dom/media/BackgroundVideoDecodingPermissionObserver.cpp

   1 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "BackgroundVideoDecodingPermissionObserver.h"
   7
   8 #include "mozilla/AsyncEventDispatcher.h"
   9 #include "mozilla/dom/BrowsingContext.h"
  10 #include "mozilla/StaticPrefs_media.h"
  11 #include "MediaDecoder.h"
  12 #include "nsContentUtils.h"
  13 #include "mozilla/dom/Document.h"
  14 #include "mozilla/Services.h"
  15 #include "nsIObserverService.h"
  16
  17 namespace mozilla {
  18
  19 BackgroundVideoDecodingPermissionObserver::
  20     BackgroundVideoDecodingPermissionObserver(MediaDecoder* aDecoder)
  21     : mDecoder(aDecoder), mIsRegisteredForEvent(false) {
  22   MOZ_ASSERT(mDecoder);
  23 }
  24
  25 NS_IMETHODIMP
  26 BackgroundVideoDecodingPermissionObserver::Observe(nsISupports* aSubject,
  27                                                    const char* aTopic,
  28                                                    const char16_t* aData) {
  29   if (!StaticPrefs::media_resume_background_video_on_tabhover()) {
  30     return NS_OK;
  31   }
  32
  33   if (!IsValidEventSender(aSubject)) {
  34     return NS_OK;
  35   }
  36
  37   if (strcmp(aTopic, "unselected-tab-hover") == 0) {
  38     bool allowed = !NS_strcmp(aData, u"true");
  39     mDecoder->SetIsBackgroundVideoDecodingAllowed(allowed);
  40   }
  41   return NS_OK;
  42 }
  43
  44 void BackgroundVideoDecodingPermissionObserver::RegisterEvent() {
  45   MOZ_ASSERT(!mIsRegisteredForEvent);
  46   nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
  47   if (observerService) {
  48     observerService->AddObserver(this, "unselected-tab-hover", false);
  49     mIsRegisteredForEvent = true;
  50     if (nsContentUtils::IsInStableOrMetaStableState()) {
  51       // Events shall not be fired synchronously to prevent anything visible
  52       // from the scripts while we are in stable state.
  53       if (nsCOMPtr<dom::Document> doc = GetOwnerDoc()) {
  54         doc->Dispatch(NewRunnableMethod(
  55             "BackgroundVideoDecodingPermissionObserver::EnableEvent", this,
  56             &BackgroundVideoDecodingPermissionObserver::EnableEvent));
  57       }
  58     } else {
  59       EnableEvent();
  60     }
  61   }
  62 }
  63
  64 void BackgroundVideoDecodingPermissionObserver::UnregisterEvent() {
  65   MOZ_ASSERT(mIsRegisteredForEvent);
  66   nsCOMPtr<nsIObserverService> observerService = services::GetObserverService();
  67   if (observerService) {
  68     observerService->RemoveObserver(this, "unselected-tab-hover");
  69     mIsRegisteredForEvent = false;
  70     mDecoder->SetIsBackgroundVideoDecodingAllowed(false);
  71     if (nsContentUtils::IsInStableOrMetaStableState()) {
  72       // Events shall not be fired synchronously to prevent anything visible
  73       // from the scripts while we are in stable state.
  74       if (nsCOMPtr<dom::Document> doc = GetOwnerDoc()) {
  75         doc->Dispatch(NewRunnableMethod(
  76             "BackgroundVideoDecodingPermissionObserver::DisableEvent", this,
  77             &BackgroundVideoDecodingPermissionObserver::DisableEvent));
  78       }
  79     } else {
  80       DisableEvent();
  81     }
  82   }
  83 }
  84
  85 BackgroundVideoDecodingPermissionObserver::
  86     ~BackgroundVideoDecodingPermissionObserver() {
  87   MOZ_ASSERT(!mIsRegisteredForEvent);
  88 }
  89
  90 void BackgroundVideoDecodingPermissionObserver::EnableEvent() const {
  91   // If we can't get document or outer window, then you can't reach the chrome
  92   // <browser> either, so we don't need want to dispatch the event.
  93   dom::Document* doc = GetOwnerDoc();
  94   if (!doc || !doc->GetWindow()) {
  95     return;
  96   }
  97
  98   RefPtr<AsyncEventDispatcher> asyncDispatcher =
  99       new AsyncEventDispatcher(doc, u"UnselectedTabHover:Enable"_ns,
 100                                CanBubble::eYes, ChromeOnlyDispatch::eYes);
 101   asyncDispatcher->PostDOMEvent();
 102 }
 103
 104 void BackgroundVideoDecodingPermissionObserver::DisableEvent() const {
 105   // If we can't get document or outer window, then you can't reach the chrome
 106   // <browser> either, so we don't need want to dispatch the event.
 107   dom::Document* doc = GetOwnerDoc();
 108   if (!doc || !doc->GetWindow()) {
 109     return;
 110   }
 111
 112   RefPtr<AsyncEventDispatcher> asyncDispatcher =
 113       new AsyncEventDispatcher(doc, u"UnselectedTabHover:Disable"_ns,
 114                                CanBubble::eYes, ChromeOnlyDispatch::eYes);
 115   asyncDispatcher->PostDOMEvent();
 116 }
 117
 118 dom::BrowsingContext* BackgroundVideoDecodingPermissionObserver::GetOwnerBC()
 119     const {
 120   dom::Document* doc = GetOwnerDoc();
 121   return doc ? doc->GetBrowsingContext() : nullptr;
 122 }
 123
 124 dom::Document* BackgroundVideoDecodingPermissionObserver::GetOwnerDoc() const {
 125   if (!mDecoder->GetOwner()) {
 126     return nullptr;
 127   }
 128
 129   return mDecoder->GetOwner()->GetDocument();
 130 }
 131
 132 bool BackgroundVideoDecodingPermissionObserver::IsValidEventSender(
 133     nsISupports* aSubject) const {
 134   nsCOMPtr<nsPIDOMWindowInner> senderInner(do_QueryInterface(aSubject));
 135   if (!senderInner) {
 136     return false;
 137   }
 138
 139   RefPtr<dom::BrowsingContext> senderBC = senderInner->GetBrowsingContext();
 140   if (!senderBC) {
 141     return false;
 142   }
 143   // Valid sender should be in the same browsing context tree as where owner is.
 144   return GetOwnerBC() ? GetOwnerBC()->Top() == senderBC->Top() : false;
 145 }
 146
 147 NS_IMPL_ISUPPORTS(BackgroundVideoDecodingPermissionObserver, nsIObserver)
 148
 149 }  // namespace mozilla