From 3e89d2998588f8e35c524e523ba2ee853f0f6475 Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Mon, 20 Apr 2026 11:31:17 +0200
Subject: refactor: restructure files to their domains,  new preview overlay
 system, and dep graph

---
 .../web/src/timeline/components/timeline-ruler.tsx | 146 +++++++++++++++++++++
 1 file changed, 146 insertions(+)
 create mode 100644 apps/web/src/timeline/components/timeline-ruler.tsx

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

diff --git a/apps/web/src/timeline/components/timeline-ruler.tsx b/apps/web/src/timeline/components/timeline-ruler.tsx
new file mode 100644
index 00000000..e2a379ee
--- /dev/null
+++ b/apps/web/src/timeline/components/timeline-ruler.tsx
@@ -0,0 +1,146 @@
+import { type JSX, useLayoutEffect, useRef } from "react";
+import { BASE_TIMELINE_PIXELS_PER_SECOND } from "@/timeline/scale";
+import { mediaTimeToSeconds } from "opencut-wasm";
+import { TICKS_PER_SECOND } from "@/wasm";
+import { TIMELINE_RULER_HEIGHT_PX } from "./layout";
+import { DEFAULT_FPS } from "@/fps/defaults";
+import { useEditor } from "@/editor/use-editor";
+import { getRulerConfig, shouldShowLabel } from "@/timeline/ruler-utils";
+import { useScrollPosition } from "@/timeline/hooks/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 durationTicks = useEditor((e) => e.timeline.getTotalDuration());
+	const durationSeconds = mediaTimeToSeconds({ time: durationTicks });
+	const pixelsPerSecond = BASE_TIMELINE_PIXELS_PER_SECOND * zoomLevel;
+	const visibleDurationSeconds = dynamicTimelineWidth / pixelsPerSecond;
+	const effectiveDurationSeconds = Math.max(
+		durationSeconds,
+		visibleDurationSeconds,
+	);
+	const fps =
+		useEditor((e) => e.project.getActiveOrNull()?.settings.fps) ?? DEFAULT_FPS;
+	const { labelIntervalSeconds, tickIntervalSeconds } = getRulerConfig({
+		zoomLevel,
+		fps,
+	});
+	const tickCount =
+		Math.ceil(effectiveDurationSeconds / 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 visibleStartTimeSeconds = Math.max(
+		0,
+		(scrollLeft - bufferPx) / pixelsPerSecond,
+	);
+	const visibleEndTimeSeconds =
+		(scrollLeft + viewportWidth + bufferPx) / pixelsPerSecond;
+
+	const startTickIndex = Math.max(
+		0,
+		Math.floor(visibleStartTimeSeconds / tickIntervalSeconds),
+	);
+	const endTickIndex = Math.min(
+		tickCount - 1,
+		Math.ceil(visibleEndTimeSeconds / tickIntervalSeconds),
+	);
+
+	const timelineTicks: Array<JSX.Element> = [];
+	for (
+		let tickIndex = startTickIndex;
+		tickIndex <= endTickIndex;
+		tickIndex += 1
+	) {
+		const timeSeconds = tickIndex * tickIntervalSeconds;
+		if (timeSeconds > effectiveDurationSeconds) break;
+
+		const timeTicks = Math.round(timeSeconds * TICKS_PER_SECOND);
+		const showLabel = shouldShowLabel({
+			time: timeSeconds,
+			labelIntervalSeconds,
+		});
+		timelineTicks.push(
+			<TimelineTick
+				key={tickIndex}
+				time={timeTicks}
+				timeInSeconds={timeSeconds}
+				zoomLevel={zoomLevel}
+				fps={fps}
+				showLabel={showLabel}
+			/>,
+		);
+	}
+
+	return (
+		<div
+			role="slider"
+			tabIndex={0}
+			aria-label="Timeline ruler"
+			aria-valuemin={0}
+			aria-valuemax={effectiveDurationSeconds}
+			aria-valuenow={0}
+			className="relative flex-1 overflow-x-visible"
+			style={{ height: TIMELINE_RULER_HEIGHT_PX }}
+			onWheel={handleWheel}
+			onClick={(event) => {
+				// Ruler seek already happens on mousedown via playhead scrubbing.
+				// Forwarding the follow-up click re-enters the selection-clearing path.
+				if (event.target === event.currentTarget) {
+					handleTimelineContentClick(event);
+				}
+			}}
+			onMouseDown={handleRulerTrackingMouseDown}
+			onKeyDown={() => {}}
+		>
+			<div
+				role="none"
+				ref={rulerRef}
+				className="relative cursor-default select-none"
+				style={{
+					height: TIMELINE_RULER_HEIGHT_PX,
+					width: `${dynamicTimelineWidth}px`,
+				}}
+				onMouseDown={handleRulerMouseDown}
+			>
+				{timelineTicks}
+			</div>
+		</div>
+	);
+}
-- 
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