Preloads and dynamically displays preview images below links, avoiding duplicate previews. Implements fallback to the next image if the first fails to load. Includes debug mode.
// ==UserScript==
// @name Pornolab Preloaded Preview
// @version 1.6.5
// @description Preloads and dynamically displays preview images below links, avoiding duplicate previews. Implements fallback to the next image if the first fails to load. Includes debug mode.
// @author Ace
// @license MIT
// @match *://pornolab.net/forum/tracker*
// @match *://pornolab.net/forum/viewforum*
// @match *://pornolab.net/forum/search*
// @icon https://static.pornolab.net/favicon.ico
// @run-at document-end
// @grant none
// @namespace https://greasyfork.org/users/1418199
// ==/UserScript==
(async function () {
"use strict";
/* ================= CONFIG ================= */
const MIN_HEIGHT = 201;
const MAX_CONCURRENT_FETCHES = 5;
const PREVIEW_HEIGHT = "17rem";
/* ================= STYLES ================= */
const style = document.createElement("style");
style.textContent = `
.preview-container {
height: ${PREVIEW_HEIGHT};
display: flex;
justify-content: center;
align-items: center;
overflow: hidden;
margin-top: 0.5rem;
background: #111;
border-radius: 6px;
font-size: 0.9rem;
color: #888;
}
.preview-container img {
max-width: 100%;
max-height: 100%;
object-fit: contain;
display: block;
}
/* Aspect-aware soft constraints */
.preview-container img.portrait {
max-width: 70%;
}
.preview-container img.landscape {
max-height: 80%;
}
`;
document.head.appendChild(style);
/* ================= CACHE ================= */
// Session-only cache: topic URL -> array of preview URLs
const previewCache = new Map();
/* ================= HELPERS ================= */
function buildUrl(link) {
// IMPORTANT: preserve /forum/ path
return new URL(link.getAttribute("href"), location.href).href;
}
async function fetchPreviewUrls(url) {
if (previewCache.has(url)) {
return previewCache.get(url);
}
const res = await fetch(url);
if (!res.ok) {
previewCache.set(url, []);
return [];
}
const html = await res.text();
const doc = new DOMParser().parseFromString(html, "text/html");
// Forum structure guarantee:
// <var class="postImg" title="FULL_IMAGE_URL">
const urls = [...doc.querySelectorAll(".postImg")]
.map(el => el.getAttribute("title"))
.filter(Boolean);
previewCache.set(url, urls);
return urls;
}
function attachFallbackAndAspectLogic(img, urls) {
let index = 0;
const tryNext = () => {
index++;
if (index < urls.length) {
img.src = urls[index];
} else {
img.replaceWith(createEmptyPlaceholder());
}
};
img.addEventListener("error", tryNext);
img.addEventListener("load", () => {
// Reject small images
if (img.naturalHeight < MIN_HEIGHT) {
tryNext();
return;
}
// Aspect-aware refinement (cheap, one-time)
const ratio = img.naturalWidth / img.naturalHeight;
if (ratio < 0.75) {
img.classList.add("portrait");
} else if (ratio > 1.6) {
img.classList.add("landscape");
}
});
}
function createEmptyPlaceholder() {
const div = document.createElement("div");
div.className = "preview-container";
div.textContent = "No Eligible preview found";
return div;
}
function insertPreview(link, urls) {
const container = document.createElement("div");
container.className = "preview-container";
if (!urls.length) {
container.textContent = "No Eligible preview found";
link.after(container);
return;
}
const img = document.createElement("img");
img.loading = "lazy";
img.src = urls[0];
attachFallbackAndAspectLogic(img, urls);
container.appendChild(img);
link.after(container);
}
/* ================= PROCESSING ================= */
const links = [...document.querySelectorAll(".tLink, .tt-text")];
let index = 0;
async function worker() {
while (index < links.length) {
const link = links[index++];
if (link.dataset.previewDone) continue;
link.dataset.previewDone = "1";
try {
const urls = await fetchPreviewUrls(buildUrl(link));
insertPreview(link, urls);
} catch {
insertPreview(link, []);
}
}
}
// Run workers (ordered, balanced)
await Promise.all(
Array.from({ length: MAX_CONCURRENT_FETCHES }, worker)
);
})();
