feat: add auto-follow zoom mode with cursor tracking

src/components/video-editor/SettingsPanel.tsx

@@ -52,6 +52,7 @@ import type {
 	PlaybackSpeed,
 	WebcamLayoutPreset,
 	ZoomDepth,
+	ZoomFocusMode,
 } from "./types";
 import { SPEED_OPTIONS } from "./types";
 
@@ -92,6 +93,9 @@ interface SettingsPanelProps {
 	onWallpaperChange: (path: string) => void;
 	selectedZoomDepth?: ZoomDepth | null;
 	onZoomDepthChange?: (depth: ZoomDepth) => void;
+	selectedZoomFocusMode?: ZoomFocusMode | null;
+	onZoomFocusModeChange?: (mode: ZoomFocusMode) => void;
+	hasCursorTelemetry?: boolean;
 	selectedZoomId?: string | null;
 	onZoomDelete?: (id: string) => void;
 	selectedTrimId?: string | null;
@@ -161,6 +165,9 @@ export function SettingsPanel({
 	onWallpaperChange,
 	selectedZoomDepth,
 	onZoomDepthChange,
+	selectedZoomFocusMode,
+	onZoomFocusModeChange,
+	hasCursorTelemetry = false,
 	selectedZoomId,
 	onZoomDelete,
 	selectedTrimId,
@@ -500,6 +507,41 @@ export function SettingsPanel({
 					{!zoomEnabled && (
 						<p className="text-[10px] text-slate-500 mt-2 text-center">{t("zoom.selectRegion")}</p>
 					)}
+					{zoomEnabled && hasCursorTelemetry && (
+						<div className="mt-3">
+							<span className="text-sm font-medium text-slate-200 mb-2 block">
+								{t("zoom.focusMode.title")}
+							</span>
+							<div className="grid grid-cols-2 gap-1.5">
+								{(["manual", "auto"] as const).map((mode) => {
+									const isActive = selectedZoomFocusMode === mode;
+									return (
+										<Button
+											key={mode}
+											type="button"
+											onClick={() => onZoomFocusModeChange?.(mode)}
+											className={cn(
+												"h-auto w-full rounded-lg border px-2 py-2 text-center shadow-sm transition-all",
+												"duration-200 ease-out cursor-pointer",
+												isActive
+													? "border-[#34B27B] bg-[#34B27B] text-white shadow-[#34B27B]/20"
+													: "border-white/5 bg-white/5 text-slate-400 hover:bg-white/10 hover:border-white/10 hover:text-slate-200",
+											)}
+										>
+											<span className="text-xs font-semibold capitalize">
+												{t(`zoom.focusMode.${mode}`)}
+											</span>
+										</Button>
+									);
+								})}
+							</div>
+							{selectedZoomFocusMode === "auto" && (
+								<p className="text-[10px] text-slate-500 mt-1.5">
+									{t("zoom.focusMode.autoDescription")}
+								</p>
+							)}
+						</div>
+					)}
 					{zoomEnabled && (
 						<Button
 							onClick={handleDeleteClick}

src/components/video-editor/VideoEditor.tsx

@@ -56,6 +56,7 @@ import {
 	type TrimRegion,
 	type ZoomDepth,
 	type ZoomFocus,
+	type ZoomFocusMode,
 	type ZoomRegion,
 } from "./types";
 import VideoPlayback, { VideoPlaybackRef } from "./VideoPlayback";
@@ -688,6 +689,18 @@ export default function VideoEditor() {
 		[selectedZoomId, pushState],
 	);
 
+	const handleZoomFocusModeChange = useCallback(
+		(focusMode: ZoomFocusMode) => {
+			if (!selectedZoomId) return;
+			pushState((prev) => ({
+				zoomRegions: prev.zoomRegions.map((region) =>
+					region.id === selectedZoomId ? { ...region, focusMode } : region,
+				),
+			}));
+		},
+		[selectedZoomId, pushState],
+	);
+
 	const handleZoomDelete = useCallback(
 		(id: string) => {
 			pushState((prev) => ({ zoomRegions: prev.zoomRegions.filter((r) => r.id !== id) }));
@@ -1093,6 +1106,7 @@ export default function VideoEditor() {
 						webcamPosition,
 						previewWidth,
 						previewHeight,
+						cursorTelemetry,
 						onProgress: (progress: ExportProgress) => {
 							setExportProgress(progress);
 						},
@@ -1224,6 +1238,7 @@ export default function VideoEditor() {
 						webcamPosition,
 						previewWidth,
 						previewHeight,
+						cursorTelemetry,
 						onProgress: (progress: ExportProgress) => {
 							setExportProgress(progress);
 						},
@@ -1292,6 +1307,7 @@ export default function VideoEditor() {
 			webcamPosition,
 			exportQuality,
 			handleExportSaved,
+			cursorTelemetry,
 		],
 	);
 
