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// Copyright 2015 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 THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_FRAGMENTATION_CONTEXT_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_FRAGMENTATION_CONTEXT_H_
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/geometry/layout_size.h"
#include "third_party/blink/renderer/platform/geometry/layout_unit.h"
namespace blink {
// A fragmentation context is either established by a multicol container, or by
// pages when printing. A fragmentation context consists of a series of
// fragmentainers. A fragmentainer is simply a column or page, depending on the
// type of fragmentation context. [1]
//
// A couple of methods here take a |blockOffset| parameter. This is the offset
// from the start of the fragmentation context, pretending that everything is
// laid out in one single strip (and not sliced into pages or columns).
// In multicol, this is referred to as the flow thread coordinate space.
//
// It should be noted that a multicol container may be nested inside another
// fragmentation context (another multicol container, or the pages when
// printing), although this class doesn't deal with that (it's internal to the
// multicol implementation).
//
// [1] http://www.w3.org/TR/css3-break/#fragmentation-model
class CORE_EXPORT FragmentationContext {
public:
virtual ~FragmentationContext() = default;
// The height of the fragmentainers may depend on the total height of the
// contents (column balancing), in which case false is returned if we haven't
// laid out yet. Otherwise, true is returned.
virtual bool IsFragmentainerLogicalHeightKnown() = 0;
// Return the height of the fragmentainer at the specified offset. The
// fragmentainer height isn't necessarily uniform all across the
// fragmentation context. This method may only be called if the logical
// height has been calculated, i.e. if IsFragmentainerLogicalHeightKnown()
// returns true.
virtual LayoutUnit FragmentainerLogicalHeightAt(LayoutUnit block_offset) = 0;
// Return how much is left of the fragmentainer at the specified offset.
// Callers typically want this information to decide whether some piece of
// content fits in this fragmentainer, or if it has to push the content to the
// next fragmentainer.
virtual LayoutUnit RemainingLogicalHeightAt(LayoutUnit block_offset) = 0;
// Return the flow thread of the fragmentation context, if it is a multicol
// fragmentation context. Since multicol containers may be nested inside other
// fragmentation contexts, sometimes we need to know if it's a multicol
// container that we're dealing with.
virtual class LayoutMultiColumnFlowThread* AssociatedFlowThread() {
return nullptr;
}
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_FRAGMENTATION_CONTEXT_H_
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