diff --git a/surfaces/shell/src/display/DisplayApp.tsx b/surfaces/shell/src/display/DisplayApp.tsx
index dc385d6..bcf8f00 100644
--- a/surfaces/shell/src/display/DisplayApp.tsx
+++ b/surfaces/shell/src/display/DisplayApp.tsx
@@ -42,6 +42,11 @@ export interface DisplayAppProps {
/** The shortest interval between two revalidations prompted by refused module requests. Test seam
* only. */
readonly revalidationIntervalMs?: number;
+ /** How often a running display re-resolves its descriptor on its own. Test seam only. */
+ readonly periodicRevalidationMs?: number;
+ /** The first automatic retry delay after a failed start; doubles to a one-minute ceiling. Test seam
+ * only. */
+ readonly retryBaseMs?: number;
}
/** A Wi-Fi reassociation or a switch reboot lasts seconds and needs no comment on a lobby wall. Only
@@ -52,6 +57,16 @@ export const DISPLAY_OFFLINE_INDICATOR_DELAY_MS = 10_000;
* display that is merely missing one permission must not turn every refused request into two more. */
export const DISPLAY_REVALIDATION_INTERVAL_MS = 15_000;
+/** A running display asks again this often, so a module upgraded on the server is picked up and a
+ * revocation is noticed even by a module that makes no requests of its own. */
+export const DISPLAY_PERIODIC_REVALIDATION_MS = 5 * 60_000;
+
+/** A display that could not start tries again on its own: from this delay, doubling to a minute. A
+ * kiosk that boots before its server — after a power cut, say — must come up without anyone pressing
+ * Retry. */
+export const DISPLAY_RETRY_BASE_MS = 2_000;
+export const DISPLAY_RETRY_MAX_MS = 60_000;
+
/** Whether a fresh resolution describes exactly the display already mounted. Compared structurally:
* the descriptor and principal are small, server-produced, and carry nothing volatile, so any
* difference — a new version, a new contribution, a different principal — is a real one. */
@@ -192,8 +207,12 @@ export function DisplayApp(props: DisplayAppProps): ReactElement {
importModule,
moduleId,
offlineIndicatorDelayMs = DISPLAY_OFFLINE_INDICATOR_DELAY_MS,
+ periodicRevalidationMs = DISPLAY_PERIODIC_REVALIDATION_MS,
+ retryBaseMs = DISPLAY_RETRY_BASE_MS,
revalidationIntervalMs = DISPLAY_REVALIDATION_INTERVAL_MS,
} = props;
+ /** Consecutive automatic retries since the display last started successfully. */
+ const failures = useRef(0);
const stateRef = useRef(state);
stateRef.current = state;
const revalidation = useRef<{ inFlight: AbortController | undefined; lastAt: number }>({
@@ -211,7 +230,7 @@ export function DisplayApp(props: DisplayAppProps): ReactElement {
* stays. A display that is not showing anything simply starts over.
*/
const revalidate = useCallback(
- (reason: "online" | "authorization"): void => {
+ (reason: "online" | "authorization" | "periodic"): void => {
const current = stateRef.current;
if (current.status !== "ready") {
if (reason === "online") {
@@ -264,6 +283,31 @@ export function DisplayApp(props: DisplayAppProps): ReactElement {
const onAuthorizationResponse = useCallback(() => revalidate("authorization"), [revalidate]);
+ // While running: ask again now and then, without disturbing anything when the answer is the same.
+ useEffect(() => {
+ if (state.status !== "ready" || periodicRevalidationMs <= 0) {
+ return;
+ }
+ const timer = setInterval(() => revalidate("periodic"), periodicRevalidationMs);
+ return () => clearInterval(timer);
+ }, [periodicRevalidationMs, revalidate, state.status]);
+
+ // Could not start: try again on its own, backing off. Pairing is not a failure — it has its own
+ // polling — and a ready display has nothing to retry.
+ useEffect(() => {
+ if (state.status === "ready") {
+ failures.current = 0;
+ return;
+ }
+ if (state.status !== "failed" && state.status !== "unavailable") {
+ return;
+ }
+ const delay = Math.min(DISPLAY_RETRY_MAX_MS, retryBaseMs * 2 ** Math.min(failures.current, 10));
+ failures.current += 1;
+ const timer = setTimeout(() => setAttempt((value) => value + 1), delay);
+ return () => clearTimeout(timer);
+ }, [retryBaseMs, state.status]);
+
useEffect(() => {
if (!connectivitySource) {
return;
diff --git a/surfaces/shell/tests/display-app.test.tsx b/surfaces/shell/tests/display-app.test.tsx
index 9899d4b..f5e956d 100644
--- a/surfaces/shell/tests/display-app.test.tsx
+++ b/surfaces/shell/tests/display-app.test.tsx
@@ -1161,4 +1161,69 @@ describe("display host — continuity across reconnects and revocation", () => {
});
expect(query("display-offline")?.textContent).toBe("Offline — reconnecting");
});
+
+ it("starts on its own when the server comes up after the screen did", async () => {
+ // A kiosk that boots before its server: the network is up, so no `online` event will ever come.
+ let up = false;
+ const fetch = vi.fn(async (input: RequestInfo | URL) => {
+ const url = String(input);
+ if (url.endsWith("/api/v1/module-displays/announcements")) {
+ return up ? json(descriptorPayload()) : json({ code: "UNAVAILABLE" }, 503);
+ }
+ return json({ code: "NOT_FOUND" }, 404);
+ }) as unknown as typeof globalThis.fetch;
+ const display = countingArtifact();
+ await act(async () => {
+ root.render(
+ ,
+ );
+ });
+ await flush();
+ expect(query("display-host-error")).not.toBeNull();
+
+ up = true;
+ await act(async () => {
+ await new Promise((resolve) => setTimeout(resolve, 200));
+ });
+ await flush();
+ expect(display.counts.mounts).toBe(1);
+ expect(query("display-host-error")).toBeNull();
+ });
+
+ it("re-resolves a running display periodically, remounting only for a new version", async () => {
+ const server = changingServer();
+ const display = countingArtifact();
+ await act(async () => {
+ root.render(
+ ,
+ );
+ });
+ await flush();
+ const before = server.descriptorCalls();
+ await act(async () => {
+ await new Promise((resolve) => setTimeout(resolve, 150));
+ });
+ await flush();
+ expect(server.descriptorCalls()).toBeGreaterThan(before);
+ expect(display.counts).toEqual({ mounts: 1, unmounts: 0 });
+
+ server.set(200, descriptorPayload("announcements", "2.0.0"));
+ await act(async () => {
+ await new Promise((resolve) => setTimeout(resolve, 150));
+ });
+ await flush();
+ expect(display.counts.mounts).toBe(2);
+ });
});