Harden camera zoom helper restore and key namespace

web/src/utils/cameraZoom.ts

@@ -0,0 +1,162 @@
+export const CAMERA_ZOOM_MIN_SCALE = 1;
+export const CAMERA_ZOOM_MAX_SCALE = 8;
+// Tuning constant for discrete shift+wheel zoom on grid cards.
+export const CAMERA_ZOOM_SHIFT_WHEEL_STEP = 0.1;
+
+export type CameraZoomRuntimeTransform = {
+  scale: number;
+  positionX: number;
+  positionY: number;
+};
+
+export type CameraZoomDimensions = {
+  viewportWidth: number;
+  viewportHeight: number;
+  contentWidth: number;
+  contentHeight: number;
+};
+
+export type CameraZoomPersistedState = {
+  /**
+   * Scale normalized to a [0, 1] range between min and max zoom.
+   */
+  normalizedScale: number;
+  /**
+   * Relative content x-coordinate (0..1) that should map to the viewport center.
+   */
+  focusX: number;
+  /**
+   * Relative content y-coordinate (0..1) that should map to the viewport center.
+   */
+  focusY: number;
+};
+
+export function clamp(value: number, min: number, max: number): number {
+  return Math.min(max, Math.max(min, value));
+}
+
+export function clampScale(
+  scale: number,
+  minScale: number = CAMERA_ZOOM_MIN_SCALE,
+  maxScale: number = CAMERA_ZOOM_MAX_SCALE,
+): number {
+  return clamp(scale, minScale, maxScale);
+}
+
+export function normalizeScale(
+  scale: number,
+  minScale: number = CAMERA_ZOOM_MIN_SCALE,
+  maxScale: number = CAMERA_ZOOM_MAX_SCALE,
+): number {
+  if (maxScale <= minScale) {
+    return 0;
+  }
+
+  return clamp(
+    (clampScale(scale, minScale, maxScale) - minScale) / (maxScale - minScale),
+    0,
+    1,
+  );
+}
+
+export function denormalizeScale(
+  normalizedScale: number,
+  minScale: number = CAMERA_ZOOM_MIN_SCALE,
+  maxScale: number = CAMERA_ZOOM_MAX_SCALE,
+): number {
+  if (maxScale <= minScale) {
+    return minScale;
+  }
+
+  const normalized = clamp(normalizedScale, 0, 1);
+  return minScale + normalized * (maxScale - minScale);
+}
+
+/**
+ * Calculates a new pan position to keep the content under the cursor fixed
+ * while changing scale.
+ */
+export function getCursorRelativeZoomTransform(
+  current: CameraZoomRuntimeTransform,
+  targetScale: number,
+  cursorX: number,
+  cursorY: number,
+  minScale: number = CAMERA_ZOOM_MIN_SCALE,
+  maxScale: number = CAMERA_ZOOM_MAX_SCALE,
+): CameraZoomRuntimeTransform {
+  const nextScale = clampScale(targetScale, minScale, maxScale);
+  const safeCurrentScale =
+    Number.isFinite(current.scale) && current.scale > 0
+      ? current.scale
+      : CAMERA_ZOOM_MIN_SCALE;
+  const contentX = (cursorX - current.positionX) / safeCurrentScale;
+  const contentY = (cursorY - current.positionY) / safeCurrentScale;
+
+  return {
+    scale: nextScale,
+    positionX: cursorX - contentX * nextScale,
+    positionY: cursorY - contentY * nextScale,
+  };
+}
+
+export function toPersistedCameraZoomState(
+  runtime: CameraZoomRuntimeTransform,
+  dimensions: CameraZoomDimensions,
+  minScale: number = CAMERA_ZOOM_MIN_SCALE,
+  maxScale: number = CAMERA_ZOOM_MAX_SCALE,
+): CameraZoomPersistedState {
+  const safeContentWidth = dimensions.contentWidth || 1;
+  const safeContentHeight = dimensions.contentHeight || 1;
+  const safeScale =
+    Number.isFinite(runtime.scale) && runtime.scale > 0
+      ? runtime.scale
+      : CAMERA_ZOOM_MIN_SCALE;
+  const centerContentX =
+    (dimensions.viewportWidth / 2 - runtime.positionX) / safeScale;
+  const centerContentY =
+    (dimensions.viewportHeight / 2 - runtime.positionY) / safeScale;
+
+  return {
+    normalizedScale: normalizeScale(runtime.scale, minScale, maxScale),
+    focusX: clamp(centerContentX / safeContentWidth, 0, 1),
+    focusY: clamp(centerContentY / safeContentHeight, 0, 1),
+  };
+}
+
+export function fromPersistedCameraZoomState(
+  persisted: CameraZoomPersistedState,
+  dimensions: CameraZoomDimensions,
+  minScale: number = CAMERA_ZOOM_MIN_SCALE,
+  maxScale: number = CAMERA_ZOOM_MAX_SCALE,
+): CameraZoomRuntimeTransform {
+  const scale = denormalizeScale(persisted.normalizedScale, minScale, maxScale);
+  const safeContentWidth = dimensions.contentWidth || 1;
+  const safeContentHeight = dimensions.contentHeight || 1;
+  const contentX = clamp(persisted.focusX, 0, 1) * safeContentWidth;
+  const contentY = clamp(persisted.focusY, 0, 1) * safeContentHeight;
+
+  return {
+    scale,
+    positionX: dimensions.viewportWidth / 2 - contentX * scale,
+    positionY: dimensions.viewportHeight / 2 - contentY * scale,
+  };
+}
+
+export function getNextScaleFromWheelDelta(
+  currentScale: number,
+  wheelDeltaY: number,
+  step: number = CAMERA_ZOOM_SHIFT_WHEEL_STEP,
+  minScale: number = CAMERA_ZOOM_MIN_SCALE,
+  maxScale: number = CAMERA_ZOOM_MAX_SCALE,
+): number {
+  if (wheelDeltaY === 0) {
+    return clampScale(currentScale, minScale, maxScale);
+  }
+
+  const direction = wheelDeltaY > 0 ? -1 : 1;
+  return clampScale(currentScale + direction * step, minScale, maxScale);
+}
+
+export function getCameraZoomStorageKey(cameraName: string): string {
+  return `live:grid-card:zoom:${cameraName}`;
+}