[css-grid] Allow to place positioned grid items on the padding

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 390a4410d79de9baacadd9c36c8bf90a5fd4460c..d41cbb106b83581c22e23a24d18ca8de0d209abd 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
@@ -1493,30 +1493,28 @@ void LayoutGrid::offsetAndBreadthForPositionedChild(const LayoutBox& child, Grid
         breadth = (direction == ForColumns) ? clientLogicalWidth() : clientLogicalHeight();
         return;
     }
-    positions.translate(direction == ForColumns ? m_smallestColumnStart : m_smallestRowStart);
+    int smallestStart = abs(direction == ForColumns ? m_smallestColumnStart : m_smallestRowStart);

[svillar, 2016/01/19 12:04:51]

I'm starting to do

bool isRowAxis = direction == ForColumns

and then use it all along the code. I think we can do it here as well, as you're
anyway touching lines with that comparison.

[Manuel Rego, 2016/01/19 15:52:25]

Done.

+    int resolvedInitialPosition = positions.untranslatedResolvedInitialPosition() + smallestStart;
+    int resolvedFinalPosition = positions.untranslatedResolvedFinalPosition() + smallestStart;

[svillar, 2016/01/19 12:04:51]

This manual translation requires some explanation in a comment.

Also, as we're translating perhaps we should use size_t for those variables.

[Manuel Rego, 2016/01/19 15:52:25]

Added comment.
But that's precisely the issue, that for abspos items even after translated
we could have negative values, so we need to use ints.

 
     GridPosition startPosition = (direction == ForColumns) ? child.style()->gridColumnStart() : child.style()->gridRowStart();
     GridPosition endPosition = (direction == ForColumns) ? child.style()->gridColumnEnd() : child.style()->gridRowEnd();
-    size_t lastTrackIndex = (direction == ForColumns ? gridColumnCount() : gridRowCount()) - 1;
+    int lastTrackIndex = (direction == ForColumns ? gridColumnCount() : gridRowCount());

[svillar, 2016/01/19 12:04:51]

Perhaps we should use this change to rename this to lastExplicitTrackIndex in
order to make it clear that positioned items ignore implicit position

[Manuel Rego, 2016/01/19 15:52:25]

Done.

 
     bool startIsAuto = startPosition.isAuto()
         || (startPosition.isNamedGridArea() && !GridResolvedPosition::isValidNamedLineOrArea(startPosition.namedGridLine(), styleRef(), GridResolvedPosition::initialPositionSide(direction)))
-        || (positions.resolvedInitialPosition() > lastTrackIndex);
+        || (resolvedInitialPosition < 0)
+        || (resolvedInitialPosition > lastTrackIndex);
     bool endIsAuto = endPosition.isAuto()
         || (endPosition.isNamedGridArea() && !GridResolvedPosition::isValidNamedLineOrArea(endPosition.namedGridLine(), styleRef(), GridResolvedPosition::finalPositionSide(direction)))
-        || (positions.resolvedFinalPosition() - 1 > lastTrackIndex);
+        || (resolvedFinalPosition < 0)
+        || (resolvedFinalPosition > lastTrackIndex);
 
-    size_t firstPosition = 0;
-    size_t initialPosition = startIsAuto ? firstPosition : positions.resolvedInitialPosition();
-    size_t lastPosition = lastTrackIndex;
-    size_t finalPosition = endIsAuto ? lastPosition : positions.resolvedFinalPosition() - 1;
-
-    // Positioned children do not grow the grid, so we need to clamp the positions to avoid ending up outside of it.
-    initialPosition = std::min(initialPosition, lastPosition);
-    finalPosition = std::min(finalPosition, lastPosition);
+    size_t initialPosition = startIsAuto ? 0 : resolvedInitialPosition;
+    size_t finalPosition = endIsAuto ? lastTrackIndex : resolvedFinalPosition;
 
     LayoutUnit start = startIsAuto ? LayoutUnit() : (direction == ForColumns) ?  m_columnPositions[initialPosition] : m_rowPositions[initialPosition];
-    LayoutUnit end = endIsAuto ? (direction == ForColumns) ? logicalWidth() : logicalHeight() : (direction == ForColumns) ?  m_columnPositions[finalPosition + 1] : m_rowPositions[finalPosition + 1];
+    LayoutUnit end = endIsAuto ? (direction == ForColumns) ? logicalWidth() : logicalHeight() : (direction == ForColumns) ?  m_columnPositions[finalPosition] : m_rowPositions[finalPosition];

[jfernandez, 2016/01/18 17:57:42]

I'd simplify this line, if possible.

[Manuel Rego, 2016/01/19 15:52:25]

Now that we use isForColumns I think it's not that bad.
We could use if/else lines if needed.

 
     breadth = end - start;