chromium/third_party/blink/renderer/core/layout/layout_multi_column_set.h

/*
 * Copyright (C) 2012 Apple Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_LAYOUT_MULTI_COLUMN_SET_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_LAYOUT_MULTI_COLUMN_SET_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/layout/layout_multi_column_flow_thread.h"
#include "third_party/blink/renderer/core/layout/multi_column_fragmentainer_group.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"

namespace blink {

// A set of columns in a multicol container. A column set is inserted as an
// anonymous child of the actual multicol container (i.e. the layoutObject whose
// style computes to non-auto column-count and/or column-width), next to the
// flow thread. There'll be one column set for each contiguous run of column
// content. The only thing that can interrupt a contiguous run of column content
// is a column spanner, which means that if there are no spanners, there'll
// only be one column set.
//
// Since a spanner interrupts an otherwise contiguous run of column content,
// inserting one may result in the creation of additional new column sets. A
// placeholder for the spanning layoutObject has to be placed in between the
// column sets that come before and after the spanner, if there's actually
// column content both before and after the spanner.
//
// A column set has no children on its own, but is merely used to slice a
// portion of the tall "single-column" flow thread into actual columns visually,
// to convert from flow thread coordinates to visual ones. It is in charge of
// both positioning columns correctly relatively to the parent multicol
// container, and to calculate the correct translation for each column's
// contents, and to paint any rules between them. LayoutMultiColumnSet objects
// are used for painting, hit testing, and any other type of operation that
// requires mapping from flow thread coordinates to visual coordinates.
//
// Columns are normally laid out in the inline progression direction, but if the
// multicol container is inside another fragmentation context (e.g. paged media,
// or an another multicol container), we may need to group the columns, so
// that we get one MultiColumnFragmentainerGroup for each outer fragmentainer
// (page / column) that the inner multicol container lives in. Each
// fragmentainer group has its own column height, but the column height is
// uniform within a group.
class CORE_EXPORT LayoutMultiColumnSet final : public LayoutBlockFlow { … };

template <>
struct DowncastTraits<LayoutMultiColumnSet> { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_LAYOUT_MULTI_COLUMN_SET_H_