abcjs/src/synth/supports-audio.js

Renderer for abc music notation

var activeAudioContext = require('./active-audio-context');

//
// Support for audio depends on three things: support for Promise, support for AudioContext, and support for AudioContext.resume.
// Unfortunately, AudioContext.resume cannot be detected unless an AudioContext is created, and creating an AudioContext can't
// be done until a user click, so there is no way to know for sure if audio is supported until the user tries.
// We can get close, though - we can test for Promises and AudioContext - there are just a few evergreen browsers that supported
// that before supporting resume, so we'll test what we can.

// The best use of this routine is to call it before doing any audio related stuff to decide whether to bother.
// But then, call it again after a user interaction to test for resume.

function supportsAudio() {
	if (!window.Promise)
		return false;

	if (!window.AudioContext &&
		!window.webkitAudioContext &&
		!navigator.mozAudioContext &&
		!navigator.msAudioContext)
		return false;

	var aac = activeAudioContext();
	if (aac)
		return aac.resume !== undefined;
}

module.exports = supportsAudio;