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

---
 .../src/timeline/components/timeline-playhead.tsx  | 117 +++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 apps/web/src/timeline/components/timeline-playhead.tsx

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

diff --git a/apps/web/src/timeline/components/timeline-playhead.tsx b/apps/web/src/timeline/components/timeline-playhead.tsx
new file mode 100644
index 00000000..4dd3329f
--- /dev/null
+++ b/apps/web/src/timeline/components/timeline-playhead.tsx
@@ -0,0 +1,117 @@
+"use client";
+
+import { useRef } from "react";
+import {
+	getCenteredLineLeft,
+	TIMELINE_INDICATOR_LINE_WIDTH_PX,
+	timelineTimeToSnappedPixels,
+} from "@/timeline";
+import { useTimelinePlayhead } from "@/timeline/hooks/use-timeline-playhead";
+import { TICKS_PER_SECOND } from "@/wasm";
+import { useEditor } from "@/editor/use-editor";
+import { TIMELINE_SCROLLBAR_SIZE_PX } from "./layout";
+import { TIMELINE_LAYERS } from "./layers";
+
+interface TimelinePlayheadProps {
+	zoomLevel: number;
+	hasHorizontalScrollbar: boolean;
+	rulerRef: React.RefObject<HTMLDivElement | null>;
+	rulerScrollRef: React.RefObject<HTMLDivElement | null>;
+	tracksScrollRef: React.RefObject<HTMLDivElement | null>;
+	timelineRef: React.RefObject<HTMLDivElement | null>;
+	playheadRef?: React.RefObject<HTMLDivElement | null>;
+	isSnappingToPlayhead?: boolean;
+}
+
+export function TimelinePlayhead({
+	zoomLevel,
+	hasHorizontalScrollbar,
+	rulerRef,
+	rulerScrollRef,
+	tracksScrollRef,
+	timelineRef,
+	playheadRef: externalPlayheadRef,
+	isSnappingToPlayhead = false,
+}: TimelinePlayheadProps) {
+	const editor = useEditor();
+	const duration = editor.timeline.getTotalDuration();
+	const internalPlayheadRef = useRef<HTMLDivElement>(null);
+	const playheadRef = externalPlayheadRef || internalPlayheadRef;
+
+	const { handlePlayheadMouseDown } = useTimelinePlayhead({
+		zoomLevel,
+		rulerRef,
+		rulerScrollRef,
+		tracksScrollRef,
+		playheadRef,
+	});
+
+	const timelineContainerHeight =
+		timelineRef.current?.clientHeight ??
+		tracksScrollRef.current?.clientHeight ??
+		400;
+	const totalHeight = Math.max(
+		0,
+		timelineContainerHeight -
+			(hasHorizontalScrollbar ? TIMELINE_SCROLLBAR_SIZE_PX - 5 : 0),
+	);
+
+	const currentTime = editor.playback.getCurrentTime();
+	const centerPosition = timelineTimeToSnappedPixels({
+		time: currentTime,
+		zoomLevel,
+	});
+	const scrollLeft = tracksScrollRef.current?.scrollLeft ?? 0;
+	const leftPosition =
+		getCenteredLineLeft({ centerPixel: centerPosition }) - scrollLeft;
+
+	const handlePlayheadKeyDown = (
+		event: React.KeyboardEvent<HTMLDivElement>,
+	) => {
+		if (event.key !== "ArrowLeft" && event.key !== "ArrowRight") return;
+
+		event.preventDefault();
+		const fps = editor.project.getActive().settings.fps;
+		const ticksPerFrame = Math.round(
+			(TICKS_PER_SECOND * fps.denominator) / fps.numerator,
+		);
+		const direction = event.key === "ArrowRight" ? 1 : -1;
+		const now = editor.playback.getCurrentTime();
+		const nextTime = Math.max(
+			0,
+			Math.min(duration, now + direction * ticksPerFrame),
+		);
+
+		editor.playback.seek({ time: nextTime });
+	};
+
+	return (
+		<div
+			ref={playheadRef}
+			role="slider"
+			aria-label="Timeline playhead"
+			aria-valuemin={0}
+			aria-valuemax={duration}
+			aria-valuenow={currentTime}
+			tabIndex={0}
+			className="pointer-events-none absolute"
+			style={{
+				left: `${leftPosition}px`,
+				top: 0,
+				height: `${totalHeight}px`,
+				width: `${TIMELINE_INDICATOR_LINE_WIDTH_PX}px`,
+				zIndex: TIMELINE_LAYERS.playhead,
+			}}
+			onKeyDown={handlePlayheadKeyDown}
+		>
+			<div className="bg-primary pointer-events-none absolute left-0 h-full w-0.5" />
+
+			<button
+				type="button"
+				aria-label="Drag playhead"
+				className={`pointer-events-auto absolute top-1 left-1/2 size-3 -translate-x-1/2 transform cursor-col-resize rounded-full border-2 shadow-xs ${isSnappingToPlayhead ? "bg-primary border-primary" : "bg-primary border-primary/50"}`}
+				onMouseDown={handlePlayheadMouseDown}
+			/>
+		</div>
+	);
+}
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