Bergson ======= What is Bergson? ---------------- Bergson is the scheduling system for [Flocking](https://github.com/colinbdclark/Flocking) and [Aconite](https://github.com/colinbdclark/aconite). It provides a variety of clocks driven by different sources (such as requestAnimationFrame, the Web Audio API, and setInterval), and a priority queue-based scheduler that allows you to queue up one-time and repeating function calls. Bergson provides a very low-level API for scheduling, and is intended for library developers to build their own rhythmic and pattern-based abstractions on top of. Examples -------- ### Creating a Scheduler with the requestAnimationFrame Clock ### var scheduler = berg.scheduler({ components: { clock: { type: "berg.clock.requestAnimationFrame", options: { freq: 60 } } } }); scheduler.start(); ### Scheduling one-time events ### scheduler.schedule({ type: "once", time: 30 // 30 seconds from now callback: function (now) { // Do something in the future. } }); ### Scheduling repeating events ### scheduler.schedule({ type: "repeat", time: 5, // Start repeating five seconds from now. freq: 2, // Repeat every two seconds. end: 20, // Stop repeating 20 seconds from now. callback: function (now) { // Do something repeatedly. } }); ### Listening for Clock Events Directly ### scheduler.clock.events.onTick.addListener(function (time, rate) { // Do something every time the clock ticks. }); Bergson API ------------- ### Scheduler API ### #### Score Event Specifications #### A _score event specification_ is a JSON-type (i.e. plain old, non-prototypal) object that describes the event to be scheduled. It can contain the following properties.
Property Value Description
type "once" or "repeat" The type of event to schedule (either one-time or repeating).
time Number The future time in seconds when the scheduled event should occur.
interval Number (Only for repeating events) The time interval, in seconds, between repetitions. This option takes precendence over freq if both are provided.
freq Number (Only for repeating events) The frequency at which the event should repeat. This option will be overridden by interval if both are provided.
end Number (Only for repeating events) The future time in seconds when the scheduled event should stop repeating.
callback Function The function to invoke.
#### Scheduler Model #### For more information on interacting with models, see the [Infusion documentation about the Change Applier](http://docs.fluidproject.org/infusion/development/ChangeApplierAPI.html).
Property Description Types
timeScale The scheduler's time scale factor. Defaults to 1.0. Number
#### Scheduler Members ####
Property Description Types
queue The priority queue used to sort and queue score events. berg.priorityQueue
#### Scheduler Methods ####
Method Description Argument Types Returns
start Starts the scheduler and its clock. none undefined
stop Stops the scheduler and its clock. none undefined
schedule Schedules an event A _score event specification_ object The scheduled score event specification.
clear Removes a scheduled event from the scheduler queue. The _score event specification_ to clear. undefined
clearAll Removes all scheduled events from the scheduler queue. none undefined
setTimeScale Sets the time scale factor for the scheduler. This will cause all time values for current and future scheduled events to be scaled by the specified value. Number undefined
### Clock API ### #### Clock Members ####
Property Description Types
time The current clock time, in seconds. Number
freq The clock's frequency, in cyles per second. Number
tickDuration The duration between ticks, in seconds. Number
#### Clock Methods ####
Method Description Argument Types Returns
start Starts the clock. none undefined
stop Stops clock. none undefined
tick Advances the clock's time. (This will be invoked automatically for most clocks.) None undefined
#### Clock Events ####
Event Name Description Argument Types
onTick Fires each time the clock ticks. Number time: the current clock time in seconds
Types of Clocks ---------------
Clock Description Default rate
berg.clock.requestAnimationFrame A clock that is driven at (or as near as possible to) the display's refresh rate by the browser's built-in requestAnimationFrame function. Note that this clock will be throttled down to 1 Hz automatically by the browser if its tab is not active. 60 Hz. You must override this value if your display is running a different refresh rate.
berg.clock.audioContext Uses the Web Audio API's AudioContext as a source of time. This clock needs to be driven by your own ScriptProcessorNode code (i.e. by calling its tick() method within your onaudioprocess handler). This clock will not start ticking until its start() method is invoked by a user action (such as a button click). Dynamically determined based on the AudioContext's sampleRate and this clock's blockSize option.
berg.clock.autoAudioContext An AudioContext-based clock that will automatically create a ScriptProcessorNode instance and wire it up correctly for you. Use this if you're not using the Web Audio API directly, but want a rock-solid clock for scheduling events in your application. This clock will not start ticking until its start() method is invoked by a user action (such as a button click). Dynamically determined based on the AudioContext's sampleRate and this clock's blockSize option.
berg.clock.setInterval A clock that is driven by the browser's built-in (and notoriously jittery) setInterval function. Use this if you don't need significant reliability, and want maximal cross-environment compatibility (e.g. with Node.js). Note that this clock will be throttled down automatically by the browser if its tab is not active. 10 Hz
berg.clock.workerSetInterval Like berg.clock.setInterval, except that it employs a Web Worker in order to avoid the standard throttling done by browsers when the page is in the background. 10 Hz
berg.clock.offline A base grade for creating your own types of clocks. An offline clock tracks time relatively (i.e. without reference to a "real" source of time such as the system clock). This clock should be driven manually by invoking its tick() method. 1 Hz
berg.clock.realtime A base grade for creating your own types of clocks. A realtime clock tracks time based on the actual system time using, by default, performance.now(). This clock should be driven manually by invoking its tick() method. 1 Hz
Building and Testing Bergson ----------------------------- ### Prerequisites Bergson uses Node.js, npm, Grunt, and Testem for its build and test tooling. Here's how to get set up: 1. Install the [Node.js](https://nodejs.org/en/) LTS release 3. Install Grunt: npm install -g grunt-cli 4. Install Testem: npm install -g testem ### How to Build Bergson To download all of Bergson's dependencies, build them, and then build Bergson itself, run the following commands: npm install grunt ### Running Bergson's Test Suite Bergson's test suite can be run on both Node.js and all of the browsers installed on your computer using Testem: npm test If you'd like to run only the Node.js tests, run: npm run node-test Or if you only want to run the browser tests: npm run browser-test Alternatively, if you'd like to only run the tests in one browser, you can open the test suite ``tests/unit/all-tests.html`` file by hand in your browser. Community --------- Bergson is supported by the Flocking community and uses its forums: ### Mailing List The [Flocking mailing list](http://lists.idrc.ocadu.ca/mailman/listinfo/flocking) is the place to ask questions, share code, and request new features. ### Chat Flocking has an IRC channel, which can also be used to ask questions about Bergson. Join #flocking on irc.freenode.net. Credits and License ------------------- Bergson is written and maintained by Colin Clark. It is dually licensed under the MIT and GPL 2.0 licenses.