[css-values-5] Define if() notation #10064 #5624 #5009 #6638 #4731 #3455

fantasai · fantasai · commit f70deb43d3fe · 2024-10-25T17:05:47.000-04:00
diff --git a/css-values-5/Overview.bs b/css-values-5/Overview.bs
@@ -1242,6 +1242,40 @@ Selecting the First Supported Value: the ''first-valid()'' notation</h3>
 	<<declaration-value>> imposes no contextual validity constraints on what it matches,
 	unlike <<whole-value>>.
 
+<!-- Big Text: if()
+-->
+
+<h3 id="if-notation">
+Conditional Value Selection: the ''if()'' notation</h3>
+
+	The <dfn>if()</dfn> notation is an [=arbitrary substitution function=]
+	that represents conditional values.
+	Its argument consists of an ordered semi-colon&ndash;separated list of statements,
+	each consisting of a condition
+	followed by a colon
+	followed by the value represented by this notation
+	if the corresponding condition is the first in the list to be true.
+	If no condition matches,
+	then the ''if()'' notation represents an empty token stream.
+
+	Note: [=Arbitrary substitution functions=] all resolve at [=computed value=] time;
+	therefore if the resulting property value is invalid,
+	it falls back to the property's [=initial value=]
+	rather than to an earlier value in the [=cascade=].
+
+	The ''if()'' notation syntax is defined as follows:
+
+	<pre class=prod>
+	<dfn><<if()>></dfn> = if( [ <<if-condition>> : <<declaration-value>>? ; ]*
+	             <<if-condition>> : <<declaration-value>>? ;? )
+	<dfn><<if-condition>></dfn> =
+	  supports( [ <supports-condition> | <declaration> ] ) |
+	  media( <<media-query>> ) |
+	  style( <<style-query>> ) |
+	  else
+	</pre>
+
+	ISSUE: Incorporate boolean syntax for combining these queries.
 
 <!-- Big Text: toggle()
 

-Original file line number
+Diff line change
 	<> imposes no contextual validity constraints on what it matches,
 	unlike <>.
++
++
++
 +Conditional Value Selection: the ''if()'' notation
++
 +	The if() notation is an [=arbitrary substitution function=]
 +	that represents conditional values.
 +	Its argument consists of an ordered semi-colon–separated list of statements,
 +	each consisting of a condition
 +	followed by a colon
 +	followed by the value represented by this notation
 +	if the corresponding condition is the first in the list to be true.
 +	If no condition matches,
 +	then the ''if()'' notation represents an empty token stream.
++
 +	Note: [=Arbitrary substitution functions=] all resolve at [=computed value=] time;
 +	therefore if the resulting property value is invalid,
 +	it falls back to the property's [=initial value=]
 +	rather than to an earlier value in the [=cascade=].
++
 +	The ''if()'' notation syntax is defined as follows:
++
++
 +	<> = if( [ <> : <>? ; ]*
 +	             <> : <>? ;? )
 +	<> =
 +	  supports( [  |  ] ) |
 +	  media( <> ) |
 +	  style( <> ) |
 +	  else
++
++
 +	ISSUE: Incorporate boolean syntax for combining these queries.
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