From 7ee2e1e54ef1ea8c6eceef87e46ec74e2cc23869 Mon Sep 17 00:00:00 2001
From: Kentai Radiquum <kentai.waah@gmail.com>
Date: Sun, 26 Jan 2025 05:14:15 +0500
Subject: [PATCH] add image lazy loading via observer API

---
 src/templates/components/Header.ejs           |  4 +-
 src/templates/components/Image.ejs            | 24 ++++++++
 src/templates/components/Link/Stickerset.ejs  | 23 +-------
 src/templates/components/Pack/Description.ejs | 25 +--------
 src/templates/components/Pack/Preview.ejs     | 23 +-------
 src/templates/functions.ejs                   | 13 +++++
 static/RenderImages.js                        | 55 +++++++++++--------
 static/tailwind.css                           | 13 ++---
 8 files changed, 81 insertions(+), 99 deletions(-)
 create mode 100644 src/templates/components/Image.ejs

diff --git a/src/templates/components/Header.ejs b/src/templates/components/Header.ejs
index cfbe8d2..63717fa 100644
--- a/src/templates/components/Header.ejs
+++ b/src/templates/components/Header.ejs
@@ -1,11 +1,11 @@
 <% include('/functions') %>
 <header class="sticky top-0 left-0 right-0 bg-[#1d1f3d] rounded-b-lg z-10">
-    <div class="container flex items-center justify-between px-8 py-4 mx-auto min-h-16">
+    <div class="container flex items-center justify-between gap-4 px-8 py-4 mx-auto min-h-16">
         <a href="<%- path %>/index.html"><img class="h-6 sm:h-10" src="<%- path %>/static/images/logo.svg" alt="index page"/></a>
         <% if (stickerset) { %>
             <div id="stickerpackname" class="-p-4 flex items-center gap-2 transition-transform translate-y-[var(--tw-translate-y)]" style="--tw-translate-y:-200%">
                 <img src="<%- CreateImageURL(homeserverUrl, stickerset.stickers[0].id) %>" class="object-contain w-8 aspect-square" />
-                <p class="text-lg sm:text-xl"><%- stickerset.title %></p>
+                <p class="text-lg sm:text-xl line-clamp-1"><%- stickerset.title %></p>
             </div>
         <% }; %>
         <div class="items-center justify-center hidden gap-2 text-white sm:flex sm:gap-4 sm:text-xl">
diff --git a/src/templates/components/Image.ejs b/src/templates/components/Image.ejs
new file mode 100644
index 0000000..ece8c8c
--- /dev/null
+++ b/src/templates/components/Image.ejs
@@ -0,0 +1,24 @@
+<% include('/functions'); %>
+<% var id; %>
+<% id = makeid(4); %>
+<div class="grid items-center justify-center object-contain w-16 grid-cols-1 grid-rows-1 sm:w-32 aspect-square">
+    <img data-image-src="<%- CreateImageURL(homeserverUrl, image) %>" data-image-id="<%- image %>-<%- id %>" class="invisible object-contain w-16 sm:w-32 aspect-square [grid-column:1] [grid-row:1]" />
+    <svg
+        role="status"
+        data-spinner-id="<%- image %>-<%- id %>"
+        aria-hidden="true"
+        class="mx-auto [grid-column:1] [grid-row:1] w-8 text-gray-200 sm:w-16 animate-spin dark:text-gray-600 fill-green-500"
+        viewBox="0 0 100 101"
+        fill="none"
+        xmlns="http://www.w3.org/2000/svg"
+    >
+        <path
+        d="M100 50.5908C100 78.2051 77.6142 100.591 50 100.591C22.3858 100.591 0 78.2051 0 50.5908C0 22.9766 22.3858 0.59082 50 0.59082C77.6142 0.59082 100 22.9766 100 50.5908ZM9.08144 50.5908C9.08144 73.1895 27.4013 91.5094 50 91.5094C72.5987 91.5094 90.9186 73.1895 90.9186 50.5908C90.9186 27.9921 72.5987 9.67226 50 9.67226C27.4013 9.67226 9.08144 27.9921 9.08144 50.5908Z"
+        fill="currentColor"
+        />
+        <path
+        d="M93.9676 39.0409C96.393 38.4038 97.8624 35.9116 97.0079 33.5539C95.2932 28.8227 92.871 24.3692 89.8167 20.348C85.8452 15.1192 80.8826 10.7238 75.2124 7.41289C69.5422 4.10194 63.2754 1.94025 56.7698 1.05124C51.7666 0.367541 46.6976 0.446843 41.7345 1.27873C39.2613 1.69328 37.813 4.19778 38.4501 6.62326C39.0873 9.04874 41.5694 10.4717 44.0505 10.1071C47.8511 9.54855 51.7191 9.52689 55.5402 10.0491C60.8642 10.7766 65.9928 12.5457 70.6331 15.2552C75.2735 17.9648 79.3347 21.5619 82.5849 25.841C84.9175 28.9121 86.7997 32.2913 88.1811 35.8758C89.083 38.2158 91.5421 39.6781 93.9676 39.0409Z"
