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Add MediaSession.activate()
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 * Let MediaSession.deactivate() return a promise.
 * Drop implicit activation and decativation for AudioContext.

Fixes w3c#50
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@foolip
foolip committed Sep 25, 2015
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170 changes: 77 additions & 93 deletions mediasession.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -215,7 +215,8 @@ conforming IDL fragments, as described in the Web IDL specification. [[!WEBIDL]]
interface MediaSession {
readonly attribute MediaSessionKind kind;

void deactivate();
Promise<void> activate();
Promise<void> deactivate();
};

enum MediaSessionKind {
Expand Down Expand Up @@ -243,14 +244,19 @@ sessions</dfn>.
<dd>
Returns the <a>media session</a>'s <a>kind</a>.
</dd>
<dt>
<code><var>session</var> . {{MediaSession/activate()}}</code>
</dt>
<dd>
Requests platform-level media focus and sets the <a>media session</a>'s
<a>state</a> to <code><a lt="active media session state">active</a></code>.
</dd>
<dt>
<code><var>session</var> . {{MediaSession/deactivate()}}</code>
</dt>
<dd>
Releases platform-level media focus, sets the <a>media session</a>'s
<a>state</a> to <code><a lt="idle media session state">idle</a></code> and
applies any changes necessary to its
<a>audio-producing participants</a>.
Releases platform-level media focus and sets the <a>media session</a>'s
<a>state</a> to <code><a lt="idle media session state">idle</a></code>.
</dd>
</dl>

Expand All @@ -263,8 +269,56 @@ session state">idle</a></code>.
The <dfn attribute for="MediaSession"><code>kind</code></dfn>
attribute must return the <a>media session</a>'s <a>kind</a>.

The <dfn method for="MediaSession"><code>activate()</code></dfn> method, when
invoked, must run these steps:

<ol>
<li>
Let <var>media session</var> be the <a>context object</a>.
</li>
<li>
Let <var>promise</var> be a new promise.
</li>
<li>
Return <var>promise</var>, and run the remaining steps <a>in parallel</a>.
</li>
<li>
<a>Activate</a> <var>media session</var>.
</li>
<li>
If <a>activate</a> failed, reject <var>promise</var> with a
<code>TypeError</code>.
</li>
<li>
Otherwise, fulfill <var>promise</var> with undefined.
</li>
</ol>

Note: {{activate()}} can fail if there is an ongoing high-priority activity,
e.g. a phone call.

The <dfn method for="MediaSession"><code>deactivate()</code></dfn> method, when
invoked, must <a>deactivate</a> the <a>context object</a>.
invoked, must run these steps:

<ol>
<li>
Let <var>media session</var> be the <a>context object</a>.
</li>
<li>
Let <var>promise</var> be a new promise.
</li>
<li>
Return <var>promise</var>, and run the remaining steps <a>in parallel</a>.
</li>
<li>
<a>Deactivate</a> <var>media session</var>.
</li>
<li>
Fulfill <var>promise</var> with undefined.
</li>
</ol>

Note: Unlike {{activate()}}, {{deactivate()}} cannot fail.

<h3 id="media-session-states">States</h3>

Expand Down Expand Up @@ -570,8 +624,7 @@ the original corresponding <a>duck</a> request.

<h3 id="activating-a-media-session">Activating a media session</h3>

The <dfn>media session activation algorithm</dfn> takes one argument,
<var>media session</var>, and consists of the following steps:
To <dfn>activate</dfn> a <var>media session</var>, run these steps:

<ol>
<li>
Expand Down Expand Up @@ -647,11 +700,11 @@ The <dfn>media session activation algorithm</dfn> takes one argument,

<h3 id="interrupting-a-media-session">Interrupting a media session</h3>

A <a>media session</a> may be interrupted at any time after its
<a>media session activation algorithm</a> has been run. This typically occurs
when another application or another <a>media session</a> requests and is granted
a level of platform media focus that affects the <a>media session</a> based on
its <a>kind</a>.
An <code><a lt="active media session state">active</a></code> <a>media
session</a> may be interrupted at any time. This typically occurs when another
application or another <a>media session</a> requests and is granted a level of
platform media focus that affects the <a>media session</a> based on its
<a>kind</a>.

Interruptions can be both transient or permanent. A transient interruption means
we can either choose to <a>duck</a> our media content and continue playing it
Expand Down Expand Up @@ -699,10 +752,9 @@ The <dfn>media session interruption algorithm</dfn> takes one argument,
state">idle</a></code>.

