1 files changed, 71 insertions, 0 deletions
diff --git a/dom/base/ImageTracker.h b/dom/base/ImageTracker.h
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+++ b/dom/base/ImageTracker.h
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+/* -*- 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