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+"use client";
+
+import {
+ createContext,
+ useCallback,
+ useContext,
+ useEffect,
+ useMemo,
+ useRef,
+ useState,
+} from "react";
+import {
+ canvasToOverlay,
+ getDisplayScale,
+ positionToOverlay,
+ screenPixelsToLogicalThreshold,
+ screenToCanvas,
+} from "@/preview/preview-coords";
+import { clamp, isNearlyEqual } from "@/utils/math";
+import { PREVIEW_ZOOM } from "@/preview/zoom";
+
+const MIDDLE_MOUSE_BUTTON = 1;
+const IS_AT_FIT_EPSILON = 0.001;
+const IS_AT_ACTUAL_SIZE_EPSILON = 0.01;
+
+interface PreviewViewportContextValue {
+ canPan: boolean;
+ isAtFit: boolean;
+ isAtActualSize: boolean;
+ isPanning: boolean;
+ sceneHeight: number;
+ sceneLeft: number;
+ sceneTop: number;
+ sceneWidth: number;
+ zoomPercent: number;
+ canvasToOverlay: ({
+ canvasX,
+ canvasY,
+ }: {
+ canvasX: number;
+ canvasY: number;
+ }) => { x: number; y: number };
+ fitToScreen: () => void;
+ getDisplayScale: () => { x: number; y: number };
+ handlePanPointerDown: ({ event }: { event: React.PointerEvent }) => boolean;
+ handlePanPointerMove: ({ event }: { event: React.PointerEvent }) => boolean;
+ handlePanPointerUp: ({ event }: { event: React.PointerEvent }) => boolean;
+ positionToOverlay: ({
+ positionX,
+ positionY,
+ }: {
+ positionX: number;
+ positionY: number;
+ }) => { x: number; y: number };
+ panByScreenDelta: ({
+ deltaX,
+ deltaY,
+ }: {
+ deltaX: number;
+ deltaY: number;
+ }) => void;
+ resetPan: () => void;
+ scaleZoom: ({ factor }: { factor: number }) => void;
+ screenPixelsToLogicalThreshold: ({
+ screenPixels,
+ }: {
+ screenPixels: number;
+ }) => { x: number; y: number };
+ screenToCanvas: ({
+ clientX,
+ clientY,
+ }: {
+ clientX: number;
+ clientY: number;
+ }) => { x: number; y: number } | null;
+ setActualSize: () => void;
+ setViewportPercent: ({ percent }: { percent: number }) => void;
+ zoomIn: () => void;
+ zoomOut: () => void;
+}
+
+const PreviewViewportContext =
+ createContext<PreviewViewportContextValue | null>(null);
+
+interface PreviewViewportProviderProps {
+ children: React.ReactNode;
+ value: PreviewViewportContextValue;
+}
+
+interface PreviewViewportStateOptions {
+ canvasHeight: number;
+ canvasWidth: number;
+ viewportHeight: number;
+ viewportRef: React.RefObject<HTMLDivElement | null>;
+ viewportWidth: number;
+}
+
+interface PanSession {
+ centerX: number;
+ centerY: number;
+ clientX: number;
+ clientY: number;
+ pointerId: number;
+}
+
+function getClampedCenterAxis({
+ axisSize,
+ center,
+ scale,
+ viewportSize,
+}: {
+ axisSize: number;
+ center: number;
+ scale: number;
+ viewportSize: number;
+}): number {
+ if (axisSize <= 0 || scale <= 0 || viewportSize <= 0) {
+ return axisSize / 2;
+ }
+
+ const visibleHalfSpan = viewportSize / (2 * scale);
+ if (visibleHalfSpan >= axisSize / 2) {
+ return axisSize / 2;
+ }
+
+ return clamp({
+ value: center,
+ min: visibleHalfSpan,
+ max: axisSize - visibleHalfSpan,
+ });
+}
+
+function clampViewportCenter({
+ canvasHeight,
+ canvasWidth,
+ centerX,
+ centerY,
+ scale,
+ viewportHeight,
+ viewportWidth,
+}: {
+ canvasHeight: number;