+        fill="currentFill"
+        />
+    </svg>
+</div>
\ No newline at end of file
diff --git a/src/templates/components/Link/Stickerset.ejs b/src/templates/components/Link/Stickerset.ejs
index 26ba4d7..2cbf1db 100644
--- a/src/templates/components/Link/Stickerset.ejs
+++ b/src/templates/components/Link/Stickerset.ejs
@@ -1,26 +1,5 @@
-<% include('/functions') %>
 <a href="<%- path %>/<%- pack.id %>" class="flex items-center w-full h-full gap-2 p-4 rounded-md sm:gap-4 bg-slate-800">
-    <div class="grid items-center justify-center object-contain w-16 grid-cols-1 grid-rows-1 sm:w-32 aspect-square">
-        <img src="<%- CreateImageURL(homeserverUrl, pack.image) %>" data-image-id="<%- pack.image %>" class="object-contain w-16 sm:w-32 aspect-square [grid-column:1] [grid-row:1]" loading="lazy" />
-        <svg
-            role="status"
-            data-spinner-id="<%- pack.image %>"
-            aria-hidden="true"
-            class="mx-auto [grid-column:1] [grid-row:1] inline w-8 text-gray-200 sm:w-16 animate-spin dark:text-gray-600 fill-green-500"
-            viewBox="0 0 100 101"
-            fill="none"
-            xmlns="http://www.w3.org/2000/svg"
-        >
-            <path
-            d="M100 50.5908C100 78.2051 77.6142 100.591 50 100.591C22.3858 100.591 0 78.2051 0 50.5908C0 22.9766 22.3858 0.59082 50 0.59082C77.6142 0.59082 100 22.9766 100 50.5908ZM9.08144 50.5908C9.08144 73.1895 27.4013 91.5094 50 91.5094C72.5987 91.5094 90.9186 73.1895 90.9186 50.5908C90.9186 27.9921 72.5987 9.67226 50 9.67226C27.4013 9.67226 9.08144 27.9921 9.08144 50.5908Z"
-            fill="currentColor"
-            />
-            <path
-            d="M93.9676 39.0409C96.393 38.4038 97.8624 35.9116 97.0079 33.5539C95.2932 28.8227 92.871 24.3692 89.8167 20.348C85.8452 15.1192 80.8826 10.7238 75.2124 7.41289C69.5422 4.10194 63.2754 1.94025 56.7698 1.05124C51.7666 0.367541 46.6976 0.446843 41.7345 1.27873C39.2613 1.69328 37.813 4.19778 38.4501 6.62326C39.0873 9.04874 41.5694 10.4717 44.0505 10.1071C47.8511 9.54855 51.7191 9.52689 55.5402 10.0491C60.8642 10.7766 65.9928 12.5457 70.6331 15.2552C75.2735 17.9648 79.3347 21.5619 82.5849 25.841C84.9175 28.9121 86.7997 32.2913 88.1811 35.8758C89.083 38.2158 91.5421 39.6781 93.9676 39.0409Z"
-            fill="currentFill"
-            />
-        </svg>
-    </div>
+    <%- include('/components/Image', {homeserverUrl, image: pack.image}); %>
     <div>
         <p class="text-lg sm:text-2xl line-clamp-1"><%- pack.name %></p>
         <p class="text-sm sm:text-lg line-clamp-1"><%- pack.author %></p>
diff --git a/src/templates/components/Pack/Description.ejs b/src/templates/components/Pack/Description.ejs
index f4c5f89..2d2935a 100644
--- a/src/templates/components/Pack/Description.ejs
+++ b/src/templates/components/Pack/Description.ejs
@@ -1,27 +1,8 @@
-<% include('/functions') %>
 <div class="flex items-center w-full h-full gap-2 py-2 rounded-md bg-slate-800 sm:gap-4" id="stickerpackdesc">
-    <div class="grid items-center justify-center object-contain w-24 grid-cols-1 grid-rows-1 sm:w-32 aspect-square">
-        <img src="<%- CreateImageURL(homeserverUrl, stickerset.stickers[0].id) %>" data-image-id="<%- stickerset.stickers[0].id %>-Icon" class="object-contain w-24 sm:w-32 aspect-square [grid-column:1] [grid-row:1]" loading="lazy" />
-        <svg
-            role="status"
-            data-spinner-id="<%- stickerset.stickers[0].id %>-Icon"
-            aria-hidden="true"
-            class="mx-auto [grid-column:1] [grid-row:1] inline w-8 text-gray-200 sm:w-16 animate-spin dark:text-gray-600 fill-green-500"
