[LayoutNG] Add NGConstraintSpace class definition

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 NGDerivedConstraintSpace;
+class NGExclusion;
+class NGFragment;
+class NGLayoutOpportunityIterator;
+
+enum NGExclusionType {
+    ClearNone = 0,
+    ClearFloatLeft = 1,
+    ClearFloatRight = 2,
+    ClearFragment = 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 inlineSize, LayoutUnit blockSize);
+    ~NGConstraintSpace() { }
+
+    void addExclusion(const NGExclusion, unsigned options = 0);
+    void setOverflowSize(LayoutUnit inlineSize, LayoutUnit blockSize);
+    void setFixedSize(bool inlineFixed, bool blockFixed);
+    void setFragmentationType(NGFragmentationType blockFragmentationType);
+
+    // Available space in each direction, -1 indicates infinite space.
+    LayoutUnit inlineSize() const { return m_inlineSize; }
+    LayoutUnit blockSize() const { return m_blockSize; }
+
+    // The size threashold in the inline and block directions respectively that
+    // triggers the presence of a scrollbar. If exceeded the current layout
+    // should be aborted and invoked again with a constraint space modified to
+    // reserve space for a scrollbar. -1 indicates no limit.
+    LayoutUnit inlineOverflowSize() const { return m_inlineOverflowSize; }
+    LayoutUnit blockOverflowSize() const { return m_blockOverflowSize; }
+
+    // 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 = ClearNone,
+        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_inlineSize;
+    LayoutUnit m_blockSize;
+    LayoutUnit m_inlineOverflowSize;
+    LayoutUnit m_blockOverflowSize;
+
+    unsigned m_fixedInlineSize : 1;
+    unsigned m_fixedBlockSize : 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;
+
+    // When creating a derived NGConstraintSpace for the next inline level
+    // layout opportunity, inlineSize and blockSize of the NGConstraintSpace
+    // may be different from its parent. These properties hold the inline and
+    // block size of the original NGConstraintSpaces, allowing percentage
+    // resolution to work correctly.
+    LayoutUnit inlineSizeForPercentageResolution() const;
+    LayoutUnit blockSizeForPercentageResolution() const;
+
+private:
+    NGDerivedConstraintSpace();
+
+    LayoutUnit m_inlineOffset;
+    LayoutUnit m_blockOffset;
+    NGConstraintSpace* m_original;
+};
+
+} // namespace blink
+
+#endif // NGConstraintSpace_h