fix: ensure iframe visibility tracking is triggered on load

src/courseware/course/sequence/Unit/hooks/useIFrameBehavior.test.js

@@ -280,23 +280,17 @@ describe('useIFrameBehavior hook', () => {
       });
     });
     describe('visibility tracking', () => {
-      it('sets up visibility tracking after iframe has loaded', () => {
+      it('sets up visibility tracking after iframe loads', () => {
         mockState({ ...defaultStateVals, hasLoaded: true });
 
         renderHook(() => useIFrameBehavior(props));
 
         expect(global.window.addEventListener).toHaveBeenCalledTimes(2);
         expect(global.window.addEventListener).toHaveBeenCalledWith('scroll', expect.any(Function));
         expect(global.window.addEventListener).toHaveBeenCalledWith('resize', expect.any(Function));
-        // Initial visibility update.
-        expect(postMessage).toHaveBeenCalledWith(
-          {
-            type: 'unit.visibilityStatus',
-            data: {
-              topPosition: 100,
-              viewportHeight: 800,
-            },
-          },
+        // Initial visibility update is handled by the `handleIFrameLoad` method.
+        expect(postMessage).not.toHaveBeenCalledWith(
+          expect.objectContaining({ type: 'unit.visibilityStatus' }),
           config.LMS_BASE_URL,
         );
       });
@@ -362,6 +356,20 @@ describe('useIFrameBehavior hook', () => {
         window.onmessage(event);
         expect(dispatch).toHaveBeenCalledWith(processEvent(event.data, fetchCourse));
       });
+      it('updates initial iframe visibility on load', () => {
+        const { result } = renderHook(() => useIFrameBehavior(props));
+        result.current.handleIFrameLoad();
+        expect(postMessage).toHaveBeenCalledWith(
+          {
+            type: 'unit.visibilityStatus',
+            data: {
+              topPosition: 100,
+              viewportHeight: 800,
+            },
+          },
+          config.LMS_BASE_URL,
+        );
+      });
     });
     it('forwards handleIframeLoad, showError, and hasLoaded from state fields', () => {
       mockState(stateVals);

src/courseware/course/sequence/Unit/hooks/useIFrameBehavior.ts

@@ -102,6 +102,23 @@ const useIFrameBehavior = ({
   useEventListener('message', receiveMessage);
 
   // Send visibility status to the iframe. It's used to mark XBlocks as viewed.
+  const updateIframeVisibility = () => {
+    const iframeElement = document.getElementById(elementId) as HTMLIFrameElement | null;
+    const rect = iframeElement?.getBoundingClientRect();
+    const visibleInfo = {
+      type: 'unit.visibilityStatus',
+      data: {
+        topPosition: rect?.top,
+        viewportHeight: window.innerHeight,
+      },
+    };
+    iframeElement?.contentWindow?.postMessage(
+      visibleInfo,
+      `${getConfig().LMS_BASE_URL}`,
+    );
+  };
+
+  // Set up visibility tracking event listeners.
   React.useEffect(() => {
     if (!hasLoaded) {
       return undefined;
@@ -112,27 +129,9 @@ const useIFrameBehavior = ({
       return undefined;
     }
 
-    const updateIframeVisibility = () => {
-      const rect = iframeElement.getBoundingClientRect();
-      const visibleInfo = {
-        type: 'unit.visibilityStatus',
-        data: {
-          topPosition: rect.top,
-          viewportHeight: window.innerHeight,
-        },
-      };
-      iframeElement?.contentWindow?.postMessage(
-        visibleInfo,
-        `${getConfig().LMS_BASE_URL}`,
-      );
-    };
-
     // Throttle the update function to prevent it from sending too many messages to the iframe.
     const throttledUpdateVisibility = throttle(updateIframeVisibility, 100);
 
-    // Update the visibility of the iframe in case the element is already visible.
-    updateIframeVisibility();
-
     // Add event listeners to update the visibility of the iframe when the window is scrolled or resized.
     window.addEventListener('scroll', throttledUpdateVisibility);
     window.addEventListener('resize', throttledUpdateVisibility);
@@ -167,6 +166,9 @@ const useIFrameBehavior = ({
         dispatch(processEvent(e.data, fetchCourse));
       }
     };
+
+    // Update the visibility of the iframe in case the element is already visible.
+    updateIframeVisibility();
   };
 
   React.useEffect(() => {