third_party/WebKit/Source/core/layout/PaintInvalidationState.h

// Copyright 2014 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 PaintInvalidationState_h
#define PaintInvalidationState_h

#include "core/CoreExport.h"
#include "core/paint/PaintInvalidator.h"
#include "platform/geometry/LayoutRect.h"
#include "platform/graphics/PaintInvalidationReason.h"
#include "platform/transforms/AffineTransform.h"
#include "wtf/Allocator.h"
#include "wtf/Noncopyable.h"

namespace blink {

class LayoutBoxModelObject;
class LayoutObject;
class LayoutSVGModelObject;
class LayoutView;
class PaintLayer;

enum VisualRectFlags { DefaultVisualRectFlags = 0, EdgeInclusive = 1 };

// PaintInvalidationState is an optimization used during the paint
// invalidation phase.
//
// This class is extremely close to LayoutState so see the documentation
// of LayoutState for the class existence and performance benefits.
//
// The main difference with LayoutState is that it was customized for the
// needs of the paint invalidation systems (keeping visual rectangles
// instead of layout specific information).
//
// See Source/core/paint/README.md#Paint-invalidation for more details.

class CORE_EXPORT PaintInvalidationState {
  DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
  WTF_MAKE_NONCOPYABLE(PaintInvalidationState);

 public:
  PaintInvalidationState(const PaintInvalidationState& parentState,
                         const LayoutObject&);

  // For root LayoutView, or when sub-frame LayoutView's
  // invalidateTreeIfNeeded() is called directly from
  // FrameView::invalidateTreeIfNeededRecursive() instead of the owner
  // LayoutPart.
  // TODO(wangxianzhu): Eliminate the latter case.
  PaintInvalidationState(
      const LayoutView&,
      Vector<const LayoutObject*>& pendingDelayedPaintInvalidations);

  // When a PaintInvalidationState is constructed, it can be used to map
  // points/rects in the object's local space (border box space for
  // LayoutBoxes). After invalidation of the current object, before invalidation
  // of the subtrees, this method must be called to apply clip and scroll offset
  // etc. for creating child PaintInvalidationStates.
  void updateForChildren(PaintInvalidationReason);

  bool hasForcedSubtreeInvalidationFlags() const {
    return m_forcedSubtreeInvalidationFlags;
  }

  bool forcedSubtreeInvalidationCheckingWithinContainer() const {
    return m_forcedSubtreeInvalidationFlags &
           PaintInvalidatorContext::ForcedSubtreeInvalidationChecking;
  }
  void setForceSubtreeInvalidationCheckingWithinContainer() {
    m_forcedSubtreeInvalidationFlags |=
        PaintInvalidatorContext::ForcedSubtreeInvalidationChecking;
  }

  bool forcedSubtreeFullInvalidationWithinContainer() const {
    return m_forcedSubtreeInvalidationFlags &
           PaintInvalidatorContext::ForcedSubtreeFullInvalidation;
  }

  bool forcedSubtreeInvalidationRectUpdateWithinContainerOnly() const {
    return m_forcedSubtreeInvalidationFlags ==
           PaintInvalidatorContext::ForcedSubtreeInvalidationRectUpdate;
  }
  void setForceSubtreeInvalidationRectUpdateWithinContainer() {
    m_forcedSubtreeInvalidationFlags |=
        PaintInvalidatorContext::ForcedSubtreeInvalidationRectUpdate;
  }

  const LayoutBoxModelObject& paintInvalidationContainer() const {
    return *m_paintInvalidationContainer;
  }

  // Computes the position of the current object ((0,0) in the space of the
  // object) in the space of paint invalidation backing.
  LayoutPoint computePositionFromPaintInvalidationBacking() const;

  // Returns the rect bounds needed to invalidate paint of this object,
  // in the space of paint invalidation backing.
  LayoutRect computePaintInvalidationRectInBacking() const;

  void mapLocalRectToPaintInvalidationBacking(LayoutRect&) const;

  PaintLayer& paintingLayer() const;

  const LayoutObject& currentObject() const { return m_currentObject; }

 private:
  friend class VisualRectMappingTest;
  friend class PaintInvalidatorContextAdapter;

  void mapLocalRectToPaintInvalidationContainer(LayoutRect&) const;

  void updateForCurrentObject(const PaintInvalidationState& parentState);
  void updateForNormalChildren();

  LayoutRect computePaintInvalidationRectInBackingForSVG() const;

  void addClipRectRelativeToPaintOffset(const LayoutRect& localClipRect);

  const LayoutObject& m_currentObject;

  unsigned m_forcedSubtreeInvalidationFlags;

  bool m_clipped;
  bool m_clippedForAbsolutePosition;

  // Clip rect from paintInvalidationContainer if m_cachedOffsetsEnabled is
  // true.
  LayoutRect m_clipRect;
  LayoutRect m_clipRectForAbsolutePosition;

  // x/y offset from the paintInvalidationContainer if m_cachedOffsetsEnabled is
  // true.
  // It includes relative positioning and scroll offsets.
  LayoutSize m_paintOffset;
  LayoutSize m_paintOffsetForAbsolutePosition;

  // Whether m_paintOffset[XXX] and m_clipRect[XXX] are valid and can be used
  // to map a rect from space of the current object to space of
  // paintInvalidationContainer.
  bool m_cachedOffsetsEnabled;
  bool m_cachedOffsetsForAbsolutePositionEnabled;

  // The following two fields are never null. Declare them as pointers because
  // we need some logic to initialize them in the body of the constructor.

  // The current paint invalidation container for normal flow objects.
  // It is the enclosing composited object.
  const LayoutBoxModelObject* m_paintInvalidationContainer;

  // The current paint invalidation container for stacked contents (stacking
  // contexts or positioned objects).  It is the nearest ancestor composited
  // object which establishes a stacking context.  See
  // Source/core/paint/README.md ### PaintInvalidationState for details on how
  // stacked contents' paint invalidation containers differ.
  const LayoutBoxModelObject* m_paintInvalidationContainerForStackedContents;

  const LayoutObject& m_containerForAbsolutePosition;

  // Transform from the initial viewport coordinate system of an outermost
  // SVG root to the userspace _before_ the relevant element. Combining this
  // with |m_paintOffset| yields the "final" offset.
  AffineTransform m_svgTransform;

  // Records objects needing paint invalidation on the next frame. See the
  // definition of PaintInvalidationDelayedFull for more details.
  Vector<const LayoutObject*>& m_pendingDelayedPaintInvalidations;

  PaintLayer& m_paintingLayer;

#if ENABLE(ASSERT)
  bool m_didUpdateForChildren;
#endif

#if ENABLE(ASSERT) && !defined(NDEBUG)
// #define CHECK_FAST_PATH_SLOW_PATH_EQUALITY
#endif

#ifdef CHECK_FAST_PATH_SLOW_PATH_EQUALITY
  void assertFastPathAndSlowPathRectsEqual(
      const LayoutRect& fastPathRect,
      const LayoutRect& slowPathRect) const;
  bool m_canCheckFastPathSlowPathEquality;
#endif
};

// This is temporary to adapt legacy PaintInvalidationState to
// PaintInvalidatorContext
class PaintInvalidatorContextAdapter : public PaintInvalidatorContext {
 public:
  PaintInvalidatorContextAdapter(const PaintInvalidationState&);
  void mapLocalRectToPaintInvalidationBacking(const LayoutObject&,
                                              LayoutRect&) const override;

 private:
  const PaintInvalidationState& m_paintInvalidationState;
};

}  // namespace blink

#endif  // PaintInvalidationState_h