[css-grid] Attempt to fix the handling of fit-content() to make more sense per issue #209. (This needs review.)

Author: fantasai

css-grid/Overview.bs

@@ -3508,7 +3508,7 @@ Grid Sizing</h2>
 
 	<ul>
 		<li>A <dfn>fixed sizing function</dfn> (<<length>> or resolveable <<percentage>>).
-		<li>An <dfn>intrinsic sizing function</dfn> (''min-content'', ''max-content'', or ''auto'').
+		<li>An <dfn>intrinsic sizing function</dfn> (''min-content'', ''max-content'', ''auto'', ''fit-content()'').
 		<li>A <dfn>flexible sizing function</dfn> (<<flex>>).
 	</ul>
 
@@ -3607,9 +3607,9 @@ Track Sizing Terminology</h3>
 		<dd>
 			If the track was sized with a ''minmax()'' function,
 			this is the second argument to that function.
-			If the track was sized with a ''fit-content()'' function,
-			''max-content''.
 			Otherwise, the track's sizing function.
+			In all cases, treat ''auto'' and ''fit-content()'' as ''max-content'',
+			except where specified otherwise for ''fit-content()''.
 
 		<dt><dfn>available grid space</dfn>
 		<dd>
@@ -3766,11 +3766,13 @@ Resolve Intrinsic Track Sizes</h3>
 					set its <a>growth limit</a>
 					to the maximum of the items’ <a>min-content contributions</a>.
 
-				<dt>For max-content and auto maximums:
+				<dt>For max-content maximums:
 				<dd>
-					If the track has a ''max-content'' or ''auto'' <a>max track sizing function</a>,
+					If the track has a ''max-content'' <a>max track sizing function</a>,
 					set its <a>growth limit</a>
 					to the maximum of the items’ <a>max-content contributions</a>.
+					For ''fit-content()'' maximums,
+					furthermore clamp this <a>growth limit</a> by the ''fit-content()'' argument.
 			</dl>
 
 			In all cases, if a track’s <a>growth limit</a> is now less than its <a>base size</a>,
@@ -3786,7 +3788,7 @@ Resolve Intrinsic Track Sizes</h3>
 				<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''
+					an <a lt="intrinsic sizing function">intrinsic</a> <a>min track sizing function</a>
 					by <a href="#extra-space">distributing extra space</a> as needed
 					to accommodate the contributions dictated by these items’ <a>min-size contributions</a>.
 				<li>
@@ -3811,7 +3813,7 @@ Resolve Intrinsic Track Sizes</h3>
 				<li>
 					<strong>For intrinsic maximums:</strong>
 					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'')
+					an <a lt="intrinsic sizing function">intrinsic</a> <a>max track sizing function</a>
 					by <a href="#extra-space">distributing extra space</a> as needed
 					to account for these items' <a>min-size contributions</a>.
 					Mark any tracks whose <a>growth limit</a> changed
@@ -3860,9 +3862,11 @@ 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'' (including ''auto'')
+					a <a>max 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>.
+					However, limit the growth of any ''fit-content()'' tracks
+					by their ''fit-content()'' argument.
 			</ol>
 
 			Repeat incrementally for items with greater spans until all items have been considered.
@@ -3925,6 +3929,11 @@ Resolve Intrinsic Track Sizes</h3>
 						<li>when handling any intrinsic <a>growth limit</a>:
 							all affected tracks.
 					</ul>
+
+					For this purpose, ''fit-content()'' tracks are treated as ''max-content''
+					until they reach the limit specified as the ''fit-content()'' argument,
+					after which they are treated as having a <a>fixed sizing function</a> of that argument.
+
 				<li>
 					<strong>Update the tracks' affected sizes</strong>
 					by folding in the calculated increase
@@ -3945,9 +3954,6 @@ Maximize Tracks</h3>
 	If the <a>free space</a> is positive, distribute it equally to all tracks,
 	freezing tracks as they reach their <a>growth limits</a>
 	(and continuing to grow the unfrozen tracks as needed).
-	For tracks sized with ''fit-content()'',
-	first clamp the <a>growth limit</a>
-	by the track sizing function given as the ''fit-content()'' argument.
 
 	For the purpose of this step:
 	if sizing the <a>grid container</a> under a <a>max-content constraint</a>,