[css-values-4] Sync with L3

Author: fantasai

css-values-4/Overview.bs

@@ -68,11 +68,13 @@ Module Interactions</h3>
 <h2 id="value-defs">
 Value Definition Syntax</h2>
 
-	The syntax described here is used to define the set of valid values
-	for CSS properties. A property value can have one or more components.
+	The <dfn for=CSS export>value definition syntax</dfn> described here
+	is used to define the set of valid values for CSS properties
+	(and the valid syntax of many other parts of CSS).
+	A value so described can have one or more components.
 
 <h3 id="component-types">
-Component value types</h3>
+Component Value Types</h3>
 
 	Component value types are designated in several ways:
 
@@ -84,6 +86,9 @@ Component value types</h3>
 		<li>
 			basic data types, which appear between <css>&lt;</css> and <css>></css>
 			(e.g., <<length>>, <<percentage>>, etc.).
+			For <a>numeric data types</a>,
+			this type notation can annotate any range restrictions
+			using the [[#numeric-ranges|bracketed range notation]] described below.
 
 		<li>
 			types that have the same range of values as a property bearing the same name
@@ -169,7 +174,7 @@ Component value types</h3>
 	''background: url(corner.png) no-repeat, inherit;'' is invalid.
 
 <h3 id="component-combinators">
-Component value combinators</h3>
+Component Value Combinators</h3>
 
 	Component values can be arranged into property values as follows:
 
@@ -205,7 +210,7 @@ Component value combinators</h3>
 	</pre>
 
 <h3 id="component-multipliers">
-Component value multipliers</h3>
+Component Value Multipliers</h3>
 
 	Every type, keyword, or bracketed group may be followed by one of
 	the following modifiers:
@@ -286,7 +291,7 @@ Combinator and Multiplier Patterns</h3>
 	while the "in order" possibilities are all variants on juxtaposition.
 
 <h3 id="component-whitespace">
-Component values and white space</h3>
+Component Values and White Space</h3>
 
 	Unless otherwise specified,
 	<a href="https://www.w3.org/TR/css-syntax/#whitespace">white space</a> and/or comments may appear before, after, and/or between
@@ -303,7 +308,7 @@ Component values and white space</h3>
 	to get this parsed as the two lengths ''1em'' and ''2em''.
 
 <h3 id="value-examples">
-Property value examples</h3>
+Property Value Examples</h3>
 
 	Below are some examples of properties with their corresponding value
 	definition fields
@@ -442,7 +447,9 @@ Combining Values: Interpolation, Addition, and Accumulation</h2>
 <h2 id="textual-values">
 Textual Data Types</h2>
 
-	Textual data types are used to represent identifiers or text.
+	The <dfn>textual data types</dfn> include
+	various keywords and identifiers
+	as well as strings (<<string>>) and URLs (<<url>>).
 	Aside from the casing of <a href="#keywords">pre-defined keywords</a>
 	or as explicitly defined for a given property,
 	no normalization is performed,
@@ -542,7 +549,7 @@ Author-defined Identifiers: the <<custom-ident>> type</h3>
 		For example, the shorthand declaration ''animation: ease-in ease-out''
 		is equivalent to the longhand declarations
 		''animation-timing-function: ease-in; animation-name: ease-out;''.
-		''ease-in'' is claimed by the <<timing-function>> production belonging to 'animation-timing-function',
+		''ease-in'' is claimed by the <<easing-function>> production belonging to 'animation-timing-function',
 		leaving ''ease-out'' to be claimed by the <<custom-ident>> production belonging to 'animation-name'.
 	</div>
 
@@ -782,18 +789,60 @@ Numeric Data Types</h2>
 	they represent the value’s abstract quantity,
 	not its syntactic representation.
 
-		Properties may restrict numeric values to some range.
-		If the value is outside the allowed range,
-		unless otherwise specified,
-		the declaration is invalid and must be <a href="https://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
+	The <dfn>numeric data types</dfn> include
+	<<integer>>,
+	<<number>>,
+	<<percentage>>,
+	and various <a>dimensions</a>
+	including <<length>>, <<angle>>, <<time>>, <<frequency>>, and <<resolution>>.
+
+	Note: While general-purpose <a>dimensions</a> are defined here,
+	some other modules define additional data types
+	(e.g. [[css-grid-1]] introduces ''fr'' units)
+	whose usage is more localized.
+
+<h3 id="numeric-ranges">
+Range Restrictions and Range Definition Notation</h3>
+
+	Properties can restrict numeric values to some range.
+	If the value is outside the allowed range,
+	then unless otherwise specified,
+	the declaration is invalid and must be <a href="https://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
+	Range restrictions can be annotated in the numeric type notation
+	using <dfn local-lt="bracketed range notation">CSS bracketed range notation</dfn>--
+	<code>[<var>min</var>,<var>max</var>]</code>--
+	within the angle brackets, after the identifying keyword,
+	indicating a closed range
+	between (and including) <var>min</var> and <var>max</var>.
+	For example, <<integer [0,10]>> indicates an integer between ''0'' and ''10'', inclusive.
+
+	Note: CSS values generally do not allow open ranges;
+	thus only square-bracket notation is used.
+
+	CSS theoretically supports infinite precision and infinite ranges for all value types;
+	however in reality implementations have finite capacity.
+	UAs should support reasonably useful ranges and precisions.
+	Range extremes that are ideally unlimited
+	are indicated using &infin; or &minus;&infin; as appropriate.
+
+	If no range is indicated,
+	either by using the <a>bracketed range notation</a>
+	or in the property description,
+	then <code>[&minus;&infin;,&infin;]</code> is assumed.
+
+	Note: At the time of writing,
+	the <a>bracketed range notation</a> is new;
+	thus in most CSS specifications
+	any range limitations are described only in prose.
+	(For example, “Negative values are not allowed” or
+	“Negative values are invalid”
+	indicate a <code>[0,&infin;]</code> range.)
+	This does not make them any less binding.
 
