collage fixes

README.md

@@ -94,8 +94,9 @@ The template also accepts a raw URL string or standard CasparCG XML
 
 ## Collage
 
-Use `/collage` to render multiple social posts as a vertically scrolling strip.
-Posts are repeated in the track so the motion keeps filling gaps.
+Use `/collage` to render multiple social posts as independently scrolling
+columns. The browser keeps only a small window of live posts per column, removes
+cards after they scroll off the top, and fills new random cards at the bottom.
 
 Repeated `url` parameters:
 
@@ -114,12 +115,15 @@ Useful collage parameters:
 - `spacing`: pixels between a post and anything else, including screen edges and other posts, default `48`.
 - `fade`: optional pixels used to fade posts in/out at the top and bottom edges, default `0`.
 - `columns`: number of post columns, default `3`.
+- `repeatDistance`: minimum pixel distance before the same post can be reused near another live copy, default `900`.
+- `hydrateDelay`: milliseconds between hydrating newly inserted provider embeds, default `180`.
 - `duration`: seconds per scroll loop, default `360`.
-- `repeat`: number of times to repeat the post list in each half of the loop, default `4`.
+- `repeat`: virtual scroll buffer multiplier, default `2`.
 - `shuffle`: `1` to randomize post order on each page load, default `1`.
 
-Collage card width is calculated from `width`, `spacing`, and `columns`,
-then capped at `500px`, so all columns fit within the configured screen width.
+Collage card width is calculated from `width`, `spacing`, and `columns` so the
+columns fill the configured screen width with only the chosen spacing at the
+edges.
 
 ## API
 

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "dev": "node --watch src/server.js",
     "start": "node src/server.js",
-    "typecheck": "node --check src/server.js && node --check src/oembed.js && node --check src/providers.js && node --check src/templates.js && node --check public/caspar.js",
+    "typecheck": "node --check src/server.js && node --check src/oembed.js && node --check src/providers.js && node --check src/templates.js && node --check public/caspar.js && node --check public/collage.js",
     "build": "npm run typecheck",
     "test": "node --test"
   },

