Issue #1655: Update MediaQueryList to the current draft spec.

This make MediaQueryList inherit from EventTarget and adds MediaQueryListEvent
as an interface as well as the onchange() method.
This should not affect compatibility with other code; the event object is a
MediaQueryListEvent instance, which is recognized as a MediaListQuery instance.

dom/base/nsDocument.cpp

@@ -1785,7 +1785,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsDocument)
        l != &tmp->mDOMMediaQueryLists; ) {
     PRCList *next = PR_NEXT_LINK(l);
     MediaQueryList *mql = static_cast<MediaQueryList*>(l);
-    mql->RemoveAllListeners();
+    mql->Disconnect();
     l = next;
   }
 

dom/webidl/MediaQueryList.webidl

@@ -4,17 +4,21 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  *
  * The origin of this IDL file is
- * http://dev.w3.org/csswg/cssom-view/#the-mediaquerylist-interface
+ * https://drafts.csswg.org/cssom-view/#mediaquerylist
  *
  * Copyright © 2012 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C
  * liability, trademark and document use rules apply.
  */
 
-interface MediaQueryList {
+interface MediaQueryList : EventTarget {
   readonly attribute DOMString media;
   readonly attribute boolean matches;
-  void addListener(MediaQueryListListener listener);
-  void removeListener(MediaQueryListListener listener);
-};
 
-callback MediaQueryListListener = void (MediaQueryList list);
+  [Throws]
+  void addListener(EventListener? listener);
+
+  [Throws]
+  void removeListener(EventListener? listener);
+
+           attribute EventHandler onchange;
+};

dom/webidl/MediaQueryListEvent.webidl

@@ -0,0 +1,18 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 http://mozilla.org/MPL/2.0/.
+ *
+ * https://drafts.csswg.org/cssom-view/#mediaquerylistevent
+ */
+
+[Constructor(DOMString type, optional MediaQueryListEventInit eventInitDict)]
+interface MediaQueryListEvent : Event {
+  readonly attribute DOMString media;
+  readonly attribute boolean matches;
+};
+
+dictionary MediaQueryListEventInit : EventInit {
+  DOMString media = "";
+  boolean matches = false;
+};

dom/webidl/moz.build

@@ -684,6 +684,7 @@ GENERATED_EVENTS_WEBIDL_FILES = [
     'HashChangeEvent.webidl',
     'HiddenPluginEvent.webidl',
     'ImageCaptureErrorEvent.webidl',
+    'MediaQueryListEvent.webidl',
     'MediaStreamEvent.webidl',
     'MediaStreamTrackEvent.webidl',
     'MozSettingsEvent.webidl',

layout/base/nsPresContext.cpp

@@ -1931,33 +1931,13 @@ nsPresContext::MediaFeatureValuesChanged(nsRestyleHint aRestyleHint,
 
   if (!PR_CLIST_IS_EMPTY(mDocument->MediaQueryLists())) {
     // We build a list of all the notifications we're going to send
-    // before we send any of them.  (The spec says the notifications
-    // should be a queued task, so any removals that happen during the
-    // notifications shouldn't affect what gets notified.)  Furthermore,
-    // we hold strong pointers to everything we're going to make
-    // notification calls to, since each notification involves calling
-    // arbitrary script that might otherwise destroy these objects, or,
-    // for that matter, |this|.
-    //
-    // Note that we intentionally send the notifications to media query
-    // list in the order they were created and, for each list, to the
-    // listeners in the order added.
-    nsTArray<MediaQueryList::HandleChangeData> notifyList;
+    // before we send any of them.
     for (PRCList *l = PR_LIST_HEAD(mDocument->MediaQueryLists());
          l != mDocument->MediaQueryLists(); l = PR_NEXT_LINK(l)) {
+      nsAutoMicroTask mt;
       MediaQueryList *mql = static_cast<MediaQueryList*>(l);
-      mql->MediumFeaturesChanged(notifyList);
+      mql->MaybeNotify();
     }
-
-    if (!notifyList.IsEmpty()) {
-      for (uint32_t i = 0, i_end = notifyList.Length(); i != i_end; ++i) {
-        nsAutoMicroTask mt;
-        MediaQueryList::HandleChangeData &d = notifyList[i];
-        d.callback->Call(*d.mql);
-      }
-    }
-
-    // NOTE:  When |notifyList| goes out of scope, our destructor could run.
   }
 }
 

layout/style/MediaQueryList.cpp

@@ -1,5 +1,4 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
 /* 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 http://mozilla.org/MPL/2.0/. */
@@ -7,19 +6,26 @@
 /* implements DOM interface for querying and observing media queries */
 
