[css-values-4] Add a dfn for 'round to the nearest integer', since CS…

…S is consistent in how it does this. #5689
w3c · Oct 21, 2021 · b4739bc · b4739bc
1 parent 0b0c3c5
commit b4739bc
Showing 1 changed file with 15 additions and 9 deletions.
diff --git a/css-values-4/Overview.bs b/css-values-4/Overview.bs
@@ -1111,6 +1111,13 @@ Integers: the <<integer>> type</h3>
 	css/CSS2/values/numbers-units-004.xht
 	</wpt>
 
+	Unless otherwise specified,
+	in the CSS specifications
+	<dfn for=CSS export lt="round to the nearest integer">rounding to the nearest integer</dfn>
+	requires rounding in the direction of +∞
+	when the fractional portion is exactly 0.5.
+	(For example, ''1.5'' rounds to ''2'', while ''-1.5'' rounds to ''-1''.)
+
 <h4 id="combine-integers">
 Computation and Combination of <<integer>></h4>
 
@@ -1124,8 +1131,7 @@ Computation and Combination of <<integer>></h4>
 		<var>p</var> &times; <var>V<sub>b</sub></var>);
 	that is, interpolation happens in the real number space
 	as for <<number>>s, and the result is converted to an <<integer>>
-	by rounding to the nearest integer,
-	with values halfway between adjacent integers rounded towards positive infinity.
+	by [=rounding to the nearest integer=].
 
 	<a>Addition</a> of <<integer>> is defined as
 	<var>V<sub>result</sub></var> =
@@ -3303,6 +3309,7 @@ Stepped Value Functions: ''round()'', ''mod()'', and ''rem()''</h3>
 
 	If <<rounding-strategy>> is omitted,
 	it defaults to ''nearest''.
+	(Aka [=rounding to the nearest integer=].)
 
 	Issue(5689): CSSOM needs to specify how it rounds,
 	and it's probably good for CSS functions to round the same way by default.
@@ -4135,9 +4142,8 @@ Type Checking</h3>
 	</div>
 
 	Additionally, [=math functions=] that resolve to <<number>>
-	can be used in any place that only accepts <<integer>>.
-	(It gets rounded to the nearest integer,
-	as specified in [[#calc-range]].)
+	can be used in any place that only accepts <<integer>>;
+	the value is [=rounded to the nearest integer=] as it resolves.
 
 	Operators form sub-expressions, which gain types based on their arguments.
 
@@ -4676,9 +4682,8 @@ Range Checking</h3>
 
 	Additionally, if a [=math function=] that resolves to <<number>>
 	is used somewhere that only accepts <<integer>>,
-	the [=computed value=] and [=used value=] are rounded to the nearest integer,
+	the [=computed value=] and [=used value=] are [=rounded to the nearest integer=],
 	in the same manner as clamping, above.
-	The rounding method must be the same as is used for animations of integer values.
 
 	<div class=example>
 		Since widths smaller than 0px are not allowed,
@@ -4995,8 +5000,9 @@ Appendix A: Recommended Minimum Ranges and Precision of Computed Values</h2>
 		(for example, in the ''calc()'' expression),
 		if the result is unsupported
 		it must also be clamped/rounded as necessary.
-	<span class="note">
-		Note this means that rounding errors <em>may</em> accumulate.
+		<span class="note">
+			Note this means that rounding errors <em>may</em> accumulate.
+		</span>
 -->