Specify /preview_url requests as low priority

src/@types/global.d.ts

@@ -96,4 +96,20 @@ declare global {
         // but we still need this for MatrixCall::getRidOfRTXCodecs()
         setCodecPreferences(codecs: RTCRtpCodecCapability[]): void;
     }
+
+    interface RequestInit {
+        /**
+         * Specifies the priority of the fetch request relative to other requests of the same type.
+         * Must be one of the following strings:
+         *   high: A high priority fetch request relative to other requests of the same type.
+         *   low: A low priority fetch request relative to other requests of the same type.
+         *   auto: Automatically determine the priority of the fetch request relative to other requests of the same type (default).
+         *
+         * @see https://html.spec.whatwg.org/multipage/urls-and-fetching.html#fetch-priority-attribute
+         * @see https://github.com/microsoft/TypeScript/issues/54472
+         * @see https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API#browser_compatibility
+         * Not yet supported in Safari or Firefox
+         */
+        priority?: "high" | "low" | "auto";
+    }
 }

src/client.ts

@@ -5128,6 +5128,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             undefined,
             {
                 prefix: MediaPrefix.R0,
+                priority: "low",
             },
         );
         // TODO: Expire the URL preview cache sometimes

src/http-api/fetch.ts

@@ -222,7 +222,7 @@ export class FetchHttpApi<O extends IHttpOpts> {
         method: Method,
         url: URL | string,
         body?: Body,
-        opts: Pick<IRequestOpts, "headers" | "json" | "localTimeoutMs" | "keepAlive" | "abortSignal"> = {},
+        opts: Pick<IRequestOpts, "headers" | "json" | "localTimeoutMs" | "keepAlive" | "abortSignal" | "priority"> = {},
     ): Promise<ResponseType<T, O>> {
         const urlForLogs = this.sanitizeUrlForLogs(url);
         logger.debug(`FetchHttpApi: --> ${method} ${urlForLogs}`);
@@ -276,6 +276,7 @@ export class FetchHttpApi<O extends IHttpOpts> {
                 cache: "no-cache",
                 credentials: "omit", // we send credentials via headers
                 keepalive: keepAlive,
+                priority: opts.priority,
             });
 
             logger.debug(`FetchHttpApi: <-- ${method} ${urlForLogs} [${Date.now() - start}ms ${res.status}]`);

src/http-api/interface.ts

@@ -33,7 +33,7 @@ export interface IHttpOpts {
     localTimeoutMs?: number;
 }
 
-export interface IRequestOpts {
+export interface IRequestOpts extends Pick<RequestInit, "priority"> {
     /**
      * The alternative base url to use.
      * If not specified, uses this.opts.baseUrl