[CSS Grid Layout] Support for justify-items property.

Source/core/rendering/RenderGrid.cpp

Index: Source/core/rendering/RenderGrid.cpp
diff --git a/Source/core/rendering/RenderGrid.cpp b/Source/core/rendering/RenderGrid.cpp
index f58fb1c46d4fdbebf7c5c97d0b7f853f663a2288..9d8c2be583bb75382e28a4cf63de4ac629d017bf 100644
--- a/Source/core/rendering/RenderGrid.cpp
+++ b/Source/core/rendering/RenderGrid.cpp
@@ -1118,28 +1118,44 @@ LayoutUnit RenderGrid::centeredColumnPositionForChild(const RenderBox* child) co
     return columnPosition + std::max<LayoutUnit>(0, endOfColumn - startOfColumn - child->logicalWidth()) / 2;
 }
 
+static ItemPosition resolveJustification(const RenderStyle* parentStyle, const RenderStyle* childStyle)
+{
+    ItemPosition justify = childStyle->justifySelf();
+    if (justify == ItemPositionAuto)
+        justify = (parentStyle->justifyItems() == ItemPositionAuto) ? ItemPositionStretch : parentStyle->justifyItems();
+
+    return justify;
+}
+
 LayoutUnit RenderGrid::columnPositionForChild(const RenderBox* child) const
 {
-    ItemPosition childJustifySelf = child->style()->justifySelf();
-    switch (childJustifySelf) {
+    bool hasOrthogonalWritingMode = child->isHorizontalWritingMode() != isHorizontalWritingMode();
+    ItemPosition justifySelf = resolveJustification(style(), child->style());
+
+    switch (justifySelf) {

[Julien - ping for review, 2014/08/22 21:22:14]

Unneeded variable:

switch(resolveJustification(style(), child->style()) {

[jfernandez, 2014/08/26 11:23:13]

Done.

     case ItemPositionSelfStart:
+        // If orthogonal writing-modes, this computes to 'Start'.

[Julien - ping for review, 2014/08/22 21:22:14]

'start' (lowercase s) to match the specification.

Nit: This reads better for me but you may disagree -> For orthogonal
writing-modes, this computes to 'start'

[jfernandez, 2014/08/26 11:23:13]

Done.

+        // FIXME: grid track sizing and positioning does not support orthogonal modes yet.

[Julien - ping for review, 2014/08/22 21:22:14]

grid track sizing and position *do* not support (it's plural :))

[jfernandez, 2014/08/26 11:23:13]

Done.

+        if (hasOrthogonalWritingMode)
+            return columnPositionAlignedWithGridContainerStart(child);
+
         // self-start is based on the child's direction. That's why we need to check against the grid container's direction.
         if (child->style()->direction() != style()->direction())
             return columnPositionAlignedWithGridContainerEnd(child);
 
         return columnPositionAlignedWithGridContainerStart(child);
     case ItemPositionSelfEnd:
+        // If orthogonal writing-modes, this computes to 'Start'.
+        // FIXME: grid track sizing and positioning does not support orthogonal modes yet.

[Julien - ping for review, 2014/08/22 21:22:14]

Same comments.

[jfernandez, 2014/08/26 11:23:13]

Done.

+        if (hasOrthogonalWritingMode)
+            return columnPositionAlignedWithGridContainerEnd(child);
+
         // self-end is based on the child's direction. That's why we need to check against the grid container's direction.
         if (child->style()->direction() != style()->direction())
             return columnPositionAlignedWithGridContainerStart(child);
 
         return columnPositionAlignedWithGridContainerEnd(child);
 
-    case ItemPositionFlexStart:
-    case ItemPositionFlexEnd:
-        // Only used in flex layout, for other layout, it's equivalent to 'start'.
-        return columnPositionAlignedWithGridContainerStart(child);

[Julien - ping for review, 2014/08/22 21:22:14]

Unneeded change. We can agree / disagree over which format is more readable but
this touches the history for no good reason.

[jfernandez, 2014/08/26 11:23:13]

Acknowledged.

-
     case ItemPositionLeft:
         // If the property's axis is not parallel with the inline axis, this is equivalent to ‘start’.
         if (!isHorizontalWritingMode())
@@ -1161,12 +1177,17 @@ LayoutUnit RenderGrid::columnPositionForChild(const RenderBox* child) const
 
     case ItemPositionCenter:
         return centeredColumnPositionForChild(child);
+        // Only used in flex layout, for other layout, it's equivalent to 'start'.
+    case ItemPositionFlexStart:
     case ItemPositionStart:
         return columnPositionAlignedWithGridContainerStart(child);
+        // Only used in flex layout, for other layout, it's equivalent to 'start'.
+    case ItemPositionFlexEnd:
     case ItemPositionEnd:
         return columnPositionAlignedWithGridContainerEnd(child);
 
     case ItemPositionAuto:
+        break;

[Julien - ping for review, 2014/08/22 21:22:14]

ASSERT_NOT_REACHED();

[jfernandez, 2014/08/26 11:23:13]

There is such ASSERT at the end of the function, which is also used by the
"default" case. 

     case ItemPositionStretch:
     case ItemPositionBaseline:
     case ItemPositionLastBaseline: