1 files changed, 167 insertions, 0 deletions
diff --git a/dom/base/ImageTracker.cpp b/dom/base/ImageTracker.cpp
new file mode 100644
index 0000000000..d7ba03f02d
--- /dev/null
+++ b/dom/base/ImageTracker.cpp
@@ -0,0 +1,167 @@
+/* -*- 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 */
+
+#include "ImageTracker.h"
+
+#include "imgIContainer.h"
+#include "imgIRequest.h"
+#include "mozilla/Preferences.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla::dom {
+
+ImageTracker::ImageTracker() : mLocking(false), mAnimating(true) {}
+
+ImageTracker::~ImageTracker() { SetLockingState(false); }
+
+nsresult ImageTracker::Add(imgIRequest* aImage) {
+  MOZ_ASSERT(aImage);
+
+  nsresult rv = NS_OK;
+  auto entry = mImages.LookupForAdd(aImage);
+  if (entry) {
+    // The image is already in the hashtable.  Increment its count.
+    uint32_t oldCount = entry.Data();
+    MOZ_ASSERT(oldCount > 0, "Entry in the image tracker with count 0!");
+    entry.Data() = oldCount + 1;
+  } else {
+    // A new entry was inserted - set the count to 1.
+    entry.OrInsert([]() { return 1; });
+
+    // If we're locking images, lock this image too.
+    if (mLocking) {
+      rv = aImage->LockImage();
+    }
+
+    // If we're animating images, request that this image be animated too.
+    if (mAnimating) {
+      nsresult rv2 = aImage->IncrementAnimationConsumers();
+      rv = NS_SUCCEEDED(rv) ? rv2 : rv;
+    }
+  }
+
+  return rv;
+}
+
+nsresult ImageTracker::Remove(imgIRequest* aImage, uint32_t aFlags) {
+  NS_ENSURE_ARG_POINTER(aImage);
+
+  // Get the old count. It should exist and be > 0.
+  if (auto entry = mImages.Lookup(aImage)) {
+    MOZ_ASSERT(entry.Data() > 0, "Entry in the image tracker with count 0!");
+    // If the count becomes zero, remove it from the tracker.
+    if (--entry.Data() == 0) {
+      entry.Remove();
+    } else {
+      return NS_OK;
+    }
+  } else {
+    MOZ_ASSERT_UNREACHABLE("Removing image that wasn't in the tracker!");
+    return NS_OK;
+  }
+
+  nsresult rv = NS_OK;
+
+  // Now that we're no longer tracking this image, unlock it if we'd
+  // previously locked it.
+  if (mLocking) {
+    rv = aImage->UnlockImage();
+  }
+
+  // If we're animating images, remove our request to animate this one.
+  if (mAnimating) {
+    nsresult rv2 = aImage->DecrementAnimationConsumers();
+    rv = NS_SUCCEEDED(rv) ? rv2 : rv;
+  }
+
+  if (aFlags & REQUEST_DISCARD) {
+    // Request that the image be discarded if nobody else holds a lock on it.
+    // Do this even if !mLocking, because even if we didn't just unlock
+    // this image, it might still be a candidate for discarding.
+    aImage->RequestDiscard();
+  }
+
+  return rv;
+}
+
+nsresult ImageTracker::SetLockingState(bool aLocked) {
+  if (XRE_IsContentProcess() &&
+      !Preferences::GetBool("image.mem.allow_locking_in_content_processes",
+                            true)) {
+    return NS_OK;
+  }
+
+  // If there's no change, there's nothing to do.
+  if (mLocking == aLocked) return NS_OK;
+
+  // Otherwise, iterate over our images and perform the appropriate action.
+  for (auto iter = mImages.Iter(); !iter.Done(); iter.Next()) {
+    imgIRequest* image = iter.Key();
+    if (aLocked) {
+      image->LockImage();
+    } else {
+      image->UnlockImage();
+    }
+  }
+
+  // Update state.
+  mLocking = aLocked;
+
+  return NS_OK;
+}
+
+void ImageTracker::SetAnimatingState(bool aAnimating) {
+  // If there's no change, there's nothing to do.
+  if (mAnimating == aAnimating) return;
+
+  // Otherwise, iterate over our images and perform the appropriate action.
+  for (auto iter = mImages.Iter(); !iter.Done(); iter.Next()) {
+    imgIRequest* image = iter.Key();
+    if (aAnimating) {
+      image->IncrementAnimationConsumers();
+    } else {
+      image->DecrementAnimationConsumers();
+    }
+  }
+
+  // Update state.
+  mAnimating = aAnimating;
+}
+
+void ImageTracker::RequestDiscardAll() {
+  for (auto iter = mImages.Iter(); !iter.Done(); iter.Next()) {
+    iter.Key()->RequestDiscard();
+  }
+}
+
+void ImageTracker::MediaFeatureValuesChangedAllDocuments(
+    const MediaFeatureChange& aChange) {
+  // Inform every content image used in the document that media feature values
+  // have changed.  If the same image is used in multiple places, then we can
+  // end up informing them multiple times.  Theme changes are rare though and we
+  // don't bother trying to ensure we only do this once per image.
+  //
+  // Pull the images out into an array and iterate over them, in case the
+  // image notifications do something that ends up modifying the table.
+  nsTArray<nsCOMPtr<imgIContainer>> images;
+  for (auto iter = mImages.Iter(); !iter.Done(); iter.Next()) {
+    imgIRequest* req = iter.Key();
+    nsCOMPtr<imgIContainer> image;
+    req->GetImage(getter_AddRefs(image));
+    if (!image) {
+      continue;
+    }
+    images.AppendElement(image->Unwrap());
+  }
+  for (imgIContainer* image : images) {
+    image->MediaFeatureValuesChangedAllDocuments(aChange);
+  }
+}
+
+}  // namespace mozilla::dom