1 files changed, 149 insertions, 0 deletions
diff --git a/dom/media/BackgroundVideoDecodingPermissionObserver.cpp b/dom/media/BackgroundVideoDecodingPermissionObserver.cpp
new file mode 100644
index 0000000000..f91629a090
--- /dev/null
+++ b/dom/media/BackgroundVideoDecodingPermissionObserver.cpp
@@ -0,0 +1,149 @@
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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/. */
+
+#include "BackgroundVideoDecodingPermissionObserver.h"
+
+#include "mozilla/AsyncEventDispatcher.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/StaticPrefs_media.h"
+#include "MediaDecoder.h"
+#include "nsContentUtils.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/Services.h"
+#include "nsIObserverService.h"
+
+namespace mozilla {
+
+BackgroundVideoDecodingPermissionObserver::
+    BackgroundVideoDecodingPermissionObserver(MediaDecoder* aDecoder)
+    : mDecoder(aDecoder), mIsRegisteredForEvent(false) {
+  MOZ_ASSERT(mDecoder);
+}
+
+NS_IMETHODIMP
+BackgroundVideoDecodingPermissionObserver::Observe(nsISupports* aSubject,
+                                                   const char* aTopic,
+                                                   const char16_t* aData) {
+  if (!StaticPrefs::media_resume_background_video_on_tabhover()) {
+    return NS_OK;
+  }
+
+  if (!IsValidEventSender(aSubject)) {
+    return NS_OK;
+  }
+
+  if (strcmp(aTopic, "unselected-tab-hover") == 0) {
+    bool allowed = !NS_strcmp(aData, u"true");
+    mDecoder->SetIsBackgroundVideoDecodingAllowed(allowed);
+  }
+  return NS_OK;
+}
+
+void BackgroundVideoDecodingPermissionObserver::RegisterEvent() {
+  MOZ_ASSERT(!mIsRegisteredForEvent);
+  nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
+  if (observerService) {
+    observerService->AddObserver(this, "unselected-tab-hover", false);
+    mIsRegisteredForEvent = true;
+    if (nsContentUtils::IsInStableOrMetaStableState()) {
+      // Events shall not be fired synchronously to prevent anything visible
+      // from the scripts while we are in stable state.
+      if (nsCOMPtr<dom::Document> doc = GetOwnerDoc()) {
+        doc->Dispatch(NewRunnableMethod(
+            "BackgroundVideoDecodingPermissionObserver::EnableEvent", this,
+            &BackgroundVideoDecodingPermissionObserver::EnableEvent));
+      }
+    } else {
+      EnableEvent();
+    }
+  }
+}
+
+void BackgroundVideoDecodingPermissionObserver::UnregisterEvent() {
+  MOZ_ASSERT(mIsRegisteredForEvent);
+  nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
+  if (observerService) {
+    observerService->RemoveObserver(this, "unselected-tab-hover");
+    mIsRegisteredForEvent = false;
+    mDecoder->SetIsBackgroundVideoDecodingAllowed(false);
+    if (nsContentUtils::IsInStableOrMetaStableState()) {
+      // Events shall not be fired synchronously to prevent anything visible
+      // from the scripts while we are in stable state.
+      if (nsCOMPtr<dom::Document> doc = GetOwnerDoc()) {
+        doc->Dispatch(NewRunnableMethod(
+            "BackgroundVideoDecodingPermissionObserver::DisableEvent", this,
+            &BackgroundVideoDecodingPermissionObserver::DisableEvent));
+      }
+    } else {
+      DisableEvent();
+    }
+  }
+}
+
+BackgroundVideoDecodingPermissionObserver::
+    ~BackgroundVideoDecodingPermissionObserver() {
+  MOZ_ASSERT(!mIsRegisteredForEvent);
+}
+
+void BackgroundVideoDecodingPermissionObserver::EnableEvent() const {
+  // If we can't get document or outer window, then you can't reach the chrome
+  // <browser> either, so we don't need want to dispatch the event.
+  dom::Document* doc = GetOwnerDoc();
+  if (!doc || !doc->GetWindow()) {
+    return;
+  }
+
+  RefPtr<AsyncEventDispatcher> asyncDispatcher =
+      new AsyncEventDispatcher(doc, u"UnselectedTabHover:Enable"_ns,
+                               CanBubble::eYes, ChromeOnlyDispatch::eYes);
+  asyncDispatcher->PostDOMEvent();
+}
+
+void BackgroundVideoDecodingPermissionObserver::DisableEvent() const {
+  // If we can't get document or outer window, then you can't reach the chrome
+  // <browser> either, so we don't need want to dispatch the event.
+  dom::Document* doc = GetOwnerDoc();
+  if (!doc || !doc->GetWindow()) {
+    return;
+  }
+
+  RefPtr<AsyncEventDispatcher> asyncDispatcher =
+      new AsyncEventDispatcher(doc, u"UnselectedTabHover:Disable"_ns,
+                               CanBubble::eYes, ChromeOnlyDispatch::eYes);
+  asyncDispatcher->PostDOMEvent();
+}
+
+dom::BrowsingContext* BackgroundVideoDecodingPermissionObserver::GetOwnerBC()
+    const {
+  dom::Document* doc = GetOwnerDoc();
+  return doc ? doc->GetBrowsingContext() : nullptr;
+}
+
+dom::Document* BackgroundVideoDecodingPermissionObserver::GetOwnerDoc() const {
+  if (!mDecoder->GetOwner()) {
+    return nullptr;
+  }
+
+  return mDecoder->GetOwner()->GetDocument();
+}
+
+bool BackgroundVideoDecodingPermissionObserver::IsValidEventSender(
+    nsISupports* aSubject) const {
+  nsCOMPtr<nsPIDOMWindowInner> senderInner(do_QueryInterface(aSubject));
+  if (!senderInner) {
+    return false;
+  }
+
+  RefPtr<dom::BrowsingContext> senderBC = senderInner->GetBrowsingContext();
+  if (!senderBC) {
+    return false;
+  }
+  // Valid sender should be in the same browsing context tree as where owner is.
+  return GetOwnerBC() ? GetOwnerBC()->Top() == senderBC->Top() : false;
+}
+
+NS_IMPL_ISUPPORTS(BackgroundVideoDecodingPermissionObserver, nsIObserver)
+
+}  // namespace mozilla