[LayoutNG] A different approach to multi-col.

third_party/WebKit/Source/core/layout/ng/ng_multi_column_layout_algorithm.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 NGMultiColumnLayoutAlgorithm_h
+#define NGMultiColumnLayoutAlgorithm_h
+
+#include "core/CoreExport.h"
+#include "core/layout/ng/ng_block_node.h"
+#include "core/layout/ng/ng_break_token.h"
+#include "core/layout/ng/ng_constraint_space_builder.h"
+#include "core/layout/ng/ng_fragment_builder.h"
+#include "core/layout/ng/ng_layout_algorithm.h"
+
+namespace blink {
+
+class ComputedStyle;
+class NGConstraintSpace;
+class NGConstraintSpaceBuilder;
+
+// A class for general block layout (e.g. a <div> with no special style).
+// Lays out the children in sequence.
+class CORE_EXPORT NGMultiColumnLayoutAlgorithm : public NGLayoutAlgorithm {
+ public:
+  // Default constructor.
+  // @param layout_object The layout object associated with this block.
+  // @param style Style reference of the block that is being laid out.
+  // @param first_child Our first child; the algorithm will use its NextSibling
+  //                    method to access all the children.
+  // @param space The constraint space which the algorithm should generate a
+  //              fragment within.
+  NGMultiColumnLayoutAlgorithm(NGBlockNode* node,
+                               NGConstraintSpace* space,
+                               NGBreakToken* break_token = nullptr);
+
+  RefPtr<NGLayoutResult> Layout() override;
+  Optional<MinMaxContentSize> ComputeMinMaxContentSize() const override;
+
+ private:
+  const NGConstraintSpace& ConstraintSpace() const {
+    DCHECK(constraint_space_);
+    return *constraint_space_;
+  }
+
+  const ComputedStyle& Style() const { return node_->Style(); }
+
+  Persistent<NGBlockNode> node_;
+  NGConstraintSpace* constraint_space_;
+
+  // The break token from which we are currently resuming layout.
+  NGBreakToken* break_token_;
+
+  NGFragmentBuilder builder_;
+  NGConstraintSpaceBuilder space_builder_;
+
+  NGBoxStrut border_and_padding_;
+  LayoutUnit content_size_;
+  LayoutUnit max_inline_size_;
+};
+
+}  // namespace blink
+
+#endif  // NGBlockLayoutAlgorithm_h