public/collage.js

@@ -0,0 +1,279 @@
+const dataElement = document.getElementById("collage-data");
+const stage = document.querySelector(".collage-stage");
+const track = document.querySelector(".collage-track");
+const config = JSON.parse(dataElement.textContent);
+
+let lastFrame = performance.now();
+let itemCursor = 0;
+const columns = [];
+const deviceScale = window.devicePixelRatio || 1;
+const hydrationQueue = [];
+const hydrateDelay = Math.max(Number(config.hydrateDelay) || 0, 0);
+const placeholderHeight = 160;
+const cardColumns = new WeakMap();
+let trackTop = 0;
+let hydrationTimer;
+const cardObserver = new ResizeObserver((entries) => {
+  for (const entry of entries) {
+    const card = entry.target;
+    const column = cardColumns.get(card);
+    const previousExtent = cardExtent(card);
+
+    card.dataset.height = String(Math.max(entry.contentRect.height, placeholderHeight));
+
+    if (column) {
+      column.contentHeight += cardExtent(card) - previousExtent;
+    }
+  }
+});
+
+function snapPixel(value) {
+  return Math.round(value * deviceScale) / deviceScale;
+}
+
+function slugify(value = "") {
+  return String(value)
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, "-")
+    .replace(/^-|-$/g, "") || "unknown";
+}
+
+function executeScripts(root) {
+  for (const script of root.querySelectorAll("script")) {
+    const replacement = document.createElement("script");
+
+    for (const attribute of script.attributes) {
+      replacement.setAttribute(attribute.name, attribute.value);
+    }
+
+    replacement.textContent = script.textContent;
+    script.replaceWith(replacement);
+  }
+}
+
+function scheduleHydration(card, item) {
+  if (!hydrateDelay) {
+    hydrateCard(card, item);
+    return;
+  }
+
+  hydrationQueue.push({ card, item });
+
+  if (!hydrationTimer) {
+    hydrationTimer = setInterval(hydrateNextCard, hydrateDelay);
+  }
+}
+
+function hydrateNextCard() {
+  let next = hydrationQueue.shift();
+
+  while (next && !next.card.isConnected) {
+    next = hydrationQueue.shift();
+  }
+
+  if (!next) {
+    clearInterval(hydrationTimer);
+    hydrationTimer = undefined;
+    return;
+  }
+
+  hydrateCard(next.card, next.item);
+}
+
+function nudgeProviderWidgets(root) {
+  window.twttr?.widgets?.load?.(root);
+  window.instgrm?.Embeds?.process?.();
+  window.bluesky?.scan?.(root);
+}
+
+function hydrateCard(card, item) {
+  if (item.type === "photo" && item.url) {
+    const image = document.createElement("img");
+    image.src = item.url;
+    image.alt = item.title || "";
+    card.replaceChildren(image);
+  } else {
+    card.innerHTML = item.html || "";
+  }
+
+  executeScripts(card);
+  nudgeProviderWidgets(card);
+  card.classList.add("is-hydrated");
+}
+
+function createCard(column, item) {
+  const card = document.createElement("section");
+  card.className = `embed collage-card provider-${slugify(item.providerName)}`;
+  card.dataset.source = item.targetUrl;
+  card.dataset.height = String(placeholderHeight);
+  card.style.setProperty("--embed-width", `${config.cardWidth}px`);
+  cardColumns.set(card, column);
+  column.contentHeight += cardExtent(card);
+  cardObserver.observe(card);
+  scheduleHydration(card, item);
+  return card;
+}
+
+function createColumn(index) {
+  const element = document.createElement("div");
+  element.className = "collage-column";
+  element.dataset.column = String(index);
+  track.append(element);
+
+  return {
+    element,
+    index,
+    offset: 0,
+    contentHeight: 0,
+  };
+}
+
+function cardExtent(card) {
+  return cardHeight(card) + config.spacing;
+}
+
+function cardHeight(card) {
+  return Math.max(Number(card.dataset.height) || 0, placeholderHeight);
+}
+
+function candidateY(column) {
+  return column.contentHeight - column.offset;
+}
+
+function isTooCloseToSamePost(item, column) {
+  if (!config.repeatDistance || config.items.length < 2) {
+    return false;
+  }
+
+  const minDistanceSquared = config.repeatDistance * config.repeatDistance;
+  const nextY = candidateY(column);
+
+  for (const otherColumn of columns) {
+    const columnDistance = Math.abs(column.index - otherColumn.index) * (config.cardWidth + config.spacing);
+
+    for (const card of otherColumn.element.children) {
+      if (card.dataset.source !== item.targetUrl) {
+        continue;
+      }
+
+      const existingY = card.offsetTop - otherColumn.offset;
+      const yDistance = nextY - existingY;
+      const distanceSquared = (columnDistance * columnDistance) + (yDistance * yDistance);
+
+      if (distanceSquared < minDistanceSquared) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+function randomCandidate() {
+  return config.items[Math.floor(Math.random() * config.items.length)];
+}
+
+function sequentialCandidate(attempt) {
+  return config.items[(itemCursor + attempt) % config.items.length];
+}
+
+function nextItem(column) {
+  const maxAttempts = Math.max(config.items.length * 2, 8);
+  let fallback = config.items[0];
+
+  for (let attempt = 0; attempt < maxAttempts; attempt += 1) {
+    const item = config.shuffle ? randomCandidate() : sequentialCandidate(attempt);
+    fallback = item;
+
+    if (!isTooCloseToSamePost(item, column)) {
+      if (!config.shuffle) {
+        itemCursor += attempt + 1;
+      }
+
+      return item;
+    }
+  }
+
+  if (!config.shuffle) {
+    itemCursor += 1;
+  }
+
+  return fallback;
+}
+
+function fillColumn(column) {
+  const targetHeight = stage.clientHeight + Math.max(config.cardWidth, 720) + config.spacing;
+  let guard = 0;
+
+  while (column.contentHeight - column.offset < targetHeight && guard < 24) {
+    column.element.append(createCard(column, nextItem(column)));
+    guard += 1;
+  }
+}
+
+function fillColumns() {
+  for (const column of columns) {
+    fillColumn(column);
+  }
+}
+
+function recycleColumn(column) {
+  let firstCard = column.element.firstElementChild;
+
+  while (firstCard && isFullyAboveStage(firstCard, column)) {
+    column.contentHeight -= cardExtent(firstCard);
+    column.offset -= cardExtent(firstCard);
+    cardObserver.unobserve(firstCard);
+    cardColumns.delete(firstCard);
+    firstCard.remove();
+    column.element.append(createCard(column, nextItem(column)));
+    firstCard = column.element.firstElementChild;
+  }
+}
+
+function isFullyAboveStage(card, column) {
+  const cardBottom = trackTop + cardHeight(card) - column.offset;
+
+  return cardBottom <= 0;
+}
+
+function scrollSpeed() {
+  const baseDistance = Math.max(stage.clientHeight, config.cardWidth * config.repeat);
+  return baseDistance / config.duration;
+}
+
+function frame(now) {
+  const elapsedSeconds = Math.min((now - lastFrame) / 1000, 0.1);
+  lastFrame = now;
+
+  for (const column of columns) {
+    column.offset += scrollSpeed() * elapsedSeconds;
+    recycleColumn(column);
+    fillColumn(column);
+    column.element.style.transform = `translate3d(0, ${snapPixel(-column.offset)}px, 0)`;
+  }
+
+  requestAnimationFrame(frame);
+}
+
+for (let index = 0; index < config.columns; index += 1) {
+  columns.push(createColumn(index));
+}
+
+fillColumns();
+trackTop = track.offsetTop;
+
+for (const [index, column] of columns.entries()) {
+  const firstCard = column.element.firstElementChild;
+  const stagger = firstCard ? Math.min(index * config.spacing * 0.75, cardExtent(firstCard) * 0.4) : 0;
+  column.offset = stagger;
+  column.element.style.transform = `translate3d(0, ${snapPixel(-column.offset)}px, 0)`;
+}
+
+const observer = new ResizeObserver(() => {
+  trackTop = track.offsetTop;
+  fillColumns();
+});
+observer.observe(stage);
+
+requestAnimationFrame(frame);

