From fca99d6126c31fbb18ed9f1034cee6f940b040e8 Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Tue, 10 Feb 2026 16:28:21 +0100
Subject: refactor

---
 .../editor/panels/timeline/timeline-ruler.tsx      | 126 +++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 apps/web/src/components/editor/panels/timeline/timeline-ruler.tsx

(limited to 'apps/web/src/components/editor/panels/timeline/timeline-ruler.tsx')

diff --git a/apps/web/src/components/editor/panels/timeline/timeline-ruler.tsx b/apps/web/src/components/editor/panels/timeline/timeline-ruler.tsx
new file mode 100644
index 00000000..b0261aa2
--- /dev/null
+++ b/apps/web/src/components/editor/panels/timeline/timeline-ruler.tsx
@@ -0,0 +1,126 @@
+import { type JSX, useLayoutEffect, useRef } from "react";
+import { TIMELINE_CONSTANTS } from "@/constants/timeline-constants";
+import { DEFAULT_FPS } from "@/constants/project-constants";
+import { useEditor } from "@/hooks/use-editor";
+import { getRulerConfig, shouldShowLabel } from "@/lib/timeline/ruler-utils";
+import { useScrollPosition } from "@/hooks/timeline/use-scroll-position";
+import { TimelineTick } from "./timeline-tick";
+
+interface TimelineRulerProps {
+	zoomLevel: number;
+	dynamicTimelineWidth: number;
+	rulerRef: React.Ref<HTMLDivElement>;
+	tracksScrollRef: React.RefObject<HTMLElement | null>;
+	handleWheel: (e: React.WheelEvent) => void;
+	handleTimelineContentClick: (e: React.MouseEvent) => void;
+	handleRulerTrackingMouseDown: (e: React.MouseEvent) => void;
+	handleRulerMouseDown: (e: React.MouseEvent) => void;
+}
+
+export function TimelineRuler({
+	zoomLevel,
+	dynamicTimelineWidth,
+	rulerRef,
+	tracksScrollRef,
+	handleWheel,
+	handleTimelineContentClick,
+	handleRulerTrackingMouseDown,
+	handleRulerMouseDown,
+}: TimelineRulerProps) {
+	const editor = useEditor();
+	const duration = editor.timeline.getTotalDuration();
+	const pixelsPerSecond = TIMELINE_CONSTANTS.PIXELS_PER_SECOND * zoomLevel;
+	const visibleDuration = dynamicTimelineWidth / pixelsPerSecond;
+	const effectiveDuration = Math.max(duration, visibleDuration);
+	const project = editor.project.getActive();
+	const fps = project?.settings.fps ?? DEFAULT_FPS;
+	const { labelIntervalSeconds, tickIntervalSeconds } = getRulerConfig({
+		zoomLevel,
+		fps,
+	});
+	const tickCount = Math.ceil(effectiveDuration / tickIntervalSeconds) + 1;
+
+	const { scrollLeft, viewportWidth } = useScrollPosition({
+		scrollRef: tracksScrollRef,
+	});
+
+	/**
+	 * widens the virtualization buffer during zoom transitions.
+	 * useScrollPosition lags one frame behind the scroll adjustment
+	 * that useLayoutEffect applies after a zoom change.
+	 */
+	const prevZoomRef = useRef(zoomLevel);
+	const isZoomTransition = zoomLevel !== prevZoomRef.current;
+	const bufferPx = isZoomTransition
+		? Math.max(200, (scrollLeft + viewportWidth) * 0.15)
+		: 200;
+
+	useLayoutEffect(() => {
+		prevZoomRef.current = zoomLevel;
+	}, [zoomLevel]);
+
+	const visibleStartTime = Math.max(
+		0,
+		(scrollLeft - bufferPx) / pixelsPerSecond,
+	);
+	const visibleEndTime =
+		(scrollLeft + viewportWidth + bufferPx) / pixelsPerSecond;
+
+	const startTickIndex = Math.max(
+		0,
+		Math.floor(visibleStartTime / tickIntervalSeconds),
+	);
+	const endTickIndex = Math.min(
+		tickCount - 1,
+		Math.ceil(visibleEndTime / tickIntervalSeconds),
+	);
+
+	const timelineTicks: Array<JSX.Element> = [];
+	for (
+		let tickIndex = startTickIndex;
+		tickIndex <= endTickIndex;
+		tickIndex += 1
+	) {
+		const time = tickIndex * tickIntervalSeconds;
+		if (time > effectiveDuration) break;
+
+		const showLabel = shouldShowLabel({ time, labelIntervalSeconds });
+		timelineTicks.push(
+			<TimelineTick
+				key={tickIndex}
+				time={time}
+				zoomLevel={zoomLevel}
+				fps={fps}
+				showLabel={showLabel}
+			/>,
+		);
+	}
+
+	return (
+		<div
+			role="slider"
+			tabIndex={0}
+			aria-label="Timeline ruler"
+			aria-valuemin={0}
+			aria-valuemax={effectiveDuration}
+			aria-valuenow={0}
+			className="relative h-4 flex-1 overflow-x-visible"
+			onWheel={handleWheel}
+			onClick={handleTimelineContentClick}
+			onMouseDown={handleRulerTrackingMouseDown}
+			onKeyDown={() => {}}
+		>
+			<div
+				role="none"
+				ref={rulerRef}
+				className="relative h-4 cursor-default select-none"
+				style={{
+					width: `${dynamicTimelineWidth}px`,
+				}}
+				onMouseDown={handleRulerMouseDown}
+			>
+				{timelineTicks}
+			</div>
+		</div>
+	);
+}
-- 
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