@@ -1502,6 +1518,7 @@ export default function VideoEditor() {
 											onSelectAnnotation={handleSelectAnnotation}
 											onAnnotationPositionChange={handleAnnotationPositionChange}
 											onAnnotationSizeChange={handleAnnotationSizeChange}
+											cursorTelemetry={cursorTelemetry}
 										/>
 									</div>
 								</div>
@@ -1584,6 +1601,13 @@ export default function VideoEditor() {
 							selectedZoomId ? zoomRegions.find((z) => z.id === selectedZoomId)?.depth : null
 						}
 						onZoomDepthChange={(depth) => selectedZoomId && handleZoomDepthChange(depth)}
+						selectedZoomFocusMode={
+							selectedZoomId
+								? (zoomRegions.find((z) => z.id === selectedZoomId)?.focusMode ?? "manual")
+								: null
+						}
+						onZoomFocusModeChange={(mode) => selectedZoomId && handleZoomFocusModeChange(mode)}
+						hasCursorTelemetry={cursorTelemetry.length > 0}
 						selectedZoomId={selectedZoomId}
 						onZoomDelete={handleZoomDelete}
 						selectedTrimId={selectedTrimId}

src/components/video-editor/VideoPlayback.tsx

@@ -41,10 +41,14 @@ import {
 	type ZoomRegion,
 } from "./types";
 import {
+	AUTO_FOLLOW_RAMP_DISTANCE,
+	AUTO_FOLLOW_SMOOTHING_FACTOR,
+	AUTO_FOLLOW_SMOOTHING_FACTOR_MAX,
 	DEFAULT_FOCUS,
 	ZOOM_SCALE_DEADZONE,
 	ZOOM_TRANSLATION_DEADZONE_PX,
 } from "./videoPlayback/constants";
+import { adaptiveSmoothFactor, smoothCursorFocus } from "./videoPlayback/cursorFollowUtils";
 import { clampFocusToStage as clampFocusToStageUtil } from "./videoPlayback/focusUtils";
 import { layoutVideoContent as layoutVideoContentUtil } from "./videoPlayback/layoutUtils";
 import { clamp01 } from "./videoPlayback/mathUtils";
@@ -93,6 +97,7 @@ interface VideoPlaybackProps {
 	onSelectAnnotation?: (id: string | null) => void;
 	onAnnotationPositionChange?: (id: string, position: { x: number; y: number }) => void;
 	onAnnotationSizeChange?: (id: string, size: { width: number; height: number }) => void;
+	cursorTelemetry?: import("./types").CursorTelemetryPoint[];
 }
 
 export interface VideoPlaybackRef {
@@ -141,6 +146,7 @@ const VideoPlayback = forwardRef<VideoPlaybackRef, VideoPlaybackProps>(
 			onSelectAnnotation,
 			onAnnotationPositionChange,
 			onAnnotationSizeChange,
+			cursorTelemetry = [],
 		},
 		ref,
 	) => {
@@ -160,6 +166,7 @@ const VideoPlayback = forwardRef<VideoPlaybackRef, VideoPlaybackProps>(
 		const [webcamDimensions, setWebcamDimensions] = useState<Size | null>(null);
 		const currentTimeRef = useRef(0);
 		const zoomRegionsRef = useRef<ZoomRegion[]>([]);
+		const cursorTelemetryRef = useRef<import("./types").CursorTelemetryPoint[]>([]);
 		const selectedZoomIdRef = useRef<string | null>(null);
 		const animationStateRef = useRef({
 			scale: 1,
@@ -194,6 +201,8 @@ const VideoPlayback = forwardRef<VideoPlaybackRef, VideoPlaybackProps>(
 		const onTimeUpdateRef = useRef(onTimeUpdate);
 		const onPlayStateChangeRef = useRef(onPlayStateChange);
 		const videoReadyRafRef = useRef<number | null>(null);
+		const smoothedAutoFocusRef = useRef<ZoomFocus | null>(null);
+		const prevTargetProgressRef = useRef(0);
 
