layout/style/MediaQueryList.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
   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 "nsISupports.h"
  13 #include "nsCycleCollectionParticipant.h"
  14 #include "nsAutoPtr.h"
  15 #include "nsCOMPtr.h"
  16 #include "nsTArray.h"
  17 #include "prclist.h"
  18 #include "mozilla/Attributes.h"
  19 #include "nsWrapperCache.h"
  20 #include "mozilla/dom/MediaQueryListBinding.h"
  21
  22 class nsIDocument;
  23 class nsMediaList;
  24
  25 namespace mozilla {
  26 namespace dom {
  27
  28 class MediaQueryList MOZ_FINAL : public nsISupports,
  29                                  public nsWrapperCache,
  30                                  public PRCList
  31 {
  32 public:
  33   // The caller who constructs is responsible for calling Evaluate
  34   // before calling any other methods.
  35   MediaQueryList(nsIDocument *aDocument,
  36                  const nsAString &aMediaQueryList);
  37 private:
  38   ~MediaQueryList();
  39
  40 public:
  41   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
  42   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(MediaQueryList)
  43
  44   nsISupports* GetParentObject() const;
  45
  46   struct HandleChangeData {
  47     nsRefPtr<MediaQueryList> mql;
  48     nsRefPtr<mozilla::dom::MediaQueryListListener> callback;
  49   };
  50
  51   typedef FallibleTArray< nsRefPtr<mozilla::dom::MediaQueryListListener> > CallbackList;
  52   typedef FallibleTArray<HandleChangeData> NotifyList;
  53
  54   // Appends listeners that need notification to aListenersToNotify
  55   void MediumFeaturesChanged(NotifyList &aListenersToNotify);
  56
  57   bool HasListeners() const { return !mCallbacks.IsEmpty(); }
  58
  59   void RemoveAllListeners();
  60
  61   JSObject* WrapObject(JSContext* aCx) MOZ_OVERRIDE;
  62
  63   // WebIDL methods
  64   void GetMedia(nsAString& aMedia);
  65   bool Matches();
  66   void AddListener(mozilla::dom::MediaQueryListListener& aListener);
  67   void RemoveListener(mozilla::dom::MediaQueryListListener& aListener);
  68
  69 private:
  70   void RecomputeMatches();
  71
  72   // We only need a pointer to the document to support lazy
  73   // reevaluation following dynamic changes.  However, this lazy
  74   // reevaluation is perhaps somewhat important, since some usage
  75   // patterns may involve the creation of large numbers of
  76   // MediaQueryList objects which almost immediately become garbage
  77   // (after a single call to the .matches getter).
  78   //
  79   // This pointer does make us a little more dependent on cycle
  80   // collection.
  81   //
  82   // We have a non-null mDocument for our entire lifetime except
  83   // after cycle collection unlinking.  Having a non-null mDocument
  84   // is equivalent to being in that document's mDOMMediaQueryLists
  85   // linked list.
  86   nsCOMPtr<nsIDocument> mDocument;
  87
  88   nsRefPtr<nsMediaList> mMediaList;
  89   bool mMatches;
  90   bool mMatchesValid;
  91   CallbackList mCallbacks;
  92 };
  93
  94 } // namespace dom
  95 } // namespace mozilla
  96
  97 #endif /* !defined(mozilla_dom_MediaQueryList_h) */