Source/modules/device_orientation/DeviceSensorEventDispatcher.cpp

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
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 *
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 * notice, this list of conditions and the following disclaimer.
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 * in the documentation and/or other materials provided with the
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#include "config.h"
#include "modules/device_orientation/DeviceSensorEventDispatcher.h"

namespace WebCore {

DeviceSensorEventDispatcher::DeviceSensorEventDispatcher()
    : m_needsPurge(false)
    , m_isDispatching(false)
{
}

DeviceSensorEventDispatcher::~DeviceSensorEventDispatcher()
{
}

void DeviceSensorEventDispatcher::addController(DeviceSensorEventController* controller)
{
    bool wasEmpty = m_controllers.isEmpty();
    if (!m_controllers.contains(controller))
        m_controllers.append(controller);
    if (wasEmpty)
        startListening();
}

void DeviceSensorEventDispatcher::removeController(DeviceSensorEventController* controller)
{
    // Do not actually remove the controller from the vector, instead zero them out.
    // The zeros are removed in these two cases:
    // 1. either immediately if we are not dispatching any events,
    // 2. or after didChangeDeviceMotion/Orientation has dispatched all events.
    // This is to correctly handle the re-entrancy case when a controller is destroyed
    // while in the didChangeDeviceMotion/Orientation method.
    size_t index = m_controllers.find(controller);
    if (index == kNotFound)
        return;

    m_controllers[index] = 0;
    m_needsPurge = true;

    if (!m_isDispatching)
        purgeControllers();
}

void DeviceSensorEventDispatcher::purgeControllers()
{
    ASSERT(m_needsPurge);

    size_t i = 0;
    while (i < m_controllers.size()) {
        if (!m_controllers[i]) {
            m_controllers[i] = m_controllers.last();
            m_controllers.removeLast();
        } else {
            ++i;
        }
    }

    m_needsPurge = false;

    if (m_controllers.isEmpty())
        stopListening();
}

} // namespace WebCore