[CSS Grid Layout] Fix issues adding new items to grid

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 351881084b582f24de06651ade28f7fd5595239d..f37c4c1b58cf3a883d13040b6b679cd14c0ae530 100644
--- a/Source/core/rendering/RenderGrid.cpp
+++ b/Source/core/rendering/RenderGrid.cpp
@@ -191,20 +191,28 @@ void RenderGrid::addChild(RenderObject* newChild, RenderObject* beforeChild)
         return;
     }
 
+    if (style()->gridAutoFlow() != AutoFlowNone) {
+        // The grid needs to be recomputed as it might contain auto-placed items that will change their position.
+        dirtyGrid();
+        return;
+    }
+
     RenderBox* newChildBox = toRenderBox(newChild);
     OwnPtr<GridSpan> rowPositions = resolveGridPositionsFromStyle(newChildBox, ForRows);
     OwnPtr<GridSpan> columnPositions = resolveGridPositionsFromStyle(newChildBox, ForColumns);
     if (!rowPositions || !columnPositions) {
         // The new child requires the auto-placement algorithm to run so we need to recompute the grid fully.
         dirtyGrid();
-    } else {
-        if (gridRowCount() <= rowPositions->finalPositionIndex || gridColumnCount() <= columnPositions->finalPositionIndex) {
-            // FIXME: We could just insert the new child provided we had a primitive to arbitrarily grow the grid.
-            dirtyGrid();
-        } else {
-            insertItemIntoGrid(newChildBox, GridCoordinate(*rowPositions, *columnPositions));
-        }
+        return;
     }
+
+    // Grow grid if required.

[Julien - ping for review, 2014/03/21 18:27:19]

Maybe we could turn that into a better comment:

// Ensure that the grid is big enough to contain new grid item.

+    if (gridRowCount() <= rowPositions->finalPositionIndex)
+        growGrid(ForRows, rowPositions->finalPositionIndex - gridRowCount() + 1);
+    if (gridColumnCount() <= columnPositions->finalPositionIndex)
+        growGrid(ForColumns, columnPositions->finalPositionIndex - gridColumnCount() + 1);
+
+    insertItemIntoGrid(newChildBox, GridCoordinate(*rowPositions, *columnPositions));
 }
 
 void RenderGrid::removeChild(RenderObject* child)
@@ -709,16 +717,19 @@ bool RenderGrid::tracksAreWiderThanMinTrackBreadth(GridTrackSizingDirection dire
 }
 #endif
 
-void RenderGrid::growGrid(GridTrackSizingDirection direction)
+void RenderGrid::growGrid(GridTrackSizingDirection direction, size_t positions)

[Julien - ping for review, 2014/03/21 18:27:19]

How about we pass in the _maximum_ position we want the grid to be?

I think that would simplify the callers and not make this code worse. It is also
more aligned with what you expect of this API (you really don't care about the
delta size but about the maximum allowed position)

 {
+    ASSERT(positions >= 1);
+
     if (direction == ForColumns) {
         const size_t oldColumnSize = m_grid[0].size();
         for (size_t row = 0; row < m_grid.size(); ++row)
-            m_grid[row].grow(oldColumnSize + 1);
+            m_grid[row].grow(oldColumnSize + positions);
     } else {
         const size_t oldRowSize = m_grid.size();
-        m_grid.grow(oldRowSize + 1);
-        m_grid[oldRowSize].grow(m_grid[0].size());
+        m_grid.grow(oldRowSize + positions);
+        for (size_t row = oldRowSize; row < m_grid.size(); ++row)
+            m_grid[row].grow(m_grid[0].size());
     }
 }
 
@@ -824,7 +835,7 @@ void RenderGrid::placeSpecifiedMajorAxisItemsOnGrid(const Vector<RenderBox*>& au
             continue;
         }
 
-        growGrid(autoPlacementMinorAxisDirection());
+        growGrid(autoPlacementMinorAxisDirection(), 1);
         OwnPtr<GridCoordinate> emptyGridArea = iterator.nextEmptyGridArea();
         ASSERT(emptyGridArea);
         insertItemIntoGrid(autoGridItems[i], emptyGridArea->rows.initialPositionIndex, emptyGridArea->columns.initialPositionIndex);
@@ -863,7 +874,7 @@ void RenderGrid::placeAutoMajorAxisItemOnGrid(RenderBox* gridItem)
     // We didn't find an empty grid area so we need to create an extra major axis line and insert our gridItem in it.
     const size_t columnIndex = (autoPlacementMajorAxisDirection() == ForColumns) ? m_grid[0].size() : minorAxisIndex;
     const size_t rowIndex = (autoPlacementMajorAxisDirection() == ForColumns) ? minorAxisIndex : m_grid.size();
-    growGrid(autoPlacementMajorAxisDirection());
+    growGrid(autoPlacementMajorAxisDirection(), 1);
     insertItemIntoGrid(gridItem, rowIndex, columnIndex);
 }