 		const clampFocusToStage = useCallback((focus: ZoomFocus, depth: ZoomDepth) => {
 			return clampFocusToStageUtil(focus, depth, stageSizeRef.current);
@@ -379,6 +388,7 @@ const VideoPlayback = forwardRef<VideoPlaybackRef, VideoPlaybackProps>(
 			if (!regionId) return;
 			const region = zoomRegionsRef.current.find((r) => r.id === regionId);
 			if (!region) return;
+			if (region.focusMode === "auto") return;
 			onSelectZoom(region.id);
 			event.preventDefault();
 			isDraggingFocusRef.current = true;
@@ -462,6 +472,10 @@ const VideoPlayback = forwardRef<VideoPlaybackRef, VideoPlaybackProps>(
 			zoomRegionsRef.current = zoomRegions;
 		}, [zoomRegions]);
 
+		useEffect(() => {
+			cursorTelemetryRef.current = cursorTelemetry;
+		}, [cursorTelemetry]);
+
 		useEffect(() => {
 			selectedZoomIdRef.current = selectedZoomId;
 		}, [selectedZoomId]);
@@ -830,10 +844,16 @@ const VideoPlayback = forwardRef<VideoPlaybackRef, VideoPlaybackProps>(
 			};
 
 			const ticker = () => {
+				const bm = baseMaskRef.current;
+				const ss = stageSizeRef.current;
+				const viewportRatio =
+					bm.width > 0 && bm.height > 0
+						? { widthRatio: ss.width / bm.width, heightRatio: ss.height / bm.height }
+						: undefined;
 				const { region, strength, blendedScale, transition } = findDominantRegion(
 					zoomRegionsRef.current,
 					currentTimeRef.current,
-					{ connectZooms: true },
+					{ connectZooms: true, cursorTelemetry: cursorTelemetryRef.current, viewportRatio },
 				);
 
 				const defaultFocus = DEFAULT_FOCUS;
@@ -854,6 +874,47 @@ const VideoPlayback = forwardRef<VideoPlaybackRef, VideoPlaybackProps>(
 					targetFocus = regionFocus;
 					targetProgress = strength;
 
+					// Apply adaptive smoothing for auto-follow mode
+					if (region.focusMode === "auto" && !transition) {
+						const raw = targetFocus;
+						const isZoomingIn =
+							targetProgress < 0.999 && targetProgress >= prevTargetProgressRef.current;
+						if (targetProgress >= 0.999) {
+							// Full zoom: adaptive smoothing — moves faster when far, decelerates when close
+							const prev = smoothedAutoFocusRef.current ?? raw;
+							const factor = adaptiveSmoothFactor(
+								raw,
+								prev,
+								AUTO_FOLLOW_SMOOTHING_FACTOR,
+								AUTO_FOLLOW_SMOOTHING_FACTOR_MAX,
+								AUTO_FOLLOW_RAMP_DISTANCE,
+							);
+							const smoothed = smoothCursorFocus(raw, prev, factor);
+							smoothedAutoFocusRef.current = smoothed;
+							targetFocus = smoothed;
+						} else if (isZoomingIn) {
+							// Zoom-in: track cursor directly so zoom always aims at current cursor
+							// position; keep ref in sync to avoid snap when full-zoom begins
+							smoothedAutoFocusRef.current = raw;
+						} else {
+							// Zoom-out: keep smoothing for continuity — avoids snap at zoom-out start
+							const prev = smoothedAutoFocusRef.current ?? raw;
+							const factor = adaptiveSmoothFactor(
+								raw,
+								prev,
+								AUTO_FOLLOW_SMOOTHING_FACTOR,
+								AUTO_FOLLOW_SMOOTHING_FACTOR_MAX,
+								AUTO_FOLLOW_RAMP_DISTANCE,
+							);
+							const smoothed = smoothCursorFocus(raw, prev, factor);
+							smoothedAutoFocusRef.current = smoothed;
+							targetFocus = smoothed;
+						}
+					} else if (region.focusMode !== "auto") {
+						smoothedAutoFocusRef.current = null;
+					}
+					prevTargetProgressRef.current = targetProgress;
+
 					// Handle connected zoom transitions (pan between adjacent zoom regions)
 					if (transition) {
 						const startTransform = computeZoomTransform({

