[css-grid] Fix row-locked auto-positioning to handle sparse vs. dense correctly..

Author: fantasai

css-grid/Overview.bs

@@ -2308,10 +2308,20 @@ Grid Item Placement Algorithm</h3>
 
 		For each <a>grid item</a> with a <a>definite row position</a>
 		(that is, the 'grid-row-start' and 'grid-row-end' properties define a <a>definite grid position</a>),
-		in <a>order-modified document order</a>,
-		set the row-start line of its <a>placement</a>
-		to the earliest (smallest positive index) line index
-		that ensures this item’s <a>grid area</a> will not overlap any <a>occupied</a> grid cells.
+		in <a>order-modified document order</a>:
+
+		: “sparse” packing (omitted ''dense'' keyword)
+		:: 
+			Set the row-start line of its <a>placement</a>
+			to the earliest (smallest positive index) line index
+			that ensures this item’s <a>grid area</a> will not overlap any <a>occupied</a> grid cells
+			and that is past any <a>grid items</a> previously placed in this row by this step.
+
+		: “dense” packing (''dense'' specified)
+		::
+			Set the row-start line of its <a>placement</a>
+			to the earliest (smallest positive index) line index
+			that ensures this item’s <a>grid area</a> will not overlap any <a>occupied</a> grid cells.
 
 	2. <b>Determine the number of columns in the implicit grid.</b>
 

css-grid/Overview.html

@@ -4395,12 +4395,41 @@ <h3 class="heading settled" data-level="9.5" id="auto-placement-algo"><span clas
 
           <p>For each <a data-link-type="dfn" href="#grid-item">grid item</a> with a <a data-link-type="dfn" href="#definite-grid-position">definite row position</a>
 (that is, the <a class="property" data-link-type="propdesc" href="#propdef-grid-row-start">grid-row-start</a> and <a class="property" data-link-type="propdesc" href="#propdef-grid-row-end">grid-row-end</a> properties define a <a data-link-type="dfn" href="#definite-grid-position">definite grid position</a>),
-in <a data-link-type="dfn" href="http://dev.w3.org/csswg/css-flexbox-1/#order-modified-document-order">order-modified document order</a>,
-set the row-start line of its <a data-link-type="dfn" href="#grid-placement">placement</a>
+in <a data-link-type="dfn" href="http://dev.w3.org/csswg/css-flexbox-1/#order-modified-document-order">order-modified document order</a>:</p>
+          
+
+
+          <dl>
+            <dt data-md="">
+              <p>“sparse” packing (omitted <a class="css" data-link-type="maybe" href="#valdef-grid-auto-flow-dense">dense</a> keyword)</p>
+              
+
+            </dt>
+            <dd data-md="">
+
+              <p>Set the row-start line of its <a data-link-type="dfn" href="#grid-placement">placement</a>
+to the earliest (smallest positive index) line index
+that ensures this item’s <a data-link-type="dfn" href="#grid-area">grid area</a> will not overlap any <a data-link-type="dfn" href="#occupied">occupied</a> grid cells
+and that is past any <a data-link-type="dfn" href="#grid-item">grid items</a> previously placed in this row by this step.</p>
+              
+
+
+            </dd>
+            <dt data-md="">
+              <p>“dense” packing (<a class="css" data-link-type="maybe" href="#valdef-grid-auto-flow-dense">dense</a> specified)</p>
+              
+
+            </dt>
+            <dd data-md="">
+
+              <p>Set the row-start line of its <a data-link-type="dfn" href="#grid-placement">placement</a>
 to the earliest (smallest positive index) line index
 that ensures this item’s <a data-link-type="dfn" href="#grid-area">grid area</a> will not overlap any <a data-link-type="dfn" href="#occupied">occupied</a> grid cells.</p>
-          
+              
 
+            </dd>
+          </dl>
+          
 
         </li>
         <li data-md="">