Tilemap cells are stored compactly in the project file: each layer keeps a tile list, an origin and one run-length encoded string per row; older projects with a cell map still load (#134)

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/store/serialize.ts

@@ -28,6 +28,7 @@ import type {
   TilemapLayer,
 } from '../model/Asset';
 import { parseCellKey } from '../model/tilemap';
+import { decodeCells, encodeCells, isStoredCells } from './tilemapCells';
 import { isAssetType } from '../model/AssetTypes';
 import { isFontFile } from '../model/font';
 import { isSoundFile } from '../model/sound';
@@ -218,9 +219,19 @@ export function deserializeProject(raw: unknown, fallbackId = ''): Project {
   return project;
 }
 
-/** Plain JSON-ready copy of the project (deep clone, stable key order for readable diffs). */
+/**
+ * Plain JSON-ready copy of the project (deep clone, stable key order for readable diffs). The cells
+ * of a tilemap are the one thing written differently from how they are held: see `tilemapCells.ts`.
+ */
 export function serializeProject(project: Project): unknown {
-  return JSON.parse(JSON.stringify(project));
+  const copy = JSON.parse(JSON.stringify(project)) as Project;
+  for (const asset of copy.assets)
+    if (asset.type === 'tilemap')
+      (asset as { layers: unknown[] }).layers = asset.layers.map(({ cells, ...layer }) => ({
+        ...layer,
+        ...encodeCells(cells),
+      }));
+  return copy;
 }
 
 function normalizeObjects(
@@ -513,8 +524,10 @@ function normalizeLayers(raw: unknown): TilemapLayer[] {
   for (const item of Array.isArray(raw) ? raw : []) {
     const l = asRecord(item);
     if (typeof l.id !== 'string' || !l.id || layers.some((o) => o.id === l.id)) continue;
+    // Projects saved before #134 hold the map itself; it is taken over as it is.
+    const stored = isStoredCells(l) ? decodeCells(l) : asRecord(l.cells);
     const cells: Record<string, string> = {};
-    for (const [key, value] of Object.entries(asRecord(l.cells)))
+    for (const [key, value] of Object.entries(stored))
       if (parseCellKey(key) && typeof value === 'string' && value !== '') cells[key] = value;
     const layer: TilemapLayer = { id: l.id, name: typeof l.name === 'string' ? l.name : 'Layer', cells };
     if (l.hidden === true) layer.hidden = true;