// ==UserScript==
// @name        Smart scrolling
// @namespace   [email protected]
// @description Prevent scrolling issues when page is resized by loading images
// @include     *
// @version     1.4
// @grant       none
// @run-at      document-start
// ==/UserScript==
(function() {
var hash = location.hash.replace("#", "");
if(hash) {
var scrollListener = function() {removeEventListener("wheel", scrollListener); hash = "";};
addEventListener("wheel", scrollListener);
}
var images;
var update = function() {
var scrollY = 0, ready = document.readyState == "complete", elem;
if(hash) {
elem = document.getElementById(hash) || document.getElementsByName(hash)[0];
if(elem) scrollY = Math.round(elem.getBoundingClientRect().top);
} else if(document.readyState == "interactive") {
if(!images) images = [].slice.call(document.getElementsByTagName("IMG"));
var overflows = ["auto", "scroll"], data, rect, height;
for(var i = 0; i < images.length; i++) {
if(!images[i].zssData) images[i].zssData = {};
data = images[i].zssData;
if(ready) delete images[i].zssData;
if(data.complete) continue;
rect   = images[i].getBoundingClientRect();
height = Math.max(data.height || 0, Math.round(rect.bottom - rect.top));
if(isNaN(data.height)) {
if(images[i].complete || !images[i].offsetParent || getComputedStyle(images[i]).position == "fixed")
data.complete = true;
else
data.height = height;
} else if(data.height != height) {
data.complete = true;
if(rect.top >= 0) continue;
elem = images[i];
while(true) {
elem = elem.parentNode;
if(elem == document.body) {
scrollY += height - data.height;
break;
} else if(overflows.includes(getComputedStyle(elem).overflow)) {
elem.scrollTop += height - data.height;
break;
}
}
}
}
}
if(scrollY !== 0) scrollBy(0, scrollY);
if(!ready) requestAnimationFrame(update);
};
update();
})();