File: LayoutAnalyzer.h

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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 LayoutAnalyzer_h
#define LayoutAnalyzer_h

#include "platform/LayoutUnit.h"
#include "wtf/Allocator.h"
#include "wtf/Noncopyable.h"
#include <memory>

namespace blink {

class LayoutBlock;
class LayoutObject;
class TracedValue;

// Observes the performance of layout and reports statistics via a TracedValue.
// Usage:
// LayoutAnalyzer::Scope analyzer(*this);
class LayoutAnalyzer {
  USING_FAST_MALLOC(LayoutAnalyzer);
  WTF_MAKE_NONCOPYABLE(LayoutAnalyzer);

 public:
  enum Counter {
    LayoutBlockWidthChanged,
    LayoutBlockHeightChanged,
    LayoutBlockSizeChanged,
    LayoutBlockSizeDidNotChange,
    LayoutObjectsThatSpecifyColumns,
    LayoutAnalyzerStackMaximumDepth,
    LayoutObjectsThatAreFloating,
    LayoutObjectsThatHaveALayer,
    LayoutInlineObjectsThatAlwaysCreateLineBoxes,
    LayoutObjectsThatHadNeverHadLayout,
    LayoutObjectsThatAreOutOfFlowPositioned,
    LayoutObjectsThatNeedPositionedMovementLayout,
    PerformLayoutRootLayoutObjects,
    LayoutObjectsThatNeedLayoutForThemselves,
    LayoutObjectsThatNeedSimplifiedLayout,
    LayoutObjectsThatAreTableCells,
    LayoutObjectsThatAreTextAndCanNotUseTheSimpleFontCodePath,
    CharactersInLayoutObjectsThatAreTextAndCanNotUseTheSimpleFontCodePath,
    LayoutObjectsThatAreTextAndCanUseTheSimpleFontCodePath,
    CharactersInLayoutObjectsThatAreTextAndCanUseTheSimpleFontCodePath,
    TotalLayoutObjectsThatWereLaidOut,
  };
  static const size_t NumCounters = 21;

  class Scope {
    STACK_ALLOCATED();

   public:
    explicit Scope(const LayoutObject&);
    ~Scope();

   private:
    const LayoutObject& m_layoutObject;
    LayoutAnalyzer* m_analyzer;
  };

  class BlockScope {
    STACK_ALLOCATED();

   public:
    explicit BlockScope(const LayoutBlock&);
    ~BlockScope();

   private:
    const LayoutBlock& m_block;
    LayoutUnit m_width;
    LayoutUnit m_height;
  };

  LayoutAnalyzer() {}

  void reset();
  void push(const LayoutObject&);
  void pop(const LayoutObject&);

  void increment(Counter counter, unsigned delta = 1) {
    m_counters[counter] += delta;
  }

  std::unique_ptr<TracedValue> toTracedValue();

 private:
  const char* nameForCounter(Counter) const;

  double m_startMs;
  unsigned m_depth;
  unsigned m_counters[NumCounters];
};

}  // namespace blink

#endif  // LayoutAnalyzer_h