nes-embed.js

// Matt Hughson

var SCREEN_WIDTH = 256;
var SCREEN_HEIGHT = 240;
var FRAMEBUFFER_SIZE = SCREEN_WIDTH*SCREEN_HEIGHT;

var canvas_ctx, image;
var framebuffer_u8, framebuffer_u32;

var AUDIO_BUFFERING = 512;
var SAMPLE_COUNT = 4*1024;
var SAMPLE_MASK = SAMPLE_COUNT - 1;
var audio_samples_L = new Float32Array(SAMPLE_COUNT);
var audio_samples_R = new Float32Array(SAMPLE_COUNT);
var audio_write_cursor = 0, audio_read_cursor = 0;

var nes = new jsnes.NES({
	onFrame: function(framebuffer_24){
		for(var i = 0; i < FRAMEBUFFER_SIZE; i++) framebuffer_u32[i] = 0xFF000000 | framebuffer_24[i];
	},
	onAudioSample: function(l, r){
		audio_samples_L[audio_write_cursor] = l;
		audio_samples_R[audio_write_cursor] = r;
		audio_write_cursor = (audio_write_cursor + 1) & SAMPLE_MASK;
	},
	// sampleRate: getSampleRate()
});

function getSampleRate()
{
	if (!window.AudioContext) {
		return 44100;
	}
	let myCtx = new window.AudioContext();
	let sampleRate = myCtx.sampleRate;
	myCtx.close();
	return sampleRate;
}	

function onAnimationFrame(){
	window.setTimeout(onAnimationFrame, 1000/60);
	
	image.data.set(framebuffer_u8);
	canvas_ctx.putImageData(image, 0, 0);
	nes.frame();
}

function audio_remain(){
	return (audio_write_cursor - audio_read_cursor) & SAMPLE_MASK;
}

function audio_callback(event){
	var dst = event.outputBuffer;
	var len = dst.length;
	
	// Attempt to avoid buffer underruns.
	if(audio_remain() < AUDIO_BUFFERING) nes.frame();
	
	var dst_l = dst.getChannelData(0);
	var dst_r = dst.getChannelData(1);
	for(var i = 0; i < len; i++){
		var src_idx = (audio_read_cursor + i) & SAMPLE_MASK;
		dst_l[i] = audio_samples_L[src_idx];
		dst_r[i] = audio_samples_R[src_idx];
	}
	
	audio_read_cursor = (audio_read_cursor + len) & SAMPLE_MASK;
}

function keyboard(callback, event){
	var player = 1;
	var prevent = true;
	switch(event.keyCode){
		case 38: // UP
		case 87: // W
			callback(player, jsnes.Controller.BUTTON_UP); break;
		case 40: // Down
		case 83: // S
			callback(player, jsnes.Controller.BUTTON_DOWN); break;
		case 37: // Left
		case 65: // A
			callback(player, jsnes.Controller.BUTTON_LEFT); break;
		case 39: // Right
		case 68: // D
			callback(player, jsnes.Controller.BUTTON_RIGHT); break;
		case 18: // 'alt'
		case 88: // 'x'
			callback(player, jsnes.Controller.BUTTON_A); break;
		case 90: // 'z'
		case 17: // 'ctrl'
			callback(player, jsnes.Controller.BUTTON_B); break;
		case 32: // Space
		case 16: // Right Shift
			callback(player, jsnes.Controller.BUTTON_SELECT); break;
		case 13: // Return
			callback(player, jsnes.Controller.BUTTON_START); break;
		default: prevent = false; break;
	}
	
	if (prevent){
		event.preventDefault();
	}
}

function nes_init(canvas_id){
	var canvas = document.getElementById(canvas_id);
	canvas_ctx = canvas.getContext("2d");
	image = canvas_ctx.getImageData(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
	
	canvas_ctx.fillStyle = "black";
	canvas_ctx.fillRect(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
	
	// Allocate framebuffer array.
	var buffer = new ArrayBuffer(image.data.length);
	framebuffer_u8 = new Uint8ClampedArray(buffer);
	framebuffer_u32 = new Uint32Array(buffer);
	
	// Setup audio.
	var audio_ctx = new window.AudioContext();
	var script_processor = audio_ctx.createScriptProcessor(AUDIO_BUFFERING, 0, 2);
	script_processor.onaudioprocess = audio_callback;
	script_processor.connect(audio_ctx.destination);
	document.addEventListener('click',  () => {audio_ctx.resume()})
}

function nes_boot(rom_data){
	nes.loadROM(rom_data);
	window.requestAnimationFrame(onAnimationFrame);
}

function nes_load_data(canvas_id, rom_data){
	nes_init(canvas_id);
	nes_boot(rom_data);
}

function nes_load_url(canvas_id, path){
	nes_init(canvas_id);
	
	var req = new XMLHttpRequest();
	req.open("GET", path);
	req.overrideMimeType("text/plain; charset=x-user-defined");
	req.onerror = () => console.log(`Error loading ${path}: ${req.statusText}`);
	
	req.onload = function() {
		if (this.status === 200) {
		nes_boot(this.responseText);
		} else if (this.status === 0) {
			// Aborted, so ignore error
		} else {
			req.onerror();
		}
	};
	
	req.send();
}

document.addEventListener('keydown', (event) => {keyboard(nes.buttonDown, event)});
document.addEventListener('keyup', (event) => {keyboard(nes.buttonUp, event)});


