Bootstrapping the Quintus Engine: Part II - HTML5 Mobile Game Development - page 177

if(loc.x < joypad.zone) {
joypad.joypadTouch = touch.identifier;
joypad.centerX = loc.x;
joypad.centerY = loc.y;
joypad.x = null;
joypad.y = null;
}
}
});
Q.el.on('touchmove',function(e) {
if(joypad.joypadTouch !== null) {
var evt = e.originalEvent;
for(var i=0,len=evt.changedTouches.length;i<len;i++) {
var touch = evt.changedTouches[i];
if(touch.identifier === joypad.joypadTouch) {
var loc = Q.input.touchLocation(touch),
dx = loc.x - joypad.centerX,
dy = loc.y - joypad.centerY,
dist = Math.sqrt(dx * dx + dy * dy),
overage = Math.max(1,dist / joypad.size),
ang = Math.atan2(dx,dy);
if(overage > 1) {
dx /= overage;
dy /= overage;
dist /= overage;
}
var triggers = [
dy < -joypad.trigger,
dx > joypad.trigger,
dy > joypad.trigger,
dx < -joypad.trigger
];
for(var k=0;k<triggers.length;k++) {
var actionName = joypad.inputs[k];
if(triggers[k]) {
Q.inputs[actionName] = true;
if(!joypad.triggers[k]) {
Q.input.trigger(actionName);
}