[css-sizing-4] Add property to switch among behaviors for zeroing out…

… min-content contributions. w3c#4585

css-sizing-4/Overview.bs

@@ -476,7 +476,7 @@ Min/Max Size Transfers</h3>
 <h2 id='intrinsic'>
 Intrinsic Size Determination</h2>
 
-<h3 id="intrinsic-contribution">
+<h3 id="intrinsic-sizes">
 Intrinsic Sizes</h3>
 
 	ISSUE: [[css-sizing-3#intrinsic-sizes]]
@@ -628,6 +628,69 @@ Intrinsic Size Contributions</h3>
 
 	ISSUE: [[css-sizing-3#intrinsic-contribution]]
 
+<h3 id='intrinsic-contribution-override'>
+Zeroing Min-Content Size Contributions: the 'min-intrinsic-sizing' property</h3>
+
+	<pre class="propdef">
+	Name: min-intrinsic-sizing
+	Value: legacy | zero-if-scroll || zero-if-extrinsic
+	Initial: legacy
+	Inherited: no
+	Applies to: all elements except [=inline boxes=]
+	Computed value: as specified
+	Percentages: n/a
+	Animation type: discrete
+	</pre>
+
+	ISSUE: This property seriously needs some name bikeshedding.
+
+	This property defines whether the [=min-content contribution=]
+	of a [=non-replaced=] box
+	is “compressed” under certain circumstances.
+	Values have the following meanings:
+
+	<dl dfn-for=min-intrinsic-size dfn-type=value>
+		<dt><dfn>legacy</dfn>
+		<dd>
+			The box’s [=min-content contribution=]
+			is handled as normal.
+
+		<dt><dfn>zero-if-scroll</dfn>
+		<dd>
+			The box’s [=min-content contribution=]
+			is “compressed” if it is a [=scroll container=].
+
+		<dt><dfn>zero-if-extrinsic</dfn>
+		<dd>
+			The box’s [=min-content contribution=]
+			is “compressed” if has an [=extrinsic size|extrinsic=]
+			[=preferred size|preferred=] or [=maximum size|maximum=] size.
+
+			Note: This is the default behavior of most [=replaced elements=].
+	</dl>
+
+	<div class="example">
+		The following rule will make all [=scroll containers=]
+		essentially ignore their contents
+		when passing up their size contributions
+		(unless they specifically requested a content-based size):
+
+		<pre highlight=css>*, ::before, ::after { min-intrinsic-size: zero-if-scroll; }</pre>
+
+		This prevents the [=scroll container=] from blowing up the size of its ancestors
+		if it contains large items such as a table or long lines of unbreakable text.
+		Meanwhile, it allows boxes that are not scroll containers
+		to continue influencing the [=min-content size=] of their ancestors.
+	</div>
+
+	Note: The behavior of ''zero-if-scroll'' would have been a better default,
+	but due to Web-compat, it cannot be the initial value. :(
+
+	The “compressed” [=min-content contributions=] is calculated
+	by pretending the box were empty,
+	except when factoring in sizing constraints imposed by explicit
+	''width/min-content'', ''width/max-content'', and ''width/fit-content'' values
+	of the [=sizing properties=].
 
 <!--
 ████████ ██     ██ ████████ ████████  ████ ██    ██  ██████  ████  ██████