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Better Reddit Image Previews

Fixes issues with reddit image previews. Specifically, clicking image preview now links directly to image (instead of thread) and fits height of image previews in carousel so they don't get clipped out.

As of 2022-03-07. See the latest version.

// ==UserScript==
// @name         Better Reddit Image Previews
// @namespace    https://lawrenzo.com/p/better-reddit-image-previews
// @version      0.3.0
// @description  Fixes issues with reddit image previews. Specifically, clicking image preview now links directly to image (instead of thread) and fits height of image previews in carousel so they don't get clipped out.
// @author       Lawrence Sim
// @license      WTFPL (http://www.wtfpl.net)
// @grant        none
// @match        *://*.reddit.com/*
// ==/UserScript==
'use strict';
(function() {
    function fixImage(img, fixHeight) {
        if(!img || img.getAttribute("ifix")) return;
        if(fixHeight) {
            img.style.height = "100%";
            img.parentElement.style.height = "100%";
        }
        img.addEventListener("click", evt => {
            window.open(img.getAttribute("src").replace("preview.redd.it", "i.redd.it"));
            evt.stopPropagation();
            evt.preventDefault();
        });
        img.setAttribute("ifix", 1);
    }
    var feedWatcher    = null,
        postWatcher    = null,
        galleryWatcher = null;
    function processNodes(nodes) {
        nodes.forEach(node => {
            node.querySelectorAll("div[data-testid='post-container']")
                .forEach(post => {
                    if(post.getAttribute("ifix")) return;
                    let postbg = post.querySelector("[data-click-id='background']");
                    if(postbg) postWatcher.observe(postbg, {childList:true});
                    post.setAttribute("ifix", 1);
                });
        });
    }
    function resetFeedWatcher(feedWrapper) {
        if(feedWatcher) feedWatcher.disconnect();
        feedWatcher = new MutationObserver(mutated => {
            mutated.forEach(mutant => processNodes(mutant.addedNodes))
        });
        feedWatcher.observe(feedWrapper, {childList:true});
    }
    function resetPostWatcher() {
        if(postWatcher) postWatcher.disconnect();
        postWatcher = new MutationObserver(mutated => {
            mutated[0].addedNodes.forEach(node => {
                if(!node.querySelectorAll) return
                node.querySelectorAll("img[alt='Post image']")
                    .forEach(img => fixImage(img));
                let gallery = node.querySelector("ul");
                if(gallery) {
                    galleryWatcher.observe(gallery, {childList: true, subtree:true});
                    gallery.querySelectorAll("li figure img")
                        .forEach(img => fixImage(img, true));
                }
            });
        });
    }
    function resetGalleryWatcher() {
        if(galleryWatcher) galleryWatcher.disconnect();
        galleryWatcher = new MutationObserver(mutated => {
            mutated.forEach(mutant => {
                mutant.addedNodes.filter(node => node.nodeName == "IMG")
                                 .forEach(node => fixImage(node, true));
            });
        });
    }
    var lastFeedWrapper = null;
    (new MutationObserver(() => {
        let listingLayout = document.querySelector(".ListingLayout-outerContainer"),
            firstPost     = listingLayout && listingLayout.querySelector("div[data-testid='post-container']"),
            feedWrapper   = firstPost && firstPost.parentNode.parentNode.parentNode;
        if(feedWrapper && feedWrapper !== lastFeedWrapper) {
            resetGalleryWatcher();
            resetPostWatcher();
            processNodes([feedWrapper]);
            resetFeedWatcher(feedWrapper);
            lastFeedWrapper = feedWrapper;
        }
    })).observe(document.body, {childList:true, subtree:true});
})();