shaka-player
Version:
DASH/EME video player library
211 lines (187 loc) • 6.55 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.media.RegionObserver');
goog.require('shaka.media.IPlayheadObserver');
goog.require('shaka.media.RegionTimeline');
/**
* The region observer watches a region timeline and playhead, and fires events
* (onEnter, onExit, and onSkip) as the playhead moves.
*
* @implements {shaka.media.IPlayheadObserver}
* @final
*/
shaka.media.RegionObserver = class {
/**
* Create a region observer for the given timeline. The observer does not
* own the timeline, only uses it. This means that the observer should NOT
* destroy the timeline.
*
* @param {!shaka.media.RegionTimeline} timeline
*/
constructor(timeline) {
/** @private {shaka.media.RegionTimeline} */
this.timeline_ = timeline;
/**
* A mapping between a region and where we previously were relative to it.
* When the value here differs from what we calculate, it means we moved and
* should fire an event.
*
* @private {!Map.<shaka.extern.TimelineRegionInfo,
* shaka.media.RegionObserver.RelativePosition_>}
*/
this.oldPosition_ = new Map();
/** @private {shaka.media.RegionObserver.EventListener} */
this.onEnter_ = (region, seeking) => {};
/** @private {shaka.media.RegionObserver.EventListener} */
this.onExit_ = (region, seeking) => {};
/** @private {shaka.media.RegionObserver.EventListener} */
this.onSkip_ = (region, seeking) => {};
// To make the rules easier to read, alias all the relative positions.
const RelativePosition = shaka.media.RegionObserver.RelativePosition_;
const BEFORE_THE_REGION = RelativePosition.BEFORE_THE_REGION;
const IN_THE_REGION = RelativePosition.IN_THE_REGION;
const AFTER_THE_REGION = RelativePosition.AFTER_THE_REGION;
/**
* A read-only collection of rules for what to do when we change position
* relative to a region.
*
* @private {!Iterable.<shaka.media.RegionObserver.Rule_>}
*/
this.rules_ = [
{
weWere: null,
weAre: IN_THE_REGION,
invoke: (region, seeking) => this.onEnter_(region, seeking),
},
{
weWere: BEFORE_THE_REGION,
weAre: IN_THE_REGION,
invoke: (region, seeking) => this.onEnter_(region, seeking),
},
{
weWere: AFTER_THE_REGION,
weAre: IN_THE_REGION,
invoke: (region, seeking) => this.onEnter_(region, seeking),
},
{
weWere: IN_THE_REGION,
weAre: BEFORE_THE_REGION,
invoke: (region, seeking) => this.onExit_(region, seeking),
},
{
weWere: IN_THE_REGION,
weAre: AFTER_THE_REGION,
invoke: (region, seeking) => this.onExit_(region, seeking),
},
{
weWere: BEFORE_THE_REGION,
weAre: AFTER_THE_REGION,
invoke: (region, seeking) => this.onSkip_(region, seeking),
},
{
weWere: AFTER_THE_REGION,
weAre: BEFORE_THE_REGION,
invoke: (region, seeking) => this.onSkip_(region, seeking),
},
];
}
/** @override */
release() {
this.timeline_ = null;
// Clear our maps so that we are not holding onto any more information than
// needed.
this.oldPosition_.clear();
// Clear the callbacks so that we don't hold onto any references external
// to this class.
this.onEnter_ = (region, seeking) => {};
this.onExit_ = (region, seeking) => {};
this.onSkip_ = (region, seeking) => {};
}
/** @override */
poll(positionInSeconds, wasSeeking) {
const RegionObserver = shaka.media.RegionObserver;
for (const region of this.timeline_.regions()) {
const previousPosition = this.oldPosition_.get(region);
const currentPosition = RegionObserver.determinePositionRelativeTo_(
region, positionInSeconds);
// We will only use |previousPosition| and |currentPosition|, so we can
// update our state now.
this.oldPosition_.set(region, currentPosition);
for (const rule of this.rules_) {
if (rule.weWere == previousPosition && rule.weAre == currentPosition) {
rule.invoke(region, wasSeeking);
}
}
}
}
/**
* Set all the listeners. This overrides any previous calls to |setListeners|.
*
* @param {shaka.media.RegionObserver.EventListener} onEnter
* The callback for when we move from outside a region to inside a region.
* @param {shaka.media.RegionObserver.EventListener} onExit
* The callback for when we move from inside a region to outside a region.
* @param {shaka.media.RegionObserver.EventListener} onSkip
* The callback for when we move from before to after a region or from
* after to before a region.
*/
setListeners(onEnter, onExit, onSkip) {
this.onEnter_ = onEnter;
this.onExit_ = onExit;
this.onSkip_ = onSkip;
}
/**
* Get the relative position of the playhead to |region| when the playhead is
* at |seconds|. We treat the region's start and end times as inclusive
* bounds.
*
* @param {shaka.extern.TimelineRegionInfo} region
* @param {number} seconds
* @return {shaka.media.RegionObserver.RelativePosition_}
* @private
*/
static determinePositionRelativeTo_(region, seconds) {
const RelativePosition = shaka.media.RegionObserver.RelativePosition_;
if (seconds < region.startTime) {
return RelativePosition.BEFORE_THE_REGION;
}
if (seconds > region.endTime) {
return RelativePosition.AFTER_THE_REGION;
}
return RelativePosition.IN_THE_REGION;
}
};
/**
* An enum of relative positions between the playhead and a region. Each is
* phrased so that it works in "The playhead is X" where "X" is any value in
* the enum.
*
* @enum {number}
* @private
*/
shaka.media.RegionObserver.RelativePosition_ = {
BEFORE_THE_REGION: 1,
IN_THE_REGION: 2,
AFTER_THE_REGION: 3,
};
/**
* All region observer events (onEnter, onExit, and onSkip) will be passed the
* region that the playhead is interacting with and whether or not the playhead
* moving is part of a seek event.
*
* @typedef {function(shaka.extern.TimelineRegionInfo, boolean)}
*/
shaka.media.RegionObserver.EventListener;
/**
* @typedef {{
* weWere: ?shaka.media.RegionObserver.RelativePosition_,
* weAre: ?shaka.media.RegionObserver.RelativePosition_,
* invoke: shaka.media.RegionObserver.EventListener
* }}
*
* @private
*/
shaka.media.RegionObserver.Rule_;