Support text track selection in video controls

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index 299905f7c3714f256eb3b03a50adc27a9ba2b08b..f0eff4daaf2170a1ee3acde177fd7c768f20507c 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -363,6 +363,7 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName, Document& docum
     , m_audioTracks(AudioTrackList::create(*this))
     , m_videoTracks(VideoTrackList::create(*this))
     , m_textTracks(nullptr)
+    , m_selectedTextTrack(nullptr)
 #if ENABLE(WEB_AUDIO)
     , m_audioSourceNode(nullptr)
 #endif
@@ -1167,6 +1168,23 @@ void HTMLMediaElement::textTrackModeChanged(TextTrack* track)
     textTracks()->scheduleChangeEvent();
 }
 
+void HTMLMediaElement::showTextTrackAtIndex(unsigned index)

[fs, 2015/04/14 12:34:56]

Any reason - m_selectedTextTrack excepted - to have this in HTMLMediaElement?

[srivats, 2015/04/16 23:37:19]

No. I moved this method to MediaControlElements and now I'm setting a bit to
prevent automatic track selection from happening when a track is selected by the
user.

+{
+    TextTrackList* trackList = textTracks();
+    if (!trackList || !trackList->length())
+        return;
+
+    for (unsigned i = 0; i < trackList->length(); ++i) {
+        TextTrack* track = trackList->item(i);
+        track->setMode(TextTrack::disabledKeyword());

[fs, 2015/04/14 12:34:56]

This ought to be more selective. I.e. only do this if the track is of a rendered
kind and "showing" - even the latter is not entirely obvious either.

[srivats, 2015/04/16 23:37:19]

By rendered tracks, are you referring to tracks with ready state LOADED? I added
a check to disable a track only if it's showing.

[fs, 2015/04/17 11:54:46]

No, I mean tracks that are either kind=subtitles or kind=captions. See for
instance TextTrack::isRendered(). Adding a new method "isVisual" or
"isRenderable" or something like that might make sense, and then you could use
that here.

Checking LOADED would not be appropriate, but it does add additional
complication since loading a track could fail, so tracks with readinessState()
== FailedToLoad should probably be excluded as well.

[srivats, 2015/04/21 01:48:55]

Done.

+    }
+
+    if (index < trackList->length()) {
+        m_selectedTextTrack = trackList->item(index);

[fs, 2015/04/14 12:34:56]

It feels a bit like this is only used to avoid running auto-selection - which a
single bit would suffice for (and IIRC that's what the spec has too.) The bits
involved in text track selection already are a bit of a mess though.
Quite possibly the bit could be set based on a gesture rather than a direct call
too.

[srivats, 2015/04/16 23:37:19]

Done.

+        m_selectedTextTrack->setMode(TextTrack::showingKeyword());
+    }
+}
+
 bool HTMLMediaElement::isSafeToLoadURL(const KURL& url, InvalidURLAction actionIfInvalid)
 {
     if (!url.isValid()) {
@@ -2481,6 +2499,12 @@ void HTMLMediaElement::honorUserPreferencesForAutomaticTextTrackSelection()
     if (!m_textTracks || !m_textTracks->length())
         return;
 
+    // If the user has selected a track to display, don't perform automatic selection
+    if (m_selectedTextTrack) {
+        m_selectedTextTrack->setMode(TextTrack::showingKeyword());
+        return;
+    }
+
     AutomaticTrackSelection::Configuration configuration;
     if (m_processingPreferenceChange)
         configuration.disableCurrentlyEnabledTracks = true;