forked from mirrors/gecko-dev
0dea82ac15
Depends on D145735 Differential Revision: https://phabricator.services.mozilla.com/D145736
112 lines
3.7 KiB
C++
112 lines
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_dom_DOMMozPromiseRequestHolder_h
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#define mozilla_dom_DOMMozPromiseRequestHolder_h
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#include "mozilla/DOMEventTargetHelper.h"
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#include "mozilla/MozPromise.h"
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namespace mozilla::dom {
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/**
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* This is a helper class that can be used when MozPromises are
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* being consumed by binding layer code. It effectively creates
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* a MozPromiseRequestHolder that auto-disconnects when the binding's
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* global is disconnected.
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*
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* It can be used like this:
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*
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* RefPtr<Promise>
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* SomeAsyncAPI(Args& aArgs, ErrorResult& aRv)
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* {
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* nsIGlobalObject* global = GetParentObject();
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* if (!global) {
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* aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
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* return nullptr;
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* }
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*
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* RefPtr<Promise> outer = Promise::Create(global, aRv);
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* if (aRv.Failed()) {
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* return nullptr;
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* }
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*
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* RefPtr<DOMMozPromiseRequestHolder> holder =
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* new DOMMozPromiseRequestHolder(global);
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*
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* DoAsyncStuff()->Then(
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* global->EventTargetFor(TaskCategory::Other), __func__,
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* [holder, outer] (const Result& aResult) {
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* holder->Complete();
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*
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* // Note, you can access the holder's bound global in
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* // your reaction handler. Its mostly likely set if
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* // the handler fires, but you still must check for
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* // its existence since something could disconnect
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* // the global between when the MozPromise reaction
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* // runnable is queued and when it actually runs.
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* nsIGlobalObject* global = holder->GetParentObject();
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* NS_ENSURE_TRUE_VOID(global);
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*
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* outer->MaybeResolve(aResult);
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* }, [holder, outer] (nsresult aRv) {
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* holder->Complete();
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* outer->MaybeReject(aRv);
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* })->Track(*holder);
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*
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* return outer.forget();
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* }
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*
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* NOTE: Currently this helper class extends DETH. This is only
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* so that it can bind to the global and receive the
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* DisconnectFromOwner() method call. In this future the
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* binding code should be factored out so DETH is not
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* needed here. See bug 1456893.
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*/
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template <typename PromiseType>
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class DOMMozPromiseRequestHolder final : public DOMEventTargetHelper {
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MozPromiseRequestHolder<PromiseType> mHolder;
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~DOMMozPromiseRequestHolder() = default;
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void DisconnectFromOwner() override {
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mHolder.DisconnectIfExists();
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DOMEventTargetHelper::DisconnectFromOwner();
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}
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JSObject* WrapObject(JSContext* aCx,
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JS::Handle<JSObject*> aGivenProto) override {
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// We are extending DETH to get notified when the global goes
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// away, but this object should never actually be exposed to
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// script.
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MOZ_CRASH("illegal method");
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}
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public:
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explicit DOMMozPromiseRequestHolder(nsIGlobalObject* aGlobal)
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: DOMEventTargetHelper(aGlobal) {
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MOZ_DIAGNOSTIC_ASSERT(aGlobal);
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}
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operator MozPromiseRequestHolder<PromiseType>&() { return mHolder; }
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operator const MozPromiseRequestHolder<PromiseType>&() const {
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return mHolder;
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}
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void Complete() { mHolder.Complete(); }
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void DisconnectIfExists() { mHolder.DisconnectIfExists(); }
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bool Exists() const { return mHolder.Exists(); }
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NS_INLINE_DECL_REFCOUNTING_INHERITED(DOMMozPromiseRequestHolder,
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DOMEventTargetHelper)
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};
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} // namespace mozilla::dom
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#endif // mozilla_dom_DOMMozPromiseRequestHolder_h
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