1 files changed, 99 insertions, 0 deletions
diff --git a/apps/web/src/components/editor/timeline/timeline-scroll-sync.tsx b/apps/web/src/components/editor/timeline/timeline-scroll-sync.tsx
new file mode 100644
index 00000000..2318f977
--- /dev/null
+++ b/apps/web/src/components/editor/timeline/timeline-scroll-sync.tsx
@@ -0,0 +1,99 @@
+import { useEffect, useRef } from "react";
+
+export interface TimelineScrollSyncProps {
+  rulerScrollRef: React.RefObject<HTMLDivElement>;
+  tracksScrollRef: React.RefObject<HTMLDivElement>;
+  trackLabelsScrollRef: React.RefObject<HTMLDivElement>;
+}
+
+export function useTimelineScrollSync({
+  rulerScrollRef,
+  tracksScrollRef,
+  trackLabelsScrollRef,
+}: TimelineScrollSyncProps) {
+  const isUpdatingRef = useRef(false);
+  const lastRulerSync = useRef(0);
+  const lastTracksSync = useRef(0);
+  const lastVerticalSync = useRef(0);
+
+  // --- Scroll synchronization effect ---
+  useEffect(() => {
+    const rulerViewport = rulerScrollRef.current?.querySelector(
+      "[data-radix-scroll-area-viewport]"
+    ) as HTMLElement;
+    const tracksViewport = tracksScrollRef.current?.querySelector(
+      "[data-radix-scroll-area-viewport]"
+    ) as HTMLElement;
+    const trackLabelsViewport = trackLabelsScrollRef.current?.querySelector(
+      "[data-radix-scroll-area-viewport]"
+    ) as HTMLElement;
+
+    if (!rulerViewport || !tracksViewport) return;
+
+    // Horizontal scroll synchronization between ruler and tracks
+    const handleRulerScroll = () => {
+      const now = Date.now();
+      if (isUpdatingRef.current || now - lastRulerSync.current < 16) return;
+      lastRulerSync.current = now;
+      isUpdatingRef.current = true;
+      tracksViewport.scrollLeft = rulerViewport.scrollLeft;
+      isUpdatingRef.current = false;
+    };
+    const handleTracksScroll = () => {
+      const now = Date.now();
+      if (isUpdatingRef.current || now - lastTracksSync.current < 16) return;
+      lastTracksSync.current = now;
+      isUpdatingRef.current = true;
+      rulerViewport.scrollLeft = tracksViewport.scrollLeft;
+      isUpdatingRef.current = false;
+    };
+
+    rulerViewport.addEventListener("scroll", handleRulerScroll);
+    tracksViewport.addEventListener("scroll", handleTracksScroll);
+
+    // Vertical scroll synchronization between track labels and tracks content
+    if (trackLabelsViewport) {
+      const handleTrackLabelsScroll = () => {
+        const now = Date.now();
+        if (isUpdatingRef.current || now - lastVerticalSync.current < 16)
+          return;
+        lastVerticalSync.current = now;
+        isUpdatingRef.current = true;
+        tracksViewport.scrollTop = trackLabelsViewport.scrollTop;
+        isUpdatingRef.current = false;
+      };
+      const handleTracksVerticalScroll = () => {
+        const now = Date.now();
+        if (isUpdatingRef.current || now - lastVerticalSync.current < 16)
+          return;
+        lastVerticalSync.current = now;
+        isUpdatingRef.current = true;
+        trackLabelsViewport.scrollTop = tracksViewport.scrollTop;
+        isUpdatingRef.current = false;
+      };
+
+      trackLabelsViewport.addEventListener("scroll", handleTrackLabelsScroll);
+      tracksViewport.addEventListener("scroll", handleTracksVerticalScroll);
+
+      return () => {
+        rulerViewport.removeEventListener("scroll", handleRulerScroll);
+        tracksViewport.removeEventListener("scroll", handleTracksScroll);
+        trackLabelsViewport.removeEventListener(
+          "scroll",
+          handleTrackLabelsScroll
+        );
+        tracksViewport.removeEventListener(
+          "scroll",
+          handleTracksVerticalScroll
+        );
+      };
+    }
+
+    return () => {
+      rulerViewport.removeEventListener("scroll", handleRulerScroll);
+      tracksViewport.removeEventListener("scroll", handleTracksScroll);
+    };
+  }, []);
+
+  return null;
+}