chromium/third_party/blink/renderer/core/layout/table/table_borders.h

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_TABLE_TABLE_BORDERS_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_TABLE_TABLE_BORDERS_H_

#include <optional>

#include "base/check_op.h"
#include "base/dcheck_is_on.h"
#include "base/memory/scoped_refptr.h"
#include "base/notreached.h"
#include "third_party/blink/renderer/core/style/computed_style.h"
#include "third_party/blink/renderer/core/style/computed_style_constants.h"
#include "third_party/blink/renderer/platform/geometry/layout_unit.h"
#include "third_party/blink/renderer/platform/text/text_direction.h"
#include "third_party/blink/renderer/platform/text/writing_mode.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"

namespace blink {

class BlockNode;
class ComputedStyle;
struct BoxStrut;

// When table has collapsed borders, computing borders for table parts is
// complex, and costly.
// TableBorders precomputes collapsed borders. It exposes the API for
// border access. If borders are not collapsed, the API returns regular
// borders.
//
// TableBorders methods often take rowspan/colspan arguments.
// Rowspan must never be taller than the section.
// Colspan must never be wider than the table.
// To enforce this, TableBorders keeps track of section dimensions,
// and table's last column.
//
// Collapsed borders are stored as edges.
// Edges are stored in a 1D array. The array does not grow if borders are
// not set.
// Each edge represents a cell border.
// Mapping between edges and cells is best understood like this:
// - each cell stores only two edges, left edge, and a top edge.
// - cell's right edge is the left edge of the next cell.
// - cell's bottom edge is the top edge of the cell in the next row.
//
// To store all last row/col edges, an extra imaginary cell is used.
//
// A grid with R rows and C columns has |2 * (R+1) * (C+1)| edges.
// Example; R=1, C=3, 2*(1+1)*(3+1) = 16 edges.
// Edges 7, 9, 11, 13, 14, 15 are unused.
//
//     1    3   5   7
//   ------------------    <= edges for 3 cols X 1 row
//   |0  |2  |4   |6
//   |   |   |    |
//   ------------------
//   | 8 | 10| 12 | 14
//   |   |   |    |
//   |9  |11 |13  |15

class TableBorders : public GarbageCollected<TableBorders> { … };

}  // namespace blink

WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(…)
WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(…)

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_TABLE_TABLE_BORDERS_H_