[css-grid] Make 'auto' track sizing rely on min-size instead of always on min-content. Make min-size: auto affect grid items.

Author: fantasai

css-grid/Overview.bs

@@ -662,6 +662,12 @@ Grid Items</h2>
 	except that ''margin/auto'' margins and the <a>box alignment properties</a>
 	have special effects. (See [[#alignment]].)
 
+	The ''min-width/auto'' value of 'min-width' and 'min-height'
+	behaves on <a>grid items</a> in the relevant axis
+	analogously to its behavior on <a>flex items</a> in the <a>main axis</a>.
+	See [[!CSS3-FLEXBOX]].
+
+	ISSUE: Review implications of intrinsic ratio and Grid's 2D nature.
 
 <!--
 <h3 id="position-grid">
@@ -857,6 +863,9 @@ Track Sizing: the 'grid-template-rows' and 'grid-template-columns' properties</h
 			Each <<flex>>-sized track takes a share of the remaining space in proportion to its <a>flex factor</a>.
 			See <a href="#fr-unit">Flexible Lengths</a> for more details.
 
+			When appearing outside a ''minmax()'' notation,
+			implies an automatic minimum (i.e. ''minmax(auto, <<flex>>)'').
+
 		<dt><dfn>max-content</dfn>
 		<dd>
 			Represents the largest <a>max-content contribution</a>
@@ -880,7 +889,9 @@ Track Sizing: the 'grid-template-rows' and 'grid-template-columns' properties</h
 
 		<dt><dfn>auto</dfn>
 		<dd>
-			Computes to ''minmax(min-content, max-content)''.
+			As a maximum, identical to ''max-content''.
+			As a minimum, represents the largest minimum size (as specified by 'min-width'/'min-height')
+			of the <a>grid items</a> occupying the <a>grid track</a>.
 	</dl>
 
 	<div class='example'>
@@ -2599,7 +2610,7 @@ Grid Sizing</h2>
 
 	<ul>
 		<li>A <dfn>fixed sizing function</dfn> (<<length>> or resolveable <<percentage>>).
-		<li>An <dfn>intrinsic sizing function</dfn> (''min-content'' or ''max-content'').
+		<li>An <dfn>intrinsic sizing function</dfn> (''min-content'', ''max-content'', or ''auto'').
 		<li>A <dfn>flexible sizing function</dfn> (<<flex>>).
 	</ul>
 
@@ -2778,38 +2789,53 @@ Resolve Intrinsic Track Sizes</h3>
 					If the track has a ''max-content'' <a>min track sizing function</a>,
 					set its <a>base size</a>
 					to the maximum of the items’ <a>max-content contributions</a>.
+				<li>
+					<strong>For auto minimums:</strong>
+					If the track has an ''auto'' <a>min track sizing function</a>,
+					set its <a>base size</a>
+					to the maximum of the items’ outer minimum sizes,
+					as specified by their respective 'min-width' or 'min-height' properties
+					(whichever matches the relevant axis).
 				<li>
 					<strong>For min-content maximums:</strong>
 					If the track has a ''min-content'' <a>max track sizing function</a>,
 					set its <a>growth limit</a>
 					to the maximum of the items’ <a>min-content contributions</a>.
 				<li>
-					<strong>For max-content maximums:</strong>
-					If the track has a ''max-content'' <a>max track sizing function</a>,
+					<strong>For max-content and auto maximums:</strong>
+					If the track has a ''max-content'' or ''auto'' <a>max track sizing function</a>,
 					set its <a>growth limit</a>
 					to the maximum of the items’ <a>max-content contributions</a>.
 			</ul>
 		<li>
 			<strong>Increase sizes to accommodate spanning items:</strong>
 			Next, consider the items with a span of 2
 			that do not span a track with a <a>flexible sizing function</a>:
+			<!-- auto-min contribution <= min-content contribution <= max-content contribution -->
 			<ol>
 				<li>
 					<strong>For intrinsic minimums:</strong>
 					First increase the <a>base size</a> of tracks with
+					a <a>min track sizing function</a> of ''min-content'', ''max-content'', or ''auto''
+					by <a href="#extra-space">distributing extra space</a> as needed
+					to accommodate the contributions dictated by these items’
+					minimum size (as specified by 'min-width'/'min-height').
+				<li>
+					<strong>For content-based minimums:</strong>
+					Next continue to increase the <a>base size</a> of tracks with
 					a <a>min track sizing function</a> of ''min-content'' or ''max-content''
 					by <a href="#extra-space">distributing extra space</a> as needed
 					to account for these items' <a>min-content contributions</a>.
 				<li>
 					<strong>For max-content minimums:</strong>
-					Next continue to increase the <a>base size</a> of tracks with
+					Third continue to increase the <a>base size</a> of tracks with
 					a <a>min track sizing function</a> of ''max-content''
 					by <a href="#extra-space">distributing extra space</a> as needed
 					to account for these items' <a>max-content contributions</a>.
 				<li>
 					<strong>For intrinsic maximums:</strong>
-					Third increase the <a>growth limit</a> of tracks with
-					a <a>max track sizing function</a> of ''min-content'' or ''max-content''
+					Next increase the <a>growth limit</a> of tracks with
+					a <a>max track sizing function</a> of ''min-content'' or ''max-content'' (including ''auto'')
 					by <a href="#extra-space">distributing extra space</a> as needed
 					to account for these items' <a>min-content contributions</a>.
 					Mark any tracks whose <a>growth limit</a> changed
@@ -2819,7 +2845,7 @@ Resolve Intrinsic Track Sizes</h3>
 				<li>
 					<strong>For max-content maximums:</strong>
 					Lastly continue to increase the <a>growth limit</a> of tracks with
-					a <a>max track sizing function</a> of ''max-content''
+					a <a>max track sizing function</a> of ''max-content'' (including ''auto'')
 					by <a href="#extra-space">distributing extra space</a> as needed
 					to account for these items' <a>max-content contributions</a>.
 			</ol>