var core = require('../core'),
EventEmitter = require('eventemitter3').EventEmitter,
// Internal event used by composed emitter
TICK = 'tick';
/**
* Yes, this is accessing an internal module:eventemitter3 api.
* Ugly, but calling module:eventemitter3.EventEmitter#listeners
* does a bit too much for what this is for.
* This is simple enough to keep track of and contribute
* back to the eventemitter3 project in the near future.
*
* @private
*/
function hasListeners(emitter)
{
return !!(emitter._events && emitter._events[TICK]);
}
/**
* A Ticker class that runs an update loop that other objects listen to.
* This class is composed around an EventEmitter object to add listeners
* meant for execution on the next requested animation frame.
* Animation frames are requested only when necessary,
* e.g. When the ticker is started and the emitter has listeners.
*
* @class
* @memberof PIXI.extras
*/
function Ticker()
{
var _this = this;
/**
* Internal tick method bound to ticker instance.
* This is because in early 2015, Function.bind
* is still 60% slower in high performance scenarios.
* Also separating frame requests from update method
* so listeners may be called at any time and with
* any animation API, just invoke ticker.update(time).
*
* @private
*/
this._tick = function _tick(time) {
_this._requestId = null;
if (_this.started)
{
_this.update(time);
}
// Check here because listeners could have side effects
// and may have modified state during frame execution.
// A new frame may have been requested or listeners removed.
if (_this.started && _this._requestId === null && hasListeners(_this._emitter))
{
_this._requestId = requestAnimationFrame(_this._tick);
}
};
/**
* Internal emitter used to fire 'tick' event
* @private
*/
this._emitter = new EventEmitter();
/**
* Internal current frame request ID
* @private
*/
this._requestId = null;
/**
* Internal value managed by minFPS property setter and getter.
* This is the maximum allowed millseconds between updates.
* @private
*/
this._maxElapsedMS = 100;
/**
* Whether or not this ticker should
* start automatically when a listener is added.
*
* @member {boolean}
*/
this.autoStart = false;
/**
* The current percentage of the
* target FPS with speed factored in.
*
* @member {number}
*/
this.deltaTime = 1;
/**
* The last time {@link PIXI.extras.Ticker#update}
* was invoked by animation frame callback or manually.
*
* @member {number}
*/
this.lastTime = 0;
/**
* Factor of current FPS.
* @example
* ticker.speed = 2; // Approximately 120 FPS, or 0.12 FPMS.
*
* @member {number}
*/
this.speed = 1;
/**
* Whether or not this ticker has been started.
* `true` if {@link PIXI.extras.Ticker.start} has been called.
* `false` if {@link PIXI.extras.Ticker.stop} has been called.
*
* @member {boolean}
*/
this.started = false;
}
Object.defineProperties(Ticker.prototype, {
/**
* Gets the frames per second for which this
* ticker is running. The default is appoximately
* 60 FPS in modern browsers, but may vary.
* This also factors in the property value of
* {@link PIXI.extras.Ticker#speed}.
*
* @member
* @memberof PIXI.extras.Ticker#
* @readonly
*/
FPS: {
get: function()
{
return core.TARGET_FPMS * 1000 * this.deltaTime;
}
},
/**
* This property manages the maximum amount
* of time allowed to elapse between ticks,
* or calls to {@link PIXI.extras.Ticker#update}.
*
* @member
* @memberof PIXI.extras.Ticker#
* @default 10
*/
minFPS: {
get: function()
{
return 1000 / this._maxElapsedMS;
},
set: function(fps)
{
var minFPMS = Math.min(fps / 1000, core.TARGET_FPMS);
this._maxElapsedMS = 1 / minFPMS;
}
}
});
/**
* Conditionally requests a new animation frame.
* If a frame has not already been requested, and if the internal
* emitter has listeners, a new frame is requested.
