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/*
* Copyright (C) 2018 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
namespace WebCore {
// This class is used to detect when we are painting frequently so that - even in a painting model
// without display lists - we can build and cache portions of display lists and reuse them only when
// animating. Once we transition fully to display lists, we can probably just pull from the previous
// paint's display list if it is still around and get rid of this code.
class PaintFrequencyTracker {
WTF_MAKE_FAST_ALLOCATED;
public:
PaintFrequencyTracker() = default;
void begin(MonotonicTime timestamp)
{
static unsigned paintFrequencyPaintCountThreshold = 30;
static Seconds paintFrequencyTimePerFrameThreshold = 32_ms;
static Seconds paintFrequencySecondsIdleThreshold = 5_s;
// Start by assuming the paint frequency is low
m_paintFrequency = PaintFrequency::Low;
if (!m_firstPaintTime) {
// Handle the first time this method is called.
m_firstPaintTime = timestamp;
} else if (timestamp - m_lastPaintTime > paintFrequencySecondsIdleThreshold) {
// It has been 5 seconds since last time we draw this renderer. Reset the state
// of this object as if, we've just started tracking the paint frequency.
m_firstPaintTime = timestamp;
m_totalPaints = 0;
} else if (m_totalPaints >= paintFrequencyPaintCountThreshold && ((m_lastPaintTime - m_firstPaintTime) / m_totalPaints) <= paintFrequencyTimePerFrameThreshold) {
// Change the paint frequency to be high only if:
// - This renderer has been painted at least 30 times.
// - The frame rate to paint this renderer has been at least 31.25 FPS.
m_paintFrequency = PaintFrequency::High;
}
m_lastPaintTime = timestamp;
++m_totalPaints;
}
void end()
{
ASSERT(m_firstPaintTime);
ASSERT(m_firstPaintTime <= m_lastPaintTime);
}
bool paintingFrequently() const { return m_paintFrequency == PaintFrequency::High; }
private:
MonotonicTime m_firstPaintTime;
MonotonicTime m_lastPaintTime;
unsigned m_totalPaints { 0 };
enum class PaintFrequency : bool { Low, High };
PaintFrequency m_paintFrequency { PaintFrequency::Low };
};
class SinglePaintFrequencyTracking {
WTF_MAKE_FAST_ALLOCATED;
public:
SinglePaintFrequencyTracking(PaintFrequencyTracker& paintFrequencyTracker, MonotonicTime timestamp)
: m_paintFrequencyTracker(paintFrequencyTracker)
{
m_paintFrequencyTracker.begin(timestamp ? timestamp : MonotonicTime::now());
}
~SinglePaintFrequencyTracking()
{
m_paintFrequencyTracker.end();
}
private:
PaintFrequencyTracker& m_paintFrequencyTracker;
};
}