|
| 1 | +/* |
| 2 | + * @author Mikel Tuesta <[email protected]> |
| 3 | + */ |
| 4 | +'use strict'; |
| 5 | + |
| 6 | +(function (window, DomHelpers, ScrollProxyListener, _) { |
| 7 | + |
| 8 | + /** |
| 9 | + * ParallaxController - Singleton |
| 10 | + * |
| 11 | + * @constructor |
| 12 | + */ |
| 13 | + var ScrollProxy = (function () { |
| 14 | + var instance; |
| 15 | + |
| 16 | + function ScrollProxy() { |
| 17 | + var latestKnownScrollY = window.pageYOffset, |
| 18 | + animating = false, |
| 19 | + windowDimensions = { |
| 20 | + height: -1, |
| 21 | + width: -1 |
| 22 | + }, |
| 23 | + listeners = []; |
| 24 | + |
| 25 | + var notifyListeners = function () { |
| 26 | + var args = Array.prototype.slice.call(arguments), |
| 27 | + methodName = args.splice(0, 1); |
| 28 | + for (var i = 0; i < listeners.length; i++) { |
| 29 | + listeners[i][methodName].apply(listeners[i], args); |
| 30 | + } |
| 31 | + }; |
| 32 | + var requestFrame = function () { |
| 33 | + if (!animating) { |
| 34 | + window.requestAnimationFrame(doFrame); |
| 35 | + } |
| 36 | + animating = true; |
| 37 | + }; |
| 38 | + var doFrame = function () { |
| 39 | + notifyListeners('doFrame'); |
| 40 | + animating = false; |
| 41 | + }; |
| 42 | + var onScroll = function () { |
| 43 | + latestKnownScrollY = window.pageYOffset; |
| 44 | + notifyListeners('onScroll', latestKnownScrollY); |
| 45 | + requestFrame(); |
| 46 | + }; |
| 47 | + var onResize = function () { |
| 48 | + windowDimensions = DomHelpers.getWindowDimensions(); |
| 49 | + notifyListeners('onResize', windowDimensions); |
| 50 | + }; |
| 51 | + var bindListeners = function () { |
| 52 | + window.addEventListener('scroll', onScroll); |
| 53 | + window.addEventListener('resize', _.debounce(onResize, 200)); |
| 54 | + }; |
| 55 | + var addListener = function (listener) { |
| 56 | + if (!(listener instanceof ScrollProxyListener)) { |
| 57 | + throw 'Provided listener must be an instance of ScrollProxyListener.'; |
| 58 | + } |
| 59 | + listeners.push(listener); |
| 60 | + }; |
| 61 | + var removeListener = function (listener) { |
| 62 | + var listenerIndex = listeners.indexOf(listener); |
| 63 | + if (listenerIndex !== -1) { |
| 64 | + listeners.splice(listenerIndex, 1); |
| 65 | + } |
| 66 | + }; |
| 67 | + var init = function () { |
| 68 | + windowDimensions = DomHelpers.getWindowDimensions(); |
| 69 | + bindListeners(); |
| 70 | + }; |
| 71 | + init(); |
| 72 | + |
| 73 | + return { |
| 74 | + addListener: addListener, |
| 75 | + removeListener: removeListener |
| 76 | + } |
| 77 | + } |
| 78 | + |
| 79 | + return { |
| 80 | + getInstance: function () { |
| 81 | + if (!instance) { |
| 82 | + instance = new ScrollProxy(); |
| 83 | + } |
| 84 | + return instance; |
| 85 | + } |
| 86 | + }; |
| 87 | + })(); |
| 88 | + |
| 89 | + // Expose ScrollProxy |
| 90 | + window.ScrollProxy = ScrollProxy; |
| 91 | + |
| 92 | +})(window, window.DomHelpers, window.ScrollProxyListener, _); |
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