Workaround to iOS WebAudio default lock – fix for WebAudio MOD/XM/S3M Player

player.js

// Fix for https://github.com/jhalme/webaudio-mod-player

// WebAudio is suspended on iOS by default, until an attempt to
// play audio immediately follows a user interaction.

// A simple workaround is to pre-initialize the context
// and bind a user interaction that plays an empty
// buffer once. Doing so unlocks the suspended state for the 
// remainder of the session.

// I fixed it by adding this unlock method to player.js:
// (matching syntax... old-skool!)

Modplayer.prototype.unlock = function() 
{
  if (this.context==null) this.createContext();
  
  // make an empty buffer
  var tempbuffer = this.context.createBuffer(1, 1, 22050);
  var tempsource = this.context.createBufferSource();
  tempsource.buffer = tempbuffer;
  
  // connect it to the context's output
  tempsource.connect(this.context.destination);
  
  // play that silence!
  tempsource.noteOn(0);
}

// Then using it in a small demo app as follows.
// Could be any main app really... the point is it just
// has to make use of the unlock for iOS.

class ModplayerDemo {

	// create demo
	constructor() {

		// create the player instance
		this.modPlayer = new Modplayer();

		// set whether the web audio session is assumed to be locked based on env
		this.unlocked = ( ModplayerDemo.iOS ) ? false : true;
	}

	// @return whether environment is iOS
	static get iOS() {
		return ( navigator.userAgent.match(/iPhone/i) || navigator.userAgent.match(/iPad/i) || navigator.userAgent.match(/iPod/i) );
	}

	// initialize demo
	init() {
	  
		// for iOS, bind touchstart to unlock the audio context
		if ( ModplayerDemo.iOS ) {
			window.addEventListener( 'touchstart', this.unlock.bind( this ) );
		}
		
		// assign Modplayer onReady delegate for when loading completes
		var that = this;

		this.modPlayer.onReady = function() {
			that.onReady();
		};
	}

	unlock() {
		if ( !this.unlocked ) {
		  
			this.unlocked = true;
			
			// call unlock() to resume the suspended audio session
			this.modPlayer.unlock();
		}
	}

	load(musicUrl) {
		this.modPlayer.load( musicUrl );
	}

	onReady() {
		
		// start playback following load/parse completion
		
		if ( !this.unlocked ) {
			// keep trying every 100ms until unlocked
			setTimeout( this.onReady.bind( this ), 100 );
		}
		else {
			this.modPlayer.play();
		}
	}
}

var demo = new ModplayerDemo();
demo.init();
demo.load( 'mods/Mantronix_and_Tip/mod.overload' );