Support for 1 - 4 Gamepad Controllers in Impact.js for Local Multiplayer Games

example.js

// bind keyboard and gamepad buttons
ig.input.bind( ig.KEY.X, 'shoot1');
ig.input.bind( ig.GAMEPAD1.FACE_1, 'shoot1');

ig.input.bind( ig.GAMEPAD2.FACE_1, 'shoot2');

ig.input.bind( ig.GAMEPAD3.FACE_1, 'shoot3');

ig.input.bind( ig.GAMEPAD4.FACE_1, 'shoot4');


// use .pressed() and .state() pretty much as usual
if( ig.input.pressed('shoot1') ) {
    // shoot for player 1
}

gamepads.js

//
// Adapted from one-gamepad support in this thread:
// http://impactjs.com/forums/help/gamepad-events
//
// Put this in a file at lib/plugins/gamepads.js and require plugins.gamepads in your main module.

ig.module(
	'plugins.gamepads' 
)
.requires(
	'impact.input',
	'impact.game'
)
.defines(function(){

// Assign some values to the Gamepad buttons. We use an offset of 256
// here so we don't collide with the keyboard buttons when binding.
ig.GAMEPAD_BUTTON_OFFSET = 256;

// Define ig.GAMEPAD1 through ig.GAMEPAD4
for (var i = 1; i <= 4; i++) {
	ig['GAMEPAD' + i] = {
		FACE_1: ig.GAMEPAD_BUTTON_OFFSET * i + 0,
		FACE_2: ig.GAMEPAD_BUTTON_OFFSET * i + 1,
		FACE_3: ig.GAMEPAD_BUTTON_OFFSET * i + 2,
		FACE_4: ig.GAMEPAD_BUTTON_OFFSET * i + 3,
		LEFT_SHOULDER: ig.GAMEPAD_BUTTON_OFFSET * i + 4,
		RIGHT_SHOULDER: ig.GAMEPAD_BUTTON_OFFSET * i + 5,
		LEFT_SHOULDER_BOTTOM: ig.GAMEPAD_BUTTON_OFFSET * i + 6,
		RIGHT_SHOULDER_BOTTOM: ig.GAMEPAD_BUTTON_OFFSET * i + 7,
		SELECT: ig.GAMEPAD_BUTTON_OFFSET * i + 8,
		START: ig.GAMEPAD_BUTTON_OFFSET * i + 9,
		LEFT_ANALOGUE_STICK: ig.GAMEPAD_BUTTON_OFFSET * i + 10,
		RIGHT_ANALOGUE_STICK: ig.GAMEPAD_BUTTON_OFFSET * i + 11,
		PAD_TOP: ig.GAMEPAD_BUTTON_OFFSET * i + 12,
		PAD_BOTTOM: ig.GAMEPAD_BUTTON_OFFSET * i + 13,
		PAD_LEFT: ig.GAMEPAD_BUTTON_OFFSET * i + 14,
		PAD_RIGHT: ig.GAMEPAD_BUTTON_OFFSET * i + 15
	};
}


ig.normalizeVendorAttribute(navigator, 'getGamepads');

if( !navigator.getGamepads ) {
	// No Gamepad support; nothing to do here
	return;
}

ig.Input.inject({
	// gamepad: null,
	currentButtonState: [], // array of vals, one for each gamepad
	lastButtons: [], // array of arrays of vals, one for each gamepad
	hasButtonObject: !!window.GamepadButton,

	getGamepadSnapshot: function(index) {
		var gamepads = navigator.getGamepads();
		if (gamepads && gamepads[index - 1]) {
			return gamepads[index - 1];
		}

		return null;
	},

	pollGamepad: function(index) {
		var gamepad = this.getGamepadSnapshot(index);

		if( !gamepad ) {
			// No gamepad snapshot?
			return;
		}

		this.lastButtons[index] = this.lastButtons[index] || [];

		// Iterate over all buttons, see if they're bound and check
		// for their state
		for( var button = 0; button < gamepad.buttons.length; button++ ) {
			var action = this.bindings[button+ig.GAMEPAD_BUTTON_OFFSET*index];

			// Is the button bound to an action?
			if( action ) {
				// Chrome behavior was changed
				this.currentButtonState[index] = gamepad.buttons[button].pressed;
				// this.currentButtonState[index] = this.hasButtonObject
				// 	? gamepad.buttons[button].pressed // W3C Standard 
				// 	: gamepad.buttons[button]; // Current Chrome version

				var prevState = this.lastButtons[index][button];
				
				// Was not pressed, but is now?
				if( !prevState && this.currentButtonState[index] ) {					
					this.actions[action] = true;
					this.presses[action] = true;
				}
				// Was pressed, but is no more?
				else if( prevState && !this.currentButtonState[index] ) {
					this.delayedKeyup[action] = true;
				}
			}

			this.lastButtons[index][button] = this.currentButtonState[index];
		}
	}
});

// Always poll gamepad before each frame
ig.Game.inject({
	run: function() {
		for (var i = 1; i <= 4; i++) {
			ig.input.pollGamepad(i);
		}
		
		this.parent();
	}
})

});

This is really slick, thank you for sharing!

I have a question though I hope you can help clarify. This script only detects the gamepads on startup, if the user connects or disconnects a gamepad, how can I accommodate? Hopefully this makes sense, thanks for your help!