CSS WG Blog Minutes San Diego F2F August 2012: Cascadi…

Minutes San Diego F2F August 2012: Cascading Variables

Cascading Variables

• Resolved: Syntax of variables settled on var-foo and var(foo); i.e. not using $foo notation.
• Action: TabAtkins, fantasai, and glazou to write blog post explaining why not using $.
• Resolved: Include fallback in Level 1.
• Resolved: Defer parent-var() to Level 2.
• Resolved: Accept Variables Level 2 with parent-var() as work item.
• Resolved: Publish WD of CSS Variables providing sentence jdaggett objects to is removed.

The CSS Working Group chose not to adopt a $foo syntax and to continue using a functional notation for this feature for several reasons:

• The scope of a variable declaration, like a CSS property declaration, cascades and inherits through the element tree. This behavior is fundamentally different from every server-side processing language that uses $foo and cannot be duplicated on the server side.
• These variables can only be used within property values. They are not global macros. Languages that allow $foo usually treat them as macro expansions that can be used anywhere, for example to shorten selectors or to represent multiple declarations in a declaration block.
• There are reasons to want general-use macros in CSS. Not using $foo leaves this syntax open to future extensions of CSS and allows either server-side macros or a future CSS macro expansion feature to co-exist with cascading variables.
• Using a functional notation allows extensions like specifying fallback values (var(foo, fallback-value)) or using the parent’s scope (parent-var(foo)) to be simple extensions consistent with the basic syntax.

For further reading on this topic, see “Let’s Talk about CSS Variables” by Tab Atkins (CSSWG spec editor) and “CSS Variables, why we drop the $foo notation” by Daniel Glazman (CSSWG co-chair).

Full minutes

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