<p class="note">
This implies that the next time the <a>media session activation
algorithm</a> is run against <var>media session</var> that we will
re-request media focus according to the steps defined in that
algorithm.
This implies that the next time the <var>media session</var> is
<a>activated</a>, that we will re-request media focus according to
the steps defined in that algorithm.
</p>
</li>
<li>
Expand Down Expand Up @@ -1031,9 +1083,9 @@ The <dfn>media session deactivation algorithm</dfn> takes one argument,
<code><a lt="idle media session state">idle</a></code>.

<p class="note">
This implies that the next time the <a>media session activation
algorithm</a> is run against <var>media session</var> that we will
re-request media focus according to the steps defined in that algorithm.
This implies that the next time the <var>media session</var> is
<a>activated</a>, that we will re-request media focus according to the
steps defined in that algorithm.
</p>
</li>
</ol>
Expand Down Expand Up @@ -1103,13 +1155,14 @@ following steps, passing in <a>media element</a> as <var>media element</var>:
element</var> to this list.
</li>
<li>
Let <var>activated</var> be the result of running the <a>media session
activation algorithm</a> for <var>media session</var>.
<a>Activate</a> <var>media session</var>.
</li>
<li>
If <var>activated</var> is failure, <a>pause</a> <var>current media
element</var>.
If <a>activate</a> failed, <a>pause</a> <var>media element</var>.
</li>
<!-- TODO(philipj): Integrate with HTML to better precisely when implicit
activation happens and clarify that it's only the paused attribute that's
temporarily paused, there should be no actual playback, however short. -->
</ol>


Expand Down Expand Up @@ -1206,38 +1259,6 @@ agent must run the following steps:
</li>
</ol>

<h3 id="activating-a-media-session-from-an-audiocontext-object">Activating a
media session from an {{AudioContext}} object</h3>

<!-- XXX https://www.w3.org/Bugs/Public/show_bug.cgi?id=28625 -->

When the {{resume()}} method on an {{AudioContext}} object is invoked from
script and that {{AudioContext}} object's {{state}} attribute is "{{suspended}}"
then the user agent must run the following steps:

<ol>
<li>
Let <var>audio object</var> be the current {{AudioContext}} object.
</li>
<li>
Let <var>media session</var> be the value of <var>audio object</var>'s
<a>current media session</a>.
</li>
<li>
If <var>audio object</var> is not currently in <var>media session</var>'s
list of <a>audio-producing participants</a>, then append <var>audio
object</var> to this list.
</li>
<li>
Let <var>activated</var> be the result of running the <a>media session
activation algorithm</a> for <var>media session</var>.
</li>
<li>
If <var>activated</var> is failure, <a>pause</a> <var>audio object</var>.
</li>
</ol>


<h3 id="interrupting-a-media-session-from-an-audiocontext-object">Interrupting a
media session from an {{AudioContext}} object</h3>

Expand All @@ -1249,43 +1270,6 @@ When the user agent is to <dfn>resume a web audio object</dfn> for a given
{{AudioContext}} object it must invoke that {{AudioContext}} object's
{{resume()}} method.

<h3 id="deactivating-a-media-session-from-an-audiocontext-object">Deactivating a
media session from an {{AudioContext}} object</h3>

When an {{AudioContext}} object's {{state}} attribute transitions to
"{{closed}}", the user agent must <a>release web audio object from its media
session</a>.

When the user agent is to <dfn>release web audio object from its media
session</dfn> for a given {{AudioContext}} object it must run the following
steps:

<ol>
<li>
Let <var>audio object</var> be the current {{AudioContext}} object.
</li>
<li>
Let <var>media session</var> be the value of <var>audio object</var>'s
<a>current media session</a>.
</li>
<li>
If <var>audio object</var> is not currently in <var>media session</var>'s
list of <a>audio-producing participants</a>, then terminate these steps.
</li>
<li>
If <var>audio object</var> is in <var>media session</var>'s <a>resume
list</a> then remove it from this list.
</li>
<li>
Remove <var>audio object</var> from <var>media session</var>'s list of
<a>audio-producing participants</a>.
</li>
<li>
Run the <a>media session deactivation algorithm</a> for <var>media
session</var>.
</li>
</ol>

<h2 id="examples">Examples</h2>

<em>This section is non-normative.</em>
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