+ canvasWidth: number;
+ centerX: number;
+ centerY: number;
+ scale: number;
+ viewportHeight: number;
+ viewportWidth: number;
+}): { x: number; y: number } {
+ return {
+ x: getClampedCenterAxis({
+ center: centerX,
+ axisSize: canvasWidth,
+ scale,
+ viewportSize: viewportWidth,
+ }),
+ y: getClampedCenterAxis({
+ center: centerY,
+ axisSize: canvasHeight,
+ scale,
+ viewportSize: viewportHeight,
+ }),
+ };
+}
+
+function getFitScale({
+ canvasHeight,
+ canvasWidth,
+ viewportHeight,
+ viewportWidth,
+}: {
+ canvasHeight: number;
+ canvasWidth: number;
+ viewportHeight: number;
+ viewportWidth: number;
+}): number {
+ if (
+ canvasHeight <= 0 ||
+ canvasWidth <= 0 ||
+ viewportHeight <= 0 ||
+ viewportWidth <= 0
+ ) {
+ return 1;
+ }
+
+ return Math.min(viewportWidth / canvasWidth, viewportHeight / canvasHeight);
+}
+
+function getClampedZoom({ zoom }: { zoom: number }): number {
+ return clamp({
+ value: zoom,
+ min: PREVIEW_ZOOM.min,
+ max: PREVIEW_ZOOM.max,
+ });
+}
+
+export function PreviewViewportProvider({
+ children,
+ value,
+}: PreviewViewportProviderProps) {
+ return (
+ <PreviewViewportContext.Provider value={value}>
+ {children}
+ </PreviewViewportContext.Provider>
+ );
+}
+
+export function usePreviewViewportState({
+ canvasHeight,
+ canvasWidth,
+ viewportHeight,
+ viewportRef,
+ viewportWidth,
+}: PreviewViewportStateOptions): PreviewViewportContextValue {
+ const [zoom, setZoomState] = useState(1);
+ const [center, setCenter] = useState(() => ({
+ x: canvasWidth / 2,
+ y: canvasHeight / 2,
+ }));
+ const [isPanning, setIsPanning] = useState(false);
+ const panSessionRef = useRef<PanSession | null>(null);
+ const centerRef = useRef(center);
+ centerRef.current = center;
+
+ const fitScale = useMemo(
+ () =>
+ getFitScale({
+ canvasHeight,
+ canvasWidth,
+ viewportHeight,
+ viewportWidth,
+ }),
+ [canvasHeight, canvasWidth, viewportHeight, viewportWidth],
+ );
+ const viewportScale = fitScale * zoom;
+ const geometry = useMemo(
+ () => ({
+ canvasHeight,
+ canvasWidth,
+ centerX: center.x,
+ centerY: center.y,
+ scale: viewportScale,
+ viewportHeight,
+ viewportWidth,
+ }),
+ [
+ canvasHeight,
+ canvasWidth,
+ center.x,
+ center.y,
+ viewportHeight,
+ viewportScale,
+ viewportWidth,
+ ],
+ );
+
+ const scaleZoom = useCallback(({ factor }: { factor: number }) => {
+ setZoomState((previousZoom) =>
+ getClampedZoom({
+ zoom: previousZoom * factor,
+ }),
+ );
+ }, []);
+
+ const panByScreenDelta = useCallback(
+ ({ deltaX, deltaY }: { deltaX: number; deltaY: number }) => {
+ if (zoom <= 1 || (deltaX === 0 && deltaY === 0)) {
+ return;
+ }
+
+ setCenter((previousCenter) =>
+ clampViewportCenter({
+ canvasHeight,
+ canvasWidth,
+ centerX: previousCenter.x + deltaX / viewportScale,
+ centerY: previousCenter.y + deltaY / viewportScale,
+ scale: viewportScale,
+ viewportHeight,
+ viewportWidth,
+ }),
+ );
+ },
+ [
+ canvasHeight,
+ canvasWidth,
+ viewportHeight,
+ viewportScale,
+ viewportWidth,
+ zoom,
+ ],
+ );
+
+ const resetPan = useCallback(() => {
+ setCenter({
+ x: canvasWidth / 2,
+ y: canvasHeight / 2,
+ });
+ }, [canvasHeight, canvasWidth]);
