Detect change on video/viewport intersection when rendered remotely

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
index dcf3d60f9d3a77daeb6ba5f0f05e3c4c7e30e025..8ebf80990d836b331943b0a6fb81b7e13de61a81 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -128,6 +128,7 @@ namespace {
 
 constexpr float kMostlyFillViewportThreshold = 0.85f;
 constexpr double kMostlyFillViewportBecomeStableSeconds = 5;
+constexpr double kCheckIntersectWhenPausedIntervalInSeconds = 2;

[miu, 2016/12/10 02:18:37]

If the "stable" check is 5 seconds, the timer interval should be something that
is zero modulo 5 seconds: Probably 1 second would be fine.

[xjz, 2016/12/12 18:58:45]

Done.

 
 enum MediaControlsShow {
   MediaControlsShowAttribute = 0,
@@ -370,6 +371,9 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName,
       m_viewportFillDebouncerTimer(
           this,
           &HTMLMediaElement::viewportFillDebouncerTimerFired),
+      m_checkIntersectionWhenPausedTimer(
+          this,
+          &HTMLMediaElement::checkIntersectionWhenPausedTimerFired),
       m_playedTimeRanges(),
       m_asyncEventQueue(GenericEventQueue::create(this)),
       m_playbackRate(1.0f),
@@ -3254,6 +3258,7 @@ void HTMLMediaElement::updatePlayState() {
       webMediaPlayer()->play();
     }
 
+    m_checkIntersectionWhenPausedTimer.stop();
     startPlaybackProgressTimer();
     m_playing = true;
   } else {  // Should not be playing right now
@@ -3262,6 +3267,7 @@ void HTMLMediaElement::updatePlayState() {
     }
 
     m_playbackProgressTimer.stop();
+    startCheckIntersectionWhenPausedTimer();
     m_playing = false;
     double time = currentTime();
     if (time > m_lastSeekTime)
@@ -3275,6 +3281,7 @@ void HTMLMediaElement::updatePlayState() {
 void HTMLMediaElement::stopPeriodicTimers() {
   m_progressEventTimer.stop();
   m_playbackProgressTimer.stop();
+  m_checkIntersectionWhenPausedTimer.stop();

[miu, 2016/12/10 02:18:37]

If you take my advice below, this extra stop() call here becomes unnecessary.

[xjz, 2016/12/12 18:58:45]

Done.

 }
 
 void HTMLMediaElement::
@@ -4033,8 +4040,13 @@ DEFINE_TRACE(HTMLMediaElement::AudioSourceProviderImpl) {
   visitor->trace(m_client);
 }
 
+void HTMLMediaElement::enableMonitorViewportIntersection(bool enable) {
+  m_enableMonitorViewportIntersection = enable;

[miu, 2016/12/10 02:18:37]

IMHO, this would all be simpler if we didn't have two different timers that
might call checkViewportIntersectionChanged(). Let's just have one and then:

1. Rename m_checkIntersectionWhenPausedTimer to just
m_checkViewportIntersectionTimer.

2. Get rid of the m_enableMonitorViewportIntersection boolean.

3. Only call start() or stop() on the timer from
enableMonitorViewportIntersection():

  void HTMLMediaElement::enableMonitorViewportIntersection(bool enable) {
    if (enable && !m_checkViewportIntersectionTimer.isActive())
      m_checkViewportIntersectionTimer.startRepeating(...);
    else if (!enable)
      m_checkViewportIntersectionTimer.stop();
  }

[xjz, 2016/12/12 18:58:45]

Done.

+}
+
 void HTMLMediaElement::checkViewportIntersectionChanged() {
-  // TODO(xjz): Early return if we not in tab mirroring.
+  if (!m_enableMonitorViewportIntersection)
+    return;
 
   IntersectionGeometry geometry(
       document().frame()->localFrameRoot()->document(), this, Vector<Length>(),
@@ -4071,4 +4083,16 @@ void HTMLMediaElement::viewportFillDebouncerTimerFired(TimerBase*) {
     m_webMediaPlayer->becameDominantVisibleContent(m_mostlyFillingViewport);
 }
 
+void HTMLMediaElement::checkIntersectionWhenPausedTimerFired(TimerBase*) {
+  checkViewportIntersectionChanged();
+}
+
+void HTMLMediaElement::startCheckIntersectionWhenPausedTimer() {
+  if (m_checkIntersectionWhenPausedTimer.isActive())
+    return;
+
+  m_checkIntersectionWhenPausedTimer.startRepeating(
+      kCheckIntersectWhenPausedIntervalInSeconds, BLINK_FROM_HERE);
+}
+
 }  // namespace blink