Quelle ImageTracker.h Sprache: C

/* -*- 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/. */

/* table of images used in a document, for batch locking/unlocking and
* animating */

#ifndef mozilla_dom_ImageTracker
#define mozilla_dom_ImageTracker

#include "nsTHashMap.h"
#include "nsHashKeys.h"

class imgIRequest;
namespace mozilla {
struct MediaFeatureChange;
}

namespace mozilla::dom {

/*
* Image Tracking
*
* Style and content images register their imgIRequests with their document's
* image tracker, so that we can efficiently tell all descendant images when
* they are and are not visible. When an image is on-screen, we want to call
* LockImage() on it so that it doesn't do things like discarding frame data
* to save memory. The PresShell informs its document's image tracker whether
* its images should be locked or not via SetLockingState().
*
* See bug 512260.
*/
class ImageTracker {
public:
  ImageTracker();
  ImageTracker(const ImageTracker&) = delete;
  ImageTracker& operator=(const ImageTracker&) = delete;

  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ImageTracker)

  nsresult Add(imgIRequest* aImage);

  enum { REQUEST_DISCARD = 0x1 };
  nsresult Remove(imgIRequest* aImage, uint32_t aFlags = 0);

  // Makes the images on this document locked/unlocked. By default, the locking
  // state is unlocked/false.
  void SetLockingState(bool aLocked);
  bool GetLockingState() const { return mLocking; }

  // Makes the images on this document capable of having their animation
  // active or suspended. An Image will animate as long as at least one of its
  // owning Documents needs it to animate; otherwise it can suspend.
  void SetAnimatingState(bool aAnimating);

  void RequestDiscardAll();
  void MediaFeatureValuesChangedAllDocuments(const MediaFeatureChange&);

private:
  ~ImageTracker();

  nsTHashMap<nsPtrHashKey<imgIRequest>, uint32_t> mImages;
  bool mLocking = false;
  bool mAnimating = true;
};

}  // namespace mozilla::dom

#endif  // mozilla_dom_ImageTracker

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