feat(scene): shared zoom/pan for control and presentation

Keep effects pinned to map coordinates when the viewport changes; materials/NPC overlays stay screen-fixed.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/main/sceneView/sceneViewStore.test.ts

@@ -0,0 +1,67 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+
+import {
+  DEFAULT_SCENE_VIEW_CAMERA,
+  sceneViewPanBy,
+  sceneViewZoomAt,
+} from '../../shared/types/sceneView';
+
+import { SceneViewStore } from './sceneViewStore';
+
+describe('SceneViewStore', () => {
+  it('resets to default camera', () => {
+    const store = new SceneViewStore();
+    store.dispatch({ kind: 'set', camera: { scale: 2, ox: 0.2, oy: 0.8 } });
+    const next = store.dispatch({ kind: 'reset' });
+    assert.equal(next.scale, 1);
+    assert.equal(next.ox, 0.5);
+    assert.equal(next.oy, 0.5);
+  });
+
+  it('clamps scale and origin', () => {
+    const store = new SceneViewStore();
+    const next = store.dispatch({ kind: 'set', camera: { scale: 99, ox: -1, oy: 2 } });
+    assert.equal(next.scale, 8);
+    assert.equal(next.ox, 0);
+    assert.equal(next.oy, 1);
+  });
+});
+
+describe('sceneViewZoomAt / panBy', () => {
+  it('zooms toward cursor and keeps that content point under cursor', () => {
+    const hostW = 1000;
+    const hostH = 500;
+    const containW = 800;
+    const containH = 400;
+    const hostX = 700;
+    const hostY = 250;
+    const next = sceneViewZoomAt(DEFAULT_SCENE_VIEW_CAMERA, {
+      hostW,
+      hostH,
+      containW,
+      containH,
+      hostX,
+      hostY,
+      factor: 2,
+    });
+    assert.ok(next.scale > 1.5);
+    const displayW = containW * next.scale;
+    const displayH = containH * next.scale;
+    const left = hostW / 2 - next.ox * displayW;
+    const top = hostH / 2 - next.oy * displayH;
+    const ix = (hostX - left) / displayW;
+    const iy = (hostY - top) / displayH;
+    // At scale=1 contain is centered; cursor was at content x=(700-100)/800=0.75
+    assert.ok(Math.abs(ix - 0.75) < 1e-6);
+    assert.ok(Math.abs(iy - 0.5) < 1e-6);
+  });
+
+  it('pans in host pixels', () => {
+    const cam = { scale: 2, ox: 0.5, oy: 0.5 };
+    const next = sceneViewPanBy(cam, { containW: 400, containH: 200, dx: 80, dy: 0 });
+    // displayW=800; dx=80 → ox decreases by 0.1
+    assert.ok(Math.abs(next.ox - 0.4) < 1e-6);
+    assert.equal(next.oy, 0.5);
+  });
+});

app/main/sceneView/sceneViewStore.ts

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+import {
+  clampSceneViewCamera,
+  DEFAULT_SCENE_VIEW_CAMERA,
+  type SceneViewCamera,
+  type SceneViewEvent,
+  type SceneViewState,
+} from '../../shared/types';
+
+function emptyState(): SceneViewState {
+  return {
+    revision: 1,
+    ...DEFAULT_SCENE_VIEW_CAMERA,
+  };
+}
+
+export class SceneViewStore {
+  private state: SceneViewState = emptyState();
+
+  getState(): SceneViewState {
+    return this.state;
+  }
+
+  reset(): SceneViewState {
+    if (
+      this.state.scale === 1 &&
+      this.state.ox === 0.5 &&
+      this.state.oy === 0.5
+    ) {
+      return this.state;
+    }
+    this.state = {
+      revision: this.state.revision + 1,
+      ...DEFAULT_SCENE_VIEW_CAMERA,
+    };
+    return this.state;
+  }
+
+  dispatch(event: SceneViewEvent): SceneViewState {
+    switch (event.kind) {
+      case 'reset':
+        return this.reset();
+      case 'set': {
+        const camera: SceneViewCamera = clampSceneViewCamera(event.camera);
+        if (
+          camera.scale === this.state.scale &&
+          camera.ox === this.state.ox &&
+          camera.oy === this.state.oy
+        ) {
+          return this.state;
+        }
+        this.state = {
+          revision: this.state.revision + 1,
+          ...camera,
+        };
+        return this.state;
+      }
+      default: {
+        const _exhaustive: never = event;
+        void _exhaustive;
+        return this.state;
+      }
+    }
+  }
+}