Detect change on the intersection of video and viewport.

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

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 21 matching lines @@
 #include "bindings/core/v8/ScriptController.h"
 #include "bindings/core/v8/ScriptEventListener.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/HTMLNames.h"
 #include "core/css/MediaList.h"
 #include "core/dom/Attribute.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/ElementVisibilityObserver.h"
 #include "core/dom/Fullscreen.h"
+#include "core/dom/IntersectionGeometry.h"
 #include "core/dom/TaskRunnerHelper.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/events/Event.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/frame/UseCounter.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/html/AutoplayUmaHelper.h"
 #include "core/html/HTMLMediaSource.h"
@@ skipping 67 matching lines @@
 namespace blink {
 
 using namespace HTMLNames;
 
 using WeakMediaElementSet = HeapHashSet<WeakMember<HTMLMediaElement>>;
 using DocumentElementSetMap =
     HeapHashMap<WeakMember<Document>, Member<WeakMediaElementSet>>;
 
 namespace {
 
+constexpr int64_t kOneHundredPercent = 100;
+constexpr int64_t kMostlyFillViewportThresholdPercent = 85;
+constexpr double kMostlyFillViewportBecomeStableTime = 5;

[ojan, 2016/11/24 00:48:33]

Nit: I generally prefer time values to say the unit of time to be extra clear.
So, I'd make this kMostlyFillViewportBecomeStableSeconds.

[xjz, 2016/11/24 02:16:16]

Done.

+
 enum MediaControlsShow {
   MediaControlsShowAttribute = 0,
   MediaControlsShowFullscreen,
   MediaControlsShowNoScript,
   MediaControlsShowNotShown,
   MediaControlsShowMax
 };
 
 String urlForLoggingMedia(const KURL& url) {
   static const unsigned maximumURLLengthForLogging = 128;
@@ skipping 264 matching lines @@
 HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName,
                                    Document& document)
     : HTMLElement(tagName, document),
       ActiveScriptWrappable(this),
       ActiveDOMObject(&document),
       m_loadTimer(this, &HTMLMediaElement::loadTimerFired),
       m_progressEventTimer(this, &HTMLMediaElement::progressEventTimerFired),
       m_playbackProgressTimer(this,
                               &HTMLMediaElement::playbackProgressTimerFired),
       m_audioTracksTimer(this, &HTMLMediaElement::audioTracksTimerFired),
+      m_viewportFillDebouncerTimer(
+          this,
+          &HTMLMediaElement::viewportFillDebouncerTimerFired),
       m_playedTimeRanges(),
       m_asyncEventQueue(GenericEventQueue::create(this)),
       m_playbackRate(1.0f),
       m_defaultPlaybackRate(1.0f),
       m_networkState(kNetworkEmpty),
       m_readyState(kHaveNothing),
       m_readyStateMaximum(kHaveNothing),
       m_volume(1.0f),
       m_lastSeekTime(0),
       m_previousProgressTime(std::numeric_limits<double>::max()),
@@ skipping 762 matching lines @@
   // wrapper.
   m_audioSourceProvider.wrap(m_webMediaPlayer->getAudioSourceProvider());
   m_webMediaPlayer->setVolume(effectiveMediaVolume());
 
   m_webMediaPlayer->setPoster(posterImageURL());
 
   m_webMediaPlayer->setPreload(effectivePreloadType());
 
   m_webMediaPlayer->load(loadType(), source, corsMode());
 
+  m_webMediaPlayer->stablyFilledMostViewport(m_mostlyFillingViewport);
+
   if (isFullscreen()) {
     // This handles any transition to or from fullscreen overlay mode.
     frame->chromeClient().enterFullscreenForElement(this);
   }
 }
 
 void HTMLMediaElement::setPlayerPreload() {
   if (m_webMediaPlayer)
     m_webMediaPlayer->setPreload(effectivePreloadType());
 
@@ skipping 1292 matching lines @@
 void HTMLMediaElement::startPlaybackProgressTimer() {
   if (m_playbackProgressTimer.isActive())
     return;
 
   m_previousProgressTime = WTF::currentTime();
   m_playbackProgressTimer.startRepeating(maxTimeupdateEventFrequency,
                                          BLINK_FROM_HERE);
 }
 
 void HTMLMediaElement::playbackProgressTimerFired(TimerBase*) {
+  checkViewportIntersectionChanged();
+
   if (!std::isnan(m_fragmentEndTime) && currentTime() >= m_fragmentEndTime &&
       getDirectionOfPlayback() == Forward) {
     m_fragmentEndTime = std::numeric_limits<double>::quiet_NaN();
     if (!m_paused) {
       UseCounter::count(document(),
                         UseCounter::HTMLMediaElementPauseAtFragmentEnd);
       // changes paused to true and fires a simple event named pause at the
       // media element.
       pauseInternal();
     }
@@ skipping 1669 matching lines @@
 }
 
 IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect()
     const {
   IntRect result;
   if (LayoutObject* object = m_element->layoutObject())
     result = object->absoluteBoundingBoxRect();
   return result;
 }
 
+void HTMLMediaElement::checkViewportIntersectionChanged() {

[ojan, 2016/11/24 00:48:33]

Can we early return if we're not tab casting so we only need to do this work
when tab casting? The intersection work isn't *very* expensive, but it's not
cheap either.

Looks like we don't plumb that data in today, but I think it should be possible
to via RemoteRenderingController? In either case, putting a TODO and doing so a
followup patch would be fine.

[xjz, 2016/11/24 02:16:16]

Add TODO comment for now. Will see if this can be resolved in a follow-up CL.

+  ExecutionContext* context = getExecutionContext();
+  DCHECK(context->isDocument());
+  Document& document = toDocument(*context);
+  IntersectionGeometry geometry(&document, this, Vector<Length>(), true);

[ojan, 2016/11/24 00:48:33]

Now that you're in the HTMLElement world, you can get to the document more
directly with document(). 

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/Node....

Also, we generally try to avoid boolean arguments to functions unless it's
obvious what the bool is because it makes it hard to know what they are. From
the C++ style guide "Consider changing the function signature to replace a bool
argument with an enum argument. This will make the argument values
self-describing."

The typical solution here is to create an enum:
enum class IntersectionGeometryBounds {
  kShouldReportRootBounds,
  kShouldNotReportRootBounds,
}

[xjz, 2016/11/24 02:16:16]

Done. Name the enum as ReportRootBounds.

+  geometry.computeGeometry();
+  IntRect intersectRect = geometry.intersectionIntRect();
+  if (m_currentIntersectRect == intersectRect)
+    return;
+
+  m_currentIntersectRect = intersectRect;
+  // Reset on any intersection change, since this indicates the user is
+  // scrolling around in the document, the document is changing layout, etc.
+  m_viewportFillDebouncerTimer.stop();
+  bool isMostlyFillingViewport =
+      (kOneHundredPercent * m_currentIntersectRect.size().area() >
+       kMostlyFillViewportThresholdPercent *

[ojan, 2016/11/24 00:48:33]

Nit: If you make this kMostlyFillViewportThreshold and have the value be 0.85
instead of 85, then you can avoid needing the kOneHundredPercent value at all.

[xjz, 2016/11/24 02:16:16]

Done. 

+           geometry.rootIntRect().size().area());
+  if (m_mostlyFillingViewport == isMostlyFillingViewport)
+    return;
+
+  if (!isMostlyFillingViewport) {
+    m_mostlyFillingViewport = isMostlyFillingViewport;
+    if (m_webMediaPlayer)
+      m_webMediaPlayer->stablyFilledMostViewport(false);

[ojan, 2016/11/24 00:48:33]

Nit: It took me a bit to understand these few lines. Partially it's because you
use false here and isMostlyFillingViewport on line 4230. Either way is fine, but
it would make the code easier to read if you either use false in both places or
isMostlyFillingViewport in both places.

[xjz, 2016/11/24 02:16:16]

Done.

+    return;
+  }
+
+  m_viewportFillDebouncerTimer.startOneShot(kMostlyFillViewportBecomeStableTime,
+                                            BLINK_FROM_HERE);

[ojan, 2016/11/24 00:48:33]

Indentation is off here. FWIW, I haven't used it much, but a lot of people use
"git cl format" to have git cl fix these sorts of issues for them instead of
doing it manually.

[xjz, 2016/11/24 02:16:16]

I always do "git cl format". Is the "indentation" here not correct? Anyway,
after renaming |kMostlyFillViewportBecomeStableTime|, this is not applicable.

+}
+
+void HTMLMediaElement::viewportFillDebouncerTimerFired(TimerBase*) {
+  m_mostlyFillingViewport = true;
+  if (m_webMediaPlayer)
+    m_webMediaPlayer->stablyFilledMostViewport(true);
+}
+
 }  // namespace blink