[css-grid] Use grid area position to determine overflowing items

third_party/WebKit/Source/core/layout/LayoutGrid.cpp

Index: third_party/WebKit/Source/core/layout/LayoutGrid.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
index ec13d1934a0da3df498bbfaa44792491e7bfb277..55aae691e41cad51e701c5dd337b925f37c6be01 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
@@ -1922,8 +1922,8 @@ void LayoutGrid::layoutGridItems(GridSizingData& sizingData)
         updateAutoMarginsInColumnAxisIfNeeded(*child);
         updateAutoMarginsInRowAxisIfNeeded(*child);
 
-#if ENABLE(ASSERT)
         const GridArea& area = cachedGridArea(*child);
+#if ENABLE(ASSERT)
         ASSERT(area.columns.startLine() < sizingData.columnTracks.size());
         ASSERT(area.rows.startLine() < sizingData.rowTracks.size());
 #endif
@@ -1934,7 +1934,8 @@ void LayoutGrid::layoutGridItems(GridSizingData& sizingData)
         // TODO (lajava): Child's margins should account when evaluating whether it overflows its grid area (http://crbug.com/628155).

[jfernandez, 2016/09/19 18:01:24]

Remove the TODO, please.

[svillar, 2016/09/20 11:12:46]

Acknowledged.

         LayoutUnit childGridAreaHeight = isHorizontalWritingMode() ? overrideContainingBlockContentLogicalHeight : overrideContainingBlockContentLogicalWidth;
         LayoutUnit childGridAreaWidth = isHorizontalWritingMode() ? overrideContainingBlockContentLogicalWidth : overrideContainingBlockContentLogicalHeight;
-        if (child->size().height() > childGridAreaHeight || child->size().width() > childGridAreaWidth)
+        LayoutRect gridAreaRect(gridAreaLogicalPosition(area), LayoutSize(childGridAreaWidth, childGridAreaHeight));
+        if (!gridAreaRect.contains(child->frameRect()))

[jfernandez, 2016/09/19 18:01:24]

Using FrameRect should be the same than doing operations with height()(width(),
like in the old code. I don't understand why this is solving the issue.
Additionally, wouldn't we take into account the box-sizing property ?  

[svillar, 2016/09/20 11:12:47]

The main difference are not the sizes indeed, but the location of the grid area
vs the location of the child.

             m_gridItemsOverflowingGridArea.append(child);
     }
 }
@@ -2661,6 +2662,16 @@ LayoutPoint LayoutGrid::findChildLogicalPosition(const LayoutBox& child, GridSiz
     return isOrthogonalChild(child) ? childLocation.transposedPoint() : childLocation;
 }
 
+LayoutPoint LayoutGrid::gridAreaLogicalPosition(const GridArea& area) const
+{
+    LayoutUnit columnAxisOffset = m_rowPositions[area.rows.startLine()];
+    LayoutUnit rowAxisOffset = m_columnPositions[area.columns.startLine()];
+
+    // See comment in findChildLogicalPosition() about why we need sometimes to translate from RTL
+    // to LTR the rowAxisOffset coordinate.
+    return LayoutPoint(style()->isLeftToRightDirection() ? rowAxisOffset : translateRTLCoordinate(rowAxisOffset), columnAxisOffset);
+}
+
 void LayoutGrid::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& paintOffset) const
 {
     if (!m_gridItemArea.isEmpty())