public/styles.css

@@ -215,6 +215,8 @@ code {
   display: grid;
   justify-items: center;
   padding: var(--collage-spacing);
+  contain: layout paint;
+  pointer-events: none;
   -webkit-mask-image: linear-gradient(
     to bottom,
     transparent 0,
@@ -232,19 +234,23 @@ code {
 }
 
 .collage-track {
-  display: flex;
-  flex-direction: column;
-  width: max-content;
-  align-items: stretch;
-  gap: var(--collage-spacing);
-  animation: collage-scroll var(--collage-duration) linear infinite;
-  will-change: transform;
-}
-
-.collage-group {
   display: grid;
   grid-template-columns: repeat(var(--collage-columns), minmax(0, var(--collage-card-width)));
   gap: var(--collage-spacing);
+  width: max-content;
+  backface-visibility: hidden;
+  contain: layout style;
+}
+
+.collage-column {
+  display: flex;
+  flex-direction: column;
+  gap: var(--collage-spacing);
+  width: var(--collage-card-width);
+  backface-visibility: hidden;
+  contain: layout style;
+  transform: translate3d(0, 0, 0);
+  will-change: transform;
 }
 
 .collage-card {
@@ -252,10 +258,16 @@ code {
   width: 100%;
   height: auto;
   max-width: var(--collage-card-width);
-  overflow: hidden;
+  max-height: none;
+  contain: layout style;
+  overflow: visible;
   transform: none;
 }
 
+.collage-card:not(.is-hydrated) {
+  min-height: 160px;
+}
+
 .collage-card > iframe,
 .collage-card > blockquote,
 .collage-card > img,
@@ -274,16 +286,11 @@ code {
   width: 100% !important;
   max-width: 100% !important;
   box-sizing: border-box;
+  margin: 0 !important;
 }
 
-@keyframes collage-scroll {
-  from {
-    transform: translateY(0);
-  }
-
-  to {
-    transform: translateY(calc(-50% - (var(--collage-spacing) / 2)));
-  }
+.collage-card > * {
+  margin-block: 0 !important;
 }
 
 .error {

src/server.js

@@ -84,6 +84,7 @@ async function serveStatic(requestUrl, response) {
   const staticPaths = new Map([
     ["/styles.css", "styles.css"],
     ["/caspar.js", "caspar.js"],
+    ["/collage.js", "collage.js"],
   ]);
   const path = staticPaths.get(requestUrl.pathname) || "";
 
