Extract LayoutTableSection::CellStruct to a standalone class TableGridCell

third_party/WebKit/Source/core/layout/TableGridCell.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TableGridCell_h
+#define TableGridCell_h
+
+#include "platform/wtf/Allocator.h"
+#include "platform/wtf/Vector.h"
+
+namespace blink {
+
+class LayoutTableCell;
+
+// TableGridCell represents a single unit in the table grid.
+// - Without rowspan and colspan, TableGridCells and LayoutTableCells have 1:1
+//   relationship.
+// - A LayoutTableCell spanning multiple rows or effective columns can cover
+//   multiple TableGridCells.
+// - Multiple LayoutTableCells can span into the same TableGridCell, e.g.
+//    <tr><td>A</td><td rowspan="2">B</td></tr>
+//    <tr><td colspan="2">C></td></tr>
+//   both LayoutTableCell B and C cover the TableGridCell at (1,1).
+
+class TableGridCell {
+  DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
+
+ public:
+  // We can't inline the constructor and destructor because cells_ needs full
+  // definition of LayoutTableCell, and we can't include LayoutTableCell.h
+  // from this file due to circular includes.
+  TableGridCell();
+  ~TableGridCell();
+
+  // This is the LayoutTableCell covering this TableGridCell that is on top of
+  // the others (aka the last LayoutTableCell in DOM order for this
+  // TableGridCell).
+  //
+  // The concept of a primary cell is dubious at most as it doesn't correspond
+  // to a DOM or rendering concept. Also callers should be careful about
+  // assumptions about it. For example, even though the primary cell is visibly
+  // the top most, it is not guaranteed to be the only one visible for this
+  // unit due to different visual overflow rectangles.
+  LayoutTableCell* PrimaryCell() {
+    return HasCells() ? cells_.back() : nullptr;
+  }
+  const LayoutTableCell* PrimaryCell() const {
+    return const_cast<TableGridCell*>(this)->PrimaryCell();
+  }
+
+  bool HasCells() const { return cells_.size() > 0; }
+
+  Vector<LayoutTableCell*, 1>& Cells() { return cells_; }
+  const Vector<LayoutTableCell*, 1>& Cells() const { return cells_; }
+
+  bool InColSpan() const { return in_col_span_; }
+  void SetInColSpan(bool in_col_span) { in_col_span_ = in_col_span; }
+
+ private:
+  // All LayoutTableCells covering this TableGridCell.
+  // Due to colspan / rowpsan, it is possible to have overlapping cells
+  // (see class comment about an example).
+  // This Vector is sorted in DOM order.
+  Vector<LayoutTableCell*, 1> cells_;
+
+  // True for columns after the first in a colspan.
+  bool in_col_span_ = false;
+};
+
+}  // namespace blink
+
+#endif  // TableGridCell_h