author Nika Layzell <>
Thu, 06 Aug 2020 14:04:13 +0000
changeset 544125 ee09cb88af177571304759bc05c760e3d82fd1ed
parent 514774 6fb8c8d916eb951b35cf161789f8395957b73616
permissions -rw-r--r--
Bug 1656854 - Part 2: Add a BrowsingContextGroup keepalive to BrowserParent shutdown, r=farre In bug 1652085, I added BrowsingContextGroup keepalives while waiting for replies to the discard message, however that message isn't actually sent to the current owner process. Instead, the BrowsingContext is discarded by the PBrowser being destroyed. This should help ensure we also keep the group alive during normal BrowserParent destruction. Differential Revision:

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at */

#ifndef mozilla_dom_XULBroadcastManager_h
#define mozilla_dom_XULBroadcastManager_h

#include "mozilla/dom/Element.h"
#include "nsAtom.h"

class nsXULElement;

namespace mozilla {
namespace dom {

class XULBroadcastManager final {
  explicit XULBroadcastManager(Document* aDocument);


   * Checks whether an element uses any of the special broadcaster attributes
   * or is an observes element. This mimics the logic in FindBroadcaster, but
   * is intended to be a lighter weight check and doesn't actually guarantee
   * that the element will need a listener.
  static bool MayNeedListener(const Element& aElement);

  nsresult AddListener(Element* aElement);
  nsresult RemoveListener(Element* aElement);
  void AttributeChanged(Element* aElement, int32_t aNameSpaceID,
                        nsAtom* aAttribute);
  void MaybeBroadcast();
  void DropDocumentReference();  // notification that doc is going away
  enum HookupAction { eHookupAdd = 0, eHookupRemove };

  nsresult UpdateListenerHookup(Element* aElement, HookupAction aAction);

  void RemoveListenerFor(Element& aBroadcaster, Element& aListener,
                         const nsAString& aAttr);
  void AddListenerFor(Element& aBroadcaster, Element& aListener,
                      const nsAString& aAttr, ErrorResult& aRv);

  nsresult ExecuteOnBroadcastHandlerFor(Element* aBroadcaster,
                                        Element* aListener, nsAtom* aAttr);
  // The out params of FindBroadcaster only have values that make sense when
  // the method returns NS_FINDBROADCASTER_FOUND.  In all other cases, the
  // values of the out params should not be relied on (though *aListener and
  // *aBroadcaster do need to be released if non-null, of course).
  nsresult FindBroadcaster(Element* aElement, Element** aListener,
                           nsString& aBroadcasterID, nsString& aAttribute,
                           Element** aBroadcaster);

  void SynchronizeBroadcastListener(Element* aBroadcaster, Element* aListener,
                                    const nsAString& aAttr);

  // This reference is nulled by the Document in it's destructor through
  // DropDocumentReference().
  Document* MOZ_NON_OWNING_REF mDocument;

   * A map from a broadcaster element to a list of listener elements.
  PLDHashTable* mBroadcasterMap;

  class nsDelayedBroadcastUpdate {
    nsDelayedBroadcastUpdate(Element* aBroadcaster, Element* aListener,
                             const nsAString& aAttr)
        : mBroadcaster(aBroadcaster),
          mNeedsAttrChange(false) {}

    nsDelayedBroadcastUpdate(Element* aBroadcaster, Element* aListener,
                             nsAtom* aAttrName, const nsAString& aAttr,
                             bool aSetAttr, bool aNeedsAttrChange)
        : mBroadcaster(aBroadcaster),
          mNeedsAttrChange(aNeedsAttrChange) {}

    nsDelayedBroadcastUpdate(const nsDelayedBroadcastUpdate& aOther) = delete;
    nsDelayedBroadcastUpdate(nsDelayedBroadcastUpdate&& aOther) = default;

    nsCOMPtr<Element> mBroadcaster;
    nsCOMPtr<Element> mListener;
    // Note if mAttrName isn't used, this is the name of the attr, otherwise
    // this is the value of the attribute.
    nsString mAttr;
    RefPtr<nsAtom> mAttrName;
    bool mSetAttr;
    bool mNeedsAttrChange;

    class Comparator {
      static bool Equals(const nsDelayedBroadcastUpdate& a,
                         const nsDelayedBroadcastUpdate& b) {
        return a.mBroadcaster == b.mBroadcaster && a.mListener == b.mListener &&
               a.mAttrName == b.mAttrName;
  nsTArray<nsDelayedBroadcastUpdate> mDelayedBroadcasters;
  nsTArray<nsDelayedBroadcastUpdate> mDelayedAttrChangeBroadcasts;
  bool mHandlingDelayedAttrChange;
  bool mHandlingDelayedBroadcasters;


}  // namespace dom
}  // namespace mozilla

#endif  // mozilla_dom_XULBroadcastManager_h