*
* @private
*/
Ticker.prototype._requestIfNeeded = function _requestIfNeeded()
{
if (this._requestId === null && hasListeners(this._emitter))
{
// ensure callbacks get correct delta
this.lastTime = performance.now();
this._requestId = requestAnimationFrame(this._tick);
}
};
/**
* Conditionally cancels a pending animation frame.
*
* @private
*/
Ticker.prototype._cancelIfNeeded = function _cancelIfNeeded()
{
if (this._requestId !== null)
{
cancelAnimationFrame(this._requestId);
this._requestId = null;
}
};
/**
* Conditionally requests a new animation frame.
* If the ticker has been started it checks if a frame has not already
* been requested, and if the internal emitter has listeners. If these
* conditions are met, a new frame is requested. If the ticker has not
* been started, but autoStart is `true`, then the ticker starts now,
* and continues with the previous conditions to request a new frame.
*
* @private
*/
Ticker.prototype._startIfPossible = function _startIfPossible()
{
if (this.started)
{
this._requestIfNeeded();
}
else if (this.autoStart)
{
this.start();
}
};
/**
* Calls {@link module:eventemitter3.EventEmitter#on} internally for the
* internal 'tick' event. It checks if the emitter has listeners,
* and if so it requests a new animation frame at this point.
*
* @returns {PIXI.extras.Ticker} this
*/
Ticker.prototype.add = function add(fn, context)
{
this._emitter.on(TICK, fn, context);
this._startIfPossible();
return this;
};
/**
* Calls {@link module:eventemitter3.EventEmitter#once} internally for the
* internal 'tick' event. It checks if the emitter has listeners,
* and if so it requests a new animation frame at this point.
*
* @returns {PIXI.extras.Ticker} this
*/
Ticker.prototype.addOnce = function addOnce(fn, context)
{
this._emitter.once(TICK, fn, context);
this._startIfPossible();
return this;
};
/**
* Calls {@link module:eventemitter3.EventEmitter#off} internally for 'tick' event.
* It checks if the emitter has listeners for 'tick' event.
* If it does, then it cancels the animation frame.
*
* @returns {PIXI.extras.Ticker} this
*/
Ticker.prototype.remove = function remove(fn, once)
{
this._emitter.off(TICK, fn, once);
if (!hasListeners(this._emitter))
{
this._cancelIfNeeded();
}
return this;
};
/**
* Starts the ticker. If the ticker has listeners
* a new animation frame is requested at this point.
*/
Ticker.prototype.start = function start()
{
if (!this.started)
{
this.started = true;
this._requestIfNeeded();
}
};
/**
* Stops the ticker. If the ticker has requested
* an animation frame it is canceled at this point.
*/
Ticker.prototype.stop = function stop()
{
if (this.started)
{
this.started = false;
this._cancelIfNeeded();
}
};
/**
* Triggers an update, setting deltaTime, lastTime, and
* firing the internal 'tick' event invoking all listeners.
*
* @param [currentTime=performance.now()] {number} the current time of execution
*/
Ticker.prototype.update = function update(currentTime)
{
var elapsedMS;
// Allow calling update directly with default currentTime.
currentTime = currentTime || performance.now();
elapsedMS = currentTime - this.lastTime;
// cap the milliseconds elapsed
if (elapsedMS > this._maxElapsedMS)
{
elapsedMS = this._maxElapsedMS;
}
this.deltaTime = (elapsedMS * core.TARGET_FPMS);
// Factor in speed
this.deltaTime *= this.speed;
// Invoke listeners added to internal emitter
this._emitter.emit(TICK, this.deltaTime);
this.lastTime = currentTime;
};
/**
* The shared ticker instance used by {@link PIXI.extras.MovieClip}.
* The property {@link PIXI.extras.Ticker#autoStart} is set to true
* for this instance.
*
* @type {PIXI.extras.Ticker}
* @memberof PIXI.extras.Ticker
*/
Ticker.sharedTicker = new Ticker();
Ticker.sharedTicker.autoStart = true;
module.exports = Ticker;