 #include "mozilla/dom/MediaQueryList.h"
+#include "mozilla/dom/MediaQueryListEvent.h"
+#include "mozilla/dom/EventTarget.h"
+#include "mozilla/dom/EventTargetBinding.h"
 #include "nsPresContext.h"
 #include "nsIMediaList.h"
 #include "nsCSSParser.h"
 #include "nsIDocument.h"
 
+// Fixed event target type
+#define ONCHANGE_STRING NS_LITERAL_STRING("change")
+
 namespace mozilla {
 namespace dom {
 
 MediaQueryList::MediaQueryList(nsIDocument *aDocument,
                                const nsAString &aMediaQueryList)
-  : mDocument(aDocument),
-    mMediaList(new nsMediaList),
-    mMatchesValid(false)
+  : mDocument(aDocument)
+  , mMediaList(new nsMediaList)
+  , mMatchesValid(false)
+  , mIsKeptAlive(false)
 {
   PR_INIT_CLIST(this);
 
@@ -36,30 +42,24 @@ MediaQueryList::~MediaQueryList()
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(MediaQueryList)
 
-NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(MediaQueryList)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(MediaQueryList, DOMEventTargetHelper)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocument)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCallbacks)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
-NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(MediaQueryList)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(MediaQueryList, DOMEventTargetHelper)
   if (tmp->mDocument) {
     PR_REMOVE_LINK(tmp);
     NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocument)
   }
-  tmp->RemoveAllListeners();
+  tmp->Disconnect();
   NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
-NS_IMPL_CYCLE_COLLECTION_TRACE_WRAPPERCACHE(MediaQueryList)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(MediaQueryList)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
 
-NS_INTERFACE_MAP_BEGIN(MediaQueryList)
-  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
-  NS_INTERFACE_MAP_ENTRY(nsISupports)
-  NS_INTERFACE_MAP_ENTRIES_CYCLE_COLLECTION(MediaQueryList)
-NS_INTERFACE_MAP_END
-
-NS_IMPL_CYCLE_COLLECTING_ADDREF(MediaQueryList)
-NS_IMPL_CYCLE_COLLECTING_RELEASE(MediaQueryList)
+NS_IMPL_ADDREF_INHERITED(MediaQueryList, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(MediaQueryList, DOMEventTargetHelper)
 
 void
 MediaQueryList::GetMedia(nsAString &aMedia)
@@ -80,57 +80,124 @@ MediaQueryList::Matches()
 }
 
 void
-MediaQueryList::AddListener(MediaQueryListListener& aListener)
+MediaQueryList::AddListener(EventListener* aListener, ErrorResult& aRv)
 {
-  if (!HasListeners()) {
-    // When we have listeners, the pres context owns a reference to
-    // this.  This is a cyclic reference that can only be broken by
-    // cycle collection.
-    NS_ADDREF_THIS();
+  if (!aListener) {
+    return;
   }
 
+  AddEventListenerOptionsOrBoolean options;
+  options.SetAsBoolean() = false;
+
+  AddEventListener(ONCHANGE_STRING, aListener, options, Nullable<bool>(), aRv);
+}
+
+void
+MediaQueryList::AddEventListener(const nsAString& aType,
+                                 EventListener* aCallback,
+                                 const AddEventListenerOptionsOrBoolean& aOptions,
+                                 const dom::Nullable<bool>& aWantsUntrusted,
+                                 ErrorResult& aRv)
+{
   if (!mMatchesValid) {
     MOZ_ASSERT(!HasListeners(),
                "when listeners present, must keep mMatches current");
     RecomputeMatches();
   }
 
-  for (uint32_t i = 0; i < mCallbacks.Length(); ++i) {
-    if (aListener == *mCallbacks[i]) {
-      // Already registered
-      return;
-    }
+  DOMEventTargetHelper::AddEventListener(aType, aCallback, aOptions,
+                                         aWantsUntrusted, aRv);
+
+  if (aRv.Failed()) {
+    return;
   }
 
