1 files changed, 107 insertions, 0 deletions
diff --git a/layout/style/MediaQueryList.h b/layout/style/MediaQueryList.h
new file mode 100644
index 0000000000..046fe55dd5
--- /dev/null
+++ b/layout/style/MediaQueryList.h
@@ -0,0 +1,107 @@
+/* -*- 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 http://mozilla.org/MPL/2.0/. */
+
+/* implements DOM interface for querying and observing media queries */
+
+#ifndef mozilla_dom_MediaQueryList_h
+#define mozilla_dom_MediaQueryList_h
+
+#include "nsISupports.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsCOMPtr.h"
+#include "nsTArray.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Attributes.h"
+#include "nsWrapperCache.h"
+#include "mozilla/DOMEventTargetHelper.h"
+#include "mozilla/dom/MediaQueryListBinding.h"
+
+namespace mozilla::dom {
+
+class MediaList;
+
+class MediaQueryList final : public DOMEventTargetHelper,
+                             public LinkedListElement<MediaQueryList> {
+ public:
+  // The caller who constructs is responsible for calling Evaluate
+  // before calling any other methods.
+  MediaQueryList(Document* aDocument, const nsACString& aMediaQueryList,
+                 CallerType);
+
+ private:
+  ~MediaQueryList();
+
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(MediaQueryList, DOMEventTargetHelper)
+
+  nsISupports* GetParentObject() const;
+
+  void MediaFeatureValuesChanged();
+
+  // Returns whether we need to notify of the change by dispatching a change
+  // event.
+  [[nodiscard]] bool EvaluateOnRenderingUpdate();
+  void FireChangeEvent();
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  // WebIDL methods
+  void GetMedia(nsACString& aMedia) const;
+  bool Matches();
+  void AddListener(EventListener* aListener, ErrorResult& aRv);
+  void RemoveListener(EventListener* aListener, ErrorResult& aRv);
+
+  IMPL_EVENT_HANDLER(change)
+
+  bool HasListeners() const;
+
+  void Disconnect();
+
+  size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;
+
+ private:
+  void LastRelease() final {
+    auto* listElement = static_cast<LinkedListElement<MediaQueryList>*>(this);
+    if (listElement->isInList()) {
+      listElement->remove();
+    }
+  }
+
+  void RecomputeMatches();
+
+  // We only need a pointer to the document to support lazy
+  // reevaluation following dynamic changes.  However, this lazy
+  // reevaluation is perhaps somewhat important, since some usage
+  // patterns may involve the creation of large numbers of
+  // MediaQueryList objects which almost immediately become garbage
+  // (after a single call to the .matches getter).
+  //
+  // This pointer does make us a little more dependent on cycle
+  // collection.
+  //
+  // We have a non-null mDocument for our entire lifetime except
+  // after cycle collection unlinking.  Having a non-null mDocument
+  // is equivalent to being in that document's mDOMMediaQueryLists
+  // linked list.
+  RefPtr<Document> mDocument;
+  const RefPtr<const MediaList> mMediaList;
+  // Whether our MediaList depends on our viewport size. Our medialist is
+  // immutable, so we can just compute this once and carry on with our lives.
+  const bool mViewportDependent : 1;
+  // The matches state.
+  // https://drafts.csswg.org/cssom-view/#mediaquerylist-matches-state
+  bool mMatches : 1;
+  // The value of the matches state on creation, or on the last rendering
+  // update, in order to implement:
+  // https://drafts.csswg.org/cssom-view/#evaluate-media-queries-and-report-changes
+  bool mMatchesOnRenderingUpdate : 1;
+};
+
+}  // namespace mozilla::dom
+
+#endif /* !defined(mozilla_dom_MediaQueryList_h) */