[css-syntax] Define <urange> in terms of tokens. The definition is looser than it originally was, which vastly simplifies the specification and recognition of the token, without harming use.

--HG--
extra : rebase_source : edbe8a3d5531121e48c0940a45641b261d702967

Author: tabatkins

css-syntax/Overview.bs

@@ -2973,8 +2973,105 @@ The <<urange>> type</h3>
 	(using the <a href="http://www.w3.org/TR/css3-values/#value-defs">Value Definition Syntax in the Values & Units spec</a>) as:
 
 	<pre class="prod">
+		<<urange>> =
+			u '+' <<urange-codepoint>> |
+			u '+' <<urange-codepoint>>? '?'+ |
+			u '+' <<urange-codepoint>> <<negative-urange-codepoint>> |
+			u '+' <<urange-range>>
 	</pre>
 
+	where:
+
+	: <dfn><<urange-codepoint>></dfn>
+	:: One of the following:
+		* A <<number-token>> whose type flag is set to "integer" and whose representation is composed solely of <a>digits</a> (no leading "+" or "-" characters).
+		* An <<ident-token>> whose representation is solely <a>hex digits</a>.
+		*  A <<dimension-token>> whose type flag is set to "integer" and whose unit is composed solely of <a>hex digits</a>
+
+	: <dfn><<negative-urange-codepoint>></dfn>
+	:: One of the following:
+		* A <<number-token>> whose type flag is set to "integer", and whose value is negative.
+			(If the implementation does not support <a href="https://en.wikipedia.org/wiki/Signed_zero">negative zero</a>,
+			then when the value is zero,
+			the implementation must additionally verify that the representation begins with U+002D HYPHEN-MINUS (-).)
+		* An <<ident-token>> whose representation is U+002D HYPHEN-MINUS, followed solely <a>hex digits</a>.
+		* A <<dimension-token>> whose type flag is set to "integer",
+			whose value is negative,
+			and whose unit is composed solely of <a>hex digits</a>.
+			(Same caveat as for <<number-token>> applies here.)
+
+	: <dfn><<urange-range>></dfn>
+	:: One of the following:
+		* An <<ident-token>> whose representation consists solely of
+			one or more <a>hex digits</a>,
+			followed by U+002D HYPHEN-MINUS (-),
+			followed by one or more <a>hex digits</a>.
+		* A <<dimension-token>> whose type flag is set to "integer",
+			and whose unit consists solely of
+			one or more <a>hex digits</a>,
+			followed by U+002D HYPHEN-MINUS (-),
+			followed by one or more <a>hex digits</a>.
+
+	In this production,
+	no whitespace can occur between any of the tokens.
+
+	The <<urange>> production represents a range of one or more contiguous unicode code points,
+	which are non-negative integers.
+	Each clause of the above grammar is interpreted as follows:
+
+	: <code>u '+' <<urange-codepoint>></code>
+	::
+		<a title="interpret a token as a hex integer">Interpret the &lt;urange-codepoint> as a hex integer</a>.
+		The <<urange>> represents a range consisting only of the resulting value.
+
+	: <code>u '+' <<urange-codepoint>>? '?'+</code>
+	::
+		If the <<urange-codepoint>> is specified,
+		let <var>B</var> be the result of <a title="interpret a token as a hex integer">interpreting the &lt;urange-codepoint> as a hex integer</a>;
+		otherwise, let <var>B</var> be zero.
+		Let <var>S</var> be the number of contiguous U+003F QUESTION MARK (?) codepoints.
+
+		The <<urange>> represents a contiguous range from
+		<code style="white-space: nowrap">B✕(16<sup>S</sup>)</code> to
+		<code style="white-space: nowrap">B✕(16<sup>S</sup>) + 16<sup>S+1</sup> − 1</code>,
+		inclusive.
+
+	: <code>u '+' <<urange-codepoint>> <<negative-urange-codepoint>></code>
+	::
+		Let <var>starting value</var> be the result of <a title="interpret a token as a hex integer">interpreting the &lt;urange-codepoint> as a hex integer</a>.
+		Let <var>ending value</var> be the negation of the result of <a title="interpret a token as a hex integer">interpreting the &lt;negative-urange-codepoint> as a hex integer</a>.
+
+		The <<urange>> represents a contiguous range from <var>starting value</var> to <var>ending value</var>, inclusive.
+
+	: <code>u '+' <<urange-range>></code>
+	::
+		Split the <<urange-range>>’s representation (or representation + unit)
+		into the two halves on either side of the U+002D HYPHEN-MINUS (-) codepoint.
+		Interpret each half as a hexadecimal integer.
+
+		The <<urange>> represents a contiguous range from the first half's value to the second half's value, inclusive.
+
+	To <dfn>interpret a token as a hex integer</dfn>:
+
+	* If the token is a <<number-token>> whose type flag is set to "integer",
+		interpret its representation as a hexadecimal number
+		and return the resulting value.
+
+	* If the token is an <<ident-token>> consisting solely of <a>hex digits</a>,
+		interpret its representation as a hexadecimal number
+		and return the resulting value.
+
+	* If the token is a <<dimension-token>> whose type flag is set to "integer"
+		and whose unit consists solely of <a>hex digits</a>,
+		concatenate its representation and its unit,
+		then interpret that as a hexadecimal number
+		and return the resulting value.
+
+	* Otherwise, the token can't be interpreted as a hex integer.
+		It is a specification error to reach this clause.
+
+
+
 
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