-  if (!mCallbacks.AppendElement(&aListener, fallible)) {
-    if (!HasListeners()) {
-      // Append failed; undo the AddRef above.
-      NS_RELEASE_THIS();
-    }
-  }
+  UpdateMustKeepAlive();
 }
 
 void
-MediaQueryList::RemoveListener(MediaQueryListListener& aListener)
+MediaQueryList::RemoveListener(EventListener* aListener, ErrorResult& aRv)
 {
-  for (uint32_t i = 0; i < mCallbacks.Length(); ++i) {
-    if (aListener == *mCallbacks[i]) {
-      mCallbacks.RemoveElementAt(i);
-      if (!HasListeners()) {
-        // See NS_ADDREF_THIS() in AddListener.
-        NS_RELEASE_THIS();
-      }
-      break;
-    }
+  if (!aListener) {
+    return;
   }
+
+  EventListenerOptionsOrBoolean options;
+  options.SetAsBoolean() = false;
+
+  RemoveEventListener(ONCHANGE_STRING, aListener, options, aRv);
 }
 
 void
-MediaQueryList::RemoveAllListeners()
+MediaQueryList::RemoveEventListener(const nsAString& aType,
+                                    EventListener* aCallback,
+                                    const EventListenerOptionsOrBoolean& aOptions,
+                                    ErrorResult& aRv)
 {
-  bool hadListeners = HasListeners();
-  mCallbacks.Clear();
-  if (hadListeners) {
+  DOMEventTargetHelper::RemoveEventListener(aType, aCallback, aOptions, aRv);
+
+  if (aRv.Failed()) {
+    return;
+  }
+
+  UpdateMustKeepAlive();
+}
+
+EventHandlerNonNull*
+MediaQueryList::GetOnchange()
+{
+  if (NS_IsMainThread()) {
+    return GetEventHandler(nsGkAtoms::onchange, EmptyString());
+  }
+  return GetEventHandler(nullptr, ONCHANGE_STRING);
+}
+
+void
+MediaQueryList::SetOnchange(EventHandlerNonNull* aCallback)
+{
+  if (NS_IsMainThread()) {
+    SetEventHandler(nsGkAtoms::onchange, EmptyString(), aCallback);
+  } else {
+    SetEventHandler(nullptr, ONCHANGE_STRING, aCallback);
+  }
+
+  UpdateMustKeepAlive();
+}
+
+void
+MediaQueryList::UpdateMustKeepAlive()
+{
+  bool toKeepAlive = HasListeners();
+  if (toKeepAlive == mIsKeptAlive) {
+    return;
+  }
+
+  // When we have listeners, the pres context owns a reference to
+  // this.  This is a cyclic reference that can only be broken by
+  // cycle collection.
+
+  mIsKeptAlive = toKeepAlive;
+
+  if (toKeepAlive) {
+    NS_ADDREF_THIS();
+  } else {
+    NS_RELEASE_THIS();
+  }
+}
+
+bool
+MediaQueryList::HasListeners()
+{
+  return HasListenersFor(ONCHANGE_STRING);
+}
+
+void
+MediaQueryList::Disconnect()
+{
+  DisconnectFromOwner();
+
+  if (mIsKeptAlive) {
+    mIsKeptAlive = false;
     // See NS_ADDREF_THIS() in AddListener.
     NS_RELEASE_THIS();
   }
@@ -169,27 +236,6 @@ MediaQueryList::RecomputeMatches()
   mMatchesValid = true;
 }
 
-void
-MediaQueryList::MediumFeaturesChanged(
-    nsTArray<HandleChangeData>& aListenersToNotify)
-{
-  mMatchesValid = false;
-
-  if (HasListeners()) {
-    bool oldMatches = mMatches;
-    RecomputeMatches();
-    if (mMatches != oldMatches) {
-      for (uint32_t i = 0, i_end = mCallbacks.Length(); i != i_end; ++i) {
-        HandleChangeData *d = aListenersToNotify.AppendElement(fallible);
-        if (d) {
-          d->mql = this;
-          d->callback = mCallbacks[i];
-        }
-      }
-    }
-  }
-}
-
 nsISupports*
 MediaQueryList::GetParentObject() const
 {
@@ -202,5 +248,36 @@ MediaQueryList::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
   return MediaQueryListBinding::Wrap(aCx, this, aGivenProto);
 }
 