-            viewBox="0 0 100 101"
-            fill="none"
-            xmlns="http://www.w3.org/2000/svg"
-        >
-            <path
-            d="M100 50.5908C100 78.2051 77.6142 100.591 50 100.591C22.3858 100.591 0 78.2051 0 50.5908C0 22.9766 22.3858 0.59082 50 0.59082C77.6142 0.59082 100 22.9766 100 50.5908ZM9.08144 50.5908C9.08144 73.1895 27.4013 91.5094 50 91.5094C72.5987 91.5094 90.9186 73.1895 90.9186 50.5908C90.9186 27.9921 72.5987 9.67226 50 9.67226C27.4013 9.67226 9.08144 27.9921 9.08144 50.5908Z"
-            fill="currentColor"
-            />
-            <path
-            d="M93.9676 39.0409C96.393 38.4038 97.8624 35.9116 97.0079 33.5539C95.2932 28.8227 92.871 24.3692 89.8167 20.348C85.8452 15.1192 80.8826 10.7238 75.2124 7.41289C69.5422 4.10194 63.2754 1.94025 56.7698 1.05124C51.7666 0.367541 46.6976 0.446843 41.7345 1.27873C39.2613 1.69328 37.813 4.19778 38.4501 6.62326C39.0873 9.04874 41.5694 10.4717 44.0505 10.1071C47.8511 9.54855 51.7191 9.52689 55.5402 10.0491C60.8642 10.7766 65.9928 12.5457 70.6331 15.2552C75.2735 17.9648 79.3347 21.5619 82.5849 25.841C84.9175 28.9121 86.7997 32.2913 88.1811 35.8758C89.083 38.2158 91.5421 39.6781 93.9676 39.0409Z"
-            fill="currentFill"
-            />
-        </svg>
+    <div class="px-2">
+        <%- include('/components/Image', {homeserverUrl, image: stickerset.stickers[0].id}); %>
     </div>
-    <div class="px-4">
+    <div class="px-2">
         <p class="text-xl font-bold sm:text-2xl line-clamp-1"><%- stickerset.title %></p>
         <% if (stickerset.hasOwnProperty("author") && stickerset.author.hasOwnProperty("name") && stickerset.author.name) { %>
             <% if (stickerset.author.hasOwnProperty("url") && stickerset.author.url) { %>
diff --git a/src/templates/components/Pack/Preview.ejs b/src/templates/components/Pack/Preview.ejs
index 4793bc1..dec4c38 100644
--- a/src/templates/components/Pack/Preview.ejs
+++ b/src/templates/components/Pack/Preview.ejs
@@ -1,29 +1,8 @@
-<% include('/functions') %>
 <div class="w-full h-full px-4 py-2 rounded-md sm:px-8 bg-slate-800 sm:gap-4">
     <p class="mb-4 text-lg border-b md:text-2xl border-slate-400"><%- stickerset.stickers.length %> stickers</p>
     <div class="grid w-full h-full grid-cols-3 gap-2 lg:grid-cols-3 sm:grid-cols-4 xl:grid-cols-4 2xl:grid-cols-5">
         <% stickerset.stickers.forEach(function(sticker){ %>
-            <div class="grid items-center justify-center object-contain w-24 grid-cols-1 grid-rows-1 sm:w-32 aspect-square">
-                <img src="<%- CreateImageURL(homeserverUrl, sticker.id) %>" data-image-id="<%- sticker.id %>" class="object-contain w-24 sm:w-32 aspect-square [grid-column:1] [grid-row:1]" loading="lazy" />
-                <svg
-                    role="status"
-                    data-spinner-id="<%- sticker.id %>"
-                    aria-hidden="true"
-                    class="mx-auto [grid-column:1] [grid-row:1] inline w-8 text-gray-200 sm:w-16 animate-spin dark:text-gray-600 fill-green-500"
-                    viewBox="0 0 100 101"
-                    fill="none"
-                    xmlns="http://www.w3.org/2000/svg"
-                >
-                    <path
-                    d="M100 50.5908C100 78.2051 77.6142 100.591 50 100.591C22.3858 100.591 0 78.2051 0 50.5908C0 22.9766 22.3858 0.59082 50 0.59082C77.6142 0.59082 100 22.9766 100 50.5908ZM9.08144 50.5908C9.08144 73.1895 27.4013 91.5094 50 91.5094C72.5987 91.5094 90.9186 73.1895 90.9186 50.5908C90.9186 27.9921 72.5987 9.67226 50 9.67226C27.4013 9.67226 9.08144 27.9921 9.08144 50.5908Z"
-                    fill="currentColor"
-                    />
-                    <path
