Sonic Pi timing demo in Opal Ruby

README.md

Click here to try in Opal

iteration_with_sleep.js

// Proof of concept for blocking sleep with iteration using jsfiddle
// note the parallel iteration

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function demo() {
  console.log("boom")
  await sleep(1000);
}

async function demo2() {
  while(true) {
    await demo();
  }
}

async function demo3() {
  console.log("tick")
  await sleep(500);
}

async function demo4() {
  while(true) {
    await demo3();
  }
}

demo2();
demo4();

timing.js.rb

# takes 20 seconds to run so be patient

start_time = Time.now.to_f
sched_ahead = 0.5
virtual_time = start_time + sched_ahead

10.times do
  sleep_time = 2
  
  # calculate an "ideal" time that we'd like to sleep for
  # and cache it
  virtual_time = virtual_time + sleep_time
  
  # get the real time
  # This will most likely be a few milliseconds further on
  #   than our ideal time because of computation time etc.
  now = Time.now.to_f
  puts now
  
  # sleep for slightly less than our ideal time,
  # taking into account the delay
  sleep(virtual_time - now)
end

webaudio-sampler.js

window.AudioContext = window.AudioContext || window.webkitAudioContext;

/// custom buffer loader
/// see http://www.html5rocks.com/en/tutorials/webaudio/intro/
function BufferLoader(context, urlList, callback) {
    this.context = context;
    this.urlList = urlList;
    this.onload = callback;
    this.bufferList = new Array();
    this.loadCount = 0;
}

BufferLoader.prototype.loadBuffer = function (url, index) {
    // Load buffer asynchronously
    var request = new XMLHttpRequest();
    request.open("GET", url, true);
    request.responseType = "arraybuffer";

    var loader = this;

    request.onload = function () {
        // Asynchronously decode the audio file data in request.response
        loader.context.decodeAudioData(
        request.response,

        function (buffer) {
            if (!buffer) {
                alert('error decoding file data: ' + url);
                return;
            }
            loader.bufferList[index] = buffer;
            if (++loader.loadCount == loader.urlList.length) loader.onload(loader.bufferList);
        },

        function (error) {
            console.error('decodeAudioData error', error);
        });
    }

    request.onerror = function (e) {
        alert('BufferLoader: XHR error');
        console.log(e);
    }

    request.send();
}

BufferLoader.prototype.load = function () {
    for (var i = 0; i < this.urlList.length; ++i)
    this.loadBuffer(this.urlList[i], i);
}

/// setup audio context and start loading samples
var actx =
new AudioContext(),
    blst,
    bLoader = new BufferLoader(
    actx, [
        'https://dl.dropboxusercontent.com/s/mide1jl8ks3hdmd/drum_cymbal_closed.flac',
        'https://dl.dropboxusercontent.com/s/mide1jl8ks3hdmd/drum_cymbal_closed.flac',
        'https://dl.dropboxusercontent.com/s/zc5nu4pm4oree63/bd_haus.flac'],
    done),
    isReady = false;

/// start loading the samples
bLoader.load();

/// when samples are loaded update status
function done(bl) {
    blst = bl;
    isReady = true;
    $('#status').html('Ready!');
}

/// this sets up chain so we can play audio
function play(i) {
    var src = actx.createBufferSource();
    src.buffer = blst[i];
    src.connect(actx.destination);
    src.start(0);
}

/// check keys
$(window).bind("keydown", function (key) {
    if (!isReady) return;

    switch (parseInt(key.which, 10)) {
        case 65:
            play(0);
            break;
        case 83:
            play(1);
            break;
        case 68:
            play(2);
            break;
    }

})

I'm using this gist as a sort of work log as I try things out. I did have second thoughts around contributing to Opal based on some history around that particular project. I was going to include the following statement in my commit message but after engaging with the core committers there I agreed to use a different forum. I'm including the comment here for posterity:

Finally, if my contributions to the project are accepted I agree to the
terms of the code of conduct. For my own peace of mind though, I would
like to go on record to say that I don't share the views of other
maintainers on the issue of transgender discrimination in particular.

I don't want to make any more political statements than necessary as
this project has already hosted a great deal of discussion. However, as a sibling of
mine is a) currently transitioning gender and b) working towards a career in coding I
don't feel I can ignore the issue with a clear conscience.

Rather than walking away or ignoring the project I have chosen to engage and to
contribute if I can. My view is that I'd like to move forward with
positivity but this doesn't imply that I condone or support the views
I've seen expressed by maintainers elsewhere.