music21j-port/src/ext/midijs/js/plugin.webmidi.js

A toolkit for computer-aided musicology, Javascript version

/*
	----------------------------------------------------------------------
	Web MIDI API - Native Soundbanks
	----------------------------------------------------------------------
	http://webaudio.github.io/web-midi-api/
	----------------------------------------------------------------------
*/

// information to share with loader...
export const shared_root_info = {};


let plugin = null;
let output = null;
const channels = [];

export const send = (data, delay) => { // set channel volume
	output.send(data, delay * 1000);
};

export const setController = (channel, type, value, delay) => {
	output.send([channel, type, value], delay * 1000);
};

export const setVolume = (channel, volume, delay) => { // set channel volume
	output.send([0xB0 + channel, 0x07, volume], delay * 1000);
};

export const programChange = (channel, program, delay) => { // change patch (instrument)
	output.send([0xC0 + channel, program], delay * 1000);
};

export const pitchBend = (channel, program, delay) => { // pitch bend
	output.send([0xE0 + channel, program], delay * 1000);
};

export const noteOn = (channel, note, velocity, delay) => {
	output.send([0x90 + channel, note, velocity], delay * 1000);
};

export const noteOff = (channel, note, delay) => {
	output.send([0x80 + channel, note, 0], delay * 1000);
};

export const chordOn = (channel, chord, velocity, delay) => {
	for (const note of chord) {
		output.send([0x90 + channel, note, velocity], delay * 1000);
	}
};

export const chordOff = (channel, chord, delay) => {
	for (const note of chord) {
		output.send([0x80 + channel, note, 0], delay * 1000);
	}
};

export const stopAllNotes = () => {
	output.cancel();
	for (let channel = 0; channel < 16; channel ++) {
		output.send([0xB0 + channel, 0x7B, 0]);
	}
};

export const connect = opts => {
	const errFunction = err => {
		console.error('Could not connect to web midi! Falling back to WebAudio:', err);
		// we tried.  Anything that sort of supports webmidi should support WebAudio.
		if (shared_root_info.webaudio_backup_connect) {
			shared_root_info.config.api = 'webaudio';
			shared_root_info.webaudio_backup_connect(opts);
		}
	};
	navigator.requestMIDIAccess().then(access => {
		const plugin = access;
		const pluginOutputs = plugin.outputs;
		if (typeof pluginOutputs == 'function') { // Chrome pre-43
			output = pluginOutputs()[0];
		} else { // Chrome post-43
			output = pluginOutputs[0];
		}
		if (output === undefined) { // nothing there...
			errFunction('No outputs defined');
		} else {
			opts.onsuccess && opts.onsuccess();
		}
	}, errFunction);
};