Created
June 28, 2015 03:07
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Userscript to fix scroll position to viewport center element when resizing
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| // ==UserScript== | |
| // @name Retain Scroll Position | |
| // @namespace http://cssu.in | |
| // @description Fixes scroll position to viewport center element when resizing | |
| // @include * | |
| // @version 0.1 | |
| // @grant none | |
| // @noframes | |
| // ==/UserScript== | |
| (function() { | |
| "use strict"; | |
| function get_absolute_offset(element) { | |
| var left = 0, | |
| top = 0; | |
| do { | |
| left += element.offsetLeft; | |
| top += element.offsetTop; | |
| element = element.offsetParent; | |
| } while(element); | |
| return { | |
| left: left, | |
| top: top | |
| }; | |
| } | |
| function get_center_element() { | |
| var center = [ | |
| window.innerWidth / 2, | |
| window.innerHeight / 2 | |
| ].map(Math.round); | |
| return document.elementFromPoint(center[0], center[1]); | |
| } | |
| var page_anchor = get_center_element(); | |
| window.addEventListener("resize", function() { | |
| var offset = get_absolute_offset(page_anchor); | |
| window.scroll( | |
| offset.left - ((window.innerWidth / 2) - (page_anchor.clientWidth / 2)), | |
| offset.top - ((window.innerHeight / 2) - (page_anchor.clientHeight / 2))); | |
| }, false); | |
| window.addEventListener("scroll", function() { | |
| page_anchor = get_center_element(); | |
| }, false); | |
| })(); |
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