paper.js/src/dom/DomEvent.js

/*
 * Paper.js - The Swiss Army Knife of Vector Graphics Scripting.
 * http://paperjs.org/
 *
 * Copyright (c) 2011 - 2014, Juerg Lehni & Jonathan Puckey
 * http://scratchdisk.com/ & http://jonathanpuckey.com/
 *
 * Distributed under the MIT license. See LICENSE file for details.
 *
 * All rights reserved.
 */

/**
 * @name DomEvent
 * @namespace
 * @private
 */
var DomEvent = /** @lends DomEvent */{
	add: function(el, events) {
		for (var type in events) {
			var func = events[type],
				parts = type.split(/[\s,]+/g);
			for (var i = 0, l = parts.length; i < l; i++)
				el.addEventListener(parts[i], func, false);
		}
	},

	remove: function(el, events) {
		for (var type in events) {
			var func = events[type],
				parts = type.split(/[\s,]+/g);
			for (var i = 0, l = parts.length; i < l; i++)
				el.removeEventListener(parts[i], func, false);
		}
	},

	getPoint: function(event) {
		var pos = event.targetTouches
				? event.targetTouches.length
					? event.targetTouches[0]
					: event.changedTouches[0]
				: event;
		return new Point(
			pos.pageX || pos.clientX + document.documentElement.scrollLeft,
			pos.pageY || pos.clientY + document.documentElement.scrollTop
		);
	},

	getTarget: function(event) {
		return event.target || event.srcElement;
	},

	getRelatedTarget: function(event) {
		return event.relatedTarget || event.toElement;
	},

	getOffset: function(event, target) {
		// Remove target offsets from page coordinates
		return DomEvent.getPoint(event).subtract(DomElement.getOffset(
				target || DomEvent.getTarget(event)));
	},

	stop: function(event) {
		event.stopPropagation();
		event.preventDefault();
	}
};

DomEvent.requestAnimationFrame = new function() {
	var nativeRequest = DomElement.getPrefixed(window, 'requestAnimationFrame'),
		requested = false,
		callbacks = [],
		focused = true,
		timer;

	DomEvent.add(window, {
		focus: function() {
			focused = true;
		},
		blur: function() {
			focused = false;
		}
	});

	function handleCallbacks() {
		// Checks all installed callbacks for element visibility and
		// execute if needed.
		for (var i = callbacks.length - 1; i >= 0; i--) {
			var entry = callbacks[i],
				func = entry[0],
				el = entry[1];
			if (!el || (PaperScope.getAttribute(el, 'keepalive') == 'true'
					|| focused) && DomElement.isInView(el)) {
				// Only remove from the list once the callback was called. This
				// could take a long time based on visibility. But this way we
				// are sure to keep the animation loop running.
				callbacks.splice(i, 1);
				func();
			}
		}
		if (nativeRequest) {
			if (callbacks.length) {
				// If we haven't processed all callbacks yet, we need to keep
				// the loop running, as otherwise it would die off.
				nativeRequest(handleCallbacks);
			} else {
				requested = false;
			}
		}
	}

	return function(callback, element) {
		// Add to the list of callbacks to be called in the next animation
		// frame.
		callbacks.push([callback, element]);
		if (nativeRequest) {
			// Handle animation natively. We only need to request the frame
			// once for all collected callbacks.
			if (!requested) {
				nativeRequest(handleCallbacks);
				requested = true;
			}
		} else if (!timer) {
			// Install interval timer that checks all callbacks. This
			// results in faster animations than repeatedly installing
			// timout timers.
			timer = setInterval(handleCallbacks, 1000 / 60);
		}
	};
};