flutter_flutter/engine/bindings/core/v8/CallbackPromiseAdapter.h

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 */

#ifndef CallbackPromiseAdapter_h
#define CallbackPromiseAdapter_h

#include "bindings/core/v8/ScriptPromiseResolver.h"
#include "public/platform/WebCallbacks.h"

namespace blink {

// This class provides an easy way to convert from a Script-exposed
// class (i.e. a class that has a toV8() overload) that uses Promises
// to a WebKit API class that uses WebCallbacks. You can define
// separate Success and Error classes, but this example just uses one
// object for both.
//
// To use:
//
// class MyClass ... {
//    typedef blink::WebMyClass WebType;
//    static PassRefPtr<MyClass> take(ScriptPromiseResolver* resolver,
//                                    blink::WebMyClass* webInstance) {
//        // convert/create as appropriate, but often it's just:
//        return MyClass::create(adoptPtr(webInstance));
//
//        // Since promise resolving is done as an async task, it's not
//        // guaranteed that the script context has seen the promise resolve
//        // immediately after calling onSuccess/onError. You can use the
//        // ScriptPromise from the resolver to schedule a task that executes
//        // after resolving:
//        ScriptState::Scope scope(resolver->scriptState());
//        resolver->promise().then(...);
//    }
//
//    // Called when aborting to resolve/reject a promise due to an empty
//    // execution context.
//    static void dispose(blink::WebMyClass* webInstance) {
//        // delete as appropriate, but often it's just:
//        delete webInstance;
//    }
//
// Now when calling into a WebKit API that requires a WebCallbacks<blink::WebMyClass, blink::WebMyClass>*:
//
//    // call signature: callSomeMethod(WebCallbacks<MyClass, MyClass>* callbacks)
//    webObject->callSomeMethod(new CallbackPromiseAdapter<MyClass, MyClass>(resolver, scriptExecutionContext));
//
// Note that this class does not manage its own lifetime. In this
// example that ownership of the WebCallbacks instance is being passed
// in and it is up to the callee to free the WebCallbacks instace.
template<typename S, typename T>
class CallbackPromiseAdapter FINAL : public blink::WebCallbacks<typename S::WebType, typename T::WebType> {
public:
    explicit CallbackPromiseAdapter(PassRefPtr<ScriptPromiseResolver> resolver)
        : m_resolver(resolver)
    {
        ASSERT(m_resolver);
    }
    virtual ~CallbackPromiseAdapter() { }

    virtual void onSuccess(typename S::WebType* result) OVERRIDE
    {
        if (!m_resolver->executionContext() || m_resolver->executionContext()->activeDOMObjectsAreStopped()) {
            S::dispose(result);
            return;
        }
        m_resolver->resolve(S::take(m_resolver.get(), result));
    }

    virtual void onError(typename T::WebType* error) OVERRIDE
    {
        if (!m_resolver->executionContext() || m_resolver->executionContext()->activeDOMObjectsAreStopped()) {
            T::dispose(error);
            return;
        }
        m_resolver->reject(T::take(m_resolver.get(), error));
    }

private:
    RefPtr<ScriptPromiseResolver> m_resolver;
    WTF_MAKE_NONCOPYABLE(CallbackPromiseAdapter);
};

template<typename T>
class CallbackPromiseAdapter<void, T> FINAL : public blink::WebCallbacks<void, typename T::WebType> {
public:
    explicit CallbackPromiseAdapter(PassRefPtr<ScriptPromiseResolver> resolver)
        : m_resolver(resolver)
    {
        ASSERT(m_resolver);
    }
    virtual ~CallbackPromiseAdapter() { }

    virtual void onSuccess() OVERRIDE
    {
        if (!m_resolver->executionContext() || m_resolver->executionContext()->activeDOMObjectsAreStopped()) {
            return;
        }
        m_resolver->resolve(V8UndefinedType());
    }

    virtual void onError(typename T::WebType* error) OVERRIDE
    {
        if (!m_resolver->executionContext() || m_resolver->executionContext()->activeDOMObjectsAreStopped()) {
            T::dispose(error);
            return;
        }
        m_resolver->reject(T::take(m_resolver.get(), error));
    }

private:
    RefPtr<ScriptPromiseResolver> m_resolver;
    WTF_MAKE_NONCOPYABLE(CallbackPromiseAdapter);
};

} // namespace blink

#endif