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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 FragmentationContext_h
#define FragmentationContext_h
#include "core/CoreExport.h"
#include "platform/LayoutUnit.h"
#include "platform/geometry/LayoutSize.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() { }
// 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.
virtual LayoutUnit fragmentainerLogicalHeightAt(LayoutUnit blockOffset) = 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 blockOffset) = 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 // FragmentationContext_h
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