/////////////////////
// GAMEPAD SUPPORT
//
// Based on documentation here: https://developer.mozilla.org/en-US/docs/Web/API/Gamepad_API/Using_the_Gamepad_API
/////////////////////

var haveEvents = 'ongamepadconnected' in window;
var controllers = {};

// Once the presses a button on one of the controllers, this will store
// the index of that controller so that only that controller is checked
// each frame. This is to avoid additional controllers triggering key_up
// events when they are just sitting there inactive.
var cur_controller_index = -1;

function connecthandler(e) {
  addgamepad(e.gamepad);
}

function addgamepad(gamepad) {
  controllers[gamepad.index] = gamepad;
  requestAnimationFrame(updateStatus);
}

function disconnecthandler(e) {
  removegamepad(e.gamepad);
}

function removegamepad(gamepad) {
  delete controllers[gamepad.index];
}

// Check all controllers to see if player has pressed any buttons.
// If they have, store that as the current controller.
function findController()
{
	var i = 0;
	var j;

	for (j in controllers) 
	{
		var controller = controllers[j];

		for (i = 0; i < controller.buttons.length; i++) 
		{
			var val = controller.buttons[i];
			var pressed = val == 1.0;
			if (typeof(val) == "object") 
			{
				pressed = val.pressed;
				val = val.value;
			}

			if (pressed) 
			{
				cur_controller_index = j;
			}
		}
	}
}

function updateStatus() 
{
	if (!haveEvents) 
	{
		scangamepads();
	}

	// If a controller has not yet been chosen, check for one now.
	if (cur_controller_index == -1)
	{
	  findController();
	}

	// Allow for case where controller was chosen this frame
	if (cur_controller_index != -1)
	{
		var i = 0;
		var j;

		var controller = controllers[cur_controller_index];

		for (i = 0; i < controller.buttons.length; i++) 
		{
			var val = controller.buttons[i];
			var pressed = val == 1.0;
			if (typeof(val) == "object") 
			{
				pressed = val.pressed;
				val = val.value;
			}

			var player = 1 //parseInt(j,10) + 1;

			if (pressed) 
			{
				var callback = nes.buttonDown;
				switch(i)
				{
					case 12: // UP
					callback(player, jsnes.Controller.BUTTON_UP); break;
					case 13: // Down
					callback(player, jsnes.Controller.BUTTON_DOWN); break;
					case 14: // Left
					callback(player, jsnes.Controller.BUTTON_LEFT); break;
					case 15: // Right
					callback(player, jsnes.Controller.BUTTON_RIGHT); break;
					case 1: // 'A'
					callback(player, jsnes.Controller.BUTTON_A); break;
					case 0: // 'B'
					callback(player, jsnes.Controller.BUTTON_B); break;
					case 8: // Select
					callback(player, jsnes.Controller.BUTTON_SELECT); break;
					case 9: // Start
					callback(player, jsnes.Controller.BUTTON_START); break;
				}
			} 
			else 
			{
				var callback = nes.buttonUp;
				switch(i)
				{
					case 12: // UP
					callback(player, jsnes.Controller.BUTTON_UP); break;
					case 13: // Down
					callback(player, jsnes.Controller.BUTTON_DOWN); break;
					case 14: // Left
					callback(player, jsnes.Controller.BUTTON_LEFT); break;
					case 15: // Right
					callback(player, jsnes.Controller.BUTTON_RIGHT); break;
					case 1: // 'A'
					callback(player, jsnes.Controller.BUTTON_A); break;
					case 0: // 'B'
					callback(player, jsnes.Controller.BUTTON_B); break;
					case 8: // Select
					callback(player, jsnes.Controller.BUTTON_SELECT); break;
					case 9: // Start
					callback(player, jsnes.Controller.BUTTON_START); break;
				}
			}

			// var axes = d.getElementsByClassName("axis");
			// for (i = 0; i < controller.axes.length; i++)
			// {
				// var a = axes[i];
				// a.innerHTML = i + ": " + controller.axes[i].toFixed(4);
				// a.setAttribute("value", controller.axes[i] + 1);
			// }
		}
	}
		
	requestAnimationFrame(updateStatus);
}

function scangamepads() {
  var gamepads = navigator.getGamepads ? navigator.getGamepads() : (navigator.webkitGetGamepads ? navigator.webkitGetGamepads() : []);
  for (var i = 0; i < gamepads.length; i++) {
    if (gamepads[i]) {
      if (gamepads[i].index in controllers) {
        controllers[gamepads[i].index] = gamepads[i];
      } else {
        addgamepad(gamepads[i]);
      }
    }
  }
}

window.addEventListener("gamepadconnected", connecthandler);
window.addEventListener("gamepaddisconnected", disconnecthandler);

if (!haveEvents) {
 setInterval(scangamepads, 500);
}