Source/WebCore/dom/MutationObserver.cpp

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 * in the documentation and/or other materials provided with the
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 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#include "config.h"

#include "MutationObserver.h"

#include "Dictionary.h"
#include "Document.h"
#include "ExceptionCode.h"
#include "Microtasks.h"
#include "MutationCallback.h"
#include "MutationObserverRegistration.h"
#include "MutationRecord.h"
#include <algorithm>
#include <wtf/MainThread.h>

namespace WebCore {

static unsigned s_observerPriority = 0;

Ref<MutationObserver> MutationObserver::create(Ref<MutationCallback>&& callback)
{
    ASSERT(isMainThread());
    return adoptRef(*new MutationObserver(WTFMove(callback)));
}

MutationObserver::MutationObserver(Ref<MutationCallback>&& callback)
    : m_callback(WTFMove(callback))
    , m_priority(s_observerPriority++)
{
}

MutationObserver::~MutationObserver()
{
    ASSERT(m_registrations.isEmpty());
}

bool MutationObserver::validateOptions(MutationObserverOptions options)
{
    return (options & (Attributes | CharacterData | ChildList))
        && ((options & Attributes) || !(options & AttributeOldValue))
        && ((options & Attributes) || !(options & AttributeFilter))
        && ((options & CharacterData) || !(options & CharacterDataOldValue));
}

void MutationObserver::observe(Node& node, const Dictionary& optionsDictionary, ExceptionCode& ec)
{
    static const struct {
        const char* name;
        MutationObserverOptions value;
    } booleanOptions[] = {
        { "childList", ChildList },
        { "subtree", Subtree },
        { "attributeOldValue", AttributeOldValue },
        { "characterDataOldValue", CharacterDataOldValue }
    };
    MutationObserverOptions options = 0;
    bool value = false;
    for (auto& booleanOption : booleanOptions) {
        if (optionsDictionary.get(booleanOption.name, value) && value)
            options |= booleanOption.value;
    }

    HashSet<AtomicString> attributeFilter;
    if (optionsDictionary.get("attributeFilter", attributeFilter))
        options |= AttributeFilter;

    bool attributesOptionIsSet = optionsDictionary.get("attributes", value);
    if ((attributesOptionIsSet && value) || (!attributesOptionIsSet && (options & (AttributeFilter | AttributeOldValue))))
        options |= Attributes;

    bool characterDataOptionIsSet = optionsDictionary.get("characterData", value);
    if ((characterDataOptionIsSet && value) || (!characterDataOptionIsSet && (options & CharacterDataOldValue)))
        options |= CharacterData;

    if (!validateOptions(options)) {
        ec = TypeError;
        return;
    }

    node.registerMutationObserver(this, options, attributeFilter);
}

Vector<Ref<MutationRecord>> MutationObserver::takeRecords()
{
    Vector<Ref<MutationRecord>> records;
    records.swap(m_records);
    return records;
}

void MutationObserver::disconnect()
{
    m_records.clear();
    HashSet<MutationObserverRegistration*> registrations(m_registrations);
    for (auto* registration : registrations)
        MutationObserverRegistration::unregisterAndDelete(registration);
}

void MutationObserver::observationStarted(MutationObserverRegistration* registration)
{
    ASSERT(!m_registrations.contains(registration));
    m_registrations.add(registration);
}

void MutationObserver::observationEnded(MutationObserverRegistration* registration)
{
    ASSERT(m_registrations.contains(registration));
    m_registrations.remove(registration);
}

typedef HashSet<RefPtr<MutationObserver>> MutationObserverSet;

static MutationObserverSet& activeMutationObservers()
{
    static NeverDestroyed<MutationObserverSet> activeObservers;
    return activeObservers;
}

static MutationObserverSet& suspendedMutationObservers()
{
    static NeverDestroyed<MutationObserverSet> suspendedObservers;
    return suspendedObservers;
}

static bool mutationObserverCompoundMicrotaskQueuedFlag;

class MutationObserverMicrotask final : public Microtask {
    WTF_MAKE_FAST_ALLOCATED;
public:
    MutationObserverMicrotask()
    {
    }

    virtual ~MutationObserverMicrotask()
    {
    }

private:
    Result run() override
    {
        mutationObserverCompoundMicrotaskQueuedFlag = false;

        MutationObserver::deliverAllMutations();

        return Result::Done;
    }
};

static void queueMutationObserverCompoundMicrotask()
{
    if (mutationObserverCompoundMicrotaskQueuedFlag)
        return;
    mutationObserverCompoundMicrotaskQueuedFlag = true;

    auto microtask = std::make_unique<MutationObserverMicrotask>();
    MicrotaskQueue::mainThreadQueue().append(WTFMove(microtask));
}

void MutationObserver::enqueueMutationRecord(Ref<MutationRecord>&& mutation)
{
    ASSERT(isMainThread());
    m_records.append(WTFMove(mutation));
    activeMutationObservers().add(this);

    queueMutationObserverCompoundMicrotask();
}

void MutationObserver::setHasTransientRegistration()
{
    ASSERT(isMainThread());
    activeMutationObservers().add(this);

    queueMutationObserverCompoundMicrotask();
}

HashSet<Node*> MutationObserver::getObservedNodes() const
{
    HashSet<Node*> observedNodes;
    for (auto* registration : m_registrations)
        registration->addRegistrationNodesToSet(observedNodes);
    return observedNodes;
}

bool MutationObserver::canDeliver()
{
    return m_callback->canInvokeCallback();
}

void MutationObserver::deliver()
{
    ASSERT(canDeliver());

    // Calling clearTransientRegistrations() can modify m_registrations, so it's necessary
    // to make a copy of the transient registrations before operating on them.
    Vector<MutationObserverRegistration*, 1> transientRegistrations;
    for (auto* registration : m_registrations) {
        if (registration->hasTransientRegistrations())
            transientRegistrations.append(registration);
    }
    for (auto& registration : transientRegistrations)
        registration->clearTransientRegistrations();

    if (m_records.isEmpty())
        return;

    Vector<Ref<MutationRecord>> records;
    records.swap(m_records);

    m_callback->call(records, this);
}

void MutationObserver::deliverAllMutations()
{
    ASSERT(isMainThread());
    static bool deliveryInProgress = false;
    if (deliveryInProgress)
        return;
    deliveryInProgress = true;

    if (!suspendedMutationObservers().isEmpty()) {
        Vector<RefPtr<MutationObserver>> suspended;
        copyToVector(suspendedMutationObservers(), suspended);
        for (auto& observer : suspended) {
            if (!observer->canDeliver())
                continue;

            suspendedMutationObservers().remove(observer);
            activeMutationObservers().add(observer);
        }
    }

    while (!activeMutationObservers().isEmpty()) {
        Vector<RefPtr<MutationObserver>> observers;
        copyToVector(activeMutationObservers(), observers);
        activeMutationObservers().clear();
        std::sort(observers.begin(), observers.end(), [](const RefPtr<MutationObserver>& lhs, const RefPtr<MutationObserver>& rhs) {
            return lhs->m_priority < rhs->m_priority;
        });

        for (auto& observer : observers) {
            if (observer->canDeliver())
                observer->deliver();
            else
                suspendedMutationObservers().add(observer);
        }
    }

    deliveryInProgress = false;
}

} // namespace WebCore