[css-grid] Remove 'stack' value, because it's dumb.

Author: tabatkins

css-grid/Overview.bs

@@ -1546,7 +1546,7 @@ Sizing Auto-generated Rows and Columns: the 'grid-auto-rows' and 'grid-auto-colu
 
 	<pre class='propdef'>
 	Name: grid-auto-flow
-	Value: <<auto-flow-direction>> || <<auto-flow-algorithm>>
+	Value: [ row | column ] || dense
 	Initial: row
 	Applies to: <a>grid containers</a>
 	Inherited: no
@@ -1555,68 +1555,40 @@ Sizing Auto-generated Rows and Columns: the 'grid-auto-rows' and 'grid-auto-colu
 	Computed value: specified value
 	</pre>
 
-	<pre class=prod>
-		<dfn>&lt;auto-flow-direction></dfn> = row | column
-		<dfn>&lt;auto-flow-algorithm></dfn> = dense | stack
-	</pre>
-
 	<a>Grid items</a> that aren't explicitly placed are automatically placed
 	into an unoccupied space in the <a>grid container</a>
 	by the <a>auto-placement algorithm</a>.
 	'grid-auto-flow' controls how the <a>auto-placement algorithm</a> works,
 	specifying exactly how auto-placed items get flowed into the grid.
 	See [[#auto-placement-algo]] for details on precisely how the auto-placement algorithm works.
 
-	The <<auto-flow-direction>> determines what direction the search for unoccupied space takes place,
-	and whether rows or columns are added as needed to accommodate the content.
-	If this is omitted, it means the same as specifying ''grid-auto-flow/row''.
-
-	<dl dfn-for="grid-auto-flow <auto-flow-direction>" dfn-type=value>
+	<dl dfn-for="grid-auto-flow" dfn-type=value>
 		<dt><dfn>row</dfn>
 		<dd>
 			The <a>auto-placement algorithm</a> places items
 			by filling each row in turn,
 			adding new rows as necessary.
+			If neither ''row'' nor ''column'' is provided,
+			''row'' is assumed.
 
 		<dt><dfn>column</dfn>
 		<dd>
 			The <a>auto-placement algorithm</a> places items
 			by filling each column in turn,
 			adding new columns as necessary.
-	</dl>
-
-	The <<auto-flow-algorithm>> determines how the search for free space is conducted,
-	and where items are placed.
-	If omitted, it indicates that a “sparse” algorithm is to be used.
-
-	<dl dfn-for="grid-auto-flow <auto-flow-algorithm>" dfn-type=value>
-		<dt>omitted (“sparse”)
-		<dd>
-			If the <<auto-flow-algorithm>> is not specified,
-			the auto-placement algorithm uses a “sparse” packing algorithm.
-			It maintains a “cursor” that gradually moves through the grid,
-			looking for sufficiently large unoccupied areas to place each auto-placed <a>grid item</a> in turn.
-			It never returns to already-searched areas of the grid,
-			even if a large <a>grid item</a> causes the “cursor” to skip over areas
-			that would be large enough to fit smaller subsequent <a>grid items</a>.
-
-			Note: While this algorithm can possibly leave large “holes” in a grid,
-			it ensures that all of the auto-placed items appear “in order”,
-			regardless of the shape of the items and the grid.
 
 		<dt><dfn>dense</dfn>
 		<dd>
-			If specified, the auto-placement algorithm uses a “dense” packing algorithm,
-			which attempts to fill in holes in the grid if smaller items come up later.
-
-			Note: This may cause items to appear out-of-order.
-
-		<dt><dfn>stack</dfn>
-		<dd>
-			The auto-placement algorithm is run with a single hypothetical 1×1 grid item,
-			and all of the auto-placed items are placed wherever that hypothetical item ends up.
-			(This happens even if the auto-placed item is greater than 1×1,
-			even if doing so would cause it to overlap explicitly-placed <a>grid items</a>.)
+			If specified, the <a>auto-placement algorithm</a> uses a “dense” packing algorithm,
+			which attempts to fill in holes earlier in the grid if smaller items come up later.
+			This may cause items to appear out-of-order,
+			when doing so would fill in holes left by larger items.
+
+			If omitted, a “sparse” algorithm is used,
+			where the placement algorithm only ever moves “forward” in the grid when placing items,
+			never backtracking to fill holes.
+			This ensures that all of the auto-placed items appear “in order”,
+			even if this leaves holes that could have been filled by later items.
 	</dl>
 
 	Note: A future level of this module is expected to add a value that flows auto-positioned items together into a single “default” cell.
@@ -2322,7 +2294,7 @@ Grid Item Placement Algorithm</h3>
 
 	To aid in clarity,
 	this algorithm is written with the assumption that 'grid-auto-flow'
-	has an <<auto-flow-direction>> of ''grid-auto-flow/row''.
+	has ''grid-auto-flow/row'' specified.
 	If it is instead set to ''grid-auto-flow/column'',
 	swap all mentions of rows and columns, inline and block, etc. in this algorithm.
 
@@ -2373,9 +2345,9 @@ Grid Item Placement Algorithm</h3>
 		specified as a pair of row and column <a>grid lines</a>.
 		Initially the <a>auto-placement cursor</a> at is specified with a row and column position both equal to 1.
 
-		The <<auto-flow-algorithm>> in use determines how to position the items:
+		The 'grid-auto-flow' value in use determines how to position the items:
 
-		: omitted (“sparse”)
+		: “sparse” packing (omitted ''dense'' keyword)
 		:: For each <a>grid item</a> that hasn't been positioned by the previous steps,
 			in <a>order-modified document order</a>:
 
@@ -2406,7 +2378,7 @@ Grid Item Placement Algorithm</h3>
 					set its column position to 1,
 					and return to the previous step.
 
-		: ''grid-auto-flow/dense''
+		: “dense” packing (''dense'' specified)
 		:: For each <a>grid item</a> that hasn't been positioned by the previous steps,
 			in <a>order-modified document order</a>:
 
@@ -2437,27 +2409,6 @@ Grid Item Placement Algorithm</h3>
 					set its column position to 1,
 					and return to the previous step.
 
-		: ''grid-auto-flow/stack''
-		:: Find the first unoccupied <a>grid cell</a> in the first row that contains an unoccupied <a>grid cell</a>.
-			This is the <dfn>default stacking cell</dfn>.
-			It is also the <dfn>default stacking cell for the column</dfn> that it is in.
-
-			For each <a>grid item</a> that hasn't been positioned by the previous steps,
-			in <a>order-modified document order</a>:
-
-			: If the item has a <a>definite column position</a>:
-			:: If the column corresponding to the item’s start-most column position
-				does not yet have a <a>default stacking cell for the column</a>,
-				find the first row with an unoccupied cell in that column.
-				That cell is now the <a>default stacking cell for the column</a>.
-
-				Set the item's row-start and column-start line indexes
-				to the column and row position of the <a title="default stacking cell for the column">default stacking cell for the start-most column of the item's position</a>.
-
-			: If the item has an <a>automatic grid position</a> in both axes:
-			:: Set the item's row-start and column-start line indexes
-				to the column and row position of the <a>default stacking cell</a>.
-
 
 <h2 id='alignment'>
 Alignment</h2>