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// Copyright 2016 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 NGLayoutAlgorithm_h
#define NGLayoutAlgorithm_h
#include "base/optional.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/layout/min_max_size.h"
#include "third_party/blink/renderer/core/layout/ng/ng_constraint_space.h"
#include "third_party/blink/renderer/platform/wtf/allocator.h"
namespace blink {
class ComputedStyle;
class NGLayoutResult;
struct MinMaxSizeInput;
// Base class for all LayoutNG algorithms.
template <typename NGInputNodeType,
typename NGBoxFragmentBuilderType,
typename NGBreakTokenType>
class CORE_EXPORT NGLayoutAlgorithm {
NGLayoutAlgorithm(NGInputNodeType node,
scoped_refptr<const ComputedStyle> style,
const NGConstraintSpace& space,
TextDirection direction,
const NGBreakTokenType* break_token)
: node_(node),
container_builder_(node, style, space.GetWritingMode(), direction) {}
NGLayoutAlgorithm(NGInputNodeType node,
const NGConstraintSpace& space,
const NGBreakTokenType* break_token)
: NGLayoutAlgorithm(node,
break_token) {}
virtual ~NGLayoutAlgorithm() = default;
// Actual layout function. Lays out the children and descendants within the
// constraints given by the NGConstraintSpace. Returns a layout result with
// the resulting layout information.
// TODO(layout-dev): attempt to make this function const.
virtual scoped_refptr<NGLayoutResult> Layout() = 0;
// Computes the min-content and max-content intrinsic sizes for the given box.
// The result will not take any min-width, max-width or width properties into
// account. If the return value is empty, the caller is expected to synthesize
// this value from the overflow rect returned from Layout called with an
// available width of 0 and LayoutUnit::max(), respectively.
virtual base::Optional<MinMaxSize> ComputeMinMaxSize(
const MinMaxSizeInput&) const {
return base::nullopt;
const NGConstraintSpace& ConstraintSpace() const { return constraint_space_; }
const ComputedStyle& Style() const { return node_.Style(); }
NGBfcOffset ContainerBfcOffset() const {
return {container_builder_.BfcLineOffset(),
NGInputNodeType Node() const { return node_; }
const NGBreakTokenType* BreakToken() const { return break_token_.get(); }
NGInputNodeType node_;
const NGConstraintSpace& constraint_space_;
// The break token from which we are currently resuming layout.
scoped_refptr<const NGBreakTokenType> break_token_;
NGBoxFragmentBuilderType container_builder_;
} // namespace blink
#endif // NGLayoutAlgorithm_h