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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.

2022-03-08 يوللانغان نەشرى. ئەڭ يېڭى نەشرىنى كۆرۈش.

// ==UserScript==
// @name         Better Reddit Image Previews
// @namespace    https://lawrenzo.com/p/better-reddit-image-previews
// @version      0.4.0
// @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() {
    //-------------------------------------------------------------------------------------
    // post and gallery watchers
    //-------------------------------------------------------------------------------------
    var postWatcher = null,
        galleryWatcher = null;
    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.forEach(node => node.nodeName == "IMG" && fixImage(node, true));
            });
        });
    }
    //-------------------------------------------------------------------------------------
    // processing and image fixing
    //-------------------------------------------------------------------------------------
    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);
    }
    function processNodes(nodes) {
        nodes.forEach(node => {
            if(!node || !node.querySelectorAll) return;
            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);
                });
        });
    }
    //-------------------------------------------------------------------------------------
    // feed related, only used if not using reddit watcher
    //-------------------------------------------------------------------------------------
    function getFeedWrapper() {
        let listingLayout = document.querySelector(".ListingLayout-outerContainer"),
            firstPost     = listingLayout && listingLayout.querySelector("div[data-testid='post-container']"),
            feedWrapper   = firstPost && firstPost.parentNode;
        while(feedWrapper && !feedWrapper.nextSibling) {
            if(feedWrapper == listingLayout) return null;
            feedWrapper = feedWrapper.parentNode || null;
        }
        return feedWrapper && feedWrapper.parentNode;
    }
    var feedWatcher = null;
    function resetFeedWatcher(feedWrapper) {
        if(feedWatcher) feedWatcher.disconnect();
        feedWatcher = new MutationObserver(mutated => {
            mutated.forEach(mutant => processNodes(mutant.addedNodes))
        });
        feedWatcher.observe(feedWrapper, {childList:true});
    }
    //-------------------------------------------------------------------------------------
    //
    //-------------------------------------------------------------------------------------
    function reset(feed) {
        resetGalleryWatcher();
        resetPostWatcher();
        if(feed) processNodes([feed]);
    }
    if(!window.redditWatcher) {
        let lastFirstPost = null;
        (new MutationObserver(() => {
            let feedWrapper = getFeedWrapper(),
                firstPost = feedWrapper && feedWrapper.children[0];
            if(firstPost !== lastFirstPost) {
                reset(feedWrapper);
                resetFeedWatcher(feedWrapper);
                lastFirstPost = firstPost;
            }
        })).observe(document.body, {childList:true, subtree:true});
    } else {
        reset(document.querySelector(".ListingLayout-outerContainer"));
        window.redditWatcher.feed.onChange(feed => reset(feed));
        window.redditWatcher.feed.onUpdate((feed, mutated) => {
            if(mutated) mutated.forEach(mutant => processNodes(mutant.addedNodes));
        });
    }
})();