Improve timeline scroll, media layout, avatars, and emoji coverage.

Remember room scroll position across switches, reserve image/video heights from Matrix dimensions, cache authenticated media blobs for avatars, restore jumbo emoji-only messages, and extend emoji font unicode-range for Unicode 15 glyphs.

src/app/utils/authenticatedMediaCache.ts

@@ -0,0 +1,87 @@
+import { getCurrentAccessToken } from './auth';
+
+const MAX_ENTRIES = 250;
+
+/** Shared blob URLs for authenticated Matrix media (avatars, thumbs, etc.). */
+const blobCache = new Map<string, string>();
+const inflight = new Map<string, Promise<string>>();
+
+export const isAuthenticatedMediaUrl = (url: string): boolean =>
+  url.includes('/_matrix/client/v1/media/download') ||
+  url.includes('/_matrix/client/v1/media/thumbnail') ||
+  (url.includes('/_matrix/media/') &&
+    (url.includes('/download/') || url.includes('/thumbnail/')));
+
+export const getCachedAuthenticatedMediaUrl = (src: string | undefined): string | undefined => {
+  if (!src) return undefined;
+  return blobCache.get(src);
+};
+
+const touch = (src: string, blobUrl: string) => {
+  // Re-insert for LRU ordering (Map preserves insertion order).
+  if (blobCache.has(src)) blobCache.delete(src);
+  blobCache.set(src, blobUrl);
+
+  while (blobCache.size > MAX_ENTRIES) {
+    const oldest = blobCache.keys().next().value as string | undefined;
+    if (!oldest) break;
+    const oldUrl = blobCache.get(oldest);
+    blobCache.delete(oldest);
+    if (oldUrl) URL.revokeObjectURL(oldUrl);
+  }
+};
+
+const fetchBlobUrl = async (src: string): Promise<string> => {
+  const accessToken = getCurrentAccessToken();
+  let response = await fetch(src, {
+    method: 'GET',
+    headers: accessToken ? { Authorization: `Bearer ${accessToken}` } : undefined,
+  });
+
+  if (!response.ok && response.status === 401 && accessToken) {
+    response = await fetch(src, { method: 'GET' });
+  }
+
+  if (!response.ok) {
+    throw new Error(`Failed to fetch authenticated media: ${response.status}`);
+  }
+
+  const blob = await response.blob();
+  return URL.createObjectURL(blob);
+};
+
+/**
+ * Returns a stable blob: URL for authenticated media, reusing cache across mounts.
+ * Non-auth URLs are returned as-is.
+ */
+export const resolveAuthenticatedMediaUrl = async (
+  src: string,
+  useAuthentication: boolean
+): Promise<string> => {
+  if (!useAuthentication || !isAuthenticatedMediaUrl(src)) {
+    return src;
+  }
+
+  const cached = blobCache.get(src);
+  if (cached) {
+    touch(src, cached);
+    return cached;
+  }
+
+  let pending = inflight.get(src);
+  if (!pending) {
+    pending = fetchBlobUrl(src)
+      .then((blobUrl) => {
+        touch(src, blobUrl);
+        inflight.delete(src);
+        return blobUrl;
+      })
+      .catch((err) => {
+        inflight.delete(src);
+        throw err;
+      });
+    inflight.set(src, pending);
+  }
+
+  return pending;
+};