fix(editor): scope slab room paint to the clicked slab's level

packages/editor/src/lib/paint-scope.test.ts

@@ -81,8 +81,8 @@ describe('paintScopeLabel', () => {
 function item(id: string, assetId: string): ItemNode {
   return { id, type: 'item', asset: { id: assetId } } as unknown as ItemNode
 }
-function slab(id: string, polygon: Array<[number, number]>): SlabNode {
-  return { id, type: 'slab', polygon } as unknown as SlabNode
+function slab(id: string, polygon: Array<[number, number]>, levelId = 'l1'): SlabNode {
+  return { id, type: 'slab', polygon, parentId: levelId } as unknown as SlabNode
 }
 function wall(
   id: string,
@@ -451,4 +451,60 @@ describe('resolvePaintScopeTargets', () => {
     })
     expect(keys(result).sort()).toEqual(['inA:surface', 'inB:surface'])
   })
+
+  it('slab room stops at the level boundary', () => {
+    // Stacked storeys share a footprint, so the upper slab's centroid sits inside
+    // the ground floor's space polygon. Painting downstairs must not reach it.
+    const ground = slab(
+      'ground',
+      [
+        [1, 1],
+        [3, 1],
+        [3, 3],
+        [1, 3],
+      ],
+      'l1',
+    )
+    const upstairs = slab(
+      'upstairs',
+      [
+        [1, 1],
+        [3, 1],
+        [3, 3],
+        [1, 3],
+      ],
+      'l2',
+    )
+    const footprint: Array<[number, number]> = [
+      [0, 0],
+      [10, 0],
+      [10, 10],
+      [0, 10],
+    ]
+    const result = resolve({
+      node: ground,
+      role: 'surface',
+      scope: 'room',
+      nodes: [ground, upstairs],
+      spaces: [
+        {
+          id: 's1',
+          levelId: 'l1',
+          polygon: footprint,
+          wallIds: [],
+          boundaryFaces: [],
+          isExterior: false,
+        },
+        {
+          id: 's2',
+          levelId: 'l2',
+          polygon: footprint,
+          wallIds: [],
+          boundaryFaces: [],
+          isExterior: false,
+        },
+      ],
+    })
+    expect(keys(result)).toEqual(['ground:surface'])
+  })
 })

packages/editor/src/lib/paint-scope.ts

@@ -355,13 +355,19 @@ export function resolvePaintScopeTargets(args: {
   if (node.type === 'slab' && scope === 'room') {
     const centroid = polygonCentroid((node as SlabNode).polygon)
     if (!centroid) return single
-    const space = Object.values(spaces).find((candidate) =>
-      pointInPolygon2D(centroid, candidate.polygon),
+    // Space polygons are per-level footprints, and stacked storeys share a
+    // footprint — so the level has to gate both the space lookup and the fan-out
+    // or one click paints the floor above too.
+    const levelId = node.parentId ?? resolveLevelId(node, nodes)
+    if (!levelId) return single
+    const space = Object.values(spaces).find(
+      (candidate) => candidate.levelId === levelId && pointInPolygon2D(centroid, candidate.polygon),
     )
     if (!space) return single
     return Object.values(nodes)
       .filter((other) => {
         if (other.type !== 'slab') return false
+        if ((other.parentId ?? resolveLevelId(other, nodes)) !== levelId) return false
         const otherCentroid = polygonCentroid((other as SlabNode).polygon)
         return otherCentroid != null && pointInPolygon2D(otherCentroid, space.polygon)
       })