palemoon-dev/platform/layout/style/MediaQueryList.h

/* -*- Mode: C++; 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/. */

/* 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 "prclist.h"
#include "mozilla/Attributes.h"
#include "nsWrapperCache.h"
#include "mozilla/DOMEventTargetHelper.h"
#include "mozilla/dom/MediaQueryListBinding.h"

class nsIDocument;
class nsMediaList;

namespace mozilla {
namespace dom {

class MediaQueryList final : public DOMEventTargetHelper,
                             public PRCList
{
public:
  // The caller who constructs is responsible for calling Evaluate
  // before calling any other methods.
  MediaQueryList(nsIDocument *aDocument,
                 const nsAString &aMediaQueryList);
private:
  ~MediaQueryList();

public:
  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(MediaQueryList, DOMEventTargetHelper)

  nsISupports* GetParentObject() const;

  void MaybeNotify();

  JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;

  // WebIDL methods
  void GetMedia(nsAString& aMedia);
  bool Matches();
  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
  // 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.
  nsCOMPtr<nsIDocument> mDocument;

  RefPtr<nsMediaList> mMediaList;
  bool mMatches;
  bool mMatchesValid;
  bool mIsKeptAlive;
};

} // namespace dom
} // namespace mozilla

#endif /* !defined(mozilla_dom_MediaQueryList_h) */