-		CSS theoretically supports infinite precision and infinite ranges for all value types;
-		however in reality implementations have finite capacity.
-		UAs should support reasonably useful ranges and precisions.
 <!--
-		The recommended minimum ranges and precision,
-		and the required rounding and clamping rules,
-		are given in <a href="#required-ranges">Appendix A</a>.
+	The recommended minimum ranges and precision,
+	and the required rounding and clamping rules,
+	are given in <a href="#required-ranges">Appendix A</a>.
 -->
 
 <!--
@@ -893,6 +942,10 @@ Numbers with Units: <a>dimension</a> values</h3>
 	in the <a href="https://www.w3.org/TR/css-syntax/">CSS Syntax Module</a> [[!CSS3SYN]].
 	Like keywords, unit identifiers are <a>ASCII case-insensitive</a>.
 
+	<wpt>
+	css/css-values/angle-units-003.html
+	</wpt>
+
 	CSS uses <<dimension>>s to specify
 	distances (<<length>>),
 	durations (<<time>>),
@@ -1089,7 +1142,7 @@ Distance Units: the <<length>> type</h2>
 	There are two types of length units: <a lt="relative length">relative</a> and <a lt="absolute length">absolute</a>.
 
 <h3 id="relative-lengths">
-Relative lengths</h3>
+Relative Lengths</h3>
 
 	<dfn lt="relative length">Relative length units</dfn> specify a length relative to another length.
 	Style sheets that use relative units can more easily scale from one output environment to another.
@@ -1151,7 +1204,7 @@ Relative lengths</h3>
 -->
 
 <h4 id="font-relative-lengths">
-Font-relative lengths: the ''em'', ''ex'', ''cap'', ''ch'', ''ic'', ''rem'', ''lh'', ''rlh'' units</h4>
+Font-relative Lengths: the ''em'', ''ex'', ''cap'', ''ch'', ''ic'', ''rem'', ''lh'', ''rlh'' units</h4>
 
 	The <dfn export id="font-relative-length">font-relative lengths</dfn>
 	refer to the font metrics of the element on which they are used--
@@ -1313,7 +1366,7 @@ Font-relative lengths: the ''em'', ''ex'', ''cap'', ''ch'', ''ic'', ''rem'', ''l
 -->
 
 <h4 id="viewport-relative-lengths">
-Viewport-percentage lengths: the ''vw'', ''vh'', ''vi'', ''vb'', ''vmin'', ''vmax'' units</h4>
+Viewport-percentage Lengths: the ''vw'', ''vh'', ''vi'', ''vb'', ''vmin'', ''vmax'' units</h4>
 
 	The <dfn export>viewport-percentage lengths</dfn> are relative to the size of the
 	<a href="https://www.w3.org/TR/CSS21/visudet.html#containing-block-details">initial containing block</a>.
@@ -1377,7 +1430,7 @@ Viewport-percentage lengths: the ''vw'', ''vh'', ''vi'', ''vb'', ''vmin'', ''vma
 -->
 
 <h3 id="absolute-lengths">
-Absolute lengths: the ''cm'', ''mm'', ''Q'', ''in'', ''pt'', ''pc'', ''px'' units</h3>
+Absolute Lengths: the ''cm'', ''mm'', ''Q'', ''in'', ''pt'', ''pc'', ''px'' units</h3>
 
 	The <dfn lt="absolute length">absolute length units</dfn> are fixed in relation to each other
 	and anchored to some physical measurement.
@@ -1430,7 +1483,7 @@ Absolute lengths: the ''cm'', ''mm'', ''Q'', ''in'', ''pt'', ''pc'', ''px'' unit
 	All of the absolute length units are <a>compatible</a>,
 	and ''px'' is their <a>canonical unit</a>.
 
-	For a CSS device, these dimensions are <dfn export lt="anchor unit">anchored</dfn> either
+	For a CSS device, these dimensions are <dfn lt="anchor unit | anchor">anchored</dfn> either
 
 	<ol type=i>
 		<li>by relating the <a>physical units</a> to their physical measurements, or