+void
+MediaQueryList::MaybeNotify()
+{
+  mMatchesValid = false;
+
+  if (!HasListeners()) {
+    return;
+  }
+
+  bool oldMatches = mMatches;
+  RecomputeMatches();
+
+  // No need to notify the change.
+  if (mMatches == oldMatches) {
+    return;
+  }
+
+  MediaQueryListEventInit init;
+  init.mBubbles = false;
+  init.mCancelable = false;
+  init.mMatches = mMatches;
+  mMediaList->GetText(init.mMedia);
+
+  RefPtr<MediaQueryListEvent> event =
+    MediaQueryListEvent::Constructor(this, ONCHANGE_STRING, init);
+  event->SetTrusted(true);
+
+  bool dummy;
+  DispatchEvent(event, &dummy);
+}
+
 } // namespace dom
 } // namespace mozilla

layout/style/MediaQueryList.h

@@ -16,6 +16,7 @@
 #include "prclist.h"
 #include "mozilla/Attributes.h"
 #include "nsWrapperCache.h"
+#include "mozilla/DOMEventTargetHelper.h"
 #include "mozilla/dom/MediaQueryListBinding.h"
 
 class nsIDocument;
@@ -24,8 +25,7 @@ class nsMediaList;
 namespace mozilla {
 namespace dom {
 
-class MediaQueryList final : public nsISupports,
-                             public nsWrapperCache,
+class MediaQueryList final : public DOMEventTargetHelper,
                              public PRCList
 {
 public:
@@ -37,33 +37,45 @@ private:
   ~MediaQueryList();
 
 public:
-  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
-  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(MediaQueryList)
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(MediaQueryList, DOMEventTargetHelper)
 
   nsISupports* GetParentObject() const;
 
-  struct HandleChangeData {
-    RefPtr<MediaQueryList> mql;
-    RefPtr<mozilla::dom::MediaQueryListListener> callback;
-  };
-
-  // Appends listeners that need notification to aListenersToNotify
-  void MediumFeaturesChanged(nsTArray<HandleChangeData>& aListenersToNotify);
-
-  bool HasListeners() const { return !mCallbacks.IsEmpty(); }
-
-  void RemoveAllListeners();
+  void MaybeNotify();
 
   JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
 
   // WebIDL methods
   void GetMedia(nsAString& aMedia);
   bool Matches();
-  void AddListener(mozilla::dom::MediaQueryListListener& aListener);
-  void RemoveListener(mozilla::dom::MediaQueryListListener& aListener);
+  void AddListener(EventListener* aListener, ErrorResult& aRv);
+  void RemoveListener(EventListener* aListener, ErrorResult& aRv);
+
+  EventHandlerNonNull* GetOnchange();
+  void SetOnchange(EventHandlerNonNull* aCallback);
+
+  using nsIDOMEventTarget::AddEventListener;
+  using nsIDOMEventTarget::RemoveEventListener;
+
+  virtual void AddEventListener(const nsAString& aType,
+                                EventListener* aCallback,
+                                const AddEventListenerOptionsOrBoolean& aOptions,
+                                const Nullable<bool>& aWantsUntrusted,
+                                ErrorResult& aRv) override;
+  virtual void RemoveEventListener(const nsAString& aType,
+                                   EventListener* aCallback,
+                                   const EventListenerOptionsOrBoolean& aOptions,
+                                   ErrorResult& aRv) override;
+
+  bool HasListeners();
+
+  void Disconnect();
 
 private:
   void RecomputeMatches();
+  
+  void UpdateMustKeepAlive();
 
   // We only need a pointer to the document to support lazy
   // reevaluation following dynamic changes.  However, this lazy
@@ -84,7 +96,7 @@ private:
   RefPtr<nsMediaList> mMediaList;
   bool mMatches;
   bool mMatchesValid;
-  nsTArray<RefPtr<mozilla::dom::MediaQueryListListener>> mCallbacks;
+  bool mIsKeptAlive;
 };
 
 } // namespace dom