+
+ const fitToScreen = useCallback(() => {
+ setZoomState(1);
+ setCenter({
+ x: canvasWidth / 2,
+ y: canvasHeight / 2,
+ });
+ }, [canvasHeight, canvasWidth]);
+
+ const zoomIn = useCallback(() => {
+ setZoomState((previousZoom) =>
+ getClampedZoom({
+ zoom: previousZoom * PREVIEW_ZOOM.step,
+ }),
+ );
+ }, []);
+
+ const zoomOut = useCallback(() => {
+ setZoomState((previousZoom) =>
+ getClampedZoom({
+ zoom: previousZoom / PREVIEW_ZOOM.step,
+ }),
+ );
+ }, []);
+
+ const setActualSize = useCallback(() => {
+ const actualSizeZoom = fitScale > 0 ? 1 / fitScale : 1;
+ setZoomState(
+ getClampedZoom({
+ zoom: actualSizeZoom,
+ }),
+ );
+ }, [fitScale]);
+
+ const setViewportPercent = useCallback(
+ ({ percent }: { percent: number }) => {
+ const targetZoom = fitScale > 0 ? percent / 100 / fitScale : 1;
+ setZoomState(getClampedZoom({ zoom: targetZoom }));
+ },
+ [fitScale],
+ );
+
+ const getViewportRect = useCallback(
+ () => viewportRef.current?.getBoundingClientRect() ?? null,
+ [viewportRef],
+ );
+
+ const screenToCanvasWithViewport = useCallback(
+ ({ clientX, clientY }: { clientX: number; clientY: number }) => {
+ const viewportRect = getViewportRect();
+ if (!viewportRect) return null;
+
+ return screenToCanvas({
+ clientX,
+ clientY,
+ geometry,
+ viewportRect,
+ });
+ },
+ [getViewportRect, geometry],
+ );
+
+ const canvasToOverlayWithViewport = useCallback(
+ ({ canvasX, canvasY }: { canvasX: number; canvasY: number }) =>
+ canvasToOverlay({
+ canvasX,
+ canvasY,
+ geometry,
+ }),
+ [geometry],
+ );
+
+ const positionToOverlayWithViewport = useCallback(
+ ({ positionX, positionY }: { positionX: number; positionY: number }) =>
+ positionToOverlay({
+ geometry,
+ positionX,
+ positionY,
+ }),
+ [geometry],
+ );
+
+ const getDisplayScaleWithViewport = useCallback(
+ () => getDisplayScale({ geometry }),
+ [geometry],
+ );
+
+ const getLogicalThresholdForScreenPixels = useCallback(
+ ({ screenPixels }: { screenPixels: number }) =>
+ screenPixelsToLogicalThreshold({
+ geometry,
+ screenPixels,
+ }),
+ [geometry],
+ );
+
+ const handlePanPointerDown = useCallback(
+ ({ event }: { event: React.PointerEvent }) => {
+ if (event.button !== MIDDLE_MOUSE_BUTTON || zoom <= 1) {
+ return false;
+ }
+
+ event.preventDefault();
+ event.stopPropagation();
+
+ panSessionRef.current = {
+ centerX: centerRef.current.x,
+ centerY: centerRef.current.y,
+ clientX: event.clientX,
+ clientY: event.clientY,
+ pointerId: event.pointerId,
+ };
+ setIsPanning(true);
+ (event.currentTarget as HTMLElement).setPointerCapture(event.pointerId);
+ return true;
+ },
+ [zoom],
+ );
+
+ const handlePanPointerMove = useCallback(
+ ({ event }: { event: React.PointerEvent }) => {
+ const panSession = panSessionRef.current;
+ if (!panSession) {
+ return false;
+ }
+
+ event.preventDefault();
+ event.stopPropagation();
+
+ const deltaX = event.clientX - panSession.clientX;
+ const deltaY = event.clientY - panSession.clientY;
+ const nextCenter = clampViewportCenter({
+ canvasHeight,
+ canvasWidth,
+ centerX: panSession.centerX - deltaX / viewportScale,