@@ -153,8 +154,10 @@ async function handleCollage(requestUrl, response) {
   const spacing = getNumber(requestUrl.searchParams, "spacing", Number(legacySpacing || 48), 0, 400);
   const fade = getNumber(requestUrl.searchParams, "fade", 0, 0, 600);
   const columns = getNumber(requestUrl.searchParams, "columns", 3, 1, 8);
+  const repeatDistance = getNumber(requestUrl.searchParams, "repeatDistance", 900, 0, 4000);
+  const hydrateDelay = getNumber(requestUrl.searchParams, "hydrateDelay", 180, 0, 2000);
   const duration = getNumber(requestUrl.searchParams, "duration", 360, 10, 1200);
-  const repeat = getNumber(requestUrl.searchParams, "repeat", 4, 2, 12);
+  const repeat = getNumber(requestUrl.searchParams, "repeat", 2, 1, 8);
   const shuffle = getBoolean(requestUrl.searchParams, "shuffle", true);
   const transparent = getBoolean(requestUrl.searchParams, "transparent", true);
   const autoplay = getBoolean(requestUrl.searchParams, "autoplay", true);
@@ -189,6 +192,8 @@ async function handleCollage(requestUrl, response) {
     spacing,
     fade,
     columns,
+    repeatDistance,
+    hydrateDelay,
     duration,
     repeat,
     shuffle,

src/templates.js

@@ -45,7 +45,7 @@ function collageCardWidth({ width, spacing, columns }) {
   const availableWidth = width - (spacing * 2) - (spacing * Math.max(columns - 1, 0));
   const columnWidth = Math.floor(availableWidth / columns);
 
-  return Math.max(Math.min(columnWidth, 500), 120);
+  return Math.max(columnWidth, 120);
 }
 
 function shuffleItems(items) {
@@ -59,6 +59,10 @@ function shuffleItems(items) {
   return shuffled;
 }
 
+function safeJson(value) {
+  return JSON.stringify(value).replaceAll("</", "<\\/");
+}
+
 function addIframePermissions(tag) {
   const autoplayPermission = "autoplay";
 
@@ -350,8 +354,10 @@ export function homePage({ providersCount = 0 } = {}) {
           <label>Spacing <input name="spacing" type="number" value="48" min="0" max="400"></label>
           <label>Fade <input name="fade" type="number" value="0" min="0" max="600"></label>
           <label>Columns <input name="columns" type="number" value="3" min="1" max="8"></label>
+          <label>Separation <input name="repeatDistance" type="number" value="900" min="0" max="4000"></label>
+          <label>Hydrate <input name="hydrateDelay" type="number" value="180" min="0" max="2000"></label>
           <label>Duration <input name="duration" type="number" value="360" min="10" max="1200"></label>
-          <label>Repeat <input name="repeat" type="number" value="4" min="2" max="12"></label>
+          <label>Repeat <input name="repeat" type="number" value="2" min="1" max="8"></label>
           <label class="checkbox-label"><input name="shuffle" value="1" type="checkbox" checked> shuffle</label>
           <label class="checkbox-label"><input name="transparent" value="1" type="checkbox" checked> transparent</label>
         </div>
@@ -435,35 +441,43 @@ export function collagePage({
   spacing = 48,
   fade = 0,
   columns = 3,
+  repeatDistance = 900,
+  hydrateDelay = 180,
   duration = 360,
-  repeat = 4,
+  repeat = 2,
   shuffle = true,
 }) {
   const cardWidth = collageCardWidth({ width, spacing, columns });
-  const orderedItems = shuffle ? shuffleItems(items) : items;
-  const groupItems = Array.from({ length: repeat }, () => orderedItems).flat();
-  const groupCards = groupItems
-    .map((item) => embedCardHtml({
+  const orderedItems = shuffle ? shuffleItems(items) : [...items];
+  const collageItems = orderedItems.map((item) => ({
     targetUrl: item.targetUrl,
-      embed: item.embed,
+    providerName: item.embed.provider_name || "",
+    type: item.embed.type || "rich",
+    title: item.embed.title || item.embed.provider_name || "",
+    url: item.embed.url || "",
+    html: prepareEmbedHtml(item.embed.html || "", { autoplay, muted }),
+  }));
+  const collageData = {
+    items: collageItems,
+    cardWidth,
+    columns,
+    repeatDistance,
+    hydrateDelay,
+    spacing,
+    duration,
+    repeat,
+    shuffle,
     autoplay,
     muted,
-      className: "embed collage-card",
-      widthCap: cardWidth,
-      includeHeight: false,
-    }))
-    .join("\n");
-  const groups = [groupCards, groupCards]
-    .map((cards) => `<div class="collage-group">${cards}</div>`)
-    .join("\n");
+  };
 
