Fix timeline panel not populating on session restore

src/ui/qml/session/src/session_model_ui.cpp

@@ -627,6 +627,17 @@ void SessionModel::processChildren(const nlohmann::json &rj, const QModelIndex &
         emit dataChanged(parent_index, parent_index, roles);
     }
 
+    // After populating session/playlist children, re-trigger the viewport and
+    // current container lookup.  On session restore the initial lookup fires
+    // before the model tree is fully built (the children arrive asynchronously),
+    // so timelines inside playlists are not yet findable.  Re-checking here
+    // ensures the timeline panel picks up the active container once its node
+    // actually exists in the tree.
+    if (type == "Session" || type == "Container List" || type == "Playlist") {
+        updateCurrentMediaContainerIndexFromBackend();
+        updateViewportCurrentMediaContainerIndexFromBackend();
+    }
+
     emit jsonChanged();
 
     CHECK_SLOW_WATCHER_FAST()

ui/qml/xstudio/views/timeline/XsTimeline.qml

@@ -306,6 +306,30 @@ Rectangle {
                     initTimeline()
                     }}(), 50);
 
+        } else if (viewedMediaSetProperties.index.valid && viewedMediaSetProperties.values.typeRole == "Playlist") {
+            // When restoring a session, the viewed container may be a Playlist
+            // rather than a Timeline.  Find the first Timeline child inside the
+            // Playlist's Container List (row 2) and initialise from it.
+            let containerListIndex = theSessionData.index(2, 0, viewedMediaSetProperties.index)
+            let childCount = theSessionData.rowCount(containerListIndex)
+            for (let i = 0; i < childCount; i++) {
+                let childIndex = theSessionData.index(i, 0, containerListIndex)
+                if (theSessionData.get(childIndex, "typeRole") == "Timeline") {
+                    // Switch the viewed container to this Timeline so the
+                    // playhead and viewport are correctly attached.
+                    theSessionData.viewportCurrentMediaContainerIndex = childIndex
+                    return
+                }
+            }
+            // No timeline children found (or not yet loaded).  If the container
+            // list is empty the data may still be arriving asynchronously, so
+            // retry after a short delay.
+            if (childCount == 0 && !timeline_items.rootIndex.valid) {
+                callbackTimer.setTimeout(function() { return function() {
+                        viewedMediaSetChanged()
+                        }}(), 250);
+            }
+
         } else if (!timeline_items.rootIndex.valid) {
             // if the user has selected something that is not a timeline (playlist,
             // subset etc.), we do  not update our index here (unless the timeline