-                    d="M93.9676 39.0409C96.393 38.4038 97.8624 35.9116 97.0079 33.5539C95.2932 28.8227 92.871 24.3692 89.8167 20.348C85.8452 15.1192 80.8826 10.7238 75.2124 7.41289C69.5422 4.10194 63.2754 1.94025 56.7698 1.05124C51.7666 0.367541 46.6976 0.446843 41.7345 1.27873C39.2613 1.69328 37.813 4.19778 38.4501 6.62326C39.0873 9.04874 41.5694 10.4717 44.0505 10.1071C47.8511 9.54855 51.7191 9.52689 55.5402 10.0491C60.8642 10.7766 65.9928 12.5457 70.6331 15.2552C75.2735 17.9648 79.3347 21.5619 82.5849 25.841C84.9175 28.9121 86.7997 32.2913 88.1811 35.8758C89.083 38.2158 91.5421 39.6781 93.9676 39.0409Z"
-                    fill="currentFill"
-                    />
-                </svg>
-            </div>
+            <%- include('/components/Image', {homeserverUrl, image: sticker.id}); %>
         <% }); %>
     </div>
 
diff --git a/src/templates/functions.ejs b/src/templates/functions.ejs
index 4719398..5fde1e3 100644
--- a/src/templates/functions.ejs
+++ b/src/templates/functions.ejs
@@ -16,4 +16,17 @@ PackRatingClass=function(rating) {
             break
     }
 }
+%>
+<%
+makeid=function(length) {
+    let result = '';
+    const characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+    const charactersLength = characters.length;
+    let counter = 0;
+    while (counter < length) {
+      result += characters.charAt(Math.floor(Math.random() * charactersLength));
+      counter += 1;
+    }
+    return result;
+}
 %>
\ No newline at end of file
diff --git a/static/RenderImages.js b/static/RenderImages.js
index b26f0e8..b094126 100644
--- a/static/RenderImages.js
+++ b/static/RenderImages.js
@@ -1,26 +1,35 @@
 const images = document.querySelectorAll("[data-image-id]");
-images.forEach((image, i) => {
-  if (i < 4) {
-    image.setAttribute("loading", "eager");
+
+let observer = new IntersectionObserver(function(entries, self) {
+  for (let entry of entries) {
+    if (entry.isIntersecting) {
+      let elem = entry.target;
+      preload_image(elem);
+      self.unobserve(elem);
+    }
   }
-
-  const spinner = document.querySelector(
-    `[data-spinner-id="${image.getAttribute("data-image-id")}"]`
-  );
-
-  if (image.height > 0 && image.complete) {
-    image.classList.remove("invisible");
-    spinner.classList.add("invisible");
-    return;
-  } else {
-    image.classList.add("invisible");
-    spinner.classList.remove("invisible");
-  }
-
-  image.addEventListener("load", () => {
-    console.log("image " + image.getAttribute("data-image-id") + " loaded");
-    image.classList.remove("invisible");
-    spinner.classList.add("invisible");
-    image.removeEventListener("load", this);
-  });
+}, {
+  rootMargin: '400px 400px 400px 400px'
+});
+
+function preload_image(img) {
+  img.src = img.dataset.imageSrc;
+  img.setAttribute("loading", "eager")
+  const id = img.dataset.imageId
+  const spinner = document.querySelector(`[data-spinner-id="${id}"]`);
+
+  console.log(`Loading ${id}`);
+  img.addEventListener("load", () => {
+    console.log(`image ${id} loaded`);
+    img.classList.remove("invisible");
+    spinner.classList.add("invisible");
+    img.removeEventListener("load", this);
+  });
+}
+
+images.forEach((image, i) => {
+  if (i <= 5) {
+    image.setAttribute("loading", "eager"); // should eager load first 6 (0-5) images
+  }
+  observer.observe(image)
 });
diff --git a/static/tailwind.css b/static/tailwind.css
index b54ece5..d8af1e2 100644
--- a/static/tailwind.css
+++ b/static/tailwind.css
@@ -648,10 +648,6 @@ video {
   display: block;
 }
 
-.inline {
-  display: inline;
-}
-
 .flex {
   display: flex;
 }
@@ -697,10 +693,6 @@ video {
   width: 4rem;
 }
 
-.w-24 {
-  width: 6rem;
-}
-
 .w-8 {
   width: 2rem;
 }
@@ -839,6 +831,11 @@ video {
   padding: 1rem;
 }
 
+.px-2 {
+  padding-left: 0.5rem;
+  padding-right: 0.5rem;
+}
+
 .px-4 {
   padding-left: 1rem;
   padding-right: 1rem;