feat: surface viewer RTT in the PopcornHost embed SDK (requestRtt + rtt event)

Author: kryptocodes

images/minimal-vnc-desktop/host/popcorn-host.js

@@ -700,6 +700,7 @@
           case 'POPCORN_KBD_STATE': emit('kbdstate', d); break;
           case 'POPCORN_INPUT_DRIFT': emit('inputdrift', d); break;
           case 'POPCORN_INTERACTION': emit('interaction', d); break;
+          case 'POPCORN_RTT': emit('rtt', d); break;
           case 'POPCORN_KBD_HEALTH': emit('health', d); break;
           // Framebuffer vs CSS vs device-pixel geometry (viewer.js traceScale).
           // The one place a "the stream looks blurry" report becomes a number, and
@@ -846,7 +847,7 @@
     }
 
     return {
-      /** Subscribe to viewer events: hello|viewport|connect|frame|disconnect|error|kbdstate|inputdrift|interaction|health|scale|layout */
+      /** Subscribe to viewer events: hello|viewport|connect|frame|disconnect|error|kbdstate|inputdrift|interaction|health|scale|layout|rtt */
       on: function (name, fn) {
         (listeners[name] || (listeners[name] = [])).push(fn);
         return this;
@@ -862,6 +863,14 @@
       toggleMagnify: function () { post('POPCORN_TOGGLE_MAGNIFY', null); },
       /** Drive the viewer's keyboard toggle from your own button. */
       toggleKeyboard: function () { post('POPCORN_TOGGLE_KBD', null); },
+      /**
+       * Ask for the viewer's measured tunnel round trip; the answer arrives as
+       * .on('rtt', ({rttMs, avgMs, samples}) => ...). rttMs is the latest
+       * viewer<->pod sample (null before the first pong), avgMs the smoothed
+       * link latency. A postMessage ping from this page could only time the
+       * in-device hop, so the viewer's own measurement is the one that matters.
+       */
+      requestRtt: function () { post('POPCORN_RTT_REQUEST', null); },
       /**
        * Paste text into the focused remote field. Read the clipboard HERE, in the
        * gesture handler of your own button: clipboard permission in a nested

images/minimal-vnc-desktop/kbd/test/host-rtt.test.mjs

@@ -10,6 +10,7 @@ import {
   installGlobals, freshViewer, fireHostMessage, parentMessages, advanceClock,
 } from './stub-dom.mjs';
 import { createMockRfb } from './mock-rfb.mjs';
+import { makeHostWindow } from './host-stub.mjs';
 
 installGlobals('ios', { embedded: true, search: '?parentOrigin=https://portal.test' });
 
@@ -52,3 +53,21 @@ test('the RTT read obeys the fail-closed inbound gate (wrong origin ignored)', a
   fireHostMessage({ type: 'POPCORN_RTT_REQUEST' }, { origin: 'https://evil.example' });
   assert.equal(lastRttMsg(), null, 'request from a non-configured origin is dropped');
 });
+
+// ---- host side (PopcornHost SDK) ----------------------------------------
+
+test('PopcornHost.requestRtt posts the request and surfaces the reply as .on(\'rtt\')', async () => {
+  const h = makeHostWindow({ top: true, iframeStyle: { position: 'fixed' },
+    iframeRect: { left: 0, top: 0, width: 411, height: 732 } });
+  const host = h.PopcornHost.attach(h.iframe, { childOrigin: 'https://pod.test' });
+
+  const got = [];
+  host.on('rtt', (d) => got.push(d));
+  host.requestRtt();
+  assert.ok(h.posted.some((m) => m.type === 'POPCORN_RTT_REQUEST'), 'request posted to the frame');
+
+  h.fromChild({ type: 'POPCORN_RTT', rttMs: 86, avgMs: 92, samples: 41 });
+  assert.equal(got.length, 1, 'rtt event emitted');
+  assert.equal(got[0].rttMs, 86);
+  assert.equal(got[0].samples, 41);
+});