Add slide visibility message control to sequence animations

2026/mcp-connect/animations/shared/sequence-helpers.js

@@ -84,9 +84,13 @@ function runSequenceAnimation({
     schedule(() => runAnimation(activeRunId), restartDelay);
   }
 
-  function start() {
+  function stop() {
     runId++;
     clearTimers();
+  }
+
+  function start() {
+    stop();
     schedule(() => runAnimation(runId), initialDelay);
   }
 
@@ -102,4 +106,18 @@ function runSequenceAnimation({
       start();
     }
   });
+
+  // Parent-controlled visibility for embedded slide iframes.
+  window.addEventListener('message', (event) => {
+    const data = event.data;
+    if (!data || data.type !== 'marp-slide-visibility') {
+      return;
+    }
+
+    if (data.active) {
+      start();
+    } else {
+      stop();
+    }
+  });
 }