src/components/video-editor/projectPersistence.ts

@@ -189,6 +189,7 @@ export function normalizeProjectEditor(editor: Partial<ProjectEditorState>): Pro
 							cx: clamp(isFiniteNumber(region.focus?.cx) ? region.focus.cx : 0.5, 0, 1),
 							cy: clamp(isFiniteNumber(region.focus?.cy) ? region.focus.cy : 0.5, 0, 1),
 						},
+						focusMode: region.focusMode === "auto" ? "auto" : "manual",
 					};
 				})
 		: [];

src/components/video-editor/types.ts

@@ -1,6 +1,7 @@
 import type { WebcamLayoutPreset } from "@/lib/compositeLayout";
 
 export type ZoomDepth = 1 | 2 | 3 | 4 | 5 | 6;
+export type ZoomFocusMode = "manual" | "auto";
 export type { WebcamLayoutPreset };
 
 export const DEFAULT_WEBCAM_LAYOUT_PRESET: WebcamLayoutPreset = "picture-in-picture";
@@ -23,6 +24,7 @@ export interface ZoomRegion {
 	endMs: number;
 	depth: ZoomDepth;
 	focus: ZoomFocus;
+	focusMode?: ZoomFocusMode;
 }
 
 export interface CursorTelemetryPoint {

src/components/video-editor/videoPlayback/constants.ts

@@ -8,3 +8,6 @@ export const VIEWPORT_SCALE = 0.8;
 export const SMOOTHING_FACTOR = 0.12;
 export const ZOOM_TRANSLATION_DEADZONE_PX = 1.25;
 export const ZOOM_SCALE_DEADZONE = 0.002;
+export const AUTO_FOLLOW_SMOOTHING_FACTOR = 0.1;
+export const AUTO_FOLLOW_SMOOTHING_FACTOR_MAX = 0.25;
+export const AUTO_FOLLOW_RAMP_DISTANCE = 0.15;

src/components/video-editor/videoPlayback/cursorFollowUtils.ts

@@ -0,0 +1,73 @@
+import type { CursorTelemetryPoint, ZoomFocus } from "../types";
+
+/**
+ * Binary-search the sorted telemetry array and linearly interpolate
+ * the cursor position at the given playback time.
+ */
+export function interpolateCursorAt(
+	telemetry: CursorTelemetryPoint[],
+	timeMs: number,
+): ZoomFocus | null {
+	if (telemetry.length === 0) return null;
+
+	if (timeMs <= telemetry[0].timeMs) {
+		return { cx: telemetry[0].cx, cy: telemetry[0].cy };
+	}
+
+	const last = telemetry[telemetry.length - 1];
+	if (timeMs >= last.timeMs) {
+		return { cx: last.cx, cy: last.cy };
+	}
+
+	let lo = 0;
+	let hi = telemetry.length - 1;
+
+	while (lo < hi - 1) {
+		const mid = (lo + hi) >>> 1;
+		if (telemetry[mid].timeMs <= timeMs) {
+			lo = mid;
+		} else {
+			hi = mid;
+		}
+	}
+
+	const before = telemetry[lo];
+	const after = telemetry[hi];
+	const span = after.timeMs - before.timeMs;
+	const t = span > 0 ? (timeMs - before.timeMs) / span : 0;
+
+	return {
+		cx: before.cx + (after.cx - before.cx) * t,
+		cy: before.cy + (after.cy - before.cy) * t,
+	};
+}
+
+/**
+ * Exponential smoothing to reduce jitter from high-frequency cursor data.
+ * Lower factor = smoother / more lag, higher = more responsive.
+ */
+export function smoothCursorFocus(raw: ZoomFocus, prev: ZoomFocus, factor: number): ZoomFocus {
+	return {
+		cx: prev.cx + (raw.cx - prev.cx) * factor,
+		cy: prev.cy + (raw.cy - prev.cy) * factor,
+	};
+}
+
+/**
+ * Compute an adaptive smoothing factor that scales with distance:
+ * far from target → faster (maxFactor), close → slower (minFactor).
+ * This replaces the hard deadzone with a natural deceleration curve.
+ */
+export function adaptiveSmoothFactor(
+	raw: ZoomFocus,
+	prev: ZoomFocus,
+	minFactor: number,
+	maxFactor: number,
+	rampDistance: number,
+): number {
+	const dx = raw.cx - prev.cx;
+	const dy = raw.cy - prev.cy;
+	const distance = Math.sqrt(dx * dx + dy * dy);
+	const t = Math.min(1, distance / rampDistance);
+	return minFactor + (maxFactor - minFactor) * t;
+}