+ centerY: panSession.centerY - deltaY / viewportScale,
+ scale: viewportScale,
+ viewportHeight,
+ viewportWidth,
+ });
+
+ setCenter(nextCenter);
+ return true;
+ },
+ [canvasHeight, canvasWidth, viewportHeight, viewportScale, viewportWidth],
+ );
+
+ const handlePanPointerUp = useCallback(
+ ({ event }: { event: React.PointerEvent }) => {
+ const panSession = panSessionRef.current;
+ if (!panSession) {
+ return false;
+ }
+
+ if (
+ (event.currentTarget as HTMLElement).hasPointerCapture(
+ panSession.pointerId,
+ )
+ ) {
+ (event.currentTarget as HTMLElement).releasePointerCapture(
+ panSession.pointerId,
+ );
+ }
+
+ panSessionRef.current = null;
+ setIsPanning(false);
+ return true;
+ },
+ [],
+ );
+
+ useEffect(() => {
+ setZoomState(1);
+ setCenter({
+ x: canvasWidth / 2,
+ y: canvasHeight / 2,
+ });
+ panSessionRef.current = null;
+ setIsPanning(false);
+ }, [canvasHeight, canvasWidth]);
+
+ useEffect(() => {
+ setCenter((previousCenter) =>
+ clampViewportCenter({
+ canvasHeight,
+ canvasWidth,
+ centerX: previousCenter.x,
+ centerY: previousCenter.y,
+ scale: viewportScale,
+ viewportHeight,
+ viewportWidth,
+ }),
+ );
+ }, [canvasHeight, canvasWidth, viewportHeight, viewportScale, viewportWidth]);
+
+ const sceneWidth = canvasWidth * viewportScale;
+ const sceneHeight = canvasHeight * viewportScale;
+ const sceneLeft = viewportWidth / 2 - center.x * viewportScale;
+ const sceneTop = viewportHeight / 2 - center.y * viewportScale;
+ const canPan = zoom > 1;
+ const zoomPercent = Math.round(viewportScale * 100);
+
+ return useMemo(
+ () => ({
+ canPan,
+ isAtActualSize: isNearlyEqual({
+ leftValue: viewportScale,
+ rightValue: 1,
+ epsilon: IS_AT_ACTUAL_SIZE_EPSILON,
+ }),
+ isAtFit: isNearlyEqual({
+ leftValue: zoom,
+ rightValue: 1,
+ epsilon: IS_AT_FIT_EPSILON,
+ }),
+ isPanning,
+ sceneHeight,
+ sceneLeft,
+ sceneTop,
+ sceneWidth,
+ zoomPercent,
+ canvasToOverlay: canvasToOverlayWithViewport,
+ fitToScreen,
+ getDisplayScale: getDisplayScaleWithViewport,
+ handlePanPointerDown,
+ handlePanPointerMove,
+ handlePanPointerUp,
+ panByScreenDelta,
+ positionToOverlay: positionToOverlayWithViewport,
+ resetPan,
+ scaleZoom,
+ screenPixelsToLogicalThreshold: getLogicalThresholdForScreenPixels,
+ screenToCanvas: screenToCanvasWithViewport,
+ setActualSize,
+ setViewportPercent,
+ zoomIn,
+ zoomOut,
+ }),
+ [
+ canPan,
+ viewportScale,
+ zoom,
+ isPanning,
+ sceneHeight,
+ sceneLeft,
+ sceneTop,
+ sceneWidth,
+ zoomPercent,
+ canvasToOverlayWithViewport,
+ fitToScreen,
+ getDisplayScaleWithViewport,
+ handlePanPointerDown,
+ handlePanPointerMove,
+ handlePanPointerUp,
+ panByScreenDelta,
+ positionToOverlayWithViewport,
+ resetPan,
+ scaleZoom,
+ getLogicalThresholdForScreenPixels,
+ screenToCanvasWithViewport,
+ setActualSize,
+ setViewportPercent,
+ zoomIn,
+ zoomOut,
+ ],
+ );
+}
+
+export function usePreviewViewport() {
+ const context = useContext(PreviewViewportContext);
+ if (!context) {
+ throw new Error(
+ "usePreviewViewport must be used within PreviewViewportProvider",
+ );
+ }
+
+ return context;
+}
generated by cgit v1.3.1 (git 2.54.0) at 2026-10-17 06:56:06 +0000