Fix tracker bar anchoring to action row and stop drift

extension/content.js

@@ -265,7 +265,7 @@ function dedupeTrackersForUrlInScope(encodedUrl, scopeRoot, preferredTracker = n
 
   const keep = preferredTracker && trackers.includes(preferredTracker)
     ? preferredTracker
-    : trackers[trackers.length - 1];
+    : trackers[0];
 
   trackers.forEach((tracker) => {
     if (tracker !== keep) {
@@ -276,6 +276,26 @@ function dedupeTrackersForUrlInScope(encodedUrl, scopeRoot, preferredTracker = n
   return keep;
 }
 
+function getTrackerHostElement(trackerElement) {
+  if (!trackerElement) {
+    return null;
+  }
+
+  const rawHost = trackerElement.closest('div[aria-posinset], article[role="article"], article, div[role="complementary"]');
+  return rawHost ? ensurePrimaryPostElement(rawHost) : null;
+}
+
+function isTrackerInsertionMarkerLocked(marker) {
+  return Boolean(marker && marker.dataset && marker.dataset.anchorLocked === '1');
+}
+
+function setTrackerInsertionMarkerLocked(marker, locked) {
+  if (!marker || !marker.dataset) {
+    return;
+  }
+  marker.dataset.anchorLocked = locked ? '1' : '0';
+}
+
 function getTrackerInsertionAnchorInPost(postElement, buttonBar) {
   if (!postElement || !buttonBar || !postElement.contains(buttonBar)) {
     return null;
@@ -412,6 +432,7 @@ function createTrackerInsertionMarker() {
   const marker = document.createElement('div');
   marker.className = 'fb-tracker-insertion-anchor';
   marker.setAttribute('aria-hidden', 'true');
+  setTrackerInsertionMarkerLocked(marker, false);
   marker.style.cssText = `
     display: block;
     width: 100%;
@@ -431,25 +452,28 @@ function positionTrackerInsertionMarker(postElement, marker, buttonBar, postNum
 
   const resolvedButtonBar = resolveActionButtonBar(postElement, buttonBar);
   const actionAnchor = getDirectActionAnchorInPost(postElement, resolvedButtonBar);
-  const sortAnchor = findAdjacentCommentSortAnchor(postElement, actionAnchor);
+  const preferredAnchor = actionAnchor;
-  const preferredAnchor = sortAnchor || actionAnchor;
 
   if (preferredAnchor && preferredAnchor.parentElement) {
     preferredAnchor.parentElement.insertBefore(marker, preferredAnchor.nextSibling);
+    setTrackerInsertionMarkerLocked(marker, true);
     return true;
   }
 
   if (resolvedButtonBar && resolvedButtonBar.parentElement && postElement.contains(resolvedButtonBar.parentElement)) {
     resolvedButtonBar.parentElement.insertBefore(marker, resolvedButtonBar.nextSibling);
+    setTrackerInsertionMarkerLocked(marker, true);
     return true;
   }
 
   if (buttonBar && buttonBar.parentElement && buttonBar.parentElement.parentElement && !postElement.contains(buttonBar.parentElement.parentElement)) {
     buttonBar.parentElement.parentElement.insertBefore(marker, buttonBar.parentElement.nextSibling);
+    setTrackerInsertionMarkerLocked(marker, false);
     return true;
   }
 
   postElement.appendChild(marker);
+  setTrackerInsertionMarkerLocked(marker, false);
   console.log('[FB Tracker] Post #' + postNum + ' - Marker fallback appended to post');
   return true;
 }
@@ -474,6 +498,11 @@ function ensureTrackerInsertionMarker(postElement, buttonBar, postNum = '?') {
     marker = createTrackerInsertionMarker();
   }
 
+  if (marker.isConnected && postElement.contains(marker) && isTrackerInsertionMarkerLocked(marker)) {
+    setTrackerAnchorForPost(postElement, marker);
+    return marker;
+  }
+
   const positioned = positionTrackerInsertionMarker(postElement, marker, buttonBar, postNum);
   if (!positioned || !marker.isConnected) {
     clearTrackerAnchorForPost(postElement, marker);
@@ -3388,6 +3417,12 @@ async function createTrackerUI(postElement, buttonBar, postNum = '?', options =
   if (existingScopedTrackers.length > 0) {
     const scopedTracker = dedupeTrackersForUrlInScope(encodedUrl, scopeRoot, existingScopedTrackers[0]);
     if (scopedTracker) {
+      const trackerHost = getTrackerHostElement(scopedTracker);
+      if (trackerHost && trackerHost !== postElement) {
+        console.log('[FB Tracker] Post #' + postNum + ' - Reusing tracker skipped (different host container)');
+        postElement.setAttribute(PROCESSED_ATTR, '1');
+        return;
+      }
       const marker = ensureTrackerInsertionMarker(postElement, buttonBar, postNum);
       if (marker) {
         insertTrackerAtMarker(marker, scopedTracker);