properties.  That's a superset of the
functionality here and so it would be much simpler to avoid this
confusing term.

I think it would be much better to use the same term for both
definition and use, so I would propose substituting "cascading
variable property" in place of "custom property".  I think that's a
more accurate way of describing the "var-foo: 16px" / "var(foo)"
syntax that's defined by this spec.


John Daggett
Received on Wednesday, 27 February 2013 03:43:05 UTC

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