CSS Values and Units Module Level 3

''string''

The attribute value is taken as the contents of a CSS <>. The default is the empty string. Note: this does not reparse the attribute value with the CSS parser. So, for example, an attribute whose value is "\33" will produce a string containing those three characters, not a string containing "3" (the character that the escape would evaluate to).

''color''

The attribute value must parse as a HASH or IDENT CSS token, and be successfully interpreted as a <>. The default is ''currentcolor''.

''url''

The attribute value is taken as the contents of a CSS <>. It is interpreted as a quoted string within the ''url()'' notation. The default is ''about:invalid'', which is a URL defined (in Appendix A) to point to a non-existent document with a generic error condition. Relative URLs must be made absolute according to the rules of the document language as applied to URLs originating from the element; they are not relative to the style sheet.

''integer''

The attribute value must parse as a NUMBER CSS token, and be successfully interpreted as an <>. The default is ''0'', or else the property's minimum value if ''0'' is not valid for the property. The default must also be used if the property in question only accepts integers within a certain range and the attribute is out of range.

''number''

The attribute value must parse as a NUMBER CSS token, and is interpreted as an <>. The default is ''0'', or else the property's minimum value if ''0'' is not valid for the property. The default must also be used if the property in question only accepts integers within a certain range and the attribute is out of range.

''length''

''angle''

''time''

''frequency''

The attribute value must parse as a DIMENSION CSS token, and be successfully interpreted as the specified type. The default is ''0'' in the relevant units, or else the property's minimum value if ''0'' in the relevant units is not valid for the property. The default must also be used if the property in question only accepts values within a certain range (e.g. positive lengths or angles from 0 to 90deg) and the attribute is out of range (e.g. a negative length or 180deg). If the unit is a relative length, it must be computed to an absolute length.

''em''

''ex''

''px''

''rem''

''vw''

''vh''

''vmin''

''vmax''

''mm''

''cm''

''in''

''pt''

''pc''

''deg''

''grad''

''rad''

''ms''

''s''

''Hz''

''kHz''

''%''

The attribute value must parse as a NUMBER CSS token, and is interpreted as a dimension with the specified unit. The default is ''0'' in the relevant units, or else the property's minimum value if ''0'' in the relevant units is not valid for the property. The default must also be used if the property in question only accepts values within a certain range (e.g. positive lengths or angles from 0 to 90deg) and the attribute is out of range (e.g. a negative length or 180deg). If the unit is a relative length, it must be computed to an absolute length.

		<stock>
			<wood length="12"/>
			<wood length="5"/>
			<metal length="19"/>
			<wood length="4"/>
		</stock>

		stock::before {
			display: block;
			content: "To scale, the lengths of materials in stock are:";
		}
		stock > * {
			display: block;
			width: attr(length em); /* default 0 */
			height: 1em;
			border: solid thin;
			margin: 0.5em;
		}
		wood {
			background: orange url(wood.png);
		}
		metal {
			background: silver url(metal.png);
		}
		

		content: attr(title color); /* 'content' doesn't accept colors */

		content: attr(end-of-quote string, inherit) close-quote;
		/* the 'inherit' value is not allowed there, since the result would be
		'inherit close-quote', which is invalid. */

		margin: attr(vertical length) attr(horizontal deg);
		/* deg units are not valid at that point */

		color: attr(color); /* 'color' doesn't accept strings */
		

Appendix A: IANA Considerations

Registration for the about:invalid URL scheme

Acknowledgments

Changes

• Specified that, in the absence of font information, ''1ch'' equal ''.5em''.
• Added ''q'' unit.
• Relaxed unnecessary restrictions on <>. Require specs referencing it to be clear about excluded keywords, because the new rule isn't as simple.
• Clarified relative URL resolution for embedded style sheets.
• Clarified {A} variant of {A,B} notation.
• Added notation for restricting the length of comma-separated lists specified with the ''#'' notation.
• Clarified handling of ''toggle()'' when used in shorthand declarations.
• Clarified that stringing together re-orderable combinations allows interleaving.
• Changed syntax references from the 2.1 grammar to the Syntax spec.

A Disposition of Comments is available. Changes since the 28 August 2012 Candidate Recommendation are:

• Corrected wqname in the ''attr()'' syntax to qname
• Made undefined namespace prefixes in ''attr()'' invalidate the function.
• Per WG resolution, made viewport-percentage units respect scrollbars on the viewport unless 'overflow' is ''auto'' (in which case they ignore the presence of scrollbars).
• Deferred exact definition of viewport-percentage units in paged media to CSS Paged Media.
• Added back the <> term as a convenience notation, so that other specs can refer to it.

• Noted that the list of CSS-wide keywords may be expanded by other specs.
• Clarified definition of ''ex'' to refer to the “first available font”.
• Specified that ''attr()'' with ''string'' or ''url'' types doesn't reparse the attribute contents, just takes the value literally as the value of a <>.