third_party/WebKit/Source/core/layout/ng/NGConstraintSpace.h

// 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 NGConstraintSpace_h
#define NGConstraintSpace_h

#include "core/CoreExport.h"
#include "platform/LayoutUnit.h"
#include "wtf/DoublyLinkedList.h"

namespace blink {

class NGConstraintSpace;
class NGDerivedConstraintSpace;
class NGExclusion;
class NGFragment;
class NGLayoutOpportunityIterator;
class LayoutBox;

enum NGExclusionType {
    NGClearNone = 0,
    NGClearFloatLeft = 1,
    NGClearFloatRight = 2,
    NGClearFragment = 4
};

enum NGFragmentationType {
    FragmentNone,
    FragmentPage,
    FragmentColumn,
    FragmentRegion
};

enum NGExclusionFlowType {
    ExcludeNone,
    ExcludeInlineFlow,
    ExcludeInlineStart,
    ExcludeInlineEnd,
    ExcludeInlineBoth
};

class NGExclusion {
public:
    NGExclusion();
    ~NGExclusion() { }
};

class CORE_EXPORT NGConstraintSpace {
public:
    NGConstraintSpace(LayoutUnit inlineContainerSize,
        LayoutUnit blockContainerSize);
    ~NGConstraintSpace() { }

    // Constructs Layout NG constraint space from legacy layout object.
    static NGConstraintSpace fromLayoutObject(const LayoutBox&);

    void addExclusion(const NGExclusion, unsigned options = 0);
    void setOverflowTriggersScrollbar(bool inlineTriggers,
        bool blockTriggers);
    void setFixedSize(bool inlineFixed, bool blockFixed);
    void setFragmentationType(NGFragmentationType);

    // Size of the container in each direction. Used for the following
    // three cases:
    // 1) Percentage resolution.
    // 2) Resolving absolute positions of children.
    // 3) Defining the threashold that triggers the presence of a
    //    scrollbar. Only applies if the corresponding scrollbarTrigger
    //    flag has been set for the direction.
    LayoutUnit inlineContainerSize() const
    {
        return m_inlineContainerSize;
    }
    LayoutUnit blockContainerSize() const
    {
        return m_blockContainerSize;
    }

    // Whether exceeding the containerSize triggers the presence of a
    // scrollbar for the indicated direction.
    // If exceeded the current layout should be aborted and invoked again
    // with a constraint space modified to reserve space for a scrollbar.
    bool inlineTriggersScrollbar() const
    {
        return m_inlineTriggersScrollbar;
    }
    bool blockTriggersScrollbar() const
    {
        return m_blockTriggersScrollbar;
    }

    // Some layout modes “stretch” their children to a fixed size (e.g. flex,
    // grid). These flags represented whether a layout needs to produce a
    // fragment that satisfies a fixed constraint in the inline and block
    // direction respectively.
    bool fixedInlineSize() const { return m_fixedInlineSize; }
    bool fixedBlockSize() const { return m_fixedBlockSize; }

    // If specified a layout should produce a Fragment which fragments at the
    // blockSize if possible.
    NGFragmentationType blockFragmentationType() const
    {
        return static_cast<NGFragmentationType>(m_blockFragmentationType);
    }

    DoublyLinkedList<const NGExclusion> exclusions(unsigned options = 0) const;

    NGLayoutOpportunityIterator layoutOpportunities(
        unsigned clear = NGClearNone,
        NGExclusionFlowType avoid = ExcludeNone) const;

    // Modifies constraint space to account for a placed fragment. Depending on
    // the shape of the fragment this will either modify the inline or block
    // size, or add an exclusion.
    void subtract(const NGFragment);

private:
    LayoutUnit m_inlineContainerSize;
    LayoutUnit m_blockContainerSize;

    unsigned m_fixedInlineSize : 1;
    unsigned m_fixedBlockSize : 1;
    unsigned m_inlineTriggersScrollbar : 1;
    unsigned m_blockTriggersScrollbar : 1;
    unsigned m_blockFragmentationType : 2;

    DoublyLinkedList<const NGExclusion> m_exclusions;
};


class CORE_EXPORT NGLayoutOpportunityIterator final {
public:
    NGLayoutOpportunityIterator(const NGConstraintSpace* space,
        unsigned clear, NGExclusionFlowType avoid)
        : m_constraintSpace(space)
        , m_clear(clear)
        , m_avoid(avoid) { }
    ~NGLayoutOpportunityIterator() { }

    const NGDerivedConstraintSpace* next();

private:
    const NGConstraintSpace* m_constraintSpace;
    unsigned m_clear;
    NGExclusionFlowType m_avoid;
};


class CORE_EXPORT NGDerivedConstraintSpace final : NGConstraintSpace {
public:
    ~NGDerivedConstraintSpace();

    LayoutUnit inlineOffset() const;
    LayoutUnit blockOffset() const;
    LayoutUnit inlineSize() const;
    LayoutUnit blockSize() const;

private:
    NGDerivedConstraintSpace();

    LayoutUnit m_inlineOffset;
    LayoutUnit m_blockOffset;
    LayoutUnit m_inlineSize;
    LayoutUnit m_blockSize;
    NGConstraintSpace* m_original;
};

} // namespace blink

#endif // NGConstraintSpace_h