FirstMeaningfulPaint UMA

third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.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 FirstMeaningfulPaintDetector_h
+#define FirstMeaningfulPaintDetector_h
+
+#include "core/CoreExport.h"
+#include "platform/Timer.h"
+#include "platform/heap/Handle.h"
+#include "wtf/Noncopyable.h"
+
+namespace blink {
+
+class Document;
+class PaintTiming;
+
+// FirstMeaningfulPaintDetector observes layout operations during page load
+// until network stable (2 seconds of no network activity), and computes the
+// layout-based First Meaningful Paint.
+// See https://goo.gl/vpaxv6 and http://goo.gl/TEiMi4 for more details.
+class CORE_EXPORT FirstMeaningfulPaintDetector : public GarbageCollectedFinalized<FirstMeaningfulPaintDetector> {

[Charlie Harrison, 2016/08/09 16:27:32]

Just to make sure: does this have to be finalized due to the
m_networkStableTimer?

[Kunihiko Sakamoto, 2016/08/10 02:33:32]

Yes.

+    WTF_MAKE_NONCOPYABLE(FirstMeaningfulPaintDetector);
+public:
+    class LayoutObjectCounter {

[Charlie Harrison, 2016/08/09 16:27:33]

Can you document this class and who should be using it?

[Kunihiko Sakamoto, 2016/08/10 02:33:32]

Done.

+    public:
+        void reset() { m_count = 0; }
+        void increment() { m_count++; }
+        unsigned count() const { return m_count; }
+    private:
+        unsigned m_count = 0;
+    };
+
+    static FirstMeaningfulPaintDetector& from(Document&);
+
+    FirstMeaningfulPaintDetector(PaintTiming*);
+    virtual ~FirstMeaningfulPaintDetector() { }
+
+    void computeLayoutSignificance(const LayoutObjectCounter&,
+        int contentsHeightBeforeLayout, int contentsHeightAfterLayout, int visibleHeight);
+    void notifyPaint();
+    void checkNetworkStable();
+
+    DECLARE_TRACE();
+
+private:
+    friend class FirstMeaningfulPaintDetectorTest;
+
+    Document* document();
+    void networkStableTimerFired(TimerBase*);
+
+    enum State { NextPaintIsNotMeaningful, NextPaintIsMeaningful, Reported };
+    State m_state = NextPaintIsNotMeaningful;
+
+    Member<PaintTiming> m_paintTiming;
+    double m_provisionalFirstMeaningfulPaint = 0.0;
+    double m_maxSignificanceSoFar = 0.0;
+    double m_accumulatedSignificanceWhileHavingBlankText = 0.0;
+    unsigned m_prevLayoutObjectCount = 0;
+    Timer<FirstMeaningfulPaintDetector> m_networkStableTimer;
+};
+
+} // namespace blink
+
+#endif