dom/base/ImageTracker.h

   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 /* table of images used in a document, for batch locking/unlocking and
   8  * animating */
   9
  10 #ifndef mozilla_dom_ImageTracker
  11 #define mozilla_dom_ImageTracker
  12
  13 #include "nsTHashMap.h"
  14 #include "nsHashKeys.h"
  15
  16 class imgIRequest;
  17 namespace mozilla {
  18 struct MediaFeatureChange;
  19 }
  20
  21 namespace mozilla {
  22 namespace dom {
  23
  24 /*
  25  * Image Tracking
  26  *
  27  * Style and content images register their imgIRequests with their document's
  28  * image tracker, so that we can efficiently tell all descendant images when
  29  * they are and are not visible. When an image is on-screen, we want to call
  30  * LockImage() on it so that it doesn't do things like discarding frame data
  31  * to save memory. The PresShell informs its document's image tracker whether
  32  * its images should be locked or not via SetLockingState().
  33  *
  34  * See bug 512260.
  35  */
  36 class ImageTracker {
  37  public:
  38   ImageTracker();
  39   ImageTracker(const ImageTracker&) = delete;
  40   ImageTracker& operator=(const ImageTracker&) = delete;
  41
  42   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ImageTracker)
  43
  44   nsresult Add(imgIRequest* aImage);
  45
  46   enum { REQUEST_DISCARD = 0x1 };
  47   nsresult Remove(imgIRequest* aImage, uint32_t aFlags = 0);
  48
  49   // Makes the images on this document locked/unlocked. By default, the locking
  50   // state is unlocked/false.
  51   nsresult SetLockingState(bool aLocked);
  52
  53   // Makes the images on this document capable of having their animation
  54   // active or suspended. An Image will animate as long as at least one of its
  55   // owning Documents needs it to animate; otherwise it can suspend.
  56   void SetAnimatingState(bool aAnimating);
  57
  58   void RequestDiscardAll();
  59   void MediaFeatureValuesChangedAllDocuments(const MediaFeatureChange&);
  60
  61  private:
  62   ~ImageTracker();
  63
  64   nsTHashMap<nsPtrHashKey<imgIRequest>, uint32_t> mImages;
  65   bool mLocking;
  66   bool mAnimating;
  67 };
  68
  69 }  // namespace dom
  70 }  // namespace mozilla
  71
  72 #endif  // mozilla_dom_ImageTracker