[css-values-5] Define if() processing, add a note. #10064

fantasai · fantasai · commit 83dbaa789694 · 2024-10-28T18:42:16.000-04:00
diff --git a/css-values-5/Overview.bs b/css-values-5/Overview.bs
@@ -1343,6 +1343,18 @@ Conditional Value Selection: the ''if()'' notation</h3>
 	The <dfn value for="if()">else</dfn> keyword represents
 	a condition that is always true.
 
+	To <dfn export>[=resolve an arbitrary substitution function|resolve an if() function=]</dfn>,
+	return the <<declaration-value>>?
+	associated with the first <<if-condition>> that is true;
+	if none are true,
+	return nothing (an empty token stream).
+
+	Note: Unlike using ''@media''/''@supports''/''@container'' rules,
+	which just ignore their contents when they're false
+	and let the cascade determine what values otherwise apply,
+	declarations with ''if()'' do not roll back the cascade if the conditions are false;
+	any fallback values must be provided inline.
+
 <!-- Big Text: toggle()
 
 █████▌  ███▌   ███▌   ███▌  █▌    █████▌   ██ ██

-Original file line number
+Diff line change
 	The else keyword represents
 	a condition that is always true.
 +	To [=resolve an arbitrary substitution function|resolve an if() function=],
 +	return the <>?
 +	associated with the first <> that is true;
 +	if none are true,
 +	return nothing (an empty token stream).
++
 +	Note: Unlike using ''@media''/''@supports''/''@container'' rules,
 +	which just ignore their contents when they're false
 +	and let the cascade determine what values otherwise apply,
 +	declarations with ''if()'' do not roll back the cascade if the conditions are false;
 +	any fallback values must be provided inline.
++
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