   return `${commonHead({ title: "oEmbed Collage", htmlClass: transparent ? "graphic-document transparent" : "graphic-document" })}
 <body class="graphic collage-page ${transparent ? "transparent" : ""} is-ready" style="--stage-width:${width}px; --stage-height:${height}px; --chroma:${escapeHtml(chroma)}; --collage-spacing:${spacing}px; --collage-fade:${fade}px; --collage-columns:${columns}; --collage-card-width:${cardWidth}px; --collage-duration:${duration}s;">
   <main class="collage-stage">
-    <div class="collage-track">
-      ${groups}
-    </div>
+    <div class="collage-track"></div>
   </main>
+  <script id="collage-data" type="application/json">${safeJson(collageData)}</script>
+  <script src="/collage.js"></script>
 </body>
 </html>`;
 }

test/templates.test.js

@@ -22,6 +22,9 @@ test("home page includes single graphic and collage forms", () => {
   assert.match(page, /name="spacing" type="number" value="48"/);
   assert.match(page, /name="fade" type="number" value="0"/);
   assert.match(page, /name="columns" type="number" value="3"/);
+  assert.match(page, /name="repeatDistance" type="number" value="900"/);
+  assert.match(page, /name="hydrateDelay" type="number" value="180"/);
+  assert.match(page, /name="repeat" type="number" value="2"/);
   assert.match(page, /name="shuffle" value="1" type="checkbox" checked/);
   assert.match(page, /Open collage/);
 });
@@ -238,6 +241,7 @@ test("renders a vertical scrolling collage page with repeated embed cards", () =
     spacing: 48,
     fade: 0,
     columns: 3,
+    repeatDistance: 900,
     duration: 360,
     repeat: 3,
     shuffle: false,
@@ -247,12 +251,17 @@ test("renders a vertical scrolling collage page with repeated embed cards", () =
   assert.match(page, /--collage-spacing:48px/);
   assert.match(page, /--collage-fade:0px/);
   assert.match(page, /--collage-columns:3/);
-  assert.match(page, /--collage-card-width:500px/);
+  assert.match(page, /--collage-card-width:576px/);
   assert.match(page, /--collage-duration:360s/);
-  assert.equal((page.match(/class="embed collage-card provider-example"/g) || []).length, 12);
-  assert.equal((page.match(/class="collage-group"/g) || []).length, 2);
-  assert.match(page, /--embed-width:500px/);
-  assert.doesNotMatch(page, /collage-card provider-example"[^>]*--embed-height/);
+  assert.match(page, /<div class="collage-track"><\/div>/);
+  assert.match(page, /<script id="collage-data" type="application\/json">/);
+  assert.match(page, /"cardWidth":576/);
+  assert.match(page, /"columns":3/);
+  assert.match(page, /"repeatDistance":900/);
+  assert.match(page, /"hydrateDelay":180/);
+  assert.match(page, /"repeat":3/);
+  assert.match(page, /"shuffle":false/);
+  assert.match(page, /<script src="\/collage\.js"><\/script>/);
 });
 
 test("shrinks collage card width to fit the configured screen width", () => {
@@ -281,6 +290,5 @@ test("shrinks collage card width to fit the configured screen width", () => {
   });
 
   assert.match(page, /--collage-card-width:260px/);
-  assert.match(page, /--embed-width:260px/);
-  assert.doesNotMatch(page, /collage-card provider-example"[^>]*--embed-height/);
+  assert.match(page, /"cardWidth":260/);
 });