tor-browser

The Tor Browser
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MediaQueryList.h (3554B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 /* implements DOM interface for querying and observing media queries */
      8 
      9 #ifndef mozilla_dom_MediaQueryList_h
     10 #define mozilla_dom_MediaQueryList_h
     11 
     12 #include "mozilla/DOMEventTargetHelper.h"
     13 #include "mozilla/LinkedList.h"
     14 #include "mozilla/dom/MediaQueryListBinding.h"
     15 #include "nsCOMPtr.h"
     16 #include "nsCycleCollectionParticipant.h"
     17 #include "nsISupports.h"
     18 #include "nsTArray.h"
     19 #include "nsWrapperCache.h"
     20 
     21 namespace mozilla::dom {
     22 
     23 class MediaList;
     24 
     25 class MediaQueryList final : public DOMEventTargetHelper,
     26                             public LinkedListElement<MediaQueryList> {
     27 public:
     28  // The caller who constructs is responsible for calling Evaluate
     29  // before calling any other methods.
     30  MediaQueryList(Document* aDocument, const nsACString& aMediaQueryList,
     31                 CallerType);
     32 
     33 private:
     34  ~MediaQueryList();
     35 
     36 public:
     37  NS_DECL_ISUPPORTS_INHERITED
     38  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(MediaQueryList, DOMEventTargetHelper)
     39 
     40  nsISupports* GetParentObject() const;
     41 
     42  void MediaFeatureValuesChanged();
     43 
     44  // Returns whether we need to notify of the change by dispatching a change
     45  // event.
     46  [[nodiscard]] bool EvaluateOnRenderingUpdate();
     47  void FireChangeEvent();
     48 
     49  JSObject* WrapObject(JSContext* aCx,
     50                       JS::Handle<JSObject*> aGivenProto) override;
     51 
     52  // WebIDL methods
     53  void GetMedia(nsACString& aMedia) const;
     54  bool Matches();
     55  void AddListener(EventListener* aListener);
     56  void RemoveListener(EventListener* aListener);
     57 
     58  IMPL_EVENT_HANDLER(change)
     59 
     60  bool HasListeners() const;
     61 
     62  void Disconnect();
     63 
     64  size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;
     65 
     66 private:
     67  void LastRelease() final {
     68    auto* listElement = static_cast<LinkedListElement<MediaQueryList>*>(this);
     69    if (listElement->isInList()) {
     70      listElement->remove();
     71    }
     72  }
     73 
     74  void RecomputeMatches();
     75 
     76  // We only need a pointer to the document to support lazy
     77  // reevaluation following dynamic changes.  However, this lazy
     78  // reevaluation is perhaps somewhat important, since some usage
     79  // patterns may involve the creation of large numbers of
     80  // MediaQueryList objects which almost immediately become garbage
     81  // (after a single call to the .matches getter).
     82  //
     83  // This pointer does make us a little more dependent on cycle
     84  // collection.
     85  //
     86  // We have a non-null mDocument for our entire lifetime except
     87  // after cycle collection unlinking.  Having a non-null mDocument
     88  // is equivalent to being in that document's mDOMMediaQueryLists
     89  // linked list.
     90  RefPtr<Document> mDocument;
     91  const RefPtr<const MediaList> mMediaList;
     92  // Whether our MediaList depends on our viewport size. Our medialist is
     93  // immutable, so we can just compute this once and carry on with our lives.
     94  const bool mViewportDependent : 1;
     95  // The matches state.
     96  // https://drafts.csswg.org/cssom-view/#mediaquerylist-matches-state
     97  bool mMatches : 1;
     98  // The value of the matches state on creation, or on the last rendering
     99  // update, in order to implement:
    100  // https://drafts.csswg.org/cssom-view/#evaluate-media-queries-and-report-changes
    101  bool mMatchesOnRenderingUpdate : 1;
    102 };
    103 
    104 }  // namespace mozilla::dom
    105 
    106 #endif /* !defined(mozilla_dom_MediaQueryList_h) */